Electrolyte and lithium ion battery

Abstract

The embodiment of the invention provides an electrolyte and a lithium ion battery. The electrolyte comprises a lithium salt, a non-aqueous solvent and an additive, the additive is prepared from 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether, a compound with a structure as shown in a formula I, and 4-chloro-2-fluoro-5-sulfonylamino benzonitrile. According to the embodiment of the invention, 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether, the compound with the structure as shown in the formula I and 4-chloro-2-fluoro-5-sulfonylamino benzonitrile are added into the electrolyte, the electrolyte is applied to the lithium ion battery, and the obtained lithium ion battery has good high-temperature storage performance and normal-temperature and high-temperature cycle performance.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to electrolytes and lithium-ion batteries. Background Technology

[0002] Lithium-ion rechargeable batteries, as a relatively mature type of battery, are widely used in digital, energy storage, and power applications. However, the performance stability of lithium-ion batteries under high voltage and high temperature conditions still presents significant technical challenges.

[0003] Taking lithium cobalt oxide batteries as an example, at high voltages, such as 4.5V, the electrolyte of lithium cobalt oxide batteries is prone to side reactions with the electrode materials, leading to interface instability, increasing the internal resistance of the battery, and reducing its cycle stability and safety.

[0004] Therefore, how to improve the electrochemical performance of lithium-ion batteries under high voltage is an urgent problem to be solved in this field. Summary of the Invention

[0005] The purpose of this application is to provide an electrolyte and a lithium-ion battery.

[0006] To achieve the above objectives, the embodiments of this application propose the following technical solutions:

[0007] In a first aspect, embodiments of this application provide an electrolyte, the electrolyte comprising:

[0008] Lithium salts

[0009] Non-aqueous solvents, and

[0010] additive;

[0011] The additives include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, compounds with the structure shown in Formula I, and 4-chloro-2-fluoro-5-sulfonylaminobenzonitrile:

[0012]

[0013] Formula I.

[0014] In one embodiment, the content of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 0.5-3.5%, based on the total mass of the electrolyte.

[0015] In one embodiment, the content of the compound with the structure shown in Formula I is 0.5-5%, based on the total mass of the electrolyte.

[0016] In one embodiment, the content of the 4-chloro-2-fluoro-5-sulfonylaminobenzonitrile is 1-5%, based on the total mass of the electrolyte.

[0017] In one embodiment, the sodium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, and lithium difluorosulfonylimide.

[0018] The lithium salt content is 5-20%, based on the total mass of the electrolyte.

[0019] In one embodiment, the non-aqueous solvent is selected from at least one of carbonates, fluorocarbonates, carboxylic acid esters, fluorocarboxylic acid esters, ethers, and fluoroethers.

[0020] In one embodiment, the non-aqueous solvent is selected from at least one of propylene carbonate, methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, difluoroethyl acetate, and ethyl 2,2,2-trifluoroethyl acetate.

[0021] The content of the non-aqueous solvent is 66.5-93%, based on the total mass of the electrolyte.

[0022] In one embodiment, the electrolyte also includes other additives;

[0023] The other additives also include at least one of vinylene sulfate, triallyl phosphate, 1,3,6-hexanetrionitrile, ethylene glycol bis(propionitrile) ether, and adiponitrile;

[0024] The content of the other additives is 0.5-5%, based on the total mass of the electrolyte.

[0025] Secondly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising:

[0026] Positive electrode sheet;

[0027] Negative electrode plate;

[0028] Diaphragm; and

[0029] The electrolyte described in the first aspect.

[0030] In one embodiment, the positive electrode sheet includes a positive electrode active material; the positive electrode active material includes LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, and Li 1+a Mn 1-y MyO2, LiCo1-y MyO2, LiFe 1-y M y PO4 and Li2Mn 1-y M y At least one of O4;

[0031] Where M is selected from one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V and Ti, 0≤a<0.2, 0≤y<1;

[0032] The lithium-ion battery operates at a voltage of 3.0-4.5V.

[0033] Compared with the prior art, the embodiments of this application have at least the following beneficial effects:

[0034] In this embodiment, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a compound with the structure shown in Formula I, and 4-chloro-2-fluoro-5-sulfonylaminobenzonitrile are added as additives to the electrolyte. Taking a lithium cobalt oxide battery as an example, the electrolyte in this embodiment removes trace amounts of H2O and HF by using the compound with the structure shown in Formula I and 4-chloro-2-fluoro-5-sulfonylaminobenzonitrile, and coordinates / chelates cobalt ions, providing a stable interface environment for the uniform formation of the subsequent CEI film and reducing the corrosion of the negative electrode by HF. Meanwhile, the film formation by 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether can inhibit the dissolution of cobalt ions and prevent the lithium salt in the electrolyte and the positive and negative electrode materials from being oxidized under high voltage, providing a stable interface environment for the other two additives to supplement and repair the initial CEI film and the initial SEI film. In other words, by combining HFE458, the compound with the structure shown in Formula I, and 4-chloro-2-fluoro-5-sulfonylaminobenzonitrile, a uniform and stable CEI film and SEI film are generated. At the same time, the mechanical toughness and ion transport efficiency of the positive and negative electrode dual-interface film are optimized, which can effectively prevent the CEI film and SEI film from being damaged under high voltage, thereby preventing the destruction of the positive and negative electrode material structure. The three complement each other, improve the performance of the CEI film and SEI film, and thus significantly improve the high-temperature storage stability, room temperature and high-temperature cycling performance of lithium-ion batteries.

[0035] Additional aspects and advantages of this application will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this application. Detailed Implementation

[0036] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0038] It should also be understood that the terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. As used in the embodiments of this application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" are intended to include the plural forms.

[0039] Below, we will first explain some of the terms and materials used in this embodiment to facilitate understanding by those skilled in the art.

[0040] HFE458: 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropyl ether.

[0041] Compound I: A compound with the structure shown in Formula I.

[0042] Compound II: 4-chloro-2-fluoro-5-sulfonamide benzonitrile.

[0043] TAP: Triallyl phosphate.

[0044] LCO: Lithium cobalt oxide.

[0045] The electrolyte and lithium-ion battery of this application are described in detail below.

[0046] First, the electrolyte of the first aspect of this embodiment will be described.

[0047] Electrolyte.

[0048] Those skilled in the art will recognize that both the CEI (Chemical Electrode Injection) and SEI (Sediment Electrode Injection) films are indispensable components for ensuring the performance of lithium-ion batteries. The CEI film protects the cathode material and inhibits structural collapse and transition metal ion dissolution during charging and discharging of cathode materials (such as lithium cobalt oxide and lithium iron phosphate). It prevents the continuous decomposition of the electrolyte at high voltages (especially above 4.3V), reduces gas generation, and avoids battery swelling. Therefore, the quality of the CEI film directly determines the battery's cycle life, safety, and high-voltage performance. A CEI film capable of withstanding higher potentials is key to achieving high energy density in high-voltage batteries.

[0049] The SEI film ensures ion conduction inside the battery and prevents internal short circuits. When the SEI film is damaged or reconstructed during cycling, it will continuously consume electrolyte and active materials, leading to a shortened lifespan of the lithium-ion battery.

[0050] The maximum charging cutoff voltage of conventional lithium cobalt oxide batteries is usually around 4.3V. When this voltage is exceeded, for example, when the charging cutoff voltage is increased to 4.5V, a series of serious interfacial side reactions and bulk structure problems will be triggered, leading to a sharp decline in the performance of lithium-ion batteries.

[0051] Specifically, when the voltage exceeds 4.5V, oxygen atoms in the lithium cobalt oxide lattice become unstable and easily precipitate as oxygen, causing the lattice structure to transform from a layered phase to a spinel phase or even a rock salt phase (CoO2). This phase transition is irreversible, resulting in the loss of active material and permanent capacity decay. Simultaneously, under high voltage, the Co atoms in the LCO lattice... 3+ It will be oxidized into unstable Co. 4+ The latter (cobalt ions) easily dissolve from the crystal lattice into the electrolyte, further damaging the cathode material structure and causing capacity decay. Furthermore, the SEI film formed on the anode surface is prone to rupture under high voltage. The migration of cobalt ions combined with the rupture of the SEI film makes dendrite formation on the anode surface easy. Simultaneously, the migration of cobalt ions and the rupture of the SEI film lead to uneven distribution of interfacial charge, preventing the products of subsequent SEI film repair additives from forming uniformly on the anode surface, creating a vicious cycle that leads to a rapid decline in the performance of the lithium-ion battery.

[0052] Secondly, traditional non-aqueous solvents in electrolytes, such as carbonate-based solvents, undergo violent oxidation reactions on the positive electrode surface under high voltage, forming an unstable CEI film. This CEI film is mainly composed of organic byproducts, and its loose and unstable structure cannot effectively prevent the continuous oxidation of the electrolyte. Instead, it increases interfacial impedance and consumes active lithium salts (such as LiPF6), and also produces gases (such as CO2), solid byproducts, and acidic substances (such as HF). LiPF6 is unstable at high temperatures and in the presence of moisture, and decomposes to produce Lewis acids PF5 and LiF. PF5 further catalyzes the decomposition of the electrolyte solvent. Under high voltage, this decomposition process is accelerated. At the same time, trace amounts of moisture react with LiPF6 to generate HF. HF corrodes the positive electrode material and accelerates the dissolution of transition metals. Meanwhile, the rupture of the SEI film under high voltage accelerates the consumption of electrolyte and active materials. This leads to an exacerbation of the reaction between HF and active lithium salt, as well as the decomposition of the electrolyte solvent, under high voltage. The instability of the CEI film under high voltage and the consumption of active materials in the electrolyte due to the rupture of the SEI film under high voltage increase the battery's internal resistance and safety hazards. Furthermore, during high-voltage cycling, water undergoes co-oxidation on the positive electrode surface, generating oxygen and acidic substances, further accelerating electrolyte decomposition.

[0053] Furthermore, as mentioned earlier, under high voltage, the solvent in the electrolyte forms an unstable CEI film at the positive electrode. This prevents the CEI film from effectively protecting the positive electrode material from corrosion or dissolution, leading to a decline in the high-temperature storage performance of the lithium-ion battery. In addition, the insufficient stability of the positive electrode CEI film causes simultaneous corrosion of the negative electrode. This is because the instability of the positive electrode CEI film causes cobalt ions in the positive electrode material to dissolve. These dissolved cobalt ions migrate to the negative electrode and are reduced and deposited on the graphite negative electrode surface. These metal deposits catalyze the decomposition of the electrolyte on the negative electrode surface, destroying the original SEI film and causing a new SEI film to continuously grow, constantly consuming lithium and electrolyte, increasing the battery's internal resistance and causing capacity decay. Moreover, the electrolyte itself contains trace amounts of HF. The HF produced by the decomposition of the positive electrode electrolyte increases the HF content in the electrolyte. HF corrodes the SEI film of the negative electrode. The combination of HF corrosion and the rupture of the SEI film at high voltage results in uneven lithium ion deposition on the negative electrode surface, forming lithium dendrites. Lithium dendrites can puncture the separator, causing an internal short circuit, while continuously consuming electrolyte and active lithium, affecting battery capacity and cycle performance.

[0054] Meanwhile, the thermal stability of the positive electrode material decreases under high voltage. Furthermore, the rupture of the SEI film in the negative electrode material under high voltage consumes electrolyte and active material. Under the influence of high voltage, high temperature, and SEI film rupture, the electrolyte decomposes at an accelerated rate. The heat released by the decomposition of the electrolyte further decomposes the positive electrode material, forming a vicious cycle that leads to thermal runaway.

[0055] In view of this, this embodiment proposes an electrolyte for use in lithium-ion batteries. The electrolyte comprises: a lithium salt, a non-aqueous solvent, and additives; the additives include HFE458, compound I, and compound II; wherein the structure of compound I is shown in Formula I:

[0056]

[0057] Formula I.

[0058] The structure of compound II is shown in Formula II:

[0059]

[0060] Formula II.

[0061] Specifically, the Chinese name of compound I is: 1-cyclopropyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-1,2,4-triazole. The Chinese name of compound II is: 4-chloro-2-fluoro-5-sulfonamide benzonitrile.

[0062] The principle by which this embodiment achieves the above-mentioned beneficial effects will be explained in detail below:

[0063] As mentioned earlier, HF and trace amounts of water in the electrolyte corrode the positive electrode material, causing cobalt ions to dissolve from it. Simultaneously, HF also corrodes the SEI film on the negative electrode surface. The corrosion from HF, combined with the high-voltage environment, exacerbates the rupture of the SEI film, further accelerating the consumption of the electrolyte and active materials. Furthermore, cobalt ions from the positive electrode material can migrate to the negative electrode surface, affecting ion conductivity.

[0064] First, the boron atom (a strong Lewis acid) of the boronic acid ester group in compound I interacts with PF6 via an empty orbital. - The lone pair electrons form Lewis acid-base complexes, altering PF6 - The dissociation equilibrium is maintained, inhibiting the hydrolysis to generate HF and reducing the production of acidic substances at the source. At the same time, the nitrile group (-CN) and sulfonamide group (-SO2NH-) of compound II have Lewis basicity, which can efficiently capture trace amounts of H2O and HF in the electrolyte, preventing them from corroding the positive electrode material and catalyzing the decomposition of the electrolyte, while also reducing the erosion of the negative electrode SEI film by HF.

[0065] Secondly, Co 2+ As a typical Lewis acid, the boron atom of the boronic acid ester group in compound I (a strong Lewis acid) binds to Co via polydentate chelation. 2+ A stable chelate is formed, with the nitrogen atom (containing lone pair electrons) on the triazole ring reacting with the dissolved Co. 3+Coordination occurs, and the dual effect better anchors cobalt ions to the positive electrode surface; and the nitrile group of compound II can form a coordination structure with a small amount of free cobalt ions, further capturing the cobalt ions that are not completely fixed, preventing them from migrating and depositing to the negative electrode, and cutting off the chain reaction of capacity decay.

[0066] Therefore, through coordination / chelation with cobalt ions, compounds I and II anchor cobalt ions on the cathode surface, achieving uniform distribution of additive molecules and laying the foundation for uniform film formation of the subsequent CEI film. At the same time, the removal of acidic impurities avoids their interference with the formation of the interfacial film, creating a clean and stable film formation environment.

[0067] Under the above film-forming environment, HFE458, as a fluorinated ether additive, can significantly reduce the viscosity of the electrolyte, improve the wettability of the electrolyte to the positive and negative electrodes and the solubility of lithium salts, and ensure that additives such as Compound I and Compound II are uniformly penetrated into the electrode surface and pores, avoiding uneven film formation caused by local lack of liquid.

[0068] HFE458 preferentially undergoes controlled oxidative decomposition in the base solvent, generating fluorinated fragments that react with Li. + The two components combine to form a dense initial CEI film rich in LiF. LiF possesses high mechanical strength and chemical stability, which can initially block direct contact between the electrolyte and the positive electrode, inhibiting excessive oxidation of the electrolyte and damage to the positive electrode structure. Oxygen free radicals generated by oxidation on the positive electrode surface initiate the ring-opening polymerization of cyclopropyl in compound I, while triazole epoxidizes to generate nitrogen-containing polymers, and the two form a cross-linked structure. Compound I further decomposes to generate polymers rich in BO and BNC structures, as well as boron-containing inorganic components such as LiBO2 and Li3BO3. These products intertwine with the initial LiF film, improving the mechanical toughness and ion transport efficiency of the film layer.

[0069] Meanwhile, the sulfonamide group of compound II decomposes under oxidizing conditions to generate sulfur-containing oxides such as Li2SO4, and the nitrile group decomposes to generate nitrogen-containing compounds, which, together with the product of compound I, fill the micropores of the initial CEI membrane. At the same time, the fluorine atom in compound II reacts with the borooxy group (-BO-) in compound I to generate crystalline borates such as LiB6O9F, whose high stability further enhances the high-temperature adaptability of the CEI membrane.

[0070] Furthermore, on the negative electrode side, the reduction potential of HFE458 preferentially undergoes controlled reduction decomposition before the electrolyte's base solvent, generating an initial SEI film rich in LiF. This SEI film possesses high mechanical strength and electronic insulation, which can initially block excessive reactions between the electrolyte and the negative electrode, inhibiting lithium dendrite growth and solvent co-intercalation. Simultaneously, compound II adsorbs on the graphite surface of the negative electrode, regulating the interfacial charge distribution and promoting uniform SEI film growth. Its nitrile and sulfonylamino groups decompose under reducing conditions to generate sulfur / nitrogen compounds such as Li2S and Li3N, while fluorine atoms further generate LiF. These products can fill microporous defects in the initial HFE458 film, repair local damage, and improve the film's mechanical toughness and high-temperature stability. Compound I undergoes reduction decomposition at the negative electrode to generate nitrogen-containing compounds and boron-containing lithium salts (such as LiBO2), which intertwine and fuse with the decomposition products of compound II, forming a composite structure of a rigid LiF substrate, boron / fluorine-containing inorganic components, and an organic flexible framework. This composite structure can better buffer the volume changes of the graphite negative electrode during charging and discharging, preventing SEI film rupture while ensuring the LiF... + Rapid transport, balancing mechanical stability and ionic conductivity.

[0071] Thus, HFE458, Compound I, and Compound II work together to form high-performance CEI and SEI films, ensuring their mechanical strength, ion conductivity, and high-temperature stability, thereby guaranteeing the high-temperature storage performance, room-temperature and high-temperature cycling performance of lithium-ion batteries.

[0072] Further, the amount of HFE458 used in the electrolyte is 0.5-3.5%, based on the total mass of the electrolyte. For example, the amount of HFE458 used in the electrolyte includes, but is not limited to:

[0073] 0.5%, 0.6%, 0.7%, 0.76%, 0.8%, 0.85%, 0.9%, 1%, 1.1%, 1.14%, 1.28%, 1.3%, 1.4%, 1.46%, 1.5%, 1.53%, 1.56%, 1.72%, 1.77%, 1.8%, 1.85%, 1.9%, 2.0%, 2.03%, 2.05%, 2.07%, 2.1%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.12%, 3.16%, 3.19%, 3.25%, 3.28%, 3.34%, 3.36%, 3.37%, 3.4%, 3.45%, 3.5%.

[0074] Furthermore, the content of compound I is 0.5-5%, based on the total mass of the electrolyte. Exemplarily, the amount of compound I in the electrolyte includes, but is not limited to:

[0075] 0.5%, 0.55%, 0.6%, 0.66%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.22%, 1.25%, 1.28%, 1.3%, 1.4%, 1.43%, 1.49%, 1.5%, 1.54%, 1.57%, 1.76%, 1.8%, 1.85%, 1.9%, 2.0%, 2.01%, 2.03%, 2.05%, 2.07%, 2.1%, 2.2%, 2.26%, 2.4%, 2 0.5%, 2.6%, 2.8%, 3%, 3.1%, 3.13%, 3.17%, 3.24%, 3.28%, 3.32%, 3.36%, 3.4%, 3.47%, 3.52%, 3.54%, 3.59%, 3.6%, 3.63%, 3.7%, 3.75%, 3.82%, 3.85%, 3.87%, 3.91%, 3.94%, 4%, 4.1%, 4.2%, 4.41%, 4.5%, 4.6%, 4.7%, 4.9%, 5%.

[0076] Furthermore, the amount of compound II in the electrolyte is 1-5%, based on the total mass of the electrolyte.

[0077] The amount of compound II used in the electrolyte includes, but is not limited to:

[0078] 1%, 1.11%, 1.14%, 1.28%, 1.36%, 1.4%, 1.47%, 1.5%, 1.53%, 1.55%, 1.78%, 1.8%, 1.83%, 1.9%, 1.91%, 1.96%, 1.97%, 2%, 2.01%, 2.05%, 2.09%, 2.1%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.1%, 3.15% 3.19%, 3.25%, 3.28%, 3.32%, 3.36%, 3.38%, 3.4%, 3.47%, 3.52%, 3.54%, 3.59%, 3.6%, 3.63%, 3.7%, 3.75%, 3.82%, 3.85%, 3.87%, 3.91%, 3.94%, 4%, 4.1%, 4.2%, 4.41%, 4.5%, 4.6%, 4.7%, 4.9%, 5%.

[0079] In this embodiment, the above-mentioned additives can be purchased directly or prepared in-house; specifically, HFE458 (CAS No.: 16627-68-2), Compound I (CAS No.: 2813254-82-7), and Compound II (CAS No.: 27589-31-7) can be purchased directly. HFE458 was purchased from Hubei Wande Chemical Co., Ltd., Compound I from Shanghai Haohong Biomedical Technology Co., Ltd., and Compound II from Shanghai Yanze Chemical Co., Ltd.

[0080] Lithium salts.

[0081] As an essential component of the electrolyte in this embodiment, the lithium salt can be selected from salts commonly used in non-aqueous electrolytes suitable for lithium-ion batteries. Specifically, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, and lithium difluorosulfonylimide.

[0082] Preferably, lithium hexafluorophosphate (LiPF6) is selected as the lithium salt. However, when using multiple lithium salts, their content is not particularly limited as long as it does not significantly impair the effectiveness of this application.

[0083] In this embodiment, the lithium salt content is 5-20%, preferably 5-18%, more preferably 10-18%, and even more preferably 12-18%, based on the total mass of the electrolyte.

[0084] For example, the amount of the lithium salt used in the electrolyte includes, but is not limited to: 5%, 5.06%, 5.11%, 5.2%, 5.3%, 5.5%, 5.6%, 5.9%, 6%, 6.1%, 6.3%, 6.5%, 7%, 7.4%, 7.6%, 7.8%, 8%, 8.1%, 8.4%, 8.7%, 9%, 9.2%, 9.5%, 9.8%, 10%, 11%, 12%, 13%, 13.3%, 14%, 14.7%, 15%, 15.5%, 16%, 16.6%, 17%, 17.2%, 17.5%, 18%, 18.4%, 18.8%, 19%, 19.2%, 19.5%, 19.7%, and 20%.

[0085] The lithium salt used in this embodiment can be purchased directly or prepared by ourselves; specifically, lithium hexafluorophosphate was purchased from Chengdu McCarthy Chemical Co., Ltd.

[0086] Non-aqueous solvent.

[0087] The electrolyte in this embodiment is the same as that of a general non-aqueous electrolyte, and typically contains a non-aqueous solvent for dissolving the lithium salt as its main component.

[0088] There are no particular limitations on the non-aqueous solvents used herein, and known organic solvents may be used. Preferably, organic solvents are selected from saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, etc., but are not particularly limited to the above types. One, two, or more non-aqueous solvents may be used alone or in combination.

[0089] Specifically, as a preferred embodiment, the non-aqueous solvent is selected from at least one of carbonates, fluorocarbonates, carboxylic acid esters, fluorocarboxylic acid esters, ethers, and fluoroethers.

[0090] In a preferred embodiment, the non-aqueous solvent is selected from at least one of propylene carbonate, methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, difluoroethyl acetate, and ethyl 2,2,2-trifluoroethyl acetate. The content of the non-aqueous solvent is 66.5-93% based on the total mass of the electrolyte.

[0091] It should be understood that, in the electrolyte of this embodiment, apart from the lithium salt and additives, the remaining components are all non-aqueous solvents. Therefore, after determining the amount of lithium salt and additives, the content of non-aqueous solvents can also be expressed as a balance.

[0092] The non-aqueous solvents used in this embodiment can be purchased directly or prepared by the user. Specifically, ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0093] Other additives.

[0094] In addition to the various components listed above, the electrolyte of this application may reasonably employ other functional additives without significantly impairing the effectiveness of this application. For example, at least one of vinylidene sulfate, triallyl phosphate, and ethylene glycol bis(propionitrile) ether may be used. Specifically, triallyl phosphate may be used.

[0095] In this application, the content of other additives is 0.5-5%, preferably 0.5-3.5%, more preferably 0.5-2%, based on the total mass of the electrolyte.

[0096] For example, the amounts of the other additives used in the electrolyte include, but are not limited to: 0.5%, 0.53%, 0.55%, 0.59%, 0.6%, 0.64%, 0.68%, 0.7%, 0.73%, 0.77%, 0.8%, 0.82%, 0.88%, 0.9%, 0.93%, 0.96%, 1.0%, 1.3%, 1.6%, 1.7%, 1.8%, 1.88%, 1.9%, 1.97%, 2.0%, 2.3%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.5%, 3.6%, 3.64%, 3.7%, 3.76%, 3.87%, 3.91%, 3.94%, 4%, 4.1%, 4.2%, 4.31%, 4.4%, 4.5%, 4.8%, 4.9%, and 5%.

[0097] The additives used in this application can be purchased directly or prepared in-house; specifically, triallyl phosphate was purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0098] Next, the preparation method of the above electrolyte will be explained.

[0099] Preparation method.

[0100] The electrolyte of this application can be prepared using methods known in the art, for example:

[0101] In an argon atmosphere glove box with a water content of <10ppm, non-aqueous solvents are mixed in proportion, then fully dried lithium salts are dissolved in the mixed non-aqueous solvents, and then additives are added. After mixing evenly, an electrolyte is obtained.

[0102] This application does not impose any special limitations on the preparation method of the electrolyte.

[0103] Next, the lithium-ion secondary battery according to the second aspect of this embodiment will be described.

[0104] Lithium-ion secondary batteries.

[0105] The lithium-ion secondary battery includes: a positive electrode, a negative electrode, a separator, and the electrolyte described above. The operating voltage of the lithium-ion battery is 3.0-4.5V.

[0106] Positive electrode sheet.

[0107] The positive electrode used in the lithium-ion battery of this embodiment includes a positive current collector and a positive active material layer located at least on one side of the positive electrode, wherein the positive active material layer includes a positive active material.

[0108] In some embodiments, the positive current collector can be a metal current collector or a composite current collector. Among them, the metal current collector includes, but is not limited to, aluminum foil current collectors.

[0109] In some embodiments, the positive electrode active material of a lithium-ion battery may include at least one of the following: layered structure positive electrode active material (e.g., nickel-cobalt-manganese ternary positive electrode material, nickel-cobalt-aluminum ternary positive electrode material, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, etc.), olivine-type phosphate active material (e.g., lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.), and spinel structure positive electrode active material (e.g., spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide, etc.).

[0110] In this embodiment, LiCoO2 is used as the positive electrode.

[0111] In some embodiments, the binder in the positive electrode active material layer may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and terpolymer of PVDF-tetrafluoroethylene-propylene.

[0112] In some embodiments, the conductive agent in the positive electrode active material layer may be at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, carbon nanotubes, graphene, and carbon nanofibers.

[0113] Negative electrode sheet.

[0114] In some embodiments, the negative electrode sheet may include a negative current collector and a layer of negative active material disposed on at least one side of the surface of the negative current collector.

[0115] In some embodiments, the negative electrode active material layer may include a negative electrode active material, a thickener, a conductive agent, and a binder. The negative electrode current collector may be a metal foil, for example, a copper foil.

[0116] In some embodiments, the negative electrode active material may be a carbon-based material, a silicon-based material, a tin-based material, etc. For example, the negative electrode active material may be selected from one or more of soft carbon, hard carbon, and graphite. Graphite is preferred.

[0117] In some embodiments, the binder in the negative electrode material layer may be at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA), and polymethyl methacrylate (PMAA).

[0118] In some embodiments, the conductive agent in the negative electrode material layer may be at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, carbon nanotubes, graphene, and carbon nanofibers.

[0119] Diaphragm.

[0120] To prevent short circuits, a separator is typically sandwiched between the positive and negative electrode plates. This application does not impose any particular restrictions on the material or shape of the separator; any known separator can be used as long as it does not significantly impair the effectiveness of this application. Suitable materials include resins, glass fibers, and inorganic materials formed from materials that stabilize the lithium-ion electrolyte of this embodiment. Porous sheets or non-woven fabric-like materials with excellent liquid retention properties are preferred.

[0121] For example, polyethylene, polypropylene and other polyolefins, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. Among them, glass filters and polyolefins are preferred, and polyolefins are even more preferred.

[0122] Next, the electrical device of the third aspect of this embodiment will be described.

[0123] Electrical appliances.

[0124] It should be noted that the features and effects described for the lithium-ion battery in the second aspect of this embodiment are also applicable to this electrical device, and will not be repeated here.

[0125] In addition, it should be noted that the specific type of electrical device is not particularly limited, and those skilled in the art can choose flexibly according to actual needs, such as including but not limited to electronic devices (such as mobile phones, laptops, tablets, wearable devices, etc.) and vehicles (such as electric vehicles, electric cars, etc.).

[0126] The present application is further illustrated below with reference to 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.

[0127] Unless otherwise specified, all materials, reagents and instruments used in the following embodiments are commercially available.

[0128] The composition and content of the electrolytes in Examples 1-6 and Comparative Examples 1-7 are shown in Table 1 below.

[0129] Table 1: Components and contents (%) of electrolytes in Examples 1-6 and Comparative Examples 1-7

[0130] Components HFE458 Compound I Compound II TAP <![CDATA[LiPF6]]> non-aqueous solvents Example 1 0.5 1.5 5 - 13 margin Example 2 3.5 1.5 2 - 13 margin Example 3 2 2 3 - 13 margin Example 4 2.5 0.5 4 - 13 margin Example 5 1 5 1 - 13 margin Example 6 2 2 3 0.5 13 margin Comparative Example 1 - - - - 13 margin Comparative Example 2 2 - - - 13 margin Comparative Example 3 - 2 - - 13 margin Comparative Example 4 - - 3 - 13 margin Comparative Example 5 2 2 - - 13 margin Comparative Example 6 2 - 3 - 13 margin Comparative Example 7 - 2 3 - 13 margin

[0131] In Table 1, the total content of all components is 100%, and the non-aqueous solvent is composed of ethylene carbonate (EC), propylene trifluorocarbonate (PC), and propyl propionate (PP) in a mass ratio of 1:1:1.

[0132] Preparation of electrolyte: In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate (EC), propylene trifluorocarbonate (PC), and propyl propionate (PP) were mixed in a mass ratio of EC:PC:PP=1:1:1. Then, fully dried lithium salt LiPF6 was dissolved in the mixed non-aqueous solvent. HFE458, compound I, compound II, and TAP (if any) were then added and mixed thoroughly to obtain the electrolyte.

[0133] The electrolytes prepared in Examples 1-6 and Comparative Examples 1-7 were used to prepare the corresponding lithium-ion batteries, specifically including:

[0134] (1) Preparation of positive electrode sheet:

[0135] LiCoO2, conductive agent SuperP, binder PVDF, and carbon nanotubes (CNTs) were mixed in a mass ratio of 96.5:1:1.5:1. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum to prepare a uniform lithium-ion battery positive electrode slurry. The positive electrode slurry was then uniformly coated onto an aluminum foil with a thickness of approximately 12 μm, with a coating weight of 0.033 g / cm³. 2 The material is dried in an 85°C oven for 4 hours, and then cold-pressed and die-cut to form a positive electrode sheet.

[0136] (2) Preparation of negative electrode sheet:

[0137] Graphite was mixed with conductive agent SuperP, thickener CMC, and binder SBR (styrene-butadiene rubber latex) at a mass ratio of 95:1.5:1:2.5. Deionized water was added, and the mixture was stirred evenly under vacuum. The resulting slurry was then uniformly coated onto a copper foil with a thickness of approximately 12 μm, with a coating weight of 0.0225 g / cm³. 2 The material is dried in a forced-air oven at 85°C for 4 hours, and then cold-pressed and slit to obtain the negative electrode sheet.

[0138] (3) Preparation of the separating membrane:

[0139] A 10μm thick polyethylene film (purchased from Celgard) was selected.

[0140] (4) Preparation of lithium-ion secondary batteries:

[0141] The positive electrode, separator, and negative electrode prepared above are sequentially stacked to form a stacked assembly, wherein the thickness of the stacked assembly is 4.6 mm, the width is 55 mm, and the length is 60 mm. The stacked assembly is baked under vacuum conditions and at 75°C for 12 hours, and then the electrolyte prepared above is injected. After vacuum sealing, standing, formation, final sealing, and capacity testing, a lithium-ion secondary battery is obtained.

[0142] Battery performance testing.

[0143] The lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1-7 were subjected to the following performance tests, and the test results are shown in Table 2.

[0144] (1) Cyclic performance test at room temperature or high temperature:

[0145] The lithium-ion battery was placed in a constant temperature chamber at 25°C or 45°C and charged to 4.5V with a constant current and constant voltage of 1C (cutoff current is 0.05C). After the battery was fully charged, it was left to stand for 5 minutes, and then discharged to 3.0V with a constant current of 1C. The discharge capacity after the first cycle was recorded. After 500 charge / discharge cycles, the capacity retention rate of the lithium-ion battery was measured.

[0146] The formula for calculating the capacity retention rate of a battery after the Nth cycle is:

[0147] Capacity retention rate after Nth cycle = Discharge capacity after Nth cycle / Discharge capacity after first cycle × 100%.

[0148] (2) High-temperature storage performance test:

[0149] At 25°C, the lithium-ion battery is charged to 4.5V at a constant current of 1.0C, then charged to a cutoff current of 0.05C at a constant voltage of 4.5V. The battery is then discharged to 3.0V at a constant current of 1.0C. The discharge capacity is recorded as C0.

[0150] At 25°C, the lithium-ion battery was charged at a constant current of 1.0C to 4.5V, and then charged at a constant voltage of 4.5V until the cutoff current of 0.05C. The lithium-ion battery was then transferred to a 60°C constant temperature chamber and stored for 30 days. After the storage period, the lithium-ion battery was removed and cooled to room temperature. At 25°C, the battery was discharged at a constant current of 1.0C to 3.0V, and the discharge capacity was recorded as C1. The high-temperature storage capacity retention rate of the lithium-ion battery was determined.

[0151] The formula for calculating the high-temperature storage capacity retention rate is: High-temperature storage capacity retention rate (%) = C1 / C0 × 100%.

[0152] Each performance test involved testing three batteries in parallel and taking the average value as the test result.

[0153] Table 2: Test results (%) of lithium ions for Examples 1-6 and Comparative Examples 1-7

[0154] Test group ambient temperature cycling performance High temperature cycling performance High-temperature storage performance Example 1 90.4 88.1 86.9 Example 2 90.8 88.5 87.8 Example 3 91.4 89.8 88.9 Example 4 89.9 86.9 85.8 Example 5 90.5 87.4 86.4 Example 6 92.6 91.1 89.7 Comparative Example 1 35.8 32.9 31.2 Comparative Example 2 46.8 42.8 43.3 Comparative Example 3 59.4 55.7 54.1 Comparative Example 4 54.6 53.8 52.9 Comparative Example 5 71.1 70.8 68.8 Comparative Example 6 77.4 75.5 73.6 Comparative Example 7 74.2 72.7 70.8

[0155] According to the test results in Table 2, compared with Comparative Example 1 (blank control group), Examples 1-6 significantly improved the high-temperature storage performance, room temperature and high-temperature cycling performance of lithium-ion batteries by adding HFE458, Compound I and Compound II as additives to the lithium-ion battery electrolyte.

[0156] Furthermore, Example 6 adds TAP to Example 3, which can effectively improve the high-temperature storage performance, room temperature and high-temperature cycling performance of lithium-ion batteries based on Example 3.

[0157] By comparing Example 3 with Comparative Examples 2-4, Comparative Example 2 only added HFE458, Comparative Example 3 only added Compound I, and Comparative Example 4 only added Compound II. The room temperature cycling performance of Comparative Examples 2-4 was 46.8%, 59.4%, and 54.6%, respectively; the high temperature cycling performance of Comparative Examples 2-4 was 42.8%, 55.7%, and 53.8%, respectively; and the high temperature storage performance of Comparative Examples 2-4 was 43.3%, 54.1%, and 52.9%, respectively. This shows that using HFE458 alone, or Compound I or Compound II alone, can only improve the high temperature storage performance, room temperature performance, and high temperature cycling performance of lithium-ion batteries to a limited extent compared to the blank control group.

[0158] For Comparative Example 2, the addition of HFE458 alone only resulted in limited improvements in high-temperature storage performance and cycling performance at both room temperature and high temperature compared to the blank control. This may be because, without compounds I and II, trace amounts of H2O and HF cannot be effectively removed, disrupting the interfacial film formation environment and preventing the formation of a sufficiently good interfacial film. Furthermore, HFE458 alone cannot effectively complex and anchor transition metals. Moreover, the CEI and SEI films formed by HFE458 do not possess sufficiently good mechanical properties and ionic conductivity. Therefore, the performance of the lithium-ion battery prepared with the electrolyte containing only HFE458 showed only limited improvement compared to the blank control.

[0159] As for Comparative Example 3, the addition of only Compound I resulted in only a limited improvement in high-temperature storage performance and cycling performance at both room temperature and high temperature compared to the blank control. This may be because, without HFE458 and Compound II, Compound I cannot form a uniform film on both the positive and negative electrodes in the absence of HFE458. Furthermore, due to the lack of HFE458 and Compound II, Compound I cannot simultaneously achieve film formation and cobalt ion anchoring, thus failing to effectively prevent the dissolution of cobalt ions. Consequently, the formed CEI film also cannot effectively prevent the dissolution of the positive electrode material metal. Therefore, the performance of the lithium-ion battery prepared with the electrolyte containing only Compound I showed only a limited improvement compared to the blank control.

[0160] As for Comparative Example 4, the addition of only Compound II only resulted in limited improvements in high-temperature storage performance and cycling performance at both room temperature and high temperature compared to the blank control. This may be because, without HFE458 and Compound I, Compound II cannot form a uniform film on both the positive and negative electrodes due to the lack of HFE458. Furthermore, due to the absence of HFE458 and Compound I, Compound II cannot simultaneously achieve film formation and cobalt ion anchoring, and the CEI film formed by Compound II cannot effectively prevent cobalt ion migration, making the SEI film more susceptible to damage. Therefore, the performance of the lithium-ion battery prepared with the electrolyte containing only Compound II showed only limited improvement compared to the blank control.

[0161] Further comparison of Example 3 with Comparative Examples 5, 6 and 7 revealed that, compared to Example 3, Comparative Example 5 lacked Compound II, Comparative Example 6 lacked Compound I, and Comparative Example 7 lacked HFE458. The high-temperature storage performance, room temperature and high-temperature cycling performance of the lithium-ion batteries of Comparative Examples 5, 6 and 7 all decreased to varying degrees.

[0162] For Comparative Example 5, which lacks Compound II, its high-temperature storage performance and room-temperature and high-temperature cycling performance only showed limited improvement compared to the blank control. This may be because Comparative Example 5 lacks Compound II. Without one of the additives capable of capturing trace amounts of H2O and HF in the electrolyte, as well as coordinating with cobalt ions, the additive composition of Comparative Example 5 cannot efficiently capture trace amounts of H2O and HF, nor can it effectively anchor free cobalt ions in the electrolyte system. Therefore, it cannot effectively mitigate the erosion of the SEI film by HF, nor can it effectively prevent the migration of cobalt ions to the negative electrode. This results in varying degrees of decline in the high-temperature storage performance, room-temperature performance, and high-temperature cycling performance of the battery corresponding to the electrolyte of Comparative Example 5.

[0163] For Comparative Example 6, which lacks compound I, its high-temperature storage performance and cycling performance at both room temperature and high temperature are only limitedly improved compared to the blank control. This may be because the absence of compound I means that the additive composition of Comparative Example 6 lacks a compound that can inhibit PF6. - Additives that can be hydrolyzed and anchored to cobalt ions prevent the additive composition in Comparative Example 6 from effectively inhibiting PF6. - Hydrolysis results in a higher concentration of trace amounts of H2O and HF in the electrolyte, which cannot be completely suppressed by compound II alone. This makes both the positive and negative electrodes susceptible to corrosion. The corrosion of the positive electrode leads to the continued dissolution of cobalt ions into the electrolyte system. However, due to the lack of compound I, compound II alone cannot efficiently anchor these free cobalt ions, thus failing to effectively prevent the migration of metal ions to the negative electrode, further damaging the SEI film. Ultimately, this results in varying degrees of decline in the high-temperature storage performance, room-temperature performance, and high-temperature cycling performance of the battery corresponding to the electrolyte in Comparative Example 6.

[0164] For Comparative Example 7, lacking HFE458, its high-temperature storage performance and room-temperature and high-temperature cycling performance only showed limited improvement compared to the blank control. This resulted in highly active solvent molecules in the electrolyte coming into direct contact with the positive electrode, leading to low antioxidant capacity of the electrolyte. Simultaneously, the absence of HFE458 prevented the provision of a uniform reaction substrate for Compound I and Compound II, causing varying degrees of decline in the high-temperature storage performance, room-temperature and high-temperature cycling performance of the battery corresponding to the electrolyte of Comparative Example 7.

[0165] In summary, this embodiment incorporates HFE458, Compound I, and Compound II as additives into the electrolyte. Compound I and Compound II remove trace amounts of H2O and HF and coordinate / chelate cobalt ions, providing a stable interfacial environment for the subsequent uniform formation of the CEI film. Meanwhile, HFE458 film formation inhibits cobalt ion dissolution, preventing the oxidation of lithium salts and positive and negative electrode materials in the electrolyte under high voltage. This provides a stable interfacial environment for the other two additives to supplement and repair the initial CEI and SEI films. In other words, through the synergy of HFE458, Compound I, and Compound II, a uniform and stable CEI and SEI film are generated. Simultaneously, the mechanical toughness and ion transport efficiency of the positive and negative electrode dual-interface films are optimized, effectively preventing the CEI and SEI films from being damaged under high voltage, thus avoiding damage to the positive and negative electrode material structures. This significantly improves the high-temperature storage stability, room-temperature and high-temperature cycling performance of the lithium-ion battery.

[0166] Therefore, the electrolyte in this embodiment can significantly improve the high-temperature storage performance, room-temperature and high-temperature cycling performance of lithium-ion batteries.

[0167] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used in this document to illustrate the principles and implementation methods of the embodiments of this application. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrolyte, characterized by, The electrolyte comprises: a lithium salt, a non-aqueous solvent, and an additive; the additive comprises 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a compound having a structure shown in Formula I, and 4-chloro-2-fluoro-5-sulfonamidobenzonitrile: ； Formula I.

2. The electrolyte according to claim 1, characterized in that, The content of the 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 0.5-3.5% based on the total mass of the electrolyte.

3. The electrolyte of claim 1, wherein The content of the compound having a structure shown in Formula I is 0.5-5% based on the total mass of the electrolyte.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The content of the 4-chloro-2-fluoro-5-sulfonamidobenzonitrile is 1-5% based on the total mass of the electrolyte.

5. The electrolyte of claim 1, wherein The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, and lithium bis(fluorosulfonyl)imide. The content of the lithium salt is 5-20% based on the total mass of the electrolyte.

6. The electrolyte of claim 1, wherein The non-aqueous solvent is selected from at least one of carbonates, fluorinated carbonates, carboxylic acid esters, fluorinated carboxylic acid esters, ethers, and fluorinated ether solvents.

7. The electrolyte according to claim 1 or 6, characterized in that, The non-aqueous solvent is selected from at least one of propylene carbonate, methyl ethyl carbonate, vinyl carbonate, dimethyl carbonate, diethyl carbonate, fluorinated vinyl carbonate, γ-butyrolactone, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, difluoroethyl acetate, and ethyl 2,2,2-trifluoroacetate. The content of the non-aqueous solvent is 66.5-93% based on the total mass of the electrolyte.

8. The electrolyte of claim 1, wherein, The electrolyte further comprises other additives; The other additives further comprise at least one of vinylene sulfite, triallyl phosphate, 1,3,6-hexanetricarbonitrile, ethylene glycol bis(propionitrile) ether, and adiponitrile. The content of the other additives is 0.5-5% based on the total mass of the electrolyte.

9. A lithium-ion battery, characterized by The lithium ion battery comprises: a positive electrode sheet; a negative electrode sheet; a separator; and the electrolyte according to any one of claims 1-8.

10. The lithium-ion battery of claim 9, wherein, The positive electrode plate includes a positive electrode active material; the positive electrode active material includes at least one of LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, Li 1+a Mn 1-y MyO2, LiCo 1-y MyO2, LiFe 1-y M y PO4, and Li2Mn 1-y M y O4. wherein M is selected from one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, and Ti, 0≤a<0.2, and 0≤y<1; The working voltage of the lithium ion battery is 3.0-4.5 V.

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