Additive for lithium ion battery electrolyte, electrolyte and lithium ion battery

Abstract

The application provides a lithium ion battery electrolyte additive, an electrolyte and a lithium ion battery, which comprise a first additive and a second additive. m H n X p COOLi, wherein C m H n X p is at least one of a chain or cyclic alkyl group, a chain or cyclic alkenyl group, a chain or cyclic alkynyl group or an aryl group, X is at least one halogen atom, 0<=n<2m+1, 0 The second additive is a compound with the structure of formula I. Compared with the prior art, the additive provided by the application can efficiently capture active oxygen free radicals and oxygen, effectively reduces the side reactions of the product on the negative electrode surface under high temperature and high pressure, protects the electrode material from oxidation, and thus effectively improves the high-temperature cycle performance, storage performance and safety performance of the lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium batteries, in particular to an additive for lithium ion battery electrolyte, an electrolyte and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are widely used in intelligent wear, computers, smart phones and electric vehicles due to their high energy density, long cycle life, high working voltage and low self-discharge rate. As the "blood vessels" of lithium ion batteries, electrolyte is one of the important raw materials of lithium ion batteries, responsible for the transmission between the positive and negative electrodes, and plays a crucial role in the performance of lithium ion batteries. The solvents, lithium salts and additives contained in the electrolyte have important effects on the low temperature, cycle, storage and safety performance of lithium ion batteries. However, the current electrolyte cannot effectively improve the side reaction on the electrode surface under high voltage, which brings great challenges to the cycle performance and storage performance of lithium ion batteries, and seriously restricts the development of lithium ion batteries under high voltage.

[0003] Therefore, it is necessary to provide a technical solution to solve the above problems. SUMMARY

[0004] One of the purposes of the present application is to solve the problem that the current electrolyte cannot improve the serious side reaction on the electrode surface under high temperature and high pressure by reducing the side reaction on the electrode surface under high temperature and high pressure, thereby effectively improving the high temperature cycle life and storage capacity of lithium ion batteries.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] An additive for lithium ion battery electrolyte, comprising a first additive and a second additive; the structure of the first additive is C m H n X p COOLi, wherein C m H n X p is at least one of chain or cyclic alkyl, chain or cyclic alkenyl, chain or cyclic alkynyl, aryl, X is at least one halogen atom, 0≤n<2m+1, 0<p≤2m+1, 4≤m≤18, p / (p+n)≥20%, m, n, p∈N; the second additive is a compound with the structure of formula I,

[0007]

[0008] wherein R1 to R5 are each independently selected from at least one of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 1 to 10 carbon atoms, an alkynyl group having 1 to 10 carbon atoms, an aryl group, a halogenated group, an amine group, a nitro group, and a sulfo group.

[0009] Preferably, the first additive further satisfies the condition that n < p.

[0010] Preferably, the first additive further satisfies the condition that 0 ≤ n < m and 6 ≤ m ≤ 18.

[0011] Preferably, the first additive is at least one of the following structural formulas:

[0012]

[0013]

[0014] Preferably, the second additive is at least one of the following structural formulas:

[0015]

[0016] Preferably, the additive further comprises a third additive, which is at least one of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, ethylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetristitnile, 1,2,3-tris(2-cyanoethoxyl)propane, propene sultone, methanedisulfonate methylene, ethylene glycol bis(propionitrile) ether.

[0017] The second object of the present application is to provide an electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive is any one of the additives for lithium ion battery electrolyte described above.

[0018] Preferably, the mass of the first additive is 0.1 to 10 wt% of the total mass of the electrolyte; the mass of the second additive is 0.1 to 10 wt% of the total mass of the electrolyte; and the mass of the third additive is 0.5 to 20 wt% of the total mass of the electrolyte.

[0019] Preferably, the lithium salt is at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium tetrafluorophosphate, lithium oxalate phosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide, and the mass of the lithium salt is 8 to 20 wt% of the total mass of the electrolyte; the organic solvent comprises one or more of vinyl carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate, and γ-butyrolactone, and the mass of the organic solvent is 50 to 85 wt% of the total mass of the electrolyte.

[0020] The third object of the present application is to provide a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the electrolyte is any one of the electrolytes described above.

[0021] Compared with the prior art, the present application has the beneficial effects that: the additive of the present application comprises a first additive and a second additive, wherein the first additive can form a supramolecular assembly in the electrolyte through hydrogen bonding with the solvent or itself, the supramolecular assembly has high surface energy and enrichment effect, and can preferentially adsorb active oxygen radicals and oxygen generated after the positive material is damaged at high temperature and high pressure, and the second additive can also react with the active oxygen radicals and oxygen, under the enrichment effect of the supramolecular assembly, the two synergistically react with oxygen, thereby effectively reducing the side reactions of the product on the negative electrode surface at high temperature and high pressure, protecting the electrode material from oxidation, and effectively improving the high-temperature cycle performance, storage performance and safety performance of the lithium ion battery. DETAILED DESCRIPTION

[0022] 1. An additive for lithium ion battery electrolyte

[0023] The first aspect of the present application aims to provide an additive for lithium ion battery electrolyte, comprising a first additive and a second additive; the structure of the first additive is C m H n X p COOLi, wherein C m H n X p is at least one of a chain or ring alkyl group, a chain or ring alkenyl group, a chain or ring alkynyl group, and an aryl group, X is at least one halogen atom, 0≤n<2m+1, 0<p≤2m+1, 4≤m≤18, p / (p+n)≥20%, m, n, p∈N; the second additive is a compound of formula I,

[0024]

[0025] wherein R1-R5 are each independently selected from at least one of hydrogen, an alkyl group with a carbon atom number of 1-10, an alkenyl group with a carbon atom number of 1-10, an alkynyl group with a carbon atom number of 1-10, an aryl group, a halogenated group, an amine group, a nitro group, and a sulfo group.

[0026] For the first additive, the supramolecular assembly formed thereby comprises an outer portion and an inner portion, the COOLi structure is dissociated to form COO - , which repel each other through electrostatic forces to form the outer portion of the assembly; the C m H n X pThe structure is as an inner part, which contains more substituted halogen atoms, and can be combined with each other through hydrogen bonds formed between halogen atoms and hydrogen atoms (not limited to C m H n X p The solvent molecules can also participate in the combination), and finally form a supermolecular assembly with a spherical, rod-like or bilayer membrane structure.

[0027] The supermolecular assembly has high surface energy and enrichment effect, and can enrich active oxygen free radicals and oxygen generated after the positive electrode material is damaged and the second additive, and provide a reaction site away from the electrode material. Thus, under the enrichment effect of the supermolecular assembly, the first additive and the second additive of the application can more efficiently react and combine with oxygen, thereby protecting the electrode material from oxidation and improving the high-temperature cycle performance, storage performance and safety performance of the lithium ion battery.

[0028] Specifically, m can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18, n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, etc., and p can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, etc. According to the different carbon atoms of m, the amount of X substitution is selected, and X can be Cl or F. Preferably, X is F substitution, the number of substitutions n < p, and more preferably n = 0 and p is full substitution. The present inventors have found that for the C m H n X p The more the number of carbon atoms and halogen atoms in the structure, the stronger the hydrogen bond combination ability between molecules, and the easier the formation of supermolecular assemblies. The ability to adsorb active oxygen radicals and oxygen under high temperature and high pressure is also stronger, which can more effectively reduce the side reactions of active oxygen radicals and oxygen on the negative electrode surface, thereby improving the cycle performance under high voltage. Preferably, 6 ≤ m ≤ 18, C m H n X p is a chain-like alkyl or aryl group.

[0029] Compared with other halogen-containing compounds or compounds containing fewer halogen atoms and carbon atoms, the first additive of the application can form a supermolecular assembly and synergistically act with the second additive, which can effectively solve the problem of serious side reactions on the electrode surface under high temperature and high pressure.

[0030] In some embodiments, the first additive is at least one of the structural formulas in Table 1.

[0031] Table 1

[0032]

[0033]

[0034] The first additive can be obtained by dissolving the corresponding precursor in a solvent, such as a 1:1 mixture of hexafluoroisopropanol and water, then adding the mixture to an aqueous lithium hydroxide solution at a 1:1 molar ratio, followed by rotary evaporation to remove the solvent and drying. For example, compound A4 is obtained by dissolving perfluorooctanoic acid in a 1:1 mixture of hexafluoroisopropanol and water, then adding the mixture to an aqueous lithium hydroxide solution at a 1:1 molar ratio, followed by rotary evaporation to remove the solvent and drying. Similarly, compound A5 is obtained by dissolving 2,4,6-trifluorobenzoic acid in a 1:1 mixture of hexafluoroisopropanol and water, then adding the mixture to an aqueous lithium hydroxide solution at a 1:1 molar ratio, followed by rotary evaporation to remove the solvent and drying.

[0035] Preferably, the second additive has at least one structural formula listed in Table 2 below.

[0036] Table 2

[0037]

[0038]

[0039] Preferably, the additive further includes a third additive, which is at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), succinic anhydride (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), 1,2,3-tris(2-cyanoxy)propane, propenesulfonate lactone (PST), methanedisulfonate methylene (MMDS), and ethylene glycol bis(propionitrile) ether (EGBE). Preferably, the third additive is at least two of the above additives. Using two or more third additives together with the first and second additives not only enhances the efficacy of the third additive but also further promotes the effects of the first and second additives, thus improving cycle performance, storage performance, and safety performance. Preferably, the third additive is a mixture of 1,3-propanesulfonate lactone (PS), fluoroethylene carbonate (FEC), and 1,2,3-tris(2-cyanoxy)propane.

[0040] 2. Electrolyte

[0041] A second aspect of the present invention aims to provide an electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive is an additive for lithium-ion battery electrolytes as described in any of the preceding claims.

[0042] In some embodiments, the mass of the first additive is 0.1-10 wt% of the total mass of the electrolyte. Specifically, it can be 0.1-0.5 wt%, 0.5-1 wt%, 1-2 wt%, 2-3 wt%, 3-4 wt%, 4-5 wt%, 5-6 wt%, 6-7 wt%, 7-8 wt%, 8-9 wt%, or 9-10 wt% of the total mass of the electrolyte. Preferably, the mass of the first additive is 0.5-5.0 wt% of the total mass of the electrolyte. In the electrolyte, the appropriate amount of the first additive can preferentially capture active oxygen radicals and oxygen generated after the positive electrode material is destroyed under high temperature and high pressure, thereby effectively reducing the side reactions of active oxygen radicals and oxygen on the surface of the negative electrode.

[0043] In some embodiments, the mass of the second additive is 0.1-10 wt% of the total mass of the electrolyte. Specifically, it can be 0.1-0.5 wt%, 0.5-1 wt%, 1-2 wt%, 2-3 wt%, 3-4 wt%, 4-5 wt%, 5-6 wt%, 6-7 wt%, 7-8 wt%, 8-9 wt%, or 9-10 wt% of the total mass of the electrolyte. Preferably, the mass of the second additive is 0.5-3.0 wt% of the total mass of the electrolyte. In the case of adding an appropriate amount of the first additive, the second additive is also added in an appropriate amount, and the synergistic effect of the two can effectively capture the generated oxygen, effectively reduce the side reactions of the active material under high temperature and high pressure, and improve the cycle performance, storage performance, and safety performance of the lithium ion battery under high temperature and high pressure.

[0044] In some embodiments, the mass of the third additive is 0.5-20 wt% of the total mass of the electrolyte. Preferably, the mass of the third additive is 5-13 wt% of the total mass of the electrolyte, specifically 5-6 wt%, 6-7 wt%, 7-8 wt%, 8-9 wt%, 9-10 wt%, 10-11 wt%, 11-12 wt%, or 12-13 wt%. More preferably, the mass of the third additive is 5-10 wt% of the total mass of the electrolyte.

[0045] In some embodiments, the lithium salt is at least one of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPF2O2), lithium difluorobisoxalate phosphate (LiPF2(C2O4)2), lithium tetrafluoroxalate phosphate (LiPF4C2O4), lithium oxalate phosphate (LiPO2C2O4), lithium bisoxalate borate (LiBOB), lithium difluoroxalate borate (LiODFB), lithium tetrafluoroborate (LiBF4), lithium bis-trifluoromethanesulfonimide (LiTFSI), and lithium bisfluorosulfonimide (LiFSI). The mass of the lithium salt is 8-20 wt% of the total mass of the electrolyte.

[0046] In some embodiments, the organic solvent comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl propionate (EP), propyl propionate (PP), ethyl acetate (EA), ethyl n-butyrate (EB), and gamma-butyrolactone (GBL); the mass of the organic solvent is 50-85 wt% of the total mass of the electrolyte.

[0047] 3. A lithium ion battery

[0048] The third aspect of the present application aims to provide a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the electrolyte is any one of the electrolytes described above. Compared with other conventional electrolyte additives, the electrolyte of the present application is particularly suitable for use at high voltage and high temperature of 4.4-4.5 V due to the addition of the first and second additives.

[0049] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode active material can be one or more of a combination of compounds represented by the chemical formulae Li a Ni x Co y M z O 2-b N b (wherein 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn, Al, and N is selected from one or more combinations of F, P, and S), and the positive electrode active material can also be one or more of LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5LiCoP04, LiMnP04, LiFeP04, LiNiP04, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. The positive active material can also be modified, and the method for modifying the positive active material is known to those skilled in the art, for example, the positive active material can be modified by coating, doping, etc., and the material used for modification can be one or more combinations of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc.

[0050] The negative electrode sheet includes a negative current collector and a negative active material layer coated on the negative current collector, and the negative active material layer includes a negative active material, a negative conductive agent, and a negative binder. The negative active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbead, silicon-based material, tin-based material, lithium titanate, or other metal capable of forming an alloy with lithium, etc. Among them, the graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon alloy; the tin-based material can be selected from one or more of elemental tin, tin oxide compound, tin alloy. The negative current collector is generally a structure or part for collecting current, and the negative current collector can be various materials suitable for use as a negative current collector of a lithium ion battery in the art, for example, the negative current collector can be one or more of metal foil, etc., and more specifically can be one or more of copper foil, etc.

[0051] The separator can be various materials suitable for use as a separator of a lithium ion battery in the art, for example, can be one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber, etc.

[0052] In order to make the technical solutions and advantages of the present application clearer, the following will combine specific embodiments to further describe the present application and its beneficial effects in detail, but the embodiments of the present application are not limited thereto.

[0053] Example 1

[0054] A lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the positive electrode sheet uses LiCoO2 as a positive electrode active material, the negative electrode sheet uses graphite as a negative electrode active material, and the separator is a polypropylene separator.

[0055] Preparation of the electrolyte: in an argon-filled glove box, the water content is <5 ppm, the oxygen content is <5 ppm, ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (DEC), propyl propionate (PP), and ethyl propionate (EP) are mixed according to the mass ratio of EC:PC:DEC:PP:EP = 1:1:1:1:1 to obtain an organic solvent, then 13.7 wt% of lithium hexafluorophosphate (LiPF6) based on the total weight of the electrolyte is slowly added to the organic solvent to obtain a mixture of the organic solvent and the lithium salt, and finally 0.5 wt% of the first additive A4, 0.5 wt% of the second additive B1, 3 wt% of propanesulfonic acid lactone (PS), 3 wt% of fluoroethylene carbonate (FEC), and 3 wt% of 1,2,3-tris(2-cyanoxyl)propane are added, and the mixture is stirred uniformly to obtain the electrolyte of Example 1.

[0056] The preparation method of the first additive A4 is as follows: using a solvent of hexafluoroisopropanol:water = 1:1 to dissolve perfluorooctanoic acid, then adding lithium hydroxide aqueous solution according to a molar ratio of 1:1 to mix, rotary evaporation to remove the solvent and drying to obtain.

[0057] Preparation of the soft package battery: the prepared positive electrode sheet, the separator, and the negative electrode sheet are stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to obtain a bare cell by winding; the bare cell is placed in an aluminum plastic film outer package, vacuum dried at 80℃, and after the moisture meets the standard, the electrolyte prepared above is injected into the dried battery, and the battery is packaged, placed, hot and cold pressed, formed, shaped, and tested to complete the preparation of the lithium ion battery.

[0058] Examples 2-38 and Comparative Examples 1-6 are prepared according to the above preparation method, and the difference is the content of each substance in the electrolyte. The specific substances and contents are shown in Table 3.

[0059] Table 3

[0060]

[0061]

[0062]

[0063] Performance test

[0064] The lithium ion batteries and their electrolytes obtained in Examples 1-38 and Comparative Examples 1-6 are tested for relevant performance.

[0065] (1) Cycle performance test of lithium ion battery

[0066] The lithium ion battery was placed in a 45°C constant temperature room for 30 minutes to make the lithium ion battery reach constant temperature. The lithium ion battery reaching constant temperature was charged at 0.5C constant current to 4.4V, then charged at 4.4V pressure to 0.05C current, and then discharged at 0.5C constant current to 3.0V, which was one charge-discharge cycle. The charging and discharging were repeated in this way, and the capacity retention rate of the lithium ion battery after 500 cycles was calculated respectively.

[0067] (2) Overcharge test

[0068] The 3PCS battery was placed in an explosion-proof box, and the lithium ion battery was charged at 3.0C constant current to 4.6V, and then charged at constant voltage for 7h, and passed if it did not catch fire or explode.

[0069] (3) Short circuit test

[0070] The lithium ion battery was charged at 0.5C constant current to 4.4V, and then charged at constant voltage to 0.05C current to full charge state. The 3PCS battery was placed in an explosion-proof oven, and the positive and negative electrodes of the battery were short-circuited with an 80mΩ resistance wire for 24h, and passed if it did not catch fire or explode.

[0071] The test results are shown in Table 4 below.

[0072] Table 4

[0073]

[0074]

[0075]

[0076] From the test results of Examples 1-20 and Comparative Examples 1-6 above, it can be seen that after adding the first additive and the second additive of the present application, the cycle performance and storage performance of the lithium ion battery under high temperature and high pressure can be effectively improved. Under the same conditions of the second additive, especially the first additive with A4 structure, the number of carbon atoms and halogen atoms contained therein are both more, the hydrogen bond combination ability between molecules is stronger, it is easier to form supramolecular assemblies, and the surface energy of the formed supramolecular assemblies is larger, which can more effectively adsorb active oxygen free radicals and oxygen under high temperature and high pressure to reduce the side reactions of active oxygen free radicals and oxygen on the negative electrode surface, thereby improving the cycle performance and storage performance under high temperature and high pressure. Under the same conditions of the first additive, especially the second additive with B2 structure is more prone to synergistic effect with the first additive, which is mainly because both of them contain halogen atoms, and the compatibility is better, the enrichment effect of the first additive on the second additive is also better, and then the second additive can also react and combine with oxygen more efficiently.

[0077] In addition, from the comparison of Examples 1-16, it can be seen that when the content of the second additive remains unchanged, with the increase of the content of the first additive, the effect of inhibiting high-temperature expansion is more significant, and the safety test effect of overcharge and short circuit is also better, but excessive first additive will also adversely affect the high-temperature cycle performance. In addition, from the comparison of Examples 1-38, it can be seen that the use of more than two first additives compared to the addition of only one first additive is better for improving the high-temperature cycle performance and safety performance of lithium ion batteries, especially the use of A4 in combination with other first additives. In particular, when the third additive is 1wt% of propane sulfone (PS), 5wt% of fluoroethylene carbonate (FEC), 3wt% of 1,2,3-tris(2-cyanoxyl)propane, and two first additives, second additives are mixed for use, the synergistic effect between the additives can significantly improve the cycle performance under high temperature and high pressure, which can be seen from the comparison of Examples 24-38 above.

[0078] In summary, the first additive, the second additive and the third additive are used as additives for lithium ion electrolyte, which can efficiently capture active oxygen free radicals and oxygen, effectively reduce the side reactions of the product on the negative electrode surface under high temperature and high pressure, protect the electrode material from oxidation, thereby effectively improving the high-temperature cycle performance and storage performance of lithium ion batteries and safety performance.

[0079] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art based on the present application shall fall within the scope of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.

Claims

1. An additive for lithium ion battery electrolyte, characterized by comprising: comprising a first additive and a second additive; the structure of the first additive is C m H n X p COOLi or wherein C m H n X p is at least one of a chain or cyclic alkyl group, a chain or cyclic alkenyl group, a chain or cyclic alkynyl group, an aryl group, X is at least one halogen atom, 0n<2m+1, 0 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, 4m+1, The second additive is a compound of formula I, wherein R1-R5 are each independently selected from at least one of hydrogen, an alkyl group having a carbon atom number of 1-10, an alkenyl group having a carbon atom number of 1-10, an alkynyl group having a carbon atom number of 1-10, an aryl group, a halogenated group, an amine group, a nitro group, and a sulfo group.

2. The additive for lithium ion battery electrolyte according to claim 1, characterized by, The first additive further satisfies the condition that n < p.

3. The additive for lithium ion battery electrolyte according to claim 2, characterized by The first additive further satisfies the condition that 0 ≤ n < m and 6 ≤ m ≤ 18.

4. The additive for lithium ion battery electrolyte according to claim 1, characterized by, The first additive is at least one of the following structural formulas:

5. The additive for lithium ion battery electrolyte according to claim 1, characterized by, The second additive is at least one of the following structural formulas:

6. The additive for lithium ion battery electrolyte according to claim 1, characterized by, A third additive is further included, and the third additive is at least one of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, ethylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanato)propane, propene sultone, methane disulfite, and ethylene glycol bis(propionitrile) ether.

7. An electrolyte, characterized by The lithium ion battery electrolyte includes a lithium salt, an organic solvent, and an additive, and the additive is the additive for lithium ion battery electrolyte according to any one of claims 1-6.

8. The electrolyte according to claim 7, characterized in that The mass of the first additive is 0.1-10 wt% of the total mass of the electrolyte; the mass of the second additive is 0.1-10 wt% of the total mass of the electrolyte; and the mass of the third additive is 0.5-20 wt% of the total mass of the electrolyte.

9. The electrolyte of claim 7, wherein, The lithium salt is at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium oxalate phosphate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bistrifluoromethanesulfonylimide, and lithium bisfluorosulfonylimide, and the mass of the lithium salt is 8-20 wt% of the total mass of the electrolyte; the organic solvent includes one or more of vinyl carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate, and γ-butyrolactone, and the mass of the organic solvent is 50-85 wt% of the total mass of the electrolyte.

10. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, characterized by, The electrolyte is the electrolyte according to any one of claims 7-9. The electrolyte is the electrolyte according to any one of claims 7-9.

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