Non-aqueous electrolyte and lithium ion battery

Abstract

In order to overcome the technical problem that the existing lithium ion battery is difficult to balance high-temperature cycle and low-temperature performance, the application provides a non-aqueous electrolyte and a lithium ion battery, the non-aqueous electrolyte comprises a lithium salt, a non-aqueous organic solvent and an additive, the lithium salt comprises lithium hexafluorophosphate, the non-aqueous organic solvent comprises ethylene carbonate, and the additive comprises an additive A shown in a structural formula I and an additive B shown in a structural formula II; the non-aqueous electrolyte satisfies the following conditions: a+b≤1.3, d / b≤3000 and 0.1≤a≤1.3, 0.01≤b≤0.5 and 10≤d≤40; a is the mass percentage content of the additive A in the non-aqueous electrolyte, and the unit is %; b is the mass percentage content of the additive B in the non-aqueous electrolyte, and the unit is %; and d is the mass percentage content of ethylene carbonate in the non-aqueous organic solvent, and the unit is %. The non-aqueous electrolyte provided by the application satisfies the above relationship, and the battery has relatively high high-temperature performance and relatively good low-temperature performance.

Description

Technical Field

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

[0002] The high energy density, long cycle life, and environmental friendliness of lithium-ion batteries have led to their significant development in the field of portable electronic products. Simultaneously, with the development of new energy vehicles, lithium-ion batteries are showing increasing application prospects in the power supply systems of these vehicles. In currently widely used lithium-ion batteries, the non-aqueous electrolyte is a key factor affecting the battery's high and low temperature performance, with additives in the non-aqueous electrolyte being particularly important for maximizing this performance. The solid electrolyte interphase (SEI) film on the surface of the negative electrode of a lithium-ion battery forms during the initial charging process. This interphase film prevents further decomposition of the electrolyte on the carbon negative electrode surface and acts as a lithium-ion tunnel, allowing only lithium ions to pass through. Therefore, the SEI film, to a certain extent, determines the performance of a lithium-ion battery, and additives in the non-aqueous electrolyte influence the formation of the SEI film at the negative electrode interface.

[0003] To improve the performance of lithium-ion batteries, many researchers have added various additives to the electrolyte to improve the quality of the SEI film, thereby enhancing battery performance. However, current research in this area is still immature. The fundamental issue is that additives or combinations of additives rarely achieve the same balance between high-temperature and low-temperature performance. For example, adding isocyanate additives to existing non-aqueous electrolytes improves high-temperature performance. However, the uneven charge distribution of the -NCO functional groups, coupled with the high electron cloud density of nitrogen and oxygen atoms resulting in strong negative charge, helps improve high-temperature cycling performance. Simultaneously, the reduced electron cloud density of carbon atoms makes them more susceptible to forming a nitrogen-containing interfacial layer in the electrolyte, leading to deterioration of low-temperature electrochemical performance and reduced low-temperature battery performance. Therefore, it is impossible to simultaneously achieve both high-temperature cycling and low-temperature performance. Summary of the Invention

[0004] To address the technical problem that existing lithium-ion batteries struggle to balance high-temperature cycling and low-temperature performance, this application provides a non-aqueous electrolyte and a lithium-ion battery.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] This invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and additives. The lithium salt comprises lithium hexafluorophosphate, the non-aqueous organic solvent comprises ethylene carbonate, and the additives comprise additive A represented by structural formula I and additive B represented by structural formula II.

[0007]

[0008] R1 is selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted aromatic, five-membered to seven-membered cycloalkyl, and a bridged ring group formed by at least two cycloalkyl groups selected from five-membered cycloalkyl, six-membered cycloalkyl, and seven-membered cycloalkyl.

[0009]

[0010] Wherein, R2, R3, and R4 are each independently selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted C1-C10 alkynyl, halogen-substituted or unsubstituted aromatic, halogen-substituted or unsubstituted C1-C10 cyano, halogen-substituted or unsubstituted C1-C10 carbonyl, -SiF3, halogen-substituted or unsubstituted -Si(C n H 2n+1 )3, where n is 1 to 3;

[0011] The non-aqueous electrolyte meets the following conditions:

[0012] a+b≤1.3, d / b≤3000 and 0.1≤a≤1.3, 0.01≤b≤0.5, 10≤d≤40;

[0013] Where a is the mass percentage of additive A in the non-aqueous electrolyte, in %;

[0014] b represents the mass percentage of additive B in the non-aqueous electrolyte, in %;

[0015] d represents the mass percentage of ethylene carbonate in the non-aqueous organic solvent, expressed as %.

[0016] Preferably, the non-aqueous electrolyte meets the following conditions:

[0017] a+b≤0.85;

[0018] d / b≤1500.

[0019] Preferably, the mass percentage a% of additive A in the non-aqueous electrolyte satisfies 0.1 ≤ a ≤ 0.5.

[0020] Preferably, the mass percentage b% of additive B in the non-aqueous electrolyte satisfies 0.03 ≤ b ≤ 0.1.

[0021] Preferably, the mass percentage d% of ethylene carbonate in the non-aqueous organic solvent satisfies 20 ≤ d ≤ 35.

[0022] Preferably, additive A is selected from at least one of the following compounds:

[0023]

[0024] Preferably, the additive B is selected from at least one of the following compounds:

[0025]

[0026]

[0027] Preferably, the lithium salt further includes LiPO2F2, LiBF4, LiBOB, LiSbF6, LiAsF6, LiCF3SO3, LiDFOB, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiN(SO2F)2, LiCl, LiBr, LiI, LiClO4, and LiB 10 Cl 10 The lithium hexafluorophosphate is selected from at least one of the following: LiAlCl4, lithium chloroborane, lithium lower aliphatic carboxylic acids having 4 or fewer carbon atoms, lithium tetraphenylborate, and lithium imino; the content of the lithium hexafluorophosphate in the non-aqueous electrolyte is 0.2M to 1.3M.

[0028] Preferably, the additive further includes auxiliary additives, which include at least one of sulfonyl lactones, cyclic carbonates, phosphates, borates, and nitrile compounds;

[0029] Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%.

[0030] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, or 1,3-propenesulfonyl lactone.

[0031] The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, or the compound shown in structural formula III:

[0032]

[0033] In structural formula III, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0034] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula IV:

[0035]

[0036] In the structural formula IV, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group;

[0037] The borate ester compound is selected from at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester;

[0038] The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

[0039] On the other hand, this application provides a lithium-ion battery, including a positive electrode, a negative electrode, and the non-aqueous electrolyte described above.

[0040] Beneficial effects:

[0041] The non-aqueous electrolyte provided in this application contains ethylene carbonate in the non-aqueous organic solvent and lithium salt including lithium hexafluorophosphate. Additives A and B are used in combination in the electrolyte. When the mass percentage d of ethylene carbonate, the mass percentage a of additive A, and the mass percentage b of additive B in the electrolyte meet the conditions: a+b≤1.3, d / b≤3000, the electrophilic and nucleophilic centers of additives A and B complex with each other, resulting in excellent synergistic effects that effectively improve the battery's low-temperature discharge capacity at -20℃ and high-temperature cycle performance. Ethylene carbonate and additive B simultaneously participate in the formation of the interfacial film during the formation process. The strong nucleophilic ability of additive B effectively reduces battery impedance during the electrolyte formation process. Furthermore, in the presence of ethylene carbonate, additive B effectively reduces the damage to the battery caused by the oxidation reaction of the cathode material to the electrolyte under high voltage. Therefore, the battery possesses high high-temperature cycle performance, low impedance growth rate, and good low-temperature performance. Detailed Implementation

[0042] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] This invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and additives. The lithium salt comprises lithium hexafluorophosphate, the non-aqueous organic solvent comprises ethylene carbonate, and the additives comprise additive A represented by structural formula I and additive B represented by structural formula II.

[0044]

[0045] R1 is selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted aromatic, five-membered to seven-membered cycloalkyl, and a bridged ring group formed by at least two cycloalkyl groups selected from five-membered cycloalkyl, six-membered cycloalkyl, and seven-membered cycloalkyl.

[0046]

[0047] Wherein, R2, R3, and R4 are each independently selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted C1-C10 alkynyl, halogen-substituted or unsubstituted aromatic, halogen-substituted or unsubstituted C1-C10 cyano, halogen-substituted or unsubstituted C1-C10 carbonyl, -SiF3, halogen-substituted or unsubstituted -Si(C n H 2n+1 )3, where n is 1 to 3;

[0048] The non-aqueous electrolyte meets the following conditions:

[0049] a+b≤1.3, d / b≤3000 and 0.1≤a≤1.3, 0.01≤b≤0.5, 10≤d≤40;

[0050] Where a is the mass percentage of additive A in the non-aqueous electrolyte, in %;

[0051] b represents the mass percentage of additive B in the non-aqueous electrolyte, in %;

[0052] d represents the mass percentage of ethylene carbonate in the non-aqueous organic solvent, expressed as %.

[0053] This invention provides a non-aqueous electrolyte. In an electrolyte containing ethylene carbonate as one of the main solvents and lithium hexafluorophosphate as the lithium salt, an additive A with a specific structure is added. Due to the typical -NCO effect in its structure, the charge distribution of the molecule itself is uneven, possessing both nucleophilic and electrophilic centers. The high electron cloud density of nitrogen and oxygen atoms results in strong negative charge, making it easy to react with electrophilic reagents, thereby improving the high-temperature cycle performance of the battery. At the same time, the electron cloud density of carbon atoms decreases, exhibiting strong positive charge and becoming an electrophilic center. In the electrolyte, it is easy to introduce a nitrogen-containing interface layer by participating in the formation of the SEI film, leading to the deterioration of low-temperature electrochemical performance. Additive B, with its unsaturated trivalent phosphorus structure, although its strong nucleophilic ability can effectively reduce battery impedance during electrolyte formation and, in the presence of ethylene carbonate, can effectively reduce the damage to the battery caused by the oxidation reaction of the cathode material to the electrolyte under high voltage, its high reducing activity can easily lead to the deterioration of high-temperature performance. Through extensive research, the inventors discovered that when additives A and B are added to the electrolyte in a non-aqueous organic solvent containing ethylene carbonate, and when additives A and B are used in combination, and the mass percentage d of ethylene carbonate in the non-aqueous organic solvent, the mass percentage a of additive A in the electrolyte, and the mass percentage b of additive B satisfy the conditions: a+b≤1.3, d / b≤3000, the electrophilic and nucleophilic centers of additives A and B complex with each other, resulting in an excellent synergistic effect that effectively improves the battery's low-temperature discharge capacity at -20℃ and high-temperature cycle performance. Ethylene carbonate and additive B simultaneously participate in the formation of the interfacial film during the formation process. The strong nucleophilic ability of additive B effectively reduces battery impedance during electrolyte formation. Furthermore, in the presence of ethylene carbonate, additive B effectively reduces the damage to the battery caused by the oxidation reaction of the cathode material to the electrolyte under high voltage. Therefore, the battery possesses high high-temperature cycle performance, low impedance growth rate, and good low-temperature performance.

[0054] If the total mass percentage (a+b)% of additives A and B in the electrolyte is greater than 1.3%, the synergistic effect of additives A and B is reduced, resulting in poor low-temperature performance of the battery. If d / b is greater than 3000, the improvement effect on reducing battery impedance is minimal.

[0055] Specifically, the content 'a' of additive A and the content 'b' of additive B in the electrolyte satisfy a+b≤1.3. For example, the value of a+b can be 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, etc.

[0056] Specifically, the content of additive B in the electrolyte (b) and the mass percentage of ethylene carbonate in the non-aqueous organic solvent (d) must satisfy d / b ≤ 3000. For example, the value of d / b can be 3000, 2400, 2000, 1500, 1000, 800, 600, 300, 100, 90, 50, 10, etc.

[0057] This application controls the mass percentage (a%) of additive A in the electrolyte to be 0.1 ≤ a ≤ 1.3. If the mass percentage (a) of additive A in the electrolyte is too low, the amount participating in the film-forming reaction is low, affecting the formation of the electrode interface film, resulting in lower high-temperature cycle performance and low-temperature performance of the battery. If the mass percentage (a) of additive A in the electrolyte is too high, it participates in the formation of the SEI film at the interface, introducing an increase in the thickness of the N-containing interface layer, thus degrading the low-temperature performance of the battery. It should be noted that the mass percentage (a%) of additive A in the electrolyte can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.2%, etc., as long as the mass percentage (a%) of additive A is within the range of 0.1 ≤ a ≤ 1.3.

[0058] The mass percentage b% of additive B in the electrolyte is 0.01 ≤ b ≤ 0.5. If the mass percentage b% of additive B is too low, the content of additive B in the electrolyte will be low, resulting in a low content of substances participating in the reaction, which will not effectively improve the high-temperature cycle performance and low-temperature performance of the battery. If the content of additive B is too high, although excessive additive B can reduce the damage to the battery caused by the oxidation reaction of the positive electrode material to the electrolyte under high voltage, excessive additive B will reduce the high-temperature cycle performance of the battery.

[0059] Specifically, the mass percentage b% of additive B in the electrolyte can be 0.01%, 0.05%, 0.07%, 0.08%, 0.1%, 0.14%, 0.16%, 0.20%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, as long as the mass percentage b% of additive B is within the range of 0.01 ≤ b ≤ 0.5.

[0060] It should be noted that in structural formulas I and II, halogen elements include F, Cl, Br, I, etc. Aromatic groups include phenyl, naphthyl, etc. C1-C10 alkyl groups include methyl, ethyl, isobutyl, pentyl, etc. C1-C10 alkenyl groups include vinyl, butenyl, octenyl, etc. Five- to seven-membered cycloalkyl groups can be five-membered, six-membered, or seven-membered rings. Bridged ring groups formed by at least two cycloalkyl groups from five-membered, six-membered, or seven-membered cycloalkyl groups can be two six-membered rings, two five-membered rings, or a bridged ring group formed by one five-membered ring and one six-membered ring. C1-C10 cyano groups can be acetonitrile, butyronitrile, etc.

[0061] In some preferred embodiments, the non-aqueous electrolyte satisfies the following conditions:

[0062] a+b≤0.85;

[0063] d / b≤1500.

[0064] In the preferred embodiments described above, the electrophilic and nucleophilic centers of additives A and B better interact and have a better synergistic effect, resulting in higher high-temperature cycle capacity retention and low-temperature capacity retention, and lower battery impedance.

[0065] In some preferred embodiments, the mass percentage a% of additive A in the non-aqueous electrolyte satisfies 0.1 ≤ a ≤ 0.5.

[0066] In the electrolyte, the mass percentage of additive A is between 0.1% and 0.5%. While improving the high-temperature cycle performance of the battery, additive B works synergistically with additive A to have a smaller impact on the low-temperature degradation of the battery.

[0067] In some preferred embodiments, the mass percentage b% of additive B in the non-aqueous electrolyte satisfies 0.03 ≤ b ≤ 0.1.

[0068] In the electrolyte, the mass percentage of additive B is between 0.03% and 0.1%. While reducing the impact of additive B on the high-temperature performance degradation of the battery, it also helps additive B to work synergistically with additive A to improve the high-temperature capacity retention of the battery.

[0069] In some preferred embodiments, the mass percentage d% of ethylene carbonate in the non-aqueous organic solvent satisfies 20 ≤ d ≤ 35.

[0070] In the electrolyte, the mass percentage (d%) of ethylene carbonate is between 20% and 35%. Controlling additive B effectively reduces the damage to the battery caused by the oxidation reaction of the positive electrode material to the electrolyte under high voltage, and improves the stability of the electrolyte.

[0071] In some preferred embodiments, additive A is selected from at least one of the following compounds:

[0072]

[0073]

[0074] In some preferred embodiments, the additive B is selected from at least one of the following compounds:

[0075]

[0076]

[0077] It should be noted that the selection of compounds for the above-mentioned preferred additives A and B is only a preferred compound of the present invention and does not represent a limitation on the present invention.

[0078] In some preferred embodiments, the lithium salt further includes LiPO2F2, LiBF4, LiBOB, LiSbF6, LiAsF6, LiCF3SO3, LiDFOB, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiN(SO2F)2, LiCl, LiBr, LiI, LiClO4, and LiB 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0079] Under the above conditions, adding LiPF6 as the main lithium salt to the non-aqueous electrolyte, along with the aforementioned auxiliary lithium salts, can improve the stability of the non-aqueous electrolyte and further enhance the high-temperature and low-temperature performance of the battery.

[0080] In some embodiments, the lithium hexafluorophosphate in the non-aqueous electrolyte contains 0.2M to 1.3M.

[0081] In some preferred embodiments, the content of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.5M to 1.2M.

[0082] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, and carboxylic acid ester solvents.

[0083] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ethers may specifically include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ethers may specifically include, but are not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. Ether compounds can be used alone or in any combination and ratio of two or more. There are no particular restrictions on the amount of ether compounds added; it is arbitrary as long as it does not significantly impair the performance of the lithium-ion battery of this invention. Typically, the volume ratio is 1% or more, preferably 2% or more, and more preferably 3% or more, when the non-aqueous solvent volume ratio is 100%. Furthermore, the volume ratio is typically 30% or less, preferably 25% or less, and more preferably 20% or less. When using two or more ether compounds in combination, the total amount of ether compounds should meet the above-mentioned range. When the amount of ether compounds added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity resulting from the increased lithium-ion dissociation degree and reduced viscosity of the chain ethers. Additionally, when the negative electrode active material is a carbon material, the phenomenon of co-intercalation between the chain ethers and lithium ions can be suppressed, thus enabling the input / output characteristics and charge / discharge rate characteristics to reach an appropriate range.

[0084] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0085] In some embodiments, the carbonate solvent includes cyclic carbonates or chain carbonates. Cyclic carbonates may specifically include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); chain carbonates may specifically include, but are not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of cyclic carbonates is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. However, when using only one type, its lower limit relative to the total volume of the non-aqueous electrolyte solvent is typically 3% or more, preferably 5% or more. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less, preferably 85% or less, and more preferably 80% or less. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to enhanced stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus contributing to achieving a favorable range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonate meets the above range.

[0086] In some embodiments, fluorine-containing chain carbonates (hereinafter referred to as "fluorinated chain carbonates") are also preferably used. There is no particular limitation on the number of fluorine atoms in a fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0087] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-lactamactone, and δ-lactamactone. Examples of chain carbonates include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0088] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. There are no particular limitations on the amount of sulfone solvent added, and it is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the amount of sulfone solvent added is within the above range, an electrolyte with excellent high-temperature storage stability is tended to be obtained.

[0089] In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.

[0090] In some embodiments, the additive further includes auxiliary additives, which include at least one of sulfonyl lactones, cyclic carbonates, phosphates, borates, and nitrile compounds.

[0091] Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%.

[0092] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, or 1,3-propenesulfonyl lactone.

[0093] The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, or the compound shown in structural formula III:

[0094]

[0095] In structural formula III, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0096] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula IV:

[0097]

[0098] In the structural formula IV, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group;

[0099] In a preferred embodiment, the unsaturated phosphate compound may be at least one of the following: triargyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0100] The borate ester compound is selected from at least one of tri(trimethylsilane)borate and tri(triethylsilane)borate.

[0101] The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

[0102] In other embodiments, the additive may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates and cyclophosphonitriles, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0103] It should be noted that, unless otherwise specified, generally, the addition amount of any optional substance in the additive in the non-aqueous electrolyte is 10% or less; preferably, the addition amount is 0.1-5%, and more preferably, the addition amount is 0.1% to 2%. Specifically, the addition amount of any optional substance in the additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

[0104] In some embodiments, when the additive is selected from fluoroethylene carbonate, based on the total mass of the non-aqueous electrolyte as 100%, the addition amount of the fluoroethylene carbonate is 0.05% to 30%.

[0105] In another aspect, the present application provides a lithium ion battery comprising a positive electrode, a negative electrode and the above-mentioned non-aqueous electrolyte.

[0106] In some embodiments, the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises LiNi x Co y Mn z L (1-x-y-z) O2, LiCo x＇ L (1-x′) O2, LiNi x＇＇ L' y＇ Mn (2-x＇＇-y＇) O4, Li z＇ MPO4, wherein L is at least one selected from Al, Sr, Mg, Ti, Ca, Zr, Zn, Si and Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x'≤1, 0.3≤x''≤0.6, 0.01≤y'≤0.2, L' is at least one selected from Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si and Fe; 0.5≤z'≤1, and M is at least one selected from Fe, Mn and Co.

[0107] In some embodiments, the positive electrode material layer further comprises a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are co-blended to obtain the positive electrode material layer.

[0108] Based on the total mass of the positive electrode material layer as 100%, the mass percentage of the positive electrode binder is 1-2%, and the mass percentage of the positive electrode conductive agent is 0.5-2%.

[0109] The positive electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylides, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; sodium carboxymethyl cellulose; polyvinyl butyral; ethylene-vinyl acetate copolymer; polyvinyl alcohol; and styrene-butadiene rubber.

[0110] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0111] In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is formed on the surface of the positive electrode current collector.

[0112] The positive current collector is selected from a metallic material that can conduct electrons. Preferably, the positive current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive current collector is selected from aluminum foil.

[0113] In some embodiments, the negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material is selected from at least one of silicon-based negative electrode, carbon-based negative electrode, lithium-based negative electrode and tin-based negative electrode.

[0114] The silicon-based anode includes at least one of silicon material, silicon oxide, silicon-carbon composite material, and silicon alloy material; the carbon-based anode includes at least one of graphite, hard carbon, soft carbon, graphene, and mesophase carbon microspheres; the lithium-based anode includes at least one of metallic lithium or lithium alloy. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy. The tin-based anode includes at least one of tin, tin-carbon, tin-oxygen, and tin metal compounds.

[0115] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0116] The selectable ranges of the negative electrode adhesive and negative electrode conductive agent are the same as those of the positive electrode adhesive and positive electrode conductive agent, and will not be repeated here.

[0117] In some embodiments, the negative electrode sheet further includes a negative electrode current collector, and the negative electrode material layer is formed on the surface of the negative electrode current collector.

[0118] The negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0119] In some embodiments, the diaphragm may be a polymer diaphragm, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP diaphragms.

[0120] In some embodiments, at least one surface of the diaphragm is coated with a surface coating comprising at least one of inorganic particles and organic gels.

[0121] By applying a surface coating, the mechanical strength and puncture resistance of the separator can be effectively improved, thereby enhancing the safety performance of the lithium-ion battery.

[0122] The present invention will be further illustrated by the following examples.

[0123] Example 1

[0124] This embodiment illustrates a method for preparing a non-aqueous electrolyte and lithium-ion battery disclosed in this invention.

[0125] 1) Preparation of non-aqueous electrolyte

[0126] Ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DMC:DEC:EMC = 30:10:20:40. Lithium hexafluorophosphate (LiPF6) was then added to a molar concentration of 1.1 mol / L, followed by additives. The content of each additive, based on 100% of the total weight of the non-aqueous electrolyte, is shown in Table 1.

[0127] 2) Preparation of the positive electrode plate

[0128] The positive electrode active material LiNi was mixed at a mass ratio of 97:1.5:1.5. 0.5 Co 0.2 Mn 0.3O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, dried, calendered, and vacuum dried, and then aluminum leads are welded on using an ultrasonic welder to obtain a positive electrode plate with a thickness of 110-160 μm.

[0129] 3) Preparation of negative electrode plate

[0130] The negative electrode active materials graphite AG, conductive carbon black Super-P, binders styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1.5:3:1.5, and then dispersed in deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of a copper foil, dried, calendered, and vacuum dried, and then nickel leads are welded on using an ultrasonic welder to obtain a negative electrode plate with a thickness of 120-150 μm.

[0131] 4) Cell fabrication

[0132] A separator with a thickness of 20 μm is placed between the positive and negative plates. Then, the sandwich structure consisting of the positive plate, negative plate and separator is wound up. The wound body is then placed in an aluminum foil packaging bag and vacuum baked at 75°C for more than 48 hours to obtain the cell to be injected with electrolyte.

[0133] 5) Electrolyte injection and formation of battery cells

[0134] In a glove box with water and oxygen contents of less than 20 ppm and 50 ppm respectively, the electrolyte prepared above was injected into the battery cell, vacuum sealed, and left at 45°C for 24 hours.

[0135] Then, perform the first charging routine formation as follows: 0.05C constant current charging for 180 min, 0.1C constant current charging for 180 min, 0.2C constant current charging for 120 min, age at 45℃ for 24 h, then vacuum seal again, and then further charge at 0.2C constant current to 4.4V, and discharge at 0.2C constant current to 3V.

[0136] Examples 2-16 and Comparative Examples 1-15

[0137] Examples 2-16 and Comparative Examples 1-15 are used to illustrate the battery and its preparation method disclosed in this invention, including most of the operation steps in Example 1. The difference is that the components and their contents in Examples 2-16 and Comparative Examples 1-15 adopt the electrolyte components shown in Table 1.

[0138] Table 1 Electrolyte parameter data for Examples 1-16 and Comparative Examples 1-15

[0139]

[0140]

[0141] Performance testing

[0142] The lithium-ion batteries prepared in Examples 1-16 and Comparative Examples 1-15 were subjected to the following performance tests: High-temperature cycling performance at 45°C:

[0143] The prepared lithium-ion battery (LiNi) 0.5 Co 0.2 Mn 0.3 The O2 / AG was placed in an oven at a constant temperature of 45°C and charged to 4.4V with a constant current of 1C. Then it was charged with constant current and constant voltage until the current dropped to 0.05C. Then it was discharged to 3.0V with a constant current of 1C. This cycle was repeated 1000 times. The discharge capacity C1 and impedance R1 of the first cycle and the discharge capacity C2 and impedance R2 of the last cycle were recorded.

[0144] Calculate the capacity retention and impedance growth rate during high-temperature cycling using the following formula:

[0145] Capacity retention rate = C2 / C1 × 100%;

[0146] Impedance growth rate = (R2-R1) / R1×100%;

[0147] -20℃ low temperature discharge performance:

[0148] The prepared lithium-ion battery (LiNi) 0.5 Co 0.2 Mn 0.3 The O2 / AG battery was placed in a constant temperature chamber at 25°C and charged at a constant current of 1C to 4.4V. It was then charged at a constant current and constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 1C to 3.0V. The discharge capacity C3 was recorded. The battery was then fully charged again in a constant temperature chamber at 25°C using the same method. The temperature of the chamber and the battery was then lowered to -20°C, and discharged at a constant current of 0.5C to 2.5V. The discharge capacity C4 was recorded.

[0149] Calculate the low-temperature discharge capacity retention rate using the following formula:

[0150] -20℃ discharge capacity retention rate = C4 / C3 × 100%;

[0151] The results obtained from the tests of Examples 1-16 and Comparative Examples 1-15 are filled in Table 2.

[0152] Table 2. Electrical performance test results of Examples 1-16 and Comparative Examples 1-15

[0153]

[0154]

[0155] As shown in Tables 1 and 2, based on the test results of Examples 1-16 and Comparative Examples 1-15, when additives A and B are added to the electrolyte in a non-aqueous organic solvent containing ethylene carbonate, and the mass content of additive A (a), the mass content of additive B (b), and the mass content of ethylene carbonate in the non-aqueous organic solvent (d) meet the preset conditions of a+b≤1.3 and d / b≤3000, the resulting lithium-ion battery exhibits high high-temperature cycle capacity retention, low-temperature discharge capacity retention, and low high-temperature cycle impedance growth rate. This indicates that the electrophilic and nucleophilic centers of additives A and B complex with each other, and their excellent synergistic effect effectively improves the battery's low-temperature discharge capacity and high-temperature cycle performance at -20℃. Ethylene carbonate and additive B simultaneously participate in the formation of the interfacial film during the formation process. The strong nucleophilic ability of additive B can effectively reduce the battery impedance during the electrolyte formation process. Furthermore, in the presence of ethylene carbonate, additive B can effectively reduce the damage to the battery caused by the oxidation reaction of the cathode material to the electrolyte under high voltage. Therefore, the battery possesses high high-temperature cycle performance, low impedance growth rate, and good low-temperature performance.

[0156] The test results from Examples 1-16 show that when the preferred conditions a+b≤0.85 and d / b≤1500 are further met, it is beneficial to further improve the high-temperature cycle capacity retention rate and low-temperature discharge capacity retention rate of lithium-ion batteries. It also has the effect of further reducing the growth rate of high-temperature cycle impedance of lithium-ion batteries. It is speculated that the electrophilic and nucleophilic centers of additive A and additive B can better complex with each other, and the synergistic effect of the two is better, thereby effectively improving the low-temperature discharge capacity and high-temperature cycle performance of the battery, and better reducing the high-temperature cycle impedance of the battery.

[0157] The test results of Comparative Examples 1-4, 7-8, and 11-13 show that even if the mass content of additive A (a), the mass content of additive B (b), and the content of ethylene carbonate (d) in the electrolyte meet the preset conditions of a+b≤1.3 and d / b≤3000, but the values ​​of a, b, or d do not meet these range limits, the high-temperature cycle capacity retention rate and low-temperature capacity retention rate of the lithium-ion battery are low, and the high-temperature cycle impedance growth rate is high. This indicates that the values ​​of a, b, or d have a strong correlation with improving the high-temperature and low-temperature performance of lithium-ion batteries. Similarly, the test results of Comparative Examples 5-6, 9-10, and 14-15 show that when the values ​​of a, b, or d meet their range limits but do not meet the preset conditions of a+b≤1.3 and d / b≤3000, the high-temperature cycle capacity retention rate and low-temperature capacity retention rate of the battery are low, and the high-temperature cycle impedance growth rate of the battery is high.

[0158] The differences between Examples 17-25 and Example 1 are that the compounds used for additive A and additive B are different, and the electrolyte composition is different, as detailed in Table 3. The rest of the preparation steps are the same as in Example 1.

[0159] The battery electrical performance testing methods for the batteries prepared in Examples 17-25 are the same as those for the battery in Example 1. The test results are shown in Table 4.

[0160] Table 3. Parameter data for Examples 1 and 17-25

[0161]

[0162]

[0163] Table 4 Electrical performance data for Examples 1 and 17-25

[0164]

[0165] A comparison of Tables 3 and 4 shows that, based on the test results of Examples 1 and 17-25, for different types of additive A or different types of additive B, when the mass content a of additive A, the mass content b of additive B, and the content d of ethylene carbonate meet the preset conditions a+b≤1.3 and d / b≤3000, their effects are similar. They all have a good effect on improving the high-temperature and low-temperature performance of the battery, thereby improving the high-temperature capacity retention rate, the low-temperature capacity retention rate, and reducing the high-temperature cycle impedance growth rate of the battery. This indicates that the relationship provided by the present invention is applicable to compounds represented by different structural formulas I and II.

[0166] Examples 26-29

[0167] The difference between Examples 26-29 and Example 1 is that the compounds selected for additive A are different, while the compounds selected for additive B are the same, and the types and amounts of auxiliary additives are different, as detailed in Table 5. The rest of the preparation steps are the same as in Example 1.

[0168] The battery electrical performance testing methods for the batteries prepared in Examples 26-29 are the same as those for the battery in Example 1. The test results are shown in Table 6.

[0169] Table 5. Electrolyte parameters for Examples 1 and 26-29.

[0170]

[0171]

[0172] Table 6 Electrical performance data for Examples 1 and 26-29

[0173]

[0174] Tables 5 and 6 show that, compared with Examples 26-29, the addition of auxiliary additives to the electrolyte significantly improved the high-temperature and low-temperature performance of the battery, indicating that additives A, B, and the auxiliary additives have complementary effects. When the auxiliary additive is fluoroethylene carbonate, the battery exhibits a high high-temperature impedance growth rate, suggesting that fluoroethylene carbonate has strong nucleophilicity and participates in the formation of the SEI film together with additive A, increasing the film thickness and thus the battery impedance. When the auxiliary additive is 1,3-propanesulfonate lactone (PS), the battery exhibits a low low-temperature capacity retention rate, suggesting that the high electron cloud density of oxygen atoms in PS results in strong electronegativity, affecting the complexation of additives A and B, weakening the synergistic effect. Additive A is also more likely to introduce an N-containing interfacial layer due to its participation in the formation of the SEI interface, leading to a deterioration in low-temperature electrochemical performance.

[0175] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that, The mixture includes lithium salts, non-aqueous organic solvents, and additives. The lithium salt includes lithium hexafluorophosphate, the non-aqueous organic solvent includes ethylene carbonate, and the additives include additive A (shown as structural formula I) and additive B (shown as structural formula II). R1 is selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted aromatic, five-membered to seven-membered cycloalkyl, and a bridged ring group formed by at least two cycloalkyl groups selected from five-membered cycloalkyl, six-membered cycloalkyl, and seven-membered cycloalkyl. Wherein, R2, R3, and R4 are each independently selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted C1-C10 alkynyl, halogen-substituted or unsubstituted aromatic, halogen-substituted or unsubstituted C1-C10 cyano, halogen-substituted or unsubstituted C1-C10 carbonyl, -SiF3, halogen-substituted or unsubstituted -Si(C n H 2n+1 )3, n is 1 to 3; the non-aqueous electrolyte satisfies the following conditions: a+b≤1.3, d / b≤3000 and 0.1≤a≤1.3, 0.01≤b≤0.5, 10≤d≤40; Wherein, a is the mass percentage of additive A in the non-aqueous electrolyte, in %; b is the mass percentage of additive B in the non-aqueous electrolyte, in %; d represents the mass percentage of ethylene carbonate in the non-aqueous organic solvent, expressed as %.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte meets the following conditions: a+b≤0.85; d / b≤1500.

3. The non-aqueous electrolyte according to claim 1, characterized in that, The mass percentage (a%) of additive A in the non-aqueous electrolyte satisfies 0.1 ≤ a ≤ 0.

5.

4. The non-aqueous electrolyte according to claim 1, characterized in that, The mass percentage b% of additive B in the non-aqueous electrolyte satisfies 0.03 ≤ b ≤ 0.

1.

5. The non-aqueous electrolyte according to claim 1, characterized in that, The mass percentage d% of ethylene carbonate in the non-aqueous organic solvent satisfies 20 ≤ d ≤ 35.

6. The non-aqueous electrolyte according to claim 1, characterized in that, The additive A is selected from at least one of the following compounds:

7. The non-aqueous electrolyte according to claim 1, characterized in that, The additive B is selected from at least one of the following compounds:

8. The non-aqueous electrolyte according to claim 1, characterized in that, The lithium salts also include LiPO2F2, LiBF4, LiBOB, LiSbF6, LiAsF6, LiCF3SO3, LiDFOB, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiN(SO2F)2, LiCl, LiBr, LiI, LiClO4, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino. The content of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.2M to 1.3M.

9. The non-aqueous electrolyte according to claim 1, characterized in that, The additives also include auxiliary additives, which include at least one of sulfonyl lactones, cyclic carbonates, phosphates, borates, and nitrile compounds. Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%. The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, or 1,3-propenesulfonyl lactone. The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, or the compound shown in structural formula III: In structural formula III, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group; The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula IV: In the structural formula IV, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group; The borate ester compound is selected from at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester; The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and the non-aqueous electrolyte as described in any one of claims 1-9.

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