JP2006318839A - Non-aqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery which is excellent in an overcharge resistance property and is enabled to control a swelling in case a charging continues for a long time. <P>SOLUTION: A nonaqueous secondary battery is composed of a cathode, an anode and nonaqueous electrolyte, and the above nonaqueous electrolyte contains cyclohexylbenzene by 3 mass% or less, as well as viphenyl, fluorobenzene and t-alkylbenzene. It is preferable that the nonaqueous secondary battery is provided with the nonaqueous electrolyte containing cyclohexylbenzene by 3 mass% or less, viphenyl by 0.1 to 0.5 mass%, fluorobenzene by 1 mass% or more and t-alkylbenzene by 1 mass% or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery.

  Conventionally, a technique has been implemented in which a special additive is contained in a non-aqueous electrolyte of a non-aqueous secondary battery to prevent ignition of the battery during overcharge and to ensure safety. In the non-aqueous secondary battery, the electrode and the non-aqueous electrolyte are in contact with each other, and the decomposition reaction of the non-aqueous electrolyte may occur.However, when the battery is overcharged, this decomposition reaction proceeds, Along with this, ignition occurs due to the high temperature inside the battery. Therefore, in the above technique, for example, as the additive, a material that can be polymerized under a high voltage to form a film on the electrode surface is used, and the contact between the electrode and the non-aqueous electrolyte is suppressed by the film. The decomposition reaction of the water electrolyte component is suppressed, and the ignition of the battery at the time of overcharge is prevented. As such an additive, for example, biphenyl, cyclohexylbenzene and the like are known.

  In the non-aqueous secondary battery, in addition to safety at the time of overcharge, the present inventors also bonded a halogen group to the benzene ring as a technique capable of suppressing gas generation during high-temperature storage and ensuring storage reliability. A technology that uses a nonaqueous electrolytic solution containing a compound and an aromatic and / or heterocyclic compound that is oxidized at a lower potential than that of the compound has been developed, and a patent application has been filed (Patent Document 1).

JP 2003-187868 A

  By the way, recently, in a device using a non-aqueous secondary battery as a driving power source, a usage form in which continuous use of the device and charging of the non-aqueous secondary battery are performed simultaneously (for example, a non-aqueous secondary battery is used as a driving power source) The usage pattern that has not been so far used is increasing, such as Internet communication using a mobile phone or the like, which is performed while charging the non-aqueous secondary battery.

  Under such usage, since the non-aqueous secondary battery is charged at the same time as the discharge, the non-aqueous secondary battery is not fully charged, and charging will continue for a long time. As a result, the voltage of the non-aqueous secondary battery may exceed the rated voltage (for example, 4.2V) and become an overvoltage state of 4.3V or more. In a non-aqueous secondary battery provided with a non-aqueous electrolyte containing the additive as described above, such continuous charging is performed and an overvoltage state occurs, whereby the unreacted polymerization reaction of the additive is performed. Progresses, and the generation of gas in the battery may cause the battery to swell, resulting in deterioration of battery characteristics.

  Some chargers for non-aqueous secondary batteries have control means for preventing the non-aqueous secondary battery from entering an overvoltage state, but some inexpensive chargers have such control means. Some are not equipped with. Therefore, in the non-aqueous secondary battery including the non-aqueous electrolyte containing the additive as described above, the battery swells when charging is continued for a long time as in the case where charging and discharging are performed simultaneously. There was still room for improvement in terms of concerns.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous secondary battery that is excellent in overcharge resistance and that suppresses swelling when charging continues for a long period of time. It is in.

  The non-aqueous secondary battery of the present invention that can achieve the above object has a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the non-aqueous electrolyte contains 3% by mass or less of cyclohexylbenzene, And biphenyl, fluorobenzene and t-alkylbenzene.

  The present invention is effective for ensuring the overcharge resistance performance of the battery, while reducing the content of cyclohexylbenzene in the non-aqueous electrolyte, which causes battery swelling when the battery is charged for a long period of time. Thus, by suppressing the battery swelling, biphenyl, fluorobenzene, and t-alkylbenzene are contained in the non-aqueous electrolyte, thereby suppressing a decrease in overcharge resistance performance due to a decrease in the amount of cyclohexylbenzene.

  Biphenyl can be a polymer for polymerizing under a high voltage to form a film on the electrode surface, similarly to cyclohexylbenzene, but this biphenyl has a lower oxidation potential than cyclohexylbenzene. Therefore, in the battery, biphenyl begins to polymerize before cyclohexylbenzene, which promotes the polymerization of cyclohexylbenzene and contributes to the formation of a more uniform film, which improves the battery's overcharge resistance. it is conceivable that. In addition, fluorobenzene and t-alkylbenzene have a higher oxidation potential than cyclohexylbenzene, and thus can contribute to an improvement in safety when the battery becomes a higher voltage due to overcharging.

  In the present invention, by combining biphenyl, fluorobenzene, and t-alkylbenzene having different characteristics as described above, the influence due to the reduction in the amount of cyclohexylbenzene can be suppressed and good overcharge resistance (ignition during overcharge can be suppressed). Performance) and suppression of swelling when battery charging continues for a long period of time.

  In producing the non-aqueous secondary battery of the present invention, cyclohexylbenzene is 3% by mass or less, biphenyl is 0.1 to 0.5% by mass, fluorobenzene is 1% by mass or more, and t-alkylbenzene is added. It is preferable to use a non-aqueous electrolyte containing 1% by mass or more.

  According to the present invention, it is possible to provide a non-aqueous secondary battery that is excellent in safety during overcharge and that suppresses the occurrence of swelling even when charging is continued for a long period of time.

  As described above, the nonaqueous secondary battery of the present invention has a nonaqueous electrolytic solution containing cyclohexylbenzene, biphenyl, fluorobenzene and t-alkylbenzene, but the content of cyclohexylbenzene in the total amount of the nonaqueous electrolytic solution. The amount is 3% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less. If the content of cyclohexylbenzene in the non-aqueous electrolyte is too large, the battery will swell when the battery is charged for a long period of time. In the battery in which the swelling has occurred, there is a possibility that the battery characteristics may be deteriorated. Note that if the content of cyclohexylbenzene in the nonaqueous electrolyte solution of the nonaqueous secondary battery is too small, the effect of improving the overcharge resistance of the battery due to the use of cyclohexylbenzene may be reduced. Therefore, the content of cyclohexylbenzene in the non-aqueous electrolyte is preferably 0.5% by mass or more and more preferably 1.0% by mass or more in the total amount of the non-aqueous electrolyte.

  The nonaqueous electrolytic solution used for producing the nonaqueous secondary battery of the present invention preferably contains cyclohexylbenzene, biphenyl, fluorobenzene, and t-alkylbenzene in respective contents described later.

  The content of cyclohexylbenzene in the non-aqueous electrolyte used for manufacturing the non-aqueous secondary battery is, for example, 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1.5% in the total amount of the non-aqueous electrolyte. It is desirable that it is less than mass%. By adjusting the content of cyclohexylbenzene in the non-aqueous electrolyte used in the production of the non-aqueous secondary battery in this way, the content of cyclohexylbenzene in the non-aqueous electrolyte of the battery is less than the above upper limit value. It can be. In order to make the content of cyclohexylbenzene in the non-aqueous electrolyte of the non-aqueous secondary battery equal to or more than the above preferred lower limit, cyclohexyl benzene in the non-aqueous electrolyte used for the production of the non-aqueous secondary battery The content of is, for example, preferably 0.5% by mass or more, more preferably 1.0% by mass or more in the total amount of the non-aqueous electrolyte.

  The content of biphenyl in the non-aqueous electrolyte used for manufacturing the non-aqueous secondary battery is, for example, 0.1% by mass or more, more preferably 0.2% by mass or more in the total amount of the non-aqueous electrolyte, It is desirable that it is 0.5 mass% or less, More preferably, it is 0.4 mass% or less. If the content of biphenyl in the non-aqueous electrolyte used for manufacturing the non-aqueous secondary battery is too small, the effect of improving the overcharge resistance of the non-aqueous secondary battery by using biphenyl may be reduced. In addition, if the biphenyl content is too high, the biphenyl has a low oxidation potential, which may cause polymerization during charging and cause deterioration of charge / discharge cycle characteristics. The swelling suppression effect may be reduced.

  The fluorobenzene referred to in the present invention is not limited as long as at least one hydrogen of the benzene ring is substituted with fluorine. For example, in addition to monofluorobenzene, 2 of the benzene ring such as difluorobenzene and trifluorobenzene is used. One having two or more hydrogens substituted with fluorine, or one having a functional group other than fluorine, such as fluoroanisole, may be used. Of these, monofluorobenzene having excellent stability under high voltage is more preferable.

  The content of fluorobenzene in the non-aqueous electrolyte used for the production of the non-aqueous secondary battery is, for example, preferably 1% by mass or more, more preferably 3% by mass or more in the total amount of the non-aqueous electrolyte. If the content of fluorobenzene in the non-aqueous electrolyte used for the production of the non-aqueous secondary battery is too small, the effect of improving the overcharge resistance of the non-aqueous secondary battery by using fluorobenzene may be reduced. . Moreover, when there is too much content of fluorobenzene, there exists a possibility that the load characteristic of a battery may fall. Therefore, the content of fluorobenzene in the non-aqueous electrolyte used for the production of the non-aqueous secondary battery is, for example, preferably 4% by mass or less, and preferably 3% by mass or less in the total amount of the non-aqueous electrolyte. Is more preferable.

  The t-alkylbenzene contained in the non-aqueous electrolyte, like fluorobenzene, has a higher oxidation potential than cyclohexylbenzene, and contributes to ensuring safety when the battery becomes higher voltage due to overcharging. Has the same action as benzene. Such an action is better for fluorobenzene than for t-alkylbenzene, but if the fluorobenzene content in the non-aqueous electrolyte is increased too much, the above-mentioned problems may occur. , T-alkylbenzene can be used in combination to reduce the amount of fluorobenzene.

  As a t-alkyl group which t-alkylbenzene has, a C4-C8 t-alkyl group is preferable, for example. Therefore, specific examples of t-alkylbenzene include t-butylbenzene, t-pentylbenzene, 1,3-di-t-butylbenzene, 1,4-di-t-butylbenzene, and the like.

  The content of t-alkylbenzene in the non-aqueous electrolyte used for the production of the non-aqueous secondary battery is, for example, preferably 1% by mass or more, more preferably 1.5% by mass or more in the total amount of the non-aqueous electrolyte. . If the content of t-alkylbenzene in the non-aqueous electrolyte used in the production of the non-aqueous secondary battery is too small, the effect of improving the overcharge resistance of the non-aqueous secondary battery due to the use of t-alkyl benzene will be reduced. There is. Moreover, when there is too much content of t-alkylbenzene, charging / discharging cycling characteristics may fall. Therefore, the content of t-alkylbenzene in the nonaqueous electrolytic solution used for manufacturing the nonaqueous secondary battery is, for example, preferably 5% by mass or less in the total amount of the nonaqueous electrolytic solution, and 4% by mass or less. It is more preferable.

As shown in Table 1, biphenyl has a lower oxidation potential than cyclohexylbenzene, and fluorobenzene and t-alkylbenzene have a higher oxidation potential than cyclohexylbenzene. Based on such an oxidation potential, each of these additives can exert the above-described action. Incidentally, the oxidation potential shown in Table 1 is a value measured as follows. In a 1: 2 (volume ratio) mixed solvent of ethylene carbonate and methyl ethyl carbonate, LiPF ₆ was dissolved at 1.0 mol / l, and the compound to be measured was dissolved at 2% by mass to perform electrolysis. A liquid was prepared. A counter electrode made of a lithium foil, a reference electrode, and a working electrode made of a platinum plate are immersed in the above electrolyte solution, and a potential scan at 50 mV / sec is performed to measure the potential at which an oxidation current of 10 μA / cm ² flows. The oxidation potential of the compound was used.

  The non-aqueous electrolyte used for the production of the non-aqueous secondary battery is not particularly limited as long as it contains cyclohexylbenzene, biphenyl, fluorobenzene and t-alkylbenzene. The same composition as the non-aqueous electrolyte used in the secondary battery can be used.

  Examples of the organic solvent used for the non-aqueous electrolyte include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), and the like. Carbonic acid esters; esters other than carbonic acid esters such as γ-butyrolactone (γ-BL) and methyl acetate (EA); ethers such as 1,3-dioxolane and 1,2-dimethoxyethane; sulfur such as sulfolane Compounds; nitrogen-containing compounds; silicon-containing compounds; fluorine-containing compounds; phosphorus-containing compounds; These organic solvents may be used individually by 1 type, respectively, and may use 2 or more types together.

In the nonaqueous electrolytic solution used for the production of the nonaqueous secondary battery, an electrolyte salt is dissolved in the above organic solvent together with cyclohexylbenzene, biphenyl, fluorobenzene and t-alkylbenzene. Specific examples of the electrolyte salt include, for example, LiPF ₆ , LiC _n F _{2n + 1} SO ₃ (n> 1), LiClO ₄ , LiBF ₄ , LiAsF ₆ , (CnF _{2n + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ) NLi ( m, n ≧ 1), (RfOSO ₂ ) ₂ NLi [Rf is an alkyl group containing a halogen having 2 or more carbon atoms, Rf may be different, or Rf may be bonded to each other. . For _{example, (CH 2 (CF 2)} 4 CH 2 OSO 2 N (Li) SO 2 O) 2: may be bonded to polymeric as (n an integer). ] Lithium salt etc. are mentioned. The concentration of the electrolyte salt in the nonaqueous electrolytic solution is preferably 0.1 to 2 mol / l, for example. Among the electrolyte salts, LiPF ₆ and fluorine-containing organic lithium salts having 2 or more carbon atoms are preferable. Further, a known gelling agent may be added to the nonaqueous electrolytic solution to form a gelled electrolytic solution (electrolyte).

  The non-aqueous secondary battery of the present invention is not particularly limited with respect to the configuration other than the non-aqueous electrolyte, and each configuration used in conventionally known non-aqueous secondary batteries can be employed.

  As the positive electrode, for example, a positive electrode mixture layer containing a positive electrode active material, a conductive additive, and a binder such as polyvinylidene fluoride (PVDF) is provided on one side of a conductive substrate such as an aluminum foil that functions as a current collector or Those formed on both sides can be used. Such a positive electrode includes, for example, a positive electrode mixture-containing composition (paste,) obtained by dispersing or dissolving a positive electrode active material, a conductive additive, and a binder in a solvent such as N-methyl-2-pyrrolidone (NMP). Slurry, etc.) is applied to one or both sides of the conductive substrate, the solvent is removed by drying to form a positive electrode mixture layer, and press treatment is performed as necessary to adjust the thickness and density of the positive electrode mixture layer. Can be manufactured. However, the positive electrode used in the battery of the present invention is not limited to those manufactured by the above-described manufacturing method, and those manufactured by other manufacturing methods can also be used.

Examples of the positive electrode active material include lithium cobalt oxide such as LiCoO ₂ ; lithium manganese oxide such as LiMn ₂ O ₄ ; lithium nickel oxide such as LiNiO ₂ ; metal such as manganese dioxide, vanadium pentoxide, and chromium oxide. Oxides; metal sulfides such as titanium disulfide and molybdenum disulfide; and the like. Among these, lithium-containing composite oxides such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNiO ₂ are more preferable, and LiCoO ₂ and LiNiO ₂ are particularly preferable. These lithium-containing composite oxides may be those in which a part of metal elements such as Co and Ni are substituted with one or more metal elements such as Mg, Al, Zr, Ti and Mn. Furthermore, these metal element oxides may be contained on the surface of these lithium-containing composite oxides.

As the conductive assistant for the positive electrode, various conventionally known conductive assistants can be used, and a carbon material is particularly preferable. The type of the carbon material is not particularly limited, but a carbon material such as carbon black having low crystallinity is particularly preferable because it can suppress battery swelling during high-temperature storage. In addition, since the content of the conductive additive in the positive electrode mixture layer can be reduced, such a low crystallinity carbon material may be used in combination with a high crystallinity carbon material (for example, a graphite-based carbon material). preferable. If the content of the conductive additive in the positive electrode mixture layer can be reduced, the content of the positive electrode active material can be increased, so that the battery capacity can be improved. When using a carbon material having low crystallinity and a carbon material having high crystallinity, the amount of the carbon material having low crystallinity in the total amount of the conductive aid is, for example, 50% by mass or more, more preferably 70% by mass or more. Thus, it is desirable that the content be 95% by mass or less, more preferably 80% by mass or less. Note that the crystallinity of the carbon material is generally determined as a carbon material having a low crystallinity when the (002) plane spacing is larger than 0.345 nm. half-value width of the peak of ～1600Cm ^-1 is 100 cm ^-1 or more at which those can be certified crystallinity is low carbon material.

  The content of the conductive additive in the positive electrode mixture layer is, for example, preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2.5% by mass or less. This is because if the positive electrode mixture layer contains too much conductive additive, gas may easily be generated due to reaction with the non-aqueous electrolyte solvent during battery charging. On the other hand, if the content of the conductive additive in the positive electrode mixture layer is too small, the conductivity of the positive electrode may be reduced and the battery characteristics may be deteriorated. Therefore, the conductive auxiliary agent content in the positive electrode mixture layer is, for example, 0 It is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and further preferably 2% by mass or more.

  In the positive electrode mixture layer, the binder content is preferably 1 to 5% by mass, for example, and the positive electrode active material content is preferably 95 to 98.5% by mass, for example. .

In the present invention, even when a positive electrode having a positive electrode mixture layer having a large specific surface area is used, battery swelling can be suppressed. Therefore, from the viewpoint of improving battery characteristics, the specific surface area of the positive electrode mixture layer is, for example, preferably 0.4 m ² / g or more, and more preferably 0.5 m ² / g or more. On the other hand, if the specific surface area of the positive electrode mixture layer becomes too large, the reactivity with the electrolytic solution tends to increase. Therefore, the specific surface area of the positive electrode mixture layer may be 1 m ² / g or less. Preferably, it is 0.7 m ² / g or less.

  As the negative electrode according to the nonaqueous secondary battery of the present invention, for example, a carbon material or a negative electrode active material such as a metal oxide or metal nitride capable of inserting and removing Li, a binder such as PVDF, and the like are further required Depending on the case, a layer formed by forming a negative electrode mixture layer containing a conductive additive on one or both sides of a conductive substrate such as a copper foil functioning as a current collector can be used. Such a negative electrode includes, for example, a negative electrode mixture-containing composition (paste, slurry, etc.) obtained by dispersing or dissolving a negative electrode active material and a binder (and a conductive aid) in a solvent such as NMP. The negative electrode mixture layer can be produced by applying it to one or both surfaces of the conductive substrate, drying the solvent to form a negative electrode mixture layer, and performing a press treatment as necessary to adjust the thickness and density of the negative electrode mixture layer. However, the negative electrode used in the battery of the present invention is not limited to those manufactured by the above-described manufacturing method, and those manufactured by other manufacturing methods can also be used.

Examples of the metal oxide capable of inserting and removing Li that can be used as the negative electrode active material include oxides containing Sn and Si, specifically, SnO ₂ and SiO ₂ . Examples of the metal nitride capable of inserting and removing Li that can be used as the negative electrode active material include Li _2.6 Co _0.4 N.

  Further, the separator interposed between the positive electrode and the negative electrode is not particularly limited, and for example, a microporous resin film used in a conventionally known nonaqueous secondary battery can be used. Examples of the microporous resin film include microporous polyethylene film, microporous polypropylene film, microporous ethylene-propylene copolymer film, microporous polypropylene / polyethylene bilayer film, microporous polypropylene / polyethylene / polypropylene 3 Examples thereof include a layer film.

  The thickness of the separator is preferably thinner from the viewpoint of improving the energy density of the battery, and is preferably 20 μm or less, for example, but is preferably 10 μm or more from the viewpoint of ensuring safety. The separator porosity is preferably 42% or less, and is preferably 40% or less because the effect of using each of the above additives in the non-aqueous electrolyte may be reduced if the separator is too large. More preferably, it is more preferably 38% or less. On the other hand, the separator porosity is preferably 30% or more, more preferably 33% or more, and more preferably 35% or more because the load characteristics of the battery may be deteriorated if the porosity is too small. More preferably.

If the air permeability of the separator is too small, the effect of using each of the above additives in the non-aqueous electrolyte may be reduced. Therefore, it is preferably 200 seconds / 100 cm ³ or more, and preferably 300 seconds / 100 cm. More preferably, it is ³ or more. On the other hand, if the air permeability of the separator is too large, battery characteristics may be deteriorated, and therefore, it is preferably 500 seconds / 100 cm ³ or less, and more preferably 400 seconds / 100 cm ³ or less.

  In the non-aqueous secondary battery of the present invention, the constituent elements such as the non-aqueous electrolyte solution, the positive electrode, the negative electrode, and the separator described above are loaded into the battery case by a conventionally known method, and the opening of the battery case is sealed. Use batteries. The non-aqueous secondary battery of the present invention thus obtained is a thin battery having a relatively small internal volume, such as a laminated battery (battery having an aluminum laminate film as an outer package) or a square battery. The effect becomes remarkable. However, the non-aqueous secondary battery of the present invention is not limited to the above-described form, and may be various conventionally known forms such as a cylindrical battery (cylindrical battery, etc.), a button-type battery (coin-type battery), etc. In such a form, the effect can be secured.

In addition, the non-aqueous secondary battery of the present invention is a mode having a high possibility of ignition during overcharge, such as a high capacity battery (for example, a battery having a discharge capacity of 130 mAh / cm ³ or more). Such ignition can be suppressed and good safety can be ensured. In order to increase the capacity of the non-aqueous secondary battery of the present invention as described above, for example, the conductive auxiliary agent content in the positive electrode mixture layer is limited to the preferred upper limit value or less, and further, the positive electrode A method of increasing the density of the positive electrode mixture layer or the negative electrode mixture layer by press treatment when forming the mixture layer or the negative electrode mixture layer can be employed.

  The non-aqueous secondary battery of the present invention can be applied to various uses where a conventionally known non-aqueous secondary battery is used, and in particular, a mobile phone or a notebook personal computer that may be charged and discharged simultaneously. It can be suitably used as a drive power source for various portable devices such as PDAs (personal personal digital assistants).

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

Example 1
<Preparation of non-aqueous electrolyte>
LiPF ₆ was dissolved at a concentration of 1.2 mol / l in a 1: 2 (volume ratio) mixed solvent of EC and MEC to obtain a solution. Further, cyclohexylbenzene, biphenyl, fluorobenzene (monofluorobenzene) and t-butylbenzene are dissolved in this solution so that the concentrations are 2% by mass, 0.2% by mass, 3% by mass and 2% by mass, respectively. To prepare a non-aqueous electrolyte.

<Preparation of positive electrode>
LiCoO _{2 as a} positive electrode active material (specific surface area 0.5 g / m ² ): 93.5 parts by mass, carbon black: 2.0 parts by mass, graphite (“KS-6” manufactured by Lonza): 0.5 Part by mass was added and mixed. The obtained mixture was added to and mixed with an NMP solution in which 4 parts by mass of PVDF had been dissolved in advance to prepare a positive electrode mixture-containing paste. This positive electrode mixture-containing paste is uniformly applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, dried to form a positive electrode mixture layer, and the positive electrode mixture layer is further formed by a roller press. After pressurizing, it was cut into a predetermined size, and a lead body was welded to the current collector to produce a strip-shaped positive electrode. However, in the above positive electrode, in the electrode laminate having a wound structure in which the positive electrode after production is wound after being overlapped with the negative electrode via a separator, the portion on the inner surface side of the innermost peripheral portion not facing the negative electrode is A positive electrode mixture layer was not formed.

<Production of negative electrode>
95 parts by mass of mesocarbon microbead fired body as a negative electrode active material was added to and mixed with a solution in which 5 parts by mass of PVDF was previously dissolved in NMP to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste is uniformly applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 10 μm, dried to form a negative electrode mixture layer, and the negative electrode mixture layer is further formed by a roller press. After pressurizing, it was cut into a predetermined size, and a lead body was welded to the current collector to produce a strip-shaped negative electrode. However, in the negative electrode, in the electrode laminate having a wound structure in which the prepared negative electrode is overlapped with the positive electrode via a separator and wound, the inner surface portion of the innermost peripheral portion that does not face the positive electrode The negative electrode mixture layer was not formed.

<Battery assembly>
After the above positive electrode and negative electrode were stacked via a separator made of a microporous polyethylene film having a thickness of 20 μm, a porosity of 37%, and an air permeability of 400 seconds / 100 cm ³ , Pressurization was performed so as to form a flat shape to obtain an electrode laminate having a flat wound structure. Thereafter, an insulating tape was attached to the electrode laminate, and the outer dimensions were inserted into a rectangular battery case having a thickness (depth) of 4 mm, a width of 30 mm, and a height of 48 mm, and provided on a lid for welding and sealing the lead body. The nonaqueous electrolyte solution was injected into the battery case from the electrolyte solution inlet. Thereafter, after the non-aqueous electrolyte sufficiently permeates the separator or the like, the electrolyte solution inlet is sealed to seal the inside of the battery case, and then precharging and aging are performed, as shown in FIG. A prismatic non-aqueous secondary battery having a structure as shown in FIG. 2 was produced.

  Here, the battery shown in FIGS. 1 and 2 will be described. The positive electrode 1 and the negative electrode 2 are wound in a spiral shape through the separator 3 as described above, and then pressed so as to become a flat shape. The electrode laminate 6 having a structure is accommodated in a rectangular battery case 4 together with a non-aqueous electrolyte. However, in FIG. 1, in order to avoid complication, a metal foil, a non-aqueous electrolyte, and the like as a conductive substrate used in manufacturing the positive electrode 1 and the negative electrode 2 are not illustrated.

  The battery case 4 is made of an aluminum alloy and constitutes a battery exterior material. The battery case 4 also serves as a positive electrode terminal. And the insulator 5 which consists of a polyethylene sheet is arrange | positioned at the bottom part of the battery case 4, From the electrode laminated body 6 of the flat winding structure which consists of the said positive electrode 1, the negative electrode 2, and the separator 3, the positive electrode 1 and the negative electrode 2 of A positive electrode lead body 7 and a negative electrode lead body 8 respectively connected to one end are drawn out. A stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the battery case 4 via a polypropylene insulating packing 10, and an insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached.

  And this cover plate 9 is inserted in the opening part of the said battery case 4, and the opening part of the battery case 4 is sealed by welding the junction part of both, and the inside of a battery is sealed.

  The lid plate 9 is provided with an electrolyte inlet 14, and when the battery is assembled, a nonaqueous electrolyte is injected into the battery from the electrolyte inlet 14, and then the electrolyte inlet 14 is sealed. Therefore, in FIG. 1, it is expressed as the electrolyte solution inlet 14, but in the completed battery, 14 is a trace of the sealed electrolyte solution inlet. The cover plate 9 is provided with an explosion-proof safety valve 15.

  In the battery of Example 1, the battery case 4 and the cover plate 9 function as positive terminals by directly welding the positive electrode lead body 7 to the cover plate 9, and the negative electrode lead body 8 is welded to the lead plate 13, The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the battery case 4, the sign may be reversed. There is also.

  FIG. 2 is a perspective view schematically showing the external appearance of the battery shown in FIG. 1. FIG. 2 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 1, the inner peripheral portion of the electrode body is not cross-sectional.

Example 2
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the concentration of t-butylbenzene was changed to 3% by mass. A battery was prepared in the same manner as in Example 1 except that this non-aqueous electrolyte was used. Produced.

Example 3
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of t-amylbenzene was changed to 2% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 4
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of t-amylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 5
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of 1,4-di-t-butylbenzene was changed to 2% by mass in place of t-butylbenzene. A battery was fabricated in the same manner as in Example 1 except that it was used.

Example 6
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of 1,4-di-t-butylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was fabricated in the same manner as in Example 1 except that it was used.

Example 7
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the biphenyl concentration was changed to 0.1% by mass. A battery was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. did.

Example 8
A nonaqueous electrolyte was prepared in the same manner as in Example 7 except that the concentration of t-butylbenzene was changed to 3% by mass. A battery was prepared in the same manner as in Example 1 except that this nonaqueous electrolyte was used. Produced.

Example 9
A nonaqueous electrolytic solution was prepared in the same manner as in Example 7 except that the concentration of t-amylbenzene was changed to 2% by mass in place of t-butylbenzene, and this nonaqueous electrolytic solution was prepared and used. Produced a battery in the same manner as in Example 1.

Example 10
A non-aqueous electrolyte was prepared in the same manner as in Example 7 except that the concentration of t-amylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 11
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the biphenyl concentration was changed to 0.5% by mass. A battery was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. did.

Example 12
A non-aqueous electrolyte was prepared in the same manner as in Example 11 except that the concentration of t-butylbenzene was changed to 3% by mass. A battery was prepared in the same manner as in Example 1 except that this non-aqueous electrolyte was used. Produced.

Example 13
A nonaqueous electrolytic solution was prepared in the same manner as in Example 11 except that the concentration of t-amylbenzene was changed to 2% by mass in place of t-butylbenzene, and this nonaqueous electrolytic solution was prepared and used. Produced a battery in the same manner as in Example 1.

Example 14
A nonaqueous electrolytic solution was prepared in the same manner as in Example 11 except that the concentration of t-amylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 15
A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that the concentration of fluorobenzene was changed to 1% by mass. A battery was produced in the same manner as in Example 1 except that this nonaqueous electrolyte was used. .

Example 16
A non-aqueous electrolyte was prepared in the same manner as in Example 15 except that the concentration of t-butylbenzene was changed to 3% by mass. The battery was the same as in Example 1 except that this non-aqueous electrolyte was used. Was made.

Example 17
A nonaqueous electrolytic solution was prepared in the same manner as in Example 15 except that the concentration of t-amylbenzene was changed to 2% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 18
A nonaqueous electrolytic solution was prepared in the same manner as in Example 15 except that the concentration of t-amylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 19
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of fluorobenzene was changed to 5% by mass. A battery was produced in the same manner as in Example 1 except that this nonaqueous electrolytic solution was used. .

Example 20
A non-aqueous electrolyte was prepared in the same manner as in Example 19 except that the concentration of t-butylbenzene was changed to 3% by mass. A battery was prepared in the same manner as in Example 1 except that this non-aqueous electrolyte was used. Produced.

Example 21
A nonaqueous electrolytic solution was prepared in the same manner as in Example 19 except that the concentration of t-amylbenzene was changed to 2% by mass in place of t-butylbenzene. The nonaqueous electrolytic solution was used except that this nonaqueous electrolytic solution was used. A battery was prepared in the same manner as in Example 1.

Example 22
A nonaqueous electrolytic solution was prepared in the same manner as in Example 19 except that the concentration of t-amylbenzene was changed to 3% by mass in place of t-butylbenzene. A battery was prepared in the same manner as in Example 1.

Example 23
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the biphenyl concentration was changed to 0.6% by mass. A battery was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. did.

Example 24
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of fluorobenzene was changed to 7% by mass. A battery was produced in the same manner as in Example 1 except that this nonaqueous electrolytic solution was used. .

Example 25
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the concentration of t-butylbenzene was changed to 5% by mass. A battery was prepared in the same manner as in Example 1 except that this non-aqueous electrolyte was used. Produced.

Comparative Example 1
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the concentration of cyclohexylbenzene was changed to 4% by mass. A battery was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. .

Comparative Example 2
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that biphenyl was not added. A battery was fabricated in the same manner as in Example 1 except that this non-aqueous electrolyte was used.

Comparative Example 3
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that no fluorobenzene was added. A battery was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used.

Comparative Example 4
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that t-butylbenzene was not added, and a battery was fabricated in the same manner as in Example 1 except that this nonaqueous electrolytic solution was used.

  The following evaluation was performed about the nonaqueous secondary battery of Examples 1-25 and Comparative Examples 1-4. The results are shown in Table 2 and Table 3.

<Overcharge test>
The non-aqueous secondary batteries of Examples 1 to 25 and Comparative Examples 1 to 4 were each overcharged at 12 V with a current corresponding to 1 C, and examined for the presence or absence of ignition / rupture.

<Swelling evaluation during continuous charging>
For the non-aqueous secondary batteries of Examples 1 to 25 and Comparative Examples 1 to 4, each battery was measured for 168 hours at a current corresponding to 1 C and a voltage of 4.3 V, and then the thickness of the battery was measured. The increase rate from the initial thickness [(thickness after storage−initial thickness) / (initial thickness) × 100 (%)] was examined.

<Load characteristics>
For the batteries of Examples 1 to 25 and Comparative Examples 1 to 4, when the charge / discharge current is indicated by C, 840 mA is set to 1C, a 1C current limiting circuit is provided, and the initial charge is performed at a constant voltage of 4.2V, Then, it discharged to 3.0V at 0.2C. Subsequently, the battery was charged with a current corresponding to 1 C until the battery voltage reached 4.2 V, and then discharged with a current equivalent to 2 C until it reached 3.0 V, and the discharge capacity was determined. The load characteristics were evaluated from the ratio between the discharge capacity at 2C and the discharge capacity at 0.2C.

<Charge / discharge cycle characteristics>
For the batteries of Examples 1 to 25 and Comparative Examples 1 to 4, charging was performed at a current corresponding to 1C until the battery voltage reached 4.2V, and then the conditions for discharging until 3.0V at a current corresponding to 1C were satisfied. The discharge was carried out for 500 cycles, and the discharge capacity at the 500th cycle divided by the discharge capacity at the first cycle multiplied by 100 was evaluated as charge / discharge cycle characteristics (%).

  As can be seen from Table 2 and Table 3, in the non-aqueous secondary batteries of Examples 1 to 25, there was no ignition during the overcharge test, excellent overcharge resistance performance, and continuous charging The change in thickness is very small before and after, and the occurrence of swelling is suppressed. Furthermore, in the non-aqueous secondary batteries of Examples 1 to 25, load characteristics and charge / discharge cycle characteristics are also good. Moreover, in the non-aqueous secondary battery of Examples 1-22 manufactured using the non-aqueous electrolyte with a more suitable composition, the effect of suppressing battery swelling due to continuous charging and battery characteristics (load characteristics, charge / discharge cycle characteristics) Is particularly good.

  On the other hand, the non-aqueous secondary batteries of Comparative Examples 1 to 4 have problems such that ignition occurs during overcharge or the battery swells after continuous charge is large.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically an example of the non-aqueous secondary battery of this invention, (a) is the top view, (b) is the fragmentary longitudinal cross-sectional view. It is a perspective view of the non-aqueous secondary battery shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Insulator 6 Electrode laminated body 7 Positive electrode lead body 8 Negative electrode lead body 9 Sealing cover plate 10 Insulation packing 11 Terminal 12 Insulator 13 Lead plate 14 Electrolyte injection port 15 Safety valve

Claims (2)

A non-aqueous secondary battery having a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The non-aqueous secondary battery, wherein the non-aqueous electrolyte contains 3% by mass or less of cyclohexylbenzene and biphenyl, fluorobenzene, and t-alkylbenzene.   A non-aqueous electrolyte containing 3% by mass or less of cyclohexylbenzene, 0.1 to 0.5% by mass of biphenyl, 1% by mass or more of fluorobenzene, and 1% by mass or more of t-alkylbenzene is used. The nonaqueous secondary battery according to claim 1.

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