A battery

Abstract

The application provides a battery, which comprises a positive electrode sheet, a negative electrode sheet, a diaphragm and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent and a first additive and a second additive, the first additive is selected from at least one of cyclic silane compounds containing unsaturated bonds, and the second additive is selected from at least one of fluorinated cyclic carbonate compounds; through the synergistic effect between the mass of the unit area single-side negative electrode active material layer in the negative electrode sheet, the specific surface area of the negative electrode active material and the electrolyte additive, the high-temperature cycle performance and the high-temperature storage performance of the prepared battery can be effectively improved, and the thermal shock safety performance of the battery is further improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a battery, particularly a battery with good high-temperature cycle performance, good high-temperature storage performance and high safety performance. Background Technology

[0002] Lithium-ion batteries are widely used in various electronic products due to their high energy density and long cycle life. In recent years, they have also been extensively used in electric vehicles, power tools, and energy storage devices. As the application scope of lithium-ion batteries expands, their size is also increasing, making battery safety performance particularly important. Furthermore, with the improvement of people's living standards and their aspirations for a better life, higher demands are being placed on battery energy density.

[0003] To improve the energy density of lithium-ion batteries, increasing the voltage of the cathode material is a common approach. However, as the limiting voltage of cathode materials continues to rise, their specific capacity gradually increases, leading to severe deterioration in high-temperature performance and making it impossible to guarantee long cycle life. Especially under high voltage, during long-term charge-discharge cycles, the cathode material expands in volume, causing severe cracks. Electrolyte enters the cathode material, damaging its structure, and the release of reactive oxygen species further accelerates the oxidative decomposition of the electrolyte. Furthermore, while the ultra-high specific capacity of silicon anode materials can also improve battery energy density, the surface particles of silicon anode materials are prone to fracture and have a large volume expansion rate, easily leading to numerous side reactions of the electrolyte on the surface, ultimately causing severe capacity decay.

[0004] Currently, oxide coatings are typically used to modify the surface of cathode materials, or cathode materials with different morphologies and structures are prepared. However, these processes are complex, costly, and offer poor protection. Therefore, it is crucial to invent a battery with better safety and higher cycle stability. Summary of the Invention

[0005] To address the problem of stress damage to electrode material surfaces caused by the volume expansion of both positive and negative electrode materials in existing high-voltage batteries, leading to rupture of the solid electrolyte membrane and the generation of active oxygen that oxidizes the electrolyte, this invention provides a battery. The battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte additives include cyclic silane compounds containing unsaturated bonds and fluorinated cyclic carbonate compounds. Through the synergistic effect of the mass of the single-sided negative electrode active material layer per unit area in the negative electrode, the specific surface area of ​​the negative electrode active material, and the electrolyte additives, the high-temperature cycle performance and high-temperature storage performance of the prepared battery can be effectively improved, and the thermal shock safety performance of the battery can be further enhanced.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent, a first additive, and a second additive, wherein the first additive is selected from cyclic silane compounds containing unsaturated bonds, and the second additive is selected from at least one of fluorinated cyclic carbonate compounds.

[0008] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0009] The battery satisfies the following relationship:

[0010] 115≤(a+1 / 5b) / (t×p)≤700

[0011] Where a represents the percentage of the first additive by mass in the total mass of the electrolyte, b represents the percentage of the second additive by mass in the total mass of the electrolyte, and t represents the mass of the single-sided negative electrode active material layer per unit area, in g / cm³. 2 p represents the specific surface area of ​​the negative electrode active material, in m². 2 / g.

[0012] According to an embodiment of the present invention, when the battery satisfies 115≤(a+1 / 5b) / (t×p)≤700, the additive per unit mass can effectively protect the surface of the negative electrode material per unit specific surface area, fully suppressing the volume expansion of the negative electrode material, and also significantly improving the battery's high-temperature cycle performance, high-temperature storage performance, and safety performance. When the battery does not satisfy 115≤(a+1 / 5b) / (t×p)≤700, the additive per unit mass is insufficient to form sufficient protection for the negative electrode material per unit specific surface area, or the formed protective layer is too thick. Both of these will result in insignificant improvements in the battery's high-temperature cycle performance, high-temperature storage performance, and safety performance.

[0013] According to an embodiment of the present invention, 130≤(a+1 / 5b) / (t×p)≤200.

[0014] According to an embodiment of the present invention, (a+1 / 5b) / (t×p) is 115, 120, 130, 140, 150, 160, 170, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, 520, 550, 580, 600, 620, 650, 680 or 700.

[0015] According to an embodiment of the present invention, 0.05% ≤ a ≤ 5%, that is, the percentage content a of the first additive by mass of the total electrolyte is 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3.0%, 3.4%, 3.5%, 4%, 4.5%, 4.8%, or 5%.

[0016] According to an embodiment of the present invention, 5% ≤ b ≤ 15%, that is, the percentage content b of the second additive in the total mass of the electrolyte is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0017] According to an embodiment of the present invention, 0.0045 ≤ t ≤ 0.028, that is, the mass t of the single-sided negative electrode active material layer per unit area is 0.005 g / cm³. 2 0.006g / cm 2 0.008g / cm 2 0.009g / cm 2 0.01g / cm 2 0.11 g / cm 2 0.012g / cm 2 0.013g / cm 2 0.014 g / cm 2 0.15g / cm 2 0.017g / cm 2 0.018g / cm 2 Or 0.02g / cm 2 .

[0018] According to an embodiment of the present invention, 0.55 ≤ p ≤ 2.35, the specific surface area p of the negative electrode active material is 0.6 m². 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g or 2m 2 / g.

[0019] According to an embodiment of the present invention, the cyclic silane compound containing unsaturated bonds is a six-membered cyclic silane compound containing carbon-carbon double bonds.

[0020] According to an embodiment of the present invention, the cyclic silane compound containing unsaturated bonds has the structural formula shown in Formula I:

[0021]

[0022] In Formula I, R1, R2, and R3 may be the same or different and are independently selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted olefin, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; if substituted, the substituent is halogen or alkyl; X is selected from -CH2-, -O-, -S-, NH, PH, and BH.

[0023] According to embodiments of the present invention, R1, R2, and R3 may be the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C. 1-20 Alkyl, substituted or unsubstituted C 2-20 Olefins, substituted or unsubstituted 3-20 membered cycloalkyl groups, substituted or unsubstituted C4 groups 6-20 Aryl; if substituted, the substituent is a halogen or C. 1-20 alkyl.

[0024] According to embodiments of the present invention, R1, R2, and R3 may be the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C. 1-12 Alkyl, substituted or unsubstituted C 2-12 Olefins, substituted or unsubstituted 3-12 membered cycloalkyl groups, substituted or unsubstituted C4 groups 6-12 Aryl; if substituted, the substituent is a halogen or C. 1-12 alkyl.

[0025] According to embodiments of the present invention, R1, R2, and R3 may be the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C. 1-6 Alkyl, substituted or unsubstituted C 2-6 Olefins, substituted or unsubstituted 3-6 membered cycloalkyl groups, substituted or unsubstituted C 6-10 Aryl; if substituted, the substituent is a halogen or C. 1-6 alkyl.

[0026] According to embodiments of the present invention, R1, R2, and R3 may be the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C. 1-3 Alkyl, substituted or unsubstituted C 2-3 Olefins, substituted or unsubstituted 3-6 membered cycloalkyl groups, substituted or unsubstituted C 6-8Aryl; if substituted, the substituent is a halogen or C. 1-3 alkyl.

[0027] According to an embodiment of the present invention, the first additive can be prepared by methods known in the art or can be obtained through commercial purchase.

[0028] According to an embodiment of the present invention, the first additive is selected from at least one of the compounds shown in Formulas I-1 to I-15:

[0029]

[0030]

[0031] According to an embodiment of the present invention, the fluorocyclic carbonate compound has at least one of the structural formulas shown in Formula II:

[0032]

[0033] In Formula II, R4, R5, R6, and R7 may be the same or different, and are independently selected from hydrogen, fluorine, alkyl, or fluorine-substituted alkyl groups, and at least one of R4, R5, R6, and R7 is selected from fluorine or fluorine-substituted alkyl groups; R8 is absent or -CH2-.

[0034] According to embodiments of the present invention, R4, R5, R6, and R7 may be the same or different, and are independently selected from hydrogen, fluorine, and C. 1-12 Alkyl, fluorine-substituted C 1-12 Alkyl group, and at least one of R4, R5, R6, and R7 is selected from fluorine or fluorine-substituted C4 groups. 1-12 alkyl.

[0035] According to embodiments of the present invention, R4, R5, R6, and R7 may be the same or different, and are independently selected from hydrogen, fluorine, and C. 1-6 Alkyl, fluorine-substituted C 1-6 Alkyl group, and at least one of R4, R5, R6, and R7 is selected from fluorine or fluorine-substituted C4 groups. 1-6 alkyl.

[0036] According to embodiments of the present invention, R4, R5, R6, and R7 may be the same or different, and are independently selected from hydrogen, fluorine, and C. 1-3 Alkyl, fluorine-substituted C 1-3 Alkyl group, and at least one of R4, R5, R6, and R7 is selected from fluorine or fluorine-substituted C4 groups. 1-3 alkyl.

[0037] According to an embodiment of the present invention, the second additive is selected from at least one of the compounds shown in Formulas II-1 to II-8:

[0038]

[0039] According to embodiments of the present invention, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethanesulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, or lithium di(trifluoromethanesulfonyl)imide.

[0040] According to an embodiment of the present invention, the lithium salt accounts for 10 to 15 wt% of the total mass of the electrolyte, for example, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%.

[0041] According to embodiments of the present invention, the organic solvent is selected from carbonates and / or carboxylic esters, wherein the carbonate is selected from one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate; and the carboxylic ester is selected from one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, and ethyl butyrate.

[0042] According to an embodiment of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, wherein the positive active material layer includes a positive active material, a conductive agent, and a binder.

[0043] According to an embodiment of the present invention, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt% positive electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0044] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt% positive electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0045] According to an embodiment of the present invention, the mass percentage of each component in the negative electrode active material layer is: 80-99.8 wt% negative electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0046] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6 wt% negative electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0047] According to an embodiment of the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0048] According to an embodiment of the present invention, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0049] According to an embodiment of the present invention, the negative electrode active material is at least one of silicon-based negative electrode material and carbon-based negative electrode material.

[0050] According to an embodiment of the present invention, the carbon-based anode material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.

[0051] According to an embodiment of the present invention, the silicon-based anode material is selected from at least one of silicon-carbon anode materials and silicon-oxygen anode materials.

[0052] According to an embodiment of the present invention, the negative electrode active material is silicon-carbon / graphite or silicon-oxygen / graphite.

[0053] According to an embodiment of the present invention, the positive electrode active material is selected from one or more of transition metal lithium oxides, lithium iron phosphate, and lithium manganese oxide; the chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0054] The beneficial effects of this invention are:

[0055] This invention provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte comprises a lithium salt, an organic solvent, a first additive, and a second additive. The first additive is selected from cyclic silane compounds containing unsaturated bonds, and the second additive is selected from at least one of fluorinated cyclic carbonate compounds.

[0056] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0057] The battery satisfies the following relationship:

[0058] 115≤(a+1 / 5b) / (t×p)≤700

[0059] Where a represents the percentage of the first additive by mass in the total mass of the electrolyte, b represents the percentage of the second additive by mass in the total mass of the electrolyte, and t represents the mass of the single-sided negative electrode active material layer per unit area, in g / cm³. 2 p represents the specific surface area of ​​the negative electrode active material, in m². 2 / g.

[0060] Correlation between the specific surface area of ​​the negative electrode material per unit area and the content of additives revealed a synergistic effect. Specifically, by controlling the mass of the single-sided negative electrode active material layer per unit area, the specific surface area of ​​the negative electrode active material, and the electrolyte additives, the volume expansion of the negative electrode material can be effectively suppressed. This prevents stress damage to the electrode surface caused by the volume expansion, thus avoiding the rupture of the solid electrolyte film on the electrode surface and the oxidation of the electrolyte. Simultaneously, it significantly improves the high-temperature cycle performance and high-temperature storage performance of the prepared battery, and further enhances the battery's thermal shock safety performance.

[0061] Specifically, the cyclic silane compounds containing unsaturated bonds in the electrolyte exhibit higher stability compared to chain silane compounds containing unsaturated bonds due to their cyclic structure. Under high voltage, oxidative decomposition causes the silicon-carbon bonds formed between the cyclic silicon atoms and branched molecules to break. The broken silicon-oxygen bonds are further oxidized, and some of the oxidation products can undergo polymerization reactions with organic solvents (such as EC) in the electrolyte. The resulting polymer can form a protective film not only on the positive electrode surface but also on the negative electrode surface. Furthermore, the cyclic silane compounds containing unsaturated bonds can generate a compound containing -Si-XF- bonds after continuous oxidation. This compound containing -Si-XF- bonds can participate in film formation on the positive and negative electrode surfaces.

[0062] Under conventional high-temperature, fully charged conditions, the solid electrolyte membrane on the electrode surface exhibits poor thermal stability, making it prone to deformation, loosening, and increased porosity, leading to further solvent reduction at the negative electrode. In contrast, the unsaturated double bonds on the side chains of the cyclic silane compounds of this invention can undergo polymerization on the negative electrode surface to form a Si-XF-containing network protective film. This Si-XF-containing network protective film possesses a certain degree of toughness, enhancing the robustness and structural stability of the SEI film while suppressing its deformation, thus effectively inhibiting the volume expansion of the negative electrode material. Furthermore, by controlling the mass of the single-sided negative electrode active material layer per unit area and the specific surface area of ​​the negative electrode active material, and matching the specific surface area of ​​the negative electrode material per unit area with the additive content, the high-temperature storage performance and high-temperature cycle performance of the battery can be significantly improved. In addition, the introduced second additive can work together with the first additive on the negative electrode surface to form a dense and repairable polymer layer on the negative electrode surface without increasing the impedance, further suppressing the volume expansion of the negative electrode material. The two work together to protect the positive and negative electrodes and prevent further decomposition of the electrolyte. Detailed Implementation

[0063] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0064] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0065] Lithium-ion batteries are prepared through the following steps:

[0066] 1) Preparation of positive electrode sheet

[0067] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried and then rolled and slit to obtain the desired positive electrode sheet.

[0068] 2) Preparation of negative electrode sheet

[0069] A negative electrode active material, silicon-carbon / artificial graphite (containing 5% silicon-carbon and 95% artificial graphite), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5. Deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode active slurry. The negative electrode active slurry was uniformly coated onto both surfaces of a copper foil. The coated copper foil was air-dried at room temperature, then transferred to an 80°C oven for drying for 10 hours. After cold pressing and slitting, the negative electrode sheet was obtained. The mass of the negative electrode active material layer per unit area on one side is t, and the unit is g / cm³. 2 The specific surface area of ​​the negative electrode active material is p, with units of m². 2 / g.

[0070] 3) Preparation of electrolyte

[0071] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / PC / DEC / PP (where EC is ethylene carbonate, PC is propylene carbonate, DEC is diethyl carbonate, and PP is propyl propionate) are mixed evenly in a mass ratio of 10 / 10 / 20 / 60. Then, fully dried lithium hexafluorophosphate (LiPF6) is quickly added to the mixture based on 13 wt% of the total electrolyte mass. After dissolving, 1,3-propanesulfonyl lactone, 1,3,6-hexanetrionitrile (HTCN), adiponitrile (ADN), the first additive, and the second additive are added based on 3 wt% of the total electrolyte mass. The mixture is then mixed evenly to prepare the electrolyte.

[0072] 4) Preparation of lithium-ion batteries

[0073] The positive electrode sheet from step 1), the negative electrode sheet from step 2), and the separator are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell is placed in an outer packaging aluminum foil, and the electrolyte from step 3) is injected into the outer packaging. After vacuum sealing, settling, formation, shaping, and sorting, a lithium-ion battery is obtained. The charge / discharge range of the battery of this invention is 3.0–4.5V.

[0074] Examples 1-14 and Comparative Examples 1-5

[0075] The only differences between Examples 1-14 and Comparative Examples 1-5 are the selection and content of the first and second additives, as well as the mass t of the single-sided negative electrode active material layer per unit area and the specific surface area p of the negative electrode active material, as shown in Table 1.

[0076] Table 1. Composition of the batteries in the examples and comparative examples.

[0077] a％ b％ <![CDATA[t g / cm 2 ]]> <![CDATA[p m 2 / g]]> (a+1 / 5b) / (t×p) Example 1 I-1 / 0.2 II-1 / 5 0.015 0.6 133.3 Example 2 I-1 / 0.5 II-1 / 7 0.018 0.7 150.8 Example 3 I-1 / 1 II-1 / 10 0.010 1.6 187.5 Example 4 I-1 / 2 II-1 / 12 0.013 1.8 188.0 Example 5 I-1 / 0.5 II-1 / 15 0.020 0.9 194.4 Example 6 I-1 / 2 II-1 / 12 0.0035 1.8 698.4 Example 7 I-1 / 2 II-1 / 12 0.013 2.5 135.4 Example 8 I-1 / 2 II-1 / 4 0.013 1.8 119.7 Example 9 I-1 / 6 II-1 / 12 0.013 1.8 359.0 Example 10 I-2 / 2 II-1 / 12 0.013 1.8 188.0 Example 11 I-3 / 2 II-1 / 12 0.013 1.8 188.0 Example 12 I-4 / 2 II-1 / 12 0.013 1.8 188.0 Example 13 I-1 / 2 II-2 / 12 0.013 1.8 188.0 Example 14 I-1 / 2 II-3 / 12 0.013 1.8 188.0 Comparative Example 1 I-1 / 2 II-1 / 12 0.002 1.8 1222.2 Comparative Example 2 I-1 / 2 II-1 / 12 0.013 5.0 67.7 Comparative Example 3 I-1 / 0 II-1 / 12 0.013 1.8 102.6 Comparative Example 4 I-1 / 2 II-1 / 2 0.013 1.8 102.6 Comparative Example 5 I-1 / 2 II-1 / 0 0.013 1.8 85.5

[0078] The battery performance of the above embodiments and comparative examples was tested as follows:

[0079] 1) 45℃ Cyclic Performance Test

[0080] The batteries in Table 1 were subjected to 800 charge-discharge cycles at 45°C and a 1C rate within the charge-discharge cutoff voltage range. The discharge capacity of the first cycle was measured as x1 mAh, and the discharge capacity of the Nth cycle was measured as y1 mAh. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R1 = y1 / x1.

[0081] 2) 85℃ High Temperature Storage Test

[0082] First, let the battery stand for 10 minutes after capacity testing. Then, discharge it at 0.2C to 3V, let it stand for 10 minutes, then fully charge it at 0.5C, cut off at 0.05C, and let it stand for 10 minutes. Test the voltage, internal resistance, and thickness of the fully charged battery at 25±5℃. After placing the fully charged battery in an 85℃ oven for 8 hours, remove the hot battery and test its voltage, internal resistance, and thickness. Also, perform capacity retention and recovery tests.

[0083] 3) Safety performance testing:

[0084] Charge the fully charged battery cells at 0.5C to the upper limit cutoff voltage, maintain the voltage at 0.05C, and place the fully charged sample in a thermal shock test chamber at an ambient temperature of 25℃±5℃. Then, raise the temperature to 140℃±2℃ at a rate of 15℃±2℃ / min and maintain this temperature for 42 minutes before the test ends. Observe whether the battery catches fire or explodes. If it does not catch fire or explode, the safety performance is indicated as "safe" and marked with YES. If it only catches fire, it is indicated as "fire". If it only explodes, it is indicated as "explosion". If it catches fire and explodes, the safety performance is indicated as "fire and explosion" and marked with NO.

[0085] The test results are shown in Table 2 below.

[0086] Table 2 shows the performance test results of the batteries in the examples and comparative examples.

[0087]

[0088] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes a lithium salt, an organic solvent, a first additive, and a second additive. The first additive is selected from cyclic silane compounds containing unsaturated bonds, and the second additive is selected from at least one of fluorinated cyclic carbonate compounds. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The battery satisfies the following relationship: 115≤(a+1 / 5b) / (t×p)≤700 Where a represents the percentage of the first additive by mass in the total mass of the electrolyte, b represents the percentage of the second additive by mass in the total mass of the electrolyte, and t represents the mass of the single-sided negative electrode active material layer per unit area, in g / cm³. 2 p represents the specific surface area of ​​the negative electrode active material, in m². 2 / g; 0.05%≤a≤5%; 3.5%≤b≤15%; 0.0045≤t≤0.028; 0.55≤p≤2.35; The cyclic silane compound containing unsaturated bonds has the structural formula shown in Formula I: Equation I In Formula I, R1, R2, and R3 may be the same or different and are independently selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted olefin, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; if substituted, the substituent is halogen or alkyl; X is selected from -CH2-, -O-, -S-, NH, PH, and BH.

2. The battery according to claim 1, characterized in that, The substituted or unsubstituted alkyl group is a substituted or unsubstituted C14 group. 1-20 Alkyl; the substituted or unsubstituted olefin is a substituted or unsubstituted C14. 2-20 Olefin; the substituted or unsubstituted cycloalkyl group is a substituted or unsubstituted 3-20 membered cycloalkyl group; the substituted or unsubstituted aryl group is a substituted or unsubstituted C group. 6-20 Aryl; if substituted, the substituent is a halogen or C. 1-20 alkyl.

3. The battery according to claim 2, characterized in that, The substituted or unsubstituted alkyl group is a substituted or unsubstituted C14 group. 1-12 Alkyl; the substituted or unsubstituted olefin is a substituted or unsubstituted C14. 2-12 Olefin; the substituted or unsubstituted cycloalkyl group is a substituted or unsubstituted 3-12 membered cycloalkyl group; the substituted or unsubstituted aryl group is a substituted or unsubstituted C group. 6-12 Aryl; if substituted, the substituent is a halogen or C. 1-12 alkyl.

4. The battery according to claim 1, characterized in that, The fluorocyclic carbonate compound has the structural formula shown in Formula II: Formula II In Formula II, R4, R5, R6, and R7 may be the same or different, and are independently selected from hydrogen, fluorine, alkyl, or fluorine-substituted alkyl groups, and at least one of R4, R5, R6, and R7 is selected from fluorine or fluorine-substituted alkyl groups; R8 is absent or -CH2-.

5. The battery according to claim 4, characterized in that, The alkyl group is C 1-12 Alkyl; the fluorinated alkyl group is a fluorinated C14. 1-12 alkyl.

6. The battery according to claim 5, characterized in that, The alkyl group is C 1-6 Alkyl; the fluorinated alkyl group is a fluorinated C14. 1-6 alkyl.

7. The battery according to claim 1, characterized in that, 130≤(a+1 / 5b) / (t×p)≤200.

8. The battery according to claim 1, characterized in that, The lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethanesulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, or lithium di(trifluoromethanesulfonyl)imide. And / or, the organic solvent is selected from carbonates and / or carboxylic esters, wherein the carbonate is selected from one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate; and the carboxylic ester is selected from one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, ethyl butyrate.

9. The battery according to claim 1, characterized in that, The negative electrode active material is at least one of silicon-based negative electrode materials and carbon-based negative electrode materials.

10. The battery according to claim 9, characterized in that, The carbon-based anode material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon; and / or, the silicon-based anode material is selected from at least one of silicon-carbon anode material and silicon-oxygen anode material.

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