Electrolyte for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Abstract

The present invention relates to an electrolyte solution for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery. The present disclosure relates to an electrolyte solution for a nonaqueous electrolyte secondary battery containing a silane compound having two or more trialkoxysilyl groups. According to the present disclosure, an electrolyte solution for a nonaqueous electrolyte secondary battery is provided that can suppress degradation of the negative electrode in the nonaqueous electrolyte secondary battery.

Description

Technical Field

[0001] The present disclosure relates to an electrolyte solution for a nonaqueous electrolyte secondary battery, and further relates to a nonaqueous electrolyte secondary battery including the electrolyte solution. Background Art

[0002] International Publication No. 2017 / 051500 proposes applying a protective film containing a silane coupling agent to the surface of the negative electrode in a non-aqueous electrolyte secondary battery to suppress degradation of the negative electrode. Japanese Patent Application Laid-Open No. 2011-222450 proposes incorporating a specific difluorosilane compound into the electrolyte of a non-aqueous electrolyte secondary battery to suppress increases in internal resistance and high-temperature degradation of the non-aqueous electrolyte. Summary of the Invention

[0003] When a protective film comprising a silane compound is formed by surface treatment of the negative electrode, as described in International Publication No. 2017 / 051500, the material comprising the silane compound has significant expansion and contraction, so the film may rupture during cycling, causing rapid degradation. Furthermore, as described in Japanese Patent Application Laid-Open No. 2011-222450, when an additive comprising a silane compound is added to the electrolyte to protect the negative electrode, the additive may completely undergo reductive decomposition at the negative electrode, causing the decomposition products to expand and contract during cycling, leading to rupture and rapid degradation. Alternatively, residual additives in the electrolyte at the positive electrode may oxidatively decompose, rendering the negative electrode incapable of protecting the negative electrode.

[0004] An object of the present disclosure is to provide an electrolytic solution for a nonaqueous electrolyte secondary battery capable of suppressing degradation of a negative electrode in the nonaqueous electrolyte secondary battery.

[0005] The present disclosure provides the following nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery.

[0006] [1] An electrolyte solution for a non-aqueous electrolyte secondary battery, comprising a silane compound having two or more trialkoxysilyl groups.

[0007] [2] The electrolyte solution for a non-aqueous electrolyte secondary battery according to [1], wherein the trialkoxysilyl group is one selected from the group consisting of a trimethoxysilyl group, a triethoxysilyl group, and a tripropoxysilyl group.

[0008] [3] The electrolyte solution for a non-aqueous electrolyte secondary battery according to [1] or [2], wherein the silane compound further has a saturated hydrocarbon group having 2 to 6 carbon atoms.

[0009] [4] The electrolyte solution for a non-aqueous electrolyte secondary battery according to any one of [1] to [3], wherein the silane compound is represented by the following formula (1):

[0010] [Chemistry 1]

[0011]

[0012] In the formula, a=1~4, b=3~7, c=2~6, d=4~12, and n=1 or 2.

[0013] [5] The electrolyte solution for a non-aqueous electrolyte secondary battery according to any one of [1] to [4], comprising:

[0014] A compound represented by the following formula (1-1):

[0015] [Chemistry 2]

[0016]

[0017] Wherein, a=1-4, b=3-7, c=2-6, d=4-12; and

[0018] A compound represented by the following formula (1-2):

[0019] [Chemistry 3]

[0020]

[0021] In the formula, a=1~4, b=3~7, c=2~6, d=4~12.

[0022] [6] The electrolyte solution for a non-aqueous electrolyte secondary battery according to any one of [1] to [5], wherein the concentration of the silane compound in the electrolyte solution is 1×10 3 ~1×10 5 ppm.

[0023] [7] A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte secondary battery electrolyte according to any one of [1] to [6], a positive electrode, and a negative electrode.

[0024] [8] The non-aqueous electrolyte secondary battery according to [7], wherein the negative electrode comprises negative electrode active material particles containing an alloy-based negative electrode active material.

[0025] [9] The nonaqueous electrolyte secondary battery according to [8], wherein the surface of the negative electrode active material particle has a structure containing Si or O.

[0026] The above and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram showing an example of the non-aqueous electrolyte secondary battery disclosed herein.

[0028] Figure 2 This is a schematic diagram showing an example of an electrode body in this embodiment. DETAILED DESCRIPTION

[0029] The following describes embodiments of the present invention with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. In all the following drawings, the scales of the components are adjusted appropriately to facilitate understanding, and the proportions of the components shown in the drawings are not necessarily consistent with the proportions of the actual components.

[0030] <Electrolyte for non-aqueous electrolyte secondary batteries>

[0031] The electrolyte for a non-aqueous electrolyte secondary battery (hereinafter, for simplicity, also referred to as "electrolyte") of one embodiment of the present disclosure is a liquid electrolyte. The electrolyte contains a silane compound. The electrolyte further contains a solvent and a supporting electrolyte. In addition to these components, the electrolyte may further contain optional additives such as a surfactant.

[0032] At least a portion of the electrolyte is impregnated into an electrode assembly of a non-aqueous electrolyte secondary battery, described below. The entire electrode assembly may be impregnated with the electrolyte. Alternatively, a portion of the electrolyte may be impregnated into the electrode assembly. For example, a portion of the electrolyte may be stored outside the electrode assembly (e.g., at the bottom of the outer packaging, described below).

[0033] [Silane compound]

[0034] The electrolyte contains a silane compound having two or more trialkoxysilyl groups. The electrolyte may contain, for example, two or more silane compounds having two or more trialkoxysilyl groups, preferably two. The number of trialkoxysilyl groups possessed by the silane compound may be, for example, 2 or 4. The trialkoxysilyl group is represented by the following formula:

[0035] -Si(-OC a H b )3

[0036] [wherein a=1 to 4, b=3 to 7] Examples of the trialkoxysilyl group include trimethoxysilyl, triethoxysilyl, and tripropoxysilyl. Preferably, the trialkoxysilyl group is one selected from the group consisting of trimethoxysilyl, triethoxysilyl, and tripropoxysilyl. More preferably, the trialkoxysilyl group is trimethoxysilyl and triethoxysilyl.

[0037] The silane compound may further have a saturated hydrocarbon group having 2 to 6 carbon atoms. The saturated hydrocarbon group having 2 to 6 carbon atoms is represented by the following formula:

[0038] -C c Hd -

[0039] [In the formula, c = 2 to 6, d = 4 to 12] The saturated hydrocarbon group having 2 to 6 carbon atoms is preferably a saturated hydrocarbon group having 2 or 6 carbon atoms. The saturated hydrocarbon group having 2 to 6 carbon atoms may be linear or branched, and is preferably linear.

[0040] The silane compound can be, for example, a compound represented by the above formula (1). It is preferred that the above formula (1) does not have a double bond.

[0041] The electrolyte solution may contain either or both of the compound represented by the above formula (1-1) and the compound represented by the above formula (1-2). Preferably, neither formula (1-1) nor formula (1-2) has a double bond. In formula (1-1), from the viewpoint of suppressing degradation of the negative electrode, preferably a=1, c=2 or 6. In formula (1-2), from the viewpoint of suppressing degradation of the negative electrode, preferably a=1, c=2 or 6.

[0042] From the viewpoint of suppressing deterioration of the negative electrode, the electrolyte solution preferably contains the compound represented by the above formula (1-1) and the compound represented by the above formula (1-2).

[0043] The concentration of the silane compound in the electrolyte solution (when containing a plurality of silane compounds, the total concentration of all silane compounds) can be, for example, 1 to 1×10 6 ppm, preferably more than 1.5×10 2 ppm and 1×10 6 ppm or less, more preferably 5.0×10 2 ~1×10 5 ppm, more preferably 1×10 3 ~1×10 5 ppm.

[0044] In the case where the electrolyte solution contains the compound represented by formula (1-1), the concentration of the compound represented by formula (1-1) in the electrolyte solution may be, for example, 1×10 2 ~1×10 6 ppm, preferably 1×10 4 ~1×10 5 ppm.

[0045] When the electrolyte solution contains the compound represented by formula (1-1) and the compound represented by formula (1-2), the concentration of the compound represented by formula (1-2) in the electrolyte solution may be, for example, 1 to 1×10 4 ppm, preferably 10 to 1×10 2 ppm.

[0046] [Solvent]

[0047] The solvent is aprotic. The solvent may contain optional components. For example, the solvent may contain at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), monofluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), methyl formate (MF), methyl acetate (MA), methyl propionate (MP) and γ-butyrolactone (GBL).

[0048] [Supporting electrolyte]

[0049] The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may include, for example, at least one selected from LiPF6, LiBF4, and LiN(FSO2)2. The supporting electrolyte may have a molar concentration of, for example, 0.5 mol / L to 5.0 mol / L. The supporting electrolyte may also have a molar concentration of, for example, 0.8 mol / L to 1.4 mol / L.

[0050] <Non-aqueous Electrolyte Secondary Battery>

[0051] Another embodiment of the present invention includes a nonaqueous electrolyte secondary battery (hereinafter, for simplicity, also referred to as a battery) comprising an electrolyte for a nonaqueous electrolyte secondary battery, a positive electrode, and a negative electrode. The electrolyte for the nonaqueous electrolyte secondary battery is subject to the above description of the electrolyte. The positive electrode and the negative electrode will be described later.

[0052] While referring to Figure 1 While explaining the battery. Figure 1 The battery 100 shown can be used in any application. For example, the battery 100 can be used as a main power source or a power auxiliary power source in an electric vehicle. By connecting multiple batteries 100, a battery module or a battery pack can be formed.

[0053] The battery 100 has a predetermined rated capacity, for example, 1 to 300 Ah, 1 to 50 Ah, 2 to 25 Ah, 3 to 5 Ah, or 4 to 4.2 Ah.

[0054] The battery 100 includes an outer packaging body 90. The outer packaging body 90 is square (flat rectangular). However, the square is just an example. The outer packaging body 90 can have any shape. The outer packaging body 90 can be, for example, cylindrical or bag-shaped. The outer packaging body 90 can be made of, for example, Al (aluminum) alloy. The outer packaging body 90 contains the electrode body 50 and the electrolyte (not shown). The outer packaging body 90 can include, for example, a sealing plate 91 and an outer packaging can 92. The sealing plate 91 seals the opening of the outer packaging can 92. For example, the sealing plate 91 and the outer packaging can 92 can be joined by laser welding.

[0055] The sealing plate 91 is provided with a positive terminal 81 and a negative terminal 82. The sealing plate 91 may further be provided with an injection port and a gas discharge valve. The electrolyte can be injected into the interior of the outer packaging body 90 through the injection port. The electrode body 50 is connected to the positive terminal 81 via the positive electrode current collecting component 71. The positive electrode current collecting component 71 may be, for example, an Al plate. The electrode body 50 is connected to the negative terminal 82 via the negative electrode current collecting component 72. The negative electrode current collecting component 72 may be, for example, a Cu (copper) plate.

[0056] Figure 2 This is a schematic diagram showing an example of an electrode body in this embodiment.

[0057] The electrode body 50 is of a wound type. The electrode body 50 includes a positive electrode 10, a separator 30, and a negative electrode 20. That is, the battery 100 includes a positive electrode 10, a negative electrode 20, and an electrolyte. The positive electrode 10, the separator 30, and the negative electrode 20 are all strip-shaped sheets. The electrode body 50 may include a plurality of separators 30. The electrode body 50 is formed by stacking the positive electrode 10, the separator 30, and the negative electrode 20 in sequence and winding them into a spiral shape. One of the positive electrode 10 or the negative electrode 20 may be sandwiched by the separator 30. Alternatively, both the positive electrode 10 and the negative electrode 20 may be sandwiched by the separator 30. The electrode body 50 may be formed into a flat shape after winding. In addition, the wound type is an example. The electrode body 50 may be, for example, of a stacked (stacked) type.

[0058] [positive electrode]

[0059] The positive electrode 10 may include, for example, a positive electrode substrate 11 and a positive electrode active material layer 12. The positive electrode substrate 11 is a conductive sheet. The positive electrode substrate 11 may be, for example, an Al alloy foil or the like. The "thickness" of each component in this specification can be measured by a constant pressure thickness tester (thickness gauge). The positive electrode substrate 11 may have, for example, a thickness of 10 to 30 μm. The positive electrode active material layer 12 is arranged on the surface of the positive electrode substrate 11. The positive electrode active material layer 12 may, for example, be arranged only on one side of the positive electrode substrate 11. The positive electrode active material layer 12 may also, for example, be arranged on both the front and back sides of the positive electrode substrate 11. In the width direction ( Figure 2The positive electrode substrate 11 may be exposed at one end (in the X-axis direction). The positive electrode current collecting member 71 may be joined to the exposed portion of the positive electrode substrate 11.

[0060] The positive electrode active material layer 12 can have a thickness of, for example, 10 to 200 μm. The positive electrode active material layer 12 contains positive electrode active material particles. That is, the positive electrode 10 contains positive electrode active material particles. The positive electrode active material particles may contain optional components. For example, the positive electrode active material particles may contain at least one selected from LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. Here, for example, "(NiCoMn)" in a composition formula such as "Li(NiCoMn)O2" indicates that the sum of the composition ratios within the parentheses is 1. In addition to the positive electrode active material particles, the positive electrode active material layer 12 may further contain a conductive material and a binder. The conductive material may contain optional components. For example, the conductive material may include acetylene black. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material particles. The binder may contain an optional component. For example, the binder may include polyvinylidene fluoride (PVdF). The amount of the binder to be added may be, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the positive electrode active material particles.

[0061] The positive electrode active material particles can have a D50 of, for example, 1 to 30 μm. "D50" as used herein refers to the particle size at which the cumulative volume of particles from the smallest particle size side in a volume-based particle size distribution accounts for 50% of the total particle volume. The volume-based particle size distribution can be measured using a laser diffraction particle size distribution analyzer.

[0062] The positive electrode active material particles may have a particle size of 0.1 to 10 μm. 2 The BET specific surface area is 2.547 Å / g. "BET specific surface area" in this specification refers to the specific surface area calculated using the BET multi-point method from an adsorption isotherm measured using a gas adsorption method. The adsorption medium gas is nitrogen. The BET specific surface area is measured three or more times for each measurement object. The arithmetic average of these three or more results is considered the BET specific surface area of ​​the measurement object.

[0063] [negative electrode]

[0064] The negative electrode 20 may include, for example, a negative electrode substrate 21 and a negative electrode active material layer 22. The negative electrode substrate 21 is a conductive sheet. The negative electrode substrate 21 may be, for example, a Cu (copper) alloy foil or the like. The negative electrode substrate 21 may have a thickness of, for example, 5 to 30 μm. The negative electrode active material layer 22 may be arranged on the surface of the negative electrode substrate 21. The negative electrode active material layer 22 may, for example, be arranged only on one side of the negative electrode substrate 21. The negative electrode active material layer 22 may also be arranged on both the front and back sides of the negative electrode substrate 21. In the width direction ( Figure 2 The negative electrode substrate 21 may be exposed at one end (in the X-axis direction). The negative electrode current collecting member 72 may be joined to the exposed portion of the negative electrode substrate 21.

[0065] The negative electrode active material layer 22 may have a thickness of, for example, 10 to 200 μm. The negative electrode active material layer 22 contains negative electrode active material particles. That is, the negative electrode 20 contains negative electrode active material particles. The negative electrode active material particles may contain optional components. The negative electrode active material particles may be, for example, powders. The negative electrode active material particles may have a D50 of, for example, 1 to 30 μm. "D50" in this specification indicates the particle size at which the cumulative particle volume from the small particle size side in the volume-based particle size distribution becomes 50% of the total particle volume. D50 can be measured using a laser diffraction particle size distribution measuring device. The negative electrode active material particles may have a D50 of, for example, 0.1 to 10 μm. 2 / g of BET specific surface area.

[0066] The negative electrode active material layer 22 may contain, for example, 80 to 99% by mass of negative electrode active material particles. The negative electrode active material layer 22 may contain, for example, 95 to 98% by mass of negative electrode active material particles.

[0067] The negative electrode active material particles may contain, for example, an alloy-based negative electrode active material. The negative electrode active material may be basically composed of, for example, an alloy-based negative electrode active material. The alloy-based negative electrode active material may have a large specific capacity. By using an alloy-based negative electrode active material, an improvement in energy density can be expected. However, alloy-based negative electrode active materials tend to have a large volume change (expansion and contraction rate) accompanying charge and discharge. Therefore, in the case where a protective film is formed on the surface of a negative electrode containing an alloy-based negative electrode active material, the protective film is sometimes destroyed due to the volume change accompanying charge and discharge, and the degradation of the negative electrode cannot be suppressed. However, according to the battery disclosed in the present invention, even if the negative electrode contains such an alloy-based negative electrode active material with a large volume change (expansion and contraction rate) accompanying charge and discharge, the degradation of the negative electrode can be fully suppressed by containing the above-mentioned electrolyte.

[0068] [Alloy-based negative electrode active material]

[0069] Alloy-based negative electrode active materials can absorb lithium through an alloying reaction and release it through a dealloying reaction. For example, alloy-based negative electrode active materials can contain at least one selected from Si (silicon), Sn (tin), Al (aluminum), Cd (cadmium), Sb (antimony), and Pb (lead). Si is one promising material. Various Si-containing materials can function as negative electrode active materials. In other words, the negative electrode active material can contain a Si-containing material.

[0070] In this specification, "Si-containing material" means a material containing Si. As long as the Si-containing material contains Si, it may further contain additional components. The Si-containing material may, for example, be basically composed of Si metal (Si simple substance). The Si-containing material may, for example, contain a Si-based alloy. The Si-containing material may, for example, contain at least one selected from SiCu alloy, SiNi alloy, SiAl alloy and SiZn alloy. The Si-containing material may, for example, also contain a Si compound. The Si-containing material may, for example, contain Si oxide. The Si-containing material may, for example, contain SiOx (0.5≦x≦1.5). The Si-containing material may, for example, also contain a composite material of Si and other materials. The Si-containing material may, for example, contain a Si / C composite material. The Si / C composite material can, for example, be formed by supporting Si metal, Si oxide, etc. on a carbon material (graphite, amorphous carbon, etc.). The Si-containing material may, for example, contain at least one selected from Si metal, Si-based alloy, Si oxide and Si / C composite material.

[0071] [Carbon-based negative electrode active material]

[0072] The negative electrode active material particles may, for example, contain a carbon-based negative electrode active material. The negative electrode active material particles may, for example, essentially consist of a carbon-based negative electrode active material. The carbon-based negative electrode active material may, for example, contain at least one selected from graphite, soft carbon (easily graphitizable carbon), and hard carbon (hardly graphitizable carbon).

[0073] The negative electrode active material particles may contain, for example, both an alloy-based negative electrode active material and a carbon-based negative electrode active material. Carbon-based negative electrode active materials tend to have, for example, superior cycle characteristics compared to alloy-based negative electrode active materials. By containing both alloy-based negative electrode active materials and carbon-based negative electrode active materials in the negative electrode active material particles, it is expected that both energy density and cycle characteristics can be achieved. The mass ratio of the alloy-based negative electrode active material to the carbon-based negative electrode active material may be, for example, "alloy-based negative electrode active material / carbon-based negative electrode active material = 1 / 99 to 99 / 1", "alloy-based negative electrode active material / carbon-based negative electrode active material = 1 / 99 to 30 / 70", or "alloy-based negative electrode active material / carbon-based negative electrode active material = 1 / 99 to 10 / 90".

[0074] The negative electrode active material particles may comprise at least one selected from graphite, soft carbon, hard carbon, SiO, and metallic Si. For example, the negative electrode active material particles may consist essentially of spherical graphite particles. The spherical graphite particles may be coated with, for example, a pitch-based carbon material.

[0075] The negative electrode active material layer 22 may further contain a conductive material and a binder in addition to the negative electrode active material particles. The conductive material may contain optional components. For example, the conductive material may contain carbon nanotubes, carbon black, etc.

[0076] The amount of the conductive material to be incorporated can be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the negative electrode active material particles. The binder can include optional components. For example, the binder can include at least one selected from carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR). The amount of the binder to be incorporated can be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the negative electrode active material particles.

[0077] The surface of the negative electrode active material particle preferably has at least one structure selected from the group consisting of a structure represented by -R1-Si-OH (R1 includes Si or O), a -R2-Si(-O-)3 structure (R2 represents a saturated hydrocarbon group having 2 to 6 carbon atoms), and a structure represented by the following formula (2):

[0078] [Chemistry 4]

[0079]

[0080] [Wherein, a=1~4, b=3~7, c=2~6, d=4~12].

[0081] [Separator]

[0082] At least a portion of the separator 30 is interposed between the positive electrode 10 and the negative electrode 20. The separator 30 separates the positive electrode 10 from the negative electrode 20. The separator 30 may have a thickness of, for example, 10 μm to 30 μm.

[0083] Separator 30 is porous. The electrolyte solution permeates through separator 30. Separator 30 can have an air permeability of, for example, 200 s / 100 mL to 400 s / 100 mL. "Air permeability" in this specification refers to "air resistance" as defined in JIS P8117:2009. Air permeability can be measured using the Gurley test.

[0084] The separator 30 is electrically insulating. For example, the separator 30 may comprise a polyolefin resin. For example, the separator 30 may consist essentially of a polyolefin resin. For example, the polyolefin resin may comprise at least one selected from polyethylene (PE) and polypropylene (PP). For example, the separator 30 may have a single-layer structure. For example, the separator 30 may consist essentially of a PE layer. For example, the separator 30 may have a multi-layer structure. For example, the separator 30 may be formed by sequentially stacking a PP layer, a PE layer, and a PP layer. For example, a heat-resistant layer may be formed on the surface of the separator 30.

[0085] [Example]

[0086] The following describes examples of the present disclosure (hereinafter also referred to as "the present examples"). However, the following description does not limit the scope of the present disclosure. Unless otherwise specified, "%" and "parts" in the examples are by mass % and mass parts.

[0087] <Manufacturing of Non-aqueous Electrolyte Secondary Battery>

[0088] Evaluation batteries No. 1 to No. 25 (non-aqueous electrolyte secondary batteries) were produced as follows.

[0089] (Preparation of positive electrode)

[0090] Prepare the following materials.

[0091] Positive active material: Li(NiCoMn)O2

[0092] Conductive material: Acetylene black

[0093] Adhesive: PVdF

[0094] Dispersion medium: N-methyl-2-pyrrolidone

[0095] Positive electrode substrate: Al foil

[0096] Prepare a positive electrode composite slurry by mixing the positive electrode active material, conductive material, binder, and dispersion medium. The solids mass ratio is 87 / 10 / 3. Apply the slurry to the surface of the positive electrode substrate to form a positive electrode composite layer. Compress the positive electrode composite layer. Prepare the positive electrode in this manner.

[0097] (Preparation of negative electrode)

[0098] Prepare the following materials.

[0099] Alloy negative electrode active material: SiOx (D50 = 15 μm, x = 0 to 2)

[0100] Carbon-based negative electrode active material: graphite (D50 = 20 μm)

[0101] Adhesive: CMC, SBR

[0102] Dispersion medium: water

[0103] Anode substrate: Cu foil

[0104] First additive: as shown in Table 1.

[0105] Second additive: as shown in Table 1.

[0106] The alloy-based negative electrode active material and the carbon-based negative electrode active material are mixed at a predetermined mass ratio to prepare a negative electrode active material (mixed powder).

[0107] A negative electrode slurry is prepared by mixing the negative electrode active material, binder, dispersion medium, and, if added, first and second additives. The negative electrode slurry is applied to the surface of the negative electrode substrate and dried to form a negative electrode active material layer. The negative electrode active material layer is compressed to produce a negative electrode raw sheet. The negative electrode raw sheet is cut into a specified size to prepare the negative electrode.

[0108] (Electrolyte)

[0109] Prepare an electrolyte. The electrolyte contains the following components. The types, amounts, and mass fractions of the first and second additives in the electrolyte are shown in Table 1. The amounts represent the electrolyte composition before injection into the battery, and the mass fractions represent the content after activation.

[0110] Solvent: "FEC / EMC=3 / 7 (volume ratio)"

[0111] Supporting electrolyte: LiPF6 (molar concentration = 1.0 mol / L)

[0112] First additive: as shown in Table 1.

[0113] Second additive: as shown in Table 1.

[0114] Silane compounds 1A to 1D shown in Table 1 have the structure represented by the above formula (1-1), where a, b, c, and d are the following numbers.

[0115] Silane compound 1A: (a, b, c, d) = (1, 3, 2, 4)

[0116] Silane compound 1B: (a, b, c, d) = (1, 3, 6, 12)

[0117] Silane compound 1C: (a, b, c, d) = (2, 5, 2, 4)

[0118] Silane compound 1D: (a, b, c, d) = (2, 5, 6, 12)

[0119] Silane compounds 2A to 2D shown in Table 1 have the structure represented by the above formula (1-2), where a, b, c, and d are the following numbers.

[0120] Silane compound 2A: (a, b, c, d) = (1, 3, 2, 4)

[0121] Silane compound 2B: (a, b, c, d) = (1, 3, 6, 12)

[0122] Silane compound 2C: (a, b, c, d) = (2, 5, 2, 4)

[0123] Silane compound 2D: (a, b, c, d) = (2, 5, 6, 12)

[0124] Additives 1 to 4 shown in Table 1 are the following compounds and mixtures of compounds.

[0125] Additive 1: Trimethoxysilylpropylaniline

[0126] Additive 2: Trialkoxyvinylsilane

[0127] Additive 3: Triethylsilanol [also known as hydroxytriethylsilane or triethyl(hydroxy)silane]

[0128] Additive 4: Ethylenedioxybis(trimethylsilane) [also known as 1,2-bis(trimethylsilyloxy)ethane or ethylene glycol bis(trimethylsilyl ether)]

[0129] The solvent, the supporting electrolyte, and, if added, the first additive and the second additive are mixed at a predetermined mass ratio to prepare an electrolyte solution.

[0130] (Assembly)

[0131] Prepare a separator. The separator has a three-layer structure consisting of a PP layer, a PE layer, and a PP layer. The separator has an air permeability of 200 s / 100 mL.

[0132] The positive electrode, separator, and negative electrode are stacked so that they face each other with the separator interposed between them. This forms an electrode assembly. An outer packaging is prepared. The outer packaging is a bag made of aluminum laminate film. The electrode assembly is housed within the outer packaging. The electrolyte is injected into the outer packaging. The outer packaging is sealed. A battery for evaluation is assembled in the above manner.

[0133] (Activation treatment)

[0134] In a thermostatic chamber set at 25°C, the evaluation battery was charged to 4.2V by a constant current method of 0.3C. Then, the evaluation battery was discharged to 3V by a constant current method of 0.3C. This charge and discharge cycle (one turn) was repeated 3 times. It should be noted that "C" is the symbol for the time rate of current. A current of 1C is defined as discharging the design capacity of the evaluation battery in 1 hour.

[0135] (Determination of initial capacity)

[0136] After activation, the evaluation cell was fully charged using a constant current / constant voltage method. The current during constant current charging was 0.3C. The voltage during constant voltage charging was 4.2V. Constant voltage charging was terminated when the current decayed to 0.05C. Next, the evaluation cell was discharged to 3.0V using a constant current method at 0.3C, and the initial capacity (discharge capacity) was measured.

[0137] <Evaluation>

[0138] (Initial DC resistance)

[0139] The voltage of the evaluation cell was adjusted to 3.7 V. Discharged for 30 seconds at a current of 0.5 C in a thermostatic chamber set at 25°C. The voltage drop from the start of discharge to 10 seconds was measured. The DC resistance was calculated based on the voltage drop and the discharge current.

[0140] (Capacity retention rate after degradation and resistance increase rate after degradation)

[0141] In a thermostatic chamber set at 25°C, charge and discharge cycles were repeated 1000 times. One cycle represents one cycle of the following "charge → first pause → discharge → second pause". The discharge capacity of the 1st cycle and the 1000th cycle was measured under the same conditions as the initial capacity. In addition, the DC resistance of the 1st cycle and the 1000th cycle was measured in the same manner as the measurement of the initial DC resistance. The discharge capacity of the 1000th cycle was divided by the discharge capacity of the 1st cycle to calculate the capacity retention rate after degradation. The DC resistance of the 1000th cycle was divided by the DC resistance of the 1st cycle to calculate the resistance increase rate after degradation. The results are shown in Table 1.

[0142] Charging: Constant current mode, current = 0.3It, end voltage = 4.2V

[0143] First pause: 10 minutes

[0144] Discharge: Constant current mode, current = 0.3It, end voltage = 3.0V

[0145] Second timeout: 10 minutes

[0146] [Table 1]

[0147]

[0148] As shown in Table 1, the evaluation batteries No. 1 to 8 had high capacity retention rates and small resistance increase rates after deterioration.

[0149] <Note>

[0150] This specification also discloses a “method for producing a non-aqueous electrolyte secondary battery”.

[0151] The method for producing a nonaqueous electrolyte secondary battery disclosed herein includes the following (a) to (c).

[0152] (a) A silane compound, a solvent, and a supporting electrolyte are mixed to prepare an electrolyte solution.

[0153] (b) An electrode assembly including a negative electrode and a positive electrode is formed.

[0154] (c) The electrode body is impregnated with the electrolyte solution to produce a battery.

[0155] The silane compound has two or more trialkoxysilyl groups.

[0156] This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The scope of this disclosure includes all variations within the meaning and scope equivalent to the description of the claims. For example, it is foreseeable that any configuration can be extracted from this embodiment and this example and combined arbitrarily. In the event that multiple effects are described in this embodiment and this example, the scope of this disclosure is not limited to the scope of all effects.

[0157] While the embodiments of the present invention have been described, the embodiments disclosed herein are to be construed in all respects as illustrative and non-restrictive. The scope of the present invention is indicated by the claims, and is intended to encompass all modifications within the meaning and scope of the claims and equivalents thereof.

Claims

1. An electrolyte solution for a non-aqueous electrolyte secondary battery, comprising a silane compound having two or more trialkoxysilyl groups, wherein the silane compound comprises: A compound represented by the following formula (1-1): [Chemistry 2] Where a=1~4, b=3~7, c=2~6, d=4~12; and A compound represented by the following formula (1-2): [Chemistry 3] In the formula, a=1~4, b=3~7, c=2~6, d=4~12, The concentration of the compound represented by formula (1-1) in the electrolyte is 1×10 4 ~1×10 5 ppm, the concentration of the compound represented by formula (1-2) in the electrolyte is 10 to 1×10 2 ppm.

2. The electrolyte solution for non-aqueous electrolyte secondary batteries according to claim 1, wherein The trialkoxysilyl group is one selected from the group consisting of a trimethoxysilyl group, a triethoxysilyl group, and a tripropoxysilyl group.

3. The electrolyte solution for non-aqueous electrolyte secondary batteries according to claim 1, wherein The silane compound further has a saturated hydrocarbon group having 2 to 6 carbon atoms. 4 . A non-aqueous electrolyte secondary battery comprising the electrolytic solution for a non-aqueous electrolyte secondary battery according to claim 1 , a positive electrode, and a negative electrode.

5. The non-aqueous electrolyte secondary battery according to claim 4, wherein The negative electrode includes negative electrode active material particles containing an alloy-based negative electrode active material.

6. The nonaqueous electrolyte secondary battery according to claim 5, wherein The surface of the negative electrode active material particle has a structure containing Si or O.

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