High-voltage nonaqueous electrolyte and lithium ion battery

Abstract

The application discloses a high-voltage nonaqueous electrolyte and a lithium ion battery. In order to solve the problem of poor electrochemical performance of the lithium ion battery under high voltage, the application provides a high-voltage nonaqueous electrolyte, which comprises an organic solvent, an electrolyte lithium salt and an additive, wherein the additive comprises tripropargyl borate, fluoroethylene carbonate and 1,2,3,4,5-penta(2-cyanoethyloxy)pentane. Through the synergistic cooperation of fluoroethylene carbonate, 1,2,3,4,5-penta(2-cyanoethyloxy)pentane and tripropargyl borate, the capacity retention rate after high-temperature storage and the high-temperature cycle performance of the LCO system lithium ion battery with high voltage and high specific energy can be effectively improved, the swelling of the LCO system lithium ion battery under high-temperature conditions can be effectively inhibited, the stability of the LCO system lithium ion battery can be improved, and the high-temperature, normal-temperature and rate performance of the high-voltage lithium ion battery are balanced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a high-voltage non-aqueous electrolyte and a lithium-ion battery. Background Technology

[0002] With the rapid development of mobile phones, tablets, smart wearables, and ETC devices, higher demands are being placed on the performance of lithium-ion batteries. Conventional lithium-ion batteries are no longer sufficient to meet user needs. To improve the user experience, there is a desire to maximize energy density or achieve fast charging while ensuring safety. To improve energy density, the industry is currently focusing on three main aspects: First, developing new material systems, such as lithium cobalt oxide, lithium-rich manganese-based batteries, and ternary high-nickel cathode materials, and silicon-carbon anode materials. Second, increasing the cutoff charging voltage of existing materials, such as developing lithium cobalt oxide batteries with charging voltages above 4.5V and ternary batteries above 4.4V. Third, improving battery manufacturing processes to increase areal density and compaction density, or using thinner current collectors, tapes, and aluminum-plastic casings. Furthermore, fast-charging lithium-ion batteries are developing rapidly, from the initial 0.2C charging to later 2C and even 5C charging, with the charging time required to reach the rated capacity becoming increasingly shorter.

[0003] As the voltage of commercial lithium cobalt oxide batteries gradually increases from 4.2V to 4.5V, some negative effects have emerged. For example, the surface of the material has dangling bonds and unsaturated coordination relationships, which makes its reactivity significantly higher than that of the bulk phase. During the charging of lithium cobalt oxide batteries, the following reaction processes occur: (1) the cathode material begins to delithiate from the surface; (2) after delithiation, the oxygen atoms in the Li layer lose their barrier and repel each other, resulting in unstable surface structure; (3) continuous delithiation promotes the surface lattice activity and causes gas leakage; (4) the leakage gas leads to poor stability and dissolution of surface Co atoms; (5) the dissolved high-valence Co elements also oxidize the electrolyte and participate in the electrolyte chemical reaction. Solid-liquid interface side reactions are an unavoidable problem in the development of lithium batteries. The chemical window of the non-aqueous organic electrolyte currently used is usually lower than 4.5V. When the charging cutoff voltage is higher than 4.5V, the electrolyte will undergo oxidation and decomposition on the battery surface, causing the battery capacity to "plummet". The products of oxidation and decomposition will cover the surface of the electrode material and increase the internal resistance of the battery. The separation of by-reaction products on the catalytic surface of free transition metal elements keeps the electrode material in a highly active state, which in turn brings safety hazards.

[0004] Therefore, it is essential to develop an electrolyte that can improve the performance of high-voltage, high-specific-energy lithium-ion secondary batteries. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an electrolyte suitable for high-voltage, high-specific-energy lithium-ion secondary batteries. This electrolyte not only has stable cycle performance at room temperature, but also suppresses the gas expansion, cycle decay and thickness increase of lithium-ion batteries under high-temperature conditions.

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

[0007] A high-voltage non-aqueous electrolyte comprises an organic solvent, an electrolyte lithium salt, and additives, said additives including triargyl propyl borate, fluoroethylene carbonate, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane.

[0008] Preferably, the mass percentage of the triargyl borate in the high-voltage non-aqueous electrolyte is 0.1% to 1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0009] More preferably, the mass percentage of the triargyl borate in the high-voltage non-aqueous electrolyte is 0.1% to 0.5%.

[0010] Preferably, the fluoroethylene carbonate in the high-voltage non-aqueous electrolyte has a mass percentage content of 0.1% to 10%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%.

[0011] More preferably, the fluoroethylene carbonate has a mass percentage content of 2% to 8% in the high-voltage non-aqueous electrolyte.

[0012] Preferably, the mass percentage of 1,2,3,4,5-penta(2-cyanoethoxy)pentane in the high-voltage non-aqueous electrolyte is 0.1% to 5%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0013] More preferably, the 1,2,3,4,5-penta(2-cyanoethoxy)pentane in the high-voltage non-aqueous electrolyte has a mass percentage content of 0.5% to 3%.

[0014] Preferably, the additive further includes other additives, namely vinylene carbonate, ethylene ethylene carbonate, 1,3-propane sulpholactone, 1,3-(1-propene) sulpholactone, methanedisulfonate, tris(trimethylsilane)borate, tris(trimethylsilane)phosphate, methyl cis-butene dianone, succinic anhydride, biphenyl, cyclohexylbenzene, trioctyl phosphate, fluoroethylene carbonate, succinate, adiponitrile, 1,3,6-hexanetrionitrile, 1, One or more of the following: 2-bis(2-cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,2,3-tris(2-cyanoethoxy)propane, sebaonitrile, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium hexafluoroarsenate, anhydrous lithium perchlorate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium difluorobis(oxalate)phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazolium, and lithium fluorosulfonate.

[0015] More preferably, the other additives in the high-voltage non-aqueous electrolyte have a mass percentage of 0.1% to 8%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0016] More preferably, the other additives are present in the high-voltage non-aqueous electrolyte at a mass percentage of 0.1% to 5%.

[0017] Preferably, the organic solvent is a mixture of cyclic esters and chain esters, wherein the cyclic ester is one or more of γ-butyrolactone, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and the chain ester is 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.

[0018] According to some specific embodiments, the organic solvent is preferably ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, and propyl propionate. Conventional carbonate solvents are easily catalytically decomposed under high voltage conditions. By using triargyl propargyl borate, fluoroethylene carbonate, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane in a synergistic manner, the catalytic decomposition of carbonate solvents can be effectively suppressed, thereby reducing battery gas production and metal ion dissolution.

[0019] More preferably, the organic solvent further includes ethyl fluoroacetate, such as 2,2-difluoroethyl acetate.

[0020] Preferably, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, anhydrous lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazolium, and lithium fluorosulfonate.

[0021] According to some specific embodiments, the lithium salt is lithium hexafluorophosphate.

[0022] More preferably, the concentration of the lithium salt in the high-voltage non-aqueous electrolyte is 0.8 to 3 mol / L, for example, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L, or 3 mol / L.

[0023] More preferably, the concentration of the lithium salt in the high-voltage non-aqueous electrolyte is 0.8–1.6 mol / L.

[0024] A second aspect of the present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the aforementioned high-voltage non-aqueous electrolyte.

[0025] Preferably, the voltage of the lithium ion is higher than 4.5V.

[0026] Preferably, the lithium-ion battery is an LCO system lithium-ion battery.

[0027] By adopting the above technical solution, the present invention has the following advantages compared with other processes:

[0028] This invention, through the synergistic combination of fluoroethylene carbonate, 1,2,3,4,5-penta(2-cyanoethoxy)pentane, and triargyl propyl borate, not only effectively improves the capacity retention and high-temperature cycle performance of high-voltage, high-specific-energy LCO system lithium-ion batteries after high-temperature storage, but also effectively suppresses the swelling of LCO system lithium-ion batteries under high-temperature conditions, improving the stability of LCO system lithium-ion batteries, thus taking into account the high-temperature, room-temperature, and rate performance of high-voltage lithium-ion batteries. Attached Figure Description

[0029] Figure 1 The NMR C-NMR spectrum of 1,2,3,4,5-penta(2-cyanoethoxy)pentane;

[0030] Figure 2 The NMR spectrum of 1,2,3,4,5-penta(2-cyanoethoxy)pentane. Detailed Implementation

[0031] The technical solution and implementation process of the present invention will be further explained below with reference to embodiments and comparative examples. 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 use, 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.

[0032] In this invention, the structural formula of 1,2,3,4,5-penta(2-cyanoethoxy)pentane is as follows:

[0033]

[0034] The preparation method of 1,2,3,4,5-penta(2-cyanoethoxy)pentane is as follows: 152g of xylitol and 6.8g of sodium ethoxide are mixed and heated to 90℃ and stirred for 2 hours. Then, 477g of acrylonitrile is slowly added dropwise and stirred. The mixture is reacted for 12 hours. After cooling to room temperature, 6000g of ethanol is added and stirred until homogeneous. The mixture is filtered to obtain the filter residue. The filter residue is purified by recrystallization from ethyl acetate and n-hexane to obtain the final product with a purity >99%. See the NMR spectrum for details. Figure 1 and Figure 2 .

[0035] Unless otherwise specified, the raw materials used in the following embodiments and comparative examples in this invention are all commercially available products.

[0036] In the following examples and comparative examples, DEC stands for diethyl carbonate, EC stands for ethylene carbonate, PC stands for propylene carbonate, EP stands for ethyl propionate, PP stands for propyl propionate, and DFEA stands for 2,2-difluoroethyl acetate.

[0037] Example 1:

[0038] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.1wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0039] Example 2:

[0040] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.3wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0041] Example 3:

[0042] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.5wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0043] Example 4:

[0044] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 1wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0045] Example 5:

[0046] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 1wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0047] Example 6:

[0048] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 3wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0049] Example 7:

[0050] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 5wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0051] Example 8:

[0052] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 7wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0053] Example 9:

[0054] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 2wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0055] Example 10:

[0056] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 6wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0057] Example 11:

[0058] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 8wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0059] Example 12:

[0060] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 10wt% fluoroethylene carbonate, 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0061] Example 13:

[0062] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 5 wt% fluoroethylene carbonate, 1 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 3 wt% succinate were added to the electrolyte to prepare the electrolyte.

[0063] Example 14:

[0064] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 5 wt% fluoroethylene carbonate, 1 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 2 wt% succinate were added to the electrolyte to prepare the electrolyte.

[0065] Example 15:

[0066] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 5 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0067] Example 16:

[0068] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, DFEA and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 5wt% fluoroethylene carbonate, 3wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2wt% triargyl propargyl borate and 0.3wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0069] Comparative Example 1:

[0070] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was then added to the mixed solution to prepare the electrolyte.

[0071] Comparative Example 2:

[0072] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution, and then 5wt% fluoroethylene carbonate and 2wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane were added to the electrolyte to obtain the electrolyte solution.

[0073] Comparative Example 3:

[0074] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution, and then 2wt% of 1,2,3,4,5-penta(2-cyanoethoxy)pentane and 0.2wt% of triargyl propyl borate were added to the electrolyte to prepare the electrolyte.

[0075] Comparative Example 4:

[0076] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution, and then 5wt% fluoroethylene carbonate and 0.2wt% triargyl borate were added to the electrolyte to obtain the electrolyte solution.

[0077] The electrolytes of Examples 1 to 16 and Comparative Examples 1 to 4 were tested for performance in a 4.55V lithium cobalt oxide graphite battery. The positive electrode active material of the lithium cobalt oxide graphite battery was lithium cobalt oxide, the negative electrode active material was artificial graphite, and the separator was a polypropylene / polyethylene / polypropylene composite membrane (PP / PE / PP composite membrane). The electrolyte, positive electrode, negative electrode and separator were assembled into a lithium cobalt oxide graphite battery. The assembly method refers to the prior art. This invention does not impose specific limitations.

[0078] Performance testing:

[0079] (1) Capacity retention rate and battery swelling rate after being placed at 85℃ for 4 hours

[0080] The aforementioned 4.55V lithium cobalt oxide graphite batteries were charged to 4.55V at 1C under constant current / constant voltage (CC / CV) conditions at 25℃, then placed in an oven at 85℃ for 4 hours, and subsequently discharged to 3.0V at 1C. The capacity and battery thickness after 4 hours of high-temperature storage at 85℃ were tested. The capacity and battery thickness of the batteries after charging under the same conditions, without high-temperature storage, and then discharging under the same conditions were also tested. Specifically, the capacity retention rate after 4 hours of high-temperature storage at 85℃ is equal to the capacity after 4 hours of high-temperature storage divided by the capacity without high-temperature storage; the battery swelling rate after 4 hours of high-temperature storage at 85℃ is equal to the difference between the battery thickness after storage and the battery thickness before storage divided by the battery thickness before storage.

[0081] (2) Capacity retention rate after 200 cycles at 45℃

[0082] Under constant current / constant voltage (CC / CV) conditions at 45℃, the battery was charged to 4.55V at 1C and then discharged to 3.0V at 1C. This charge-discharge cycle was repeated for 200 cycles. The battery capacity after the first charge-discharge cycle and after 200 cycles were tested respectively. The 45℃ 200-cycle capacity retention rate is equal to the battery capacity after 200 cycles divided by the battery capacity after the first charge-discharge cycle.

[0083] (3) DCR of 50% SCO and 2C10s

[0084] The voltage difference to current ratio of the 4.55V lithium cobalt oxide graphite battery under 50% SCO charge and 2C constant current discharge for 10s were tested respectively.

[0085] The performance test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] Table 1 shows that the combined use of fluoroethylene carbonate, 1,2,3,4,5-penta(2-cyanoethoxy)pentane, and triargyl borate as additives not only improves the capacity retention and high-temperature cycle performance of 4.55V lithium cobalt oxide graphite batteries after high-temperature storage, but also effectively suppresses the swelling of lithium cobalt oxide graphite batteries under high-temperature conditions, thus improving the stability of lithium cobalt oxide graphite batteries. Furthermore, combining the above three additives with appropriate amounts of other conventional additives can further improve the performance of lithium cobalt oxide graphite batteries to a certain extent.

[0089] Example 17:

[0090] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 2 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0091] Example 18:

[0092] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 4 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0093] Example 19:

[0094] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 6 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0095] Example 20:

[0096] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 8 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0097] Example 21:

[0098] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 10 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3 wt% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0099] Example 22:

[0100] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 12 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl propargyl borate, and 0.3% lithium difluorooxalate borate were added to the electrolyte to prepare the electrolyte.

[0101] Example 23:

[0102] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2mol / L LiPF6 was added to the mixed solution. Then, 10wt% fluoroethylene carbonate, 3wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2wt% triargyl borate, and 0.3wt% lithium difluorobis(oxalate)phosphate were added to the electrolyte to prepare the electrolyte.

[0103] Example 24:

[0104] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 10 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl borate, and 0.2 wt% 4,5-dicyano-2-trifluoromethylimidazolium lithium were added to the electrolyte to prepare the electrolyte.

[0105] Example 25:

[0106] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 10 wt% fluoroethylene carbonate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, 0.2 wt% triargyl borate, and 0.5 wt% lithium fluorosulfonate were added to the electrolyte to prepare the electrolyte.

[0107] Comparative Example 5:

[0108] In an argon-filled glove box (H2O content <10ppm), DEC, EC, PC, EP, and PP were mixed uniformly in a volume ratio of 1:2:1:3:3. 1.2 mol / L LiPF6 was added to the mixed solution. Then, 0.3 wt% lithium difluorooxalate borate, 3 wt% 1,2,3,4,5-penta(2-cyanoethoxy)pentane, and 0.2 wt% triargyl borate were added to the electrolyte to prepare the electrolyte.

[0109] The electrolytes of Examples 17 to 25 and Comparative Example 5 were tested for performance in a 4.55V lithium cobalt oxide silicon-oxygen carbon battery. The positive electrode active material of the lithium cobalt oxide silicon-oxygen carbon battery was lithium cobalt oxide, the negative electrode active material was silicon-oxygen carbon, the capacity was 450mAh / g, and the separator was a polypropylene / polyethylene / polypropylene composite membrane (PP / PE / PP composite membrane). The electrolyte, positive electrode, negative electrode and separator were assembled into a lithium cobalt oxide silicon-oxygen carbon battery. The assembly method refers to the prior art. The present invention does not impose specific limitations.

[0110] Performance tests included: capacity retention rate after 4 hours of high-temperature storage at 85℃ and battery swelling rate; capacity retention rate after 200 cycles at 45℃; and DCR at 50% SCO and 2C10s. The test methods are described above and will not be repeated here. The test results are shown in Table 2.

[0111] Table 2

[0112]

[0113]

[0114] Table 2 shows that in a 4.55V lithium cobalt oxide silicon-oxygen carbon battery, the combination of fluoroethylene carbonate, 1,2,3,4,5-penta(2-cyanoethoxy)pentane, and triargyl borate can also improve the capacity retention after high-temperature storage, as well as the high-temperature cycle performance, enhance the stability of the lithium cobalt oxide silicon-oxygen carbon battery, and suppress the swelling of the lithium cobalt oxide silicon-oxygen carbon battery under high-temperature conditions. Furthermore, combining the above three additives with appropriate amounts of other conventional additives can further improve the performance of the lithium cobalt oxide silicon-oxygen carbon battery to a certain extent.

[0115] As can be seen from Tables 1 and 2, the electrolyte with fluoroethylene carbonate, 1,2,3,4,5-penta(2-cyanoethoxy)pentane and triargyl borate as additives is suitable for high-voltage, high-specific-energy lithium-ion secondary batteries, taking into account the high-temperature, room-temperature and rate performance of high-voltage lithium-ion batteries.

[0116] 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 high-voltage non-aqueous electrolyte, comprising an organic solvent, an electrolyte lithium salt, and additives, characterized in that: The additives include triargyl borate, fluoroethylene carbonate, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane. The mass percentage of the triargyl borate propylidene in the high-voltage non-aqueous electrolyte is 0.1% to 1%. The fluoroethylene carbonate has a mass percentage of 0.1% to 10% in the high-voltage non-aqueous electrolyte. The mass percentage of 1,2,3,4,5-penta(2-cyanoethoxy)pentane in the high-voltage non-aqueous electrolyte is 0.1% to 5%.

2. The high-voltage non-aqueous electrolyte according to claim 1, characterized in that: The additives also include other additives, such as vinylene carbonate, ethylene ethylene carbonate, 1,3-propane sulpholactone, 1,3-(1-propene) sulpholactone, methanedisulfonate, tris(trimethylsilane)borate, tris(trimethylsilane)phosphate, methyl cis-butene anhydride, succinic anhydride, biphenyl, cyclohexylbenzene, trioctyl phosphate, fluoroethylene carbonate, succinic anhydride, adiponitrile, 1,3,6-hexanetrionitrile, 1,2- One or more of the following: di(2-cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,2,3-tris(2-cyanoethoxy)propane, sebaonitrile, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium hexafluoroarsenate, anhydrous lithium perchlorate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium difluorobis(oxalate)phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazolium, and lithium fluorosulfonate.

3. The high-voltage non-aqueous electrolyte according to claim 2, characterized in that: The other additives are present in the high-voltage non-aqueous electrolyte at a mass percentage of 0.1% to 8%.

4. The high-voltage 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 are one or more of γ-butyrolactone, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and the chain esters are 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 high-voltage non-aqueous electrolyte according to claim 1, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, anhydrous lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium 4,5-dicyano-2-trifluoromethylimidazolium, and lithium fluorosulfonate; and / or, the concentration of the lithium salt in the high-voltage non-aqueous electrolyte is 0.8~3 mol / L.

6. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that: The electrolyte is the high-voltage non-aqueous electrolyte according to any one of claims 1 to 5.

7. The lithium-ion battery according to claim 6, characterized in that: The lithium-ion battery has a voltage higher than 4.5V; and / or the lithium-ion battery is an LCO system lithium-ion battery.

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