JP6839380B2 - Manufacturing method of non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a method for producing a non-aqueous electrolyte solution, a non-aqueous electrolyte solution secondary battery, and a non-aqueous electrolyte solution secondary battery.

Non-aqueous electrolyte secondary batteries typified by lithium secondary batteries have been used as power sources for mobile devices such as laptop computers and mobile phones, but in recent years, electric vehicles (EVs), hybrid electric vehicles (HEVs), and plugs have been used. It is also used as a power source for automobiles such as in-hybrid vehicles (PHEV).

A non-aqueous electrolyte secondary battery generally includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and a non-aqueous electrolytic solution containing a non-aqueous solvent and a lithium salt.
Non-aqueous electrolyte solution The positive electrode active material that constitutes the secondary battery is a lithium-containing transition metal oxide, the negative electrode active material is a carbonaceous material such as graphite, and the non-aqueous electrolyte solution is a cyclic such as ethylene carbonate. It is widely known that an electrolyte such as _{lithium hexafluorophosphate (LiPF 6} ) is dissolved in a non-aqueous solvent containing a chain carbonate such as carbonate and diethyl carbonate as a main component.

On the other hand, since high energy density is required for a power source for automobiles, _{LiNi 1/2} Mn _1/2 O _{2 having an α-NaFeO type 2} crystal structure is required as a positive electrode active material that can be used at a higher voltage. , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , Li _{1 + α} Me _1-α O ₂ (α> 0, Me includes Mn and one or more transition metals of Co and Ni), etc. and, the development of the lithium-transition metal composite oxide such as _LiNi 1/2 _Mn 3/2 _{O 4} having a spinel type crystal structure has been carried out (see Patent Document 4, paragraph [0037]).

Further, non-aqueous electrolytic solutions containing fluoroethylene carbonate as a solvent are also known for various purposes (see Patent Documents 1 to 4).

Patent Document 1 uses "propylene carbonate and 4-fluoroethylene carbonate" as an electrolytic solution for the purpose of "providing a battery capable of improving battery characteristics such as cycle characteristics" (paragraph [0005]). The invention according to claim 1 is described, wherein the content of 4-fluoroethylene carbonate is 0.0027 g or more and 0.056 g or less with respect to 1 g of the carbon material. There is.
Further, in the battery described as an example, the positive electrode active material is LiCoO ₂ , the negative electrode active material is graphite (paragraphs [0040], [0041]), and the electrolytic solutions are propylene carbonate (PC) and ethylene carbonate (EC). _{) Is contained in a volume ratio of 70:30 to 30:70, and LiPF 6} is dissolved in a mixed solvent containing 4-fluoroethylene carbonate (FEC) in a mixed solvent containing 0.0027 to 0.056 g with respect to 1 g of the carbon material of the negative electrode. (Paragraphs [0043] to [0059]).
Then, "The charge / discharge test was performed in an environment of -10 ° C, and charging was performed with a constant current of 1200 mA until the battery voltage reached 4.2 V, and then the total charge time was 4 at a constant voltage of 4.2 V. It was carried out until the time was reached, and the discharge was carried out until the battery voltage reached 2.75 V at a constant current of 1200 mA. The discharge capacity retention rate was the discharge capacity of the 100th cycle with respect to the discharge capacity of the first cycle (initial discharge capacity). That is, it was calculated as (100th cycle discharge capacity / initial discharge capacity) × 100. ”(Paragraph [0046]) Therefore, in Patent Document 1, the charge / discharge cycle performance of the battery is this. It is evaluated based on the discharge capacity retention rate.

Patent Document 2 provides "a non-aqueous electrolyte for a secondary battery and a non-aqueous electrolyte secondary battery that can remarkably suppress gas generation even when stored at a high temperature or when charging and discharging are repeated. (Paragraph [0009]), or "Providing a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery for a secondary battery capable of suppressing a decrease in charge / discharge capacity and rate characteristics at low temperature due to gas generation" (paragraph [0010]. ]) The purpose is to "contain a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent, and the non-aqueous solvent contains a fluorocyclic carbonate, a propylene carbonate, and a diethyl carbonate. includes, for the entire the nonaqueous solvent, the content of the fluorinated cyclic carbonate W _FCC 2 to 12 wt%, the content W _PC 40 to 70 wt% of the propylene carbonate, the content of the diethyl carbonate An invention _{relating to "a non-aqueous electrolyte for a secondary battery having a W DEC} of 20 to 50% by mass" (claim 1) is described.
Further, as an example, the negative electrode active material is graphite and the positive electrode active material is LiNi _0.80 Co _0.15 Al _0.05 O ₂ (paragraphs [0072] and [0073]), as an evaluation of the cycle capacity retention rate. , "The charge / discharge cycle was repeated at 45 ° C. In the charge / discharge cycle, in the charge / discharge cycle, constant current charging was performed with a current of 600 mA until the charge voltage became 4.2 V, and then at a voltage of 4.2 V, the current was 43 mA. The constant voltage charge was performed until the voltage became constant. The pause time after charging was set to 10 minutes. On the other hand, in the discharge process, the constant current discharge was performed with a current of 850 mA until the discharge voltage became 2.5 V. The rest time after discharge was 10 minutes. The discharge capacity of the third cycle was set to 100%, and the ratio of the discharge capacity after 500 cycles was expressed as a percentage based on this discharge capacity, and this was expressed as a cycle. The capacity retention rate was used. ”(Paragraph [0077]).

Patent Document 3 aims at "providing a battery capable of obtaining a high energy density and excellent cycle characteristics" (paragraph [0008]), and "provides an electrolytic solution together with a positive electrode and a negative electrode." The negative electrode includes a carbon material and has a negative electrode active material layer having a thickness of 70 μm or more and 120 μm or less per side, and the electrolytic solution is an annular battery represented by the following formula (1). The mass content ratio (B mass%) of the halogenated cyclic carbonate (B mass%) contained in the cyclic carbonate (A mass%) represented by the above formula (1) containing a solvent containing a carbonate in an amount of 15% by mass or more and 30% by mass or less. A battery having a B / A) of 0.5 to 1.0.

[In formula (1), R _{1 to} R ₄ independently represent hydrogen, halogen, alkyl group or alkyl halide group. ] ”(Claim 1),“ The battery according to claim 1, wherein the halogenated cyclic carbonate is a fluoroethylene carbonate. ”(Claim 2),“ The cyclic carbonate represented by the formula (1) contains propylene carbonate. The battery according to claim 1, wherein the cyclic carbonate represented by the formula (1) contains ethylene carbonate. ”(Claim 4) (claim. The invention according to item 5) is described.

In the examples, the positive electrode active material is LiCoO ₂ and the negative electrode active material is a graphite battery (paragraphs [0065] and [0068]). Six as an electrolyte salt in a solvent in which propylene (PC), fluoroethylene carbonate (FEC) and / or chloroethylene carbonate (ClEC), diethyl carbonate (DEC) as a chain carbonate, and methyl ethyl carbonate (MEC) are mixed. A solution prepared by dissolving lithium fluoride phosphate at a ratio of 1 mol / kg was used. The content of the cyclic carbonate represented by the formula (1) in the solvent was 20% by mass, and the mixture was represented by the formula (1). The content of the halogenated cyclic carbonate (FEC, ClEC) in the cyclic carbonate was changed. ”(Paragraph [0071]) (paragraph [0071]).
Then, regarding the evaluation of the cycle characteristics, "Charging is performed at a constant current of 1C until the battery voltage reaches 4.2V, and then at a constant voltage of 4.2V until the total charging time reaches 4 hours. , Discharge was performed with a constant current of 1C until the battery voltage reached 3.0V. 1C is the current value at which the theoretical capacity can be completely discharged in 1 hour. The battery capacity is the initial discharge capacity (1st cycle). The discharge capacity is defined as the ratio of the discharge capacity of the 100th cycle to the initial discharge capacity (discharge capacity of the first cycle), that is, (discharge capacity of the 100th cycle / discharge capacity of the first cycle) × 100 ( %). ”(Paragraph [0072]).

Patent Document 4 states, "By optimizing the electrolyte composition of a non-aqueous electrolyte secondary battery having a lithium-nickel-manganese composite oxide on the positive electrode, the charge / discharge cycle performance of a high-voltage non-aqueous electrolyte secondary battery can be improved. For the purpose of "improving" (paragraph [0013]), "the positive electrode active material is a general formula Li _{x N y} Mn _2-y O _4-δ (provided that 0 <x <1.1, 0.45 <y <. In a non-aqueous electrolyte secondary battery which is a lithium-nickel-manganese composite oxide represented by 0.55, 0 ≦ δ <0.4), the non-aqueous electrolyte contains a cyclic carbonate and a chain carbonate, and the cyclic carbonate is contained. An invention is described for a "non-aqueous electrolyte battery" (claim 1), wherein at least one of a carbonate or a chain carbonate contains an element of fluorine.
Then, it is described that the charge / discharge cycle performance is evaluated by the charge / discharge cycle test at 25 ° C. (paragraph [0042]), and as an example including both FEC and PC, the solvent composition is FEC: PC in volume ratio. : DEC = 2: 2: 6 (paragraph [0055] [Table 3] Example 14), 1: 4: 5 electrolyte (paragraph [0059] [Table 5] Example 25) is described.

Patent Document 5 includes "a positive electrode, a negative electrode, a boric acid, and a cyclic sulfonic acid compound" for the purpose of "significantly improving the charge / discharge cycle performance of a non-aqueous electrolyte battery" (paragraph [0009]). A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte. ”(Claim 1), and the non-aqueous electrolyte secondary battery according to any one of claims 1 to 4 is 4.4 V (vs. Li /). A method of using a non-aqueous electrolyte secondary battery that charges at a positive electrode potential of ^{Li +) or higher is described.}
Then, as a specific example of the positive electrode active material having a positive electrode potential of 4.4 V (vs. Li ^/ _{Li +), "LiCo 1/3} Ni _1/3 Mn _1/3 O ₂ " is described in paragraph [0051]. As the electrolyte solvent, a solvent obtained by adding boric acid and diglycol sulfate to a mixed solvent of EC and ethyl methyl carbonate (hereinafter, also abbreviated as "EMC") is described.

Japanese Unexamined Patent Publication No. 2006-4878 WO2012 / 032700 Japanese Unexamined Patent Publication No. 2009-164053 Japanese Unexamined Patent Publication No. 2005-78820 Japanese Unexamined Patent Publication No. 2015-22901

In all of the inventions described in Patent Documents 1 to 3 above, the non-aqueous electrolytic solution contains fluoroethylene carbonate (hereinafter, also abbreviated as "FEC"), and the charge / discharge cycle performance is improved and gas is generated. The purpose is to suppress the decrease in rate characteristics at low temperatures.
However, looking at the solvent composition of the non-aqueous electrolytic solution, the non-aqueous electrolytic solution in the invention described in Patent Document 1 contains 30% by volume or more of propylene carbonate (hereinafter, also referred to as “PC” for short) and has a chain. It is unknown whether it contains a state carbonate.
The solvent of the non-aqueous electrolytic solution in the invention described in Patent Document 2 contains 40% by mass or more of PC, and the content of diethyl carbonate, which is a chain carbonate, is 50% by mass or less.
In Patent Document 3, the halogenated cyclic carbonate (FEC) is 50% by mass or more, that is, the non-halogenated cyclic carbonate (EC,) in the range of patent claims, out of 15 to 30% by mass of the cyclic carbonate. A solvent for a non-aqueous electrolyte solution containing 15% by mass or less of PC) is described, but specifically, only a solvent containing 3.0% by mass or less of PC is disclosed.
Further, in each of the inventions, the charge / discharge cycle test is performed with the battery voltage at the charging end set to 4.2 V. Therefore, in the description of Patent Documents 1 to 3, for example, the positive electrode potential is 4.4 V (vs. Li ^{/ Li +).} ) It does not provide any knowledge about the charge / discharge cycle performance in the high temperature range or low temperature range of the non-aqueous electrolyte secondary battery used under the above high voltage.

Patent Documents 4 and 5 describe inventions of a non-aqueous electrolyte solvent that contributes to the improvement of charge / discharge cycle performance in a non-aqueous electrolyte secondary battery having a positive electrode potential of 4.4 V or more. Further, Patent Document 4 describes a solvent containing FEC, PC, and a chain carbonate. This PC is a component that is treated in the same manner as EC as a cyclic carbonate, and is a solvent that does not contain EC. , PC containing 20% by volume or 40% by volume is only shown. The solvent described in Patent Document 5 contains EC and EMC as main solvents, and does not include FEC or PC.
Further, since Patent Documents 4 and 5 do not describe the charge / discharge cycle performance evaluated by the charge / discharge cycle test at high temperature or low temperature, the battery has excellent charge / discharge cycle performance from the high temperature range to the low temperature range. Nothing is shown about the solvent composition for this.

An object of the present invention is to provide a non-aqueous electrolytic solution secondary battery having excellent charge / discharge cycle performance from a high temperature range to a low temperature range by using a non-aqueous electrolytic solution having an improved solvent composition.

In the present invention, the following means are adopted in order to solve the above problems.
(1) A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt, and the non-aqueous solvent is a propylene carbonate. (PC) is contained in an amount of 4 to 15% by volume, fluoroethylene carbonate (FEC) is contained in an amount of 3 to 10% by volume, chain carbonate is contained in an amount of 75 to 93% by volume, and the positive electrode potential is 4.4 V (vs. Li ^/ Li +) or more. The non-aqueous electrolyte secondary battery (however, the non-aqueous electrolyte secondary battery corresponding to the following (a) and (b) is excluded.
(A) The positive electrode contains a lithium transition metal composite oxide having a rare earth compound attached to the surface as a positive electrode active material, and the non-aqueous electrolytic solution has lithium tetrafluoroborate and an oxalate complex as anions. Non-aqueous electrolyte secondary battery containing a lithium salt or a lithium salt having a PO bond and a PF bond in the molecule or a lithium salt having a BO bond and a BF bond in the molecule.
(B) The non-aqueous electrolyte solution is a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), and fluorinated represented by the following general formula (3). Non-aqueous electrolyte secondary battery containing chain carbonate and containing more than 15% by volume of cyclic carbonate represented by the general formula (1) in a non-aqueous solvent.
(In the general formula (1), R ₁ represents hydrogen or a hydrocarbon group, which may be the same or different from each other.)
(In the general formula (2), R ₂ represents a hydrocarbon group which may have hydrogen, fluorine, or a substituent, and may be the same or different from each other.)
(In the general formula (3), R ₃ may have a substituent, fluorine containing at least one hydrocarbon group, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ R ₄ may be different and the same.)).
(2) A method for manufacturing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte having a positive electrode potential of 4.4 V (vs. Li ^{/ Li +) or more, which comprises a non-aqueous solvent.} A non-aqueous electrolyte solution containing an electrolyte salt, wherein the non-aqueous solvent contains 4 to 15% by volume of propylene carbonate (PC), 3 to 10% by volume of fluoroethylene carbonate (FEC), and 75 to 93% by volume of chain carbonate. (However, the method for producing a non-aqueous electrolyte secondary battery corresponding to the following (a) and (b) is excluded.
(A) The positive electrode contains a lithium transition metal composite oxide having a rare earth compound attached to the surface as a positive electrode active material, and the non-aqueous electrolyte solution uses lithium tetrafluoroborate and an oxalate complex as anions. A non-aqueous electrolyte secondary battery containing a lithium salt or a lithium salt having a PO bond and a PF bond in the molecule or a lithium salt having a BO bond and a BF bond in the molecule.
(B) The non-aqueous electrolyte solution is a cyclic carbonate represented by the general formula (1), a fluorinated cyclic carbonate represented by the general formula (2), and fluorination represented by the general formula (3). A non-aqueous electrolytic solution secondary battery containing a chain carbonate and containing a cyclic carbonate represented by the general formula (1) in a non-aqueous solvent in an amount of more than 15% by volume ).

By using the non-aqueous electrolytic solution of the present invention, it is possible to provide a non-aqueous electrolytic solution secondary battery having excellent charge / discharge cycle performance from a high temperature range to a low temperature range.

External perspective view showing an embodiment of a non-aqueous electrolyte secondary battery according to the present invention. Schematic diagram showing a power storage device including a plurality of non-aqueous electrolyte secondary batteries according to the present invention.

FIG. 1 shows an external perspective view of a rectangular non-aqueous electrolytic solution secondary battery 1 which is an embodiment of a non-aqueous electrolytic solution secondary battery including the non-aqueous electrolytic solution according to the present invention. The figure is a perspective view of the inside of the battery container 3. In the non-aqueous electrolyte secondary battery 1 shown in FIG. 1, the electrode group 2 is housed in the battery container 3. The electrode group 2 is formed by winding a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material through a separator. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4', and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5'.

<Non-aqueous electrolyte>
Here, the non-aqueous electrolyte solution held in the separator contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, and in the present invention, the non-aqueous solvent is polypropylene carbonate (PC). It is characterized by containing 4 to 15% by volume of fluoroethylene carbonate (FEC), 3 to 10% by volume of fluoroethylene carbonate (FEC), and 75 to 93% by volume of chain carbonate.

FEC has high oxidation resistance and can improve charge / discharge cycle performance, but reducing the content can reduce the increase in battery thickness due to gas generation.

Since PC has _{low reactivity with an electrolyte salt such as LiPF 6} , by containing it in the non-aqueous solvent, even if the FEC is reduced, the side reaction with the active material can be suppressed and the melting point is high. It is presumed that the low temperature makes it excellent in low temperature performance.
Even with the same cyclic carbonate, EC is preferably not contained in an amount of a certain amount or more in order to suppress side reactions with the active material and the electrolyte salt. The content ratio of EC in the non-aqueous solvent is preferably 3% by volume or less, more preferably 2% by volume or less, further preferably 1% by volume or less, and most preferably no EC.

It is particularly preferable that the content of PC is 15% by volume or less when this non-aqueous electrolytic solution is applied to a secondary battery in which the negative electrode contains graphite. Graphite is a typical negative electrode material that is preferable from the viewpoint of safety and discharge capacity, but there is a problem that the charge / discharge cycle performance deteriorates when there are too many PCs in the non-aqueous electrolytic solution. In the present invention, it is preferable to limit the content of PC to 15% by volume or less of the solvent because the above-mentioned problems can be solved.

The chain carbonate in the present invention has the effect of lowering the viscosity by mixing with FEC or PC having a high dielectric constant. As the chain carbonate, known ones such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and diphenyl carbonate can be used.

In addition to PC, FEC, and chain carbonate, the non-aqueous solvent includes cyclic carboxylic acid esters such as γ-butyrolactone, γ-valerolactone, and propiolactone, tetrahydrofuran or its derivatives, 1,3-dioxane, and dimethoxyethane. , Diethoxyethane, methoxyethoxyethane, ethers such as methyl diglyme, nitriles such as acetonitrile and benzonitrile, dioxalane or a derivative thereof, etc. alone or a mixture of two or more thereof are contained in a solvent in an amount of less than 10% by volume. You may be. In order not to impair the effects of the present invention, the solvent is preferably less than 5% by volume, more preferably less than 2% by volume.

The non-aqueous solvent preferably contains a film-forming agent that suppresses the reaction between the electrolytic solution and the electrode.
Examples of the film-forming agent include propene sultone (PRS), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, and 4,4'-bis (2,2-dioxo-1,3). 2-Dioxathiolane or the like is preferable, and it is preferably contained in an amount of 0.1 to 10% by mass with respect to 100 parts by weight of the solvent containing PC, FEC, and chain carbonate.

The electrolyte salt contained in the non-aqueous electrolyte solution of the present invention is not limited, and an electrolyte salt generally used for a non-aqueous electrolyte secondary battery can be used. For example, _{lithium (Li such as LiClO 4} , LiBF ₄ , _{LiAsF 6} , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN, etc. ), Inorganic ionic salt containing one of sodium (Na) or potassium (K), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO) ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H) ₅ ) ₄ NCLO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NCLo ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-malate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phthate, lithium stearylsulfonate, lithium octylsulfonate, lithium dodecylbenzenesulfonate, and other organic ionic salts Etc., and these ionic compounds can be used alone or in combination of two or more.

The concentration of the electrolyte salt in the non-aqueous electrolyte solution is preferably 0.1 mol / l to 5.0 mol / l in order to surely obtain a non-aqueous electrolyte solution secondary battery having excellent high rate discharge characteristics. More preferably, it is 0 mol / l to 2.0 mol / l.

<Positive electrode active material>
The positive electrode active material used for the positive electrode constituting the non-aqueous electrolyte secondary battery of the present invention is electrochemically capable of inserting and removing lithium ions, and has a positive electrode potential of 4.4 V (vs. Li ^{/ Li +).} ) The above is preferable, and lithium transition metal composite oxides, polyanionic compounds, etc., which are generally used as the positive electrode active material of the non-aqueous electrolyte secondary battery, can be used. Examples of the lithium transition metal composite oxide include lithium nickel manganese composite oxide and lithium nickel cobalt manganese composite oxide. The lithium-nickel-manganese composite oxide, for _example, LiNi _{0.5 Mn} 1.5 _Li x of _{O 4} or the like _{Ni y Mn 2-y O 4} -δ (0 <x <1.1,0.45 <y < 0.55, 0 ≦ δ <0.4), _{LiMeO 2} (Me is a transition metal containing Ni and Mn) such as _{LiNi 1/2} Mn _1/2 O _{2 , or Li 1.11} Ni _0.29 Mn. _{As Li 1 + α} Me _1-α O ₂ (0 <α, Me is a transition metal containing Ni and Mn) such as 0.60 O ₂ (Li / Me = 1.25), as a lithium nickel cobalt manganese composite oxide, For example, LiMeO ₂ (Me is a transition metal containing Ni, Co and Mn) _{such as LiNi 1/3} Co _1/3 Mn _1/3 O _{2 , or Li 1.09} Co _0.11 Ni _0.18 Mn _{0. 62} O ₂ (Li / Me = 1.2), Li _1.11 Co _0.11 Ni _0.18 Mn _0.60 O ₂ (Li / Me = 1.25), etc. Li _{1 + α} Me _1-α O ₂ (0 <α, Me is a transition metal containing Ni, Co and Mn) can be used. As the polyanion compound, for example, LiNiPO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ F, Li ₂ MnSiO _{4 and the} like can be used.

<Negative electrode active material>
The negative electrode active material used for the negative electrode constituting the non-aqueous electrolyte secondary battery of the present invention is capable of electrochemically inserting and removing lithium ions, and has a positive electrode potential of 4.4 V (vs. Li /). It is preferable that it can be used at a high voltage in combination with a positive electrode having Li ⁺ ) or higher, and a carbonaceous material generally used as a negative electrode active material of a non-aqueous electrolyte secondary battery, a metal oxide such as tin oxide or silicon oxide, A metal composite oxide, a lithium alloy such as lithium alone or a lithium-aluminum alloy, a metal capable of forming an alloy with lithium such as Sn or Si, or the like can be used. Examples of the carbonaceous material include natural graphite, artificial graphite, cokes, non-graphitizable carbon, low-temperature calcinable easily graphitizable carbon, fullerenes, carbon nanotubes, carbon black, activated carbon and the like. These may be used alone or in any combination and ratio of two or more. Of these, carbonaceous materials are preferable from the viewpoint of safety, and graphite is particularly preferable.

Combining a graphite negative electrode with a non-aqueous electrolytic solution containing a PC causes a problem that the PC is decomposed on the surface of the negative electrode and the charge / discharge cycle performance is deteriorated. However, in the present invention, the above problems can be solved by limiting the content of PC to 15% by volume or less and using FEC in combination.

<Positive electrode / Negative electrode>
The positive electrode active material and the negative electrode active material, which are the main constituents of the positive electrode and the negative electrode, are preferably powders having an average particle size of 100 μm or less. In particular, the powder of the positive electrode active material is preferably 10 μm or less for the purpose of improving the high output characteristics of the non-aqueous electrolyte battery. A crusher or a classifier is used to obtain the powder in a predetermined shape. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, a sieve, or the like is used. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. The classification method is not particularly limited, and a sieve, a wind power classifier, or the like is used as needed for both dry and wet types.

In addition to the active material which is the main constituent component, the positive electrode and the negative electrode may contain a conductive agent, a binder, a thickener, a filler and the like as other constituent components.

The conductive agent is not limited as long as it is an electronically conductive material that does not adversely affect the battery performance, but is usually natural graphite (scaly graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, etc. Conductive materials such as Ketjen black, carbon whiskers, carbon fibers, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fibers, conductive ceramic materials, etc. can be included as one kind or a mixture thereof. ..

Among these, acetylene black is preferable as the conductive agent from the viewpoint of electron conductivity and coatability. The amount of the conductive agent added is preferably 0.1% by weight to 50% by weight, particularly preferably 0.5% by weight to 30% by weight, based on the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black pulverized into ultrafine particles of 0.1 to 0.5 μm because the required carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, it is possible to mix powder mixers such as V-type mixers, S-type mixers, scouring machines, ball mills, and planetary ball mills in a dry or wet manner.

Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethylene and polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM and styrene butadiene. A polymer having rubber elasticity such as rubber (SBR) and fluororubber can be used as one kind or a mixture of two or more kinds. The amount of the binder added is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.

As the filler, a material that does not adversely affect the battery performance can be used. Usually, olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, carbon and the like are used. The amount of the filler added is preferably 30% by weight or less with respect to the total weight of the positive electrode or the negative electrode.

For the positive electrode and the negative electrode, the main components (positive electrode active material for the positive electrode, negative electrode active material for the negative electrode) and other materials are kneaded to form a mixture, which is mixed with an organic solvent such as N-methylpyrrolidone or toluene or water. After that, the obtained mixed solution is coated on a current collector described in detail below, or crimped and heat-treated at a temperature of about 50 ° C. to 250 ° C. for about 2 hours to be suitably produced. To. Regarding the coating method, for example, it is preferable to apply the coating to an arbitrary thickness and an arbitrary shape by using a means such as a roller coating such as an applicator roll, a screen coating, a doctor blade method, a spin coating, or a bar coater. It is not limited.

The materials of the positive electrode current collector and the negative electrode current collector are not particularly limited, and known materials can be used.
Examples of the positive electrode current collector include metal materials such as aluminum, stainless steel, nickel plating, titanium and tantalum, and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, especially aluminum, are preferable.
Examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is preferable in terms of ease of processing and cost.

<Separator>
As the separator, it is preferable to use a microporous film, a non-woven fabric, or the like alone or in combination. Examples of the material constituting the separator include polyolefin resins typified by polyethylene and polypropylene, polyester resins typified by polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene copolymers. , Vinylidene Fluoride-Perfluorovinyl Ether Copolymer, Vinylidene Fluoride-Tetrafluoroethylene Copolymer, Vinylidene Fluoride-Trifluoroethylene Copolymer, Vinylidene Fluoride-Fluoroethylene Copolymer, Vinylidene Fluoride-Hexafluoro Acerene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, foot Examples thereof include vinylidene compound-ethylene-tetrafluoroethylene copolymer and the like. Of these, a microporous membrane containing a polyolefin resin typified by polyethylene, polypropylene or the like as a main component is preferable.

<Non-aqueous electrolyte secondary battery and power storage device>
The non-aqueous electrolyte secondary battery according to the present invention has terminals, an insulating plate, a battery case, and the like as other components of the battery, but those conventionally used may be used as they are.
The shape of the non-aqueous electrolyte secondary battery according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), and a flat battery. The present invention can also be realized as a power storage device including a plurality of the above-mentioned non-aqueous electrolyte secondary batteries. An embodiment of the power storage device is shown in FIG. In FIG. 2, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of non-aqueous electrolyte secondary batteries 1. The power storage device 30 can be mounted as a power source for automobiles such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid vehicles (PHEV).

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples as long as the gist of the present invention is not exceeded.

(Example 1)
(Electrolytic solution 1-1 of the present invention)
A non-aqueous electrolyte solution prepared by dissolving _{LiPF 6} as an electrolyte salt at a concentration of 1.2 mol / L in a solvent obtained by mixing PC: FEC: EMC in a volume ratio of 4: 3: 93 and adding 2% by mass of PRS. The electrolytic solution 1 of the present invention was used.

(Comparative electrolytes 1-1 to 1-3)
A non-aqueous electrolytic solution similar to the electrolytic solution 1-1 of the present invention was prepared except that a solvent in which FEC: EMC was mixed at a volume ratio of 7:93 and 3:97, respectively, was used, and a comparative electrolytic solution was prepared. 1-1 and Comparative Electrolyte 1-2.
Further, a non-aqueous electrolytic solution similar to the electrolytic solution 1-1 of the present invention was prepared except that a solvent in which EC was mixed at the same volume ratio was used instead of PC, and used as the comparative electrolytic solution 1-3. ..

<Manufacturing of positive electrode plate>
As the positive electrode active material, a lithium transition metal composite oxide represented by _{LiNi 1/3} Co _1/3 Mn _1/3 O _{2 was used.} Positive electrode by mass ratio Positive electrode containing active material: polyvinylidene fluoride (PVdF): acetylene black (AB) = 93: 4: 3 (solid matter equivalent) and using N-methylpyrrolidone (NMP) as a solvent. A paste was prepared, and the positive electrode paste was applied to both sides of a strip-shaped aluminum foil current collector having a thickness of 15 μm so ^{that the positive electrode active material was contained at 17 mg / cm 2 per unit electrode area.} This was pressed by a roller press to form a positive electrode active material layer, and then dried under reduced pressure at 100 ° C. for 14 hours to remove water in the electrode plate. The positive electrode plate was produced in this way.

<Manufacturing of negative electrode plate>
Graphite was used as the negative electrode active material. A negative electrode paste containing graphite: styrene-butadiene rubber (SBR): carboxymethyl cellulose (CMC) = 97: 2: 1 (in terms of solid content) in terms of mass ratio and using water as a solvent was prepared and 2 (mass). The mixture of (ratio) was applied to both sides of a strip-shaped copper foil current collector having a thickness of 10 μm. This was pressed by a roller press to form a negative electrode active material layer, and then dried under reduced pressure at 100 ° C. for 12 hours to remove water in the electrode plate. The negative electrode plate was produced in this way.

<Assembly process of non-aqueous electrolyte secondary battery>
The positive electrode plate and the negative electrode plate are laminated via a separator made of a polyethylene microporous membrane and wound into a flat shape to prepare an electrode group 2 as shown in FIG. 1 and stored in an aluminum battery container 3. Then, the positive and negative electrodes 4 and 5 were attached. The electrolytic solution 1-1 of the present invention and the comparative electrolytic solutions 1-1 to 1-3 were injected into the battery container 3 and then sealed. In this way, the non-aqueous electrolyte secondary battery was assembled.

<Initial charge / discharge process>
The non-aqueous electrolyte secondary battery assembled as described above was subjected to a two-cycle initial charge / discharge step at a temperature of 25 ° C. All voltage controls were performed with respect to the voltage between the positive and negative terminals. The charging in the first cycle was a constant current constant voltage charge with a current of 0.2 CmA and a voltage of 4.35 V for 8 hours, and the discharge was a constant current discharge with a current of 0.2 CmA and a final voltage of 2.75 V. The charging in the second cycle was a constant current constant voltage charge with a current of 1.0 CmA and a voltage of 4.35 V for 3 hours, and the discharge was a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V. A 10 minute rest period was set after charging and discharging in all cycles. In this way, a non-aqueous electrolyte secondary battery was produced. The initial discharge capacity was 173 mAh / g.

<Charge / discharge cycle test>
A high-temperature charge / discharge cycle test was conducted at a temperature of 45 ° C. on a non-aqueous electrolytic solution secondary battery provided with the electrolytic solution 1-1 of the present invention and comparative electrolytic solutions 1-1 to 1-3 produced as described above. And the transition of the discharge capacity was investigated. All voltage controls were performed with respect to the voltage between the positive and negative terminals. Charging was a constant current constant voltage charge with a current of 1.0 CmA and a voltage of 4.35 V for 3 hours, and discharge was a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V. A 10 minute rest period was set after charging and discharging in all cycles. Here, when graphite is used for the negative electrode, ^{it is known that the value of the positive electrode potential (vs. Li /} Li +) is about 0.1 larger than the value of the voltage between terminals. The results after 500 cycles are shown in Table 1.

From Table 1, the high temperature capacity retention rate is excellent in the case of Example 1-1 using a solvent containing 4% by volume of PC, 3% by volume of FEC, and 93% by volume of EMC. In addition, the increase in battery thickness is also suppressed. In the case of Comparative Examples 1-1 and 1-2 not including the PC, the high temperature capacity retention rate is low. Further, in the case of Comparative Example 1-1, no effect is observed in suppressing the increase in the battery thickness. In the case of Comparative Example 1-3 containing EC instead of PC, the high temperature capacity retention rate is low, and the effect of suppressing the increase in battery thickness is not seen.

(Example 2)
(Electrolytic solution 2-1 and 2-2 of the present invention)
A non-aqueous electrolyte solution prepared by dissolving _{LiPF 6} as an electrolyte salt at a concentration of 1.2 mol / L in a solvent having a volume ratio of PC: FEC: EMC of 5: 5: 90 and 10: 5: 85, respectively. The electrolytic solution 2-1 of the present invention and the electrolytic solution 2-2 of the present invention were used.

(Comparative electrolytes 2-1 and 2-2)
A non-aqueous electrolytic solution similar to the electrolytic solution 2-1 of the present invention is compared with the electrolytic solution 2 except that a solvent having a volume ratio of 0: 5: 95 and 20: 5: 75 is used for PC: FEC: EMC, respectively. It was set to -1, 2-2.

<Charge / discharge cycle test>
A non-aqueous electrolytic solution secondary battery is assembled in the same manner as in Example 1 except that the electrolytic solutions 2-1 and 2-2 of the present invention and the comparative electrolytic solutions 2-1 and 2-2 are used, and the initial charge and discharge are performed. Was performed, and the same high-temperature charge / discharge cycle test as in Example 1 was performed. The results after 200 cycles are shown in Table 2 below.

From Table 2, in the case of a battery in which the solvent having the composition according to the present invention is used as the non-aqueous electrolytic solution, it is effective in maintaining the high temperature capacity and suppressing the increase in the battery thickness. It can be seen that the capacity retention rate is significantly reduced.

(Example 3)
(Electrolytic solution 3-1, 3-2 of the present invention)
Electrolyte solutions having the same solvent composition as the electrolytic solutions 2-1 and 2-2 of the present invention and the types and concentrations of electrolyte salts were prepared and used as the electrolytic solutions 3-1 and 3-2 of the present invention, respectively.

(Comparative electrolyte 3-1)
The comparative electrolytic solution 3-1 was used in the same manner as the electrolytic solutions 3-1 and 3-2 of the present invention except that the volume ratio of PC: FEC: EMC was set to 0: 5: 95.

<Charge / discharge cycle test>
A non-aqueous electrolytic solution secondary battery was assembled in the same manner as in Example 1 except that the electrolytic solution 3-1 and 3-2 of the present invention and the comparative electrolytic solution 3-1 were used, and initial charging and discharging were performed. The same high temperature charge / discharge cycle test as in Example 1 was performed, and the result after 300 cycles was evaluated. Further, a charge / discharge cycle test (low temperature charge / discharge cycle test) similar to that in Example 1 was performed except that the temperature was set to 0 ° C., and the result after 100 cycles was evaluated.
The results are shown in Table 3.

According to Table 3, it can be seen that the non-aqueous electrolyte solution needs to contain PC together with FEC in order to improve the low temperature capacity retention rate while maintaining the high temperature capacity retention rate. Further, it can be seen that the PC has an effect of suppressing an increase in the battery thickness due to a low temperature charge / discharge cycle.

(Example 4)
Using the electrolytic solution 2-1 of the present invention, a non-aqueous electrolytic solution secondary battery was assembled in the same manner as in Example 1, initial charge / discharge was performed, and a high-temperature charge / discharge cycle test was conducted with a charging voltage of 4.3 V and 4. It was carried out at 35V and used as Examples 4-1 and 4-2.
Further, as Comparative Examples 4-1 and 4-2, Examples were used except that Comparative Electrolyte Solution 4-1 containing a solvent having a volume ratio of PC: FEC: EMC: EC of 2:14:74:10 was used. A non-aqueous electrolyte secondary battery was assembled in the same manner as in 4-1 and 4-2, initial charge / discharge was performed, and a high temperature charge / discharge cycle test was performed.
The results after 100 cycles are shown in Table 4.

From Table 4, in the non-aqueous electrolyte secondary battery having a battery voltage of 4.30 V or 4.35 V (positive electrode potential of about 4.4 V (vs. Li ^/ Li +)), the FEC content is the composition of the present invention. It can be seen that when a non-aqueous electrolyte solution exceeding the range and having a PC content below the composition range of the present invention is used, the high temperature capacity retention rate is slightly lowered and the battery thickness is significantly increased. On the other hand, when a non-aqueous electrolyte solution that lowers FEC to the composition range of the present invention and raises PC to the composition range of the present invention is used, the increase in battery thickness is suppressed while maintaining the high temperature capacity retention rate. It can be seen that a more remarkable effect is produced.

(Example 5)
<Manufacturing of positive electrode plate>
As the positive electrode active material, a lithium transition metal composite oxide represented by _{LiNi 1/3} Co _1/3 Mn _1/3 O _{2 was used.} Positive electrode by mass ratio Positive electrode containing active material: polyvinylidene fluoride (PVdF): acetylene black (AB) = 94: 3: 3 (solid matter equivalent) and using N-methylpyrrolidone (NMP) as a solvent. A paste was prepared, and the positive electrode paste was applied to both sides of a strip-shaped aluminum foil current collector having a thickness of 15 μm so ^{that the positive electrode active material was contained at 20 mg / cm 2 per unit electrode area.} This was pressed by a roller press to form a positive electrode active material layer, and then dried under reduced pressure at 100 ° C. for 10 hours to remove water in the electrode plate. The positive electrode plate was produced in this way.

<Manufacturing of negative electrode plate>
Graphite was used as the negative electrode active material. A negative electrode paste containing graphite: styrene-butadiene rubber (SBR): carboxymethyl cellulose (CMC) = 97: 2: 1 (in terms of solid content) in terms of mass ratio and using water as a solvent was prepared and 2 (mass). The mixture of (ratio) was applied to both sides of a strip-shaped copper foil current collector having a thickness of 10 μm. This was pressed by a roller press to form a negative electrode active material layer, and then dried under reduced pressure at 100 ° C. for 12 hours to remove water in the electrode plate. The negative electrode plate was produced in this way.

(Examples 5-1 and 5-2, Comparative Example 5-1)
According to Example 5-1, Example 5-2, and Comparative Example 5-1 in the same manner as in Example 1, using the electrolytic solution 3-1 and 3-2 of the present invention and the comparative electrolytic solution 3-1. A non-aqueous electrolyte secondary battery was produced.
The high temperature charge / discharge cycle performance of these batteries was evaluated by the discharge capacity retention rate after 300 cycles, and the low temperature charge / discharge cycle performance was evaluated by the discharge capacity retention rate after 100 cycles. The results are shown in Table 5.

(Examples 5-3 to 5-5, Comparative Example 5-2)
Performed except using non-aqueous electrolytes in which the PC: FEC: EMC in the solvent is 0:10:90, 5:10:85, 10:10:80, and 15:10:75, respectively, by volume. In the same manner as in Example 5-1, the non-aqueous electrolyte secondary batteries according to Comparative Example 5-2, Example 5-3, Example 5-4, and Example 5-5 were produced, and Example 5-1 The same high-temperature and low-temperature charge / discharge cycle tests as in the above were performed.
The high temperature charge / discharge cycle performance of these batteries was evaluated by the discharge capacity retention rate after 300 cycles, and the low temperature charge / discharge cycle performance was evaluated by the discharge capacity retention rate after 250 cycles. The results are shown in Table 6.

From Tables 5 and 6, in Comparative Examples 5-1 and 5-2 which contain FEC but do not contain PC in the solvent in the non-aqueous electrolyte secondary battery used at a high voltage, the low temperature charge / discharge cycle performance and the low temperature charge / discharge cycle performance and It can be seen that there is no effect in suppressing the increase in battery thickness. On the other hand, according to Examples 5-1 to 5-4, the high temperature charge / discharge cycle performance is maintained or improved by using the non-aqueous electrolytic solution satisfying the solvent composition of the present invention, and the low temperature charge / discharge is performed. It can be seen that the cycle performance is significantly improved. In Example 5-5, where the FEC is 10% by volume and the PC content is 15% by volume, the high temperature capacity retention rate is slightly reduced, but the low temperature capacity retention rate is significantly improved. Therefore, it can be said that the non-aqueous electrolytic solution secondary battery using the non-aqueous electrolytic solution according to the present invention has excellent charge / discharge cycle performance over a wide temperature range.

The non-aqueous electrolyte secondary battery according to the present invention has excellent charge / discharge cycle performance from a high temperature range to a low temperature range, and can suppress an increase in battery thickness. Therefore, an electric vehicle, a hybrid vehicle, and a plug-in hybrid vehicle can be suppressed. It is useful as a power source for automobiles.

1 Non-aqueous electrolyte secondary battery 2 Electrode group 3 Battery container 4 Positive terminal 4'Positive lead 5 Negative terminal 5'Negative lead 20 Power storage unit 30 Power storage device

Claims (2)

A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte.
The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt, and the non-aqueous solvent contains 4 to 15% by volume of propylene carbonate (PC), 3 to 10% by volume of fluoroethylene carbonate (FEC), and a chain carbonate. Containing 75-93% by volume,
The positive electrode potential is 4.4 V (vs. Li ^/ Li +) or higher.
Non-aqueous electrolyte secondary battery (However, non-aqueous electrolyte secondary batteries corresponding to the following (a) and (b) are excluded.
(A) The positive electrode contains a lithium transition metal composite oxide having a rare earth compound attached to the surface as a positive electrode active material, and the non-aqueous electrolytic solution has lithium tetrafluoroborate and an oxalate complex as anions. Non-aqueous electrolyte secondary battery containing a lithium salt or a lithium salt having a PO bond and a PF bond in the molecule or a lithium salt having a BO bond and a BF bond (b) The water electrolyte contains a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain carbonate represented by the following general formula (3). In addition, a non-aqueous electrolyte secondary battery in which a non-aqueous solvent contains more than 15% by volume of the cyclic carbonate represented by the general formula (1).
(In the general formula (1), R ₁ represents hydrogen or a hydrocarbon group, which may be the same or different from each other.)
(In the general formula (2), R ₂ represents a hydrocarbon group which may have hydrogen, fluorine, or a substituent, and may be the same or different from each other.)
(In the general formula (3), R ₃ may have a substituent, fluorine containing at least one hydrocarbon group, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ R ₄ may be different and the same.)). A method for manufacturing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte having a positive electrode potential of 4.4 V (vs. Li ^{/ Li +) or more.}
It contains a non-aqueous solvent and an electrolyte salt, and the non-aqueous solvent contains 4 to 15% by volume of propylene carbonate (PC), 3 to 10% by volume of fluoroethylene carbonate (FEC), and 75 to 93% by volume of chain carbonate. A method for producing a non-aqueous electrolyte secondary battery, which comprises using a non-aqueous electrolyte solution (however, a method for producing a non-aqueous electrolyte secondary battery corresponding to the following (a) and (b) is excluded.
(A) The positive electrode contains a lithium transition metal composite oxide having a rare earth compound attached to the surface as a positive electrode active material, and the non-aqueous electrolyte solution uses lithium tetrafluoroborate and an oxalate complex as anions. Non-aqueous electrolyte secondary battery containing a lithium salt or a lithium salt having a PO bond and a PF bond in the molecule or a lithium salt having a BO bond and a BF bond (b) The non-water cyclic carbonates electrolyte is represented by the following general formula (1), containing a fluorinated chain carbonate represented by the fluorinated cyclic carbonate represented by the following general formula (2), and the following general formula (3) In addition, a non-aqueous electrolyte secondary battery containing more than 15% by volume of the cyclic carbonate represented by the general formula (1) in the non-aqueous solvent.
(In the general formula (1), R ₁ represents hydrogen or a hydrocarbon group, which may be the same or different from each other.)
(In the general formula (2), R ₂ represents a hydrocarbon group which may have hydrogen, fluorine, or a substituent, and may be the same or different from each other.)
(In the general formula (3), R ₃ may have a substituent, fluorine containing at least one hydrocarbon group, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ R ₄ may be different and the same.)).