Battery

Abstract

The invention provides a battery which comprises a negative plate and an electrolyte, and a negative active material in the negative plate comprises a silicon-based material; the electrolyte comprises a first additive and fluoroethylene carbonate, the first additive comprises a compound as shown in formula 1, R1, R2 and R3 are respectively and independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl and substituted or unsubstituted C6-C20 aryl, and R1, R2 and R3 are independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C1-C20 alkenyl and substituted or unsubstituted C6-C20 aryl. Substituent groups of R1, R2 and R3 comprise at least one of halogen, cyano groups and C1-C20 alkenyl groups. The battery provided by the invention takes a silicon-based material as a negative electrode, and shows excellent high-temperature storage performance and furnace temperature performance.

Description

Technical Field

[0001] The invention relates to a battery and belongs to the field of lithium ion batteries. Background Art

[0002] Lithium-ion batteries are widely used in laptops, mobile phones, digital products and other fields due to their high energy density, high safety performance, long cycle life and environmental friendliness. The theoretical specific capacity of silicon materials (4200mAh / g) is more than 10 times that of graphite materials, and is considered to be the most promising next-generation high-energy density lithium-ion battery material. However, during the process of lithium insertion and extraction, the silicon material is accompanied by volume expansion and contraction, which may cause structural ruptures in the negative electrode sheet. The volume change of the negative electrode sheet will affect the heat conduction path inside the battery, resulting in the degradation of the furnace temperature performance of the battery. In a high temperature environment, the structural damage of the negative electrode sheet causes the electrolyte to decompose more quickly, resulting in a decrease in the high-temperature storage performance of the lithium-ion battery.

[0003] Therefore, those skilled in the art are in urgent need of developing a negative electrode silicon-doped system battery with excellent high-temperature storage performance and furnace temperature performance. Summary of the invention

[0004] The present invention provides a battery, wherein the negative electrode of the battery comprises a silicon-based material and exhibits excellent high-temperature storage performance and furnace temperature performance.

[0005] The present invention provides a battery, wherein the battery comprises a negative electrode sheet and an electrolyte, and the negative electrode active material in the negative electrode sheet comprises a silicon-based material;

[0006] The electrolyte includes a first additive and fluoroethylene carbonate, wherein the first additive includes a compound shown in Formula 1:

[0007]

[0008] Wherein, R1, R2, and R3 are each independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C6-C20 aryl, and the substituents of R1, R2, and R3 include at least one of halogen, cyano, and C1-C20 alkenyl.

[0009] The battery as described above, wherein the first additive comprises at least one of the compounds represented by Formula 2 to Formula 7:

[0010]

[0011] The battery as described above, wherein 0.2≤(10*C) / (12A+B)≤21;

[0012] Among them, A is the mass percentage of the first additive in the electrolyte; B is the mass percentage of the fluoroethylene carbonate in the electrolyte; and C is the mass percentage of the silicon-based material in the negative electrode active material.

[0013] The battery as described above, wherein the electrolyte further comprises a second additive, and the second additive comprises a nitrile compound;

[0014] The nitrile compound includes at least one of succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, fluoroacetonitrile, valeronitrile and ethoxy pentafluorophosphazene.

[0015] The battery as described above, wherein 0.1%≤A≤10%;

[0016] Preferably, 0.5%≤A≤1.5%.

[0017] The battery as described above, wherein 5%≤B≤20%;

[0018] Preferably, 10%≤B≤15%.

[0019] The battery as described above, wherein 1%≤C≤80%;

[0020] Preferably, 5%≤C≤50%.

[0021] The battery as described above, wherein 0.1%≤D≤10%,

[0022] Wherein, D is the mass percentage of the nitrile compound in the electrolyte;

[0023] Preferably, 1%≤D≤5%.

[0024] The battery as described above, wherein the electrolyte further comprises a third additive, and the third additive comprises at least one of 1,3-propane sultone, 1,3-propylene sultone and vinylene carbonate.

[0025] The battery as described above, wherein the electrolyte further comprises a lithium salt, and the lithium salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium oxalate phosphate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide and lithium bistrifluoromethanesulfonyl imide; the mass percentage of the lithium salt in the electrolyte is 10-20%;

[0026] And / or, the electrolyte further comprises an organic solvent, wherein the organic solvent comprises at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate and γ-butyrolactone;

[0027] And / or, the silicon-based material includes silicon-carbon material and / or silicon-oxygen material;

[0028] And / or, the negative electrode active material further comprises a carbon-based material, wherein the carbon-based material comprises at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon;

[0029] And / or, the battery further comprises a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0030] The battery of the present invention uses a silicon-based material as a negative electrode, and the electrolyte includes a first additive and fluoroethylene carbonate. On the one hand, the SEI film generated by the first additive and fluoroethylene carbonate is rich in inorganic components Li3N and LiF, and these inorganic components make the SEI film stronger, which can inhibit the expansion of the negative electrode active material layer and avoid problems such as structural rupture of the negative electrode sheet, thereby improving the high-temperature storage performance and furnace temperature performance of the battery; on the other hand, the present invention controls the relationship ratio of the first additive, fluoroethylene carbonate and silicon-based material within the above range, which can avoid high-temperature gas production caused by excessive first additive and fluoroethylene carbonate, and can also avoid insufficient protection of the negative electrode active material layer caused by too little first additive and fluoroethylene carbonate, thereby improving the high-temperature storage performance and furnace temperature performance of the battery. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a battery, which includes a negative electrode sheet and an electrolyte, wherein the negative electrode active material in the negative electrode sheet includes a silicon-based material;

[0033] The electrolyte includes a first additive and fluoroethylene carbonate, wherein the first additive includes a compound shown in Formula 1:

[0034]

[0035] Wherein, R1, R2, and R3 are each independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C6-C20 aryl, and the substituents of R1, R2, and R3 include at least one of halogen, cyano, and C1-C20 alkenyl.

[0036] The battery of the present invention includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent and a binder, wherein the negative electrode current collector is generally a copper foil. The negative electrode active material of the present invention includes a silicon-based material, and the silicon-based material of the present invention refers to a material with silicon as the main component, for example, silicon carbide, silicon nitride, organic silicon compound, etc. The conductive agent and the binder in the negative electrode active layer of the present invention can be selected from conventional materials in the field.

[0037] The electrolyte of the present invention includes a first additive, which includes a compound shown in Formula 1, wherein R1, R2, and R3 are each independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, and substituted or unsubstituted C6-C20 aryl. The halogen of the present invention refers to -F, -Cl, -Br, -I, etc., the substituted or unsubstituted C1-C20 alkyl refers to a substituted or unsubstituted chain alkyl having 1 to 20 carbon atoms, or a substituted or unsubstituted cycloalkyl having 3 to 20 carbon atoms, the substituted or unsubstituted C1-C20 alkoxy refers to a substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, the substituted or unsubstituted C2-C20 alkenyl refers to a substituted or unsubstituted chain alkenyl having 2 to 20 carbon atoms, or a substituted or unsubstituted cycloalkenyl having 3 to 20 carbon atoms, and the substituted or unsubstituted C6-C20 aryl refers to a substituted or unsubstituted aryl having 6 to 20 carbon atoms. When the substituent is specified as a group having a specific carbon number, all geometric isomers having that carbon number are included. The substituents of R1, R2, and R3 include at least one of halogen, cyano, and C1-C20 alkenyl. For example, the substituents of R1, R2, and R3 may be independently selected from -F, -Cl, -Br, -I, -CH3, -CH2CH3, -OCH3, -OCH2CH3, -CH=CH2, -C6H5, -CH2F, -CH2CN, -CH2CH=CH2, -OCH2CN, etc.

[0038] According to the solution provided by the present invention, an electrolyte including a first additive and fluoroethylene carbonate and a negative electrode sheet including a silicon-based material are applied to a battery, and the battery exhibits excellent high-temperature storage performance and furnace temperature performance. The inventor analyzed this principle and believed that the reason may be that the first additive and fluoroethylene carbonate work synergistically to generate a dense and stable SEI film, which is rich in substances such as LiF and Li3N, improves the mechanical strength of the SEI film, can inhibit the expansion of the negative electrode active material layer including silicon-based materials, and avoids problems such as structural rupture of the negative electrode active material layer, thereby avoiding the destruction of the heat conduction path inside the negative electrode sheet, and improving the high-temperature storage performance and furnace temperature performance of the battery;

[0039] The first additive can also coordinate with lithium ions in the electrolyte, change its solvation structure, and improve lithium ion mobility. In addition, the N atoms of the first additive participate in the construction of the SEI film, which can inhibit the increase in battery impedance caused by excessive substances such as LiF, thereby improving the battery's room temperature cycle performance and low temperature performance.

[0040] In a specific embodiment, the first additive includes at least one of the compounds shown in Formula 2 to Formula 6:

[0041]

[0042] When the first additive selects the above-mentioned compound, the first additive can further synergize with fluoroethylene carbonate, and the generated SEI film is more dense and stable, which can better protect the negative electrode active material layer, and the impedance of the SEI film formed by the above-mentioned compounds is lower, which can make the impedance of the battery lower, thereby further improving the high temperature storage performance and furnace temperature performance of the battery.

[0043] In a specific embodiment, 0.2≤(10*C) / (12A+B)≤21; wherein A is the mass percentage of the first additive in the electrolyte; B is the mass percentage of fluoroethylene carbonate in the electrolyte; and C is the mass percentage of the silicon-based material in the negative electrode active material.

[0044] The present invention controls the relationship ratio of the first additive, fluoroethylene carbonate and silicon-based material within the above range, which can avoid high-temperature gas production caused by excessive first additive and fluoroethylene carbonate, and can also avoid insufficient protection of the negative electrode active material layer caused by too little first additive and fluoroethylene carbonate, thereby further improving the high temperature storage performance and furnace temperature performance of the battery.

[0045] In a specific embodiment, the electrolyte further includes a second additive, and the second additive includes a nitrile compound.

[0046] The second additive of the present invention includes nitrile compounds, which refer to compounds containing cyano groups. The present invention does not limit the selection of other groups in the nitrile compounds, as long as the cyano group is included, and also does not limit the combination of the cyano group and other groups.

[0047] The second additive of the present invention can act synergistically with the first additive, that is, the N atoms in the first additive and the second additive are combined with the transition metal in the positive electrode active material, so that the formed CEI film is stable and dense, and the dissolution of the transition metal in the positive electrode active material can be reduced, and the damage to the negative electrode active material layer caused by the migration of the transition metal to the negative electrode deposition is reduced, thereby improving the cycle performance and high-temperature storage performance of the battery.

[0048] In a specific embodiment, the nitrile compound includes at least one of succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, fluoroacetonitrile, valeronitrile, and ethoxypentafluorophosphazene.

[0049] In a specific embodiment, 0.1%≤A≤10%, for example, A is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc. Preferably, 0.5%≤A≤1.5%.

[0050] When the nitrile compound is selected from the above compounds and meets the above range, the battery can exhibit better high-temperature storage performance and cycle performance.

[0051] In a specific embodiment, 5%≤B≤20%, for example, B is 5%, 10%, 15% or 20%. When the mass percentage of fluoroethylene carbonate is within the above range, fluoroethylene carbonate can better cooperate with the first additive, so that the battery can have better high temperature storage performance and furnace temperature performance. Preferably, 10%≤B≤15%.

[0052] In a specific embodiment, 1%≤C≤80%, for example, C is 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%. When the mass percentage of the silicon-based material is within the above range, the energy density of the battery can be improved without causing excessive expansion of the negative electrode active material layer. Preferably, 5%≤C≤50%.

[0053] In a specific embodiment, 0.1%≤D≤10%, D is the mass percentage of the nitrile compound in the electrolyte, for example, D is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc. When the mass percentage of the second additive is within the above range, the cycle performance and high temperature storage performance of the battery can be further optimized. Preferably, 1%≤D≤5%.

[0054] In a specific embodiment, the electrolyte further includes a third additive, and the third additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone and vinylene carbonate. Adding the third additive to the electrolyte is beneficial to improving the low temperature performance of the battery.

[0055] In a specific embodiment, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium oxalate phosphate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide and lithium bistrifluoromethanesulfonyl imide; the mass percentage of the lithium salt in the electrolyte is 10-20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc. When the lithium salt is selected from the above lithium-containing compounds, lithium ions can be quickly dissociated and transmitted in the electrolyte, thereby improving the cycle performance of the battery.

[0056] In a specific embodiment, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate and γ-butyrolactone. This is beneficial to improving the electrochemical performance of the lithium-ion battery.

[0057] The present invention does not limit the preparation method of the electrolyte. In a specific embodiment, it is sufficient to mix the lithium salt, the organic solvent, the first additive and the fluoroethylene carbonate in a prescribed ratio.

[0058] Furthermore, when the electrolyte further includes a second additive, the lithium salt, the organic solvent, the first additive, fluoroethylene carbonate and the second additive are mixed in a prescribed ratio.

[0059] In a specific embodiment, the silicon-based material includes silicon-carbon material and / or silicon-oxygen material. Further, the negative electrode active material also includes carbon-based material, and the carbon-based material includes at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon.

[0060] In a specific embodiment, the battery further comprises a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. When the above positive electrode active material is selected, the positive electrode active material can provide lithium ions for the battery and enable the lithium ions to be quickly transmitted in the battery, which is conducive to achieving the cycle performance of the battery.

[0061] In a specific embodiment, the negative electrode active material layer further includes a conductive agent and a binder, and the negative electrode active material layer includes: 80-99.8% of negative electrode active material, 0.1-10% of conductive agent, and 0.1-10% of binder. Preferably, the negative electrode active material layer includes: 90-99.6% of negative electrode active material, 0.2-5% of conductive agent, and 0.2-5% of binder.

[0062] In a specific embodiment, the positive electrode active material layer further includes a conductive agent and a binder, and the positive electrode active material layer includes: 80-99.8% of positive electrode active material, 0.1-10% of conductive agent, and 0.1-10% of binder. Preferably, the positive electrode active material layer includes: 90-99.6% of positive electrode active material, 0.2-5% of conductive agent, and 0.2-5% of binder.

[0063] The present invention does not limit the selection of the positive electrode current collector, and the positive electrode current collector is generally aluminum foil.

[0064] In a specific embodiment, the conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, and metal powder.

[0065] In a specific embodiment, the binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0066] In a specific embodiment, the battery further includes a separator, which is a separator known in the art that can be used in batteries and is stable to the electrolyte used, and can be specifically configured as required.

[0067] Hereinafter, the present invention will be further described in detail through specific examples.

[0068] Example 1

[0069] The battery provided in this embodiment is prepared by the following steps:

[0070] 1. Preparation of electrolyte: In a glove box filled with argon (H2O<0.1ppm, O2<0.1ppm), EC / PC / DEC / PP are mixed in a mass ratio of 10 / 20 / 40 / 30, and then fully dried lithium hexafluorophosphate (LiPF6) accounting for 14% of the total mass of the electrolyte is quickly added thereto, fluoroethylene carbonate (FEC), the compound of formula 6 and succinonitrile are added, the mass content A of the compound of formula 6 in the electrolyte is 0.5%, the mass percentage content B of fluoroethylene carbonate in the electrolyte is 15%, and the mass percentage content D of succinonitrile (SN) in the electrolyte is 5%, and the mixture is stirred evenly. After passing the moisture and free acid tests, an electrolyte is obtained;

[0071] 2. Preparation of negative electrode sheet: negative electrode active materials silicon carbon / artificial graphite (5% silicon carbon and 95% artificial graphite, C is 5%), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) are mixed in a mass ratio of 94.5:2.5:1.5:1:0.5, deionized water is added, and negative electrode active slurry is obtained under the action of a vacuum mixer; the negative electrode active slurry is evenly coated on both surfaces of the copper foil; the coated copper foil is dried at room temperature, then transferred to an oven at 80°C for drying for 10 hours, and then cold pressed and cut to obtain a negative electrode sheet;

[0072] 3. Preparation of positive electrode sheet: Mix the positive electrode active materials lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), SP (superP) and carbon nanotubes (CNT) in a mass ratio of 96:2:1.5:0.5, add N-methylpyrrolidone (NMP), and stir under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; evenly coat the positive electrode active slurry on aluminum foil, dry the coated aluminum foil, and then roll and cut it to obtain the required positive electrode sheet;

[0073] 4. Preparation of the battery: stack the positive electrode sheet, the negative electrode sheet and the separator in the order of the positive electrode sheet, the separator and the negative electrode sheet, and then wind them to obtain a battery core; place the battery core in an outer packaging aluminum foil, inject the electrolyte into the outer packaging, and obtain the battery through vacuum packaging, standing, forming, shaping, sorting and other processes. The charge and discharge range of the battery of the present invention is 3.0-4.5V.

[0074] Example 2

[0075] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 0.1%.

[0076] Example 3

[0077] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 1%.

[0078] Example 4

[0079] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1.5%.

[0080] Example 5

[0081] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 5%.

[0082] Example 6

[0083] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 10%.

[0084] Example 7

[0085] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 11%.

[0086] Example 8

[0087] The preparation method of the battery in this embodiment is substantially the same as that in Embodiment 1, except that A is 1% and B is 5%.

[0088] Example 9

[0089] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and B is 10%.

[0090] Example 10

[0091] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and B is 20%.

[0092] Embodiment 11

[0093] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and B is 21%.

[0094] Example 12

[0095] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 1%.

[0096] Example 13

[0097] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 8%.

[0098] Embodiment 14

[0099] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 10%.

[0100] Embodiment 15

[0101] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 20%.

[0102] Example 16

[0103] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and C is 30%.

[0104] Embodiment 17

[0105] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 50%.

[0106] Embodiment 18

[0107] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 1% and C is 55%.

[0108] Embodiment 19

[0109] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and C is 60%.

[0110] Embodiment 20

[0111] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and C is 70%.

[0112] Embodiment 21

[0113] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 1% and C is 80%.

[0114] Embodiment 22

[0115] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and D is 0.1%.

[0116] Embodiment 23

[0117] The preparation method of the battery in this embodiment is substantially the same as that in Embodiment 1, except that A is 1% and D is 1%.

[0118] Embodiment 24

[0119] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and D is 3%.

[0120] Embodiment 25

[0121] The preparation method of the battery in this embodiment is substantially the same as that in embodiment 1, except that A is 1% and D is 10%.

[0122] Embodiment 26

[0123] The preparation method of the battery of this embodiment is substantially the same as that of the embodiment 1, except that A is 1% and D is 11%.

[0124] Embodiment 27

[0125] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and the compound of formula 6 is replaced by the compound of formula 2.

[0126] Embodiment 28

[0127] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and the compound of formula 6 is replaced by the compound of formula 3.

[0128] Embodiment 29

[0129] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and the compound of formula 6 is replaced by the compound of formula 4.

[0130] Embodiment 30

[0131] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1% and the compound of formula 6 is replaced by the compound of formula 5.

[0132] Embodiment 31

[0133] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1%, the compound of formula 6 is replaced by the compound of formula 3, and succinonitrile is replaced by adiponitrile (ADN).

[0134] Embodiment 32

[0135] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1%, the compound of formula 6 is replaced by the compound of formula 3, and succinonitrile is replaced by 1,3,6-hexanetrinitrile (HTCN).

[0136] Embodiment 33

[0137] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1%, the compound of formula 6 is replaced by the compound of formula 3, and succinonitrile is replaced by fluoroacetonitrile.

[0138] Embodiment 34

[0139] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1%, the compound of formula 6 is replaced by the compound of formula 3, and succinonitrile is replaced by valeronitrile.

[0140] Embodiment 35

[0141] The preparation method of the battery of this embodiment is substantially the same as that of embodiment 1, except that A is 1%, the compound of formula 6 is replaced by the compound of formula 3, and succinonitrile is replaced by ethoxypentafluorophosphazene.

[0142] Comparative Example 1

[0143] The preparation method of the battery of this comparative example is substantially the same as that of Example 1, except that the compound of formula 6 is not added to the electrolyte.

[0144] Comparative Example 2

[0145] The preparation method of the battery of this comparative example is substantially the same as that of Example 1, except that fluoroethylene carbonate is not added to the electrolyte, A is 1%, and the compound of formula 6 is replaced by the compound of formula 3.

[0146] Comparative Example 3

[0147] The preparation method of the battery of this comparative example is substantially the same as that of Example 1, except that fluoroethylene carbonate is not added to the electrolyte and A is 1%.

[0148] Comparative Example 4

[0149] The preparation method of the battery of this comparative example is substantially the same as that of Example 1, except that A is 5%, B is 20%, and C is 1%.

[0150] Table 1

[0151]

[0152]

[0153] Test example

[0154] The batteries prepared in the examples and comparative examples were subjected to room temperature cycle performance test, high temperature storage performance test, furnace temperature performance test and low temperature performance test respectively:

[0155] 1. Room temperature cycle performance test: The battery is charged and discharged at a rate of 1C at 25°C. When the cycle capacity retention rate drops to 80%, the number of cycles is recorded. The results are shown in Table 2.

[0156] 2. High temperature storage performance test: Charge the battery at 25°C at a rate of 1C to the cut-off voltage, cut-off current 0.025C, and let it stand for 5 minutes to test the thickness of the lithium-ion battery (this is the thickness before storage). The fully charged battery is placed in an open circuit at (60±2)°C for 35 days. After 35 days of storage, it is placed in an open circuit at room temperature for 2 hours. The thickness after storage is measured and the thickness expansion rate of the battery is calculated. The results are shown in Table 2.

[0157] 3. Oven temperature performance test: 10 fully charged batteries were placed at 130°C for 1 hour, and the number of batteries that did not catch fire or explode was observed. The results were recorded as shown in Table 2.

[0158] 4. Low temperature performance test: The battery was charged and discharged at room temperature for 5 times at a rate of 1C, then charged to 4.5V at a rate of 1C, and the 1C capacity Q0 was recorded. The fully charged battery was placed at -20°C for 4h, and then discharged to 3V at a rate of 0.2C, and the discharge capacity Q1 was recorded. The low temperature discharge capacity retention rate was calculated, and the low temperature discharge capacity retention rate (%) = Q1 / Q0 × 100%. The results are shown in Table 2.

[0159] Table 2

[0160]

[0161]

[0162] It can be seen from Table 2 that according to the comparison between Examples 1-35 and Comparative Examples 1-4, when the electrolyte includes the first additive and fluoroethylene carbonate and (10*C) / (12A+B) is in the range of 0.2-21, the room temperature and high temperature cycle performance, furnace temperature performance and low temperature performance of the battery are better.

[0163] According to the comparison of Examples 1-7, it can be seen that when the mass percentage of the first additive is in the range of 0.1-10%, the first additive is sufficient to generate a dense and stable SEI film with fluoroethylene carbonate, inhibiting the expansion of the silicon-based material in the negative electrode active material layer, thereby effectively improving the high temperature storage performance and safety performance of the battery.

[0164] According to the comparison of Examples 1 and 8-11, it can be seen that when the mass percentage of fluoroethylene carbonate is in the range of 5-20%, the SEI film generated by the fluoroethylene carbonate and the first additive is more dense and stable, can better protect the negative electrode active material layer, and the battery has low impedance, thereby improving the battery's room temperature cycle performance, high temperature storage performance, furnace temperature performance and low temperature performance.

[0165] According to the comparison of Examples 1 and 12-21, it can be seen that when the mass percentage of the silicon-based material is in the range of 1%-80%, the expansion of the negative electrode active material layer can be suppressed, so that the room temperature cycle performance, high temperature storage performance and furnace temperature performance of the battery are better; when the mass percentage of the silicon-based material is in the range of 5%-50%, the expansion of the negative electrode active material layer can be effectively suppressed, so that the room temperature cycle performance, high temperature storage performance and furnace temperature performance of the battery are better.

[0166] According to the comparison of Examples 1 and 22-26, when the mass percentage of the second additive is in the range of 0.1-10%, the second additive can match the first additive to generate a CEI film with higher stability, which can make the battery's room temperature cycle performance, high temperature storage performance, furnace temperature performance and low temperature performance better.

[0167] According to the comparison of Examples 1 and 27-35, when the first additive is selected from compounds of Formula 2-Formula 6 or the second additive is selected from succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, fluoroacetonitrile, valeronitrile, and ethoxypentafluorophosphazene, the battery can have excellent room temperature cycle performance, high temperature storage performance, furnace temperature performance, and low temperature performance.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery, characterized in that: The battery comprises a negative electrode sheet and an electrolyte, wherein the negative electrode active material in the negative electrode sheet comprises a silicon-based material; The electrolyte includes a first additive and fluoroethylene carbonate, wherein the first additive includes a compound shown in Formula 1: Wherein, R1, R2, and R3 are each independently selected from halogen, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C6-C20 aryl, and the substituents of R1, R2, and R3 include at least one of halogen, cyano, and C1-C20 alkenyl.

2. The battery according to claim 1, characterized in that The first additive includes at least one of the compounds shown in Formula 2 to Formula 7:

3. The battery according to claim 1 or 2, characterized in that: 0.2≤(10*C) / (12A+B)≤21; Among them, A is the mass percentage of the first additive in the electrolyte; B is the mass percentage of the fluoroethylene carbonate in the electrolyte; and C is the mass percentage of the silicon-based material in the negative electrode active material.

4. The battery according to claim 3, characterized in that The electrolyte further includes a second additive, wherein the second additive includes a nitrile compound; The nitrile compound includes at least one of succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, fluoroacetonitrile, valeronitrile and ethoxy pentafluorophosphazene.

5. The battery according to any one of claims 1 to 4, characterized in that: 0.1％≤A≤10％； Preferably, 0.5%≤A≤1.5%.

6. The battery according to any one of claims 1 to 5, characterized in that: 5％≤B≤20％； Preferably, 10%≤B≤15%.

7. The battery according to any one of claims 1 to 6, characterized in that: 1％≤C≤80％； Preferably, 5%≤C≤50%.

8. The battery according to any one of claims 1 to 7, characterized in that: 0.1％≤D≤10％， Wherein, D is the mass percentage of the nitrile compound in the electrolyte; Preferably, 1%≤D≤5%.

9. The battery according to any one of claims 1 to 8, characterized in that: The electrolyte further includes a third additive including at least one of 1,3-propane sultone, 1,3-propylene sultone, and vinylene carbonate.

10. The battery according to any one of claims 1 to 9, characterized in that: The electrolyte further includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium oxalate phosphate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide and lithium bistrifluoromethanesulfonyl imide; the mass percentage of the lithium salt in the electrolyte is 10-20%; And / or, the electrolyte further comprises an organic solvent, wherein the organic solvent comprises at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate and γ-butyrolactone; And / or, the silicon-based material includes silicon-carbon material and / or silicon-oxygen material; And / or, the negative electrode active material further comprises a carbon-based material, wherein the carbon-based material comprises at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon; And / or, the battery further comprises a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

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