JP6865555B2 - Non-aqueous secondary battery - Google Patents

Description

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

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

As the electrolyte for a room temperature operating lithium ion secondary battery, it is common to dissolve an electrolyte salt of a lithium salt in a non-aqueous electrolyte and use it. For example, an electrolytic solution in which a lithium salt containing fluorine is dissolved in a mixed solvent of a highly dielectric solvent such as a cyclic carbonic acid ester and a low-viscosity solvent such as a lower chain carbonic acid ester can be mentioned. Among the fluorine-containing lithium salts, LiPF ₆ is preferably used because of its high ionic conductivity, but when water is present in the system, the fluorine-containing anion is decomposed 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, which are generally used as positive electrode active materials, and damage batteries. In order to prevent this, the following studies have been made.

In Patent Document 1, in order to prevent dissolution and metal elution of the negative electrode current collector copper foil by acid, an organic and / or inorganic copper corrosion inhibitor, or an organic and / or inorganic copper trap. An inhibitor, which is an agent, is added. Examples of the inhibitor include 1,2,3-benzotriazole, or derivatives and analogs thereof.

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

Japanese Unexamined Patent Publication No. 2001-273927 Special Table 2009-517836

However, all of these techniques function as trapping agents for transition metals, and are not techniques for preventing metal elution itself. Further, aluminum foil is mainly used for the positive electrode current collector, and the copper trapping agent cannot obtain the corrosion prevention effect of the positive electrode current collector.

The present invention is a non _{-aqueous secondary battery containing LiPF 6} in a non-aqueous electrolyte solution, which suppresses corrosion of an Al current collector and reduction deterioration on a negative electrode at high temperature, and is excellent in long-term stability. The purpose is to provide a secondary battery.

The present invention that solves the above problems has the following configurations.

[1] A positive electrode having a positive electrode active material layer capable of storing / desorbing lithium on one side or both sides of an aluminum foil current collector, and a negative electrode active material layer capable of storing / desorbing lithium on one side or both sides of the current collector. A non-aqueous secondary battery comprising a negative electrode and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution contains a lithium-containing lithium salt, and the lithium-containing fluorine salt contains LiPF ₆ and LiPF 6. LiBF ₄ and lithium difluorooxalatoborate (Li [B (C ₂ O ₄ ) F _{2 ], hereinafter abbreviated as LiFOB) are included, and LiPF 6} is a fluorine-containing lithium salt contained in the non-aqueous electrolyte solution. The total molar content of _{LiBF 4} and LiFOB contained in the non-aqueous electrolyte solution, which is contained in the largest molar ratio and contains more _{LiFOB than LiBF 4} in the molar ratio of the fluorine-containing lithium salt. fraction, the non-aqueous secondary battery relative molar fraction, and wherein the 2.3～23Mol% der Rukoto of LiPF _6.

[2] The non-described in [1], wherein _{the total content of LiPF 6} , LiBF ₄ , and LiFOB contained in the non-aqueous electrolyte solution is 0.5 to 2.0 mol / L. Water-based secondary battery.

[ 3 ] The non-aqueous secondary battery according to [1] or [ 2 ] , wherein the non-aqueous electrolyte solution contains a lithium salt other than _{LiPF 6} , LiBF _{4, and LiFOB.}

[ 4 ] The non-aqueous secondary battery according to any one of [1] to [3 ], wherein acetonitrile is contained in the non-aqueous solvent contained in the non-aqueous electrolytic solution.

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

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

[7] The ratio of the discharge capacity of the current density 1.5mA / cm 15mA / cm ² for ² of the discharge capacity at 25 ° C. is in any one of [6] from [1], wherein 50% or more The non-aqueous secondary battery described.

According to the present invention, _{in a non-aqueous secondary battery containing LiPF 6} in a non-aqueous electrolytic solution, corrosion of an Al current collector and reduction deterioration on a negative electrode at a high temperature are suppressed, and long-term stability is excellent. A non-aqueous secondary battery can be provided.

It is a top view which shows typically an example of the non-aqueous secondary battery of this embodiment. FIG. 5 is a cross-sectional view taken along the line AA of the non-aqueous secondary battery of FIG.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The numerical range described by using "~" in the present specification includes the numerical values described before and after the numerical range.

<1. Overall configuration of non-aqueous secondary battery>
The electrolytic solution of the present embodiment can be used, for example, in a non-aqueous secondary battery. The non-aqueous secondary battery of the present embodiment includes, for example, a positive electrode having a positive electrode active material layer capable of occluding / desorbing lithium on one side or both sides of an aluminum foil current collector, and one side or both sides of the current collector. Examples thereof include a lithium ion secondary battery including a negative electrode having a negative electrode active material layer capable of occluding / removing lithium.

Specifically, the non-aqueous secondary battery of the present embodiment may be the non-aqueous secondary battery shown in FIGS. 1 and 2. Here, FIG. 1 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 2 is a 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 via a separator 170 in a space 120 formed inside a battery exterior 110 composed of two aluminum laminated films. It contains the body and a non-aqueous electrolyte solution (not shown). The outer peripheral portion of the battery exterior 110 is sealed by heat-sealing the upper and lower aluminum laminate films. The laminate in which the positive electrode 150, the separator 170, and the negative electrode 160 are laminated in this order is impregnated with a non-aqueous electrolytic solution. In addition, in FIG. 2, in order to avoid complicating the drawings, each layer constituting the battery exterior 110 and each layer of the positive electrode 150 and the negative electrode 160 are not shown separately.

The aluminum laminate film constituting the battery exterior 110 preferably has both sides of the aluminum foil coated with a 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 non-aqueous secondary battery 100. One end of each of the positive electrode lead body 130 and the negative electrode lead body 140 is pulled out to the outside of the battery exterior 110 so that they can be connected to an external device or the like, and their ionomer portions are 1 of the battery exterior 110. It is heat-sealed together with the sides.

In the non-aqueous secondary battery 100 shown in FIGS. 1 and 2, the positive electrode 150 and the negative electrode 160 each have one laminated electrode body, but the number of laminated positive electrodes 150 and 160 is determined by the capacity design. It can be increased as appropriate. In the case of a laminated electrode body having a plurality of positive electrodes 150 and 160 negative electrodes, 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. As the tabs having the same pole, a mode in which the exposed portion of the current collector is formed, a mode in which a metal piece is welded to the exposed portion of the current collector, and the like are possible.

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 arranged so that the positive electrode active material layer and the negative electrode active material layer face each other via the separator 170.

Hereinafter, the positive electrode and the negative electrode are collectively referred to as “electrode”, the positive electrode active material layer and the negative electrode active material layer are collectively referred to as “electrode active material layer”, and the positive electrode mixture and the negative electrode mixture are collectively referred to as “electrode mixture”.

As each of these members, as long as each requirement in the present embodiment is satisfied, a material provided in a conventional lithium ion secondary battery can be used, and for example, a material described later 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 contains at least a non-aqueous solvent (hereinafter, also simply referred to as “solvent”) and LiPF ₆ , LiBF ₄ , and lithium difluorooxalatoborate (LiFOB) as lithium salts.

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

_{Although LiPF 6} contained in the electrolytic solution has excellent ionic conductivity, it does not have sufficient thermal stability and has the property of easily hydrolyzing with a trace amount of water in the solvent to generate lithium fluoride and hydrogen fluoride. When LiPF ₆ is decomposed, _{the ionic conductivity of the electrolytic solution containing LiPF 6} is lowered, and the generated lithium fluoride and hydrogen fluoride corrode materials such as electrodes and current collectors, or decompose the solvent. It may have a fatal adverse effect on the battery. However, in the present embodiment, _{by coexisting LiBF 4} and LiFOB in addition to _{LiPF 6} , a protective film can be formed on the surface of the current collector of the positive electrode to prevent corrosion. Regarding the effect of lithium salt coexistence, <2-2. This will be described in detail in the section Lithium Salts>.

<2-1. Non-aqueous solvent>
The “non-aqueous solvent” as used in the present embodiment _{means a component obtained by removing LiPF 6} , LiBF ₄ , LiFOB, and a separate lithium salt to be added, if any, from the electrolytic solution. That is, when the electrolytic solution contains other additives described later, the solvent and the electrode protection additive are collectively referred to as a "non-aqueous solvent".

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

Specific examples of the aprotonic solvent include, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate. , Trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, and cyclic carbonates typified by vinylene carbonate; to fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and trifluoromethylethylene carbonate. Cyclic fluorinated carbonates represented; γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and lactone represented by ε-caprolactone; sulfolane, dimethylsulfoxide, and ethylene glycol sulfide. Sulfur compounds typified by; tetrahydrofuran, 2-methyl tetrahydrofuran, 1,4-dioxane, and cyclic ethers typified by 1,3-dioxane; ethylmethyl carbonate, dimethylcarbonate, diethylcarbonate, methylpropylcarbonate, methylisopropylcarbonate. , Dipropyl carbonate, methylbutyl carbonate, dibutyl carbonate, ethylpropyl carbonate, and chain carbonate represented by methyltrifluoroethyl carbonate; represented by trifluorodimethyl carbonate, trifluorodiethyl carbonate, and trifluoroethylmethyl carbonate. Chain fluorinated carbonates; mononitriles represented by acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, and acrylonitrile; alkoxy group-substituted nitriles represented by methoxynitrile and 3-methoxypropionitrile; malononitrile, skates. Sinonitrile, Glutaronitrile, Adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanooctane , 2,7-Dicyanooctane, 1,9-dicyanononane, 2,8-dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, and dinitrile typified by 2,4-dimethylglutaronitrile; benzo Cyclic nitrile represented by nitrile; substitute for methyl propionate Represented chain ester; chain ether typified by dimethoxyethane, diethyl ether, 1,3-dioxolane, diglime, triglime, and tetraglyme; Rf ^4- OR ⁵ (Rf ⁴ is a fluorine-containing alkyl group, R ⁵ is a fluorinated ether typified by an organic group that may contain fluorine); in addition to ketones typified by acetone, methyl ethyl ketone, and methyl isobutyl ketone, halides typified by these fluorinated compounds are used. Can be mentioned. These may be used alone or in combination of two or more.

Of these non-aqueous solvents, acetonitrile is preferably used. Acetonitrile may be used alone or may contain other aprotic solvents as described above. When an aprotic solvent other than acetonitrile is mixed and used, the content of acetonitrile is preferably 1 to 100% by volume, more preferably 30% by volume or more, more preferably 30% by volume or more, based on the total amount of the non-aqueous solvent. It is preferably 40% by volume or more, more preferably 70% by volume or more.

When the content of acetonitrile is 30% by volume or more, the ionic conductivity tends to increase and high output characteristics tend to be exhibited, and further, the 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.

As a combination of other aprotic solvents for acetonitrile, it is preferable to use one or more of cyclic carbonate and chain carbonate together with acetonitrile. Here, as the cyclic carbonate and the chain carbonate, only one of the above-exemplified ones may be selected and used, and two or more kinds (for example, two or more kinds of the above-exemplified cyclic carbonates, the above-mentioned Two or more of the exemplified chain carbonates, or one or more of the above-exemplified cyclic carbonates and two or more of the above-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 ethylmethyl carbonate, dimethyl carbonate, or diethyl carbonate is more preferable as the chain carbonate. And it is more preferable to use cyclic carbonate.

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

Acetonitrile is easily electrochemically reduced and decomposed. Therefore, it is preferable to mix this with another solvent and add an electrode protection additive for forming a protective film on the electrode at least one of them.

Acetonitrile has high ionic conductivity and can enhance the diffusivity of lithium ions in the battery. Therefore, when the electrolytic solution contains acetonitrile, especially in the positive electrode where the positive electrode active material layer is thickened to increase the filling amount of the positive electrode active material, lithium ions are difficult to reach during discharge under a high load. Lithium ions can be well diffused to the region near the body. Therefore, it is possible to draw out a sufficient capacity even at the time of high load discharge, and it is possible to obtain a non-aqueous secondary battery having excellent load characteristics.

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 charging characteristics of the non-aqueous secondary battery can also be enhanced. In the 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 solution, the CC charging area can be increased (CC charging time can be lengthened) and the charging current can be increased, so that the non-aqueous secondary battery can be charged. The time from the start to the fully charged state can be significantly shortened.

<2-2. Lithium salt>
The fluorine-containing lithium salt as the electrolyte salt in the present embodiment is characterized by containing LiPF ₆ , LiBF ₄ , and lithium difluorooxalatoborate (LiFOB). _{The total concentration of LiPF 6} , LiBF ₄ , and LiFOB in the non-aqueous electrolyte solution is preferably 0.5 to 2.0 mol / L. More preferably, it is 0.8 mol or more. Further, the total concentration of LiPF ₆ , LiBF ₄ , and LiFOB is more preferably about 1 to 2 mol / L. This value is preferably 15 mol or less, more preferably 4 mol or less, and further preferably 2.8 mol or less with respect to 1 L of the non-aqueous solvent. When the total content of the fluorine-containing lithium salt is within the above range, the ionic conductivity tends to increase and high output characteristics tend to be exhibited, and the storage characteristics and other battery characteristics can be further improved. There is a tendency.

Among the fluorine-containing lithium salts contained in the electrolytic solution, LiPF ₆ is contained in the largest molar fraction. This is because LiPF ₆ has good ionic conductivity. However, it is necessary to take measures to suppress the influence of hydrofluoric acid generation due to hydrolysis.

Fluorine-containing lithium salt reacts with generic aluminum as a positive electrode current collector, AlF ₃ are known to form a passivation film. By forming this passivation film, the surface of the aluminum current collector becomes corrosion resistant. However, since AlF ₃ is insulating, if the passivation film formed is too thick, it causes an increase in internal resistance. Therefore, it is preferable that AlF 3 is formed with an appropriate thickness and without defects. When _{only LiPF 6} is used, the thickness of the passivation film tends to be thicker than necessary due to the high reactivity of _{LiPF 6. By coexisting LiBF 4} and LiFOB here, it is possible to form a thin and highly uniform passivation film .

Further, the contents of LiBF ₄ and LiFOB are preferably more _{LiFOB than LiBF 4 in terms of mole fraction.} LiFOB contributes not only to the formation of the passivation film of the positive electrode current collector, but also to the formation of the surface film of the negative electrode active material. _{When LiBF 4} is contained in a larger amount than LiFOB, the reason is unknown, but there is a tendency that the formation of the SEI film on the surface of the negative electrode is inhibited.

The electrolytic solution may contain a fluorine-containing inorganic lithium salt other than _{LiPF 6} and LiBF _4. The "fluorine-containing inorganic lithium salt" refers to a lithium salt which does not contain a carbon atom in an anion but contains a fluorine atom in an anion and is soluble in a non-aqueous solvent. The fluorine-containing inorganic lithium salt in the present embodiment forms a passivation film on the surface of the metal foil which is the positive electrode current collector, and suppresses corrosion of the positive electrode current collector. Fluorine-containing inorganic lithium salts are excellent as electrolyte salts in terms of solubility, conductivity, and ionization. Specific examples of the fluorine-containing inorganic lithium salt used other than LiPF ₆ and LiBF _{4 include, for example, 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.

As the lithium salt that can be used in the present embodiment, in addition to the fluorine-containing inorganic lithium salt, the inorganic lithium salt used for the non-aqueous secondary battery and / or the organic lithium salt may be supplementarily added. The "inorganic lithium salt" refers to a lithium salt which does not contain a carbon atom in an anion and is soluble in a non-aqueous solvent. The "organolithium salt" is a lithium salt containing a carbon atom as an anion and soluble in a non-aqueous solvent.

Specific examples include, for example, an inorganic lithium salt containing no fluorine atom in an anion such as _{LiClO 4} , LiAlO ₄ , LiAlCl ₄ , LiB ₁₀ Cl _{10 , and 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₎ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ etc. LiN (SO ₂ C _m F _{2 m + 1} ) ₂ [m is an integer of 1 to 8] Organic lithium salt represented by; 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], an organic lithium salt represented by; _{LiBF q} (C) such as LiBF ₃ (CF _{3). s} F _{2s + 1} ) _4-q [q is an integer of 1-3, s is an integer of 1-8] Organic lithium salt; LiB (C ₂ O ₄ ) ₂ Lithium bis (oxalate) borate (LiBOB); LiBOB halide; Lithium oxalatodifluoroborate (LiODFB) represented by _{LiBF 2} (C ₂ O ₄ ); Lithium bis (malonate) borate represented by _{LiB (C 3} O ₄ H ₂ ) ₂ LiBMB); Lithium tetrafluorooxalat phosphate represented by _{LiPF 4} (C ₂ O ₄ ), organic lithium salts such as lithium difluorobis (oxalat) phosphate represented by _{LiPF 2} (C ₂ O ₄ ) _2, Lithium salt bonded to polyvalent anion; 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)
{In the formula, R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² may be the same or different from each other and contain perfluoroalkyl groups having 1 to 8 carbon atoms. Shown. }, And one or more of these can be used together with the fluorine-containing inorganic lithium salt.

In order to improve the load characteristics and charge / discharge cycle characteristics of the non-aqueous secondary battery, it is preferable to supplementally add an organolithium salt having an oxalic acid group, LiB (C ₂ O ₄ ) ₂ , LiPF ₄ ( It is particularly preferable to add at least one selected from the group consisting of C ₂ O ₄ ) and LiPF ₂ (C ₂ O ₄ ) _2. The organolithium salt having an oxalic acid group may be added to the non-aqueous electrolytic solution or contained in the negative electrode (negative electrode active material layer). These organolithium salts containing an oxalic acid group function as a film-forming agent on the surface of the negative electrode.

The amount of the organic lithium salt having a oxalic acid group added to the non-aqueous electrolyte solution is 0, as the amount of the non-aqueous electrolyte solution per 1 L of the non-aqueous solvent from the viewpoint of ensuring a better effect by its use. It 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 organolithium salt having an oxalic acid group in the non-aqueous electrolyte solution is too large, it may precipitate. Therefore, the amount of the organic lithium salt having an oxalic acid group added to the non-aqueous electrolyte solution is preferably less than 1.0 mol per 1 L of the non-aqueous solvent of the non-aqueous electrolyte solution. It is more preferably less than 5 mol and even more preferably less than 0.2 mol.

<2-3. Electrode protection additive ＞
The electrolytic solution in the present embodiment may contain an additive that protects the electrodes. The electrode protection additive is not particularly limited as long as it does not hinder the solution of the problem according to the present invention. It may substantially overlap with a substance (ie, the non-aqueous solvent described above) that serves as a solvent for dissolving the lithium salt. The electrode protection additive is preferably a substance that contributes to improving the performance of the electrolytic solution and the non-aqueous secondary battery in the present embodiment, but also includes a substance that is not directly involved in the electrochemical reaction.

Specific examples of the electrode protection additive include 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, and cis-4,5-difluoro. -1,3-Dioxolane-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4, Fluoroethylene carbonate typified 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 ε -Lactone typified by caprolactone; cyclic ether typified by 1,4-dioxane; ethylene sulphite, propylene sulphite, butylene sulphite, pentensulfite, sulfolane, 3-methylsulfolane, 1,3-propanesulton, Cyclic sulfur compounds typified by 1,4-butanesulton and tetramethylene sulfoxide can be mentioned. These may be used alone or in combination of two or more.

When acetonitrile is contained as a non-aqueous solvent, acetonitrile is easily chemically reduced and decomposed. Therefore, the non-aqueous solvent containing acetonitrile is a cyclic aprotic polar solvent as an additive for forming a protective film on the negative electrode. It is preferable to contain one or more kinds of cyclic carbonates, and more preferably one or more kinds of unsaturated bond-containing cyclic carbonates are contained.

The content of the electrode protection additive in the electrolytic solution in the present embodiment is not particularly limited. 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. Is even more preferable.

In the present embodiment, the larger the content of the electrode protection additive, the more the deterioration of the electrolytic solution can be suppressed. However, the smaller the content of the electrode protection additive, the better the high output characteristics of the non-aqueous secondary battery in a low temperature environment. Therefore, by adjusting the content of the electrode protection additive within the above 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. It tends to be able to be maximized. By preparing the electrolytic solution with such a composition, the cycle performance of the non-aqueous secondary battery, the high output performance in a low temperature environment, and other battery characteristics all 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, improving the high temperature storage property, improving the safety (for example, preventing overcharging, etc.), the non-aqueous electrolyte solution is, for example, sulfonic acid. Sulfonic acid ester, diphenyldisulfide, cyclohexylbenzene, biphenyl, fluorobenzene, tert-butylbenzene, phosphate ester [ethyldiethylphosphonoacetate (EDPA): (C ₂ H ₅ O) ₂ (P = O) -CH ₂ ( C = O) OC ₂ H ₅ , Trisyl Phosphate (Trifluoroethyl) (TFEP) :( CF ₃ CH ₂ O) ₃ P = O, Triphenyl Phosphate (TPP): (C ₆ H ₅ O) ₃ P = O, etc.], etc., and an optional additive selected from derivatives of each of these compounds and the like can be appropriately contained. In particular, the above-mentioned phosphate 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 acts 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 auxiliary agent and a binder.

The positive electrode active material layer preferably contains a material capable of occluding and releasing lithium ions as the positive electrode active material. The positive electrode active material layer preferably contains a conductive auxiliary agent and a binder together with the positive electrode active material, if necessary. When such a material is used, it tends to be possible to obtain a high voltage and a high energy density, which is preferable.

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 from 0 to 1.1, and y represents a number from 0 to 2. }, Lithium-containing compounds represented by each, and other lithium-containing compounds can be mentioned.

Examples of the lithium-containing compound represented by each of the general formulas (2a) and (2b) include lithium cobalt oxide represented by _{LiCoO 2 ; LiMnO 2} , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O ₄ . lithium manganese oxide represented; LiNiO lithium nickel oxide represented by _2; Li z _{MO 2} (M comprises Ni, Mn, and at least one transition metal element selected from Co, and, Ni, Mn , Co, Al, and Mg, indicating two or more kinds of metal elements, and z indicates a number of more than 0.9 and less than 1.2.) Lithium-containing composite metal oxides and the like represented by Can be mentioned.

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 having lithium, a metal phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element. silicic acid metal compound (e.g. _Li t _M u _SiO 4, _M have the same meanings as defined in formula (3a), t is the number of 0 to 1, u represents. a number of 0 to 2) it includes. 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), and chromium. 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 preferred.

More specifically, as the lithium-containing compound, a composite oxide containing lithium and a transition metal element, a metal chalcogenide containing lithium and a transition metal element, and a metal phosphate compound having lithium are more preferable, for example, the following, respectively. General formulas (3a) and (3b):
^{_{Li v M I D 2 (3a}} )
Li _w M ^II PO ₄ (3b)
{Wherein, D is an oxygen or chalcogen element, M ^I and M ^II is represents one or more transition metal elements each, the value of v and w is the charge and discharge state of the battery, v 0.05 ~ 1.10, w represents a number of 0.05 to 1.10. } Can be mentioned.

The lithium-containing compound represented by the above-mentioned general formula (3a) has a layered structure, and the compound represented by the above-mentioned general formula (3b) has an olivine structure. These lithium-containing compounds are those in which a part of the transition metal element is replaced with Al, Mg, or other transition metal elements for the purpose of stabilizing the structure, and these metal elements are included in the crystal grain boundary. It may be one in which a part of an oxygen atom is replaced with a fluorine atom or the like, or one in which at least a part of the surface of a positive electrode active material is coated with another positive electrode active material.

As the positive electrode active material in the present embodiment, only the above-mentioned lithium-containing compound may be used, or other positive electrode active materials 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; conductive polymers, and the like. Examples of metal oxides or metal chalcogenides 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. Examples thereof include oxides, sulfides, and serenes of metals other than lithium represented by _2. Examples of the conductive polymer include conductive polymers typified by polyaniline, polythiophene, polyacetylene, and polypyrrole.

The above-mentioned other positive electrode active materials may be used alone or in combination of two or more, and are not particularly limited. However, since lithium ions can be reversibly and stably occluded and released and a high energy density can be achieved, the positive electrode active material layer is at least one transition metal selected from Ni, Mn, and Co. It preferably contains an element.

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

Examples of the conductive auxiliary agent include graphite, acetylene black, carbon black typified by Ketjen black, and carbon fiber. The content ratio of the conductive auxiliary agent is preferably 10 parts by mass or less, and 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 fluororubber. The content ratio of the binder is preferably 6 parts by mass or less, and more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the positive electrode active material.

For the positive electrode active material layer, 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 auxiliary agent and a binder is dispersed in a solvent is applied to a positive electrode current collector and dried (solvent removal). ), And if necessary, it is formed by pressing. The solvent is not particularly limited, and conventionally known solvents 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.

Aluminum foil is used as the positive electrode current collector. The surface of the current collector may be coated with carbon 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 even 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 is formed by compressing the positive electrode active material layer obtained after drying by a roll press or the like. The thickness of the positive electrode mixture after compression is preferably 10 to 300 μm, more preferably 20 to 280 μm, and even 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 acts as a negative electrode of a non-aqueous secondary battery, and may be a known one.
The negative electrode active material layer preferably contains a conductive auxiliary agent and a binder together with the negative electrode active material, if necessary.

As the negative electrode active material, in addition to metallic lithium and lithium alloys, materials capable of dove and dedove lithium ions are used. Examples thereof include carbon materials, tin oxide, niobium oxide, vanadium oxide, titanium oxide, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), silicon, transition metal nitrogen oxides and the like. Among them, from the viewpoint of increasing the battery voltage, lithium ion is 0.4 V vs. It is preferable to use a material that can be occluded at a lower potential than Li / Li ^+. Such materials are carbon-based materials, such as amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, thermally decomposed carbon, coke, glassy carbon, calcined organic polymer compounds, mesocarbon microbeads. , Carbon fiber, activated carbon, graphite, carbon colloid, and carbon materials typified by carbon black. The negative electrode active material may be used alone or in combination of two or more.

Examples of the conductive auxiliary agent include graphite, acetylene black, carbon black typified by Ketjen black, and carbon fiber. The content ratio of the conductive auxiliary agent is preferably 20 parts by mass or less, and 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 fluororubber. The content ratio of the binder is preferably 10 parts by mass or less, and more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the negative electrode active material.

For the negative electrode active material layer, 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 auxiliary agent and a binder is dispersed in a solvent is applied to a negative electrode current collector and dried (solvent removal). It is formed by pressing as needed. The solvent is not particularly limited, and conventionally known solvents 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 composed of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. Further, the negative electrode current collector may have a carbon coat on its 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 even more preferably 7 to 30 μm.

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

<5. Separator>
The non-aqueous 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 preventing short circuits between the positive electrode 150 and the negative electrode 160 and imparting safety such as shutdown. As the separator 170, the same one as that provided in a known non-aqueous secondary battery may be used, and an insulating thin film having high ion permeability and excellent mechanical strength is preferable. Examples of the separator 170 include woven fabrics, non-woven fabrics, and microporous membranes made of synthetic resin. Among these, microporous membranes made of synthetic resin are preferable.

As the microporous membrane made of synthetic resin, for example, a microporous membrane containing polyethylene or polypropylene as a main component, or a polyolefin-based microporous membrane such as a microporous membrane containing both of these polyolefins is preferably used. Examples of the non-woven 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 structure in which one type of microporous membrane is laminated in a single layer or a plurality of types, or may be a structure in which two or more types of microporous membranes are laminated. The separator 170 may have a configuration in which two or more kinds of resin materials are melt-kneaded and laminated in a single layer or a plurality of layers using a mixed resin material.

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

The laminated film exterior is in a state in which two sheets are stacked with the hot-melt resin side facing inward, or bent so that the hot-melt resin side faces inward, and the ends are sealed by heat sealing. Can be used as an exterior body. When the laminated film exterior body is used, the positive electrode lead body 130 (or the 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) are connected to the negative electrode current collector. The lead tab to be connected may be connected. In this case, the laminated film outer body is sealed with the ends of the positive electrode lead body 130 and the negative electrode lead body 140 (or the lead tabs connected to the positive electrode terminal and the negative electrode terminal) pulled out to the outside of the outer body. May be good.

When an acetonitrile-based electrolytic solution is used, swelling of the laminate cell is likely to occur during heat sealing. It is preferably 15 to 40 mm. By setting the above distance, swelling of the cell can be prevented.

<7. Battery manufacturing method>
The non-aqueous secondary battery 100 in the present embodiment has the above-mentioned non-aqueous electrolyte solution, a positive electrode 150 having a positive electrode active material layer on one side or both sides of the current collector, and a negative electrode active material layer on one side or both sides of the current collector. It is produced by a known method using a negative electrode 160, a battery exterior 110, and a separator 170 if necessary.

First, a laminate composed of a positive electrode 150, a positive electrode 160, and a separator 170, if necessary, is formed. For example, an embodiment in which a long positive electrode 150 and a negative electrode 160 are wound in a laminated state in which the long separator is interposed between the positive electrode 150 and the negative electrode 160 to form a laminated body having a wound structure; the positive electrode 150. An embodiment of forming a laminated body having a laminated structure in which the positive electrode sheet 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 positive electrode body sheet and the negative electrode body sheet are alternately inserted between the zigzag-folded separators by folding the separator of the scale into pieces.

Next, the above-mentioned laminate is housed in the battery exterior 110 (battery case), the electrolytic solution according to the present embodiment is injected into the battery case, and the laminate is immersed in the electrolytic solution and sealed. The non-aqueous secondary battery according to the present embodiment can be manufactured.

Alternatively, a gel-like electrolyte membrane is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-shaped positive electrode 150, a negative electrode 160, an electrolyte membrane, and a separator 170 if necessary. After forming a laminated body having a laminated structure using the above, the non-aqueous secondary battery 100 can also be manufactured by accommodating it 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 square cylinder shape, a button shape, a coin shape, a flat shape, a laminated shape, and the like are preferably adopted.

It should be noted that the arrangement of the electrodes is such that there is a portion where the outer peripheral edge of the negative electrode active material layer and the outer peripheral edge 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. If the battery is designed as such, the charge / discharge cycle characteristics of the non-aqueous secondary battery may deteriorate due to the displacement of the electrodes during battery assembly. Therefore, in the electrode body used for the non-aqueous secondary battery, it is preferable to fix the position of the electrode in advance with a tape such as a polyimide tape, a polyphenylene sulfide tape, a 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 charging, but is stabilized by decomposing a part of the electrolytic solution during the initial charging. The method of initial charging is not particularly limited, but the initial charging is preferably performed at 0.001 to 0.3C, more preferably 0.002 to 0.25C, and 0.003 to 0.2C. It is more preferable to be carried out in. It is also preferable that the initial charging is performed via constant voltage charging on the way. The constant current that discharges the rated capacity in 1 hour is 1C. By setting a long voltage range in which the lithium salt is involved in the electrochemical reaction, SEI is formed on the electrode surface, which has the effect of suppressing an increase in internal resistance including the positive electrode 150, as well as a reaction product. Is not firmly fixed only to the negative electrode 160, but somehow gives a good effect to members other than the negative electrode 160, such as the positive electrode 150 and the separator 170. Therefore, it is very effective to perform the initial charging in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte solution.

The non-aqueous secondary battery 100 in the present embodiment can also be used as a battery pack in which a plurality of non-aqueous secondary batteries 100 are connected in series or in parallel. From the viewpoint of controlling the charge / discharge state of the battery pack, the working voltage range per battery pack is preferably 2 to 5 V, more preferably 2.5 to 5 V, and preferably 2.75 V to 5 V. Especially preferable.

Although the embodiment for carrying out the present invention has been described above, the present invention is not limited to the above-described embodiment. The present invention can be modified in various ways without departing from the gist thereof.

Hereinafter, the present invention will be described in more detail by way of examples. Various evaluations were carried out as follows.

(1) Preparation of positive electrode A composite oxide of lithium, nickel, manganese and cobalt (LiNi _0.5 Mn _0.2 Co _0.3 O ₂ ) as a positive electrode active material, acetylene black powder as a conductive auxiliary agent, and a binder. Vinylidene fluoride (PVdF) was mixed at a mass ratio of 100: 3.5: 3 to obtain a positive electrode mixture. N-Methyl-2-pyrrolidone was added as a solvent to the obtained positive electrode mixture and further mixed to prepare a positive electrode mixture-containing slurry. This positive electrode mixture-containing slurry was applied to an aluminum foil having a thickness of 15 μm, which serves as a positive electrode current collector, on one side of the aluminum foil while adjusting ^{the basis weight to about 95.0 g / m 2.} When the positive electrode mixture-containing slurry was applied to the aluminum foil, an unapplied region was formed so that a part of the aluminum foil was exposed. Then, by rolling with a roll press so that the density of the positive electrode active material layer was 1.90 g / cm ³ , a positive electrode composed of the positive electrode active material layer and the positive electrode current collector was obtained.

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

(2-1) Preparation of Graphite Negative Electrode A graphite as a negative electrode active material, carboxymethyl cellulose as a binder, and styrene butadiene latex are mixed at a mass ratio of 100: 1.1: 1.5, and an appropriate amount of water is further added. After the addition, the mixture was thoroughly mixed to prepare a slurry containing a negative electrode mixture. This slurry was applied to one side of a copper foil having a thickness of 10 μm with a constant thickness. When the negative electrode mixture-containing slurry was applied to the copper foil, an unapplied region was formed so that a part of the copper foil was exposed. Then, by rolling with a roll press so that the density of the negative electrode active material layer was 1.20 g / cm ³ , a negative electrode composed of the negative electrode active material layer and the negative electrode current collector was obtained.

Next, this 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 a nickel lead piece for extracting an electric current to the exposed portion of the copper foil. Was welded and vacuum dried at 80 ° C. for 12 hours to obtain a negative electrode with a lead.

_{(2-2) Preparation of LTO Negative Electrode Li 4} Ti ₅ O ₁₂ (density 3.30 g / cm ³ ) with a number average particle diameter of 7.4 μm, which is a negative electrode active material, and acetylene with a number average particle diameter of 48 nm as a conductive aid. Black (density 1.95 g / cm ³ ) and polyvinylidene fluoride (PVdF; density 1.75 g / cm ³ ) as a binder are mixed at a mass ratio of 82.0: 8.0: 10.0, and the negative electrode is used. Obtained a mixture. N-Methyl-2-pyrrolidone as a solvent was added to the obtained negative electrode mixture so as to have a solid content of 45% by mass and further mixed to prepare a negative electrode mixture-containing slurry. This slurry was applied to one side of a copper foil having a thickness of 10 μm with a constant thickness. When the negative electrode mixture-containing slurry was applied to the copper foil, an unapplied region was formed so that a part of the copper foil was exposed. Then, by rolling with a roll press so that the density of the negative electrode active material layer was 1.86 g / cm ³ , a negative electrode composed of the negative electrode active material layer and the negative electrode current collector was obtained.

Next, this 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 a nickel lead piece for extracting an electric current to the exposed portion of the copper foil. Was welded and vacuum dried at 80 ° C. for 12 hours to obtain a negative electrode with a lead.

(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, and this laminated electrode body is used. , 90 mm × 80 mm aluminum laminate sheet was housed in the outer body and vacuum dried at 80 ° C. for 5 hours to remove water. Subsequently, after injecting the electrolytic solution into the outer body, the outer body is sealed, and the single-layer laminated non-aqueous secondary battery having the appearance shown in FIG. 1 and the cross-sectional structure shown in FIG. 2 (hereinafter, simply "single"). A layer-laminated battery) was produced. This single-layer laminated battery has a rated current value of 23 mAh and a rated voltage value of 4.2 V.

(4) Evaluation of Single-Layer Laminated Battery The single-layer laminated battery obtained as described above was first charged and discharged according to the procedure of (4-1) below. Next, the formation state of the positive electrode current collector passivation film was evaluated according to the following procedure (4-2), and the output characteristics were evaluated according to the following procedure (4-3). Charging / discharging was performed using a charging / discharging device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a constant temperature bath PLM-73S (trade name) manufactured by Futaba Kagaku Co., Ltd.

Here, 1C means a current value that is expected to discharge a fully charged battery at a constant current and complete the discharge 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 complete the discharge in 1 hour.

(4-1) Initial charge / discharge treatment of a single-layer laminated battery The ambient temperature of the single-layer laminated battery is set to 25 ° C., and the battery is charged with a constant current of 1.125 mA corresponding to 0.05 C, and the battery voltage is 4.2 V. After charging until the temperature reached, charging was performed with a constant current of 4.2 V for a total of 3 hours. After that, it was discharged to 3.0 V with a constant current of 7.5 mA corresponding to 0.3 C.

(4-2) Evaluation of formation state of positive electrode current collector passivation film After the treatment of (4-1), the battery was disassembled in the Ar box. The removed positive electrode was washed with tetrahydrofuran and then with water in the air, and the positive electrode active material layer was peeled off with N-methyl-2-pyrrolidone. After drying, the weight of the aluminum foil measured in advance was subtracted, and the weight of the substance remaining on the current collector aluminum foil was measured as a passivation film. The thickness of the passivation film formed on the current collector was calculated with the specific gravity of the residue being 2 g / cm ^3.

(4-3) Output characteristics (discharge capacity retention rate)
Each single-layer laminated battery obtained in Example 2 and Comparative Example 2 described below was constantly charged to 4.2 V at a current value of ^{0.5 mA / cm 2 at 25 ° C., and then charged for 1 hour 4 times.} Constant voltage charging was performed at .2 V. For each single-layer laminated battery after charging, discharge at a constant current until it reaches 3.0 V at each current value of ^{1.5 mA / cm 2} and 15 mA / cm ^{2, and measure the discharge capacity at each current value.} did.

Then, a value obtained by dividing the discharge capacity retention ratio in discharge capacity of the discharge capacity of 15 mA / cm ² of 1.5 mA / cm ^2, expressed as a percentage.

(5) Li immersion test Since the formation state of the negative electrode surface SEI differs depending on the composition of the electrolytic solution, the following simple evaluation was carried out. A Li metal leaf (thickness 200 μm, 3 mm square) was immersed in 5 ml of an electrolytic solution having a composition to be evaluated, and stored at 50 ° C. for 7 days in an Ar atmosphere. When Li metal is eluted and the electrolytic solution is colored due to poor SEI formation, it is evaluated as "x (defective)", and when SEI formation is good, Li metal is not eluted and the electrolytic solution is not colored. Was "○ (good)".

[Examples and Comparative Examples]
An electrolytic solution prepared by dissolving Li salt in a non-aqueous solvent of acetonitrile / propylene carbonate / vinylene carbonate / ethylene sulfide = 47/38/11/4 (volume ratio) so as to have the concentration shown in Table 1 was prepared and used in Examples. And incorporated into the battery of the comparative example. In Example 1, Comparative Example 1 and Comparative Example 3, Li ₄ Ti ₅ O ₁₂ (hereinafter abbreviated as LTO) was used as the negative electrode active material, and in Example 2 and Comparative Example 2, graphite was used as the negative electrode active material. Table 1 shows the thickness of the positive electrode current collector passivation film of these batteries and the results of a simple evaluation of the negative electrode surface SEI formation state in the electrolytic solution having these compositions.

In Comparative Example 1, when the battery was disassembled after the initial charge / discharge treatment of (4-1), it was confirmed that the positive electrode active material layer was peeled off from the current collector. This peeling is caused by the thickening of the passivation film, and suggests an increase in the internal resistance value.

Further, there are Example 2 in which good Al passivation is formed and the result of the Li immersion test is also good, and Comparative Example in which the result of the Li immersion test is poor although good Al passivation is formed. For 2, (4-3) was compared. The results are shown in Table 2.

From the above results, in the non-aqueous secondary battery using the electrolytic solution of the present embodiment, the passivation film on the surface of the positive electrode current collector is well formed, and the negative electrode surface SEI is also well formed. It was found that the internal resistance was low and the storage deterioration due to the reduction deterioration on the negative electrode at high temperature was reduced.

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

100 Non-aqueous secondary battery 110 Battery exterior 120 (of battery exterior 110) Space 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 capable of occluding / desorbing lithium on one side or both sides of an aluminum foil current collector, and a positive electrode.
A negative electrode having a negative electrode active material layer capable of occluding / desorbing lithium on one side or both sides of the current collector, and a negative electrode.
A non-aqueous secondary battery comprising a non-aqueous electrolyte solution.
Fluorine-containing lithium salt is contained in the non-aqueous electrolyte solution,
The fluorine-containing lithium salt contains LiPF ₆ , LiBF ₄ , and lithium difluorooxalatoborate (Li [B (C ₂ O ₄ ) F ₂ ], hereinafter abbreviated as LiFOB).
The fluorine-containing lithium salt contained in the non-aqueous electrolyte solution contains LiPF ₆ at the highest mole fraction and contains more _{LiFOB than LiBF 4} at the mole fraction of the fluorine-containing lithium salt .
The total molar fraction of _{LiBF 4} and LiFOB contained in the non-aqueous electrolyte solution is 2.3 to 23 mol% with respect to the molar fraction of _{LiPF 6.} Next battery. The non-aqueous secondary according to claim 1, wherein the total content of _{LiPF 6} , LiBF ₄ , and LiFOB contained in the non-aqueous electrolyte solution is 0.5 to 2.0 mol / L. battery. The non-aqueous secondary battery according to claim 1 or 2 , wherein the non-aqueous electrolyte solution contains a lithium salt other than _{LiPF 6} , LiBF _{4, and LiFOB.} The non-aqueous secondary battery according to any one of claims 1 to 3 , wherein acetonitrile is contained in the non-aqueous solvent contained in the non-aqueous electrolytic solution. The content of acetonitrile nonaqueous solvents, the nonaqueous secondary battery according to請Motomeko 4, wherein at 30% by volume or more of the non-aqueous solvent. The non-aqueous secondary battery according to any one of claims 1 to 5 , wherein the positive electrode active material layer contains at least one transition metal element selected from Ni, Mn, and Co. The ratio of the discharge capacity of 1.5mA / cm 15mA / cm ² for ² of the discharge capacity at 25 ° C. is nonaqueous secondary according to any one of claims 1 to 6, characterized in that less than 50% Next battery.

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