Non-aqueous electrolyte and lithium battery

Abstract

The application relates to an electrolyte and a lithium ion secondary battery. The electrolyte comprises an organic solvent, an electrolyte salt and an additive, wherein the additive comprises pyridine boron trifluoride, fluoroethylene carbonate and 1,3,6-hexane trinitrile. The mass percentage of the pyridine boron trifluoride in the electrolyte is 0.1% to 5%; the mass percentage of the fluoroethylene carbonate in the electrolyte is 0.1% to 8%; and the mass percentage of the 1,3,6-hexane trinitrile in the electrolyte is 0.1% to 5%. Through the synergistic effect of the different types of additives, the high-temperature and normal-temperature performances of the high-voltage lithium ion battery are improved, the use of sulfur-containing substances can be reduced, and even the sulfur-containing substances can not be used.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a non-aqueous electrolyte and a lithium battery. BACKGROUND

[0002] With the emergence of new consumer fields such as mobile phones, tablets, smart wear and ETC, lithium ion batteries have shown great advantages due to their high energy density and long cycle life. However, with the continuous diversification of the functions of the corresponding devices and the continuous rise of the power consumption of the power modules, conventional lithium ion batteries have been difficult to meet the user's use requirements. In order to improve the user experience, the development direction of lithium ion batteries has become increasingly clear, that is, to improve the energy density as much as possible or to achieve fast charging under safe conditions. In order to improve the energy density, the industry is currently developing in three ways. One is to seek new material systems, such as lithium cobaltate, lithium-rich manganese-based, ternary high-nickel positive electrode materials, and silicon-carbon negative electrode materials, etc.; the second is to improve the cut-off charging voltage of existing materials, such as 4.4V or above lithium cobaltate batteries, 4.4V or above ternary batteries, etc.; the third is to improve the areal density and the compaction density by changing the battery process, or to use thinner current collectors, tapes and aluminum plastic shells, etc. On the other hand, in order to quickly shorten the charging time and thus achieve the rated capacity, fast-charging lithium ion batteries have emerged, from the initial 0.2C charging to the later 2C charging, and even 5C charging.

[0003] In the digital field with high requirements for volume energy density, the design idea of lithium batteries is to use high-voltage lithium cobaltate & silicon-carbon negative electrode, and the voltage of commercial lithium cobaltate batteries has been gradually increased from the initial 4.2V to 4.48V, which leads to an increase in the internal resistance of the battery. At the same time, with the SVHC list becoming wider and wider, many sulfur-containing compounds in the later stage are likely to be restricted. Therefore, it is necessary to develop an electrolyte that does not contain sulfur and has good high-temperature and cycle performance at high voltage. SUMMARY

[0004] The purpose of the present application is to provide a non-aqueous electrolyte capable of improving the high-temperature performance and discharge performance of lithium batteries at high voltage.

[0005] Another purpose of the present application is to provide a lithium battery containing the non-aqueous electrolyte.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] The first aspect of the present application provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising an organic solvent, an electrolyte lithium salt and an additive, the additive comprising pyridine boron trifluoride, fluoroethylene carbonate, 1,3,6-hexane trinitrile. The mass percentage content of the pyridine boron trifluoride in the non-aqueous electrolyte is 0.1% to 5%. The mass percentage content of the fluoroethylene carbonate in the non-aqueous electrolyte is 0.1% to 10%. The mass percentage content of the 1,3,6-hexane trinitrile in the non-aqueous electrolyte is 0.1% to 5%.

[0008] Preferably, the additive comprises butanedinitrile, and the mass percentage content of the butanedinitrile in the non-aqueous electrolyte is 0.1% to 5%.

[0009] Preferably, the mass percentage content of the butanedinitrile in the non-aqueous electrolyte is 1% to 4%.

[0010] Further preferably, the mass percentage content of the butanedinitrile in the non-aqueous electrolyte is 1% to 3%.

[0011] Preferably, the mass percentage content of the 1,3,6-hexane trinitrile in the non-aqueous electrolyte is 1% to 4%.

[0012] Further preferably, the mass percentage content of the 1,3,6-hexane trinitrile in the non-aqueous electrolyte is 2% to 4%.

[0013] Preferably, the mass percentage content of the pyridine boron trifluoride in the non-aqueous electrolyte is 0.1% to 2%.

[0014] Further preferably, the mass percentage content of the pyridine boron trifluoride in the non-aqueous electrolyte is 0.1% to 1%.

[0015] Preferably, the mass percentage content of the fluoroethylene carbonate in the non-aqueous electrolyte is 2% to 8%.

[0016] Preferably, the non-aqueous electrolyte comprises other additives, the other additives comprising one or more of vinylene carbonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, hexanedinitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,2,3-tris(2-cyanoethoxy)propane, lithium tetrafluoroborate, decanedinitrile, and the mass percentage content of each of the other additives in the non-aqueous electrolyte is 0.1% to 5%.

[0017] Further preferably, the mass percentage content of each of the other additives in the non-aqueous electrolyte is 0.1% to 1%.

[0018] Preferably, the non-aqueous electrolyte does not comprise lithium difluoro(oxalato)borate.

[0019] Preferably, the non-aqueous electrolyte does not include sulfur-containing compounds.

[0020] Preferably, the organic solvent is a mixture of cyclic ester and chain ester, the cyclic ester includes one or more of gamma-butyrolactone, ethylene carbonate, propylene carbonate, and the chain ester includes one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl fluoropropionate, ethyl fluoropropionate, ethyl fluoracetate.

[0021] Preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorophosphate, lithium trifluoromethylsulfonate, lithium bisfluorosulfonimide.

[0022] Preferably, the concentration of the lithium salt is 0.8-3 mol / L.

[0023] Further preferably, the concentration of the lithium salt is 0.8-1.5 mol / L.

[0024] The second aspect of the present application provides a high-voltage lithium battery, which includes a positive electrode, a negative electrode, and an electrolyte, the electrolyte is the non-aqueous electrolyte, and the charge cut-off voltage of the high-voltage lithium battery can be as high as 4.55 V.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] The present application, by compounding the additives of pyridine boron trifluoride, fluorinated ethylene carbonate, 1,3,6-hexane trinitrile, and other components in the non-aqueous electrolyte, can ensure the high-temperature performance and cycle performance of the lithium battery at a conventional voltage, and when the voltage is increased to 4.55 V or even higher, the lithium battery can have more excellent high-temperature performance and discharge performance, as well as more excellent safety performance and electrochemical performance. At the same time, the use of sulfur-containing substances in the non-aqueous electrolyte can be reduced, and even no sulfur-containing substances can be used. DETAILED DESCRIPTION

[0027] The present application will be further described below in conjunction with examples. However, the present application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different specific requirements, and the implementation conditions not mentioned are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as there is no conflict between them.

[0028] With the gradual increase of the voltage of lithium battery, certain negative effects are brought, such as the reaction activity of the material surface is obviously higher than the bulk phase due to the existence of dangling bonds and unsaturated coordination relationship. When the lithium cobalt oxide battery is charged, the following reaction processes occur: (1) the positive material starts to delithiate from the surface; (2) after delithiation, the repulsion between the oxygen atoms in the Li layer is lost, resulting in unstable surface structure; (3) continuous delithiation promotes the gas overflow of the surface lattice activity; (4) the overflow gas leads to poor stability of the surface Co atom and dissolution; (5) the dissolved high-valence Co element also oxidizes the electrolyte and participates in the electrolyte chemical reaction. The solid-liquid interface side reaction is an inevitable problem in the development of lithium batteries. The chemical window of the non-aqueous organic electrolyte currently used is usually lower than 4.4V. When the charging cutoff voltage is higher than 4.4V, the electrolyte will be oxidized and decomposed on the surface of the battery, which leads to a sharp decrease in the capacity of the battery. At the same time, the products of oxidation and decomposition also cover the surface of the electrode material, increasing the internal resistance of the battery. The free transition metal elements catalyze the division of the surface side reaction products, making the electrode material maintain a high active state, which brings hidden dangers.

[0029] With the increasing width of the SVHC list, many sulfur-containing compounds in the later stage are likely to be restricted. Therefore, the inventors of the present application have conducted in-depth research and a large number of experiments, and finally proposed an electrolyte which does not contain sulfur and has good high-temperature and cycle performance at high voltage.

[0030] In the present application, by adding the additives pyridine boron trifluoride, fluoroethylene carbonate, 1,3,6-hexane trinitrile, selectively adding butanedinitrile and other additives to the electrolyte, and combining with other components in the non-aqueous electrolyte, the high-temperature performance and cycle performance of the lithium battery at the conventional voltage are ensured, and when the voltage is increased to 4.55V or even higher, the lithium battery can have more excellent high-temperature performance and discharge performance, as well as more excellent safety performance and electrochemical performance.

[0031] The present application will be further described below in conjunction with the examples. However, the present application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as they do not conflict with each other. In the specific examples in the present application, the raw materials used can be obtained by market purchase.

[0032] Example 1:

[0033] In an argon-filled glove box (H2O content <10 ppm), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, then 4 wt% of fluoroethylene carbonate, 5 wt% of 1,3,6-hexanetricarbonitrile and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0034] Example 2:

[0035] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile and 0.1 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0036] Example 3:

[0037] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0038] Example 4:

[0039] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile and 1 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0040] Example 5:

[0041] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile and 0.5wt% pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0042] Example 6:

[0043] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile and 0.5wt% pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0044] Example 7:

[0045] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile and 0.5wt% pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0046] Example 8:

[0047] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile and 0.5wt% pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0048] Example 9:

[0049] In an argon-filled glove box (H2O content <10 ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile and 0.5wt% pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0050] Example 10:

[0051] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 2 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile and 1 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0052] Example 11:

[0053] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of tris(trimethylsilyl)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0054] Example 12:

[0055] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of tris(trimethylsilyl)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0056] Example 13:

[0057] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of tris(trimethylsilyl)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0058] Example 14:

[0059] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of lithium difluoro(oxalato)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0060] Example 15:

[0061] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of lithium difluoro(oxalato)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0062] Comparative Example 1:

[0063] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of lithium difluoro(oxalato)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0064] Comparative Example 2:

[0065] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of lithium difluoro(oxalato)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0066] Comparative Example 3:

[0067] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% of succinonitrile, 4 wt% of fluoroethylene carbonate, 3 wt% of 1,3,6-hexanetricarbonitrile, 0.5 wt% of lithium difluoro(oxalato)borate and 0.5 wt% of pyridine boron trifluoride were added to the electrolyte, respectively, to prepare the electrolyte.

[0068] Comparative Example 4:

[0069] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile, and 0.5wt% lithium difluoro(oxalato)borate were added to the electrolyte, respectively, to prepare the electrolyte.

[0070] Comparative Example 5:

[0071] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile, and 0.5wt% lithium difluoro(oxalato)borate were added to the electrolyte, respectively, to prepare the electrolyte.

[0072] Comparative Example 6:

[0073] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile, and 0.8wt% 1-3 propane sultone were added to the electrolyte, respectively, to prepare the electrolyte.

[0074] Comparative Example 7:

[0075] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile, and 1wt% 1-3 propane sultone were added to the electrolyte, respectively, to prepare the electrolyte.

[0076] Comparative Example 8:

[0077] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2wt% butanedinitrile, 4wt% fluoroethylene carbonate, 3wt% 1,3,6-hexanetricarbonitrile, and 2wt% 1-3 propane sultone were added to the electrolyte, respectively, to prepare the electrolyte.

[0078] Comparative Example 9:

[0079] In an argon-filled glove box (H2O content < 10 ppm), DEC, EC, PC, EP and PP were mixed uniformly at a volume ratio of 1:2:1:3:3, 1.15 mol / L LiPF6 was added to the mixed solution, and then 2 wt% butanedinitrile, 4 wt% fluoroethylene carbonate, 3 wt% 1,3,6-hexanetricarbonitrile, and 4 wt% 1,3-propane sultone were added to the electrolyte, respectively, to prepare the electrolyte.

[0080] The electrolytes prepared in the above examples and comparative examples were assembled into lithium cobaltate-graphite batteries, respectively. The capacity retention rate and the battery swelling rate of the above lithium cobaltate-graphite batteries after 4 hours of high-temperature storage at 85°C were tested, respectively, and the test data are shown in Table 1. The test method was as follows: charging to 4.55V at 1C under constant current / constant voltage (CC / CV) conditions at 25°C, then storing in an oven at 85°C for 4 hours, and then discharging to 3.0V at 1C after storage, respectively, to test the capacity after 4 hours of high-temperature storage at 85°C and the battery thickness; the capacity and the battery thickness of the above batteries after charging under the same conditions and discharging under the same conditions without high-temperature storage were tested, respectively. The capacity retention rate of the above batteries after 4 hours of high-temperature storage at 85°C was equal to the capacity after 4 hours of high-temperature storage at 85°C divided by the capacity without high-temperature storage. The battery swelling rate of the above batteries after 4 hours of high-temperature storage at 85°C was equal to the difference between the battery thickness after storage and the battery thickness before storage divided by the battery thickness before storage. The 45°C 200 cycle capacity retention rate and the 50% SCO, 2C 10s DCR of the above lithium cobaltate-graphite batteries were tested, respectively. The test method for the 45°C 200 cycle capacity retention rate was as follows: charging to 4.55V at 1C under constant current / constant voltage (CC / CV) conditions at 45°C, and then discharging to 3.0V at 1C, respectively, to test the battery capacity after the first charge-discharge and the battery capacity after 200 cycles of charge-discharge, and the 45°C 200 cycle capacity retention rate was equal to the battery capacity after 200 cycles of charge-discharge divided by the battery capacity after the first charge-discharge; the test method for the 50% SCO, 2C 10s DCR was as follows: the voltage difference and the current ratio of the battery under 50% SCO state were tested under 2C constant current discharge for 10s; and the relevant experimental data are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] From the comparison of Example 1 and Comparative Example 1, it can be seen that, by adding the additive compound of fluoroethylene carbonate, 1,3,6-hexanetricarbonitrile and pyridine boron trifluoride to the electrolyte, the high-temperature storage performance and the capacity retention rate at high temperature of the battery are both improved, and the high-temperature swelling rate and the DCR of the battery are reduced. From the comparison of Examples 2-10 and Comparative Examples 4-9, it can be seen that, by adding the additive compound of succinonitrile, fluoroethylene carbonate, 1,3,6-hexanetricarbonitrile and pyridine boron trifluoride to the electrolyte, and adjusting the ratio of each additive, the battery gas production and the battery impedance can be significantly reduced while the high-temperature storage performance and the high-temperature capacity retention rate are equivalent or better.

[0085] From the comparison of Examples 2-9 and Examples 11-13, it can be seen that, by adding the additive compound of succinonitrile, fluoroethylene carbonate, 1,3,6-hexanetricarbonitrile, pyridine boron trifluoride and other additives to the electrolyte, the capacity retention rate of the battery at 85°C high-temperature storage for 4H and the cycle capacity retention rate of 45°C 200 cycles under the condition of 4.55V can be further improved, and the battery swelling rate (%) and the DCR of 50%SCO, 2C10s of the battery at 85°C high-temperature storage for 4H under the condition of 4.55V can be further reduced. It is shown that the additive compound of succinonitrile, fluoroethylene carbonate, 1,3,6-hexanetricarbonitrile, pyridine boron trifluoride and other additives can further improve the high-temperature performance and the discharge performance of the battery, and further improve the safety performance of the battery.

[0086] The above detailed description of the present application is intended to enable those skilled in the art to understand and implement the present application, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A non-aqueous electrolyte, said non-aqueous electrolyte comprising an organic solvent, an electrolyte lithium salt, and additives, characterized in that, The additives include boron trifluoride pyridine, fluoroethylene carbonate, 1,3,6-hexanetrionitrile and succinate; The boron trifluoride pyridine in the non-aqueous electrolyte has a mass percentage content of 0.1% to 1%. The fluoroethylene carbonate has a mass percentage content of 2% to 8% in the non-aqueous electrolyte; The mass percentage of the 1,3,6-hexanetrionitrile in the non-aqueous electrolyte is 2% to 4%. The succinic anionylene in the non-aqueous electrolyte has a mass percentage of 1% to 3%. The non-aqueous electrolyte does not contain sulfur-containing compounds.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes other additives, including one or more of the following: ethylene carbonate, tris(trimethylsilane)borate, tris(trimethylsilane)phosphate, adiponitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,2,3-tris(2-cyanoethoxy)propane, lithium tetrafluoroborate, and sebacate, wherein the mass percentage of each of the other additives in the non-aqueous electrolyte is 0.1% to 5%.

3. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte does not include lithium difluorooxalate borate.

4. The non-aqueous electrolyte according to claim 1, characterized in that, The organic solvent is a mixture of cyclic esters and chain esters, wherein the cyclic esters include one or more of γ-butyrolactone, ethylene carbonate, and propylene carbonate; The chain esters include one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl fluoropropionate, ethyl fluoropropionate, and ethyl fluoropropionate.

5. The non-aqueous electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, anhydrous lithium perchlorate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, and lithium difluorosulfonylimide, and the concentration of the lithium salt is 0.8 to 3 mol / L.

6. A lithium battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte includes the non-aqueous electrolyte as described in any one of claims 1 to 5.

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