A battery electrolyte and a battery containing the same

Abstract

This invention relates to a battery electrolyte and a battery containing the electrolyte. To improve the problems of gas generation and capacity loss during high-temperature storage of lithium cobalt oxide batteries, this invention provides a battery electrolyte comprising a base electrolyte and additives, wherein the additives include additive A and additive B. Additive A is selected from one or more compounds containing unsaturated alkenyl (alkyne) groups, and additive B is selected from one or more sulfur-containing additives and / or phosphorus-containing additives. By using additives A and B in combination, and further through their synergistic effect with other components in the electrolyte, this invention can simultaneously ensure a smaller increase in internal resistance and a smaller increase in thickness expansion during high-temperature storage, thereby achieving a higher capacity recovery rate and suppressing battery gas generation.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery electrolyte and a battery containing the electrolyte. Background Technology

[0002] Lithium cobalt oxide (LCO) batteries, with their high volumetric energy density, are currently a mainstream lithium-ion battery used in portable and smart electronic products. However, in recent years, with the continuous improvement of consumer demands and product technology, the market has placed higher requirements on battery performance. For example, the state of charge and the environment in which batteries are transported, used, and stored are complex and variable, making better high-temperature storage performance particularly important. Generally, after high-temperature storage, batteries will experience problems such as gas expansion, increased impedance, and voltage drop, which will lead to capacity loss, shortened lifespan, and even battery failure or safety hazards.

[0003] The main mechanisms by which high-temperature storage affects battery performance are as follows: (1) Under high-temperature conditions, the structure of positive and negative electrode materials is prone to change, resulting in irreversible phase transitions; (2) The dissolution and reduction reactions of transition metal elements damage the SEI film and consume active Li. + (3) Self-decomposition of the electrolyte or side reactions at the electrode / electrolyte interface. As an important medium connecting the positive and negative electrodes, the electrolyte affects the stability of the electrode / electrolyte interface film and plays a key role in the performance of the battery. Therefore, in order to better address the impact of high-temperature storage on the performance of lithium cobalt oxide batteries, it is necessary to optimize the electrolyte formulation. Summary of the Invention

[0004] The purpose of this invention is to provide a battery electrolyte that can improve the stability of lithium cobalt oxide batteries under high-temperature storage, suppress high-temperature gas generation, and improve the problem of capacity loss during high-temperature storage.

[0005] Another object of the present invention is to provide a lithium cobalt oxide battery containing the above-described battery electrolyte.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a battery electrolyte, the battery electrolyte comprising a base electrolyte and additives, the base electrolyte comprising an organic solvent and a lithium salt, the additives comprising additive A and additive B, wherein additive A is selected from one or more compounds containing unsaturated alkenyl (alkynyl) groups, and additive B is selected from one or more of sulfur-containing additives and / or phosphorus-containing additives.

[0008] In this embodiment of the invention, the additive A is selected from one or more of triallyl isocyanurate (TAIC), tetravinylsilane (TVSi), triargyl phosphate (TPP), vinyl ethylene carbonate (VEC), propargyl propionate, and propargyl benzoate.

[0009] In this embodiment of the invention, the additive B is selected from one or more of vinyl sulfate (DTD), 1,3-propanesulfonyl lactone (1,3-PS), methylene disulfonate (MMDS), lithium difluorophosphate (LiDFP), lithium difluorobis(oxalato) phosphate (LiDFOP), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), and tris(2,2,2-trifluoroethyl) phosphate (TFP).

[0010] According to some embodiments of the present invention, the additive consists of additive A and additive B.

[0011] According to some embodiments of the present invention, the mass ratio of additive A to additive B is (1-3):1, for example 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1.

[0012] According to some embodiments of the present invention, the additive A is added at a mass of 1% to 5% of the total mass of the battery electrolyte, for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, or 5%.

[0013] According to some embodiments of the present invention, the additive B is added at a mass of 1% to 3% of the total mass of the battery electrolyte, for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0014] According to some embodiments of the present invention, the additive A comprises at least triallyl isocyanurate and tetravinylsilane, and the mass ratio of the triallyl isocyanurate and tetravinylsilane is (0.5-3):1, for example 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1.

[0015] According to some embodiments of the present invention, the additive B comprises at least vinyl sulfate.

[0016] In embodiments of the present invention, the organic solvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl propionate, propyl propionate, methyl difluoroacetate, and ethyl difluoroacetate.

[0017] According to some embodiments of the present invention, the organic solvent includes dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, and the volume ratio of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate is (0.5-1.5):(0.5-1.5):1.

[0018] Further, the volume ratio of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate is (0.8-1.2):(0.8-1.2):1.

[0019] According to other embodiments of the present invention, the organic solvent includes dimethyl carbonate, ethyl methyl carbonate and ethyl difluorocarbonate, and the volume ratio of dimethyl carbonate, ethyl methyl carbonate and ethyl difluorocarbonate is (0.5-1.5):(0.5-1.5):1.

[0020] Further, the volume ratio of dimethyl carbonate, ethyl methyl carbonate and ethyl difluoroacetate is (0.8-1.2):(0.8-1.2):1.

[0021] In embodiments of the present invention, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium dioxolaneborate.

[0022] In this embodiment of the invention, the concentration of the lithium salt in the basic electrolyte is 0.1 to 1.5 mol / L, for example 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L.

[0023] According to some embodiments of the present invention, the lithium salt comprises lithium hexafluorophosphate and lithium dioxalate borate, and the molar ratio of lithium hexafluorophosphate to lithium dioxalate borate is (3-5):1.

[0024] Furthermore, the molar ratio of lithium hexafluorophosphate to lithium dioxaborate is (3.5–4.5):1.

[0025] According to some embodiments of the present invention, the lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide, and the molar ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (3-5):1.

[0026] Furthermore, the molar ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (3.5–4.5):1.

[0027] In this embodiment of the invention, the basic electrolyte further includes basic additives, which include fluoroethylene carbonate and / or vinylene carbonate.

[0028] According to some embodiments of the present invention, the base additive is composed of fluoroethylene carbonate and vinylene carbonate, and the mass ratio of the fluoroethylene carbonate and vinylene carbonate is (0.5-2):1, for example 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1.

[0029] According to some embodiments of the present invention, the basic additive is added at a mass of 1% to 5% of the total mass of the basic electrolyte, for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, or 5%.

[0030] A second aspect of the present invention also provides a battery comprising the battery electrolyte described above.

[0031] In this embodiment of the invention, the positive electrode active material of the battery is lithium cobalt oxide.

[0032] In this embodiment of the invention, the negative electrode active material of the battery is graphite, including natural graphite or artificial graphite.

[0033] Preferably, the battery operates at a voltage of 4.2V or higher.

[0034] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0035] This invention utilizes the combined use of additive A (containing unsaturated alkenyl (alkyne) compounds) and additive B (containing sulfur-based additives and / or phosphorus-based additives), and further leverages their synergistic effect with other components in the electrolyte to simultaneously ensure a smaller internal resistance growth rate and a smaller thickness expansion rate during high-temperature storage, thereby achieving a higher capacity recovery rate and improving the problems of gas generation and capacity loss during high-temperature storage. Detailed Implementation

[0036] To address the issues of gas generation and capacity loss during high-temperature storage of lithium cobalt oxide batteries, the inventors of this application conducted extensive research and experimental verification on the electrolyte formulation. By using a combination of additive A (containing unsaturated alkenyl (alkyne) compounds) and additive B (containing sulfur-based and / or phosphorus-based additives), additive A can form a film earlier at higher potentials and is more prone to forming cross-linked molecular structures, reducing gas generation at high temperatures. The addition of additive B helps mitigate the high impedance effect caused by additive A, thus simultaneously ensuring a smaller internal resistance growth rate and a smaller thickness expansion rate during high-temperature storage, thereby achieving a higher capacity recovery rate. Furthermore, by adjusting the amount of additives, lithium salt combinations, and solvent types, the composition and structure of the positive and negative electrode interface films are further optimized, thereby constructing an interface film protective film with high ionic conductivity and good stability, further improving the high-temperature storage performance of lithium cobalt oxide batteries.

[0037] Specifically, the improved battery electrolyte of the present invention includes a base electrolyte and additives. The base electrolyte includes an organic solvent and a lithium salt. The additives include additive A and additive B. Additive A is selected from one or more compounds containing unsaturated alkenyl (alkynyl) groups, and additive B is selected from one or more sulfur-containing additives and / or phosphorus-containing additives. Additive A is selected from one or more of triallyl isocyanurate, tetravinylsilane, triargyl phosphate, vinyl vinyl carbonate, propargyl propionate, and propargyl benzoate. Additive B is selected from one or more of vinyl sulfate, 1,3-propanesulfonate lactone, methanedisulfonate, lithium difluorophosphate, lithium difluorobis(oxalato) phosphate, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, and tris(2,2,2-trifluoroethyl) phosphate.

[0038] More specifically, the organic solvent of the basic electrolyte includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl propionate, propyl propionate, methyl difluoroacetate, and ethyl difluoroacetate; the lithium salt of the basic electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium dioxolaneborate; the basic electrolyte also includes basic additives, which include fluoroethylene carbonate and / or vinylene carbonate.

[0039] Further, additive A includes at least triallyl isocyanurate and tetravinylsilane, and the mass ratio of triallyl isocyanurate to tetravinylsilane is (0.5-3):1; additive B includes at least vinyl sulfate; the mass ratio of additive A to additive B is (1-3):1; the mass of additive A is 1%-5% of the total mass of the battery electrolyte; and the mass of additive B is 1%-3% of the total mass of the battery electrolyte.

[0040] Further, the organic solvent in the basic electrolyte includes dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate, and the volume ratio of dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate is (0.5–1.5):(0.5–1.5):1; or, the organic solvent includes dimethyl carbonate, ethyl methyl carbonate, and ethyl difluorophosphate, and the volume ratio of dimethyl carbonate, ethyl methyl carbonate, and ethyl difluorophosphate is (0.5–1.5):(0.5–1.5):1; the lithium salt in the basic electrolyte includes lithium hexafluorophosphate and oxalic acid. The electrolyte contains lithium borate, wherein the molar ratio of lithium hexafluorophosphate to lithium dioxalate borate is (3-5):1; or, the lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the molar ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (3-5):1; the basic additive in the basic electrolyte is composed of fluoroethylene carbonate and vinylene carbonate, wherein the mass ratio of fluoroethylene carbonate to vinylene carbonate is (0.5-2):1; and the mass of the basic additive is 1%-5% of the total mass of the basic electrolyte.

[0041] The battery electrolyte of the present invention is suitable for high-voltage lithium cobalt oxide batteries, that is, the positive electrode material of the battery is lithium cobalt oxide and the working voltage of the battery is 4.2V or above.

[0042] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0043] Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available products.

[0044] Unless otherwise specified, the operations involved in the preparation of battery electrolyte and battery assembly in the following embodiments and comparative examples are all prior art.

[0045] In the following examples and comparative examples, the mass fraction of a component in the base electrolyte refers to the mass percentage of that component relative to the total mass of the base electrolyte, and the concentration of a lithium salt refers to the concentration of that lithium salt in the base electrolyte. The mass fraction of an additive added to the base electrolyte is the percentage of that additive relative to the total mass of the battery electrolyte.

[0046] Examples 1-10 and Comparative Examples 1-4

[0047] Prepare the battery electrolyte according to the component amounts in Table 1. Taking Example 1 as an example, the operation method includes:

[0048] (1) Prepare the basic electrolyte. In a glove box filled with argon atmosphere (H2O content <1ppm, O2 content <1ppm), accurately measure electronic grade EC, DMC and EMC solvents in a volume ratio of 1:1:1. Mix them and slowly add 1mol / L (1M) lithium salt LiPF6 while stirring. Stir thoroughly until the lithium salt is completely dissolved. Then add 1% FEC and 1% VC by mass in sequence. Stir evenly to obtain the basic electrolyte.

[0049] (2) While stirring, add 1% TAIC, 1% TVSi and 1% DTD by mass to the base electrolyte in sequence.

[0050] Table 1

[0051]

[0052]

[0053] In Table 1, LiPF6: lithium hexafluorophosphate; LiFSI: lithium difluorosulfonylimide; EC: ethylene carbonate; DMC: dimethyl carbonate; EMC: ethyl methyl carbonate; DFEA: ethyl difluorophosphate; FEC: fluoroethylene carbonate; VC: vinylene carbonate; DTD: ethylene sulfate; LiDFP: lithium difluorophosphate; TMSP: tris(trimethylsilane) phosphite; TAIC: triallyl isocyanurate; TVSi: tetravinylsilane.

[0054] Battery fabrication and electrochemical performance testing:

[0055] The battery electrolytes from Examples 1-10 and Comparative Examples 1-4 were injected into 4.2V lithium cobalt oxide / graphite pouch cells with a capacity of 800mAh, respectively. Then, the cells were subjected to normal procedures including settling, formation, secondary sealing, capacity testing, and detection. Specific high-temperature storage test conditions are as follows:

[0056] At room temperature, using a Shenzhen Xinwei battery tester, the battery was charged to 4.2V at a rate of 0.5C under constant current / constant voltage (CC / CV) conditions, and then transferred to a 60℃ oven for 28 days.

[0057] The internal resistance of the battery before and after high-temperature storage was measured using an HP3560 precision battery internal resistance tester. The battery internal resistance growth rate (%) was calculated as follows: (Battery internal resistance after high-temperature storage - Initial internal resistance) / Initial internal resistance × 100%. The battery thickness before and after high-temperature storage was measured using a Mulimtech battery thickness tester. The battery thickness swelling rate (%) was calculated as follows: (Battery thickness after high-temperature storage - Initial thickness) / Initial thickness × 100%.

[0058] After being stored in a 60℃ oven for 28 days, the batteries were transferred to room temperature. Then, using a Shenzhen Xinwei battery tester, the batteries were discharged at a rate of 0.5C to 2.75V, then charged at a rate of 0.5C to 4.2V, and then discharged at a rate of 0.5C to 2.75V for one charge-discharge cycle. The discharge capacity of the batteries before and after high-temperature storage was tested, and the capacity recovery rate was calculated as: discharge capacity after high-temperature storage / initial capacity × 100%. The discharge capacity after storage is the discharge capacity tested during the charge-discharge cycle of the battery after being stored at high temperature and then transferred to room temperature. The initial capacity is the discharge capacity tested during the first charge-discharge cycle of the battery before high-temperature storage under the same conditions at room temperature.

[0059] The test results are shown in Table 2.

[0060] Table 2

[0061] Battery Internal resistance growth rate Battery thickness swelling rate Capacity recovery rate Example 1 27.2％ 19.2％ 84.6％ Example 2 31.1％ 19.5％ 83.5％ Example 3 29.1％ 18.7％ 82.1％ Example 4 25.3％ 20.8％ 85.9％ Example 5 24.2％ 21.6％ 86.5％ Example 6 22.4％ 19.4％ 87.1％ Example 7 21.2％ 15.8％ 89.2％ Example 8 20.5％ 16.5％ 89.5％ Example 9 18.1％ 13.2％ 90.1％ Example 10 16.5％ 15.3％ 91.2％ Comparative Example 1 33.9％ 29.0％ 81.3％ Comparative Example 2 42.1％ 20.3％ 82.4％ Comparative Example 3 26.8％ 42.1％ 77.8％ Comparative Example 4 20.3％ 33.6％ 80.7％

[0062] According to Tables 1 and 2, using a combination of additives containing unsaturated alkenyl (alkyne) compounds and additives containing sulfur or phosphorus can simultaneously ensure a smaller internal resistance growth rate and a smaller thickness expansion rate during high-temperature storage, compared to using electrolytes containing only unsaturated alkenyl (alkyne) compounds or additives containing sulfur or phosphorus, thus achieving a higher capacity recovery rate.

[0063] Some examples and comparative examples show that when sulfur- or phosphorus-containing additives are selected using DTD, they are more effective than LiDFP and TMSP in improving the high impedance caused by additives containing unsaturated alkenyl (alkyne) compounds. The examples further show that by adjusting the amount of additives, lithium salt combinations, and solvent types, the composition and structure of the positive and negative electrode interface films can be further optimized, thereby constructing interface films with high ionic conductivity and good stability. Examples 9 and 10, in particular, demonstrate better improvement in high-temperature stable capacity loss and gas expansion problems in the battery.

[0064] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A battery electrolyte, characterized in that the battery electrolyte comprises a base electrolyte and additives, the base electrolyte comprising an organic solvent and a lithium salt, the additives comprising additive A and additive B, wherein additive A is selected from one or more compounds containing unsaturated alkenyl (alkynyl) groups, and additive B is selected from one or more sulfur-containing additives and / or phosphorus-containing additives.

2. The battery electrolyte according to claim 1, characterized in that, Additive A is selected from one or more of triallyl isocyanurate, tetravinylsilane, triargyl phosphate, vinyl ethylene carbonate, propargyl propionate, and propargyl benzoate. And / or, the additive B is selected from one or more of vinyl sulfate, 1,3-propanesulfonyl lactone, methanedisulfonate, lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, and tris(2,2,2-trifluoroethyl) phosphate.

3. The battery electrolyte according to claim 1, characterized in that, The additive consists of additive A and additive B. And / or, the mass ratio of additive A to additive B is (1-3):1; And / or, the mass of additive A is 1% to 5% of the total mass of the battery electrolyte; And / or, the mass of additive B is 1% to 3% of the total mass of the battery electrolyte.

4. The battery electrolyte according to claim 1, characterized in that, The additive A comprises at least triallyl isocyanurate and tetravinylsilane, and the mass ratio of the triallyl isocyanurate to tetravinylsilane is (0.5-3):

1. And / or, the additive B includes at least vinyl sulfate.

5. The battery electrolyte according to claim 1, characterized in that, The organic solvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl propionate, propyl propionate, methyl difluoroacetate, and ethyl difluoroacetate. And / or, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium dioxolaneborate; And / or, the concentration of the lithium salt in the base electrolyte is 0.1 to 1.5 mol / L.

6. The battery electrolyte according to claim 1, characterized in that, The basic electrolyte also includes basic additives, which include fluoroethylene carbonate and / or vinylene carbonate.

7. The battery electrolyte according to claim 6, characterized in that, The basic additive is composed of fluoroethylene carbonate and vinylene carbonate, and the mass ratio of the fluoroethylene carbonate and vinylene carbonate is (0.5-2):

1. And / or, the mass of the base additive is 1% to 5% of the total mass of the base electrolyte.

8. The battery electrolyte according to claim 1, characterized in that, The organic solvent includes dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate, and the volume ratio of dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate is (0.5-1.5):(0.5-1.5):

1. Alternatively, the organic solvent may include dimethyl carbonate, ethyl methyl carbonate, and ethyl difluorocarbonate, wherein the volume ratio of dimethyl carbonate, ethyl methyl carbonate, and ethyl difluorocarbonate is (0.5–1.5):(0.5–1.5):1; And / or, the lithium salt comprises lithium hexafluorophosphate and lithium dioxalate borate, and the molar ratio of lithium hexafluorophosphate to lithium dioxalate borate is (3-5):1; Alternatively, the lithium salt may include lithium hexafluorophosphate and lithium difluorosulfonylimide, and the molar ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (3-5):

1.

9. A battery, characterized in that: The battery includes the battery electrolyte as described in any one of claims 1 to 8.

10. The battery according to claim 9, characterized in that: The positive electrode active material of the battery is lithium cobalt oxide.

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