A lithium-ion battery electrolyte and a lithium-ion battery

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically relating to a lithium-ion battery electrolyte and a lithium-ion battery. The lithium-ion battery electrolyte comprises an organic solvent, a lithium salt, and a bisphosphite compound; the bisphosphite compound has the following structure: wherein, A is selected from C. n H 2n‑2 Or C n H 2n‑4 n=2~12; B is selected from halogen atoms or -Si(C) atoms. m H 2m+1 )3, m=1~4. By adding a bisphosphite compound with a specific structure, the high-temperature cycle and storage performance of the battery was improved, gas production was reduced, and DC internal resistance was lowered.

Description

Technical Field

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

[0002] In recent years, with the development of new energy technologies, lithium-ion power batteries for vehicles have placed higher demands on the performance of lithium-ion rechargeable batteries. To meet the requirements of long driving range and wide temperature range environments for electric vehicles, it is necessary to develop lithium-ion rechargeable batteries with higher energy density, superior high-temperature cycle life, and better storage performance to meet the lifespan requirement of over 10 years for automotive power batteries. To improve energy density, using layered oxide cathode materials with high nickel content and increasing their operating voltage has become an important technological direction. However, these cathode materials have poor interfacial stability under high pressure and high temperature conditions, and are prone to continuous oxidation side reactions with the electrolyte, leading to problems such as capacity decay, increased impedance, and gas generation, severely restricting the battery's long cycle life and high-temperature storage performance.

[0003] In related technologies, functional film-forming additives are often added to the electrolyte to improve the stability of the electrode / electrolyte interface. Tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate are commonly used additives. These additives contain silane groups and have good low-temperature performance; however, their synergistic stabilizing effect on the positive and negative electrode interfaces at high temperatures is limited. Furthermore, conventional single-functional additives often focus on forming a protective film on one side of the negative or positive electrode, making it difficult to simultaneously construct a low-impedance and stable solid-state electrolyte interface (SEI) film at both the positive and negative electrode interfaces at high temperatures. Meanwhile, the carbonate-based electrolytes commonly used in commercial lithium-ion batteries are inherently flammable, posing a safety hazard, and conventional interfacial film-forming additives typically do not possess the function of improving the intrinsic safety of the electrolyte.

[0004] Therefore, how to solve the technical problem of unstable positive and negative electrode interfaces at high temperatures in lithium-ion batteries using high-voltage, high-nickel cathode materials through the design of electrolyte additives, while also taking into account the safety performance of the electrolyte, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a lithium-ion battery electrolyte by combining and introducing a bisphosphite compound and a phosphazene compound with specific structures into the electrolyte system. The alkenyl or alkynyl groups of the bisphosphite compound can be reduced on the negative electrode surface during charging to form a stable protective film, thereby improving the battery's high-temperature lifespan. The silane groups can absorb hydrofluoric acid and moisture in the electrolyte, thereby reducing side reactions in the battery and lowering the battery's internal resistance. Furthermore, the phosphite group (-PO-) of the compound of the present invention can form a low-resistance protective film on the positive electrode surface, suppressing side reactions between the positive electrode and the electrolyte and improving high-temperature performance.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, a lithium-ion battery electrolyte is provided, comprising an organic solvent, a lithium salt, and a bisphosphite compound; The bisphosphite compound has the structure shown in Formula I: Formula 1 Wherein, A is selected from C. n H 2n-2 Or C n H 2n-4 n=2~12; B is selected from halogen atoms or -Si(C) m H 2m+1 )3, m=1~4.

[0007] By combining and introducing bisphosphite compounds and phosphazene compounds with specific structures into the electrolyte system, the bisphosphite compounds can participate in the reaction at the positive and negative electrode interfaces to form a stable solid electrolyte interphase (SEI) film, effectively suppressing the side reactions between the electrode materials and the electrolyte at high temperatures. This significantly improves the high-temperature storage and cycle performance of the battery, and reduces the gas generation rate and DC internal resistance. At the same time, the phosphazene compounds, as flame retardant components, can decompose to produce free radical quenchers when the electrolyte is heated or burned, interrupting the combustion chain reaction. This greatly improves the self-extinguishing ability of the electrolyte and enhances the safety of the battery system. Thus, the technical effect of simultaneously achieving high-temperature long life and high safety in a single electrolyte formulation is achieved.

[0008] In some of these embodiments, the bisphosphite compound is selected from at least one of 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite).

[0009] The relevant structures of the bisphosphite compound are as follows: 2-Butene-1,4-bis(difluorophosphite) 2-Butyn-1,4-bis(difluorophosphite) 2-Butene-1,4-bis(di(trimethylsilyl)phosphite) 2-Butyn-1,4-bis(di(trimethylsilyl)phosphite) By limiting the bisphosphite compounds to at least one selected from 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite), these specific compounds possess clearly defined alkenyl / alkynyl groups and substituents with strong electron-withdrawing or passivating effects. The alkenyl / alkynyl groups are more readily reduced to form a film on the negative electrode surface, while the difluorophosphite or trimethylsilyl phosphite groups help form a low-resistance protective film on the positive electrode surface and remove harmful HF, thereby synergistically achieving superior interface stability. This further optimizes the battery's performance in terms of high-temperature storage capacity retention, cycle performance, and gas generation suppression.

[0010] In some embodiments, the lithium-ion battery electrolyte further includes a second additive, which includes phosphazene compounds.

[0011] In some of these embodiments, the phosphazene compound is a cyclic phosphazene compound.

[0012] In some of these embodiments, the cyclic phosphazene compound has a six-membered cyclic phosphazene structure.

[0013] In some of these embodiments, the phosphazene compound has the structure shown in Formula 2, wherein R1 to R6 are independently selected from at least one of C, H, O and halogen atoms; Formula 2.

[0014] In some of these embodiments, the phosphazene compound has the structure shown in Formulas 3 to 7: Formula 3 Formula 4 Formula 5 Formula 6 Formula 7.

[0015] By limiting phosphazene compounds to cyclic phosphazene compounds with a six-membered cyclic phosphazene structure, particularly those with structures shown in Formulas 2 to 7, these specific cyclic phosphazenes exhibit higher thermal stability and better phosphorus content, and can be well dispersed in electrolytes. In the event of thermal runaway, their cyclic structure can more effectively decompose to generate highly reactive phosphorus free radicals, efficiently capturing hydrogen and hydroxyl free radicals generated during combustion. This allows for a faster and more thorough interruption of the combustion chain reaction, significantly shortening the self-extinguishing time of the electrolyte (e.g., from 63 seconds to 2 seconds). While ensuring basic electrochemical performance, this greatly enhances the battery's safety protection capabilities.

[0016] In some embodiments, the mass fraction of the bisphosphite compound is 0.01% to 5% based on the total mass of the electrolyte, preferably 0.1% to 2%.

[0017] In some embodiments, the mass fraction of the phosphazene compound is 1% to 15%; preferably, the mass fraction of the phosphazene compound is 2% to 10%.

[0018] In some of these embodiments, the lithium salt has a mass fraction of 10% to 20%.

[0019] In some of these embodiments, the organic solvent has a mass fraction of 75-90%.

[0020] In some embodiments, the organic solvent includes cyclic carbonates and chain esters.

[0021] In some embodiments, the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butene carbonate, or γ-butyrolactone.

[0022] In some embodiments, the chain ester includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate.

[0023] In some of these embodiments, the lithium salt includes at least one of LiPF6, Li(FSO2)2N, and Li(CF3SO2)2N.

[0024] The mass fraction of the lithium salt is 10-20% based on the mass of the electrolyte (100%), for example, the mass fraction of the lithium salt is 10%, 12%, 15%, 18%, or 20%, or a range thereof.

[0025] In some embodiments, the lithium-ion battery electrolyte further includes a third additive, which includes at least one of the following: cyclic carbonate compounds containing unsaturated bonds, halogenated cyclic carbonate compounds, sulfate compounds, sulfonyl lactone compounds, phosphate compounds, and borate compounds.

[0026] In some embodiments, the cyclic carbonate compound containing unsaturated bonds includes vinylene carbonate and vinyl ethylene carbonate.

[0027] In some embodiments, the halocyclic carbonate compound includes fluoroethylene carbonate.

[0028] In some embodiments, the sulfate ester compound includes vinyl sulfate.

[0029] In some embodiments, the sulfonyl lactone compound includes 1,3-propanesulfonyl lactone.

[0030] In some embodiments, the phosphate compound includes tris(trimethylsilyl)phosphate.

[0031] In some embodiments, the borate ester compound includes tris(trimethylsilyl)boronic acid ester.

[0032] In some embodiments, the lithium salt compound includes at least one of lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, and lithium difluorooxalate phosphate.

[0033] In some embodiments, the volume ratio of the cyclic carbonate to the chain carboxylic acid ester is (10~40):(60~90).

[0034] By limiting the organic solvents to include cyclic carbonates (such as ethylene carbonate EC) and linear esters (such as ethyl methyl carbonate EMC and diethyl carbonate DEC), and controlling the volume ratio of cyclic carbonates to linear esters at (10~40):(60~90), this solvent system exhibits good lithium salt dissociation capability, suitable viscosity, and a wide electrochemical window. Cyclic carbonates contribute to the formation of a stable SEI film, while linear esters improve ionic conductivity and low-temperature performance. At this ratio, their synergistic effect provides a suitable dissolution and reaction environment for bisphosphites and phosphazene additives, promoting the uniform and effective function of the additives at the electrode interface, thereby supporting the improvement of overall battery performance.

[0035] According to another aspect of the present invention, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte; the electrolyte comprising the above-described lithium-ion battery electrolyte.

[0036] By applying an electrolyte containing a combination of bisphosphite compounds and phosphazene compounds to a complete lithium-ion battery comprising positive and negative electrodes, the electrolyte achieves full contact and function with the positive and negative electrode materials during battery charging and discharging. The protective film formed at the electrode interface by the bisphosphite compounds and the flame-retardant function of the phosphazene compounds are realized and manifested in the complete battery system, ultimately resulting in a lithium-ion battery product with comprehensive benefits such as high capacity retention at high temperatures, long cycle life, low gas generation, low internal resistance, and high safety.

[0037] In some of these embodiments, the positive electrode sheet comprises a positive electrode material.

[0038] In some embodiments, the cathode material includes LiCoO2 and LiNi. x Co y Mn z O2, LiNi x Mn y O2, LiMn2O4, LiMnO2, Li2MnO4, Li 1+a Mn 1-x M x O2, LiCo 1-x M x O2, LiMn 1-x M x O4, Li2Mn 1-x O4 is any one or more of the following: M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, and 0≤x, y, z≤1.

[0039] In some of these embodiments, the negative electrode sheet comprises a negative electrode material.

[0040] In some embodiments, the negative electrode material includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silicon-oxygen negative electrode, and silicon-carbon negative electrode.

[0041] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. By combining and introducing bisphosphite compounds and phosphazene compounds with specific structures into the electrolyte system, the bisphosphite compounds can participate in the reaction at the positive and negative electrode interfaces to form a stable solid electrolyte interphase (SEI) film, effectively suppressing the side reactions between the electrode materials and the electrolyte at high temperatures, thereby significantly improving the high-temperature storage and cycle performance of the battery, and reducing the gas generation rate and DC internal resistance; at the same time, the phosphazene compounds, as flame retardant components, can decompose to produce free radical quenchers when the electrolyte is heated or burned, interrupting the combustion chain reaction, thereby greatly improving the self-extinguishing ability of the electrolyte and enhancing the safety of the battery system. Thus, the technical effect of simultaneously achieving high temperature long life and high safety in a single electrolyte formulation is achieved.

[0042] 2. By limiting the bisphosphite compounds to at least one selected from 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite), these specific compounds have clearly defined alkenyl / alkynyl groups and substituents with strong electron-withdrawing or passivating effects. Among these, the alkenyl / alkynyl groups are more readily reduced to form a film on the negative electrode surface, while the difluorophosphite group or trimethylsilyl phosphite group helps to form a low-resistance protective film on the positive electrode surface and remove harmful HF, thereby synergistically achieving a better interface stability effect. This further optimizes the battery's performance in terms of high-temperature storage capacity retention, cycle performance, and gas generation suppression.

[0043] 3. By limiting phosphazene compounds to cyclic phosphazene compounds with a six-membered cyclic phosphazene structure, especially compounds with structures shown in Formulas 2 to 7, these specific cyclic phosphazene structures exhibit higher thermal stability and better phosphorus content, and can be well dispersed in electrolytes. In the event of thermal runaway, their cyclic structure can more effectively decompose to generate highly reactive phosphorus free radicals, efficiently capturing hydrogen and hydroxyl free radicals generated during combustion, thereby more quickly and thoroughly interrupting the combustion chain reaction. This significantly shortens the self-extinguishing time of the electrolyte (e.g., from 63 seconds to 2 seconds), greatly enhancing the battery's safety protection capabilities while ensuring basic electrochemical performance.

[0044] 4. By controlling the mass fraction of the diphosphite compound at 0.01%~5% (preferably 0.1%~2%), the mass fraction of the phosphazene compound at 1%~15% (preferably 2%~10%), the mass fraction of the lithium salt at 10%~20%, and the mass fraction of the organic solvent at 75%~90%, the concentration thresholds at which each component can exert its effectiveness in the system are met, while avoiding the negative effects caused by excessive addition. For example, an appropriate amount of diphosphite is sufficient to form an effective interfacial film without significantly deteriorating ionic conductivity; an appropriate amount of phosphazene compound can provide sufficient flame retardancy without impairing battery cycle life; and reasonable lithium salt and solvent contents ensure the basic ion mobility and electrochemical stability of the electrolyte, thereby synergistically optimizing the battery's high-temperature performance, safety, and internal resistance to a better level.

[0045] 5. By limiting the organic solvents to include cyclic carbonates (such as ethylene carbonate EC) and linear esters (such as ethyl methyl carbonate EMC and diethyl carbonate DEC), and controlling the volume ratio of cyclic carbonates to linear esters at (10~40):(60~90), this solvent system exhibits good lithium salt dissociation capability, suitable viscosity, and a wide electrochemical window. Cyclic carbonates contribute to the formation of a stable SEI film, while linear esters improve ionic conductivity and low-temperature performance. At this ratio, their synergistic effect provides a suitable dissolution and reaction environment for bisphosphites and phosphazene additives, promoting the uniform and effective function of the additives at the electrode interface, thereby supporting the improvement of overall battery performance.

[0046] 6. By applying an electrolyte containing a combination of bisphosphite compounds and phosphazene compounds to a complete lithium-ion battery comprising positive and negative electrodes, the electrolyte achieves full contact and function with the positive and negative electrode materials during battery charging and discharging. The protective film formed at the electrode interface by the bisphosphite compounds and the flame-retardant function of the phosphazene compounds are realized and manifested in the complete battery system, ultimately resulting in a lithium-ion battery product with comprehensive benefits including high capacity retention at high temperatures, long cycle life, low gas production, low internal resistance, and high safety. Detailed Implementation

[0047] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0048] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0049] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0050] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0051] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0052] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] In the field of lithium-ion battery technology, to achieve higher energy density to meet the demand for long driving range, the commonly used technical approach is to use layered oxides with high nickel content (such as LiNi). x Co y Mn z This method uses O2 (x≥0.6) as the positive electrode material, coupled with a high operating voltage window (e.g., above 4.3V), and employs a liquid electrolyte composed of lithium salt (e.g., LiPF6) and organic carbonate solvent (e.g., ethylene carbonate, ethyl methyl carbonate). Specifically, this scheme provides lithium ions through the dissociation of the lithium salt in the solvent. The lithium ions migrate back and forth between the positive and negative electrodes during charging and discharging, achieving charge storage and release. Its widespread application is primarily due to its ability to achieve relatively high initial capacity and ionic conductivity, and to provide effective wetting of the electrode material.

[0054] However, this approach does not perform ideally when applied to harsh operating environments with high temperatures and high voltages. A fundamental contradiction lies in the fact that the highly active cathode material and high-voltage operating conditions used in this approach to achieve high energy density inevitably exacerbate side reactions at the electrode-electrolyte interface (especially the cathode / electrolyte interface), impairing the battery's long-term cycle and storage stability, and even triggering significant gas generation and increased internal resistance. Specifically, when high-nickel ternary lithium-ion batteries using related electrolyte technologies undergo 60°C high-temperature storage or 45°C high-temperature cycling tests, the battery's capacity retention rate rapidly declines, accompanied by significant volume expansion (gas generation) and increased DC internal resistance.

[0055] Through in-depth analysis, the inventors discovered that the root causes of the aforementioned contradictions are multifaceted: From a materials chemistry perspective, high-nickel cathode materials are prone to surface lattice oxygen precipitation under high voltage, exhibiting strong oxidizing properties and continuously catalyzing the decomposition of carbonate solvents; from an interface chemistry perspective, commonly used single-functional additives in related technologies (such as silane-containing borate esters or phosphate esters) are difficult to simultaneously form a stable and low-resistance protective film at the cathode and anode interfaces, leading to accelerated interfacial side reactions at high temperatures; from an electrochemical perspective, continuous side reactions consume active lithium and electrolyte, and the resulting gas and interfacial impedance layer accumulation hinder lithium-ion transport and increase battery internal resistance. These factors collectively limit the performance ceiling of existing solutions in addressing the new demands of high temperature and high voltage.

[0056] To overcome the aforementioned contradictions, this invention proposes a different technical approach. Its core concept lies in introducing a bisphosphite compound with a specific molecular structure as an additive into the electrolyte. Utilizing the differential functional groups at both ends of its molecule, it participates in constructing stable protective layers at the interfaces of the negative and positive electrodes, thereby synergistically suppressing interfacial side reactions, reducing gas production, and lowering interfacial impedance. In other words, this invention provides a novel electrolyte additive and its application to solve the problems of poor cycle and storage performance, excessive gas production, and rapid internal resistance growth caused by interfacial instability in high-nickel lithium-ion batteries under high-temperature and high-voltage conditions, achieving the technical effect of improving the overall high-temperature performance of the battery. Specifically, this invention adopts the following technical solution: According to one aspect of the present invention, a lithium-ion battery electrolyte is provided, comprising an organic solvent, a lithium salt, and a bisphosphite compound; The bisphosphite compound has the structure shown in Formula I: Formula 1 Wherein, A is selected from C. n H 2n-2 Or C n H 2n-4n=2~12; B is selected from halogen atoms or -Si(C) m H 2m+1 )3, m=1~4.

[0057] By combining and introducing bisphosphite compounds and phosphazene compounds with specific structures into the electrolyte system, the bisphosphite compounds can participate in the reaction at the positive and negative electrode interfaces to form a stable solid electrolyte interphase (SEI) film, effectively suppressing the side reactions between the electrode materials and the electrolyte at high temperatures. This significantly improves the high-temperature storage and cycle performance of the battery, and reduces the gas generation rate and DC internal resistance. At the same time, the phosphazene compounds, as flame retardant components, can decompose to produce free radical quenchers when the electrolyte is heated or burned, interrupting the combustion chain reaction. This greatly improves the self-extinguishing ability of the electrolyte and enhances the safety of the battery system. Thus, the technical effect of simultaneously achieving high-temperature long life and high safety in a single electrolyte formulation is achieved.

[0058] In some of these embodiments, the bisphosphite compound is selected from at least one of 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite).

[0059] By limiting the bisphosphite compounds to at least one selected from 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite), these specific compounds possess clearly defined alkenyl / alkynyl groups and substituents with strong electron-withdrawing or passivating effects. Among these, the alkenyl / alkynyl groups are more readily reduced to form a film on the negative electrode surface, while the difluorophosphite or trimethylsilyl phosphite groups help form a low-resistance protective film on the positive electrode surface and remove harmful HF, thereby synergistically achieving superior interface stability. This further optimizes and confirms the battery's performance in high-temperature storage capacity retention, cycle performance, and gas generation suppression.

[0060] In some embodiments, the lithium-ion electrolyte further includes a second additive, which includes phosphazene compounds.

[0061] In some of these embodiments, the phosphazene compound is a cyclic phosphazene compound.

[0062] The cyclic phosphazene compound has a six-membered cyclic phosphazene structure.

[0063] In some of these embodiments, the phosphazene compound has the structure shown in Formula 2, wherein R1 to R6 are independently selected from at least one of C, H, O and halogen atoms; Formula 2.

[0064] In some of these embodiments, the phosphazene compound has the structure shown in Formulas 3 to 7: Formula 3 Formula 4 Formula 5 Formula 6 Formula 7.

[0065] By limiting phosphazene compounds to cyclic phosphazene compounds with a six-membered cyclic phosphazene structure, particularly those with structures shown in Formulas 2 to 7, these specific cyclic phosphazenes exhibit higher thermal stability and better phosphorus content, and can be well dispersed in electrolytes. In the event of thermal runaway, their cyclic structure can more effectively decompose to generate highly reactive phosphorus free radicals, efficiently capturing hydrogen and hydroxyl free radicals generated during combustion. This allows for a faster and more thorough interruption of the combustion chain reaction, significantly shortening the self-extinguishing time of the electrolyte (e.g., from 63 seconds to 2 seconds). While ensuring basic electrochemical performance, this greatly enhances the battery's safety protection capabilities.

[0066] In some embodiments, the mass fraction of the bisphosphite compound is 0.01% to 5% based on the total mass of the electrolyte, preferably 0.1% to 2%.

[0067] In some embodiments, the mass fraction of the phosphazene compound is 1% to 15%; preferably, the mass fraction of the phosphazene compound is 2% to 10%.

[0068] In some of these embodiments, the lithium salt has a mass fraction of 10% to 20%.

[0069] In some of these embodiments, the organic solvent has a mass fraction of 75-90%.

[0070] In some embodiments, the organic solvent includes cyclic carbonates and chain esters.

[0071] In some embodiments, the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butene carbonate, or γ-butyrolactone.

[0072] In some embodiments, the chain ester includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate.

[0073] In some of these embodiments, the lithium salt includes at least one of LiPF6, Li(FSO2)2N, and Li(CF3SO2)2N.

[0074] In some embodiments, the lithium-ion battery electrolyte further includes a third additive, which includes at least one of the following: cyclic carbonate compounds containing unsaturated bonds, halogenated cyclic carbonate compounds, sulfate compounds, sulfonyl lactone compounds, phosphate compounds, and borate compounds.

[0075] In some embodiments, the cyclic carbonate compound containing unsaturated bonds includes vinylene carbonate and vinyl ethylene carbonate.

[0076] In some embodiments, the halocyclic carbonate compound includes fluoroethylene carbonate.

[0077] In some embodiments, the sulfate ester compound includes vinyl sulfate.

[0078] In some embodiments, the sulfonyl lactone compound includes 1,3-propanesulfonyl lactone.

[0079] In some embodiments, the phosphate compound includes tris(trimethylsilyl)phosphate.

[0080] In some embodiments, the borate ester compound includes tris(trimethylsilyl)boronic acid ester.

[0081] In some embodiments, the lithium salt compound includes at least one of lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, and lithium difluorooxalate phosphate.

[0082] In some embodiments, the volume ratio of the cyclic carbonate to the chain carboxylic acid ester is (10~40):(60~90).

[0083] By limiting the organic solvents to include cyclic carbonates (such as ethylene carbonate EC) and linear esters (such as ethyl methyl carbonate EMC and diethyl carbonate DEC), and controlling the volume ratio of cyclic carbonates to linear esters at (10~40):(60~90), this solvent system exhibits good lithium salt dissociation capability, suitable viscosity, and a wide electrochemical window. Cyclic carbonates contribute to the formation of a stable SEI film, while linear esters improve ionic conductivity and low-temperature performance. At this ratio, their synergistic effect provides a suitable dissolution and reaction environment for bisphosphites and phosphazene additives, promoting the uniform and effective function of the additives at the electrode interface, thereby supporting the improvement of overall battery performance.

[0084] According to another aspect of the present invention, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte; the electrolyte comprising the above-described lithium-ion battery electrolyte.

[0085] In some of these embodiments, the positive electrode sheet comprises a positive electrode material.

[0086] In some embodiments, the cathode material includes LiCoO2 and LiNi. x Co y Mn z O2, LiNi x Mn y O2, LiMn2O4, LiMnO2, Li2MnO4, Li 1+a Mn 1-x M x O2, LiCo 1-x M x O2, LiMn 1-x M x O4, Li2Mn 1-x O4 is any one or more of the following: M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, and 0≤x, y, z≤1.

[0087] In some of these embodiments, the negative electrode sheet comprises a negative electrode material.

[0088] In some embodiments, the negative electrode material includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silicon-oxygen negative electrode, and silicon-carbon negative electrode.

[0089] By applying an electrolyte containing a combination of bisphosphite compounds and phosphazene compounds to a complete lithium-ion battery comprising positive and negative electrodes, the electrolyte achieves full contact and function with the positive and negative electrode materials during battery charging and discharging. The protective film formed at the electrode interface by the bisphosphite compounds and the flame-retardant function of the phosphazene compounds are realized and manifested in the complete battery system, ultimately resulting in a lithium-ion battery product with comprehensive benefits such as high capacity retention at high temperatures, long cycle life, low gas generation, low internal resistance, and high safety.

[0090] In this application, "bisphosphite compound" refers to any compound whose molecular structure contains two phosphite groups, and whose two ends have unsaturated bond groups that can be reduced to form a film on the negative electrode surface of a lithium-ion battery, and specific functional groups that can form a protective film or remove harmful substances on the positive electrode surface, thereby synergistically stabilizing the positive and negative electrode interfaces and reducing the DC internal resistance of the battery. For example, it may include, but is not limited to: compounds having the general structural formula shown in Formula 1, wherein A is a group containing an alkenyl or alkynyl group, and B is a halogen atom or a silane group; or specific examples thereof, such as at least one of 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite), or combinations thereof.

[0091] In this application, the "A" group (in bisphosphite compounds) refers to any hydrocarbon structural unit containing a carbon-carbon unsaturated bond (alkenyl or alkynyl) that can preferentially undergo electrochemical reduction reactions before the negative electrode surface during lithium-ion battery charging, participating in the formation of the solid electrolyte interphase (SEI) film to enhance interfacial stability. For example, it may include, but is not limited to, units conforming to the general formula C. n H 2n-2 Or C n H 2n-4 The group, where n is an integer from 2 to 12, such as vinyl, ethynyl, butenyl or butynyl-derived linking groups, or combinations thereof.

[0092] In this application, the "B" group (in bisphosphite compounds) refers to any halogen atom or organosilicon group attached to a phosphite group that can interact with the surface of the lithium-ion battery cathode material to form a low-impedance protective layer and / or remove acidic substances (such as HF) from the electrolyte to reduce side reactions. For example, it may include, but is not limited to: fluorine (F), chlorine (Cl), bromine (Br), iodine (I) atoms, or trialkylsilane groups such as -Si(CH3)3, -Si(C2H5)3, or combinations thereof.

[0093] In this application, "phosphazene compounds" refers to any cyclic or chain structure in which the molecular skeleton contains alternating phosphorus and nitrogen atoms, and which can decompose under the thermal runaway conditions of lithium-ion batteries to generate free radical quenchers, thereby interrupting the combustion chain reaction and improving the safety of the electrolyte and the battery. For example, it may include, but is not limited to: compounds having a six-membered cyclic phosphazene structure, such as cyclic phosphazene compounds with structures shown in Formulas 2 to 7, or combinations thereof.

[0094] In the description of this invention, "a plurality of" means two or more.

[0095] In a specific embodiment of the present invention, the battery can also be a battery pack assembled from the aforementioned battery modules. The battery pack may contain one or more battery modules, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack. Specifically, the battery pack may include a battery box and multiple battery modules disposed within the battery box; the battery box includes an upper box and a lower box, the upper box covering the lower box and forming a closed space for accommodating the battery modules. The multiple battery modules can be arranged in the battery box in any manner.

[0096] According to another aspect of the present invention, an electrical device is provided, comprising the battery described in the above-described technical solution. Thus, the electrical device possesses all the features and advantages of the battery described in the above-described technical solution, which will not be repeated here. Specifically, the battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0097] The following detailed description of this application is based on specific embodiments, but the implementation and protection of this invention are not limited thereto. The following embodiments are only some embodiments of this application and are not intended to limit this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0098] Example 1 This embodiment provides an electrolyte, the preparation method of which is as follows: Lithium hexafluorophosphate is used as the lithium salt (the mass of lithium hexafluorophosphate is 14% of the electrolyte mass), and a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) is used as the organic solvent, wherein the volume ratio of EC:EMC:DEC is 30:50:20; the organic solvent accounts for 85% of the total mass of the electrolyte. In addition, the electrolyte also contains an additive: compound 2 (2-butene-1,4-bis(difluorophosphite)) accounting for 1% of the total mass of the electrolyte.

[0099] Example 2 This embodiment provides an electrolyte, the preparation method of which is as follows: Lithium hexafluorophosphate is used as the lithium salt (the mass of lithium hexafluorophosphate is 15% of the electrolyte mass), and a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) is used as the organic solvent, wherein the volume ratio of EC:EMC:DEC is 30:50:20; the organic solvent accounts for 84% of the total mass of the electrolyte. In addition, the electrolyte also contains an additive: compound 3 (2-butyne-1,4-bis(difluorophosphite)) accounting for 1% of the total mass of the electrolyte.

[0100] Example 3 Lithium hexafluorophosphate is used as the lithium salt (the mass of lithium hexafluorophosphate is 15% of the electrolyte mass), and a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) is used as the organic solvent, wherein the volume ratio of EC:EMC:DEC is 35:45:20; the organic solvent accounts for 84% of the total mass of the electrolyte. In addition, the electrolyte also contains an additive: compound 4 (2-butene-1,4-bis(di(trimethylsilyl)phosphite)) accounting for 1% of the total mass of the electrolyte.

[0101] Example 4 The only difference between this embodiment and Example 1 is that the mass fraction of compound 2 is 0.1%, and the organic solvent accounts for 84.9% of the total mass of the electrolyte; all other conditions and parameters are exactly the same as in Example 1.

[0102] Example 5 The only difference between this embodiment and Example 1 is that the mass fraction of compound 2 is 2%, and the organic solvent accounts for 83% of the total mass of the electrolyte; all other conditions and parameters are exactly the same as in Example 1.

[0103] Example 6 The only difference between this embodiment and Example 1 is that a phosphazene compound (formula 4 compound) with a mass fraction of 2% was added, and the organic solvent accounts for 83% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0104] Example 7 The only difference between this embodiment and Example 1 is that a phosphazene compound (formula 4) with a mass fraction of 5% was added, and the organic solvent accounts for 81% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0105] Example 8 The only difference between this embodiment and Example 1 is that a phosphazene compound (formula 4) with a mass fraction of 10% is added, and the organic solvent accounts for 76% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0106] Example 9 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, it also contains 1% vinyl sulfate (DTD) and 5% phosphazene compound (compound 4) with a mass fraction of 1%, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0107] Example 10 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, a compound containing 1% vinylene carbonate (VC) and 5% phosphazene (formula 4) has been added, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0108] Example 11 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, a compound containing 1% fluoroethylene carbonate (FEC) and 5% phosphazene compound (compound 4) has been added, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0109] Example 12 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, a compound containing 1%,3-propanesulfonic acid lactone (PS) with a mass fraction of 1% and 5% phosphazene compound (compound 4) is added, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0110] Example 13 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, a compound containing 1% lithium difluorophosphate (LiPO2F2) and 5% phosphazene compound (compound 4) with a mass fraction of 1% is added, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0111] Example 14 The only difference between this embodiment and Example 1 is that, in addition to compound 2 having a mass fraction of 1%, a compound containing 1% lithium difluorooxalate borate (LiDFOB) and 5% phosphazene compound (compound 5) with a mass fraction of 1% is added, and the organic solvent accounts for 79% of the total mass of the electrolyte; other conditions and parameters are exactly the same as in Example 1.

[0112] Comparative Example 1 The only difference between this comparative example and Example 1 is that compound 2 is not added, and the organic solvent accounts for 86% of the total mass of the electrolyte; all other conditions and parameters are exactly the same as in Example 1.

[0113] Comparative Example 2 The only difference between this comparative example and Example 9 is that the volume ratio of EC:EMC:DEC in the organic solvent is adjusted to 8:50:20; all other conditions and parameters are exactly the same as in Example 9.

[0114] Comparative Example 3 The only difference between this comparative example and Example 9 is that the volume ratio of EC:EMC:DEC in the organic solvent is adjusted to 50:50:20; all other conditions and parameters are exactly the same as in Example 9.

[0115] Implementation Results Example Preparation of lithium-ion batteries: Lithium nickel manganese oxide (LiNi) is used as the positive electrode active material. 0.75 Mn 0.25 O2), conductive agent Super-P, and binder PVDF were dissolved in N-methylpyrrolidone at a mass ratio of 94:3.0:3.0 to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the current collector aluminum foil with a coating amount of 18 mg / cm². 2 After drying at 85°C, the material is cold-pressed, trimmed, cut into pieces, and slit. Then, it is dried under vacuum at 85°C for 4 hours, and the tabs are welded to produce the positive electrode sheet of a lithium-ion secondary battery that meets the requirements. A negative electrode slurry was prepared by dissolving hard carbon (anode active material), Super-P (conductive agent), CMC (thickener), and SBR (binder) in deionized water at a mass ratio of 96.5:1.0:1.0:1.5. The slurry was then uniformly coated onto the copper foil current collector at a coating weight of 8.9 mg / cm². 2 After drying at 85℃, the material is cold-pressed, trimmed, cut into pieces, and slit. Then, it is dried under vacuum at 110℃ for 4 hours, and the tabs are welded to produce a negative electrode sheet for a lithium-ion secondary battery that meets the requirements. The electrolytes obtained in Examples 1-14 and Comparative Examples 1-3, along with the positive electrode, negative electrode, and separator (PE film), were stacked to form a battery with a thickness of 8 mm, a width of 60 mm, and a length of 130 mm. The battery was then vacuum-baked at 85°C for 10 h, injected with electrolyte, and allowed to stand for 24 h. After that, it was charged to 4.3 V with a constant current of 0.1 C (200 mA), and then charged at a constant voltage of 4.3 V until the current dropped to 0.05 C (100 mA). Then, it was discharged to 2.8 V with a constant current of 0.1 C (200 mA). This charge-discharge cycle was repeated twice. Finally, it was charged to 3.8 V with a constant current of 0.1 C (200 mA) to obtain a lithium-ion secondary battery.

[0116] The performance of lithium-ion secondary batteries prepared using the electrolytes prepared in Examples 1-14 and Comparative Examples 1-3 was tested, and the specific methods were as follows: Storage capacity retention: At 25°C, the lithium-ion secondary batteries prepared in Examples 1-14 and Comparative Examples 1-3 were first charged to 4.3V with a constant current of 1C, and then further charged to a current of 0.05C with a constant voltage of 4.3V. Then, the lithium-ion secondary batteries were discharged to 2.8V with a constant current of 1C. This discharge capacity is the discharge capacity of the lithium-ion secondary batteries before high-temperature storage. Next, the lithium-ion secondary batteries were charged to 4.3V with a constant current of 1C and stored at 60°C for 30 days. After storage, the lithium-ion secondary batteries were placed at 25°C and then discharged to 2.8V with a constant current of 0.5C. Then, they were charged to 4.3V with a constant current of 1C, and then further charged to a current of 1C with a constant voltage of 4.3V. Finally, they were discharged to 2.8V with a constant current of 1C. This final discharge capacity is the discharge capacity of the lithium-ion secondary batteries after high-temperature storage. Capacity retention rate (%) of lithium-ion secondary battery after high-temperature storage = [Discharge capacity of lithium-ion secondary battery after high-temperature storage / Discharge capacity of lithium-ion secondary battery before high-temperature storage] × 100%.

[0117] Cyclic performance test: At 45℃, the lithium-ion secondary battery was first charged to 4.3V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.3V, and finally discharged to 2.8V with a constant current of 1C. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion secondary battery was subjected to cyclic charge-discharge tests in the above manner, and the discharge capacity of the 800th cycle was recorded. Cyclic capacity retention rate (%) = [Discharge capacity of lithium-ion secondary battery in 800th cycle / Discharge capacity of lithium-ion secondary battery in the first cycle] × 100%.

[0118] High-temperature storage test: The lithium-ion battery was then stored at 60℃ for 30 days. After storage, the lithium-ion secondary battery was placed in a 25℃ environment, and the battery volume was tested using the water displacement method. The battery thickness was measured with a micrometer. Then, the lithium-ion secondary battery was discharged to 2.8V with a constant current of 0.5C, and then charged to 4.3V with a constant current of 1C. It was then further charged to 1C with a constant voltage of 4.3V, and then discharged to 2.8V with a constant current of 1C. The final discharge capacity is the discharge capacity of the lithium-ion secondary battery after high-temperature storage. The battery volume expansion rate = (volume after storage / volume before storage - 1)%.

[0119] DC internal resistance test: At 25°C, the lithium-ion secondary batteries prepared in the examples and comparative examples were first charged to 4.3V with a constant current of 1C. They were then further charged to a current of 0.05C with a constant voltage of 4.3V. Finally, the lithium-ion secondary batteries were discharged for 1 hour with a constant current of 0.5C, maintaining a state of charge (SOC) of 50%. After resting for 10 minutes, the voltage V1 was recorded. Then, the batteries were discharged for 10 seconds with a current I (I=5C), and the discharge termination voltage V2 was recorded. The DC internal resistance (DCIR) of the battery is calculated using the formula: DCIR = (V1 - V2) / I, in mΩ.

[0120] Electrolyte self-extinguishing time test: The molded nickel foam sheet is thoroughly cleaned and dried. Then, the nickel foam is held with metal tweezers, 1g of electrolyte is dropped into the nickel foam, the electrolyte is ignited, and the time from when the ignition source is removed to when the electrolyte is extinguished is recorded as the self-extinguishing time.

[0121] The test results are shown in Table 1: Table 1 Performance test results of lithium-ion secondary batteries As shown in Table 1, a comparison between Examples 1-3 and Comparative Example 1 reveals that the addition of the diphosphite compound to the electrolyte forms a low-internal-resistance, stable SEI film on the positive and negative electrode surfaces, significantly improving the battery's high-temperature cycling and storage performance while reducing gas production. A comparison between Examples 6-8 and Example 1 shows that the addition of phosphazene additives significantly reduces the electrolyte's self-quenching time, makes the electrolyte less ignitable, and significantly improves battery safety. A comparison between Examples 9-14 and Comparative Example 1 demonstrates that the diphosphite compound of the present invention, when used in combination with additives such as vinyl sulfate (DTD), vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), lithium difluorophosphate (LiPO2F2), or lithium difluorooxalate borate (LiDFOB), can achieve even better performance.

[0122] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0123] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium-ion battery electrolyte, characterized in that, The lithium-ion battery electrolyte includes an organic solvent, a lithium salt, and a bisphosphite compound; The bisphosphite compound has the structure shown in Formula I: Formula 1 Wherein, A is selected from C. n H 2n-2 Or C n H 2n-4 n=2~12; B is selected from halogen atoms or -Si(C) m H 2m+1 )3, m=1~4.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, The bisphosphite compound is selected from at least one of 2-butene-1,4-bis(difluorophosphite), 2-butyn-1,4-bis(difluorophosphite), 2-butene-1,4-bis(di(trimethylsilyl)phosphite), and 2-butyn-1,4-bis(di(trimethylsilyl)phosphite).

3. The lithium-ion battery electrolyte according to claim 1 or 2, characterized in that, The lithium-ion battery electrolyte also includes a second additive, which includes phosphazene compounds. Preferably, the phosphazene compound is a cyclic phosphazene compound.

4. The lithium-ion battery electrolyte according to claim 3, characterized in that, The structure of the phosphazene compound is shown in Formula 2, wherein R1 to R6 are independently selected from at least one of C, H, O and halogen atoms; Formula 2.

5. The lithium-ion battery electrolyte according to claim 4, characterized in that, The structures of the phosphazene compounds are shown in Formulas 3 to 7: Formula 3 Formula 4 Formula 5 Formula 6 Formula 7.

6. The lithium-ion battery electrolyte according to any one of claims 1-3, characterized in that, Based on the total mass of the electrolyte, the mass fraction of the bisphosphite compound is 0.01% to 5%, preferably 0.1% to 2%. And / or, the mass fraction of the phosphazene compound is 1% to 15%; preferably, the mass fraction of the phosphazene compound is 2% to 10%. And / or, the lithium salt has a mass fraction of 10% to 20%; And / or, the organic solvent has a mass fraction of 75-90%.

7. The lithium-ion battery electrolyte according to any one of claims 1-3, characterized in that, The organic solvents include cyclic carbonates and chain esters; Preferably, the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butene carbonate, or γ-butyrolactone. Preferably, the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate. And / or, the lithium salt includes at least one of LiPF6, Li(FSO2)2N, and Li(CF3SO2)2N.

8. The lithium-ion battery electrolyte according to any one of claims 1-3, characterized in that, The lithium-ion battery electrolyte further includes a third additive, which includes at least one of the following: cyclic carbonate compounds containing unsaturated bonds, halogenated cyclic carbonate compounds, sulfate compounds, sulfonyl lactone compounds, phosphate compounds, borate ester compounds, and lithium salt compounds. Preferably, the cyclic carbonate compound containing unsaturated bonds includes vinylene carbonate and vinyl ethylene carbonate; Preferably, the halocyclic carbonate compound includes fluoroethylene carbonate; Preferably, the sulfate ester compound includes vinyl sulfate; Preferably, the sulfonyl lactone compound includes 1,3-propanesulfonyl lactone; Preferably, the phosphate ester compound includes tris(trimethylsilyl)phosphate; Preferably, the borate ester compound includes tris(trimethylsilyl)borate ester; Preferably, the lithium salt compound includes at least one of lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, and lithium difluorooxalate phosphate.

9. The lithium-ion battery electrolyte according to claim 7, characterized in that, The volume ratio of the cyclic carbonate to the chain carboxylic acid ester is (10~40):(60~90).

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte; the electrolyte includes the lithium-ion battery electrolyte according to any one of claims 1-9.

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