Non-aqueous electrolyte, non-aqueous electrolyte secondary battery comprising that non-aqueous electrolyte, and compound

Abstract

To provide a non-aqueous electrolyte that reduces the initial input resistance of a non-aqueous electrolyte secondary battery and inhibits gas generation in the battery.SOLUTION: A non-aqueous electrolyte contains an electrolyte, a non-aqueous solvent, and a compound represented by the formula (I) in the figure. (In the formula (I), X and Y are sulfur-containing ester structures; R1 and R2 are each independently a halogen atom or a C1-10 organic group; and R3 is a C3-20 alkylene group with a substituent comprising at least one carbon-carbon unsaturated bond.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte, a non-aqueous electrolyte secondary battery containing the non-aqueous electrolyte, and a compound.

Background Art

[0002] Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are being put into practical use in a wide range of applications, from so-called consumer power sources such as mobile phones and notebook computers to in-vehicle power sources for driving such as automotive use. However, in recent years, the demand for higher performance of non-aqueous electrolyte secondary batteries has been increasing more and more. In particular, improvements in various battery characteristics such as high capacity, low-temperature use characteristics, high-temperature storage characteristics, cycle characteristics, and safety during overcharging are desired. So far, as means for improving the high-temperature storage test and cycle test of non-aqueous electrolyte secondary batteries, numerous technologies have been studied for various battery components such as the active materials of the positive and negative electrodes and the non-aqueous electrolyte.

[0003] Patent Document 1 describes a lithium secondary battery composed of a non-aqueous electrolyte containing a specific disulfonic acid ester derivative in order to have excellent cycle characteristics and further improve battery characteristics such as electric capacity and storage characteristics in a charged state. Patent Document 2 describes a lithium secondary battery composed of a non-aqueous electrolyte containing a specific disulfonic acid ester derivative containing a double bond in the main chain in order to have excellent cycle characteristics and further improve battery characteristics such as electric capacity and storage characteristics in a charged state. Patent Document 3 describes a lithium secondary battery composed of a non-aqueous electrolyte containing a chain compound having one or more sulfur-containing functional groups in order to improve the cycle capacity retention rate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] However, when the present inventors examined the methods described in Patent Documents 1 to 3, they found that the film formation reaction on the electrode does not proceed smoothly, making it difficult to achieve both a reduction in the initial input resistance of a non-aqueous electrolyte secondary battery and suppression of gas generation within the battery. [Means for solving the problem]

[0006] In view of the above circumstances, the inventors of this invention conducted diligent research and found that the above problems can be solved by including a sulfur-containing ester compound having an unsaturated bond in a non-aqueous electrolyte, and thus completed the present invention. In other words, the present invention relates to the following [1] to

[15] . [1] A non-aqueous electrolyte containing an electrolyte, a non-aqueous solvent, and a compound represented by the following formula (I). [ka] (In formula (I), X and Y are sulfur-containing ester structures; R 1 and R 2 Each is independently a halogen atom or an organic group having 1 to 10 carbon atoms; R 3 This is an alkylene group having 3 to 20 carbon atoms and a substituent containing at least one carbon-carbon unsaturated bond. [2] The non-aqueous electrolyte according to [1], wherein the substituent containing a carbon-carbon unsaturated bond is a substituent containing a carbon-carbon unsaturated bond at its terminal end. [3] The compound according to [1] or [2], wherein the substituent containing the carbon-carbon unsaturated bond is an alkenyl group. [4] The aforementioned R 3 The alkylene group represented by has 3 to 10 carbon atoms, and is one of the compounds described in any of [1] to [3]. [5] The above-mentioned R 1 and R 2 are each independently a hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom, and the compound according to any one of [1] to [4]. [6] The content of the compound represented by the formula (I) is 0.001 to 10% by mass based on the total amount of the non-aqueous electrolyte, and the non-aqueous electrolyte according to any one of [1] to [5]. [7] The electrolyte contains LiPF6, and the mass ratio of the content of the compound represented by the formula (I) to the content of PF6 - [the content of the compound represented by the formula (I) / PF6 - content] is 0.00001 to 1, and the non-aqueous electrolyte according to any one of claims [1] to [6]. [8] A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of claims [1] to [7]. [9] The non-aqueous electrolyte secondary battery according to [8], wherein the positive electrode contains a lithium transition metal oxide represented by the following compositional formula (1). Li 1+x MO2(1) (In the compositional formula (1), x is -0.1 or more and 0.5 or less, and M is at least one transition metal element.)

[10] A compound represented by the following formula (I).

Chemical formula

[11] The compound according to

[10] , wherein the substituent containing a carbon-carbon unsaturated bond is a substituent containing a carbon-carbon unsaturated bond at the terminal.

[12] The compound according to

[10] or

[11] , wherein the substituent containing a carbon-carbon unsaturated bond is an alkenyl group.

[13] The aforementioned R 3 The alkylene group represented by has 3 to 10 carbon atoms, and is a compound as described in any of

[10] to

[12] .

[14] The aforementioned R 1 and R 2 The compounds described in any of

[10] to

[13] are each independently a hydrocarbon group having 1 to 10 carbon atoms, which may be substituted with a halogen atom.

[15] A compound according to any of

[10] to

[14] , wherein the compound represented by formula (I) is the compound represented by formula (II) below. [ka] (In formula (II), R 4 and R 5 Each is independently a halogen atom or an organic group having 1 to 10 carbon atoms; R 6 This is an alkylene group having 3 to 20 carbon atoms and a substituent containing at least one carbon-carbon unsaturated bond. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a non-aqueous electrolyte that achieves both a reduction in the initial input resistance of a non-aqueous electrolyte secondary battery and suppression of gas generation within the battery. [Modes for carrying out the invention]

[0008] The reason why the non-aqueous electrolyte of the present invention exhibits such excellent effects is not entirely clear, but it is presumed to be as follows: The disulfonic acid ester compound described in Patent Document 1 reacts with the electrode to form a low-resistance film component, but because it does not contain a structure containing a carbon-carbon unsaturated bond, the reaction with the electrode is slow and film formation is insufficient. Therefore, it is thought that the reduction of the initial input resistance and the suppression of gas generation within the battery are insufficient in non-aqueous electrolyte secondary batteries. The non-aqueous electrolyte of the present invention contains a compound represented by formula (I). The compound represented by formula (I) has substituents containing carbon-carbon unsaturated bonds, and these carbon-carbon unsaturated bonds react sufficiently with the electrodes to form a low-resistance film. Therefore, it is believed that both a reduction in the initial input resistance of a non-aqueous electrolyte secondary battery and a suppression of gas generation within the battery can be achieved.

[0009] In this specification, "α~β" means that the numerical range is greater than or equal to α and less than or equal to β.

[0010] <1.Non-aqueous electrolyte> The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery according to the embodiment of the present invention contains an electrolyte and a non-aqueous solvent for dissolving it, similar to a general non-aqueous electrolyte, and contains a compound represented by formula (I) described below.

[0011] [1-1. Compounds represented by formula (I)] [ka]

[0012] In formula (I), X and Y are sulfur-containing ester structures; R 1 and R 2 Each is independently a halogen atom or an organic group having 1 to 10 carbon atoms; R 3 This is an alkylene group having 3 to 20 carbon atoms and a substituent containing at least one carbon-carbon unsaturated bond.

[0013] R 1 and R 2 In this context, an organic group refers to a functional group composed of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and halogen atoms. Specific examples include hydrocarbon groups such as alkyl groups, alkenyl groups, alkynyl groups, and aryl groups; oxygen and carbon atom-containing functional groups such as alkoxy groups, ether groups, carbonate groups, and carbonyl groups; and nitrogen and carbon atom-containing functional groups such as nitrile groups. Organic groups may have substituents, such as halogen atoms.

[0014] The organic group is preferably a hydrocarbon group having 1 to 10 carbon atoms that may be substituted with a halogen atom, more preferably a hydrocarbon group having 1 to 8 carbon atoms that may be substituted with a halogen atom, even more preferably a hydrocarbon group having 1 to 5 carbon atoms that may be substituted with a halogen atom, and even more preferably a hydrocarbon group having 1 to 3 carbon atoms that may be substituted with a halogen atom. Furthermore, "hydrocarbon groups that may be substituted with halogen atoms" refers to hydrocarbon groups in which at least one hydrogen atom of the hydrocarbon group is substituted with a halogen atom, as well as unsubstituted hydrocarbon groups.

[0015] Furthermore, the organic group is preferably an alkyl group having 1 to 8 carbon atoms that may be substituted with a halogen atom, more preferably an alkyl group having 1 to 5 carbon atoms that may be substituted with a halogen atom, even more preferably an alkyl group having 1 to 3 carbon atoms that may be substituted with a halogen atom, and even more preferably a methyl group.

[0016] R 3 In this context, the number of carbon atoms refers to the number of carbon atoms including substituents. Furthermore, substituents containing a carbon-carbon unsaturated bond refer to groups having an unsaturated aliphatic hydrocarbon group such as an alkenyl group or an alkynyl group, or an aromatic hydrocarbon group such as an aryl group or an aralkyl group. It is preferable that the substituent is an unsaturated aliphatic hydrocarbon group, and more preferably an alkenyl group. In addition, substituents containing at least one carbon-carbon unsaturated bond at their terminus are preferred.

[0017] R 3 The number of carbon atoms in the alkylene group represented is preferably 3 to 10, more preferably 3 to 8, and even more preferably 3 to 6.

[0018] In formula (I), X and Y are preferably each independently a sulfur-containing ester structure selected from a sulfonic acid ester structure, a sulfuric acid ester structure, and a sulfite ester structure, and it is more preferable that the compound represented by formula (I) is the compound represented by formula (II).

[0019] [ka]

[0020] In the above equation (II), R 4 , R 5 , and R 6 These are, respectively, R in formula (I) above. 1 , R 2 , and R 3 It is synonymous with [the above].

[0021] The molecular weight of the compound represented by formula (I) is not particularly limited, but is usually 200 or more, and usually 2000 or less, preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less. The molecular weight of the compound represented by formula (I) is preferably 200 to 1000, more preferably 200 to 500, and even more preferably 200 to 300. This range makes the compound easy to handle and allows for an appropriate viscosity of the non-aqueous electrolyte when added.

[0022] (Content of the compound represented by formula (I)) The content of the compound represented by formula (I) in the non-aqueous electrolyte is not particularly limited, but is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, relative to the total amount of the non-aqueous electrolyte. The content of the compound represented by formula (I) is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.1 to 2% by mass. Only one compound represented by formula (I) may be included, or two or more may be included. When two or more compounds represented by formula (I) are included, it is preferable that the total content is within the above range.

[0023] (Method for preparing the compound represented by formula (I)) The compound represented by the above formula (I) is, for example, R 1 X and R2 Y corresponds to an acid chloride and R 3 It can be synthesized by reacting a diol equivalent to it using known methods (see J.Med.Chem., 2004, 4300-4315, etc.). The identification of the compound represented by formula (I) above in a non-aqueous electrolyte and the measurement of its content are performed using nuclear magnetic resonance (NMR) spectroscopy.

[0024] Examples of compounds represented by the above formula (I) include the following compounds 1 to 48. [ka]

[0025] Among the above compounds, it is preferable that the exemplary compounds 1 to 28 satisfy formula (II) above, and R 3 Exemplary compounds 1-16, 18, and 20-28, which have a carbon-carbon unsaturated bond at the terminus of the substituent, are more preferably R 3 Exemplary compounds 1-6, 11-14, 16, 18, and 20-28 are more preferably substituents containing a carbon-carbon double bond, R 1 and R 2 However, exemplary compounds 1-6, 11-14, 16, 18, 20-24, 26, and 28, which are hydrocarbon groups having 1 to 10 carbon atoms that may be substituted with halogen atoms, are even more preferred. These compounds can reduce initial input resistance and suppress gas generation.

[0026] [1-2. Electrolytes] Lithium salts are preferred as electrolytes for non-aqueous electrolytes. There are no particular restrictions on lithium salts, but examples include lithium fluoroborate, lithium fluorophosphate, lithium tungstate, lithium carboxylate, lithium sulfonate, lithium imide, lithium methide, lithium oxalate, and fluorine-containing organic lithium salts.

[0027] Among these, from the viewpoint of improving low-temperature power characteristics, high-rate charge / discharge characteristics, impedance characteristics, high-temperature storage characteristics, and cycle characteristics, lithium fluoroborate salts such as LiBF4; lithium fluorophosphate salts such as LiPF6, Li2PO3F, and LiPO2F2; lithium sulfonate salts such as LiFSO3 and CH3SO3Li; and lithium imide salts such as LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, and lithium cyclic 1,3-perfluoropropanedi Sulfonylimide; LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3 as lithium methide salts; lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium tris(oxalate) phosphate, etc. are preferred as lithium oxalate salts, one or more selected from LiPF6, LiN(FSO2)2, lithium bis(oxalate) borate and LiFSO3 are more preferred, and LiPF6 is particularly preferred.

[0028] The above electrolytes can be used individually or in combination of two or more in any ratio. There are no particular restrictions on the combination of two or more electrolytes, and examples include combinations of LiPF6 and LiN(FSO2)2, LiPF6 and LiBF4, LiPF6 and LiN(CF3SO2)2, LiBF4 and LiN(FSO2)2, and LiBF4, LiPF6 and LiN(FSO2)2. Among these, combinations of LiPF6 and LiN(FSO2)2, LiPF6 and LiBF4, and LiBF4, LiPF6 and LiN(FSO2)2 are preferred.

[0029] While there are no particular restrictions on the total concentration of the electrolyte, from the viewpoint of ensuring proper electrical conductivity for battery operation and sufficient output characteristics, it is typically 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass or more, relative to the total amount of the non-aqueous electrolyte, and also typically 18% by mass or less, preferably 17% by mass or less, more preferably 16% by mass or less.

[0030] (PF6 - (Ratio of the content of the compound represented by formula (I) to the content of the other compound) When LiPF6 is included as an electrolyte, PF6 - The ratio of the content of the compound represented by formula (I) [g] to the content of [p] [p] [p] [p] / PF6 - The content of [substance] is usually 0.0001 to 1, preferably 0.0001 to 0.5, and more preferably 0.0001 to 0.1. Within this range, the effect can be further enhanced. The identification and measurement of electrolyte content are performed using nuclear magnetic resonance (NMR) spectroscopy. [1-3. Non-aqueous solvents] The non-aqueous electrolyte according to the present invention, like general non-aqueous electrolytes, usually contains a non-aqueous solvent that dissolves the electrolyte as described above as its main component. There are no particular restrictions on the non-aqueous solvent, and known organic solvents can be used. Examples of organic solvents include saturated cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; linear carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ether compounds such as dimethoxymethane, diethoxymethane, ethoxymethoxymethane, tetrahydrofuran, 1,3-dioxane, and 1,4-dioxane; sulfone compounds such as 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, dimethyl sulfone, ethyl methylsulfone, and monofluoromethylmethylsulfone. Among these, saturated cyclic carbonates, linear carbonates, and carboxylic acid esters are preferred, and saturated cyclic carbonates and linear carbonates are more preferred. These non-aqueous solvents can be used individually or in combination of two or more.

[0031] [1-4. Auxiliary Agents] The non-aqueous electrolyte according to the present invention may contain various auxiliary agents different from the electrolyte and non-aqueous solvent, as long as the effects of the present invention are not impaired. Conventionally known auxiliary agents can be used as desired. The auxiliary agents can be used individually or in combination of two or more in any ratio. Examples of additives include cyclic carbonates having carbon-carbon unsaturated bonds, fluorine-containing cyclic carbonates, compounds having isocyanate groups, compounds having an isocyanuric acid skeleton, sulfur-containing organic compounds, phosphorus-containing organic compounds, silicon-containing compounds, aromatic compounds, organic compounds having cyano groups, fluorine-free carboxylic acid esters, cyclic ether compounds, carboxylic acid anhydrides, compounds containing borate anions, compounds containing phosphate anions having PF and P=O bonds, compounds containing anions having S=O bonds, and compounds containing oxalate complex anions. For example, compounds described in International Publication No. 2015 / 111676 can be cited. The amount of the auxiliary agent is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 0.001 to 10% by mass relative to the total amount of the non-aqueous electrolyte.

[0032] <2. Non-aqueous electrolyte secondary battery> The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and the above-mentioned non-aqueous electrolyte. The configuration excluding the above-mentioned non-aqueous electrolyte will be described below using a lithium-ion secondary battery as an example.

[0033] [2-1. Positive electrode] The positive electrode has a positive electrode active material capable of intercalating and releasing lithium ions on at least a portion of the current collector surface. The positive electrode active material includes a lithium transition metal compound. (2-1-1. Positive electrode active material) The following describes the positive electrode active material (lithium transition metal oxide) used in the positive electrode.

[0034] ≪2-1-1-1. Lithium transition metal oxides≫ Lithium transition metal oxides are compounds that have a structure capable of desorbing and inserting lithium ions, and are represented by the following compositional formula (1). Li 1+x MO2(1) In empirical formula (1), x is -0.1 ≤ x ≤ 0.5, and M is at least one transition metal element.

[0035] Specific examples of lithium transition metal oxides represented by the chemical formula (1) include LiCoO2, LiNiO2, LiMnO2, and LiNi 0.85 Co 0.10 Al 0.05 O2, LiLiLi 0.80 Co 0.15 Al 0.05 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.6 Co 0.2 Mn0.2 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.91 Co 0.06 Mn 0.03 O2, LiLiLi 0.91 Co 0.06 Al 0.03 O2, LiLiLi 0.90 Co 0.03 Al 0.07 O2, Li 1.00 Ni 0.61 Co 0.20 Mn 0.19 Examples include O2. Among these, one selected from LiCoO2, LiNiO2, and LiMnO2 is preferred from the viewpoint of reducing initial input resistance and suppressing gas generation, with LiCoO2 being more preferred.

[0036] The positive electrode active material is identified by ICP emission spectroscopy after wet decomposition of the sample.

[0037] ≪2-1-1-2. Introduction of different elements≫ Lithium transition metal oxides may contain elements other than those included in any of the above compositional formulas (1) (other elements).

[0038] ≪2-1-1-3. Surface Coating≫ As the positive electrode, a positive electrode active material may be used in which a substance with a different composition from the positive electrode active material (surface-adhered substance) is attached to its surface. Examples of surface-adhering substances include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate. These surface-adhering substances can be attached to the surface of the positive electrode active material by, for example, dissolving or suspending them in a solvent, impregnating and adding them to the positive electrode active material, and then drying them. The amount of surface-adhering material is typically 1 μmol / g to 1 mmol / g relative to the positive electrode active material, and preferably 10 μmol / g to 1 mmol / g. In this specification, a positive electrode active material with the above-mentioned surface-adhered substance attached to its surface is also referred to as a "positive electrode active material."

[0039] ≪2-1-1-4. Blend≫ The positive electrode active material can be used alone or in combination of two or more materials in any ratio.

[0040] (2-1-2. Positive electrode configuration and manufacturing method) The positive electrode using the positive electrode active material can be manufactured by conventional methods. Specifically, the positive electrode can be obtained by a coating method in which the positive electrode active material, binder, and optionally conductive material and thickener are dry-mixed to form a sheet, which is then pressed onto the positive electrode current collector, or by dissolving or dispersing these materials in a liquid medium such as an aqueous solvent or an organic solvent to form a slurry, which is then applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector. Alternatively, for example, the positive electrode active material may be roll-molded to form a sheet electrode, or it may be compressed to form a pellet electrode. The following describes the process of sequentially applying and drying the slurry onto the positive electrode current collector.

[0041] ≪2-1-2-1. Content of positive electrode active material≫ The content of the positive electrode active material in the positive electrode active material layer is typically 80-99.5% by mass.

[0042] ≪2-1-2-2. Electrode density≫ The positive electrode active material layer obtained by applying and drying a binder, conductive material, etc., is preferably compacted by hand press, roller press, etc., in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer present on the current collector is usually 1.5 to 4.5 g / cm³. 3 That is the case.

[0043] ≪2-1-2-3. Binding Agent≫ As a binder, when forming the positive electrode active material layer by a coating method, the type of material is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium for the slurry. For example, fluororesins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene are preferred due to their weather resistance, chemical resistance, heat resistance, and flame retardancy; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide are preferred. Furthermore, mixtures of the above polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, etc., can also be used. The binder can be used alone or in combination of two or more types in any ratio. Furthermore, when a resin is used as a binder, the weight-average molecular weight of the resin can be arbitrary as long as it does not impair the effects of the present invention, and is usually between 1 and 3 million. When the molecular weight is within this range, the strength of the electrode is improved, and the electrode can be formed suitably. The binder content in the positive electrode active material layer is typically 0.1 to 80% by mass.

[0044] ≪2-1-2-4. Conductive Materials≫ Any known conductive material can be used as the conductive material. Specific examples include metallic materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon-based materials such as amorphous carbon such as needle coke. The conductive material can be used alone or in combination of two or more materials in any ratio. The conductive material is usually included in the positive electrode active material layer in an amount of 0.01 to 50% by mass.

[0045] ≪2-1-2-5. Current Collector≫ The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, with aluminum being preferred. Examples of current collector shapes include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal. Among these, metal foil or metal thin film is preferred. The metal thin film may be formed in a mesh shape as appropriate. When the shape of the positive electrode current collector is plate-shaped or film-shaped, the thickness of the current collector can be arbitrary, but is usually between 1 μm and 1 mm.

[0046] ≪2-1-2-6. Thickness of the positive electrode plate≫ While the thickness of the positive electrode plate is not particularly limited, from the viewpoint of high capacity and high output, the thickness of the positive electrode active material layer, obtained by subtracting the thickness of the current collector from the thickness of the positive electrode plate, is typically 10 to 500 μm on one side of the current collector.

[0047] ≪2-1-2-7. Surface coating of the positive electrode plate≫ The positive electrode plate may be one on which a substance with a different composition from the positive electrode plate is attached to its surface, and the same substance as the surface-attached substance that may be attached to the surface of the positive electrode active material is used.

[0048] [2-2. Negative electrode] The negative electrode has a negative electrode active material capable of intercalating and releasing lithium ions on at least a portion of the current collector surface.

[0049] (2-2-1. Negative electrode active material) There are no particular restrictions on the negative electrode active material used in the negative electrode, as long as it is capable of electrochemically intercalating and releasing metal ions. Specific examples include (i) carbon-based materials, (ii) materials containing metal elements and / or metalloid elements that can alloy with Li, (iii) lithium-containing metal composite oxide materials, and mixtures thereof. Among these, it is preferable to use (i) carbon-based materials, (ii) materials containing metal elements and / or metalloid elements that can alloy with Li, and (iv) mixtures of materials containing metal elements and / or metalloid elements that can alloy with Li and graphite, as these offer good cycle characteristics, safety, and excellent continuous charging characteristics. These can be used individually or in combination of two or more in any ratio.

[0050] ≪2-2-1-1. Carbon-based materials≫ (i) Examples of carbon-based materials include natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. Among these, natural graphite is preferred. Carbon-based materials can be used individually or in combination of two or more in any ratio. Examples of natural graphite include scaly graphite, flake graphite, and / or graphite particles obtained by treating these graphites, such as spheroidization or densification. Among these, spherical or ellipsoidal graphite particles obtained by spheroidization treatment are preferred from the viewpoint of particle packing properties or charge / discharge rate characteristics. The average particle size (d50) of graphite particles is typically 1 to 100 μm.

[0051] ≪2-2-1-2. Physical Properties of Carbon-Based Materials≫ The carbon-based material used as the negative electrode active material preferably satisfies at least one of the following physical properties and characteristics such as shape, as shown in (1) to (4), and more preferably satisfies multiple items simultaneously. (1) X-ray diffraction parameters The d-value (interlayer distance) of the lattice plane (002 plane) of carbon-based materials, as determined by X-ray diffraction using the JSPS method, is typically 0.335 to 0.360 nm. Furthermore, the crystallite size (Lc) of carbon-based materials, as determined by X-ray diffraction using the JSPS method, is 1.0 nm or greater. (2) Volume-based average particle size The volume-based average particle size of carbon-based materials is the volume-based average particle size (median diameter) determined by laser diffraction and scattering, and is typically between 1 and 100 μm. (3) Raman R value, Raman half-width The Raman R value of carbon-based materials is measured using argon ion laser Raman spectroscopy and is typically between 0.01 and 1.5. Also, 1580 cm² of carbon-based materials -1 The Raman width at half maximum in the vicinity is not particularly restricted, but is usually 10-100 cm. -1 That is the case. (4) BET specific surface area The BET specific surface area of ​​carbon-based materials is the value of the specific surface area measured using the BET method, and is typically between 0.1 and 100 m². 2 ·g -1 That is the case. The negative electrode active material may contain two or more carbon-based materials with different properties. The properties referred to here are one or more characteristics selected from the group consisting of X-ray diffraction parameters, volume-based average particle size, Raman R value, Raman full width at half maximum, and BET specific surface area. Examples of materials containing two or more carbon-based materials with different properties include those in which the volume-based particle size distribution is not symmetrical when centered on the median diameter, those containing two or more carbon-based materials with different Raman R values, and those with different X-ray diffraction parameters.

[0052] ≪2-2-1-3. Materials containing metallic and / or metalloid elements that can be alloyed with Li≫ (ii) Any material containing a metal element and / or metalloid element that can be alloyed with Li can be used, but from the viewpoint of capacity and cycle life, it is preferable that the material be a metal or metalloid selected from the group consisting of, for example, Sb, Si, Sn, Al, As, and Zn. Furthermore, if the material containing a metal element and / or metalloid element that can be alloyed with Li contains two or more metals, the material may be an alloy material made of an alloy of these metals. Furthermore, materials containing metallic and / or metalloid elements that can alloy with Li include oxides, nitrides, and carbides of metals and / or metalloids. These materials may contain two or more metals that can alloy with Li. Among these, materials containing Si are preferred, and metallic Si (hereinafter also referred to as "Si") or Si-containing inorganic compounds are more preferred in terms of high capacity. In this specification, Si or Si-containing inorganic compounds are collectively referred to as "Si compounds". The content of material containing a metallic element and / or metalloid element that can alloy with Li, relative to the total mass of the negative electrode active material, is preferably 0.1 to 25% by mass. Furthermore, materials containing metallic and / or metalloid elements that can be alloyed with Li may already be alloyed with Li during the production of the negative electrode, as described later, and Si compounds are preferred as such materials in terms of increasing capacity.

[0053] As for Si compounds, SiO x Examples include (0≦x≦2), etc. Li is a metal alloying compound. y Si(0 <y≦4.4)、Li 2z SiO 2+z(0 < z ≤ 2) and the like can be mentioned. As the Si compound, silicon oxide (SiO x1 , 0 < x1 ≤ 2) is preferable in that it has a larger theoretical capacity compared to graphite, and amorphous Si or nano-sized Si crystals are preferable in that alkali ions such as lithium ions can easily enter and exit, and high capacity can be obtained. When the material containing a metal element and / or a metalloid element capable of alloying with Li is in the form of particles, the average particle diameter (d50) of the particles is usually 0.01 to 10 μm from the viewpoint of cycle life.

[0054] <<2-2-1-4. Lithium-containing metal composite oxide material>> (iii) The lithium-containing metal composite oxide material is not particularly limited as long as it can occlude and release lithium ions. Specifically, from the viewpoint of high current density charge-discharge characteristics, a lithium-containing metal composite oxide material containing titanium is preferable, a composite oxide of lithium and titanium (hereinafter, also referred to as "lithium titanium composite oxide") is more preferable, and a lithium titanium composite oxide having a spinel structure is even more preferable because it greatly reduces the output resistance. Also, lithium and / or titanium of the lithium titanium composite oxide may be substituted with at least one element selected from the group consisting of other metal elements, for example, Al, Ga, Cu, and Zn. As the lithium titanium composite oxide, Li 4 / 3 Ti 5 / 3 O4, Li1Ti2O4, and Li 4 / 5 Ti 11 / 5 O4 are preferable. Also, as the lithium titanium composite oxide in which a part of lithium and / or titanium is substituted with other elements, for example, Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 is also preferable.

[0055] <<2-2-1-5. Mixture of a material containing a metal element and / or a metalloid element capable of alloying with Li and graphite>> (iv) A mixture of graphite and a material containing a metal element and / or metalloid element that can alloy with Li may be a mixture in which the material containing the metal element and / or metalloid element that can alloy with Li and graphite are mixed in the state of being independent particles, or it may be a composite in which the material containing the metal element and / or metalloid element that can alloy with Li is present on the surface or inside the graphite particles. The proportion of materials containing metal elements and / or metalloids that can alloy with Li, relative to the total amount of graphite, is usually between 1% by mass and 99% by mass. The identification and content measurement of the negative electrode active material are performed by ICP emission spectroscopy after alkali fusion of the sample.

[0056] (2-2-2. Negative electrode configuration and manufacturing method) The negative electrode may be manufactured using any known method, as long as it does not impair the effects of the present invention. For example, it can be manufactured by adding a binder, a liquid medium such as an aqueous solvent or an organic solvent, and optionally a thickener, a conductive material, a filler, etc., to the negative electrode active material to form a slurry, applying this slurry to a current collector, drying it, and then pressing it to form a negative electrode active material layer.

[0057] ≪2-2-2-1. Content of negative electrode active material≫ The content of the negative electrode active material in the negative electrode active material layer is typically 80-99.5% by mass.

[0058] ≪2-2-2-2. Electrode density≫ The negative electrode active material layer obtained by applying and drying a binder, thickener, etc., is preferably compacted by hand press, roller press, or the like in order to increase the packing density of the negative electrode active material. The electrode structure when the negative electrode active material is used as an electrode is not particularly limited, but the density of the negative electrode active material layer present on the current collector is typically 1 to 2.2 g / cm³. 3 That is the case.

[0059] ≪2-2-2-3. Binding Agent≫ The binder can be any material that is stable with non-aqueous electrolytes or liquid media used in electrode manufacturing, and is not particularly limited. Specific examples include rubbery polymers such as styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene rubber, as well as fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and tetrafluoroethylene-ethylene copolymers. These can be used individually or in combination of two or more in any ratio. The binder content relative to the negative electrode active material is typically 0.1 to 20% by mass. In particular, when the binder contains a rubbery polymer such as SBR as its main component, the binder content relative to the negative electrode active material is usually 0.1 to 5% by mass. Furthermore, when the binder contains a fluorine-based polymer such as polyvinylidene fluoride as its main component, the binder content relative to the negative electrode active material is usually 1 to 15% by mass.

[0060] ≪2-2-2-4. Thickening Agents≫ Thickening agents are typically used to adjust the viscosity of slurries. While not particularly limited, examples of thickening agents include carboxymethylcellulose and its salts, methylcellulose, hydroxymethylcellulose, ethylcellulose, and polyvinyl alcohol. These can be used individually or in combination of two or more in any ratio. When a thickening agent is used, the amount of the thickening agent relative to the negative electrode active material is usually 0.1 to 5% by mass.

[0061] ≪2-2-2-5. Current Collector≫ Any known material can be used as the current collector for holding the negative electrode active material. Examples of negative electrode current collectors include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred in terms of ease of processing and cost. Examples of the negative electrode current collector shape include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal. Among these, metal foil or metal thin film is preferred. The metal thin film may be formed in a mesh shape as appropriate. When the negative electrode current collector is plate-shaped or film-shaped, the thickness of the current collector can be arbitrary, but is usually between 1 μm and 1 mm.

[0062] ≪2-2-2-6. Thickness of the negative electrode plate≫ The thickness of the negative electrode (negative electrode plate) is designed to match the positive electrode (positive electrode plate) used and is not particularly limited; however, the thickness of the negative electrode active material layer, obtained by subtracting the thickness of the current collector from the thickness of the negative electrode material, is usually 15 to 300 μm.

[0063] ≪2-2-2-7. Surface coating of the negative electrode plate≫ The negative electrode plate may also be one in which a substance with a different composition from the negative electrode active material is attached to its surface (surface-attached substance). Examples of surface-attached substances include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate.

[0064] [2-3. Separator] A separator is usually placed between the positive and negative electrodes to prevent short circuits. In this case, the non-aqueous electrolyte is typically used by impregnating this separator. There are no particular restrictions on the material or shape of the separator; any known material or shape can be used as long as it does not impair the effects of the present invention.

[0065] [2-4.Battery design] (2-4-1. Electrode group) The electrode group may be either a laminated structure in which the positive electrode plate and the negative electrode plate are separated by the separator, or a structure in which the positive electrode plate and the negative electrode plate are spirally wound around the separator. The ratio of the volume of the electrode group to the internal volume of the battery (electrode group occupancy rate) is usually between 40% and 90%.

[0066] (2-4-2. Current collection structure) In the case of electrode groups with the aforementioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to a terminal is preferably used. A structure that reduces resistance by providing multiple terminals within the electrode is also preferably used. In the case of electrode groups with the aforementioned wound structure, the internal resistance can be reduced by providing multiple lead structures in both the positive and negative electrodes and bundling them to a terminal.

[0067] (2-4-3. Protective elements) As protective elements, PTC (Positive Temperature Coefficient) elements whose resistance increases with heat generation due to excessive current, thermal fuses, thermistors, and valves (current interruption valves) that interrupt the current flowing through the circuit due to a rapid rise in internal pressure or temperature of the battery in the event of abnormal heat generation can be used. It is preferable to select the above protective elements that do not operate under normal high-current use, and it is even more preferable to design the system so that abnormal heat generation or thermal runaway does not occur even without protective elements.

[0068] (2-4-4. Exterior) Non-aqueous electrolyte secondary batteries are typically constructed by housing the non-aqueous electrolyte, negative electrode, positive electrode, separator, etc., according to the present invention within an outer casing (outer case). There are no restrictions on this outer casing; any known material can be used as long as it does not impair the effects of the present invention. The material of the outer casing can be any substance that is stable with respect to the non-aqueous electrolyte used, and is not particularly limited. However, from the viewpoint of weight reduction and cost, metals such as iron, aluminum, aluminum alloys, or laminate films are preferably used. Outer cases using the above-mentioned metals include those that create a sealed structure by welding the metals together using laser welding, resistance welding, or ultrasonic welding, or those that create a crimped structure using the above-mentioned metals via a resin gasket.

[0069] (2-4-5.Shape) The shape of the outer casing of the non-aqueous electrolyte secondary battery is arbitrary and can be any of the following: cylindrical, rectangular, laminated, coin-shaped, large, etc. [Examples]

[0070] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0071] The compounds used in this example are listed below.

[0072] [ka] Compound 2: 1-Butene-3,4-diol dimethanesulfonate

[0073] [ka] Comparative compound 1: 2-butyne-1,4-diol dimethanesulfonate

[0074] [ka] Comparative compound 2: 1,4-butanediol dimethanesulfonate (busulfan)

[0075] <Preparation of Compound 2> 5 g (56.75 mmol) of 3-butene-1,2-diol was placed in a 500 ml flask, dissolved in 200 ml of dichloromethane, cooled to 0°C, and then 12.63 g (124.85 mmol) of triethylamine was added. Next, 14.33 g (125.10 mmol) of methanesulfonyl chloride dissolved in 100 ml of dichloromethane was added dropwise, and the mixture was stirred at 0°C for 1.5 hours from the end of the dropwise addition, and then stirred at 20°C for 14.5 hours. The semi-solution mixture was poured into 150 ml of 1 M hydrochloric acid aqueous solution, and the organic phase and aqueous phase were separated. The aqueous phase was extracted with dichloromethane (300 ml x 3 times). The combined organic phase was washed with 150 ml of 1 M hydrochloric acid aqueous solution, then twice with 150 ml of saturated sodium bicarbonate aqueous solution, then with 300 ml of saturated sodium chloride aqueous solution, and then twice with 400 ml of deionized water. After drying with anhydrous sodium sulfate, the mixture was filtered, and the filtrate was concentrated under reduced pressure at room temperature to obtain a crude product. The obtained crude product was column purified (silica, dichloromethane) to obtain 11.9 g of compound 2 (yield 85.9%). 1 H NMR:(CDCl3, 400MHz): δ=5.93-5.83(m,1H),5.62(d,J=16.2Hz,1H),5.53(d,J=10.0Hz,1H),5.32-5.29(m,1H),4.40-4.29(m,2H),3.10(s,3H),3.08(s,3H).

[0076] <Example 1> (Preparation of non-aqueous electrolyte) A non-aqueous electrolyte was prepared by dissolving 1.2 mol / L (14.5% by mass, as the concentration in the non-aqueous electrolyte) of thoroughly dried LiPF6 in a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 3:4:3) under a dry argon atmosphere, and then dissolving compound 2 to a concentration of 0.5% by mass. The table shows the PF6 of the electrolyte LiPF6. - The ratio of the mass of compound 2 content to the content of PF6 [Content of compound 2 / PF6] - The content of [the substance] is also shown.

[0077] (Fabrication of the positive electrode) 97 parts by mass of LiCoO2 as the positive electrode active material, 1.5 parts by mass of acetylene black as the conductive material, and 1.5 parts by mass of polyvinylidene fluoride (PVdF) as the binder were mixed and slurryed in N-methyl-2-pyrrolidone. This slurry was then uniformly coated onto a 15 μm thick aluminum foil, dried, and roll-pressed to form the positive electrode.

[0078] (Fabrication of the negative electrode) 49 parts by mass of graphite powder were mixed with 50 parts by mass of aqueous carboxymethylcellulose sodium dispersion (1% by mass concentration of carboxymethylcellulose sodium) as a thickener and 1 part by mass of aqueous styrene-butadiene rubber dispersion (49% by mass concentration of styrene-butadiene rubber) as a binder, and the mixture was prepared by mixing in a disperser to form a slurry. The resulting slurry was uniformly applied to a 10 μm thick copper foil, dried, and roll-pressed to form the negative electrode.

[0079] (Manufacturing of non-aqueous electrolyte secondary batteries) The positive electrode, negative electrode, and polyolefin separator described above were stacked in the order of negative electrode, separator, and positive electrode. The resulting battery element was wrapped in an aluminum laminate film, injected with the aforementioned non-aqueous electrolyte, and then vacuum-sealed to produce a sheet-like non-aqueous electrolyte secondary battery.

[0080] <Comparative Example 1> A sheet-like non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1, except that compound 2 was not used.

[0081] <Comparative Examples 2 and 3> A sheet-like non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1, except that compound 2 was the compound shown in Table 1.

[0082] [evaluation] (Evaluation of non-aqueous electrolyte secondary batteries: Initial input resistance) The room-temperature resistance of the fabricated non-aqueous electrolyte secondary battery was evaluated as follows. In a constant temperature bath at 25°C, a sheet-shaped non-aqueous electrolyte secondary battery was charged with a constant current equivalent to 0.05C (1C is defined as the current value required to discharge the rated capacity based on the 1-hour discharge rate in 1 hour; the same applies hereinafter) until it reached 3.7V. Then, it was charged with a constant current-constant voltage charge (hereinafter also referred to as "CC-CV charge") at 0.2C until it reached 4.25V, and subsequently discharged with a constant current at 0.2C until it reached 2.5V. Furthermore, the non-aqueous electrolyte secondary battery was stabilized by CC-CV charging at 0.2C to 4.1V and then storing it at 60°C for 24 hours. Subsequently, it was discharged at 25°C at 0.2C to 2.5V, and then CC-CV charged at 0.2C to 3.7V. These batteries were then charged at -20°C at 0.05C, 0.1C, and 0.25C respectively, and the voltage was measured after 10 seconds. The internal resistance was calculated from this current-voltage line and defined as the "initial input resistance". Next, CC-CV charging was performed at 0.2C until the voltage reached 4.25V, and the batteries were left at 85°C for 24 hours. Before and after this period, the non-aqueous electrolyte secondary batteries were immersed in an ethanol bath at room temperature and their volume was measured. The volume change during this period was defined as the "gas generation amount" of the battery. Furthermore, it is preferable for the initial input resistance and gas generation amount to be as small as possible.

[0083] Table 1 shows the initial input resistance and gas generation amount for Example 1 and Comparative Examples 1-3. The initial input resistance and gas generation amounts in the table are relative values ​​with Comparative Example 1 set to 100.

[0084] [Table 1]

[0085] As is clear from Table 1, the non-aqueous electrolyte secondary battery containing compound 2 in the non-aqueous electrolyte (Example 1) exhibits reduced initial input resistance and gas generation compared to the case without compound 2 (Comparative Example 1). On the other hand, non-aqueous electrolyte secondary batteries (Comparative Examples 2-3) equipped with electrolytes containing comparative compounds 1-2 disclosed in the prior art (Patent Document 1) tend to have higher initial input resistance and gas generation compared to the case with compound 2 (Example 1). As shown in the experimental results above, the non-aqueous electrolyte containing the compound represented by formula (I) achieved both a reduction in the initial input resistance and a suppression of gas generation in the non-aqueous electrolyte secondary battery.

Claims

1. A non-aqueous electrolyte solution comprising an electrolyte, a non-aqueous solvent, and a compound represented by the following formula (I): [Formula 1] (In formula (I), X and Y are sulfur-containing ester structures; R １ and R ２ each independently represents a halogen atom or an organic group having 1 to 10 carbon atoms; R ３ is an alkylene group having 3 to 20 carbon atoms and having a substituent containing at least one carbon-carbon unsaturated bond.

2. 2. The nonaqueous electrolyte solution according to claim 1, wherein the substituent containing a carbon-carbon unsaturated bond is a substituent containing a carbon-carbon unsaturated bond at a terminal thereof.

3. 2. The nonaqueous electrolyte solution according to claim 1, wherein the substituent containing a carbon-carbon unsaturated bond is an alkenyl group.

4. The R ３ The nonaqueous electrolyte according to claim 1, wherein the alkylene group represented by the formula (I) has 3 to 10 carbon atoms.

5. The R １ and R ２ and each independently represent a hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom.

6. The non-aqueous electrolyte solution according to claim 1, wherein the content of the compound represented by formula (I) is 0.001 to 10 mass% based on the total amount of the non-aqueous electrolyte solution.

7. The electrolyte is LiPF ６ Contains PF ６ － The mass ratio of the content of the compound represented by formula (I) to the content of the compound represented by formula (I) / PF ６ － The nonaqueous electrolyte solution according to claim 1, wherein the content of

8. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of claims 1 to 7.

9. 9. The nonaqueous electrolyte secondary battery according to claim 8, wherein the positive electrode contains a lithium transition metal oxide represented by the following composition formula (1): Li １＋ｘ M.O. ２ (1) (In the composition formula (1), x is −0.1 or more and 0.5 or less, and M is at least one transition metal element.)

10. A compound represented by the following formula (I): [Case 2] (In formula (I), X and Y are sulfur-containing ester structures; R １ and R ２ each independently represents a halogen atom or an organic group having 1 to 10 carbon atoms; R ３ is an alkylene group having 3 to 20 carbon atoms and having a substituent containing at least one carbon-carbon unsaturated bond.

11. The compound according to claim 10, wherein the substituent containing a carbon-carbon unsaturated bond is a substituent containing a terminal carbon-carbon unsaturated bond.

12. The compound according to claim 10, wherein the substituent containing a carbon-carbon unsaturated bond is an alkenyl group.

13. The R ３ The compound according to claim 10, wherein the alkylene group represented by the formula (I) has 3 to 10 carbon atoms.

14. The R １ and R ２ and each independently represent a hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom.

15. The compound according to any one of claims 10 to 14, wherein the compound represented by formula (I) is a compound represented by the following formula (II): [C3] (In formula (II), R ４ and R ５ each independently represents a halogen atom or an organic group having 1 to 10 carbon atoms; R ６ is an alkylene group having 3 to 20 carbon atoms and having a substituent containing at least one carbon-carbon unsaturated bond.

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