JP2018060692A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery superior in high-temperature resistance, which uses a nonaqueous electrolyte containing acetonitrile superior in the balance between a viscosity and a relative dielectric constant, and LiPF.SOLUTION: A nonaqueous secondary battery comprises: a positive electrode having a positive electrode active material layer located on one or each of opposing faces of a current collector and including a positive electrode active material capable of occluding and releasing a lithium ion; a negative electrode having a negative electrode active material layer located on one or each of opposing faces of a current collector and including a carbon-based material capable of occluding and releasing a lithium ion; and a nonaqueous electrolyte. The nonaqueous electrolyte comprises a nonaqueous solvent which contains acetonitrile and LiPF. The nonaqueous secondary battery is arranged to include a sodium salt and a carbonate therein.SELECTED DRAWING: None

Description

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

  Non-aqueous secondary batteries such as lithium ion secondary batteries are characterized by light weight, high energy, and long life, and are widely used as power sources for various portable electronic devices. In recent years, it is also spreading for industrial use represented by power tools such as electric tools; in-vehicle use for electric vehicles, electric bicycles and the like. Further, it has been attracting attention in the field of power storage such as a residential power storage system.

As an electrolytic solution for a room temperature operation type lithium ion secondary battery, it is common to use a lithium salt electrolyte salt dissolved in a non-aqueous electrolyte solution. For example, an electrolytic solution in which a lithium salt containing fluorine is dissolved in a mixed solvent of a high dielectric solvent such as cyclic carbonate and a low-viscosity solvent such as lower chain carbonate. Among the fluorine-containing lithium salts, LiPF ₆ is particularly preferably used because of its high ionic conductivity. However, when water is present in the system, the fluorine-containing anion decomposes to generate hydrofluoric acid. Since hydrofluoric acid is a strong acid, it is known to corrode lithium transition metal composite oxides, current collector foils, and interiors that are generally used as positive electrode active materials, and to damage batteries. In order to prevent this, the following studies have been made.

  In Patent Document 1, an organic and / or inorganic copper corrosion inhibitor, or an organic and / or inorganic copper trap is used to prevent acid dissolution and metal elution of the negative electrode current collector copper foil. An inhibitor that is an agent is added. Examples of the inhibitor include 1,2,3-benzotriazole, or a derivative or similar thereof.

  In Patent Document 2, elution of transition metal is prevented by adding a chelating agent that does not react with lithium ions and do not form a coordination bond and forms a complex with transition metal ions in the battery. Examples of chelating agents include EDTA, NTA, DCTA, DTPA, EGTA.

JP 2001-273927 A Special table 2009-517836 gazette

  On the other hand, the present inventors have focused on an acetonitrile-based electrolyte having an excellent balance between viscosity and relative dielectric constant, and have continued investigations. Acetonitrile has a high potential as a solvent used in the electrolyte solution of the lithium ion secondary battery. However, lithium ion secondary batteries using an electrolytic solution containing acetonitrile are inferior in high-temperature durability performance compared to existing lithium ion secondary batteries using an electrolytic solution containing a carbonate solvent. Has not yet reached full-scale practical use.

From the results of various verification experiments, the reason why the acetonitrile-based lithium ion secondary battery is inferior in high-temperature durability is considered as follows. LiPF ₆ is generally used as an electrolyte salt of a lithium ion secondary battery. However, under a high temperature environment, LiPF ₆ decomposes while extracting hydrogen from the methyl group of acetonitrile, and the decomposition product is positive electrode transition. Promotes metal elution. The complex cation in which acetonitrile is coordinated to the eluted metal is chemically stable, and the redox reaction of the stable complex cation may cause self-discharge. These phenomena supported by the results of the disassembly analysis are problems newly found by the present inventors and are not described at all in the above-mentioned literature. Further, even when these additives were used, the high temperature durability could not be improved in the use of the acetonitrile electrolyte.

The present invention relates to a non-aqueous secondary battery using a non-aqueous electrolyte containing acetonitrile and LiPF ₆ having a good balance between viscosity and relative dielectric constant, and a non-aqueous secondary battery having excellent high-temperature durability. The purpose is to provide.

  The present invention for solving the above-mentioned problems has the following configuration.

[1] A positive electrode having a positive electrode active material layer containing a positive electrode active material capable of inserting / extracting lithium ions on one side or both sides of a current collector, and lithium ion on one side or both sides of the current collector A non-aqueous secondary battery comprising a negative electrode having a negative electrode active material layer made of a carbon-based material capable of occluding / desorbing, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte in the non-aqueous electrolyte A non-aqueous secondary battery comprising acetonitrile and LiPF _{6 in} an aqueous solvent, wherein the non-aqueous secondary battery contains a sodium salt and a carbonate.

[2] In the above [1], the sodium salt contains sodium ion in an amount of 0.01 to 7% by weight based on the total weight of the positive electrode active material layer and the negative electrode active material layer. The nonaqueous secondary battery as described.

[3] The carbonate is characterized in that the carbonate ion contains an amount of 0.1 to 10% by weight based on the total weight of the positive electrode active material layer and the negative electrode active material layer [1] Or the non-aqueous secondary battery as described in [2].

[4] The nonaqueous secondary battery according to any one of [1] to [3], wherein the nonaqueous electrolytic solution contains LiPF ₆ and a lithium salt other than LiPF ₆ .

[5] The non-aqueous secondary battery according to any one of [1] to [4], wherein the content of the acetonitrile is 30% by volume or more in the non-aqueous solvent.

[6] The non-aqueous secondary material according to any one of [1] to [5], wherein the positive electrode active material contains at least one transition metal element selected from Ni, Mn, and Co. battery.

[7] In any one of [1] to [6], the capacity retention rate is 90% or more in the cycle characteristic evaluation at 50 ° C. of the non-aqueous secondary battery defined below. The nonaqueous secondary battery as described.
The non-aqueous secondary battery is stored at 50 ° C. for 2 hours, and then charged at a constant current equivalent to 2C to reach a battery voltage of 4.2V, and then charged at a constant voltage of 4.2V for a total of 2 hours. Discharge to 3.0V with a constant current corresponding to 2C. With this as the first charge / discharge cycle, 50 cycles of charge / discharge are performed, and the ratio of the discharge capacity after the end of 50 cycles to the discharge capacity of the first cycle is defined as the capacity maintenance rate.

According to the present invention, in a non-aqueous secondary battery using a non-aqueous electrolyte containing acetonitrile and LiPF ₆ excellent in balance between viscosity and relative dielectric constant, a non-aqueous secondary battery excellent in high temperature durability is obtained. Can be provided.

It is a top view which shows roughly an example of the non-aqueous secondary battery of this embodiment. It is the sectional view on the AA line of the non-aqueous secondary battery of FIG.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. In the present specification, numerical ranges described using “to” include numerical values described before and after.

<1. Overall configuration of non-aqueous secondary battery>
The electrolyte solution of this embodiment can be used for a non-aqueous secondary battery, for example. As the nonaqueous secondary battery of this embodiment, for example, a positive electrode having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium ions, and occluding / desorbing lithium ions. And a negative electrode having a negative electrode active material layer made of a possible carbon-based material.

  Specifically, the non-aqueous secondary battery of the present embodiment may be the non-aqueous secondary battery illustrated in FIGS. 1 and 2. Here, FIG. 1 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  The non-aqueous secondary battery 100 is a laminated electrode formed by laminating a positive electrode 150 and a negative electrode 160 with a separator 170 interposed in a space 120 formed inside a battery exterior 110 constituted by two aluminum laminate films. The body and the non-aqueous electrolyte (not shown) are accommodated. The battery exterior 110 is sealed by heat-sealing upper and lower aluminum laminate films at the outer periphery thereof. The laminate in which the positive electrode 150, the separator 170, and the negative electrode 160 are sequentially laminated is impregnated with a non-aqueous electrolyte solution. In FIG. 2, in order to avoid the drawing from being complicated, each layer constituting the battery exterior 110 and each layer constituting each of the positive electrode 150 and the negative electrode 160 are not shown separately.

  It is preferable that the aluminum laminated film which comprises the battery exterior 110 is what coat | covered both surfaces of aluminum foil with polyolefin resin.

  The positive electrode 150 is connected to the positive electrode lead body 130 in the battery 100. Although not shown, the negative electrode 160 is also connected to the negative electrode lead body 140 in the battery 1. Each of the positive electrode lead body 130 and the negative electrode lead body 140 is drawn to the outside of the battery outer casing 110 so that it can be connected to an external device or the like. It is heat-sealed with the sides.

  In the non-aqueous secondary battery 100 illustrated in FIGS. 1 and 2, the positive electrode 150 and the negative electrode 160 each have a single laminated electrode body. It can be increased as appropriate. In the case of a laminated electrode body having a plurality of each of the positive electrode 150 and the negative electrode 160, the tabs of the same electrode may be joined by welding or the like, and then joined to one lead body by welding or the like and taken out of the battery. Examples of the tab having the same polarity include an aspect constituted by an exposed portion of the current collector, an aspect constituted by welding a metal piece to the exposed portion of the current collector, and the like.

  The positive electrode 150 includes a positive electrode active material layer prepared from a positive electrode mixture and a positive electrode current collector. The negative electrode 160 includes a negative electrode active material layer prepared from a negative electrode mixture and a negative electrode current collector. The positive electrode 150 and the negative electrode 160 are disposed so that the positive electrode active material layer and the negative electrode active material layer face each other with the separator 170 interposed therebetween.

  Hereinafter, the term “electrode” is abbreviated as a generic term for the positive electrode and the negative electrode, the term “electrode active material layer” is a generic term for the positive electrode active material layer and the negative electrode active material layer, and the term “electrode mixture” is generically termed for the positive electrode mixture and the negative electrode mixture.

  As each of these members, a material provided in a conventional lithium ion secondary battery can be used as long as each requirement in the present embodiment is satisfied. For example, the following materials may be used. Hereinafter, each member of the non-aqueous secondary battery will be described in detail.

<2. Electrolyte>
The electrolytic solution in the present embodiment includes at least a non-aqueous solvent (hereinafter also simply referred to as “solvent”) and LiPF ₆ . Although LiPF ₆ is excellent in ionic conductivity, it does not have sufficient thermal stability and has the property of being easily hydrolyzed by a trace amount of water in a solvent to generate lithium fluoride and hydrogen fluoride. When LiPF ₆ decomposes, the ionic conductivity of the electrolyte containing LiPF ₆ decreases, and the generated lithium fluoride and hydrogen fluoride corrode materials such as electrodes and current collectors, or decompose the solvent. Doing so may cause a fatal negative effect on the battery.

  The electrolytic solution in the present embodiment preferably does not contain moisture, but may contain a very small amount of moisture as long as the solution of the problem of the present invention is not hindered. The water content is preferably 0 to 100 ppm with respect to the total amount of the electrolytic solution.

<2-1. Non-aqueous solvent>
The term “non-aqueous solvent” as used in the present embodiment refers to a component excluding LiPF ₆ and an additional lithium salt to be added from the electrolytic solution. That is, when the electrolytic solution contains other additives described later, the solvent and the electrode protecting additive are collectively referred to as “non-aqueous solvent”.

  The non-aqueous solvent is not particularly limited as long as acetonitrile is contained in the non-aqueous solvent, and a non-aqueous solvent other than acetonitrile may or may not be contained.

  Acetonitrile has high ion conductivity and can increase the diffusibility of lithium ions in the battery. Therefore, when the electrolytic solution contains acetonitrile, particularly in the positive electrode in which the positive electrode active material layer is thickened to increase the filling amount of the positive electrode active material, it is difficult for lithium ions to reach when discharging at a high load. Lithium ions can diffuse well to the region in the vicinity of the body. Therefore, a sufficient capacity can be extracted even during high-load discharge, and a non-aqueous secondary battery having excellent load characteristics can be obtained.

  By using acetonitrile as the non-aqueous solvent of the non-aqueous electrolyte solution, as described above, the ionic conductivity of the non-aqueous electrolyte solution is improved, so that the quick charge characteristics of the non-aqueous secondary battery can be enhanced. In constant current (CC) -constant voltage (CV) charging of a non-aqueous secondary battery, the capacity per unit time in the CC charging period is larger than the charging capacity per unit time in the CV charging period. When acetonitrile is used as the non-aqueous solvent of the non-aqueous electrolyte, the CC chargeable area can be increased (the CC charge time can be increased), and the charge current can be increased, so the non-aqueous secondary battery can be charged. The time from the start to the fully charged state can be greatly shortened.

  The content of acetonitrile is preferably 1 to 100% by volume with respect to the total amount of the non-aqueous solvent, more preferably 30% by volume or more, still more preferably 40% by volume or more, and more preferably 70% by volume or more. It is.

  When the content of acetonitrile is 30% by volume or more, ionic conductivity tends to increase and high output characteristics tend to be exhibited, and further, dissolution of the lithium salt can be promoted. When the content of acetonitrile in the non-aqueous solvent is within the above range, the storage characteristics and other battery characteristics tend to be further improved while maintaining the excellent performance of acetonitrile.

  Examples of non-aqueous solvents other than acetonitrile include alcohols such as methanol and ethanol; aprotic solvents and the like. Among these, an aprotic polar solvent is preferable.

Among non-aqueous solvents other than acetonitrile, specific examples of aprotic solvents include, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene. Cyclic carbonate represented by carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, and vinylene carbonate; fluoroethylene carbonate, 1,2-difluoroethylene Cyclic fluorinated carbonates typified by carbonate and trifluoromethylethylene carbonate; γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone Representative lactones; sulfur compounds typified by sulfolane, dimethyl sulfoxide, and ethylene glycol sulfite; cyclic ethers typified by tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane; ethylmethyl Chain carbonates typified by carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and methyl trifluoroethyl carbonate; trifluorodimethyl carbonate, Chain fluorinated carbonates represented by trifluorodiethyl carbonate and trifluoroethyl methyl carbonate Bonates; mononitriles typified by propionitrile, butyronitrile, valeronitrile, benzonitrile, and acrylonitrile; alkoxy group-substituted nitriles typified by methoxyacetonitrile and 3-methoxypropionitrile; malononitrile, succinonitrile, glutaronitrile , Adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanooctane, 2,7-dicyano Octane, 1,9-dicyanononane, 2,8-dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, and dinitriles represented by 2,4-dimethylglutaronitrile; cyclics represented by benzonitrile Nitrile; Pro Chain esters represented by methyl pionate; chain ethers represented by dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme; Rf ⁴ -OR ⁵ (Rf ⁴ contains fluorine) Alkyl groups, R ⁵ is an organic group which may contain fluorine); ketones represented by acetone, methyl ethyl ketone, and methyl isobutyl ketone; Halides. These are used singly or in combination of two or more.

  Among these non-aqueous solvents other than acetonitrile, it is more preferable to use one or more of cyclic carbonate and chain carbonate together with acetonitrile. Here, only one of those exemplified above as the cyclic carbonate and the chain carbonate may be selected and used, or two or more (for example, two or more of the cyclic carbonates exemplified above, Two or more of the exemplified chain carbonates or one or more of the exemplified cyclic carbonates and two or more of the exemplified chain carbonates may be used. Among these, ethylene carbonate, propylene carbonate, vinylene carbonate, or fluoroethylene carbonate is more preferable as the cyclic carbonate, and ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate is more preferable as the chain carbonate. It is more preferable to use a cyclic carbonate.

  Acetonitrile is electrochemically susceptible to reductive decomposition. Therefore, it is preferable to perform at least one of mixing this with another solvent and adding an electrode protective additive for forming a protective film on the electrode.

  In order to increase the ionization degree of the lithium salt that contributes to charge / discharge of the non-aqueous secondary battery, the non-aqueous solvent preferably contains one or more cyclic aprotic polar solvents, and contains one or more cyclic carbonates. Is more preferable.

<2-2. Lithium salt>
LiPF ₆ is used as the lithium salt as the electrolyte salt in the present embodiment. Furthermore, other fluorine-containing inorganic lithium salts may be included. The “fluorine-containing inorganic lithium salt” refers to a lithium salt that does not contain a carbon atom in an anion but contains a fluorine atom in an anion and is soluble in acetonitrile. The fluorine-containing inorganic lithium salt in the present embodiment forms a passive film on the surface of the metal foil that is the positive electrode current collector, and suppresses corrosion of the positive electrode current collector. The fluorine-containing inorganic lithium salt is excellent as an electrolyte salt from the viewpoint of solubility, conductivity, and ionization degree. Specific examples of the fluorine-containing inorganic lithium salt used other than LiPF ₆ include, for example, LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , Li ₂ B ₁₂ F _b H _12-b [b is 0 to 3 Integer, preferably an integer of 1 to 3], LiN (SO ₂ F) _{2 and the} like. Among these, use of a fluorine-containing inorganic lithium salt having a boron atom is preferable because it tends to capture an excessive free acid component that may cause battery deterioration, and LiBF ₄ is particularly preferable from such a viewpoint.

  There is no restriction | limiting in particular about the total content of the fluorine-containing inorganic lithium salt in the electrolyte solution of this embodiment. However, this value is preferably 0.2 mol or more, more preferably 0.5 mol or more, and still more preferably 0.8 mol or more with respect to 1 L of the non-aqueous solvent. This value is preferably 15 mol or less, more preferably 4 mol or less, and even more preferably 2.8 mol or less with respect to 1 L of the non-aqueous solvent. When the total content of the fluorine-containing inorganic lithium salt is within the above range, the ionic conductivity tends to increase and high output characteristics tend to be exhibited, and while maintaining the excellent performance of acetonitrile, storage characteristics and other batteries There is a tendency that the characteristics can be further improved.

As a lithium salt used in combination with LiPF ₆ in the present embodiment, in addition to the fluorine-containing inorganic lithium salt, an inorganic lithium salt and / or an organic lithium salt used for a non-aqueous secondary battery may be supplementarily added. Good. The “inorganic lithium salt” refers to a lithium salt that does not contain a carbon atom in an anion and is soluble in acetonitrile. “Organic lithium salt” refers to a lithium salt that contains a carbon atom in its anion and is soluble in acetonitrile.

Specific examples include inorganic lithium salts that do not contain fluorine atoms in the anion such as LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiB ₁₀ Cl ₁₀ , chloroborane Li; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ Organic lithium salts such as F ₄ (SO ₃ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), lower aliphatic carboxylic acid Li, tetraphenylborate Li; LiN (SO ₂ An organic lithium salt represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 1 to 8] such as CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ ; LiPF ₅ (CF ₃ ) _{LiPF n (C p F 2p +} 1) 6-n [n is an integer of 1 to 5, p is an integer of 1 to 8] the organic lithium salt represented by the equal; LiBF ₃ (C Table with _{LiB (C 2 O 4) 2} ; LiBF q (C s F 2s + 1) 4-q [q is an integer of 1 to 3, s is an integer of 1 to 8] The organic lithium salt represented by the ₃₎ and the like Lithium bis (oxalato) borate (LiBOB); Halogenated LiBOB; LiBF ₂ (C ₂ O ₄ ) Lithium oxalate difluoroborate (LiODFB); LiB (C ₃ O ₄ H ₂ ) ₂ Lithium bis (malonate) borate (LiBMB); Lithium tetrafluorooxalatophosphate represented by LiPF ₄ (C ₂ O ₄ ), Lithium difluorobis (oxalato) represented by LiPF ₂ (C ₂ O ₄ ) ₂ Organic lithium salts such as phosphates, lithium salts bonded to polyvalent anions; the following general formulas (1a), (1b), and (1c ):
LiC (SO ₂ R ⁶ ) (SO ₂ R ⁷ ) (SO ₂ R ⁸ ) (1a)
LiN (SO ₂ OR ⁹ ) (SO ₂ OR ¹⁰ ) (1b)
LiN (SO ₂ R ¹¹ ) (SO ₂ OR ¹² ) (1c)
{Wherein R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² may be the same as or different from each other, and represent a C 1-8 perfluoroalkyl group. Show. }, And one or more of them can be used together with the fluorine-containing inorganic lithium salt.

In order to improve load characteristics and charge / discharge cycle characteristics of the non-aqueous secondary battery, it is preferable to supplementarily add an organic lithium salt having an oxalic acid group, and LiB (C ₂ O ₄ ) ₂ , LiBF ₂ ( It is particularly preferable to add one or more selected from the group consisting of C ₂ O ₄ ), LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O ₄ ) ₂ . The organic lithium salt having an oxalic acid group may be contained in the negative electrode (negative electrode active material layer) in addition to being added to the nonaqueous electrolytic solution.

  The addition amount of the organolithium salt having an oxalic acid group to the non-aqueous electrolyte is, as the amount per 1 L of the non-aqueous solvent, of the non-aqueous electrolyte is 0. The amount is preferably 005 mol or more, more preferably 0.02 mol or more, and further preferably 0.05 mol or more. However, if the amount of the organic lithium salt having an oxalic acid group in the non-aqueous electrolyte is too large, it may be precipitated. Therefore, the addition amount of the organic lithium salt having an oxalic acid group to the non-aqueous electrolyte is preferably less than 1.0 mol per liter of the non-aqueous solvent of the non-aqueous electrolyte. More preferably, it is less than 5 mol, and still more preferably less than 0.2 mol.

<2-3. Electrode protective additive>
The electrolyte solution in this embodiment may contain an additive for protecting the electrode in addition to acetonitrile. The electrode protecting additive is not particularly limited as long as it does not hinder the problem solving according to the present invention. You may substantially overlap with the substance which plays the role as a solvent which melt | dissolves lithium salt (namely, the above-mentioned non-aqueous solvent). The electrode protecting additive is preferably a substance that contributes to improving the performance of the electrolytic solution and the non-aqueous secondary battery in this embodiment, but also includes substances that are not directly involved in the electrochemical reaction.

  Specific examples of the electrode protecting additive include, for example, 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro. -1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4, Fluoroethylene carbonate represented by 4,5,5-tetrafluoro-1,3-dioxolan-2-one and 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one; Unsaturated bond-containing cyclic carbonates typified by vinylene carbonate, 4,5-dimethylvinylene carbonate, and vinylethylene carbonate; γ-butyrolactone, γ-valerolactone , Γ-caprolactone, δ-valerolactone, δ-caprolactone, and lactones represented by ε-caprolactone; cyclic ethers represented by 1,4-dioxane; ethylene sulfite, propylene sulfite, butylene sulfite, pentensal Examples thereof include cyclic sulfur compounds represented by phyto, sulfolane, 3-methylsulfolane, 1,3-propane sultone, 1,4-butane sultone, and tetramethylene sulfoxide. These are used singly or in combination of two or more.

  Acetonitrile, which is a component of a non-aqueous solvent, is easily electrochemically reduced and decomposed. Therefore, the non-aqueous solvent containing acetonitrile contains a cyclic aprotic polar solvent as an additive for forming a protective film on the negative electrode. It is preferable to include at least one species, and it is more preferable to include at least one type of unsaturated bond-containing cyclic carbonate.

  There is no restriction | limiting in particular about content of the electrode protection additive in the electrolyte solution in this embodiment. However, the content of the electrode protection additive with respect to the total amount of the non-aqueous solvent is preferably 0.1 to 30% by volume, more preferably 2 to 20% by volume, and 5 to 15% by volume. More preferably.

  In this embodiment, deterioration of electrolyte solution is suppressed, so that there is much content of the additive for electrode protection. However, the lower the content of the electrode protecting additive, the higher the high output characteristics of the non-aqueous secondary battery in a low temperature environment. Therefore, by adjusting the content of the electrode protecting additive within the above-mentioned range, excellent performance based on the high ionic conductivity of the electrolytic solution can be obtained without impairing the basic function as a non-aqueous secondary battery. There is a tendency to make the most of it. By preparing the electrolytic solution with such a composition, all of the cycle performance of the non-aqueous secondary battery, the high output performance in a low temperature environment, and other battery characteristics tend to be further improved.

<2-4. Other optional additives>
In the present embodiment, for the purpose of improving the charge / discharge cycle characteristics of the non-aqueous secondary battery, high-temperature storage property, improving safety (for example, preventing overcharge, etc.), the non-aqueous electrolyte solution includes, for example, anhydrous acid, Sulfonic acid ester, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, tert-butylbenzene, phosphoric acid ester [ethyl diethylphosphonoacetate (EDPA): (C ₂ H ₅ O) ₂ (P═O) —CH ₂ ( C═O) OC ₂ H ₅ , tris (trifluoroethyl) phosphate (TFEP): (CF ₃ CH ₂ O) ₃ P═O, triphenyl phosphate (TPP): (C ₆ H ₅ O) ₃ P ═O etc.] and the like, and optional additives selected from derivatives of these respective compounds and the like can be appropriately contained. In particular, the phosphoric acid ester has an effect of suppressing side reactions during storage and is effective.

<3. Positive electrode>
The positive electrode 150 includes a positive electrode active material layer prepared from a positive electrode mixture and a positive electrode current collector. The positive electrode 150 is not particularly limited as long as it functions as a positive electrode of a non-aqueous secondary battery, and may be a known one. The positive electrode active material layer contains a positive electrode active material and optionally further contains a conductive additive and a binder.

  The positive electrode active material layer preferably contains a material capable of inserting and extracting lithium ions as the positive electrode active material. It is preferable that a positive electrode active material layer contains a conductive support agent and a binder as needed with a positive electrode active material. The use of such a material is preferable because a high voltage and a high energy density tend to be obtained.

Examples of the positive electrode active material include the following general formulas (2a) and (2b):
Li _x MO ₂ (2a)
Li _y M ₂ O ₄ (2b)
{In the formula, M represents one or more metal elements including at least one transition metal element, x represents a number of 0 to 1.1, and y represents a number of 0 to 2. }, A lithium-containing compound represented by each of the above and other lithium-containing compounds.

Examples of the lithium-containing compound represented by each of the general formulas (2a) and (2b) include lithium cobalt oxides typified by LiCoO ₂ ; LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O ₄ . Lithium manganese oxide typified; Lithium nickel oxide typified by LiNiO ₂ ; Li _z MO ₂ (M contains at least one transition metal element selected from Ni, Mn, and Co, and Ni, Mn 2 or more metal elements selected from the group consisting of Co, Al, and Mg, and z represents a number of more than 0.9 and less than 1.2. It is done.

The lithium-containing compound other than the lithium-containing compound represented by each of the general formulas (2a) and (2b) is not particularly limited as long as it contains lithium. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, a metal chalcogenide containing lithium, a metal phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element. (For example, Li _t M _u SiO ₄ , M is as defined in the general formula (3a), t is a number from 0 to 1, and u is a number from 0 to 2). From the viewpoint of obtaining a higher voltage, lithium-containing compounds include lithium, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium, among others. A composite oxide containing at least one transition metal element selected from the group consisting of (Cr), vanadium (V), and titanium (Ti), and a metal phosphate compound are preferable.

More specifically, the lithium-containing compound is more preferably a composite oxide containing lithium and a transition metal element or a metal chalcogenide containing lithium and a transition metal element, and a metal phosphate compound containing lithium. General formulas (3a) and (3b):
^{_{Li v M I D 2 (3a}} )
Li _w M ^II PO ₄ (3b)
{Wherein D represents oxygen or a chalcogen element, M ^I and M ^II each represent one or more transition metal elements, and the values of v and w depend on the charge / discharge state of the battery, and v is 0.05 -1.10, w shows the number of 0.05-1.10. }, Compounds represented by each of the above.

  The lithium-containing compound represented by the above general formula (3a) has a layered structure, and the compound represented by the above general formula (3b) has an olivine structure. These lithium-containing compounds are obtained by substituting a part of the transition metal element with Al, Mg, or other transition metal elements for the purpose of stabilizing the structure, and include these metal elements in the grain boundaries. It is also possible to use a material in which some of the oxygen atoms are substituted with fluorine atoms or the like, or at least a part of the surface of the positive electrode active material particles coated with another positive electrode active material.

  As the positive electrode active material in the present embodiment, only the lithium-containing compound as described above may be used, or other positive electrode active material may be used in combination with the lithium-containing compound.

Examples of such other positive electrode active materials include metal oxides or metal chalcogenides having a tunnel structure and a layered structure; sulfur; a conductive polymer. Examples of the metal oxide or metal chalcogenide having a tunnel structure and a layered structure include MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ , and NbSe. ₂ includes oxides, sulfides, selenides, and the like of metals other than lithium. Examples of the conductive polymer include conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole.

  The other positive electrode active materials described above are used alone or in combination of two or more, and are not particularly limited. However, since it is possible to occlude and release lithium ions in a reversible manner and to achieve a high energy density, the positive electrode active material layer is at least one transition metal selected from Ni, Mn, and Co. It is preferable to contain an element.

  When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the use ratio of both is preferably 80% by mass or more, and 85% by mass as the use ratio of the lithium-containing compound to the entire positive electrode active material. % Or more is more preferable.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 6 parts by mass or less, more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  The positive electrode active material layer is formed by applying a positive electrode mixture-containing slurry, in which a positive electrode mixture obtained by mixing a positive electrode active material and, if necessary, a conductive additive and a binder in a solvent, is applied to a positive electrode current collector and dried (solvent removal) And is formed by pressing as necessary. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned. The solid content concentration in the positive electrode mixture-containing slurry is preferably 30 to 80% by mass, more preferably 40 to 70% by mass.

  An aluminum foil is used for the positive electrode current collector. A carbon coat may be applied to the surface of the current collector, or may be processed into a mesh shape. The thickness of the positive electrode current collector is preferably 5 to 40 μm, more preferably 7 to 35 μm, and still more preferably 9 to 30 μm.

  The positive electrode mixture-containing slurry prepared as described above is applied to a positive electrode current collector and dried to form a positive electrode active material layer. The positive electrode active material layer obtained after drying is compressed by a roll press or the like. The thickness of the positive electrode active material layer after compression is preferably 10 to 300 μm, more preferably 20 to 280 μm, and still more preferably 30 to 250 μm.

<4. Negative electrode>
The negative electrode 160 includes a negative electrode active material layer prepared from a negative electrode mixture and a negative electrode current collector. The negative electrode 160 is not particularly limited as long as it functions as a negative electrode of a non-aqueous secondary battery, and may be a known one.

From the viewpoint that the negative electrode active material layer can increase the battery voltage, lithium ion as a negative electrode active material is 0.4 V vs. It is preferable to contain a material that can be occluded at a lower potential than Li / Li ⁺ . It is preferable that a negative electrode active material layer contains a conductive support agent and a binder as needed with a negative electrode active material.

Examples of the negative electrode active material include amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, carbon fiber, activated carbon , Carbon materials represented by graphite, carbon colloid, and carbon black.
A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 20 parts by mass or less, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 10 parts by mass or less, more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  The negative electrode active material layer is coated with a negative electrode mixture-containing slurry in which a negative electrode mixture obtained by mixing a negative electrode active material and, if necessary, a conductive additive and a binder is dispersed in a solvent, and dried (solvent removal). And it forms by pressing as needed. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned. The solid content concentration in the negative electrode mixture-containing slurry is preferably 30 to 80% by mass, more preferably 40 to 70% by mass.

  The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode current collector may have a carbon coating on the surface or may be processed into a mesh shape. The thickness of the negative electrode current collector is preferably 5 to 40 μm, more preferably 6 to 35 μm, and still more preferably 7 to 30 μm.

  The negative electrode mixture-containing slurry prepared as described above is applied to a negative electrode current collector and dried to form a negative electrode active material layer. The negative electrode active material layer obtained after drying is compressed by a roll press or the like. The thickness of the negative electrode active material layer after compression is preferably 10 to 300 μm, more preferably 20 to 280 μm, and still more preferably 30 to 250 μm.

<5. Separator>
The nonaqueous secondary battery 100 in the present embodiment preferably includes a separator 170 between the positive electrode 150 and the negative electrode 160 from the viewpoint of providing safety such as prevention of short circuit between the positive electrode 150 and the negative electrode 160 and shutdown. The separator 170 may be the same as that provided in a known non-aqueous secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator 170 include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable.

  As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is suitably used. Examples of the nonwoven fabric include a porous film made of a heat resistant resin such as glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, and aramid.

  The separator 170 may have a configuration in which one type of microporous membrane is laminated or a plurality of microporous membranes may be laminated, or two or more types of microporous membranes may be laminated. The separator 170 may have a configuration in which a single layer or a plurality of layers are stacked using a mixed resin material obtained by melting and kneading two or more kinds of resin materials.

<6. Battery exterior>
Although the structure of the battery exterior 110 of the non-aqueous secondary battery 100 in this embodiment is not specifically limited, For example, any battery exterior of a battery can and a laminate film exterior body can be used. As the battery can, for example, a metal can made of steel or aluminum can be used. As the laminate film outer package, for example, a laminate film having a three-layer structure of hot melt resin / metal film / resin can be used.

  Laminate film exterior is in a state where two sheets are stacked with the hot-melt resin side facing inward, or folded so that the hot-melt resin side faces inward, and the end is sealed by heat sealing It can be used as an exterior body. When using a laminate film exterior body, the positive electrode lead body 130 (or a lead tab connected to the positive electrode terminal and the positive electrode terminal) is connected to the positive electrode current collector, and the negative electrode lead body 140 (or the negative electrode terminal and the negative electrode terminal) is connected to the negative electrode current collector. A lead tab to be connected) may be connected. In this case, the laminate film exterior body is sealed with the ends of the positive electrode lead body 130 and the negative electrode lead body 140 (or the lead tab connected to each of the positive electrode terminal and the negative electrode terminal) pulled out of the exterior body. Also good.

  When an acetonitrile-based electrolyte is used, the laminate cell tends to swell during heat sealing, so the distance from the laminated body or wound body of the sealing part into which the electrolytic solution is injected out of the sealing part of the aluminum laminate. It is preferable to set it as 15-40 mm. By setting the distance as described above, swelling of the cells can be prevented.

<7. Na salt and carbonate present in the battery>
The non-aqueous secondary battery of this embodiment is characterized by containing a sodium salt and a carbonate inside the battery. Examples of sodium salts include NaNO ₃ , NaNO ₂ , Na ₂ SO ₄ , NaHSO ₃ , NaHClO, Na ₂ CO ₃ , NaHCO ₃ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ , HCOONa, CH ₃ COONa, HOOC-COONa, NaOOC-COONa, and <2-2. Examples include salts in which lithium in organic and inorganic lithium salts described in <Lithium salt> is replaced with sodium. The amount of sodium salt in the battery is preferably such that sodium ions are 0.01 to 7% by weight based on the total weight of the positive electrode active material layer and the negative electrode active material layer. More preferably, it is 0.03 to 5 weight%, More preferably, it is 0.05 to 3 weight%. The positive electrode active material layer and the negative electrode active material layer refer to a layer formed on a current collector of each electrode by mixing an active material, a conductive additive, a binder, and other additives.

Examples of carbonates include Na ₂ CO ₃ , NaHCO ₃ , (NH ₄ ) ₂ CO ₃ , K ₂ CO _{3 and the} like. The battery internal content of carbonate is 0.1 to 10% by weight of carbonate ion (CO ₃ ²⁻ ) with respect to the total weight of the positive electrode active material layer and the negative electrode active material layer. Preferably it is 0.3-5 weight%, More preferably, it is 0.6-4 mass%, More preferably, it is 0.5-3 weight%.

Na ₂ CO ₃ and NaHCO ₃ are preferably used because they are both a sodium salt and a carbonate. However, the present invention is not limited to this, and a plurality of compounds containing sodium ions and carbonate ions may be mixed and used.

  The sodium salt and carbonate used in the non-aqueous secondary battery of the present embodiment exist in almost the entire area of the battery if dissolved in the electrolyte. A state of being locally present on any one or more of the surface, the surface or inside of the active material layer, and the surface of the electrode is also included.

  Examples of the method for adding sodium salt and carbonate at the time of manufacturing the battery include the following.

1) A sodium salt and a carbonate are dissolved in an electrolytic solution.
2) A salt solution of sodium salt and carbonate is applied to the surface of the active material layer. Separately, a coating solution for forming a film may be prepared by mixing a polymer, a solvent, and a salt, and coating and drying may be performed.
3) When forming the active material layer, a salt solution of sodium salt and carbonate or a coating solution for film formation is added to the electrode mixture.
4) The formed active material layer is impregnated with a salt solution of sodium salt and carbonate or a coating solution for film formation.

  The following method is used as a method for determining the sodium salt and carbonate content in the battery. The following method is used as a method for quantifying the organic acid ammonium salt content in the positive electrode active material layer and the negative electrode active material layer. The positive electrode active material layer and the negative electrode active material layer are peeled from the current collector, sodium salt and carbonate are extracted with water or the like, and the amount of sodium ions and carbonate ions is quantified by ion chromatography. The weights of the positive electrode active material layer and the negative electrode active material layer are determined by measuring the weight obtained by washing and removing the electrolyte solution and determining the content ratio.

  By containing a sodium salt and a carbonate in the battery, it is possible to trap hydrofluoric acid, suppress the reaction between hydrofluoric acid and the electrolyte, and improve high-temperature durability.

<8. Battery Manufacturing Method>
The non-aqueous secondary battery 100 in this embodiment has the above-described non-aqueous electrolyte solution, the positive electrode 150 having a positive electrode active material layer on one or both sides of the current collector, and the negative electrode active material layer on one or both sides of the current collector. It is produced by a known method using the negative electrode 160, the battery outer casing 110, and, if necessary, the separator 170.

  First, the laminated body which consists of the positive electrode 150 and the positive electrode 160 and the separator 170 as needed is formed. For example, an aspect in which a long positive electrode 150 and a negative electrode 160 are wound in a stacked state in which the long separator is interposed between the positive electrode 150 and the negative electrode 160 to form a wound structure laminate; And a mode of forming a laminate having a laminated structure in which the negative electrode 160 and the negative electrode sheet obtained by cutting the negative electrode 160 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet; It is possible to form a laminated body having a laminated structure in which the separators are folded in a zigzag manner and the positive electrode sheet and the negative electrode sheet are alternately inserted between the zipped separators.

  Next, the above-described laminated body is accommodated in the battery exterior 110 (battery case), the electrolytic solution according to this embodiment is injected into the battery case, and the laminated body is immersed in the electrolytic solution and sealed. The nonaqueous secondary battery in this embodiment can be produced.

  Alternatively, an electrolyte solution in a gel state is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-like positive electrode 150, a negative electrode 160, an electrolyte membrane, and, if necessary, a separator 170. A non-aqueous secondary battery 100 can also be produced by forming a laminated body having a laminated structure using the battery and housing the battery in the battery exterior 110.

  The shape of the non-aqueous secondary battery 100 in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminated shape, and the like are suitably employed.

  In addition, as for the arrangement of the electrodes, there is a portion where the outer peripheral end of the negative electrode active material layer and the outer peripheral end of the positive electrode active material layer overlap, or there is a portion where the width is too small in the non-opposing portion of the negative electrode active material layer. When it is designed in such a manner, there is a possibility that the charge / discharge cycle characteristics in the non-aqueous secondary battery may be deteriorated due to the displacement of the electrode during battery assembly. Therefore, it is preferable that the electrode body used for the non-aqueous secondary battery is previously fixed with a tape such as polyimide tape, polyphenylene sulfide tape, PP tape, an adhesive, or the like.

  The non-aqueous secondary battery 100 in the present embodiment can function as a battery by the initial charge, but is stabilized when a part of the electrolytic solution is decomposed during the initial charge. Although there is no restriction | limiting in particular about the method of initial charge, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003-0.2C More preferably, it is performed. It is also preferable that the initial charging is performed via a constant voltage charging in the middle. The constant current for discharging the rated capacity in 1 hour is 1C. By setting the voltage range in which the lithium salt is involved in the electrochemical reaction to be long, SEI is formed on the electrode surface and has the effect of suppressing the increase in internal resistance including the positive electrode 150, as well as the reaction product Is not firmly fixed only to the negative electrode 6, and in some form, a good effect is given to members other than the negative electrode 160 such as the positive electrode 150 and the separator 170. For this reason, it is very effective to perform the initial charge in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

  The nonaqueous secondary battery 100 in this embodiment can also be used as a battery pack in which a plurality of nonaqueous secondary batteries 100 are connected in series or in parallel. From the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range per unit is preferably 2 to 5 V, more preferably 2.5 to 5 V, and 2.75 V to 5 V. Particularly preferred.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment. The present invention can be variously modified without departing from the gist thereof.

  Hereinafter, the present invention will be described in more detail with reference to examples. Various evaluations were performed as follows.

(1) Production of Positive Electrode A positive electrode active material (compounds are as shown in Table 1), acetylene black powder as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder at a mass of 100: 3.3: 3. The positive electrode mixture was obtained by mixing at a ratio. N-methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture and further mixed to prepare a positive electrode mixture-containing slurry. The positive electrode mixture-containing slurry was applied to one surface of an aluminum foil while adjusting the basis weight to about 95.0 g / m ² on an aluminum foil having a thickness of 15 μm serving as a positive electrode current collector. When applying the positive electrode mixture-containing slurry to the aluminum foil, an uncoated region was formed so that a part of the aluminum foil was exposed. Then, the positive electrode which consists of a positive electrode active material layer and a positive electrode electrical power collector was obtained by rolling so that the density of a positive electrode active material layer might be 1.90 g / cm < ³ > with a roll press.

  Next, this positive electrode is cut so that the positive electrode active material layer has an area of 30 mm × 50 mm and includes an exposed portion of the aluminum foil, and an aluminum lead piece for taking out an electric current is welded to the exposed portion of the aluminum foil. And the positive electrode with a lead was obtained by performing vacuum drying for 12 hours at 120 degreeC.

(2) Production of negative electrode After mixing graphite as negative electrode active material, carboxymethyl cellulose as binder and styrene butadiene latex at a mass ratio of 100: 1.3: 1.5, and further adding an appropriate amount of water. The mixture was thoroughly mixed to prepare a negative electrode mixture-containing slurry. This slurry was applied to one side of the copper foil with a constant thickness on one side of the copper foil having a thickness of 10 μm. When applying the negative electrode mixture-containing slurry to the copper foil, an uncoated region was formed so that a part of the copper foil was exposed. Then, the negative electrode which consists of a negative electrode active material layer and a negative electrode electrical power collector was obtained by rolling so that the density of a negative electrode active material layer might be 1.20 g / cm < ³ > with a roll press.

  Next, the negative electrode is cut so that the area of the negative electrode active material layer is 32 mm × 52 mm and includes the exposed portion of the copper foil, and further, a nickel lead piece for taking out a current from the exposed portion of the copper foil Were welded and vacuum dried at 80 ° C. for 12 hours to obtain a negative electrode with leads.

(3) Assembly of single-layer laminated battery The positive electrode with lead and the negative electrode with lead after cutting are laminated via a polyethylene microporous membrane separator (thickness 21 μm) to form a laminated electrode body. The aluminum laminate sheet of 90 mm × 80 mm was housed in a package and vacuum dried at 80 ° C. for 5 hours in order to remove moisture. Subsequently, after injecting the electrolyte into the exterior body, the exterior body is sealed, and the exterior shown in FIG. 1 has a cross-sectional structure shown in FIG. Also referred to as a “layer laminate battery”. This single-layer laminated battery has a rated current value of 23 mAh and a rated voltage value of 4.2V.

(4) Evaluation of single-layer laminated battery For the single-layer laminated battery obtained as described above, first, a first charge / discharge treatment was performed according to the following procedure (4-1). Next, output characteristics were measured according to the following procedure (4-2). Charging / discharging was performed using charging / discharging apparatus ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-73S (trade name) manufactured by Futaba Kagaku Co., Ltd.

  Here, 1C means a current value at which a fully charged battery is discharged at a constant current and is expected to be discharged in 1 hour. In the following, it means a current value that is expected to discharge from a fully charged state of 4.2 V to 3.0 V at a constant current and finish discharging in 1 hour.

(4-1) Initial charge / discharge treatment of single-layer laminate battery The ambient temperature of the single-layer laminate battery is set to 25 ° C., and the battery voltage is 4.2 V by charging with a constant current of 1.125 mA corresponding to 0.05C. Then, the battery was charged until reaching the value of 4.2, and then charged at a constant current of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged to 3.0 V with a constant current of 7.5 mA corresponding to 0.3 C.

(4-2) 50 ° C. cycle evaluation The battery that has been initially charged and discharged in (4-1) is stored at 50 ° C. for 2 hours, and then charged with a constant current equivalent to 2C to reach a battery voltage of 4.2V. After that, the battery is charged with a constant voltage of 4.2V for a total of 2 hours, and discharged to 3.0V with a constant current corresponding to 2C. With this as the first charge / discharge cycle, 50 cycles of charge / discharge are performed, and the ratio of the discharge capacity after the end of 50 cycles to the discharge capacity of the first cycle is defined as the capacity maintenance rate.

[Examples and Comparative Examples]
When preparing the positive electrode, the carbonic acid compound solution described in Table 1 was applied to the surface of the positive electrode active material layer to prepare the Na ⁺ and CO ₃ ^2- content ratios described in Table 1. Specifically, a 5% carbonic acid compound solution dissolved in N-methyl-2-pyrrolidone is prepared, applied to the surface of the positive electrode active material layer, the solvent is dried, and the weight difference between before and after the application is determined. The proportion of ions contained in the layer was calculated. In addition, the concentration of LiPF ₆ is 1.3 mol / L and LiBOB is 0.01 mol / L in a non-aqueous solvent of acetonitrile / diethyl carbonate / vinylene carbonate / ethylene sulfite = 47/38/11/4 (volume ratio). The electrolyte solution thus dissolved was prepared and incorporated into the batteries of Examples and Comparative Examples.

  Table 1 lists the positive electrode active material compounds used in Examples 1 to 3 and Comparative Examples 1 and 2, added compounds, ion content ratios, and capacity retention ratios after 50 ° C. and 50 cycle evaluations.

  From the above results, it was found that the non-aqueous secondary battery using the electrolytic solution of this embodiment has improved high-temperature durability.

  Specifically, according to Examples 1 to 3, it was found that the capacity retention ratio could be 90% or more in 50 ° C. and 50 cycle characteristic evaluation.

  The non-aqueous secondary battery of the present invention is, for example, a portable device such as a mobile phone, a portable audio device, a personal computer, an IC (Integrated Circuit) tag; a rechargeable battery for a vehicle such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle; It can be applied to a residential power storage system.

DESCRIPTION OF SYMBOLS 100 Non-aqueous secondary battery 110 Battery exterior 120 Space of battery exterior 110 130 Positive electrode lead body 140 Negative electrode lead body 150 Positive electrode 160 Negative electrode 170 Separator

Claims (7)

A positive electrode having a positive electrode active material layer containing a positive electrode active material capable of inserting / extracting lithium ions on one side or both sides of a current collector;
A negative electrode having a negative electrode active material layer made of a carbon-based material capable of inserting / extracting lithium ions on one side or both sides of a current collector;
A non-aqueous secondary battery comprising a non-aqueous electrolyte solution,
The non-aqueous solvent in the non-aqueous electrolyte contains acetonitrile and LiPF ₆ ;
A non-aqueous secondary battery comprising a sodium salt and a carbonate in the non-aqueous secondary battery.   The said sodium salt contains the quantity from which a sodium ion becomes 0.01 to 7 weight% with respect to the total weight of a positive electrode active material layer and a negative electrode active material layer. Non-aqueous secondary battery.   3. The carbonate according to claim 1, wherein the carbonate contains an amount of carbonate ions of 0.1 to 10 wt% with respect to a total weight of the positive electrode active material layer and the negative electrode active material layer. The nonaqueous secondary battery as described. The nonaqueous secondary battery according to any one of claims 1 to 3, wherein the nonaqueous electrolytic solution contains LiPF ₆ and a lithium salt other than LiPF ₆ .   5. The non-aqueous secondary battery according to claim 1, wherein a content of the acetonitrile is 30% by volume or more in the non-aqueous solvent.   The non-aqueous secondary battery according to claim 1, wherein the positive electrode active material contains at least one transition metal element selected from Ni, Mn, and Co. The capacity retention rate is 90% or more in the cycle characteristic evaluation at 50 ° C. of the non-aqueous secondary battery defined below. Water-based secondary battery.
The non-aqueous secondary battery is stored at 50 ° C. for 2 hours, and then charged with a constant current equivalent to 2 C to reach a battery voltage of 4.2 V, and then charged with a constant voltage of 4.2 V for a total of 2 hours, Discharge to 3.0V with a constant current corresponding to 2C. With this as the first charge / discharge cycle, 50 cycles of charge / discharge are performed, and the ratio of the discharge capacity after the end of 50 cycles to the discharge capacity of the first cycle is defined as the capacity maintenance rate.

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