JP2022047197A - Non-aqueous electrolyte and non-aqueous secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte and a non-aqueous secondary battery capable of suppressing degradation of a positive electrode active material with a high Ni ratio and of suppressing decomposition of acetonitrile solvent by reducing a Lewis acid catalyst activity of PF5 included in LiPF6, and further, of being actuated at a high current density with stability by facilitating formation of a negative electrode SEI with a high durability against acetonitrile and its decomposition products.SOLUTION: Provided is a non-aqueous electrolyte containing a non-aqueous solvent and LiPF6. The non-aqueous solvent contains acetonitrile, vinylene carbonate, and ethylene sulfite, a volume ratio of vinylene carbonate being smaller than that of ethylene sulfite. The non-aqueous electrolyte further contains diphenyldialkoxysilane.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-aqueous electrolyte solution and a non-aqueous secondary battery using the same.

The use of lithium-ion batteries, which were used as single cells for mobile and IT, is changing drastically in the global trend of electrification of automobiles. In-vehicle batteries are required to both reduce the amount of cobalt used and improve the energy density, and several techniques for mastering the chemically unstable nickel (Ni) -based positive electrode active material have been reported.

For example, in Non-Patent Document 1 below, for a lithium ion battery using LiNi _0.6 Co _0.2 Mn _0.2 O ₂ for the positive electrode, diphenyldimethoxysilane is added to the non-aqueous electrolyte solution. It has been reported that charge / discharge cycle performance is improved. Further, in Patent Document 1 below, a lithium ion battery capable of improving cycle characteristics and initial charge / discharge characteristics by containing at least one of an alkoxysilane compound and a hydrolyzate thereof in a negative electrode active material is reported. Has been done.

Japanese Unexamined Patent Publication No. 2011-12404

Electrochimica Acta 236 (2017) 61-71

However, in Non-Patent Document 1 and Patent Document 1, the diffusion of lithium ions is rate-determining, but the conventional non-aqueous electrolytic solution to which a resistance component such as a dialkoxysilane compound is added inhibits the diffusion in the electrode layer. However, the performance when operating a non-aqueous secondary battery with a high current density was sacrificed.

The present invention has been made in view of the above circumstances, and is a non-aqueous electrolyte solution and a non-aqueous system capable of suppressing deterioration of a positive electrode active material having a high nickel (Ni) ratio and operating at a high current density. The purpose is to provide a secondary battery.

As a result of diligent research and repeated experiments to solve the above problems, the present inventors have conducted problems on the positive electrode side and the negative electrode side of the non-aqueous secondary battery in the non-aqueous electrolyte solution containing a specific silane compound and acetonitrile. We have found that the non-aqueous secondary batteries can be stably operated with a high current density, and have completed the present invention.

That is, the present invention is as follows.
[1] A non-aqueous electrolyte solution containing a non-aqueous solvent and LiPF ₆ .
The non-aqueous solvent contains acetonitrile, vinylene carbonate, and ethylene sulphite, and the volume ratio of vinylene carbonate is smaller than the volume ratio of ethylene sulphite.
Further, a non-aqueous electrolytic solution containing diphenyldialkoxysilane.
[2] The non-aqueous electrolyte solution according to the above [1], wherein the content of acetonitrile in the non-aqueous solvent is 5 to 97% by volume with respect to the total amount of the non-aqueous solvent.
[3] The content of the diphenyldialkoxysilane is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous solvent, according to the above [1] or [2]. The non-aqueous electrolyte solution described.
[4] The non-aqueous electrolytic solution according to any one of [1] to [3] above, wherein the diphenyldialkoxysilane is diphenyldimethoxysilane.
[5] A positive electrode having a positive electrode active material layer on one side or both sides of the current collector, a negative electrode having a negative electrode active material layer on one side or both sides of the current collector, a separator, and any of the above [1] to [4]. In the non-aqueous secondary battery provided with the non-aqueous electrolytic solution according to item 1,
The positive electrode active material layer has the following general formula (1):
Li _p Ni _q Co _r Mn _s M _t O _u ... (1)
{In the formula, M is aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn). ), Molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and is at least one metal selected from the group consisting of 0 <p <1.3, 0 <q <. In the range of 1.2, 0 <r <1.2, 0 ≦ s <0.5, 0 ≦ t <0.3, 0.7 ≦ q + r + s + t ≦ 1.2, 1.8 <u <2.2 Yes, and p is a value determined by the charge / discharge state of the battery. }
A non-aqueous secondary battery containing at least one selected from the group consisting of lithium-containing metal oxides represented by.
[6] The non-aqueous battery according to the above [5], wherein the lithium (Ni) content ratio q of the lithium-containing metal oxide represented by the general formula (1) is 0.5 <q <1.2. Next battery.

According to the present invention, the hydrogen fluoride (HF) trapping effect of diphenyldialkoxysilane suppresses the deterioration of the positive electrode active material having a high nickel (Ni) ratio, and the Lewis acid catalyst of PF ₅ contained in LiPF ₆ is suppressed. It is possible to reduce the activity and suppress the decomposition of the acetonitrile solvent that contributes to high ionic conductivity. Further, according to the present invention, the formation of a negative electrode SEI (Solid Electrolyte Interface) having high durability against acetonitrile and its decomposition products is promoted, so that the non-aqueous electrolyte can be stably operated at a high current density. Liquid and non-aqueous secondary batteries can be provided.

It is a top view which shows typically an example of the non-aqueous secondary battery of this embodiment. FIG. 3 is a cross-sectional view taken along the line AA of FIG.

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

<Non-water-based secondary battery>
The non-aqueous secondary battery of the present embodiment is a secondary battery including the above-mentioned non-aqueous electrolytic solution together with a positive electrode and a negative electrode, and may be, for example, a lithium ion battery, and more specifically, it is schematically shown in FIG. It may be a lithium ion battery whose plan view is shown in FIG. 2 and a sectional view is shown schematically in FIG. The lithium ion battery 100 shown in FIGS. 1 and 2 has a separator 170, a positive electrode 150 and a negative electrode 160 sandwiching the separator 170 from both sides, and a positive electrode lead sandwiching a laminate of them (separator 170, positive electrode 150, and negative electrode 160). A body 130 (connected to the positive electrode 150), a negative electrode lead body 140 (connected to the negative electrode 160), and a battery exterior 110 accommodating them are provided. The laminate in which the positive electrode 150, the separator 170, and the negative electrode 160 are laminated is impregnated with the non-aqueous electrolytic solution according to the present embodiment.

<1. Non-aqueous electrolyte>
The "non-aqueous electrolyte solution" in the present embodiment refers to a non-aqueous electrolyte solution in which water is 1% by mass or less and contains a non-aqueous solvent and LiPF ₆ with respect to the total amount of the non-aqueous electrolyte solution. The non-aqueous electrolytic solution according to the present embodiment preferably contains as little water as possible, 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 300 mass ppm or less, preferably 200 mass ppm or less, as the amount per total amount of the non-aqueous electrolytic solution. As for the non-aqueous electrolyte solution, as long as it has a configuration for achieving the solution to the problem of the present invention, as for other components, the constituent materials in the known non-aqueous electrolyte solution used for the lithium ion battery may be appropriately used. Can be selected and applied.

<1-1. Non-aqueous solvent>
The "non-aqueous solvent" as used in the present embodiment means an element obtained by removing a lithium salt and various additives from the non-aqueous electrolyte solution. When the non-aqueous electrolyte solution contains an electrode protection additive, the "non-aqueous solvent" is an element obtained by removing the lithium salt and the additive other than the electrode protection additive from the non-aqueous electrolyte solution. To say. Examples of the non-aqueous solvent include alcohols such as methanol and ethanol; aprotic solvents and the like. Among them, the aprotic solvent is preferable as the non-aqueous solvent. The non-aqueous solvent may contain a solvent other than the aprotic solvent as long as it does not hinder the solution of the problem of the present invention.

The non-aqueous solvent according to the non-aqueous electrolyte solution of the present invention contains acetonitrile as an aprotic solvent. Since the non-aqueous solvent contains acetonitrile, the ionic conductivity of the non-aqueous electrolyte solution is improved, so that the diffusivity of lithium ions in the battery can be enhanced. Therefore, when the non-aqueous electrolyte solution contains acetonitrile, lithium ions are difficult to reach even in a positive electrode in which the positive electrode active material layer is thickened to increase the filling amount of the positive electrode active material, especially when discharging under a high load. Lithium ions can be well diffused to the nearby region. As a result, 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.

Further, since the non-aqueous solvent contains acetonitrile, the quick charging 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 solution, the CC charging area can be increased (CC charging time can be lengthened) and the charging current can be increased. Therefore, from the start of charging the non-aqueous secondary battery. The time required to fully charge the battery can be significantly reduced.

Acetonitrile is easily electrochemically reduced and decomposed. Therefore, when acetonitrile is used, an electrode protection additive for forming a protective film on the electrode may be used in combination with acetonitrile as a non-aqueous solvent (for example, an aprotic solvent other than acetonitrile). It is preferable to add.

The content of acetonitrile in the non-aqueous solvent is preferably 5 to 97% by volume with respect to the total amount of the non-aqueous solvent. The lower limit of the content of acetonitrile is more preferably 10% by volume or more, still more preferably 20% by volume or more, based on the total amount of the non-aqueous solvent. The upper limit of the content of acetonitrile is more preferably 85% by volume or less, and further preferably 66% by volume or less, based on the total amount of the non-aqueous solvent. When the content of acetonitrile is 5% by volume or more with respect to the total amount of the non-aqueous solvent, the ionic conductivity of the non-aqueous electrolyte solution tends to increase, and the high output characteristics of the non-aqueous secondary battery tend to be exhibited. Furthermore, it is possible to promote the dissolution of the lithium salt. Further, when the content of acetonitrile in the non-aqueous solvent is within the above range, the high temperature cycle characteristics of the non-aqueous secondary battery and other battery characteristics are further improved while maintaining the excellent performance of acetonitrile. Tend to be able to.

Examples of the aprotic solvent other than acetonitrile include cyclic carbonate, fluoroethylene carbonate, lactone, organic compound having a sulfur atom, chain fluorinated carbonate, cyclic ether, mononitrile other than acetonitrile, alkoxy group substituted nitrile, dinitrile, and the like. Examples thereof include cyclic nitriles, short-chain fatty acid esters, chain ethers, fluorinated ethers, ketones, compounds in which part or all of the H atoms of the aprotonic solvent are replaced with halogen atoms, and the like.

Since acetonitrile, which is a component of a non-aqueous solvent, is easily electrochemically reduced and decomposed, the non-aqueous electrolyte solution according to this embodiment contains vinylene carbonate and ethylene sulfide in addition to acetonitrile in the non-aqueous solvent. Moreover, the volume ratio of vinylene carbonate is smaller than the volume ratio of ethylene sulphite.

When the non-aqueous solvent according to the present embodiment contains acetonitrile, vinylene carbonate as the cyclic carbonate, and ethylene sulfide as the organic compound having a sulfur atom, the non-aqueous electrolyte solution is used for the non-aqueous secondary battery. In addition, it suppresses the deterioration of the positive electrode active material having a high nickel (Ni) ratio, and operates the battery with a high current density.

Since the negative electrode protective film derived from vinylene carbonate has high resistance, it tends to lead to rapid charging, performance deterioration in a low temperature environment, and swelling of the battery due to gas generation during decomposition. Ethylene sulfite has a lower minimum empty orbital (LUMO) level than other oxygen-containing / sulfur compounds, and can be reduced and decomposed at a lower potential than vinylene carbonate to form a negative electrode protective film. It is possible to solve the problem of the negative electrode protective film derived from vinylene carbonate by reducing the addition amount of vinylene carbonate. Further, the negative electrode protective film derived from ethylene sulfide has low resistance in a wide temperature range, and further promotes the formation of a negative electrode SEI (Solid Electrolyte Interface) having high durability against acetonitrile and its decomposition products. It is possible to provide a non-aqueous electrolyte solution and a non-aqueous secondary battery capable of stable operation at a high current density.

When the total content of vinylene carbonate and ethylene sulfate in the non-aqueous electrolyte solution in the present embodiment is 0.1% by volume or more and less than 10% by volume with respect to the total amount of the non-aqueous solvent, the internal resistance increases. It is preferable from the viewpoint of suppressing.

Examples of the cyclic carbonate include 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, vinylene carbonate, 4,5-dimethylvinylene carbonate, and vinylethylene carbonate;

Examples of the fluoroethylene carbonate include 4-fluoro-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolane-2-one, and cis-4,5-difluoro-1,3-. Dioxolane-2-one, trans-4,5-difluoro-1,3-dioxolane-2-one, 4,4,5-trifluoro-1,3-dioxolane-2-one, 4,4,5,5 -Tetrafluoro-1,3-dioxolane-2-one and 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one;

The lactones include γ-butyrolactone, α-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone;

Examples of the organic compound having a sulfur atom include ethylene sulfoxide, propylene sulfite, butylene sulfite, pentensulfite, sulfolane, 3-sulfolene, 3-methylsulfolane, 1,3-propanesultone, and 1,4-butanesultone. , 1-Propene 1,3-Sultone, Dimethyl Sulfoxide, Tetramethylene Sulfoxide, and Ethylene Glycol Sulfite;

Examples of the chain carbonate include ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and diisobutyl carbonate;

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane;

Examples of mononitriles other than acetonitrile include propionitrile, butyronitrile, valeronitrile, benzonitrile, and acrylonitrile;

Examples of the alkoxy group-substituted nitrile include methoxyacetonitrile and 3-methoxypropionitrile;

Examples of the dinitrile include malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, and 2,6-. Dicyanoheptane, 1,8-dicyanooctane, 2,7-dicyanooctane, 1,9-dicyanononane, 2,8-dicyanononan, 1,10-dicyanodecane, 1,6-dicyanodecane, and 2,4-dimethylglue Taronitrile;

As the cyclic nitrile, for example, benzonitrile;

Examples of short chain fatty acid esters include methyl acetate, methyl propionate, methyl isobutyrate, methyl butyrate, methyl isovalerate, methyl valerate, methyl pivalate, methyl hydroangelica, methyl caproate, ethyl acetate, and propionic acid. Ethyl, ethyl isobutyrate, ethyl butyrate, ethyl isovalerate, ethyl valerate, ethyl pivalate, ethyl hydroangelica, ethyl caproate, propyl acetate, propyl propionate, propyl isobutyrate, propyl butyrate, propyl isovalerate, Valerate propyl, propyl pivalate, propyl hydroangelica, propyl caproate, isopropyl acetate, isopropyl propionate, isopropyl isobutyrate, isopropyl butyrate, isopropyl isovalerate, isopropyl valerate, isopropyl pivalate, isopropyl hydroangelica, capron Isopropyl acid, butyl acetate, butyl propionate, butyl isobutyrate, butyl butyrate, butyl isovalerate, butyl valerate, butyl pivalate, butyl hydroangelica, butyl caproate, isobutyl acetate, isobutyl propionate, isobutyl isobutyrate, Isobutyl butyrate, isobutyl isovalerate, isobutyl valerate, isobutyl pivalate, isobutyl hydroangelic acid, isobutyl caproate, tert-butyl acetate, tert-butyl propionate, tert-butyl isobutyrate, tert-butyl butyrate, isovaleric acid tert-butyl, tert-butyl valerate, tert-butyl pivalate, tert-butyl hydroangelica, and tert-butyl caproate;

Examples of the chain ether include dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme;

Examples of the fluorinated ether include Rf ²⁰ -OR ²¹ (in the formula, Rf ²⁰ represents an alkyl group containing a fluorine atom, and R ⁷ represents a monovalent organic group containing a fluorine atom. .);

Ketones include, for example, acetone, methyl ethyl ketone, and methyl isobutyl ketone;

Examples of the compound in which a part or all of the H atom of the aprotic solvent is replaced with a halogen atom include a compound in which the halogen atom is fluorine;
Can be mentioned.

Here, examples of the fluorinated product of the chain carbonate include methyl trifluoroethyl carbonate, trifluorodimethyl carbonate, trifluorodiethyl carbonate, trifluoroethyl methyl carbonate, methyl 2,2-difluoroethyl carbonate, and methyl 2,2. Examples thereof include 2-trifluoroethyl carbonate and methyl 2,2,3,3-tetrafluoropropyl carbonate. The above fluorinated chain carbonate has the following general formula:
R ⁷ -OC (O) OR ⁸
{In the formula, R ⁷ and R ⁸ are at least one selected from the group consisting of CH ₃ , CH ₂ CH ₃ , CH ₂ CH ₂ CH ₃ , CH (CH ₃ ) ₂ , and CH ₂ Rf ⁹ . , Rf ⁹ is an alkyl group having 1 to 3 carbon atoms in which a hydrogen atom is substituted with at least one fluorine atom, and R ⁷ and / or R ⁸ contains at least one fluorine atom. }
Can be represented by.

Fluorides of short-chain fatty acid esters include, for example, fluorine represented by 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetic acid, and 2,2,3,3-tetrafluoropropyl acetate. Examples include short-chain fatty acid esters. The fluorinated short-chain fatty acid ester has the following general formula:
R ¹⁰ -C (O) O-R ¹¹
{In the formula, R ¹⁰ is CH ₃ , CH ₂ CH ₃ , CH ₂ CH ₂ CH ₃ , CH (CH ₃ ) ₂ , CF ₃ CF ₂ H, CFH ₂ , CF ₂ Rf ¹² , CFHRf ¹² , and CH ₂ . At least one selected from the group consisting of Rf ¹³ , where R ¹¹ is from the group consisting of CH ₃ , CH ₂ CH ₃ , CH ₂ CH ₂ CH ₃ , CH (CH ₃ ) ₂ , and CH ₂ Rf ¹³ . At least one selected, Rf ¹² is an alkyl group having 1 to 3 carbon atoms in which a hydrogen atom may be substituted with at least one fluorine atom, and Rf ¹³ has a hydrogen atom having at least one fluorine atom. It is a substituted alkyl group with 1-3 carbon atoms, and if R ¹⁰ and / or R ¹¹ contains at least one hydrogen atom and R ¹⁰ is CF ₂ H, then R ¹¹ is not CH ₃ . .. }
Can be represented by.

As the aprotic solvent other than acetonitrile in this embodiment, one kind may be used alone, or two or more kinds may be used in combination.

As the non-aqueous solvent in the present embodiment, it is preferable to use one or more of cyclic carbonate and chain carbonate together with acetonitrile from the viewpoint of improving the stability of the non-aqueous electrolyte solution. From this point of view, as the non-aqueous solvent in the present embodiment, it is more preferable to use cyclic carbonate together with acetonitrile, and it is further preferable to use both cyclic carbonate and chain carbonate together with acetonitrile.

When cyclic carbonate other than vinylene carbonate is used together with acetonitrile, it is particularly preferable that the cyclic carbonate contains ethylene carbonate and / or fluoroethylene carbonate.

<1-2. Electrolyte salt>
The non-aqueous electrolyte solution of the present embodiment may contain LiPF ₆ , and other electrolyte salts are not particularly limited. For example, in this embodiment, the lithium salt contains LiPF ₆ and a lithium-containing imide salt.

The lithium-containing imide salt is a lithium salt represented by LiN (SO ₂ Cm F _{2m + 1} ) ₂ [in the formula, _m is an integer of 0 to 8], and specifically, LiN (SO ₂ F). ) ₂ and LiN (SO ₂ CF ₃ ) ₂ are preferably contained. Only one of these imide salts may be contained or both may be contained. Alternatively, it may contain an imide salt other than these imide salts.

When the non-aqueous solvent contains acetonitrile, the saturation concentration of the lithium-containing imide salt with respect to acetonitrile is higher than the saturation concentration of LiPF ₆ , so that the lithium-containing imide salt is contained at a molar concentration of LiPF ₆ ≤ lithium-containing imide salt. However, it is preferable because it can suppress the association and precipitation of the lithium salt and acetonitrile at a low temperature. Further, it is preferable that the content of the lithium-containing imide salt is 0.5 mol or more and 3 mol or less with respect to 1 L of the non-aqueous solvent from the viewpoint of the amount of ion supply. According to the acetonitrile-containing non-aqueous electrolyte solution containing at least one of LiN (SO ₂ F) ₂ and LiN (SO ₂ CF ₃ ) ₂ , ion conduction in a low temperature range such as -10 ° C or -30 ° C. The reduction of the rate can be effectively suppressed, and excellent low temperature characteristics can be obtained. By limiting the content in this way, it is possible to more effectively suppress the increase in resistance during high-temperature heating.

Further, as the lithium salt, a fluorine-containing inorganic lithium salt other than LiPF ₆ may be further contained, for example, LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , Li ₂ B ₁₂ F _b H _12-b [in the formula]. , B is an integer of 0 to 3], etc. may contain a fluorine-containing inorganic lithium salt. The "inorganic lithium salt" refers to a lithium salt that does not contain a carbon atom in an anion and is soluble in acetonitrile. Further, 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 acetonitrile. The fluorine-containing inorganic lithium salt is excellent in that it forms a passivation film on the surface of the metal foil which is a positive electrode current collector and suppresses corrosion of the positive electrode current collector. These fluorine-containing inorganic lithium salts may be used alone or in combination of two or more. As the fluorine-containing inorganic lithium salt, a compound which is a compound salt of LiF and Lewis acid is desirable, and among them, a fluorine-containing inorganic lithium salt having a phosphorus atom is more preferable because it facilitates the release of free fluorine atoms. A typical fluorine-containing inorganic lithium salt is LiPF ₆ which dissolves and releases a PF ₆ anion. When a fluorine-containing inorganic lithium salt having a boron atom is used as the fluorine-containing inorganic lithium salt, it is preferable because it is easy to capture an excess free acid component that may cause deterioration of the battery, and from such a viewpoint. LiBF ₄ is particularly preferred.

The content of the fluorine-containing inorganic lithium salt in the non-aqueous electrolyte solution of the present embodiment is not particularly limited, but is preferably 0.01 mol or more, preferably 0.02 mol or more with respect to 1 L of the non-aqueous solvent. Is more preferable, and 0.03 mol or more is further preferable. When the content of the fluorine-containing inorganic lithium salt is within the above-mentioned range of 0.01 mol or more, the ionic conductivity tends to increase and high output characteristics tend to be exhibited. The content of the fluorine-containing inorganic lithium salt is preferably less than 1.5 mol, more preferably less than 0.5 mol, and even more preferably less than 0.1 mol with respect to 1 L of the non-aqueous solvent. .. When the content of the fluorine-containing inorganic lithium salt is within the above-mentioned range of less than 1.5 mol, the ionic conductivity is increased, high output characteristics can be exhibited, and the ionic conductivity is decreased due to the increase in viscosity at low temperature. It tends to be suppressed, and the high temperature cycle characteristics and other battery characteristics of the non-aqueous secondary battery tend to be further improved while maintaining the excellent performance of the non-aqueous electrolyte solution.

The non-aqueous electrolyte solution of the present embodiment may further contain an organolithium salt. The "organolithium salt" is a lithium salt containing a carbon atom in an anion and soluble in acetonitrile.

Examples of the organolithium salt include an organolithium salt having an oxalic acid group. Specific examples of the organic lithium salt having an oxalate group include, for example, LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O). ₄ ) Organic lithium salts represented by each of ₂ can be mentioned, and at least one lithium salt selected from lithium salts represented by LiB (C ₂ O ₄ ) ₂ and LiBF ₂ (C ₂ O ₄ ). Is preferable. Further, it is more preferable to use one or more of these with a fluorine-containing inorganic lithium salt. This organic lithium salt having a oxalic acid group may be added to the non-aqueous electrolyte solution or may be contained in the negative electrode (negative electrode active material layer).

The amount of the organic lithium salt having a oxalic acid group added to the non-aqueous electrolyte solution is 0.005 mol per 1 L of the non-aqueous solvent of the non-aqueous electrolyte solution from the viewpoint of ensuring the better effect of its use. The above is preferable, 0.02 mol or more is more preferable, and 0.05 mol or more is further preferable. 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 a oxalic acid group added to the non-aqueous electrolyte solution is preferably less than 1.0 mol per 1 L of the non-aqueous electrolyte solution, preferably 0.5 mol. It is more preferably less than a mole, and even more preferably less than 0.2 mol.

Organolithium salts having an oxalic acid group are known to be sparingly soluble in less polar organic solvents, especially chain carbonates. The organic lithium salt having an oxalic acid group may contain a trace amount of lithium oxalate, and even when mixed as a non-aqueous electrolyte solution, it reacts with a trace amount of water contained in other raw materials. , A new white precipitate of lithium oxalate may be generated. Therefore, the content of lithium oxalate in the non-aqueous electrolytic solution of the present embodiment is not particularly limited, but is preferably 0 to 500 ppm.

As the lithium salt in the present embodiment, in addition to those listed above, a lithium salt generally used for non-aqueous secondary batteries may be supplementarily added. Specific examples of other lithium salts include, for example, LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiB ₁₀ Cl ₁₀ , and chloroborane Li, which are inorganic lithium salts containing no fluorine atom in an anion; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ . , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{(2n + 1)} SO ₃ {in the formula, n ≧ 2}, lower aliphatic carboxylic acid Li, tetraphenylborate Li , LiB (C ₃ O ₄ H ₂ ) ₂ and other organic lithium salts; LiPF ₅ (CF ₃ ) and other LiPF _n (C _p F _{2p + 1} ) _6-n [In the formula, n is an integer of 1 to 5 and And p is an integer of 1 to 8]; LiBF _q (C _s F _{2s + 1} ) _4-q such as LiBF ₃ (CF ₃ ) [q is an integer of 1 to 3 in the formula. Yes, and s is an integer of 1-8]; an organic lithium salt; a lithium salt bonded to a polyvalent anion;
The following formula (a):
LiC (SO ₂ R ^A ) (SO ₂ R ^B ) (SO ₂ R ^C ) (a)
^{ In the formula, ^RA , RB, and ^RC may be the same or different from each other, and represent a perfluoroalkyl group having 1 to 8 carbon atoms. },
The following formula (b):
LiN (SO ₂ OR ^D ) (SO ₂ OR ^E ) (b)
{In the formula, ^RD and ^RE may be the same or different from each other and represent a perfluoroalkyl group having 1 to 8 carbon atoms. } And the following formula (c)
LiN (SO ₂ ^RF ) (SO ₂ OR ^G ) (c)
{In the formula, ^{RF and RG may} be the same or different from each other and represent a perfluoroalkyl group having 1 to 8 carbon atoms. }
Examples thereof include organic lithium salts represented by each of the above, and one or more of these can be used together with a fluorine-containing inorganic lithium salt.

<1-3. Additives>
The non-aqueous electrolyte solution according to the present embodiment may contain additives in addition to the non-aqueous solvent and the electrolyte salt described above.

<Diphenyldialkoxysilane>
The non-aqueous electrolytic solution in the present embodiment contains diphenyldialkoxysilane. Diphenyldialkoxysilane can act as an electrode protection additive when a non-aqueous electrolyte solution is used in a non-aqueous secondary battery. Specific examples of the diphenyldialkoxysilane-based additive for electrode protection include diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldipropoxysilane, and diphenyldibutoxysilane. These may be used alone or in combination of two or more. Above all, it is more preferable to use diphenyldimethoxysilane having the smallest molecular weight because the number of moles per unit weight increases.

The content of diphenyldialkoxysilane in the present embodiment is not particularly limited, but is preferably in the range of 0.01% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous solvent. The lower limit of the diphenyldialkoxysilane content is more preferably 0.02% by mass or more, still more preferably 0.05% by mass or more, based on the total amount of the non-aqueous solvent. Further, the upper limit of the diphenyldialkoxysilane content is more preferably 5% by mass or less and further preferably 3% by mass or less with respect to the total amount of the non-aqueous solvent. By adjusting the content of diphenyldialkoxysilane within the above range, it tends to be possible to add even better battery characteristics without impairing the basic function as a non-aqueous secondary battery.

<Other electrode protection additives>
The other electrode protection additives are not particularly limited as long as they do not hinder the solution of the problem according to the present invention, and are substantially the same as the substance (that is, the above-mentioned non-aqueous solvent) which plays a role as a solvent for dissolving the lithium salt. (Excluding acetonitrile, vinylene carbonate, ethylene sulfide, and diphenyldialkoxysilane). The electrode protection additive is preferably a substance that contributes to improving the performance of the non-aqueous electrolyte solution and the non-aqueous secondary battery in the present embodiment, but also includes substances that are not directly involved in the electrochemical reaction. ..

Specific examples of other electrode protection additives 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, Fluoroethylene typified by 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one and 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one Anhydrous bond-containing cyclic carbonate typified by 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; propylene sulphite, butylene sulphite, pentensulfite, sulforane, 3-sulfolene, 3-methylsulfonate, 1,3-propanesulton, 1 , 4-Butan sulton, 1-propen 1,3-sulton, and cyclic sulfur compounds typified by tetramethylene sulfoxide; chain acid anhydride typified by acetic anhydride, propionic anhydride, benzoic anhydride; malonic acid anhydride , Anhydrous succinic acid, glutaric acid anhydride, maleic anhydride, phthalic anhydride, 1,2-cyclohexanedicarboxylic acid anhydride, 2,3-naphthalenedicarboxylic acid anhydride, or naphthalene-1,4,5,8- Cyclic acid anhydrides typified by tetracarboxylic acid dianhydride; examples thereof include two different types of carboxylic acids, or mixed acid anhydrides having a structure in which different types of acids are dehydrated and condensed, such as carboxylic acids and sulfonic acids. These may be used alone or in combination of two or more.

The content of the electrode protection additive in the non-aqueous electrolyte solution in the present embodiment is not particularly limited, but the content of the electrode protection additive with respect to the total amount of the non-aqueous solvent is 0.1 to 30% by volume. It is preferably 0.3 to 15% by volume, more preferably 0.5 to 4% by volume.

In the present embodiment, the larger the content of the electrode protection additive, the more the deterioration of the non-aqueous electrolyte 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, the non-aqueous electrolyte solution is excellent based on the high ionic conductivity without impairing the basic function as a non-aqueous secondary battery. There is a tendency to maximize the performance. By preparing a non-aqueous electrolyte solution with such a composition, the cycle performance of the non-aqueous secondary battery, the high output performance in a low temperature environment, and all other battery characteristics tend to be further improved. be.

<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 electrolytic solution is used, for example, a sulfonic acid ester. , Diphenyl disulfide, 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 , Tris (Trifluoroethyl) Phosphate (TFEP) :( CF ₃ CH ₂ O) ₃ P = O, Triphenyl Phosphate (TPP) :( C ₆ H ₅ O) ₃ P = O: (CH ₂ = CHCH ₂ O) ₃ P = O, triallyl phosphate, etc.], nitrogen-containing cyclic compounds with no steric damage around unshared electron pairs [pyridine, 1-methyl-1H-benzotriazole, 1-methylpyrazole, etc.] ] Etc., and an optional additive selected from derivatives of these compounds and the like can be appropriately contained. Phosphoric acid esters are particularly effective because they have the effect of suppressing side reactions during storage.

The content of the other optional additives in the present embodiment is calculated as a mass percentage with respect to the total mass of all the components constituting the non-aqueous electrolyte solution. The content of other optional additives is not particularly limited, but is preferably in the range of 0.01% by mass or more and 10% by mass or less, and 0.02% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is more preferably 5% by mass or less, and further preferably 0.05% by mass or more and 3% by mass or less. By adjusting the content of other optional additives within the above range, it tends to be possible to add even better battery characteristics without impairing the basic functions of a non-aqueous secondary battery. be.

<2. Positive electrode and positive electrode current collector>
The positive electrode 150 shown in FIGS. 1 and 2 is composed of 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 in the present invention contains a lithium-containing compound containing Fe, preferably nickel (Ni) in a relatively high ratio.

The positive electrode active material layer preferably contains a positive electrode active material, and if necessary, further contains a conductive auxiliary agent and a binder.

The positive electrode active material layer preferably contains, as the positive electrode active material, a material capable of occluding and releasing lithium ions. When such a material is used, it is preferable because a high voltage and a high energy density tend to be obtained.

Examples of the positive electrode active material include a positive electrode active material containing at least one transition metal element selected from the group consisting of Ni, Mn, and Co, and the following general formula (a):
Li _p Ni _q Co _r Mn _s M _t O _u ... (1)
{In the formula, M is aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn). , Molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and is at least one metal selected from the group, and 0 <p <1.3, 0 <q <1. .2, 0 <r <1.2, 0 ≦ s <0.5, 0 ≦ t <0.3, 0.7 ≦ q + r + s + t ≦ 1.2, 1.8 <u <2.2 , And p are values determined by the charge / discharge state of the battery. }
At least one Li-containing metal oxide selected from the lithium (Li) -containing metal oxide represented by is preferable.

Specific examples of the positive electrode active material include, for example, lithium cobalt oxide represented by LiCoO ₂ ; lithium manganese oxide represented by LiMnO ₂ , LiMn ₂ O ₄ and Li ₂ Mn ₂ O ₄ ; represented by LiNiO ₂ . Lithium nickel oxide; LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Co _0.2 O ₂ Li _z MO ₂ (in the formula, M contains at least one transition metal element selected from the group consisting of Ni, Mn, and Co, and from the group consisting of Ni, Mn, Co, Al, and Mg. It indicates two or more kinds of selected metal elements, and z indicates a number of more than 0.9 and less than 1.2), and examples thereof include lithium-containing composite metal oxides.

In particular, when the Ni content ratio q of the Li-containing metal oxide represented by the general formula (1) is 0.5 <q <1.2, the amount of Co, which is a rare metal, can be reduced and high energy can be obtained. It is preferable because both densification is achieved. Examples of such positive electrode active materials include LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.75 Co _0.15 Mn _0.15 O ₂ , and LiNi _0.8 Co _0.1 Mn. _0.1 O ₂ , LiNi _0.85 Co _0.075 Mn _0.075 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _0.81 Co _0.1 Al _0.09 O ₂ , LiNi _0.85 Co _0.1 Al _0.05 O ₂ , etc., and examples thereof include lithium-containing composite metal oxides.

On the other hand, as the Ni content ratio in the positive electrode active material layer increases, deterioration tends to proceed at a lower voltage. The positive electrode active material of the Li-containing metal oxide represented by the general formula (1) essentially has an active point that oxidatively deteriorates the non-aqueous electrolyte solution, and this active point is added to protect the negative electrode. The compound may be unintentionally consumed on the positive electrode side. Above all, acid anhydride tends to be easily affected by it. In particular, when acetonitrile is contained as a non-aqueous solvent, the effect of adding the acid anhydride is enormous, and therefore it is a fatal problem that the acid anhydride is consumed on the positive electrode side.

In addition, these additive decomposition products taken in and deposited on the positive electrode side not only cause an increase in the internal resistance of the non-aqueous secondary battery, but also accelerate the deterioration of the lithium salt. Furthermore, the protection of the negative electrode surface, which was the original purpose, is insufficient. In order to deactivate the active site that essentially oxidatively deteriorates the non-aqueous electrolyte solution, it is important to control the Jahn-Teller strain or to coexist with a component that plays a role as a neutralizing agent. Therefore, it is preferable that the positive electrode active material contains at least one metal selected from the group consisting of Al, Sn, In, Fe, V, Cu, Mg, Ti, Zn, Mo, Zr, Sr, and Ba.

For the same reason, it is preferable that the surface of the positive electrode active material is coated with a compound containing at least one metal element selected from the group consisting of Zr, Ti, Al, and Nb. Further, it is more preferable that the surface of the positive electrode active material is coated with an oxide containing at least one metal element selected from the group consisting of Zr, Ti, Al, and Nb. Further, that the surface of the positive electrode active material is coated with at least one oxide selected from the group consisting of ZrO ₂ , TiO ₂ , Al ₂ O ₃ , NbO ₃ , and LiNbO ₂ to allow lithium ions to permeate. It is particularly preferable because it does not inhibit the above.

The positive electrode active material may be a lithium-containing compound other than the Li-containing metal oxide represented by the formula (1), and 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 chalcogen product having lithium, a phosphate metal compound containing lithium and a transition metal element, and lithium and a transition metal element. Examples include metal silicate compounds containing. From the viewpoint of obtaining a higher voltage, the lithium-containing compound is at least one transition metal element selected from the group consisting of lithium, Co, Ni, Mn, Fe, Cu, Zn, Cr, V, and Ti. And, a metal phosphate compound containing is preferable.
More specifically, as the lithium-containing compound, the following formula (Xa):
Li _v M ID ₂ ( ^Xa )
{In the formula, D indicates a ^chalcogen element, MI indicates one or more transition metal elements including at least one transition metal element, and the value of v is determined by the charge / discharge state of the battery and is 0.05 to 0.05. The number of 1.10 is shown. },
The following formula (Xb):
Li _w M ^II PO ₄ (Xb)
{In the formula, M ^II indicates one or more transition metal elements including at least one transition metal element, and the value of w is determined by the charge / discharge state of the battery and is a number of 0.05 to 1.10. show. } And the following formula (Xc):
_Lit M ^III _u SiO ₄ (Xc)
{In the formula, M ^III represents one or more transition metal elements including at least one transition metal element, and the value of t is determined by the charge / discharge state of the battery and is a number of 0.05 to 1.10. Indicated, and u indicates a number from 0 to 2. }
Examples thereof include compounds represented by each of the above.

The lithium-containing compound represented by the above formula (Xa) has a layered structure, and the compounds represented by the above formulas (Xb) and (Xc) have 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 contained in the crystal grain boundary. It may be a substance in which a part of an oxygen atom is replaced with a fluorine atom or the like, a substance in which at least a part of the surface of the positive electrode active material is coated with another positive electrode active material, or the like.

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 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. Metal oxides or metal chalcogenides having a tunnel structure and a layered structure include, for example, 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, selenium compounds and the like 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 high energy density can be achieved, the positive electrode active material layer is at least one transition metal element selected from Ni, Mn, and Co. Is preferably contained.

When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the usage ratio of both is preferably 80% by mass or more, preferably 85% by mass, as the usage ratio of the lithium-containing compound to the total 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 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 positive electrode current collector is composed of, for example, a metal foil such as an aluminum foil, a nickel foil, and a stainless steel foil. The surface of the positive electrode 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.

<3. Negative electrode and negative electrode current collector>
The negative electrode 160 shown in FIGS. 1 and 2 is composed of a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The negative electrode 160 can act as a negative electrode of a non-aqueous secondary battery.

The negative electrode active material layer preferably contains a negative electrode active material and, if necessary, a conductive auxiliary agent and a binder.

Examples of the negative electrode active material include amorphous carbon (hard carbon), graphite (for example, artificial graphite, natural graphite, etc.), thermally decomposed carbon, coke, glassy carbon, calcined organic polymer compounds, mesocarbon microbeads, and the like. In addition to carbon materials such as carbon fibers, activated carbon, carbon colloids, and carbon black, metallic lithium, metal oxides, metal nitrides, lithium alloys, tin alloys, silicon alloys, intermetallic compounds, organic compounds, and inorganic compounds, Examples thereof include metal complexes and organic polymer compounds. The negative electrode active material may be used alone or in combination of two or more.

The negative electrode active material layer contains lithium ions of 0.4 V vs. as the negative electrode active material from the viewpoint of increasing the battery voltage. It is preferable to contain a material that can be occluded at a lower potential than Li / Li ⁺ .

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 carboxymethyl cellulose, PVDF, PTFE, polyacrylic acid, and fluororubber. Further, a diene-based rubber, for example, styrene-butadiene rubber and the like can also be mentioned. 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 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 be coated with carbon 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 even more preferably 7 to 30 μm.

<4. Separator>
As shown in FIG. 2, in the non-aqueous secondary battery 100 of the present embodiment, a separator 170 is provided 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. It is preferable to prepare. The separator 170 is not limited, but may be the same as that provided in a known non-aqueous secondary battery, and an insulating thin film having high ion permeability and excellent mechanical strength can be used. preferable. Examples of the separator 170 include woven fabrics, non-woven fabrics, and microporous membranes made of synthetic resin. Among these, microporous synthetic resin membranes 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 structure 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.

Inorganic particles may be present on the surface layer or inside of the separator for the purpose of imparting a function, and other organic layers may be further coated or laminated. Further, it may include a crosslinked structure. In order to improve the safety performance of the non-aqueous secondary battery, these methods may be combined as necessary.

By using such a separator 170, it is possible to realize good input / output characteristics and low self-discharge characteristics particularly required for the above-mentioned lithium ion battery for high output applications.

The film thickness of the microporous membrane that can be used as a separator is not particularly limited, but is preferably 1 μm or more from the viewpoint of membrane strength, and preferably 500 μm or less from the viewpoint of permeability. The film thickness of the microporous membrane has a relatively high calorific value, such as safety tests, and is used for high-output applications that require higher self-discharge characteristics than before, and is wound by a large battery winding machine. From the viewpoint of properties, it is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 25 μm or less. The film thickness of the microporous membrane is more preferably 15 μm or more and 25 μm or less when it is important to achieve both short-circuit resistance and output performance, but when it is important to achieve both high energy density and output performance. More preferably, it is 10 μm or more and less than 15 μm.

The porosity of the microporous membrane that can be used as a separator is preferably 30% or more and 90% or less, more preferably 35% or more and 80% or less, and more preferably 40%, from the viewpoint of following the rapid movement of lithium ions at high output. More than 70% is more preferable. When giving priority to improving output performance while ensuring safety, the porosity of the microporous membrane is particularly preferably 50% or more and 70% or less, and emphasis is placed on achieving both short-circuit resistance and output performance. In this case, 40% or more and less than 50% is particularly preferable.

From the viewpoint of the balance between the film thickness and the porosity, the air permeability of the microporous membrane that can be used as a separator is preferably 1 second / 100 cm ³ or more and 400 seconds / 100 cm ³ or less, and 100 seconds / 100 cm ³ or more 350 /. More preferably 100 cm ³ or less. When it is important to achieve both short-circuit resistance and output performance, the air permeability of the microporous membrane is particularly preferably 150 seconds / 100 cm ³ or more and 350 seconds / 100 cm ³ or less, and the output is performed while ensuring safety. When the improvement of performance is prioritized, 100/100 cm ³ seconds or more and less than 150 seconds / 100 cm ³ is particularly preferable. On the other hand, when a non-aqueous electrolyte solution having low ionic conductivity and a separator within the above range are combined, the high ionic conductivity of the non-aqueous electrolyte solution determines the moving speed of lithium ions, not the structure of the separator. Therefore, there is a tendency that the expected input / output characteristics cannot be obtained. Therefore, the ionic conductivity of the non-aqueous electrolyte solution is preferably 10 mS / cm or more, more preferably 15 mS / cm, and even more preferably 20 mS / cm. However, the film thickness, air permeability and porosity of the separator, and the ionic conductivity of the non-aqueous electrolyte solution are not limited to the above examples.

<5. Battery exterior ＞
The configuration of the battery exterior 110 of the non-aqueous secondary battery 100 shown in FIGS. 1 and 2 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 such as a square type, a square cylinder type, a cylindrical type, an elliptical type, a flat type, a coin type, or a button type made of steel, stainless steel, aluminum, clad material, or the like can be used. .. As the laminating film exterior body, for example, a laminating film having a three-layer structure of a heat-melted resin / metal film / resin can be used.

The laminated film exterior is in a state where two sheets are stacked with the heat-melted resin side facing inward, or bent so that the heat-melted resin side faces inward, and the end is sealed by a heat seal. 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 exterior 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 respectively) pulled out to the outside of the exterior body. May be good.

<6. 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 a current collector, and a negative electrode active material layer on one side or both sides of a 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 negative electrode 160, and, if necessary, a separator 170 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;
An embodiment of forming a laminated body having a laminated structure in which a positive electrode sheet and a negative electrode sheet obtained by cutting a positive electrode 150 and a negative electrode 160 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet. ;
An embodiment in which a long separator is folded in a zigzag manner, and a positive electrode body sheet and a negative electrode body sheet are alternately inserted between the zigzagly folded separators to form a laminated body having a laminated structure;
Etc. are possible.

Next, the above-mentioned laminate is housed in the battery exterior 110 (battery case), the non-aqueous electrolyte solution according to the present embodiment is injected into the battery case, and the laminate is immersed in the non-aqueous electrolyte solution for sealing. By doing so, 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 a non-aqueous electrolyte solution, and a sheet-shaped positive electrode 150, a negative electrode 160, and an electrolyte membrane, and necessary. A non-aqueous secondary battery 100 can also be manufactured by forming a laminated body having a laminated structure using the separator 170 and then accommodating the laminated body in the battery exterior 110.

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 it 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 polyimide tape, a polyphenylene sulfide tape, a tape such as a polypropylene (PP) tape, an adhesive or the like.

In the present embodiment, when a non-aqueous electrolyte solution using acetonitrile is used, the lithium ions released from the positive electrode during the initial charge of the non-aqueous secondary battery diffuse to the entire negative electrode due to its high ionic conductivity. There is a possibility that it will be done. In a non-aqueous secondary battery, the area of the negative electrode active material layer is generally larger than that of the positive electrode active material layer. However, if lithium ions are diffused and stored in a portion of the negative electrode active material layer that does not face the positive electrode active material layer, the lithium ions are not released at the time of initial discharge and remain in the negative electrode. Therefore, the contribution of the unreleased lithium ion becomes an irreversible capacity. For this reason, a non-aqueous secondary battery using a non-aqueous electrolytic solution containing acetonitrile may have a low initial charge / discharge efficiency.

On the other hand, when the area of the positive electrode active material layer is larger than that of the negative electrode active material layer, or when both are the same, current is likely to be concentrated at the edge portion of the negative electrode active material layer during charging, and lithium dendrite is generated. It will be easier.

For the above reasons, the ratio of the area of the entire negative electrode active material layer to the area of the portion where the positive electrode active material layer and the negative electrode active material layer face each other is not particularly limited, but is larger than 1.0 and less than 1.1. It is preferably greater than 1.002 and less than 1.09, more preferably greater than 1.005 and less than 1.08, and greater than 1.01 and less than 1.08. Especially preferable. In a non-aqueous secondary battery using a non-aqueous electrolyte solution containing acetonitrile, the ratio of the area of the entire negative electrode active material layer to the area of the portion where the positive electrode active material layer and the negative electrode active material layer face each other is reduced. The initial charge / discharge efficiency can be improved.

Reducing the ratio of the area of the entire negative electrode active material layer to the area of the portion where the positive electrode active material layer and the negative electrode active material layer face each other means that the negative electrode active material layer does not face the positive electrode active material layer. It means limiting the proportion of the area of the part. As a result, of the lithium ions released from the positive electrode during the initial charge, the amount of lithium ions stored in the portion of the negative electrode active material layer that does not face the positive electrode active material layer (that is, the amount of lithium ions released from the negative electrode during the initial discharge). It is possible to reduce the amount of lithium ions, which becomes an irreversible capacity) as much as possible. Therefore, by designing the ratio of the area of the entire negative electrode active material layer to the area of the portion where the positive electrode active material layer and the negative electrode active material layer face each other within the above range, the load characteristics of the battery due to the use of acetonitrile While improving the battery, the initial charge / discharge efficiency of the battery can be improved, and the generation of lithium dendrite can be suppressed.

The non-aqueous secondary battery 100 in the present embodiment can function as a battery by the initial charge, but is stabilized by decomposing a part of the non-aqueous electrolytic solution at the initial charge. 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 design capacity in 1 hour is 1C. By setting a long voltage range in which the lithium salt is involved in the electrochemical reaction, a stable and strong SEI is formed on the surface of the electrode (negative electrode 160), which has the effect of suppressing an increase in internal resistance and also reacts. The product is not firmly immobilized only on the negative electrode 160, and 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 charge 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 managing 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 more 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 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. The present invention is not limited to these examples.

(1) Preparation of non-aqueous electrolyte solution Under an inert atmosphere, various non-aqueous solvents and various additives are mixed so as to have a predetermined concentration, and further, various lithium salts are added so as to have a predetermined concentration. By doing so, the non-aqueous electrolyte solutions (S01) to (S04) were prepared. The abbreviations for non-aqueous solvents, lithium salts, and additives in Table 1 have the following meanings. Further, the mass% of the additive in Table 1 indicates the ratio of the mass part to 100 parts by mass of the non-aqueous electrolyte solution excluding the additive.
(Lithium salt)
LiPF ₆ : Lithium hexafluorophosphate LiFSI: Lithium bis (fluorosulfonyl) imide (non-aqueous solvent)
AcN: Acetonitrile EMC: Ethylmethyl carbonate EC: Ethylene carbonate VC: Vinylene carbonate (Additives: Others)
DPDMS: Diphenyldimethoxysilane

(2) Preparation of non-aqueous secondary battery (2-1) Preparation of positive electrode (A) Composite oxide of lithium, nickel, manganese, and cobalt as positive electrode active material (LiNi _0.8 Mn _0.1 Co _0.1 ) O ₂ ), (B) acetylene black powder as a conductive auxiliary agent, and (C) polyvinylidene fluoride (PVDF) as a binder are mixed at a mass ratio of 95: 3: 2 to obtain a positive electrode mixture. rice field.

N-Methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture so as to have a solid content of 68% by mass and further mixed to prepare a slurry containing a positive electrode mixture. A coating width of 240 to 250 mm, a coating length of 125 mm, and a non-coating length of 20 mm are adjusted on one side of an aluminum foil having a thickness of 15 μm and a width of 280 mm, which serves as a positive electrode current collector, while adjusting the basis weight of the slurry containing the positive electrode mixture. The coating was applied using a 3-roll transfer coater so as to have the coating pattern of, and the solvent was dried and removed in a hot air drying oven. Both sides of the obtained electrode roll were trimmed and cut, and dried under reduced pressure at 130 ° C. for 8 hours. Then, by rolling with a roll press so that the density of the positive electrode active material layer was 3.3 g / cm ³ , a positive electrode composed of the positive electrode active material layer and the positive electrode current collector was obtained. The basis weight excluding the positive electrode current collector was 15.5 mg / cm ² .

(2-2) Preparation of negative electrode (a) Artificial graphite powder (density 2.23 g / cm ³ ) with a number average particle diameter of 12.7 μm as a negative electrode active material, and (b) Number average particle diameter as a conductive auxiliary agent. 48 nm acetylene black powder (density 1.95 g / cm ³ ), (c) carboxymethyl cellulose (density 1.60 g / cm ³ ) solution (solid content concentration 1.83% by mass) and diene rubber (glass) as a binder. Transition temperature: -5 ° C, number average particle size when dried: 120 nm, density 1.00 g / cm ³ , dispersion medium: water, solid content concentration 40% by mass), (a) 95.7: (b) 0.5: (c) The mixture was mixed at a solid content mass ratio of 3.8 to obtain a negative electrode mixture.

Water was added to the obtained negative electrode mixture as a solvent so as to have a solid content of 45% by mass, and the mixture was further mixed to prepare a slurry containing the negative electrode mixture. While adjusting the basis weight of this negative electrode mixture-containing slurry on one side of a copper foil with a thickness of 8 μm and a width of 280 mm, which is a negative electrode current collector, the coating width is 240 to 250 mm, the coating length is 125 mm, and the coating length is 20 mm. The coating was applied using a 3-roll transfer coater so as to have the coating pattern of, and the solvent was dried and removed in a hot air drying furnace. Both sides of the obtained electrode roll were trimmed and cut, and dried under reduced pressure at 80 ° C. for 12 hours. Then, it was rolled by a roll press so that the density of the negative electrode active material layer was 1.5 g / cm ³ , and a negative electrode (N1) composed of the negative electrode active material layer and the negative electrode current collector was obtained. The basis weight of the negative electrode active material layer was 11.9 mg / cm ² .

(2-3) Assembly of non-aqueous secondary battery As the non-aqueous secondary battery, a test cell "PAT-cell" manufactured by EL-Cell was used. The positive electrode obtained in (2-1) above was punched into a disk shape having a diameter of 18 mm, and a separator (“FS-5P” manufactured by EL-Cell: two layers of polypropylene (PP) / polyethylene (PE), thickness 220 μm) was used. A laminate was obtained by superimposing on one side. The laminate was inserted into a cell case, and 120 μl of the electrolytic solution was uniformly dropped onto the separator using a pipette. Next, the negative electrode obtained in (2-2) above is punched into a disk shape having a diameter of 18 mm, overlapped with the separator side of the laminate, the upper plunger is attached, the screw cap is attached to the cell base, and the wing nut is attached. Tightened to seal the cell.

(3) Evaluation of non-aqueous secondary battery With respect to the non-aqueous secondary battery obtained as described above, first, the initial charging process and the initial charge / discharge capacity measurement were performed according to the procedure of (3-1) below. Next, each coin-type non-aqueous secondary battery was evaluated according to the procedure of (3-2) below. The charging / discharging was performed using a charging / discharging device BCS-805 (trade name) manufactured by BioLogic and a program constant temperature bath MK115 (trade name) manufactured by Binder. An EL-Cell test cell stand "PAT-Stand" was used for the connection between the charging / discharging device and the PAT-Cell.

Here, 1C means a current value that is expected to end the discharge in 1 hour by discharging the fully charged battery with a constant current.

(3-1) Initial charge / discharge treatment of non-aqueous secondary battery Set the ambient temperature of the non-aqueous secondary battery to 25 ° C, and charge it with a constant current of 0.185mA, which corresponds to 0.025C, to 3.1V. After reaching it, it was charged with a constant current of 0.37 mA corresponding to 0.05 C, reached 4.2 V, and then charged with a constant current of 4.2 V until the current decreased to 0.025 C. Then, the battery was discharged to 3.0 V with a constant current of 1.11 mA corresponding to 0.15 C.

Next, after reaching 4.2 V with a constant current of 1.48 mA corresponding to 0.2 C, charging was performed with a constant voltage of 4.2 V until the current attenuated to 0.025 C. Then, the battery was discharged to 3 V with a current value of 1.48 mA corresponding to 0.2 C. Then, the same charge / discharge as above was performed for one cycle.

(3-2) Cycle test For the non-aqueous secondary battery that was initially charged and discharged by the method described in (3-1) above, the ambient temperature was set to 55 ° C and 11.1 mA corresponding to 1.5 C. After reaching 4.2V with a constant current of 4.2V, charging was performed with a constant voltage of 4.2V until the current attenuated to 0.025C. Then, the battery was discharged to 3 V with a current value of 11.1 mA corresponding to 1.5 C. After that, the same charge / discharge as above was performed for 100 cycles.

When the discharge capacity of the first cycle in the cycle test was set to 100%, the discharge capacity of the 100th cycle in the cycle test was calculated as the capacity retention rate.

(3-3) Non-aqueous secondary battery [Example 1 and Comparative Examples 1 to 3]
Using each of the electrolytic solutions shown in Table 2, a non-aqueous secondary battery was assembled as described above, and the initial charge / discharge treatment and the cycle test were performed. Here, the interpretation of each test result will be described.

The capacity retention rate is an index showing the ratio of the discharge capacity in the 100th cycle to the discharge capacity in the first cycle. In the above cycle test, charging / discharging is repeated at a higher current density than in a general cycle test, and the larger the value, the smaller the capacity deterioration when the charging / discharging is repeatedly used. The capacity retention rate is preferably 85% or more, more preferably 86% or more, and further preferably 88% or more.

In Example 1, it was confirmed that the capacity retention rate did not decrease much when 1.5C charging / discharging was repeated, and the cycle performance was improved. That is, it was confirmed that stable operation was performed at a high current density. On the other hand, in Comparative Example 1 using an electrolytic solution containing ethylene sulfide and DPDMS, and Comparative Examples 2 to 3 using an electrolytic solution containing DPDMS but not containing ethylene sulfide, compared with Example 1. , The capacity retention rate of the cycle test was greatly reduced.

From the above results, in the present embodiment, a non-aqueous electrolyte solution is prepared by containing vinylene carbonate and ethylene sulfide in a non-aqueous solvent and adding DPDMS as diphenyldialkoxysilane in an appropriate ratio to prepare a non-aqueous electrolyte solution. It was confirmed that even when the non-aqueous secondary battery was repeatedly charged and discharged at a density, there was little capacity deterioration and stable operation was exhibited.

The non-aqueous secondary battery of the present invention is, for example, a storage battery for automobiles such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle, an industrial storage battery such as an electric tool, a drone, and an electric motorcycle, and a storage system for a house. Is also expected to be used.

100 Non-aqueous secondary battery 110 Battery exterior 120 Battery exterior space 130 Positive electrode lead body 140 Negative electrode lead body 150 Positive electrode 160 Negative electrode 170 Separator

Claims (6)

A non-aqueous electrolyte solution containing a non-aqueous solvent and LiPF ₆ .
The non-aqueous solvent contains acetonitrile, vinylene carbonate, and ethylene sulphite, and the volume ratio of vinylene carbonate is smaller than the volume ratio of ethylene sulphite.
Further, a non-aqueous electrolytic solution containing diphenyldialkoxysilane. The non-aqueous electrolyte solution according to claim 1, wherein the content of acetonitrile in the non-aqueous solvent is 5 to 97% by volume based on the total amount of the non-aqueous solvent. The non-aqueous electrolyte solution according to claim 1 or 2, wherein the content of the diphenyldialkoxysilane is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous solvent. The non-aqueous electrolytic solution according to any one of claims 1 to 3, wherein the diphenyldialkoxysilane is diphenyldimethoxysilane. The one according to any one of claims 1 to 4, wherein a positive electrode having a positive electrode active material layer on one side or both sides of a current collector, a negative electrode having a negative electrode active material layer on one side or both sides of a current collector, and a separator. In a non-aqueous secondary battery provided with a non-aqueous electrolyte solution,
The positive electrode active material layer has the following general formula (1):
Li _p Ni _q Co _r Mn _s M _t O _u ... (1)
{In the formula, M is aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn). ), Molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and is at least one metal selected from the group consisting of 0 <p <1.3, 0 <q <. In the range of 1.2, 0 <r <1.2, 0 ≦ s <0.5, 0 ≦ t <0.3, 0.7 ≦ q + r + s + t ≦ 1.2, 1.8 <u <2.2 Yes, and p is a value determined by the charge / discharge state of the battery. }
A non-aqueous secondary battery containing at least one selected from the group consisting of lithium-containing metal oxides represented by. The non-aqueous secondary battery according to claim 5, wherein the lithium (Ni) content ratio q of the lithium-containing metal oxide represented by the general formula (1) is 0.5 <q <1.2.

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