JP6350109B2 - Secondary battery electrolyte, secondary battery, battery pack, electric vehicle, power storage system, electric tool and electronic device - Google Patents

Description

  The present technology relates to an electrolytic solution used for a secondary battery, a secondary battery using the electrolytic solution, a battery pack using the secondary battery, an electric vehicle, an electric power storage system, an electric tool, and an electronic device.

  In recent years, various electronic devices such as mobile phones and personal digital assistants (PDAs) have become widespread, and further downsizing, weight reduction, and long life of the electronic devices are desired. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is small and lightweight and capable of obtaining a high energy density is in progress.

  In recent years, secondary batteries are not limited to the electronic devices described above, but are also being considered for other uses. For example, a battery pack detachably mounted on an electronic device, an electric vehicle such as an electric vehicle, an electric power storage system such as a household electric power server, and an electric tool such as an electric drill.

  Secondary batteries that use various charge / discharge principles have been proposed to obtain battery capacity. Among these, secondary batteries that use the storage and release of electrode reactants, and those that use precipitation and dissolution of electrode reactants. Secondary batteries are attracting attention. This is because these secondary batteries can provide a higher energy density than lead batteries and nickel cadmium batteries.

  The secondary battery includes an electrolytic solution together with a positive electrode and a negative electrode, and the electrolytic solution includes a nonaqueous solvent and an electrolyte salt. Since the composition of the electrolytic solution greatly affects the battery characteristics, various studies have been made on the composition of the electrolytic solution.

  Specifically, in order to improve cycle characteristics and the like, a fluorinated cyclic carbonate such as 4-fluoro-1,3-dioxolan-2-one is used as a non-aqueous solvent. In this case, an imide compound such as bis (trifluoromethanesulfonyl) imide lithium is used as the electrolyte salt (see, for example, Patent Documents 1 to 4).

JP 2008-123714 A JP 2010-129449 A JP2013-131394A JP 2013-225388 A

  Since electronic devices and the like are becoming more sophisticated and multifunctional, and the frequency of use of the electronic devices and the like is increasing, secondary batteries tend to be charged and discharged frequently. Therefore, there is still room for improvement regarding the battery characteristics of the secondary battery. In this case, in particular, considering the stable and continuous use of the secondary battery, it is important not only to improve battery characteristics but also to ensure safety.

  The present technology has been made in view of such problems, and its purpose is to provide an electrolyte for a secondary battery, a secondary battery, a battery pack, an electric vehicle, an electric power storage capable of achieving both battery characteristics and safety. It is to provide a system, a power tool, and an electronic device.

The electrolyte solution for a secondary battery according to the present technology includes a nonaqueous solvent and an electrolyte salt. The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate, and propylene carbonate , and the electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate . The content of 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is 95 wt% to 100 wt% der is, in the non-aqueous content of ethylene carbonate and the nonaqueous solvent in the solvent The sum of the content of propylene carbonate is 0 wt% to 5 wt%, and the content of bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent. The ratio of the amount of lithium hexafluorophosphate to the amount of lithium bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.

  The secondary battery of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution containing a nonaqueous solvent and an electrolyte salt, and the electrolyte solution has the same configuration as the electrolyte solution for the secondary battery of the present technology described above. It is. Each of the battery pack, the electric vehicle, the power storage system, the electric tool, and the electronic device of the present technology includes a secondary battery, and the secondary battery has the same configuration as the secondary battery of the present technology described above. .

According to the secondary battery electrolyte or secondary battery of the present technology, the non-aqueous solvent has the above-described configuration, and the electrolyte salt has the above-described configuration. Can be made compatible. Moreover, the same effect can be acquired also in the battery pack of this technique, an electric vehicle, an electric power storage system, an electric tool, or an electronic device.

  In addition, the effect described here is not necessarily limited, and may be any effect described in the present technology.

It is sectional drawing showing the structure of the secondary battery (cylindrical type) of one Embodiment of this technique. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. It is a perspective view showing the structure of the other secondary battery (laminate film type) of one Embodiment of this technique. It is sectional drawing along the IV-IV line of the wound electrode body shown in FIG. It is a perspective view showing the structure of the application example (battery pack: single cell) of a secondary battery. It is a block diagram showing the structure of the battery pack shown in FIG. It is a block diagram showing the structure of the application example (battery pack: assembled battery) of a secondary battery. It is a block diagram showing the structure of the application example (electric vehicle) of a secondary battery. It is a block diagram showing the structure of the application example (electric power storage system) of a secondary battery. It is a block diagram showing the structure of the application example (electric tool) of a secondary battery. It is sectional drawing showing the structure of the secondary battery (coin type) for a test.

Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings. The order of explanation is as follows.

1. 1. Electrolytic solution for secondary battery Secondary battery 2-1. Lithium ion secondary battery (cylindrical type)
2-2. Lithium ion secondary battery (laminate film type)
2-3. Lithium metal secondary battery Applications of secondary battery 3-1. Battery pack (single cell)
3-2. Battery pack (assembled battery)
3-3. Electric vehicle 3-4. Electric power storage system 3-5. Electric tool

<1. Electrolyte for secondary battery>
First, the secondary battery electrolyte solution of the present technology (hereinafter simply referred to as “electrolyte solution”) will be described.

  The electrolytic solution described here is used for, for example, a lithium secondary battery. However, the type of secondary battery in which the electrolytic solution is used is not limited to the lithium secondary battery.

[Composition of electrolyte]
This electrolytic solution is a so-called liquid electrolyte and contains a nonaqueous solvent and an electrolyte salt. In addition, the kind of nonaqueous solvent may be only one kind, and may be two or more kinds. Similarly, only one type of electrolyte salt may be used, or two or more types may be used.

  The non-aqueous solvent contains any one or more of the fluorinated cyclic compounds represented by the following formula (1). Moreover, electrolyte salt contains any 1 type in the fluorinated imide compound represented by following formula (2), or 2 or more types.

（Ｒ１〜Ｒ４のそれぞれは、水素基、フッ素基、アルキル基およびフッ素化アルキル基のうちのいずれかであり、そのＲ１〜Ｒ４のうちの少なくとも１つは、フッ素基およびフッ素化アルキル基のうちのいずれかである。）

(Each of R1 to R4 is any one of a hydrogen group, a fluorine group, an alkyl group and a fluorinated alkyl group, and at least one of R1 to R4 is a fluorine group or a fluorinated alkyl group. Either)

LiN (R5SO ₂ ) (R6SO ₂ ) (2)
(R5 and R6 are each a fluorine group or a fluorinated alkyl group.)

[Fluorinated cyclic compounds]
The fluorinated cyclic compound represented by the formula (1) is an ethylene carbonate type compound containing one or more fluorine (F) as a constituent element.

  Each type of R1 to R4 is not particularly limited as long as it is any one of a hydrogen group, a fluorine group, an alkyl group, and a fluorinated alkyl group. R1 to R4 may be the same group or different groups. Of course, some of R1 to R4 may be the same group.

  The kind of the alkyl group is not particularly limited as long as it is any one of monovalent groups composed of carbon (C) and hydrogen (H). This alkyl group may be linear or branched having one or more side chains.

Specific examples of the alkyl group include a methyl group (—CH ₃ ), an ethyl group (—C ₂ H ₅ ), a propyl group (—C ₃ H ₇ ), an n-butyl group (—C ₄ H ₈ ), and t-butyl. Group (—C (—CH ₃ ) ₂ —CH ₃ ) and the like. However, specific examples of the alkyl group may be other groups not exemplified here.

  The number of carbon atoms of the alkyl group is not particularly limited, but among them, it is preferable that the number of carbon atoms is not excessively large. This is because the compatibility of the fluorinated cyclic compound is ensured. Specifically, the carbon number of the alkyl group is preferably 1 to 10, and more preferably 1 to 5.

The kind of the fluorinated alkyl group is not particularly limited as long as it is any of the groups in which at least one hydrogen group of the alkyl groups is substituted with a fluorine group. Specific examples of the fluorinated alkyl group include a monofluoromethyl group (—CH ₂ F), a difluoromethyl group (—CHF ₂ ), a perfluoromethyl group (—CF ₃ ), and a perfluoroethyl group (—C ₂ F ₅ ). Perfluoropropyl group (—C ₃ F ₇ ), perfluoro-n-butyl group (—C ₄ F ₈ ) and perfluoro-t-butyl group (—C (—CF ₃ ) ₂ —CF ₃ ), etc. is there. However, specific examples of the fluorinated alkyl group may be other groups not exemplified here.

  Details regarding the carbon number of the fluorinated alkyl group are the same as, for example, the details regarding the carbon number of the alkyl group described above.

  However, any one or two or more of R1 to R4 are either a fluorine group or a fluorinated alkyl group. This is because the fluorinated cyclic compound must contain one or more fluorine atoms as constituent elements, as described above.

  In particular, each of R1 to R4 is either a hydrogen group or a fluorine group, and any one or two or more of R1 to R4 are preferably fluorine groups. This is because the fluorinated cyclic compound can be easily synthesized and the compatibility of the fluorinated cyclic compound is ensured.

  Further, the content of the fluorinated cyclic compound in the non-aqueous solvent needs to be sufficiently large in order to achieve both battery characteristics and safety in the secondary battery as will be described later. Specifically, the content of the fluorinated cyclic compound is 95% by weight to 100% by weight.

  That is, the non-aqueous solvent may be only the fluorinated cyclic compound, or may contain any one or more of other materials (other non-aqueous solvents described later) in addition to the fluorinated cyclic compound. Also good.

  However, since the non-aqueous solvent contains another material together with the fluorinated cyclic compound, when the content of the fluorinated cyclic compound is less than 100% by weight, the content of the other material is 5% by weight. It is suppressed to the following. Although the kind of this other material is not specifically limited, For example, it is any 1 type or 2 or more types in the other nonaqueous solvent mentioned later. Especially, it is preferable that the other material contains one or both of cyclic carbonate and chain carbonate. This is because the dissociation property of the electrolyte salt and the ion mobility are improved as described later.

  Specific examples of the fluorinated cyclic compound include compounds represented by the following formulas (1-1) to (1-16), and the compounds include geometric isomers. In this geometric isomer, the trans isomer is preferable to the cis isomer. This is because it can be easily synthesized. However, specific examples of the fluorinated cyclic compound may be other compounds not exemplified here.

  Of these, 4-fluoro-1,3-dioxolan-2-one and the like shown in Formula (1-1) are preferable. This is because it can be easily synthesized and has excellent compatibility.

[Fluorinated imide compound]
The fluorinated imide compound represented by the formula (2) is an imide lithium salt containing one or more fluorine atoms as constituent elements and two sulfonyl groups (> SO ₂ ).

  Each type of R5 and R6 is not particularly limited as long as it is either a fluorine group or a fluorinated alkyl group. R5 and R6 may be the same group or different groups.

  Details regarding the fluorinated alkyl group are the same as, for example, those described for the fluorinated cyclic compound.

  Especially, it is preferable that each of R5 and R6 is either a fluorine group or a perfluoroalkyl group. This is because the fluorinated imide compound can be easily synthesized, and the solubility and compatibility of the fluorinated imide compound are ensured.

Specific examples of the fluorinated imide compound include LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (C ₃ H ₇ SO ₂ ) ₂ , LiN (FSO). ₂ ) (CF ₃ SO ₂ ), LiN (FSO ₂ ) (C ₂ F ₅ SO ₂ ), LiN (FSO ₂ ) (C ₃ H ₇ SO ₂ ), LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ), LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ ) and LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ). However, specific examples of the fluorinated imide compound may be other compounds not exemplified here.

Among these, LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ are preferable. This is because it can be easily synthesized and has excellent solubility and the like.

  The electrolyte salt may be only a fluorinated imide compound, or may contain any one or more of other materials (other electrolyte salts described later) in addition to the fluorinated imide compound. .

  Although content of a fluorinated imide compound is not specifically limited, It is preferable that it is 0.6 mol / kg-2 mol / kg especially with respect to a non-aqueous solvent. This is because high ionic conductivity is obtained and a synergistic action of a fluorinated cyclic compound and a fluorinated imide compound described later is easily obtained.

[Reason for using fluorinated cyclic compound and fluorinated imide compound together]
Here, the reason why the non-aqueous solvent contains a predetermined amount (95 wt% to 100 wt%) of the fluorinated cyclic compound and the electrolyte salt contains the fluorinated imide compound is as follows.

  When a fluorinated imide compound is used as the electrolyte salt, battery characteristics such as initial charge / discharge characteristics can be improved. However, since the fluorinated imide compound has a property of easily corroding a metal material such as aluminum, safety is lowered. The metal material such as aluminum described here is, for example, a current collector and a lead used for a secondary battery as described later. Thus, the tendency for the safety to decrease due to the corrosion of the metal material becomes more prominent as the upper limit voltage during charging becomes higher, and more specifically, when the upper limit voltage becomes 3.6 V or more, it becomes more prominent. Become.

On the other hand, when a fluorinated cyclic compound is used as the non-aqueous solvent, a coating derived from the fluorinated cyclic compound is formed on the surface of the electrode during charge / discharge, and thus the electrode is protected by the coating. Thereby, since the decomposition reaction of the electrolytic solution is suppressed, battery characteristics such as initial charge / discharge characteristics are improved. However, since the fluorinated cyclic compound has the property of easily reacting with general electrolyte salts such as lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ), the reaction Due to this, gas is likely to be generated. As a result, the secondary battery tends to swell, and safety is reduced. Thus, the tendency for the safety to decrease due to the reaction between the non-aqueous solvent and the electrolyte salt becomes particularly prominent as the environmental temperature increases, and the content of the fluorinated cyclic compound in the non-aqueous solvent increases. The larger it becomes, the more noticeable it becomes.

  From these facts, when the fluorinated cyclic compound and the fluorinated imide compound are combined, the battery characteristics can be improved, but the safety is not improved, but rather the safety is expected to deteriorate.

  However, the fluorinated imide compound is used in a state where the content of the fluorinated cyclic compound in the non-aqueous solvent is sufficiently increased. In this case, contrary to the above prediction, not only the battery characteristics but also the safety is improved by the synergistic action of the fluorinated cyclic compound and the fluorinated imide compound. The state where the content of the fluorinated cyclic compound is sufficiently increased means the case where the content of the fluorinated cyclic compound is 95 wt% to 100 wt% as described above.

  Specifically, the decomposition reaction of the electrolytic solution is suppressed by the coating derived from the fluorinated cyclic compound. In this case, despite the use of the fluorinated cyclic compound, the reactivity of the non-aqueous solvent is specifically reduced, so that gas is hardly generated.

  Moreover, despite the use of the fluorinated imide compound, the corrosive ability of the fluorinated imide compound is specifically reduced, so that metal materials such as aluminum are hardly corroded. In this case, the reactivity of the fluorinated cyclic compound is also specifically reduced, so that gas is hardly generated.

  From these things, the decomposition reaction of electrolyte solution is suppressed by the synergistic action of a fluorinated cyclic compound and a fluorinated imide compound. In this case, the corrosion reaction of a metal material such as aluminum is suppressed, and the generation of gas is also suppressed. Therefore, not only the battery characteristics are improved, but also the safety is improved, so that both the battery characteristics and the safety are compatible.

  In particular, as described later, when the negative electrode material contains both a carbon material and a metal-based material, the above-described advantages can be effectively obtained as the content of the metal-based material in the negative electrode material increases. There is a tendency. This is because the metal-based material has a high theoretical capacity, but has a property of easily expanding and contracting at the time of charge / discharge, so that the respective effects of improving battery characteristics and safety are more easily exhibited.

[Other non-aqueous solvents]
In addition, in addition to the above-mentioned fluorinated cyclic compound, the non-aqueous solvent may contain any one type or two or more types of other materials (other non-aqueous solvents).

  The other non-aqueous solvent is, for example, any one or more of the compounds described below (excluding the fluorinated cyclic compound).

  Other nonaqueous solvents are, for example, cyclic carbonates, chain carbonates, lactones, chain carboxylates and nitriles. This is because excellent solubility and compatibility are obtained. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, and butylene carbonate, and examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate. Examples of the lactone include γ-butyrolactone and γ-valerolactone. Examples of the carboxylic acid ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, and ethyl trimethyl acetate. Examples of nitriles include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile.

  Other nonaqueous solvents include, for example, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate and dimethyl sulfoxide.

  Among these, one or both of a cyclic carbonate and a chain carbonate are preferable. More specifically, any one or two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable. In this case, a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, a relative dielectric constant ε ≧ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate (for example, viscosity ≦ 1 mPas). -A combination with s) is more preferred. This is because the dissociation property of the electrolyte salt and the ion mobility are improved in the electrolytic solution.

  In addition, the other non-aqueous solvent is one or more of unsaturated cyclic carbonates. This is because a stable protective film is formed on the surface of the electrode during charging / discharging, so that the decomposition reaction of the electrolytic solution is suppressed.

  This unsaturated cyclic carbonate is a cyclic carbonate containing one or more unsaturated bonds (carbon-carbon double bonds), and more specifically, the following formulas (3) to (5): These are compounds represented by each. Although content of unsaturated cyclic carbonate in a nonaqueous solvent is not specifically limited, For example, they are 0.01 weight%-10 weight%.

（Ｒ１１およびＲ１２のそれぞれは、水素基およびアルキル基のうちのいずれかである。Ｒ１３〜Ｒ１６のそれぞれは、水素基、アルキル基、ビニル基およびアリル基のうちのいずれかであり、そのＲ１３〜Ｒ１６のうちの少なくとも１つは、ビニル基およびアリル基のうちのいずれかである。Ｒ１７は、＞ＣＲ１８Ｒ１９で表される基であり、Ｒ１８およびＲ１９のそれぞれは、水素基およびアルキル基のうちのいずれかである。）

(Each of R11 and R12 is any one of a hydrogen group and an alkyl group. Each of R13 to R16 is any one of a hydrogen group, an alkyl group, a vinyl group, and an allyl group. At least one of R16 is any one of a vinyl group and an allyl group, R17 is a group represented by> CR18R19, and each of R18 and R19 is a hydrogen group or an alkyl group. Either.)

  The compound represented by the formula (3) is a vinylene carbonate-based compound. R11 and R12 may be the same group or different groups. Specific examples of vinylene carbonate compounds include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), and ethyl vinylene carbonate (4-ethyl). -1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1, Such as 3-dioxol-2-one and 4-trifluoromethyl-1,3-dioxol-2-one. Among these, vinylene carbonate is preferable. This is because it can be easily obtained and a high effect can be obtained.

  The compound represented by the formula (4) is a vinyl ethylene carbonate compound. R13 to R16 may be the same group or different groups. Of course, some of R13 to R16 may be the same group. Specific examples of the vinyl ethylene carbonate compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4- Ethyl-4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane- 2-one, 4,4-divinyl-1,3-dioxolan-2-one and 4,5-divinyl-1,3-dioxolan-2-one. Of these, vinyl ethylene carbonate is preferred. This is because it can be easily obtained and a high effect can be obtained. Of course, as R13 to R16, all may be vinyl groups, all may be allyl groups, or vinyl groups and allyl groups may be mixed.

  The compound represented by the formula (5) is a methylene ethylene carbonate compound. R18 and R19 may be the same group or different groups. Specific examples of methylene ethylene carbonate compounds include methylene ethylene carbonate (4-methylene-1,3-dioxolan-2-one), 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one and 4,4-diethyl-5-methylene-1,3-dioxolan-2-one and the like. This methylene ethylene carbonate compound may be a compound containing one methylene group as shown in the formula (5) or a compound containing two or more methylene groups.

  In addition, the unsaturated cyclic carbonate may be catechol carbonate (catechol carbonate) having a benzene ring. However, specific examples of the unsaturated cyclic ester carbonate may be other compounds not exemplified here.

  In addition, the other non-aqueous solvent is any one kind or two or more kinds of halogenated carbonates. This is because a stable protective film is formed on the surface of the electrode during charging / discharging, so that the decomposition reaction of the electrolytic solution is suppressed. This halogenated carbonate is a carbonate containing 1 or 2 or more halogens as a constituent element. More specifically, it is a compound represented by each of the following formulas (6) and (7). is there. Although content of halogenated carbonate in a non-aqueous solvent is not specifically limited, For example, they are 0.01 weight%-50 weight%.

（Ｒ２１〜Ｒ２４のそれぞれは、水素基、ハロゲン基、アルキル基およびハロゲン化アルキル基のうちのいずれかであり、そのＲ２１〜Ｒ２４のうちの少なくとも１つは、ハロゲン基およびハロゲン化アルキル基のうちのいずれかである。Ｒ２５〜Ｒ３０のそれぞれは、水素基、ハロゲン基、アルキル基およびハロゲン化アルキル基のうちのいずれかであり、そのＲ２５〜Ｒ３０のうちの少なくとも１つは、ハロゲン基およびハロゲン化アルキル基のうちのいずれかである。）

(Each of R21 to R24 is any one of a hydrogen group, a halogen group, an alkyl group and a halogenated alkyl group, and at least one of R21 to R24 is a halogen group or a halogenated alkyl group. Each of R25 to R30 is any one of a hydrogen group, a halogen group, an alkyl group, and a halogenated alkyl group, and at least one of R25 to R30 is a halogen group or a halogen atom. One of the alkyl groups.)

  The compound represented by formula (6) is a cyclic halogenated carbonate. However, the above-mentioned fluorinated cyclic compound is excluded from the cyclic halogenated carbonate described here. R21 to R24 may be the same group or different groups. Of course, some of R21 to R24 may be the same group.

  The type of the halogen group is not particularly limited, but among them, any one or two or more of a fluorine group, a chlorine group, a bromine group, and an iodine group are preferable, and a fluorine group is more preferable. This is because a fluorine group is easier to form the protective film than other halogen groups. The number of halogen groups is preferably two rather than one, and may be three or more. This is because the ability to form a protective film becomes higher and the protective film becomes stronger.

  The halogenated alkyl group is a group in which one or two or more hydrogen groups in an alkyl group are substituted (halogenated) with a halogen group. Details regarding the halogen group are as described above.

  Specific examples of the cyclic halogenated carbonate include compounds represented by the following formulas (6-1) to (6-5), and the compounds include geometric isomers. However, specific examples of the cyclic halogenated carbonate may be other compounds not exemplified here.

  The compound represented by the formula (7) is a chain halogenated carbonate. R25 to R30 may be the same group or different groups. Of course, a part of R25 to R30 may be the same group.

  Specific examples of the chain halogenated carbonate include fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate and difluoromethyl methyl carbonate. However, specific examples of the chain halogenated carbonate may be other compounds not exemplified here.

  Other non-aqueous solvents are also sulfonate esters. This is because the chemical stability of the electrolytic solution is further improved. Sulfonic acid esters include monosulfonic acid esters and disulfonic acid esters.

The monosulfonic acid ester may be a cyclic monosulfonic acid ester or a chain monosulfonic acid ester. Cyclic monosulfonates are, for example, sultone such as propane sultone and propene sultone. A chain monosulfonic acid ester is a compound in which a cyclic monosulfonic acid ester is cleaved on the way. For example, the chain monosulfonic acid ester when propane sultone is cleaved in the middle is CH ₃ —CH ₂ —CH ₂ —SO ₃ —CH ₃ or the like. The direction of this —SO ₃ — (— S (═O) ₂ —O—) is not particularly limited. That is, the above CH ₃ —CH ₂ —CH ₂ —SO ₃ —CH ₃ may be CH ₃ —CH ₂ —CH ₂ —S (═O) ₂ —O—CH ₃ , or CH ₃ —CH ₂ —. CH ₂ —O—S (═O) ₂ —CH ₃ may also be used.

The disulfonic acid ester may be a cyclic disulfonic acid ester or a chain disulfonic acid ester. The cyclic disulfonic acid ester is, for example, a compound represented by each of the following formula (8-1) to formula (8-3). A chain disulfonic acid ester is a compound in which a cyclic disulfonic acid ester is cleaved on the way. As an example, the chain disulfonic acid ester obtained by cleaving the compound represented by the formula (8-2) on the way is CH ₃ —SO ₃ —CH ₂ —SO ₃ —CH ₃ or the like. The directions of the two —SO ₃ — (— S (═O) ₂ —O—) are not particularly limited. That is, the above-mentioned CH ₃ —SO ₃ —CH ₂ —SO ₃ —CH ₃ may be CH ₃ —S (═O) ₂ —O—CH ₂ —S (═O) ₂ —O—CH ₃ , CH ₃ —O—S (═O) ₂ —CH ₂ —S (═O) ₂ —O—CH ₃ may be used, or CH ₃ —S (═O) ₂ —O—CH ₂ —O—S (= O) ₂ —CH ₃ may be used.

  Although content of the sulfonic acid ester in a non-aqueous solvent is not specifically limited, For example, they are 0.5 weight%-5 weight%. However, specific examples of the sulfonate ester may be other compounds not exemplified here.

  Another non-aqueous solvent is an acid anhydride. This is because the chemical stability of the electrolytic solution is further improved. Examples of the acid anhydride include a carboxylic acid anhydride, a disulfonic acid anhydride, and a carboxylic acid sulfonic acid anhydride. Examples of the carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the disulfonic anhydride include ethanedisulfonic anhydride and propanedisulfonic anhydride. Examples of the carboxylic acid sulfonic acid anhydride include anhydrous sulfobenzoic acid, anhydrous sulfopropionic acid, and anhydrous sulfobutyric acid. The content of the acid anhydride in the non-aqueous solvent is not particularly limited, but is, for example, 0.5% by weight to 5% by weight. However, specific examples of the acid anhydride may be other compounds not exemplified here.

Furthermore, other non-aqueous solvents are dicyano compounds and diisocyanate compounds. This is because the chemical stability of the electrolytic solution is further improved. Dicyano compounds, for _{example, NC-C m H 2m -CN} (m is an integer of 1 or more) is a compound represented by, more specifically, NC-C ₂ H ₄ -CN and the like. The diisocyanate compound is, for example, a compound represented by OCN—C _n H _2n —NCO (n is an integer of 1 or more), and more specifically OCN—C ₆ H ₁₂ —NCO. Although content of the dicyano compound in a solvent is not specifically limited, For example, they are 0.5 weight%-5 weight%. The range of this content is the same also about a diisocyanate compound, for example. However, specific examples of the dicyano compound and the diisocyanate compound may be other compounds not exemplified here.

[Other electrolyte salts]
In addition, in addition to the above-mentioned fluorinated imide compound, the electrolyte salt may contain any one kind or two or more kinds of other materials (other electrolyte salts).

  The other electrolyte salt is, for example, one or more of lithium salts. However, the fluorinated imide compounds described above are excluded from the other electrolyte salts described herein. The other electrolyte salt may contain a salt other than the lithium salt, for example. Examples of the salt other than the lithium salt include salts of light metals other than lithium.

Other lithium salts include, for example, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetraphenylborate _{(LiB (C 6 H 5)} 4), methanesulfonic acid lithium (LiCH ₃ SO _3), lithium trifluoromethanesulfonate (LiCF ₃ SO _3), tetrachloroaluminate lithium (LiAlCl _4), six Dilithium fluorosilicate (Li ₂ SiF ₆ ), lithium chloride (LiCl) and lithium bromide (LiBr).

  Among these, any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferable. This is because the internal resistance is lowered.

  In particular, the electrolytic solution may contain lithium hexafluorophosphate as another electrolyte salt in addition to the fluorinated imide compound. This is because the battery characteristics are further improved. The content of this lithium hexafluorophosphate is not particularly limited. However, if the content of lithium hexafluorophosphate is too large, the battery characteristics are improved, but the secondary battery may easily swell. For this reason, the content of lithium hexafluorophosphate is preferably 40 mol% or less, more preferably 10 mol% or less with respect to the substance amount (mol) of the fluorinated imide compound.

  In addition, the other electrolyte salt is one kind or two or more kinds of compounds represented by the following formulas (9) to (11). R41 and R43 may be the same group or different groups. This is the same for R51 to R53 as well as for R61 and R62.

（Ｘ４１は、長周期型周期表における１族元素または２族元素、またはＡｌである。Ｍ４１は、遷移金属、または長周期型周期表における１３族元素、１４族元素または１５族元素である。Ｒ４１は、ハロゲン基である。Ｙ４１は、−Ｃ（＝Ｏ）−Ｒ４２−Ｃ（＝Ｏ）−、−Ｃ（＝Ｏ）−ＣＲ４３₂ −、または−Ｃ（＝Ｏ）−Ｃ（＝Ｏ）−である。ただし、Ｒ４２は、アルキレン基、ハロゲン化アルキレン基、アリーレン基またはハロゲン化アリーレン基である。Ｒ４３は、アルキル基、ハロゲン化アルキル基、アリール基またはハロゲン化アリール基である。なお、ａ４は１〜４の整数であり、ｂ４は０、２または４の整数であり、ｃ４、ｄ４、ｍ４およびｎ４は１〜３の整数である。）

(X41 is a group 1 element or group 2 element in the long-period periodic table, or Al. M41 is a transition metal, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R41 is a halogen group, and Y41 is —C (═O) —R42—C (═O) —, —C (═O) —CR43 ₂ —, or —C (═O) —C (═O Where R42 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group, and R43 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group. A4 is an integer of 1 to 4, b4 is an integer of 0, 2 or 4, and c4, d4, m4 and n4 are integers of 1 to 3.)

（Ｘ５１は、長周期型周期表における１族元素または２族元素である。Ｍ５１は、遷移金属、または長周期型周期表における１３族元素、１４族元素または１５族元素である。Ｙ５１は、−Ｃ（＝Ｏ）−（ＣＲ５１₂ ）_b5−Ｃ（＝Ｏ）−、−Ｒ５３₂ Ｃ−（ＣＲ５２₂ ）_c5−Ｃ（＝Ｏ）−、−Ｒ５３₂ Ｃ−（ＣＲ５２₂ ）_c5−ＣＲ５３₂ −、−Ｒ５３₂ Ｃ−（ＣＲ５２₂ ）_c5−Ｓ（＝Ｏ）₂ −、−Ｓ（＝Ｏ）₂ −（ＣＲ５２₂ ）_d5−Ｓ（＝Ｏ）₂ −、または−Ｃ（＝Ｏ）−（ＣＲ５２₂ ）_d5−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ５１およびＲ５３のそれぞれは、水素基、アルキル基、ハロゲン基またはハロゲン化アルキル基であり、それぞれのうちの少なくとも１つは、ハロゲン基またはハロゲン化アルキル基である。Ｒ５２は、水素基、アルキル基、ハロゲン基またはハロゲン化アルキル基である。なお、ａ５、ｅ５およびｎ５は１または２の整数であり、ｂ５およびｄ５は１〜４の整数であり、ｃ５は０〜４の整数であり、ｆ５およびｍ５は１〜３の整数である。）

(X51 is a group 1 element or a group 2 element in the long-period periodic table. M51 is a transition metal, or a group 13, element or a group 15 element in the long-period periodic table. Y51 is -C (= O) - (CR51 2) b5 -C (= O) -, - R53 2 C- (CR52 2) c5 -C (= O) -, - R53 2 C- (CR52 2) c5 -CR53 ₂ −, —R53 ₂ C— (CR52 ₂ ) _c5 —S (═O) ₂ —, —S (═O) ₂ — (CR52 ₂ ) _d5 —S (═O) ₂ —, or —C (═O )-(CR52 ₂ ) _d5 -S (= O) _2- , wherein each of R51 and R53 is a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, and at least one of each Is a halogen group or a halogenated alkyl group, and R52 is a hydrogen group. An alkyl group, a halogen group or a halogenated alkyl group, wherein a5, e5 and n5 are integers of 1 or 2, b5 and d5 are integers of 1 to 4, and c5 is an integer of 0 to 4. , F5 and m5 are integers of 1 to 3.)

（Ｘ６１は、長周期型周期表における１族元素または２族元素である。Ｍ６１は、遷移金属、または長周期型周期表における１３族元素、１４族元素または１５族元素である。Ｒｆは、フッ素化アルキル基またはフッ素化アリール基であり、いずれの炭素数も１〜１０である。Ｙ６１は、−Ｃ（＝Ｏ）−（ＣＲ６１₂ ）_d6−Ｃ（＝Ｏ）−、−Ｒ６２₂ Ｃ−（ＣＲ６１₂ ）_d6−Ｃ（＝Ｏ）−、−Ｒ６２₂ Ｃ−（ＣＲ６１₂ ）_d6−ＣＲ６２₂ −、−Ｒ６２₂ Ｃ−（ＣＲ６１₂ ）_d6−Ｓ（＝Ｏ）₂ −、−Ｓ（＝Ｏ）₂ −（ＣＲ６１₂ ）_e6−Ｓ（＝Ｏ）₂ −、または−Ｃ（＝Ｏ）−（ＣＲ６１₂ ）_e6−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ６１は、水素基、アルキル基、ハロゲン基またはハロゲン化アルキル基である。Ｒ６２は、水素基、アルキル基、ハロゲン基またはハロゲン化アルキル基であり、そのうちの少なくとも１つは、ハロゲン基またはハロゲン化アルキル基である。なお、ａ６、ｆ６およびｎ６は１または２の整数であり、ｂ６、ｃ６およびｅ６は１〜４の整数であり、ｄ６は０〜４の整数であり、ｇ６およびｍ６は１〜３の整数である。）

(X61 is a group 1 element or a group 2 element in the long-period periodic table. M61 is a transition metal, or a group 13, element or a group 15 element in the long-period periodic table. Rf is A fluorinated alkyl group or a fluorinated aryl group, each having 1 to 10 carbon atoms, Y61 is —C (═O) — (CR61 ₂ ) _d6 —C (═O) —, —R62 ₂ C _{- (CR61 2) d6 -C (} = O) -, - R62 2 C- (CR61 2) d6 -CR62 2 -, - R62 2 C- (CR61 2) d6 -S (= O) 2 -, - S (═O) ₂ — (CR61 ₂ ) _e6 —S (═O) ₂ —, or —C (═O) — (CR61 ₂ ) _e6 —S (═O) ₂ —, wherein R61 is hydrogen A group, an alkyl group, a halogen group or a halogenated alkyl group, wherein R62 represents a hydrogen group, an alkyl group; , A halogen group or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a6, f6 and n6 are integers of 1 or 2, and b6, c6 and e6 are (It is an integer of 1-4, d6 is an integer of 0-4, and g6 and m6 are integers of 1-3.)

  The Group 1 elements are hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Group 2 elements are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Group 13 elements are boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Group 14 elements are carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). Group 15 elements are nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

  Specific examples of the compound represented by the formula (9) include compounds represented by the following formulas (9-1) to (9-6). Specific examples of the compound represented by the formula (10) include compounds represented by the following formulas (10-1) to (10-8). Specific examples of the compound represented by the formula (11) include a compound represented by the following formula (11-1). However, specific examples of the compounds shown in each of the formulas (9) to (11) may be other compounds not exemplified here.

  The electrolyte salt is a compound represented by each of the following formulas (12) and (13). Note that m and n may be the same value or different values. The same applies to p, q and r.

（Ｒ７１は炭素数＝２〜４の直鎖状または分岐状のパーフルオロアルキレン基である。）

(R71 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

LiC (C _p F _{2p + 1} SO ₂ ) (C _q F _{2q + 1} SO ₂ ) (C _r F _{2r + 1} SO ₂ ) (13)
(P, q and r are integers of 1 or more.)

  The compound shown in Formula (12) is a cyclic imide compound. Specific examples of the cyclic imide compound include compounds represented by the following formulas (12-1) to (12-4). However, specific examples of the cyclic imide compound may be other compounds not exemplified here.

The compound represented by the formula (13) is a chain methide compound. Specific examples of the chain methide compound include lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ). However, specific examples of the chain-like methide compound may be other compounds not exemplified here.

  Here, although total content of electrolyte salt is not specifically limited, It is preferable that it is 0.6 mol / kg-2.5 mol / kg especially with respect to a non-aqueous solvent. This is because high ionic conductivity is obtained.

  The total content of the electrolyte salt described here means the content of the fluorinated imide compound when the electrolyte salt contains only the fluorinated imide compound as described above. On the other hand, in the case where the electrolyte salt contains any one kind or two or more kinds of other electrolyte salts in addition to the fluorinated imide compound, the content of the fluorinated imide compound and other electrolyte salts Means the total content.

[Further other materials]
In addition to the non-aqueous solvent (including the fluorinated cyclic compound) and the electrolyte salt (including the fluorinated imide compound), the electrolyte solution may include any one or more of other materials. May be included.

Still another material is, for example, one or more of phosphorous fluorine-containing salts such as LiPF ₂ O ₂ and Li ₂ PFO ₃ . The content of the phosphorus fluorine-containing salt in the electrolytic solution is not particularly limited.

[Action and effect of electrolyte]
According to this electrolytic solution, the nonaqueous solvent contains a predetermined amount (95 wt% to 100 wt%) of the fluorinated cyclic compound, and the electrolyte salt contains the fluorinated imide compound. In this case, as described above, the synergistic action of the fluorinated cyclic compound and the fluorinated imide compound not only suppresses the decomposition reaction of the electrolytic solution, but also suppresses the corrosion reaction of metal materials such as aluminum. At the same time, the generation of gas is suppressed. Therefore, both battery characteristics and safety can be achieved.

<2. Secondary battery>
Next, a secondary battery using the above electrolytic solution will be described.

<2-1. Lithium-ion secondary battery (cylindrical type)>
FIG. 1 shows a cross-sectional configuration of the secondary battery. FIG. 2 is an enlarged partial cross-sectional configuration of the spirally wound electrode body 20 shown in FIG.

  The secondary battery described here is, for example, a lithium secondary battery (lithium ion secondary battery) in which the capacity of the negative electrode 22 is obtained by occlusion and release of lithium (Li) as an electrode reactant.

[overall structure]
The secondary battery has a so-called cylindrical battery structure. For example, as shown in FIG. 1, a pair of insulating plates 12 and 13 and a battery element are provided inside a hollow cylindrical battery can 11. The wound electrode body 20 is housed. The wound electrode body 20 is obtained by, for example, laminating a positive electrode 21 and a negative electrode 22 via a separator 23 and then winding the positive electrode 21, the negative electrode 22, and the separator 23. The wound electrode body 20 is impregnated with the electrolytic solution of the present technology described above.

  The battery can 11 has, for example, a hollow structure in which one end is closed and the other end is opened. For example, any of iron (Fe), aluminum (Al), and alloys thereof It is formed of one type or two or more types. Nickel or the like may be plated on the surface of the battery can 11. The pair of insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 and to extend perpendicularly to the wound peripheral surface.

  A battery lid 14, a safety valve mechanism 15, and a heat sensitive resistance element (PTC element) 16 are caulked through a gasket 17 at the open end of the battery can 11. Thereby, the battery can 11 is sealed. The battery lid 14 is formed of the same material as the battery can 11, for example. Each of the safety valve mechanism 15 and the thermal resistance element 16 is provided inside the battery lid 14, and the safety valve mechanism 15 is electrically connected to the battery lid 14 via the thermal resistance element 16. In the safety valve mechanism 15, the disk plate 15 </ b> A is reversed when the internal pressure becomes a certain level or more due to an internal short circuit or external heating. Thereby, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut. In order to prevent abnormal heat generation due to a large current, the resistance of the heat sensitive resistor 16 increases as the temperature rises. The gasket 17 is formed of, for example, an insulating material, and asphalt or the like may be applied to the surface of the gasket 17.

  For example, a center pin 24 is inserted into the winding center of the wound electrode body 20. However, the center pin 24 may not be inserted into the winding center of the wound electrode body 20. A positive electrode lead 25 is attached to the positive electrode 21, and a negative electrode lead 26 is attached to the negative electrode 22. The positive electrode lead 25 is formed of a conductive material such as aluminum, for example. For example, the positive electrode lead 25 is attached to the safety valve mechanism 15 and is electrically connected to the battery lid 14. The negative electrode lead 26 is formed of a conductive material such as nickel, for example. For example, the negative electrode lead 26 is attached to the battery can 11 and is electrically connected to the battery can 11.

[Positive electrode]
For example, as illustrated in FIG. 2, the positive electrode 21 includes a positive electrode current collector 21 </ b> A and a positive electrode active material layer 21 </ b> B provided on both surfaces of the positive electrode current collector 21 </ b> A. However, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.

  The positive electrode current collector 21A includes, for example, any one type or two or more types of conductive materials. Although the kind of conductive material is not specifically limited, For example, they are metal materials, such as aluminum (Al), nickel (Ni), and stainless steel. The positive electrode current collector 21A may be a single layer or a multilayer.

  The positive electrode active material layer 21 </ b> B includes any one or more of positive electrode materials capable of occluding and releasing lithium as a positive electrode active material. However, the positive electrode active material layer 21 </ b> B may include any one type or two or more types of other materials such as a positive electrode binder and a positive electrode conductive agent in addition to the positive electrode active material.

  The positive electrode material is preferably a lithium-containing compound, and more specifically, preferably one or both of a lithium-containing composite oxide and a lithium-containing phosphate compound. This is because a high energy density can be obtained.

  The lithium-containing composite oxide is an oxide containing lithium and one or more elements other than lithium (hereinafter referred to as “other elements”) as constituent elements, for example, crystals such as layered rock salt type and spinel type It has a structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure.

  The kind of other element is not particularly limited as long as it is any one kind or two or more kinds of arbitrary elements. Especially, it is preferable that another element is any 1 type or 2 types or more of the elements which belong to 2nd group-15th group in a long-period type periodic table. More specifically, it is more preferable that the other elements include one or more metal elements of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe). preferable. This is because a high voltage can be obtained.

  The lithium-containing composite oxide having a layered rock salt type crystal structure is, for example, a compound represented by each of the following formulas (21) to (23).

_{Li a Mn (1-bc)} Ni b M11 c O (2-d) F e ··· (21)
(M11 is cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc It is at least one of (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and a to e are 0.8. ≦ a ≦ 1.2, 0 <b <0.5, 0 ≦ c ≦ 0.5, (b + c) <1, −0.1 ≦ d ≦ 0.2 and 0 ≦ e ≦ 0.1 are satisfied. However, the composition of lithium varies depending on the charge / discharge state, and a is the value of the complete discharge state.

Li _a Ni _(1-b) M12 _b O _(2-c) F _d (22)
(M12 is cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper It is at least one of (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and a to d are 0.8. ≦ a ≦ 1.2, 0.005 ≦ b ≦ 0.5, −0.1 ≦ c ≦ 0.2 and 0 ≦ d ≦ 0.1, provided that the composition of lithium depends on the charge / discharge state Unlikely, a is the value of the fully discharged state.)

Li _a Co _(1-b) M13 _b O _(2-c) F _d (23)
(M13 is nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper It is at least one of (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and a to d are 0.8. ≦ a ≦ 1.2, 0 ≦ b <0.5, −0.1 ≦ c ≦ 0.2 and 0 ≦ d ≦ 0.1, provided that the composition of lithium varies depending on the charge / discharge state, a is the value of the fully discharged state.)

Specific examples of the lithium-containing composite oxide having a layered rock salt type crystal structure are LiNiO ₂ , LiCoO ₂ , LiCo _0.98 Al _0.01 Mg _0.01 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O _2. LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , Li _1.2 Mn _0.52 Co _0.175 Ni _0.1 O ₂ and Li _1.15 (Mn _0.65 Ni _0.22 Co _0.13 ) O ₂ .

  When the lithium-containing composite oxide having a layered rock salt type crystal structure contains nickel, cobalt, manganese and aluminum as constituent elements, the atomic ratio of nickel is preferably 50 atomic% or more. This is because a high energy density can be obtained.

  The lithium-containing composite oxide having a spinel crystal structure is, for example, a compound represented by the following formula (24).

Li _a Mn _(2-b) M14 _b O _c F _d (24)
(M14 is cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper It is at least one of (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and a to d are 0.9. ≦ a ≦ 1.1, 0 ≦ b ≦ 0.6, 3.7 ≦ c ≦ 4.1 and 0 ≦ d ≦ 0.1, provided that the composition of lithium differs depending on the charge / discharge state, and a Is the value of the fully discharged state.)

Specific examples of the lithium-containing composite oxide having a spinel crystal structure include LiMn ₂ O ₄ .

  The lithium-containing phosphate compound having an olivine type crystal structure is, for example, a compound represented by the following formula (25).

Li _a M15PO ₄ (25)
(M15 is cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), niobium It is at least one of (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W), and zirconium (Zr). 0.9 ≦ a ≦ 1.1, where the composition of lithium varies depending on the charge / discharge state, and a is the value of the complete discharge state.)

Specific examples of the lithium-containing phosphate compound having an olivine type crystal structure include LiFePO ₄ , LiMnPO ₄ , LiFe _0.5 Mn _0.5 PO _4, and LiFe _0.3 Mn _0.7 PO ₄ .

  The lithium-containing composite oxide may be a compound represented by the following formula (26).

(Li ₂ MnO ₃ ) _x (LiMnO ₂ ) _1-x (26)
(X satisfies 0 ≦ x ≦ 1, where the composition of lithium varies depending on the charge / discharge state, and x is the value of the complete discharge state.)

  In addition, the positive electrode material may be any one kind or two or more kinds of oxides, disulfides, chalcogenides, conductive polymers, and the like. Examples of the oxide include titanium oxide, vanadium oxide, and manganese dioxide. Examples of the disulfide include titanium disulfide and molybdenum sulfide. An example of the chalcogenide is niobium selenide. Examples of the conductive polymer include sulfur, polyaniline, and polythiophene. However, the positive electrode material may be a material other than the above.

  The positive electrode binder contains, for example, any one or more of synthetic rubber and polymer material. Examples of the synthetic rubber include styrene butadiene rubber, fluorine rubber, and ethylene propylene diene. Examples of the polymer material include polyvinylidene fluoride and polyimide.

  The positive electrode conductive agent contains, for example, any one or more of carbon materials. Examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

[Negative electrode]
For example, as illustrated in FIG. 2, the negative electrode 22 includes a negative electrode current collector 22A and negative electrode active material layers 22B provided on both surfaces of the negative electrode current collector 22A. However, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A.

  The anode current collector 22A includes, for example, any one type or two or more types of conductive materials. Although the kind of conductive material is not specifically limited, For example, they are metal materials, such as copper (Cu), aluminum (Al), nickel (Ni), and stainless steel. The anode current collector 22A may be a single layer or a multilayer.

  The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. In this case, the surface of the negative electrode current collector 22A only needs to be roughened at least in a region facing the negative electrode active material layer 22B. The roughening method is, for example, a method of forming fine particles using electrolytic treatment. In the electrolytic treatment, fine particles are formed on the surface of the negative electrode current collector 22A by an electrolysis method in an electrolytic bath, so that the surface of the negative electrode current collector 22A is provided with irregularities. A copper foil produced by an electrolytic method is generally called an electrolytic copper foil.

  The negative electrode active material layer 22B includes any one or more of negative electrode materials capable of occluding and releasing lithium as a negative electrode active material. However, the negative electrode active material layer 22B may include any one type or two or more types of other materials such as a negative electrode binder and a negative electrode conductive agent in addition to the negative electrode active material.

  In order to prevent unintentional deposition of lithium metal on the negative electrode 22 during charging, the chargeable capacity of the negative electrode material is preferably larger than the discharge capacity of the positive electrode 21. That is, the electrochemical equivalent of the negative electrode material capable of occluding and releasing lithium is preferably larger than the electrochemical equivalent of the positive electrode 21.

  The negative electrode material is, for example, any one or more of carbon materials. This is because the change in crystal structure at the time of occlusion and release of lithium is very small, so that a high energy density can be obtained stably. Moreover, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode active material layer 22B is improved.

  Examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite. However, the interplanar spacing of the (002) plane in non-graphitizable carbon is preferably 0.37 nm or more, and the interplanar spacing of the (002) plane in graphite is preferably 0.34 nm or less. More specifically, examples of the carbon material include pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon, and carbon blacks. The cokes include pitch coke, needle coke, petroleum coke and the like. The organic polymer compound fired body is obtained by firing (carbonizing) a polymer compound such as a phenol resin and a furan resin at an appropriate temperature. In addition, the carbon material may be low crystalline carbon heat-treated at a temperature of about 1000 ° C. or less, or may be amorphous carbon. The shape of the carbon material may be any of a fibrous shape, a spherical shape, a granular shape, and a scale shape.

  The negative electrode material is, for example, a material (metal-based material) containing any one or more of metal elements and metalloid elements as constituent elements. This is because a high energy density can be obtained.

  The metal-based material may be any of a simple substance, an alloy, and a compound, or two or more of them, or a material having at least one of those one or two or more phases. However, the alloy includes a material including one or more metal elements and one or more metalloid elements in addition to a material composed of two or more metal elements. Moreover, the alloy may contain any 1 type or 2 types or more of nonmetallic elements. The structure of this metal material is, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and two or more kinds of coexisting materials.

  The metal element and metalloid element described above are, for example, one or more of metal elements and metalloid elements capable of forming an alloy with lithium. Specifically, for example, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb) ), Bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd) and platinum (Pt).

  Among these, one or both of silicon and tin is preferable. This is because the ability to occlude and release lithium is excellent, so that a significantly high energy density can be obtained.

  The material containing one or both of silicon and tin as a constituent element may be any of a simple substance, an alloy and a compound of silicon, or any of a simple substance, an alloy and a compound of tin. It may be a kind or more, and may be a material having at least a part of one kind or two or more kinds of phases. The simple substance described here means a simple substance (which may contain a small amount of impurities) in a general sense, and does not necessarily mean 100% purity.

  The alloy of silicon is, for example, any one of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium and the like as a constituent element other than silicon or Includes two or more. The compound of silicon contains, for example, one or more of carbon and oxygen as constituent elements other than silicon. However, the compound of silicon may contain, for example, any one kind or two kinds or more of the series of elements described regarding the silicon alloy as a constituent element other than silicon.

Specific examples of silicon alloys and silicon compounds are SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi _2. MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), LiSiO, and the like. Note that _v in SiO _v may be 0.2 <v <1.4.

  The alloy of tin, for example, as a constituent element other than tin, any one of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium, or the like Includes two or more. The tin compound contains, for example, one or more of carbon and oxygen as constituent elements other than tin. However, the compound of tin may contain, for example, any one kind or two kinds or more of the series of elements described regarding the tin alloy as a constituent element other than tin.

Specific examples of the tin alloy and the tin compound include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, and Mg ₂ Sn.

  In particular, the material containing tin as a constituent element is preferably, for example, a material containing Sn (first constituent element) and the second and third constituent elements as constituent elements (Sn-containing material). The second constituent element is, for example, cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cesium (Ce), hafnium (Hf), Any one or more of tantalum, tungsten, bismuth, silicon and the like are included. The third constituent element includes, for example, any one or more of boron, carbon, aluminum, phosphorus (P), and the like. This is because when the Sn-containing material contains the second and third constituent elements, a high battery capacity and excellent cycle characteristics can be obtained.

  Especially, it is preferable that Sn containing material is a material (SnCoC containing material) which contains tin, cobalt, and carbon as a structural element. In this SnCoC-containing material, for example, the carbon content is 9.9 mass% to 29.7 mass%, and the content ratio of tin and cobalt (Co / (Sn + Co)) is 20 mass% to 70 mass%. . This is because a high energy density can be obtained.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase is preferably low crystalline or amorphous. Since this phase is a reaction phase capable of reacting with lithium, excellent characteristics can be obtained due to the presence of the reaction phase. The half-width (diffraction angle 2θ) of the diffraction peak obtained by X-ray diffraction of this reaction phase is 1 ° or more when CuKα ray is used as the specific X-ray and the insertion speed is 1 ° / min. Is preferred. This is because lithium is occluded and released more smoothly and the reactivity with the electrolytic solution is reduced. In addition, the SnCoC-containing material may include a phase containing a simple substance or a part of each constituent element in addition to the low crystalline or amorphous phase.

  Whether a diffraction peak obtained by X-ray diffraction corresponds to a reaction phase capable of reacting with lithium can be easily determined by comparing X-ray diffraction charts before and after electrochemical reaction with lithium. . For example, if the position of the diffraction peak changes before and after the electrochemical reaction with lithium, it corresponds to a reaction phase capable of reacting with lithium. In this case, for example, a diffraction peak of a low crystalline or amorphous reaction phase is observed between 2θ = 20 ° and 50 °. Such a reaction phase contains, for example, each of the above-described constituent elements, and is considered to be low crystallized or amorphous mainly due to the presence of carbon.

  In the SnCoC-containing material, it is preferable that at least a part of carbon that is a constituent element is bonded to a metal element or a metalloid element that is another constituent element. This is because aggregation or crystallization of tin or the like is suppressed. The bonding state of the elements can be confirmed using, for example, X-ray photoelectron spectroscopy (XPS). In a commercially available apparatus, for example, Al—Kα ray or Mg—Kα ray is used as the soft X-ray. When at least a part of carbon is bonded to a metal element, a metalloid element, or the like, the peak of the synthetic wave of carbon 1s orbital (C1s) appears in a region lower than 284.5 eV. It is assumed that the energy calibration is performed so that the peak of the 4f orbit (Au4f) of the gold atom is obtained at 84.0 eV. At this time, since surface-contaminated carbon is usually present on the surface of the substance, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, and the peak is used as an energy reference. In the XPS measurement, the waveform of the C1s peak is obtained in a form including the surface contamination carbon peak and the carbon peak in the SnCoC-containing material. For this reason, for example, both peaks are separated by analyzing using commercially available software. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  This SnCoC-containing material is not limited to a material (SnCoC) whose constituent elements are only tin, cobalt, and carbon. This SnCoC-containing material is, for example, any one of silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, and bismuth in addition to tin, cobalt, and carbon One kind or two or more kinds may be included as constituent elements.

  In addition to the SnCoC-containing material, a material containing tin, cobalt, iron and carbon as constituent elements (SnCoFeC-containing material) is also preferable. The composition of the SnCoFeC-containing material is arbitrary. For example, when the iron content is set to be small, the carbon content is 9.9 mass% to 29.7 mass%, and the iron content is 0.3 mass% to 5.9 mass%. The content ratio of tin and cobalt (Co / (Sn + Co)) is 30% by mass to 70% by mass. When the iron content is set to be large, the carbon content is 11.9% to 29.7% by mass, and the ratio of the content of tin, cobalt and iron ((Co + Fe) / (Sn + Co + Fe)) Is 26.4% by mass to 48.5% by mass, and the content ratio of cobalt and iron (Co / (Co + Fe)) is 9.9% by mass to 79.5% by mass. This is because a high energy density can be obtained in such a composition range. Note that the physical properties (half-value width, etc.) of the SnCoFeC-containing material are the same as the above-described physical properties of the SnCoC-containing material.

  In addition, the negative electrode material may be any one kind or two or more kinds of metal oxides and polymer compounds, for example. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Especially, it is preferable that the negative electrode material contains both a carbon material and a metal-type material for the following reasons.

  A metal-based material, particularly a material containing one or both of silicon and tin as a constituent element has an advantage of high theoretical capacity, but has a concern that it tends to violently expand and contract during charge / discharge. On the other hand, the carbon material has a concern that the theoretical capacity is low, but has an advantage that it is difficult to expand and contract during charging and discharging. Therefore, by using the carbon material and the metal-based material together, expansion / contraction during charging / discharging is suppressed while obtaining a high theoretical capacity (in other words, battery capacity).

  The respective contents of the carbon material and the metal material in the negative electrode material, in other words, the mixing ratio of the carbon material and the metal material are not particularly limited. Among these, the content of the metal material is preferably 50% by weight or less, more preferably 30% by weight or less, and further preferably 20% by weight or less. This is because the advantages of the carbon material and the metal material can be obtained in a balanced manner.

  The negative electrode active material layer 22B is formed by any one method or two or more methods among, for example, a coating method, a gas phase method, a liquid phase method, a thermal spray method, and a firing method (sintering method). The coating method is, for example, a method in which a particulate (powder) negative electrode active material is mixed with a negative electrode binder and the mixture is dispersed in an organic solvent and then applied to the negative electrode current collector 22A. Examples of the vapor phase method include a physical deposition method and a chemical deposition method. More specifically, for example, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal chemical vapor deposition, a chemical vapor deposition (CVD) method, and a plasma chemical vapor deposition method. Examples of the liquid phase method include an electrolytic plating method and an electroless plating method. The thermal spraying method is a method of spraying a molten or semi-molten negative electrode active material onto the negative electrode current collector 22A. The firing method is, for example, a method in which a mixture dispersed in an organic solvent or the like is applied to the negative electrode current collector 22A using a coating method and then heat-treated at a temperature higher than the melting point of the negative electrode binder or the like. Examples of the firing method include an atmosphere firing method, a reaction firing method, a hot press firing method, and the like.

  In this secondary battery, as described above, in order to prevent unintentional precipitation of lithium on the negative electrode 22 during charging, the electrochemical equivalent of the negative electrode material capable of occluding and releasing lithium is the electrical equivalent of the positive electrode. Greater than the chemical equivalent. Further, when the open circuit voltage (that is, the battery voltage) at the time of full charge is 4.25 V or more, compared with the case where it is 4.20 V, even when the same positive electrode active material is used, the amount of lithium released per unit mass Therefore, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. Thereby, a high energy density is obtained.

[Separator]
The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is, for example, a porous film of any one of synthetic resin and ceramic, and may be a laminated film using two or more kinds of porous films. The synthetic resin is, for example, one or more of polytetrafluoroethylene, polypropylene, and polyethylene.

  In particular, the separator 23 may include, for example, the above-described porous film (base material layer) and a polymer compound layer provided on one or both surfaces of the base material layer. This is because the adhesion of the separator 23 to each of the positive electrode 21 and the negative electrode 22 is improved, so that the distortion of the wound electrode body 20 is suppressed. As a result, the decomposition reaction of the electrolytic solution is suppressed, and the leakage of the electrolytic solution impregnated in the base material layer is also suppressed. Therefore, the resistance is not easily increased even if charging and discharging are repeated, and the battery swelling is also suppressed. Is done.

  The polymer compound layer includes, for example, a polymer material such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer material may be a material other than polyvinylidene fluoride. When forming this polymer compound layer, for example, after applying a solution in which a polymer material is dissolved in an organic solvent or the like to the substrate layer, the substrate layer is dried. In addition, after immersing a base material layer in a solution, the base material layer may be dried.

[Electrolyte]
As described above, the wound electrode body 20 is impregnated with the electrolytic solution of the present technology. That is, the electrolytic solution contains a nonaqueous solvent and an electrolyte salt. The non-aqueous solvent contains a fluorinated cyclic compound, and the electrolyte salt contains a fluorinated imide compound.

[Operation of secondary battery]
This secondary battery operates as follows, for example.

  At the time of charging, lithium ions are released from the positive electrode 21, and the lithium ions are occluded in the negative electrode 22 through the electrolytic solution. On the other hand, at the time of discharging, lithium ions are released from the negative electrode 22, and the lithium ions are occluded in the positive electrode 21 through the electrolytic solution.

[Method for producing secondary battery]
This secondary battery is manufactured by the following procedure, for example.

  When the positive electrode 21 is manufactured, first, a positive electrode active material and, if necessary, a positive electrode binder and a positive electrode conductive agent are mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture is dispersed in an organic solvent or the like to obtain a paste-like positive electrode mixture slurry. Subsequently, after applying the positive electrode mixture slurry to both surfaces of the positive electrode current collector 21A, the positive electrode mixture slurry is dried to form the positive electrode active material layer 21B. Subsequently, the positive electrode active material layer 21B is compression-molded using a roll press or the like while heating the positive electrode active material layer 21B as necessary. In this case, compression molding may be repeated a plurality of times.

  When the negative electrode 22 is manufactured, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A by the same procedure as that of the positive electrode 21 described above. Specifically, a negative electrode active material, a negative positive electrode binder, a negative electrode conductive agent, and the like are mixed to form a negative electrode mixture, and then the negative electrode mixture is dispersed in an organic solvent or the like to obtain a paste-like negative electrode mixture. A slurry is obtained. Subsequently, after applying the negative electrode mixture slurry to both surfaces of the negative electrode current collector 22A, the negative electrode mixture slurry is dried to form the negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B is compression molded using a roll press or the like.

  When preparing an electrolytic solution, an electrolyte salt containing a fluorinated imide compound is dissolved in a non-aqueous solvent containing a fluorinated cyclic compound. In this case, the content of the fluorinated cyclic compound in the non-aqueous solvent is 95% by weight to 100% by weight.

  When the secondary battery is assembled using the positive electrode 21 and the negative electrode 22, the positive electrode lead 25 is attached to the positive electrode current collector 21A using a welding method or the like, and the negative electrode lead is connected to the negative electrode current collector 22A using a welding method or the like. 26 is attached. Subsequently, after the positive electrode 21 and the negative electrode 22 are laminated via the separator 23, the positive electrode 21, the negative electrode 22, and the separator 23 are wound to form the wound electrode body 20. Subsequently, the center pin 24 is inserted into the center of the wound electrode body 20. Subsequently, the spirally wound electrode body 20 is accommodated in the battery can 11 while the spirally wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13. In this case, the tip of the positive electrode lead 25 is attached to the safety valve mechanism 15 using a welding method or the like, and the tip of the negative electrode lead 26 is attached to the battery can 11 using a welding method or the like. Subsequently, an electrolytic solution is injected into the battery can 11 and the separator 23 is impregnated with the electrolytic solution. Subsequently, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are caulked to the opening end portion of the battery can 11 through the gasket 17. Thereby, a cylindrical secondary battery is completed.

[Operation and effect of secondary battery]
According to this secondary battery, since the electrolytic solution of the present technology described above is used, not only the decomposition reaction of the electrolytic solution is suppressed, but also the corrosion reaction of a metal material such as aluminum is suppressed, and the gas Occurrence is also suppressed. Therefore, both battery characteristics and safety can be achieved.

<2-2. Lithium-ion secondary battery (laminate film type)>
FIG. 3 shows a perspective configuration of another secondary battery. FIG. 4 shows a cross-sectional configuration along line IV-IV of the spirally wound electrode body 30 shown in FIG. FIG. 3 shows a state where the wound electrode body 30 and the exterior member 40 are separated from each other. In the following, the components of the cylindrical secondary battery already described will be referred to as needed.

[Overall structure of secondary battery]
This secondary battery is a lithium ion secondary battery having a so-called laminate film type battery structure. For example, as shown in FIG. 3, a wound electrode as a battery element is provided inside a film-shaped exterior member 40. The body 30 is stored. The wound electrode body 30 is obtained by, for example, laminating a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and then winding the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte layer 36. is there. A positive electrode lead 31 is attached to the positive electrode 33, and a negative electrode lead 32 is attached to the negative electrode 34. The outermost peripheral part of the wound electrode body 30 is protected by a protective tape 37.

  Each of the positive electrode lead 31 and the negative electrode lead 32 is led out in the same direction from the inside of the exterior member 40 toward the outside, for example. The positive electrode lead 31 is formed of any one type or two or more types of conductive materials such as aluminum (Al). The negative electrode lead 32 is formed of any one type or two or more types of conductive materials such as copper (Cu), nickel (Ni), and stainless steel, for example. These conductive materials have, for example, a thin plate shape or a mesh shape.

  The exterior member 40 is, for example, a single film that can be folded in the direction of arrow R, and a recess for accommodating the wound electrode body 30 is provided in a part of the exterior member 40. The exterior member 40 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order. In the manufacturing process of the secondary battery, after the exterior member 40 is folded so that the fusion layers face each other with the wound electrode body 30 therebetween, the outer peripheral edges of the fusion layers are fused. However, the exterior member 40 may be one in which two laminated films are bonded together with an adhesive or the like. The fusion layer is, for example, any one kind or two or more kinds of films such as polyethylene and polypropylene. The metal layer is, for example, one or more of aluminum foils. The surface protective layer is, for example, any one film or two or more films selected from nylon and polyethylene terephthalate.

  Especially, it is preferable that the exterior member 40 is an aluminum laminate film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order. However, the exterior member 40 may be a laminate film having another laminated structure, a polymer film such as polypropylene, or a metal film.

  For example, an adhesion film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and between the exterior member 40 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is formed of a material having adhesion to both the positive electrode lead 31 and the negative electrode lead 32. The material having this adhesion is, for example, a polyolefin resin, and more specifically, any one or more of polyethylene, polypropylene, modified polyethylene, modified polypropylene, and the like.

[Positive electrode, negative electrode and separator]
For example, as shown in FIGS. 3 and 4, the positive electrode 33 includes a positive electrode current collector 33A and a positive electrode active material layer 33B, and the negative electrode 34 includes, for example, the negative electrode current collector 34A and the negative electrode active material layer. 34B is included. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, and the negative electrode active material layer 34B are, for example, the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode The configuration is the same as that of each of the active material layers 22B. The configuration of the separator 35 is the same as that of the separator 23, for example.

  The electrolyte layer 36 includes the above-described electrolytic solution of the present technology and a polymer compound. The electrolyte layer 36 is a so-called gel electrolyte, and an electrolytic solution is held by a polymer compound. This is because high ionic conductivity (for example, 1 mS / cm or more at room temperature) is obtained and leakage of the electrolytic solution is prevented. The electrolyte layer 36 may further include any one kind or two or more kinds of other materials such as additives.

  Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate, polyvinyl alcohol, polymethacryl It includes any one or more of methyl acid, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene and polycarbonate. In addition, the polymer compound may be a copolymer. This copolymer is, for example, a copolymer of vinylidene fluoride and hexafluoropyrene. Among these, as the homopolymer, polyvinylidene fluoride is preferable, and as the copolymer, a copolymer of vinylidene fluoride and hexafluoropyrene is preferable. This is because it is electrochemically stable.

  In the electrolyte layer 36 which is a gel electrolyte, the non-aqueous solvent contained in the electrolytic solution is a broad concept including not only a liquid material but also a material having ion conductivity capable of dissociating the electrolyte salt. . Therefore, when using a polymer compound having ion conductivity, the polymer compound is also included in the non-aqueous solvent.

  Instead of the gel electrolyte layer 36, the electrolytic solution may be used as it is. In this case, the wound electrode body 30 is impregnated with the electrolytic solution.

[Operation of secondary battery]
This secondary battery operates as follows, for example.

  At the time of charging, lithium ions are released from the positive electrode 33, and the lithium ions are occluded in the negative electrode 34 through the electrolyte layer 36. On the other hand, during discharge, lithium ions are released from the negative electrode 34 and the lithium ions are occluded in the positive electrode 33 through the electrolyte layer 36.

[Method for producing secondary battery]
The secondary battery provided with the gel electrolyte layer 36 is manufactured, for example, by the following three types of procedures.

  In the first procedure, each of the positive electrode 33 and the negative electrode 34 is manufactured by the same manufacturing procedure as that of each of the positive electrode 21 and the negative electrode 22. That is, when the positive electrode 33 is produced, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A, and when the negative electrode 34 is produced, the negative electrode active material layer is formed on both surfaces of the negative electrode current collector 34A. 34B is formed. Subsequently, an electrolytic solution, a polymer compound, an organic solvent, and the like are mixed to prepare a precursor solution. Subsequently, after applying a precursor solution to each of the positive electrode 33 and the negative electrode 34, the precursor solution is dried to form a gel electrolyte layer 36. Subsequently, the positive electrode lead 31 is attached to the positive electrode current collector 33A using a welding method or the like, and the negative electrode lead 32 is attached to the negative electrode current collector 34A using a welding method or the like. Subsequently, after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35, the positive electrode 33, the negative electrode 34, and the separator 35 are wound to form the wound electrode body 30. Subsequently, the protective tape 37 is attached to the outermost peripheral portion of the wound electrode body 30. Subsequently, after folding the exterior member 40 so as to sandwich the wound electrode body 30, the outer peripheral edge portions of the exterior member 40 are bonded to each other using a heat fusion method or the like, and the wound member 40 is wound inside the exterior member 40. The electrode body 30 is encapsulated. In this case, the adhesion film 41 is inserted between the positive electrode lead 31 and the exterior member 40, and the adhesion film 41 is inserted between the negative electrode lead 32 and the exterior member 40.

  In the second procedure, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound to produce a wound body that is a precursor of the wound electrode body 30, and then the outermost peripheral portion of the wound body. A protective tape 37 is affixed to the surface. Subsequently, after folding the exterior member 40 so as to sandwich the spirally wound electrode body 30, the remaining outer peripheral edge portion excluding the outer peripheral edge portion of one side of the exterior member 40 is bonded using a heat fusion method or the like. Thus, the wound body is housed inside the bag-shaped exterior member 40. Subsequently, an electrolyte solution is prepared by mixing the electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary. Subsequently, after the electrolyte composition is injected into the bag-shaped exterior member 40, the exterior member 40 is sealed using a heat fusion method or the like. Subsequently, the monomer is thermally polymerized to form a polymer compound. Thereby, since the electrolytic solution is held by the polymer compound, the gel electrolyte layer 36 is formed.

  In the third procedure, except for using the separator 35 in which the polymer compound layer is formed on one side or both sides, a wound body is prepared and placed inside the bag-shaped exterior member 40 in the same manner as the second procedure described above. Store. This polymer compound layer contains, for example, any one or more of polymers (homopolymers, copolymers, or multi-component copolymers) containing vinylidene fluoride as a component. It is formed by the law etc. Specifically, the polymer compound layer includes, for example, polyvinylidene fluoride, a binary copolymer of vinylidene fluoride and hexafluoropropylene, and a ternary of vinylidene fluoride, hexafluoropropylene, and chlorotrifluoroethylene. System copolymer and the like. The polymer compound layer may contain one or more other polymer compounds together with a polymer containing vinylidene fluoride as a component. Subsequently, after injecting the electrolyte into the exterior member 40, the opening of the exterior member 40 is sealed using a thermal fusion method or the like. Subsequently, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with each of the positive electrode 33 and the negative electrode 34 through the polymer compound layer. Thereby, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled, so that the electrolyte layer 36 is formed.

  In the third procedure, the swelling of the secondary battery is suppressed more than in the first procedure. Further, in the third procedure, compared with the second procedure, the non-aqueous solvent, the monomer (raw material of the polymer compound) and the like hardly remain in the electrolyte layer 36, and therefore the formation process of the polymer compound is well controlled. The For this reason, each of the positive electrode 33, the negative electrode 34, and the separator 35 and the electrolyte layer 36 are sufficiently adhered.

[Operation and effect of secondary battery]
According to this secondary battery, since the above-described electrolyte solution of the present technology is used, both battery characteristics and safety can be achieved for the same reason as the cylindrical secondary battery.

<2-3. Lithium metal secondary battery>
The secondary battery described here is a cylindrical secondary battery (lithium metal secondary battery) in which the capacity of the negative electrode 22 is expressed by precipitation and dissolution of lithium metal. This secondary battery has the same configuration as the above-described lithium ion secondary battery (cylindrical type) except that the negative electrode active material layer 22B is formed of lithium metal, and is manufactured by the same procedure. Is done.

  In this secondary battery, since lithium metal is used as the negative electrode active material, a high energy density can be obtained. The negative electrode active material layer 22B may already exist from the time of assembly, but does not exist at the time of assembly, and may be formed of lithium metal deposited during charging. Further, the anode current collector 22A may be omitted by using the anode active material layer 22B as a current collector.

  This secondary battery operates as follows, for example. At the time of charging, when lithium ions are released from the positive electrode 21, the lithium ions are deposited as lithium metal on the surface of the negative electrode current collector 22A through the electrolytic solution. At the time of discharge, when lithium metal is eluted from the negative electrode active material layer 22B as lithium ions into the electrolytic solution, the lithium ions are occluded in the positive electrode 21 through the electrolytic solution.

  According to this cylindrical lithium metal secondary battery, since the electrolytic solution of the present technology described above is used, both battery characteristics and safety can be achieved for the same reason as the above-described lithium ion secondary battery. it can.

  Note that the configuration of the lithium metal secondary battery described here is not limited to the cylindrical secondary battery, and may be applied to a laminate film type secondary battery. In this case, the same effect can be obtained.

<3. Applications of secondary batteries>
Next, application examples of the above-described secondary battery will be described.

  The secondary battery can be used for machines, devices, instruments, devices, and systems (a collection of multiple devices) that can use the secondary battery as a power source for driving or a power storage source for storing power. There is no particular limitation. The secondary battery used as a power source may be a main power source (a power source used preferentially) or an auxiliary power source (a power source used in place of the main power source or switched from the main power source). When the secondary battery is used as an auxiliary power source, the type of the main power source is not limited to the secondary battery.

  Applications of the secondary battery are as follows, for example. Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, notebook computers, cordless phones, headphone stereos, portable radios, portable televisions, and portable information terminals. It is a portable living device such as an electric shaver. Storage devices such as backup power supplies and memory cards. Electric tools such as electric drills and electric saws. It is a battery pack used for a notebook computer or the like as a detachable power source. Medical electronic devices such as pacemakers and hearing aids. An electric vehicle such as an electric vehicle (including a hybrid vehicle). It is an electric power storage system such as a home battery system that stores electric power in case of an emergency. Of course, the secondary battery may be used for other purposes not illustrated here.

  Especially, it is effective that a secondary battery is applied to a battery pack, an electric vehicle, an electric power storage system, an electric tool, an electronic device, and the like. This is because, since excellent battery characteristics are required, the performance can be effectively improved by using the secondary battery of the present technology. The battery pack is a power source using a secondary battery, and is a so-called assembled battery. The electric vehicle is a vehicle that operates (runs) using a secondary battery as a driving power source, and may be an automobile (such as a hybrid automobile) that is provided with a drive source other than the secondary battery as described above. The power storage system is a system using a secondary battery as a power storage source. For example, in a household power storage system, power is stored in a secondary battery, which is a power storage source, so that it is possible to use household electrical products using the power. An electric power tool is a tool in which a movable part (for example, a drill etc.) moves, using a secondary battery as a driving power source. An electronic device is a device that exhibits various functions using a secondary battery as a driving power source (power supply source).

  Here, some application examples of the secondary battery will be specifically described. In addition, since the structure of each application example demonstrated below is an example to the last, those structures can be changed suitably.

<3-1. Battery pack (single cell)>
FIG. 5 shows a perspective configuration of a battery pack using single cells. FIG. 6 shows a block configuration of the battery pack shown in FIG. FIG. 5 shows a state where the battery pack is disassembled.

  The battery pack described here is a simple battery pack (so-called soft pack) using one secondary battery, and is mounted, for example, on an electronic device typified by a smartphone. For example, as shown in FIG. 5, the battery pack includes a power supply 111 that is a laminate film type secondary battery, and a circuit board 116 connected to the power supply 111. A positive electrode lead 112 and a negative electrode lead 113 are attached to the power source 111.

  A pair of adhesive tapes 118 and 119 are attached to both side surfaces of the power source 111. A protection circuit (PCM: Protection, Circuit, Module) is formed on the circuit board 116. The circuit board 116 is connected to the positive electrode 112 through the tab 114 and is connected to the negative electrode lead 113 through the tab 115. The circuit board 116 is connected to a lead wire 117 with a connector for external connection. In the state where the circuit board 116 is connected to the power supply 111, the circuit board 116 is protected from above and below by the label 120 and the insulating sheet 121. By attaching the label 120, the circuit board 116, the insulating sheet 121, and the like are fixed.

  Further, the battery pack includes a power source 111 and a circuit board 116 as shown in FIG. 6, for example. The circuit board 116 includes, for example, a control unit 121, a switch unit 122, a PTC 123, and a temperature detection unit 124. Since the power source 111 can be connected to the outside via the positive electrode terminal 125 and the negative electrode terminal 127, the power source 111 is charged / discharged via the positive electrode terminal 125 and the negative electrode terminal 127. The temperature detector 124 can detect the temperature using a temperature detection terminal (so-called T terminal) 126.

  The control unit 121 controls the operation of the entire battery pack (including the usage state of the power supply 111), and includes, for example, a central processing unit (CPU) and a memory.

  For example, when the battery voltage reaches the overcharge detection voltage, the control unit 121 disconnects the switch unit 122 so that the charging current does not flow through the current path of the power supply 111. For example, when a large current flows during charging, the control unit 121 disconnects the charging current by cutting the switch unit 122.

  In addition, for example, when the battery voltage reaches the overdischarge detection voltage, the control unit 121 disconnects the switch unit 122 so that the discharge current does not flow in the current path of the power supply 111. For example, when a large current flows during discharging, the control unit 121 cuts off the switch unit 122 and cuts off the discharging current.

  The overcharge detection voltage of the secondary battery is, for example, 4.20V ± 0.05V, and the overdischarge detection voltage is, for example, 2.4V ± 0.1V.

  The switch unit 122 switches the usage state of the power source 111 (whether the power source 111 can be connected to an external device) in accordance with an instruction from the control unit 121. The switch unit 122 includes, for example, a charge control switch and a discharge control switch. Each of the charge control switch and the discharge control switch is, for example, a semiconductor switch such as a field effect transistor (MOSFET) using a metal oxide semiconductor. The charge / discharge current is detected based on, for example, the ON resistance of the switch unit 122.

  The temperature detection unit 124 measures the temperature of the power supply 111 and outputs the measurement result to the control unit 121, and includes a temperature detection element such as a thermistor, for example. The measurement result by the temperature detection unit 124 is used for the control unit 121 to perform charge / discharge control during abnormal heat generation, and is used for the control unit 121 to perform correction processing when calculating the remaining capacity.

  The circuit board 116 may not include the PTC 123. In this case, a PTC element may be attached to the circuit board 116 separately.

<3-2. Battery Pack (Battery)>
FIG. 7 shows a block configuration of a battery pack using an assembled battery. This battery pack includes, for example, a control unit 61, a power source 62, a switch unit 63, a current measurement unit 64, a temperature detection unit 65, a voltage detection unit 66, and a switch control unit 67 inside the housing 60. A memory 68, a temperature detection element 69, a current detection resistor 70, and a positive terminal 71 and a negative terminal 72. The housing 60 is made of, for example, a plastic material.

  The control unit 61 controls the operation of the entire battery pack (including the usage state of the power supply 62), and includes, for example, a CPU. The power source 62 includes one or more secondary batteries (not shown). The power source 62 is, for example, an assembled battery including two or more secondary batteries, and the connection form of these secondary batteries may be in series, in parallel, or a mixture of both. For example, the power source 62 includes six secondary batteries connected in two parallel three series.

  The switch unit 63 switches the usage state of the power source 62 (whether or not the power source 62 can be connected to an external device) in accordance with an instruction from the control unit 61. The switch unit 63 includes, for example, a charge control switch, a discharge control switch, a charging diode, a discharging diode (all not shown), and the like. Each of the charge control switch and the discharge control switch is, for example, a semiconductor switch such as a field effect transistor (MOSFET) using a metal oxide semiconductor.

  The current measuring unit 64 measures the current using the current detection resistor 70 and outputs the measurement result to the control unit 61. The temperature detection unit 65 measures the temperature using the temperature detection element 69 and outputs the measurement result to the control unit 61. This temperature measurement result is used, for example, for the controller 61 to perform charge / discharge control during abnormal heat generation, and for the controller 61 to perform correction processing when calculating the remaining capacity. The voltage detector 66 measures the voltage of the secondary battery in the power source 62, converts the measured voltage from analog to digital, and supplies the converted voltage to the controller 61.

  The switch control unit 67 controls the operation of the switch unit 63 according to the signals input from the current measurement unit 64 and the voltage detection unit 66.

  For example, when the battery voltage reaches the overcharge detection voltage, the switch control unit 67 disconnects the switch unit 63 (charge control switch) so that the charging current does not flow through the current path of the power source 62. As a result, the power source 62 can only discharge through the discharging diode. Note that the switch control unit 67 cuts off the charging current when a large current flows during charging, for example.

  Further, the switch control unit 67 disconnects the switch unit 63 (discharge control switch) so that the discharge current does not flow in the current path of the power source 62 when the battery voltage reaches the overdischarge detection voltage, for example. . As a result, the power source 62 can only be charged via the charging diode. The switch control unit 67 cuts off the discharge current when a large current flows during discharge, for example.

  In the secondary battery, for example, the overcharge detection voltage is 4.20 V ± 0.05 V, and the overdischarge detection voltage is 2.4 V ± 0.1 V.

  The memory 68 is, for example, an EEPROM that is a nonvolatile memory. The memory 68 stores, for example, numerical values calculated by the control unit 61, secondary battery information (for example, internal resistance in an initial state) measured in the manufacturing process stage, and the like. If the full charge capacity of the secondary battery is stored in the memory 68, the control unit 61 can grasp information such as the remaining capacity.

  The temperature detection element 69 measures the temperature of the power source 62 and outputs the measurement result to the control unit 61, and is, for example, a thermistor.

  The positive electrode terminal 71 and the negative electrode terminal 72 are connected to an external device (for example, a notebook personal computer) operated using a battery pack, an external device (for example, a charger) used to charge the battery pack, or the like. Is done. Charging / discharging of the power source 62 is performed via the positive terminal 71 and the negative terminal 72.

<3-3. Electric vehicle>
FIG. 8 shows a block configuration of a hybrid vehicle which is an example of an electric vehicle. This electric vehicle includes, for example, a control unit 74, an engine 75, a power source 76, a driving motor 77, a differential device 78, a generator 79, and a transmission 80 inside a metal casing 73. And a clutch 81, inverters 82 and 83, and various sensors 84. In addition, the electric vehicle includes, for example, a front wheel drive shaft 85 and a front wheel 86 connected to the differential device 78 and the transmission 80, and a rear wheel drive shaft 87 and a rear wheel 88.

  This electric vehicle can run, for example, using either the engine 75 or the motor 77 as a drive source. The engine 75 is a main power source, such as a gasoline engine. When the engine 75 is used as a power source, the driving force (rotational force) of the engine 75 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78, a transmission 80, and a clutch 81 which are driving units. . The rotational force of the engine 75 is also transmitted to the generator 79, and the generator 79 generates AC power using the rotational force. The AC power is converted into DC power via the inverter 83, and the power source 76. On the other hand, when the motor 77 which is the conversion unit is used as a power source, the power (DC power) supplied from the power source 76 is converted into AC power via the inverter 82, and the motor 77 is driven using the AC power. . The driving force (rotational force) converted from electric power by the motor 77 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78, a transmission 80, and a clutch 81, which are driving units.

  When the electric vehicle decelerates via a braking mechanism (not shown), the resistance force at the time of deceleration is transmitted as a rotational force to the motor 77, and the motor 77 generates AC power using the rotational force. Good. This AC power is preferably converted into DC power via the inverter 82, and the DC regenerative power is preferably stored in the power source 76.

  The control unit 74 controls the operation of the entire electric vehicle and includes, for example, a CPU. The power source 76 includes one or more secondary batteries (not shown). The power source 76 may be connected to an external power source and be able to store power by receiving power supply from the external power source. The various sensors 84 are used, for example, to control the rotational speed of the engine 75 and to control the opening (throttle opening) of a throttle valve (not shown). The various sensors 84 include, for example, a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

  Although the case where the electric vehicle is a hybrid vehicle has been described, the electric vehicle may be a vehicle (electric vehicle) that operates using only the power source 76 and the motor 77 without using the engine 75.

<3-4. Power storage system>
FIG. 9 shows a block configuration of the power storage system. This power storage system includes, for example, a control unit 90, a power source 91, a smart meter 92, and a power hub 93 in a house 89 such as a general house and a commercial building.

  Here, the power source 91 is connected to, for example, an electric device 94 installed in the house 89 and can be connected to an electric vehicle 96 stopped outside the house 89. The power source 91 is connected to, for example, a private generator 95 installed in a house 89 via a power hub 93 and can be connected to an external centralized power system 97 via a smart meter 92 and the power hub 93. is there.

  The electrical device 94 includes, for example, one or more home appliances, and the home appliances are, for example, a refrigerator, an air conditioner, a television, and a water heater. The private generator 95 is, for example, any one type or two types or more of a solar power generator and a wind power generator. The electric vehicle 96 is, for example, any one type or two or more types of electric vehicles, electric motorcycles, hybrid vehicles, and the like. The centralized power system 97 is, for example, any one type or two or more types among a thermal power plant, a nuclear power plant, a hydroelectric power plant, and a wind power plant.

  The control unit 90 controls the operation of the entire power storage system (including the usage state of the power supply 91), and includes, for example, a CPU. The power source 91 includes one or more secondary batteries (not shown). The smart meter 92 is, for example, a network-compatible power meter installed in a house 89 on the power demand side, and can communicate with the power supply side. Accordingly, for example, the smart meter 92 enables efficient and stable energy supply by controlling the balance between supply and demand in the house 89 while communicating with the outside.

  In this power storage system, for example, power is accumulated in the power source 91 from the centralized power system 97 that is an external power source via the smart meter 92 and the power hub 93, and from the private power generator 95 that is an independent power source via the power hub 93. Thus, electric power is accumulated in the power source 91. Since the electric power stored in the power supply 91 is supplied to the electric device 94 and the electric vehicle 96 in accordance with an instruction from the control unit 91, the electric device 94 can be operated and the electric vehicle 96 can be charged. . In other words, the power storage system is a system that makes it possible to store and supply power in the house 89 using the power source 91.

  The power stored in the power supply 91 can be used arbitrarily. For this reason, for example, power is stored in the power source 91 from the centralized power system 97 at midnight when the electricity usage fee is low, and the power stored in the power source 91 is used during the day when the electricity usage fee is high. it can.

  The power storage system described above may be installed for each house (one household), or may be installed for each of a plurality of houses (multiple households).

<3-5. Electric tool>
FIG. 10 shows a block configuration of the electric power tool. This electric tool is, for example, an electric drill, and includes a control unit 99 and a power supply 100 inside a tool main body 98 formed of a plastic material or the like. For example, a drill portion 101 which is a movable portion is attached to the tool body 98 so as to be operable (rotatable).

  The control unit 99 controls the operation of the entire power tool (including the usage state of the power supply 100), and includes, for example, a CPU. The power supply 100 includes one or more secondary batteries (not shown). The control unit 99 supplies power from the power supply 100 to the drill unit 101 in response to an operation switch (not shown).

  Specific examples of the present technology will be described in detail.

(Experimental Examples 1-1 to 1-14)
As will be described below, secondary batteries were fabricated and battery characteristics and safety were examined. The order of explanation is as follows.

1. 1. Production of coin-type secondary battery 2. Production of a laminate film type secondary battery Battery characteristics and safety assessment

<1. Production of coin-type secondary battery>
The coin type secondary battery (lithium ion secondary battery) shown in FIG. 11 was produced as a test secondary battery by the following procedure.

  In this secondary battery, a test electrode 51 and a counter electrode 53 are laminated via a separator 55, and an outer can 52 in which the test electrode 51 is accommodated and an outer cup 54 in which the counter electrode 53 is accommodated form a gasket 56. It is squeezed through.

When preparing the test electrode 51, first, 96 parts by mass of an active material (LiCoO ₂ ), 3 parts by mass of a binder (polyvinylidene fluoride), and 1 part by mass of a conductive agent (carbon black) are mixed. The mixture was used. Subsequently, the mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone) to obtain a paste slurry. Subsequently, the mixture slurry was applied to both surfaces of the current collector (20 μm-thick striped aluminum foil) using a coating apparatus, and then the mixture slurry was dried to form an active material layer. Finally, the active material layer was compression molded using a roll press.

  When producing the counter electrode 53, first, 90 parts by mass of an active material (a mixture of graphite and silicon) and 10 parts by mass of a binder (polyvinylidene fluoride) were mixed to obtain a mixture. In this case, the mixing ratio of the active materials was graphite: silicon = 80: 10 by mass ratio. Subsequently, the mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone) to obtain a paste slurry. Subsequently, the mixture slurry was applied to both surfaces of the current collector (15 μm thick strip-like electrolytic copper foil) using a coating apparatus, and then the mixture slurry was dried to form an active material layer. Finally, the active material layer was compression molded using a roll press.

When preparing the electrolytic solution, the electrolyte salt was dissolved in a non-aqueous solvent. The respective compositions of the nonaqueous solvent and the electrolyte salt are as shown in Table 1. As the non-aqueous solvent, 4-fluoro-1,3-dioxolan-2-one (FEC) that is a fluorinated cyclic compound and ethylene carbonate (EC) and propylene carbonate (PC) that are other non-aqueous solvents are used. Using. Examples of the electrolyte salt include bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ : LiTFSI) which is a fluorinated imide compound, and lithium hexafluoroborate (LiPF ₆ ) which is another electrolyte salt. Was used.

  When assembling the secondary battery, the test electrode 51 was punched into a pellet and the test electrode 51 was accommodated in an outer can 52. Subsequently, after punching the counter electrode 53 into a pellet, the counter electrode 53 was accommodated in the exterior cup 54. Subsequently, the test electrode 51 accommodated in the outer can 52 and the counter electrode 53 accommodated in the outer cup 54 are laminated via a separator 55 (a microporous polypropylene microporous film having a thickness of 23 μm), and then a gasket. The outer can 52 and the outer cup 54 were caulked through 56. Thereby, a coin-type secondary battery was completed.

<2. Fabrication of laminated film type secondary battery>
The laminate film type secondary battery (lithium ion secondary battery) shown in FIGS. 3 and 4 was produced by the following procedure. In the following, the components of the coin-type secondary battery already described will be quoted as needed.

  In the case of producing the positive electrode 33, the positive electrode active material layer 33B was formed on both surfaces of the positive electrode current collector 33A by the same procedure as that for producing the test electrode 51. Further, when producing the negative electrode 34, the negative electrode active material layer 34 </ b> B was formed on both surfaces of the negative electrode current collector 34 </ b> A by the same procedure as the production procedure of the counter electrode 53.

  When preparing the electrolytic solution, the electrolyte salt was dissolved in the non-aqueous solvent by the same procedure as the procedure for preparing the electrolytic solution in the coin-type secondary battery.

  When assembling the secondary battery, first, the positive electrode lead 31 made of aluminum was welded to the positive electrode current collector 33A, and the negative electrode lead 32 made of copper was welded to the negative electrode current collector 34A. Subsequently, after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35 (23 μm-thick microporous polypropylene film), the positive electrode 33, the negative electrode 34, and the separator 35 are wound in the longitudinal direction. A rotating electrode body 30 was formed. Subsequently, a protective tape 37 was attached to the outermost peripheral portion of the wound electrode body 30. Subsequently, after the exterior member 40 was bent so as to sandwich the wound electrode body 30, the outer peripheral edge portions on the three sides of the exterior member 40 were heat-sealed. Thereby, the wound electrode body 30 was accommodated in the bag-shaped exterior member 40. The exterior member 40 includes a nylon film (30 μm thickness), an aluminum foil (40 μm thickness), and an unstretched polypropylene film (30 μm thickness) laminated in this order from the outside in a moisture resistant aluminum laminate film (total thickness 100 μm). ) Was used. Finally, an electrolyte solution was injected into the exterior member 40 and the wound electrode body 30 was impregnated with the electrolyte solution, and then the remaining one side of the exterior member 40 was heat-sealed in a reduced pressure environment. In this case, the adhesion film 41 (50 μm thick acid-modified propylene film) is inserted between the positive electrode lead 31 and the exterior member 40, and the adhesion film 41 is similarly inserted between the negative electrode lead 32 and the exterior member 40. Inserted. Thereby, a laminated film type secondary battery was completed.

  When producing this secondary battery, the thickness of the positive electrode active material layer 33B is adjusted so that the charge / discharge capacity of the negative electrode 34 is larger than the charge / discharge capacity of the positive electrode 33, and the negative electrode 34 is fully charged. Lithium metal was not precipitated.

<3. Evaluation of battery characteristics and safety>
When the initial charge / discharge characteristics and load characteristics were examined as battery characteristics, and the swelling characteristics and corrosion characteristics were examined as safety, the results shown in Table 1 were obtained. A coin-type secondary battery was used to examine the initial charge / discharge characteristics and load characteristics, and a laminate film-type secondary battery was used to examine the swelling characteristics.

  When examining the initial charge / discharge characteristics, first, the secondary battery was charged in a room temperature environment (23 ° C.), and the charge capacity was measured. Subsequently, the secondary battery was discharged in the same environment, and the discharge capacity was measured. From these measurement results, the initial efficiency (%) = (discharge capacity / charge capacity) × 100 was calculated. At the time of charging, the battery was charged with a current of 0.2 C until the voltage reached 4.35V. During discharging, discharging was performed at a current of 0.2 C until the voltage reached 2.5V. 0.2 C is a current value at which the battery capacity (theoretical capacity) can be discharged in 5 hours.

  When examining the load characteristics, except that the current at the time of discharge was changed to 1 C, the load retention rate (%) = (discharge capacity / discharge capacity) × by the same procedure as the case of examining the initial charge / discharge characteristics. 100 was calculated. 1C is a current value at which the battery capacity can be discharged in one hour.

  In Table 1, as the above-described initial efficiency value, values normalized by setting the initial efficiency value of Comparative Example 1-12 to 100 are shown. Further, “impossible” shown in Table 1 means that the initial efficiency could not be measured because the secondary battery could not be charged / discharged. These notations are the same for the load maintenance rate.

  When investigating the swollenness characteristics, the secondary battery was charged in a room temperature environment (23 ° C.), and then the thickness of the secondary battery was measured. Subsequently, the charged secondary battery was stored in a high-temperature environment (80 ° C.) (90 hours), and then the thickness of the secondary battery was measured. From these measurement results, the swelling rate (%) = [(thickness after storage−thickness before storage) / thickness before storage] × 100 was calculated. The charge / discharge conditions were the same as in the case of examining the initial charge / discharge characteristics.

  When investigating the corrosion characteristics, measure the current-potential curve with linear sweep voltammetry (LSV) using a triode cell together with the electrolyte, and determine the current (corrosion current) value that flows due to corrosion of aluminum. Examined. In this case, lithium was used as the reference electrode, platinum was used as the counter electrode, and aluminum was used as the working electrode. The voltage range was 0 V to 5 V with respect to lithium, and the sweep rate was 0.1 mV / s.

  In Table 1, as the above-described corrosion current value, a value normalized by setting the corrosion current value of Comparative Example 1-13 to 100 is shown.

  Each of the battery characteristics and safety varied depending on the respective composition of the non-aqueous solvent and the electrolyte salt, as described below. Here, the case where the non-aqueous solvent does not contain the fluorinated cyclic compound (FEC) and the electrolyte salt does not contain the fluorinated imide compound (LiTFSI) is used as a reference for comparison.

  When the non-aqueous solvent does not contain a fluorinated cyclic compound, but the electrolyte salt contains a fluorinated imide compound (Experimental Example 1-13), the corrosion current significantly increased compared to the comparative standard. . In this case, in particular, since the secondary battery cannot be charged / discharged, each of the initial efficiency and the load retention rate could not be calculated.

  In addition, when the non-aqueous solvent contains a fluorinated cyclic compound but the electrolyte salt does not contain a fluorinated imide compound (Experimental Example 1-14), the initial efficiency and load maintenance are compared with the comparison standard. Each of the rates increased, but the swelling rate also increased significantly.

  From these results, when the non-aqueous solvent contains a fluorinated cyclic compound and the electrolyte salt contains a fluorinated imide compound, the battery characteristics are improved in the first place as compared with the comparative standard. The secondary battery cannot be charged / discharged, and the safety is expected to deteriorate.

  However, in practice (Experimental Examples 1-1 to 1-4), each of the initial efficiency and the load maintenance rate increased while sufficiently suppressing the swelling rate and the corrosion current, respectively, as compared with the comparative standard.

  As a result, when the non-aqueous solvent contains a fluorinated cyclic compound and the electrolyte salt contains a fluorinated imide compound, the synergistic action of the fluorinated cyclic compound and the fluorinated imide compound leads to the above-mentioned prediction. This shows that an advantageous tendency to the contrary is obtained. Specifically, the decomposition reactivity of the electrolytic solution is suppressed even when charging and discharging are repeated. Moreover, the corrosion reaction of aluminum by the electrolytic solution is suppressed, and the generation of gas due to the reaction between the nonaqueous solvent and the electrolyte salt is also suppressed.

  However, when a fluorinated imide compound is used, if the nonaqueous solvent contains a fluorinated cyclic compound, the content of the fluorinated cyclic compound in the nonaqueous solvent may be any value. There wasn't. Specifically, when the content of the fluorinated cyclic compound is 95% to 100% by weight (Experimental Examples 1-1 to 1-4), the content is less than 95% by weight (Experimental Example 1-5). Unlike ˜1-7), since the secondary battery can be charged and discharged, the initial efficiency and the load maintenance ratio increased while sufficiently suppressing the swelling rate and the corrosion current.

In addition, when the electrolyte salt further contains LiPF ₆ (Experimental Examples 1-8 to 1-11), compared with the case where the electrolyte salt does not contain LiPF ₆ (Experimental Example 1-2), Although the swelling rate increased depending on the LiPF ₆ content, the initial efficiency and the load retention rate increased more.

(Experimental examples 2-1 to 2-7)
Except that the composition of the negative electrode mixture was changed, a secondary battery was produced by the same procedure and the battery characteristics and safety were examined. The results shown in Table 2 were obtained. In preparing the negative electrode mixture, 90 parts by mass of the negative electrode active material (graphite) and 10 parts by mass of the negative electrode binder (polyvinylidene fluoride) were mixed.

  Even when the composition of the negative electrode mixture was changed (Table 2), the same results as in Table 1 were obtained. That is, when a fluorinated cyclic compound and a fluorinated imide compound are used together, if the content of the fluorinated cyclic compound is 95 wt% to 100 wt% (Experimental Example 2-1), Good results were obtained as compared with cases other than (Experimental Examples 2-2 to 2-7).

  From the results shown in Table 1 and Table 2, the non-aqueous solvent contains a predetermined amount (95 wt% to 100 wt%) of a fluorinated cyclic compound, and the electrolyte salt contains a fluorinated imide compound. As a result, the battery characteristics were improved and the safety was improved. Therefore, the battery characteristics and safety are compatible in the secondary battery.

  As mentioned above, although this technique was demonstrated, giving an embodiment and an Example, this technique is not limited to the aspect demonstrated in embodiment and an Example, A various deformation | transformation is possible.

  For example, the case where the battery structure is a cylindrical type, a laminate film type, and a coin type and the battery element has a winding structure has been described as an example, but the present invention is not limited thereto. The secondary battery of the present technology can be similarly applied even when other battery structures such as a square type and a button type are provided. Further, the secondary battery of the present technology can be similarly applied when the battery element has another structure such as a laminated structure.

  Moreover, the electrolyte solution for secondary batteries of this technique may be applied not only to a secondary battery but to other electrochemical devices. Other electrochemical devices are, for example, capacitors.

  In addition, the effect described in this specification is an illustration to the last, and is not limited, Moreover, there may exist another effect.

（Ｒ１〜Ｒ４のそれぞれは、水素基（−Ｈ）、フッ素基（−Ｆ）、アルキル基およびフッ素化アルキル基のうちのいずれかであり、そのＲ１〜Ｒ４のうちの少なくとも１つは、フッ素基およびフッ素化アルキル基のうちのいずれかである。）
ＬｉＮ（Ｒ５ＳＯ₂ ）（Ｒ６ＳＯ₂ ） ・・・（２）
（Ｒ５およびＲ６のそれぞれは、フッ素基およびフッ素化アルキル基のうちのいずれかである。）
（２）
前記Ｒ１〜Ｒ４のそれぞれは、水素基およびフッ素基のうちのいずれかであり、そのＲ１〜Ｒ４のうちの少なくとも１つは、フッ素基である、
上記（１）に記載の二次電池。
（３）
前記フッ素化環状化合物は、４−フルオロ−１，３−ジオキソラン−２−オンを含む、
上記（１）または（２）に記載の二次電池。
（４）
前記非水溶媒中における前記フッ素化環状化合物の含有量は、１００重量％未満であり、
前記非水溶媒は、環状炭酸エステルおよび鎖状炭酸エステルのうちの少なくとも一方を含む、
上記（１）ないし（３）のいずれかに記載の二次電池。
（５）
前記Ｒ５およびＲ６のそれぞれは、フッ素基およびパーフルオロアルキル基のうちのいずれかである、
上記（１）ないし（４）のいずれかに記載の二次電池。
（６）
前記フッ素化イミド化合物は、ＬｉＮ（ＦＳＯ₂ ）₂ 、ＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ およびＬｉＮ（Ｃ₂ Ｆ₅ ＳＯ₂ ）₂ のうちの少なくとも１種を含む、
上記（１）ないし（５）のいずれかに記載の二次電池。
（７）
前記フッ素化イミド化合物の含有量は、前記非水溶媒に対して、０．６ｍｏｌ／ｋｇ〜２ｍｏｌ／ｋｇである、
上記（１）ないし（６）のいずれかに記載の二次電池。
（８）
リチウム二次電池である、
上記（１）ないし（７）のいずれかに記載の二次電池。
（９）
非水溶媒および電解質塩を含み、
前記非水溶媒は、式（１）で表されるフッ素化環状化合物を含み、
前記電解質塩は、式（２）で表されるフッ素化イミド化合物を含み、
前記非水溶媒中における前記フッ素化環状化合物の含有量は、９５重量％〜１００重量％である、
二次電池用電解液。

（Ｒ１〜Ｒ４のそれぞれは、水素基（−Ｈ）、フッ素基（−Ｆ）、アルキル基およびフッ素化アルキル基のうちのいずれかであり、そのＲ１〜Ｒ４のうちの少なくとも１つは、フッ素基およびフッ素化アルキル基のうちのいずれかである。）
ＬｉＮ（Ｒ５ＳＯ₂ ）（Ｒ６ＳＯ₂ ） ・・・（２）
（Ｒ５およびＲ６のそれぞれは、フッ素基およびフッ素化アルキル基のうちのいずれかである。）
（１０）
上記（１）ないし（８）のいずれかに記載の二次電池と、
その二次電池の動作を制御する制御部と、
その制御部の指示に応じて前記二次電池の動作を切り換えるスイッチ部と
を備えた、電池パック。
（１１）
上記（１）ないし（８）のいずれかに記載の二次電池と、
その二次電池から供給された電力を駆動力に変換する変換部と、
その駆動力に応じて駆動する駆動部と、
前記二次電池の動作を制御する制御部と
を備えた、電動車両。
（１２）
上記（１）ないし（８）のいずれかに記載の二次電池と、
その二次電池から電力を供給される１または２以上の電気機器と、
前記二次電池からの前記電気機器に対する電力供給を制御する制御部と
を備えた、電力貯蔵システム。
（１３）
上記（１）ないし（８）のいずれかに記載の二次電池と、
その二次電池から電力を供給される可動部と
を備えた、電動工具。
（１４）
上記（１）ないし（８）のいずれかに記載の二次電池を電力供給源として備えた、電子機器。 In addition, this technique can also take the following structures.
(1)
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes a fluorinated cyclic compound represented by the formula (1),
The electrolyte salt includes a fluorinated imide compound represented by the formula (2),
The content of the fluorinated cyclic compound in the non-aqueous solvent is 95 wt% to 100 wt%,
Secondary battery.

(Each of R1 to R4 is any one of a hydrogen group (—H), a fluorine group (—F), an alkyl group and a fluorinated alkyl group, and at least one of R1 to R4 is a fluorine group) Any one of a group and a fluorinated alkyl group.)
LiN (R5SO ₂ ) (R6SO ₂ ) (2)
(R5 and R6 are each a fluorine group or a fluorinated alkyl group.)
(2)
Each of R1 to R4 is either a hydrogen group or a fluorine group, and at least one of R1 to R4 is a fluorine group.
The secondary battery as described in said (1).
(3)
The fluorinated cyclic compound includes 4-fluoro-1,3-dioxolan-2-one,
The secondary battery according to (1) or (2) above.
(4)
The content of the fluorinated cyclic compound in the non-aqueous solvent is less than 100% by weight,
The non-aqueous solvent includes at least one of a cyclic carbonate and a chain carbonate,
The secondary battery according to any one of (1) to (3).
(5)
Each of R5 and R6 is either a fluorine group or a perfluoroalkyl group.
The secondary battery according to any one of (1) to (4) above.
(6)
The fluorinated imide compound includes at least one of LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ .
The secondary battery according to any one of (1) to (5) above.
(7)
The content of the fluorinated imide compound is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent.
The secondary battery according to any one of (1) to (6) above.
(8)
Lithium secondary battery,
The secondary battery according to any one of (1) to (7) above.
(9)
Including a non-aqueous solvent and an electrolyte salt,
The non-aqueous solvent includes a fluorinated cyclic compound represented by the formula (1),
The electrolyte salt includes a fluorinated imide compound represented by the formula (2),
The content of the fluorinated cyclic compound in the non-aqueous solvent is 95 wt% to 100 wt%,
Secondary battery electrolyte.

(Each of R1 to R4 is any one of a hydrogen group (—H), a fluorine group (—F), an alkyl group and a fluorinated alkyl group, and at least one of R1 to R4 is a fluorine group) Any one of a group and a fluorinated alkyl group.)
LiN (R5SO ₂ ) (R6SO ₂ ) (2)
(R5 and R6 are each a fluorine group or a fluorinated alkyl group.)
(10)
The secondary battery according to any one of (1) to (8) above;
A control unit for controlling the operation of the secondary battery;
A battery pack comprising: a switch unit that switches the operation of the secondary battery in accordance with an instruction from the control unit.
(11)
The secondary battery according to any one of (1) to (8) above;
A converter that converts electric power supplied from the secondary battery into driving force;
A drive unit that drives according to the driving force;
An electric vehicle comprising: a control unit that controls the operation of the secondary battery.
(12)
The secondary battery according to any one of (1) to (8) above;
One or more electric devices supplied with power from the secondary battery;
And a control unit that controls power supply from the secondary battery to the electrical device.
(13)
The secondary battery according to any one of (1) to (8) above;
And a movable part to which electric power is supplied from the secondary battery.
(14)
An electronic apparatus comprising the secondary battery according to any one of (1) to (8) as a power supply source.

  20, 30 ... wound electrode body, 21, 33 ... positive electrode, 21A, 33A ... positive electrode current collector, 21B, 33B ... positive electrode active material layer, 22, 34 ... negative electrode, 22A, 34A ... negative electrode current collector, 22B, 34B ... negative electrode active material layer, 23, 35 ... separator, 36 ... electrolyte layer, 40 ... exterior member.

Claims (8)

A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Secondary battery . Lithium secondary battery,
The secondary battery according to claim 1. Including a non-aqueous solvent and an electrolyte salt,
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Secondary battery electrolyte . A secondary battery,
A control unit for controlling the operation of the secondary battery;
A switch unit for switching the operation of the secondary battery according to an instruction of the control unit,
The secondary battery is
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Battery pack . A secondary battery,
A converter that converts electric power supplied from the secondary battery into driving force;
A drive unit that drives according to the driving force;
A control unit for controlling the operation of the secondary battery,
The secondary battery is
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Electric vehicle . A secondary battery,
One or more electric devices supplied with power from the secondary battery;
A control unit for controlling power supply from the secondary battery to the electrical device,
The secondary battery is
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Power storage system . A secondary battery,
A movable part to which electric power is supplied from the secondary battery,
The secondary battery is
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Electric tool . A secondary battery is provided as a power supply source,
The secondary battery is
A positive electrode;
A negative electrode,
An electrolyte containing a non-aqueous solvent and an electrolyte salt, and
The non-aqueous solvent includes 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate ,
The electrolyte salt includes bis (trifluoromethanesulfonyl) imide lithium and lithium hexafluorophosphate ,
The content of the 4-fluoro-1,3-dioxolan-2-one in the nonaqueous solvent is, Ri 95 wt% to 100 wt% der,
The sum of the ethylene carbonate content in the non-aqueous solvent and the propylene carbonate content in the non-aqueous solvent is 0 wt% to 5 wt%,
The content of the bis (trifluoromethanesulfonyl) imide lithium is 0.6 mol / kg to 2 mol / kg with respect to the non-aqueous solvent,
The ratio of the amount of the lithium hexafluorophosphate to the amount of the bis (trifluoromethanesulfonyl) imide lithium is 0 mol% to 40 mol%.
Electronic equipment .

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