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, an isocyanate compound and a compound with a structure as shown in a formula I which is described in the specification. According to the embodiment of the invention, 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether, the isocyanate compound and the compound with the structure as shown in the formula I 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 devices, energy storage, and power applications. Among them, lithium cobalt oxide batteries were the first lithium-ion batteries to be commercially applied. They are characterized by high energy density and are commonly used in portable electronic devices.

[0003] The maximum charging cutoff voltage of conventional lithium cobalt oxide batteries is around 4.3V. When the voltage exceeds 4.3V, for example, when it is increased to 4.5V, the positive electrode of lithium cobalt oxide will experience irreversible bulk phase problems. At the same time, severe interfacial side reactions will occur on the surfaces of both the positive and negative electrodes, leading to a sharp decline in the performance of lithium cobalt oxide batteries.

[0004] Therefore, how to improve the electrochemical performance of lithium cobalt oxide batteries under high voltage has become an urgent problem to be solved. 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, isocyanate compounds, and compounds with the structure shown in Formula I:

[0012]

[0013] Formula I.

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

[0015] In one embodiment, the isocyanate compound includes at least one selected from terephthalic diisocyanate, toluene-2,4-diisocyanate, and 4,4'-diisocyanate dicyclohexylmethane;

[0016] The content of the isocyanate compound is 1.5-5%, based on the total mass of the electrolyte.

[0017] In one embodiment, the content of the compound is 0.5-3%, based on the total mass of the electrolyte.

[0018] 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.

[0019] The lithium salt content is 5-20%, based on the total mass of the electrolyte.

[0020] 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.

[0021] 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.

[0022] The content of the non-aqueous solvent is 69-92.5%, based on the total mass of the electrolyte.

[0023] In one embodiment, the electrolyte also includes other additives;

[0024] The other additives also include at least one of vinylene sulfate, triallyl phosphate, and ethylene glycol bis(propionitrile) ether;

[0025] The content of the other additives is 0.5-3.5%, based on the total mass of the electrolyte.

[0026] Secondly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising:

[0027] Positive electrode sheet;

[0028] Negative electrode plate;

[0029] Diaphragm; and

[0030] The electrolyte described in the first aspect.

[0031] 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, LiCo 1-y MyO2, LiFe 1-y M y PO4 and Li2Mn 1-y M y At least one of O4;

[0032] 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;

[0033] The lithium-ion battery operates at a voltage of 3.0-4.5V.

[0034] Compared with the prior art, the embodiments of this application have at least the following beneficial effects:

[0035] In this embodiment, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, isocyanate compounds, and compounds with the structure shown in Formula I are added to the electrolyte as additives. Through the combination of these three additives, an interface environment conducive to the formation of CEI and SEI films is constructed, resulting in CEI and SEI films with higher ionic conductivity, chemical stability, and density. Side reactions such as cobalt ion dissolution and electrolyte decomposition are suppressed. At the same time, the performance of the positive and negative electrode dual interface films is optimized, which can effectively prevent the CEI film from being damaged under high voltage and thus prevent the positive electrode material structure from being damaged. This significantly improves the high-temperature storage stability, room temperature and high-temperature cycling performance of lithium-ion batteries.

[0036] 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

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Below, we will first explain some of the terms and materials used in this embodiment to facilitate understanding by those skilled in the art.

[0041] HFE458: 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropyl ether.

[0042] Compound I: A compound with the structure shown in Formula I.

[0043] HMDI: 4,4'-Dicyclohexylmethane diisocyanate.

[0044] DENE: Ethylene glycol bis(propionitrile) ether.

[0045] LCO: Lithium cobalt oxide.

[0046] The electrolyte and lithium-ion battery of this application are described in detail below.

[0047] First, the electrolyte of the first aspect of this embodiment will be described.

[0048] Electrolyte.

[0049] As those skilled in the art will know, the quality of the CEI film directly determines the cycle life, safety, and high-voltage performance of a battery. The CEI film protects the cathode material, inhibits structural collapse and transition metal ion dissolution of the cathode material (such as lithium cobalt oxide and lithium iron phosphate) during charge and discharge, prevents the continuous decomposition of the electrolyte at high voltages (especially above 4.3V), reduces gas generation, and avoids battery swelling. In high-voltage batteries, a high-quality CEI film can withstand higher potentials and is key to achieving high energy density.

[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 battery performance.

[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 is easily dissolved from the crystal lattice into the electrolyte, further damaging the cathode material structure and causing capacity decay.

[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, increasing 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 decrease in the high-temperature storage performance of the lithium-ion battery. In addition, the instability of the positive electrode CEI film can also cause corrosion of the negative electrode. On one hand, cobalt ions dissolved in the electrolyte continuously 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, leading to uneven deposition of lithium ions on the negative electrode surface, forming lithium dendrites. Lithium dendrites can pierce the separator, causing internal short circuits, while continuously consuming electrolyte and active lithium, affecting battery capacity and cycle performance.

[0054] Meanwhile, under high voltage, the thermal stability of the cathode material decreases, and the electrolyte decomposes more rapidly under the influence of high voltage and high temperature. The heat released by the decomposition of the electrolyte will further decompose the cathode 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 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, isocyanate compounds, and compounds with the structure shown in Formula I.

[0056]

[0057] Formula I.

[0058] In this embodiment, compound I is selected as the core additive; this compound is 4-propyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-thione, which contains a thione group, a phosphorus heterocyclic structure, and a propyl side chain (-C3H7). First, on the positive electrode side, the thione group can react with oxygen free radicals on the surface of lithium cobalt oxide under high voltage (e.g., >4.4 V). The sulfur atom of the thione captures oxygen free radicals (e.g., O2) through nucleophilic substitution. - The sulfur oxides (such as Li2SO4) are generated and embedded in the positive electrode CEI film; the decomposition products of thionone can replace some of the released O2. - This process repairs lattice defects on the lithium cobalt oxide surface and inhibits the dissolution of the transition metal cobalt. Simultaneously, the sulfur-containing CEI film not only reduces interfacial impedance and improves ionic conductivity, but also facilitates a more thorough and uniform polymerization reaction of isocyanates and the film-forming reaction of fluoroethers. Furthermore, during the initial charging process, the thionyl groups can undergo reductive decomposition at low potential on the negative electrode surface, generating sulfur-containing compounds including inorganic components such as Li₂S and Li₂SO₃, and organic sulfides such as ROSO₂Li. The cross-linked structure of these sulfur-containing compounds enhances the toughness of the SEI film and reduces interfacial impedance, inhibiting lithium dendrite penetration. It can also form a physical barrier between graphite layers, preventing graphite layer peeling caused by the co-intercalation of solvent molecules such as EC and PC.

[0059] Furthermore, the phosphorus-oxygen double bond (P=O) in the decomposition product of compound I acts as a Lewis base and can react with Co. 3+ Coordination, capturing free Co in the electrolyte 3+ A stable complex is formed, preventing it from migrating to the negative electrode and damaging the SEI film, thus ensuring the long-term effectiveness of the SEI film.

[0060] The following will further explain the relevant principles of how the above-mentioned additives can work together to improve the performance of lithium-ion batteries in this embodiment.

[0061] Those skilled in the art will know that trace amounts of H2O and HF in the electrolyte can trigger the hydrolysis of lithium salts (such as lithium hexafluorophosphate), corrode the positive and negative electrode materials, and disrupt the interfacial film formation environment. In this embodiment, the isocyanate group (-NCO) in the isocyanate compound has a strong affinity for proton-containing substances (H2O, HF), enabling rapid reaction and targeted removal of impurities. Simultaneously, in compound I, the rigid bicyclic structure of the phosphorus heterocycle exhibits significant ring strain, and the P atom is connected to a strongly electron-withdrawing S atom via a phosphorus-sulfur double bond (P=S), resulting in a decrease in the electron cloud density of the P atom and enhanced electrophilicity, endowing the phosphorus heterocycle with extremely high reactivity with the P=S bond. This active site preferentially reacts with HF before the basic solvent (such as EC) and lithium salt (such as LiPF6) in the electrolyte. The P=S bond undergoes a nucleophilic substitution reaction to generate stable fluorinated phosphooxyphosphates (such as LiPF3O, Li2PO2F) and sulfofluorides (such as LiSF3), achieving targeted HF removal. Furthermore, the POC bond of the phosphorus heterocycle exhibits selective hydrolytic activity towards H2O. Under the influence of ring strain in the presence of trace amounts of water in the electrolyte, it undergoes controlled ring-opening hydrolysis, breaking the PO bond on the ring to generate linear phosphorus compounds containing hydroxyl groups (-OH). This further consumes H2O to enhance the impurity removal effect, and the hydroxyl groups in the hydrolysis products can also provide initiation sites for the subsequent polymerization reaction of isocyanate compounds. Based on the combined effect of isocyanate compounds and compound I, the H2O and HF content in the electrolyte can be significantly reduced, avoiding the decrease in lithium-ion concentration caused by lithium salt hydrolysis and preventing corrosion of the cathode material. At the same time, it eliminates the oxidation side reaction of water under high voltage (generating O2 and HF), laying the foundation for the formation of subsequent CEI and SEI films.

[0062] Secondly, on the positive electrode side, HFE458 can accumulate at the high-voltage interface, regulating the formation process of the initial CEI film. Its decomposition products help form a dense initial CEI film rich in LiF, effectively inhibiting the continuous decomposition of the electrolyte and structural damage to the lithium cobalt oxide material. Simultaneously, the addition of HFE458 significantly reduces the viscosity of the electrolyte, assisting the solvent in the electrolyte to dissolve lithium salts and other additives, improving the wettability of the electrolyte to both the positive and negative electrodes, ensuring that isocyanate compounds and additives such as Compound I are uniformly distributed on the electrode surface and in the pores, avoiding uneven film formation caused by localized electrolyte deficiency, and creating favorable conditions for the uniform film formation of subsequent additives. Next, the hydroxyl groups generated by the hydrolysis and ring-opening decomposition of Compound I and the hydroxyl groups remaining on the positive electrode surface can provide initiation sites for the polymerization of isocyanate compounds. The isocyanate compounds undergo stepwise polymerization on the positive electrode surface, generating polyurea / polyurethane polymers. This polymer exhibits good flexibility and interweaves with the LiF inorganic layer formed by the fluoroether, significantly enhancing the mechanical toughness and deformation resistance of the CEI membrane and preventing its rupture during high-voltage cycling. Simultaneously, compound I undergoes ring-opening decomposition at high voltage (approximately 4.4 V), generating sulfur- and phosphorus-containing products (such as lithium phosphate and organosulfur compounds). Lithium phosphate possesses high ionic conductivity, while organosulfur compounds can construct flexible ion transport channels. The synergistic integration of these two into the formed CEI membrane further improves its ionic conductivity and chemical stability.

[0063] Understandably, the aforementioned stable composite CEI membrane can physically block direct contact between the positive electrode and the electrolyte, reducing lattice oxygen release and decreasing metal ion dissolution at the source; for the small amount of dissolved free Co... 3+ The isocyanate group affects the dissolved free Co 3+ It has strong complexing ability; the phosphorus-oxygen double bond (P=O) in the decomposition product of compound I can act as a Lewis base and react with Co. 3+ Coordination, the two work together to capture free Co 3+ It forms a stable complex, preventing it from migrating to the negative electrode and damaging the SEI film, thus interrupting the chain reaction of capacity decay.

[0064] On the negative electrode side, the perfluorinated molecular structure of HFE458 results in weak solvation capability. This weak solvation characteristic reduces direct contact between highly reactive solvent molecules (such as EC) and the negative electrode surface, lowering the probability of excessive solvent reduction and decomposition, and preventing the SEI film from becoming too thick and having excessively high impedance due to excessive solvent decomposition. Simultaneously, HFE458 reduces side reactions of the electrolyte on the negative electrode surface, maintaining a stable interfacial environment during film formation, which is beneficial for the film formation process of isocyanate compounds and Compound I. Compound I undergoes initial reduction and decomposition at the low potential of the negative electrode, rapidly forming an inorganic SEI film containing Li2S-Li3PO4 on the negative electrode surface. This SEI film forms the basis for high ionic conductivity and mechanical strength. Subsequently, using the hydroxyl groups generated from the hydrolysis and ring-opening decomposition of Compound I, and the hydroxyl groups remaining on the negative electrode surface as initiation sites, the polyurea / polyurethane polymer generated by the reduction polymerization of isocyanate compounds can uniformly cover the surface of the inorganic SEI film and embed into the inorganic layer to form an organic flexible framework. This framework interweaves and fuses with the inorganic layer, balancing the rigidity and flexibility of the film. The propyl side chain of compound I decomposes to generate organic products such as propyl lithium (C3H7Li). The flexibility of its organic chain can buffer volume changes, and at the same time, it interacts with the isocyanate polymer to fill the pores, thereby improving the compactness and deformation resistance of the SEI film.

[0065] Therefore, this embodiment constructs an interface environment conducive to the formation of CEI and SEI films, generates CEI and SEI films with higher ionic conductivity, chemical stability and density, and suppresses side reactions such as cobalt ion dissolution and electrolyte decomposition. At the same time, it optimizes the performance of the positive and negative electrode dual interface films, which can effectively prevent the CEI film from being damaged under high voltage and thus prevent the positive electrode material structure from being damaged. This significantly improves the high-temperature storage stability, room temperature and high-temperature cycling performance of lithium-ion batteries.

[0066] Further, the amount of HFE458 used in the electrolyte is 0.5-3%, based on the total mass of the electrolyte. Exemplarily, the amount of HFE458 used in the electrolyte includes, but is not limited to:

[0067] 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%.

[0068] Furthermore, the amount of the isocyanate compound in the electrolyte is 1.5-5%, based on the total mass of the electrolyte.

[0069] Preferably, the isocyanate compound is selected from diisocyanate compounds. Since diisocyanate compounds contain two isocyanate groups, at the same addition amount, the number of isocyanate groups contained in diisocyanate compounds is greater than that in isocyanate compounds containing only one isocyanate group.

[0070] More specifically, the isocyanate compound includes at least one selected from terephthalic diisocyanate, toluene-2,4-diisocyanate, and 4,4'-diisocyanate dicyclohexylmethane. Exemplarily, this embodiment uses HMDI (4,4'-diisocyanate dicyclohexylmethane) as an example. Specifically, the amount of HMDI used in the electrolyte in this embodiment includes, but is not limited to:

[0071] 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%.

[0072] Understandably, HMDI undergoes an irreversible, rapid nucleophilic addition reaction with trace amounts of water and HF in the electrolyte. This reaction eliminates HF at its source, greatly reducing the corrosion of the LCO cathode and the damage to the SEI of the anode by HF.

[0073] Furthermore, the content of compound I is 0.5-3%, based on the total mass of the electrolyte. Exemplarily, the amount of compound I in the electrolyte includes, but is not limited to:

[0074] 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%, 2.5%, 2.6%, 2.8%, 3%.

[0075] In this embodiment, the above-mentioned additives can be purchased directly or prepared in-house; specifically, HFE458 (CAS No.: 16627-68-2) and HMDI (CAS No.: 5124-30-1) can be purchased directly. HFE458 was purchased from Hubei Wande Chemical Co., Ltd., and HMDI was purchased from Shandong Mingde Biotechnology Co., Ltd. Compound I (CAS No.: 51486-54-5) can be prepared in-house.

[0076] Lithium salts.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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%.

[0081] 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.

[0082] Non-aqueous solvent.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 69-92.5% based on the total mass of the electrolyte.

[0087] 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.

[0088] 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.

[0089] Other additives.

[0090] 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 vinylene sulfate, triallyl phosphate, and ethylene glycol bis(propionitrile) ether may be used. Specifically, ethylene glycol bis(propionitrile) ether may be used.

[0091] In this application, the content of other additives is 0.5-3.5%, preferably 0.8-3.5%, more preferably 1-3.5%, based on the total mass of the electrolyte.

[0092] 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%, and 3.5%.

[0093] The additives used in this application can be purchased directly or prepared in-house; specifically, ethylene glycol bis(propionitrile) ether was purchased from Shandong Xiya Chemical Co., Ltd.

[0094] Next, the preparation method of the above electrolyte will be explained.

[0095] Preparation method.

[0096] The electrolyte of this application can be prepared using methods known in the art, for example:

[0097] 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.

[0098] This application does not impose any special limitations on the preparation method of the electrolyte.

[0099] Next, the lithium-ion secondary battery according to the second aspect of this embodiment will be described.

[0100] Lithium-ion secondary batteries.

[0101] 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.

[0102] Please refer to the description of the first aspect. Since the lithium-ion secondary battery of this embodiment contains the above-mentioned electrolyte, the lithium-ion battery of this embodiment has a wider operating voltage range and a higher charging cut-off voltage (4.5V).

[0103] Positive electrode sheet.

[0104] 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.

[0105] 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.

[0106] 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.).

[0107] In this embodiment, LiCoO2 is used as the positive electrode.

[0108] 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.

[0109] 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.

[0110] Negative electrode sheet.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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).

[0115] 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.

[0116] Diaphragm.

[0117] 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.

[0118] 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.

[0119] Next, the electrical device of the third aspect of this embodiment will be described.

[0120] Electrical appliances.

[0121] 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.

[0122] 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.).

[0123] 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.

[0124] Unless otherwise specified, all materials, reagents and instruments used in the following embodiments are commercially available.

[0125] The following examples use a lithium-ion battery with LiCoO2 as the positive electrode active material to verify the electrolyte of this embodiment.

[0126] The composition and content of the electrolytes in Examples 1-8 and Comparative Examples 1-7 are shown in Table 1 below.

[0127] Table 1: Components and contents (%) of electrolytes in Examples 1-8 and Comparative Examples 1-7

[0128] Components HFE458 Compound I HMDI terephthalic diisocyanate Toluene-2,4-diisocyanate DENE <![CDATA[LiPF6]]> non-aqueous solvents Example 1 0.5 5 1.5 - - - 13 margin Example 2 2.4 4.1 0.5 - - - 13 margin Example 3 1.8 3.4 1.8 - - - 13 margin Example 4 1.3 2.7 3 - - - 13 margin Example 5 3 1.5 2.5 - - - 13 margin Example 6 1.8 3.4 - 1.8 - - 13 margin Example 7 1.8 3.4 - - 1.8 - 13 margin Example 8 1.8 3.4 1.8 - - 1 13 margin Comparative Example 1 - - - - - - 13 margin Comparative Example 2 1.8 - - - - - 13 margin Comparative Example 3 - 3.4 - - - - 13 margin Comparative Example 4 - - 1.8 - - - 13 margin Comparative Example 5 - 3.4 1.8 - - - 13 margin Comparative Example 6 1.8 3.4 - - - - 13 margin Comparative Example 7 1.8 - 1.8 - - - 13 margin

[0129] 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.

[0130] 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, HMDI / terephthalic diisocyanate / toluene-2,4-diisocyanate, and DENE (if any) were added and mixed thoroughly to obtain the electrolyte.

[0131] The electrolytes prepared in Examples 1-8 and Comparative Examples 1-7 were used to prepare the corresponding lithium-ion batteries, specifically including:

[0132] (1) Preparation of positive electrode sheet:

[0133] 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 0.032 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.

[0134] (2) Preparation of negative electrode sheet:

[0135] 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 0.0226 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.

[0136] (3) Preparation of the separating membrane:

[0137] A 10μm thick polyethylene film (purchased from Celgard) was selected.

[0138] (4) Preparation of lithium-ion secondary batteries:

[0139] 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 57 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.

[0140] Battery performance testing.

[0141] 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.

[0142] (1) Cyclic performance test at room temperature or high temperature:

[0143] 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.

[0144] The formula for calculating the capacity retention rate of a battery after the Nth cycle is:

[0145] Capacity retention rate after Nth cycle = Discharge capacity after Nth cycle / Discharge capacity after first cycle × 100%.

[0146] (2) High-temperature storage performance test:

[0147] 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.

[0148] 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.

[0149] The formula for calculating the high-temperature storage capacity retention rate is: High-temperature storage capacity retention rate (%) = C1 / C0 × 100%.

[0150] Each performance test involved testing three batteries in parallel and taking the average value as the test result.

[0151] Table 2: Test results (%) of lithium-ion batteries corresponding to Examples 1-8 and Comparative Examples 1-7

[0152] test group ambient temperature cycling performance High temperature cycling performance High-temperature storage performance Example 1 91.2 89.4 86.9 Example 2 91.8 89.6 87.2 Example 3 93.1 91.2 88.8 Example 4 92.5 90.6 88.3 Example 5 92.1 90.1 87.8 Example 6 92.6 90.9 88.5 Example 7 92.8 91.1 88.6 Example 8 94.4 92.4 90.1 Comparative Example 1 36.5 32.4 30.6 Comparative Example 2 48.9 43.6 44.3 Comparative Example 3 60.2 56.3 57.2 Comparative Example 4 53.3 48.7 52.1 Comparative Example 5 72.3 70.5 68.2 Comparative Example 6 79.6 76.4 74.9 Comparative Example 7 75.4 73.9 72.7

[0153] According to the test results in Table 2, compared with Comparative Example 1 (blank control group), Examples 1-8 significantly improved the high voltage resistance, high temperature storage performance and cycle performance of lithium-ion batteries by adding HFE458, Compound I and isocyanate compounds as additives to the lithium-ion battery electrolyte.

[0154] Furthermore, Example 8 adds DENE to Example 3, which can effectively improve the high voltage resistance, high temperature storage performance and cycle performance of lithium-ion batteries compared to Example 3.

[0155] 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 HMDI. The room temperature cycling performance of Comparative Examples 2-4 was 48.9%, 60.2%, and 53.3%, respectively; the high temperature cycling performance of Comparative Examples 2-4 was 43.6%, 56.3%, and 48.7%, respectively; and the high temperature storage performance of Comparative Examples 2-4 was 44.3%, 57.2%, and 52.1%, respectively. This shows that using HFE458, Compound I, or HMDI alone can only improve the high temperature storage performance, room temperature and high temperature cycling performance of lithium-ion batteries to a limited extent compared to the blank control group.

[0156] 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 Compound I and isocyanate compounds, 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 cobalt ions. 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.

[0157] As for Comparative Example 3, the addition of only Compound I resulted in only a limited improvement in its 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 HMDI, Compound I cannot form a uniform film on both the positive and negative electrodes in the absence of HFE458. Furthermore, the formed CEI film cannot effectively prevent the dissolution of cobalt ions. In addition, more side reactions occur at both the positive and negative electrodes, further deteriorating the electrolyte environment. Consequently, the performance of the lithium-ion battery prepared with the electrolyte containing only Compound I is only limited compared to the blank control.

[0158] As for Comparative Example 4, the addition of HMDI 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 HFE458 and Compound I, the lack of HFE458 prevents HMDI from forming a stable CEI film at the positive electrode, and the absence of Compound I prevents HMDI from effectively polymerizing at the negative electrode, leading to an unstable SEI film and incomplete complexation of cobalt ions. Consequently, the performance of the lithium-ion battery prepared with the electrolyte containing only HMDI showed only a limited improvement compared to the blank control.

[0159] Further comparison of Example 3 with Comparative Examples 5, 6 and 7 shows that, compared with Example 3, Comparative Example 5 lacked HFE458, Comparative Example 6 lacked HMDI, and Comparative Example 7 lacked Compound I. 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.

[0160] For Comparative Example 5, which lacks HFE458, its high-temperature storage performance and room-temperature and high-temperature cycling performance are only slightly improved compared to the blank control. This may be because the lack of HFE458 in Comparative Example 5 allows highly active solvent molecules in the electrolyte to come into direct contact with the positive electrode, resulting in low antioxidant capacity of the electrolyte. At the same time, due to the lack of HFE458, a uniform reaction substrate cannot be provided for Compound I and isocyanate compounds, 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 5.

[0161] For Comparative Example 6, which lacks HMDI, 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, due to the absence of one of the additives capable of cobalt ion coordination, the additive composition of Comparative Example 7 could not better immobilize free cobalt ions in the electrolyte system, thus failing to effectively prevent cobalt ions from migrating to the negative electrode. Simultaneously, the lack of HMDI prevented the formation of organic polymers on both the positive and negative electrode surfaces that could enhance the mechanical toughness and resistance to deformation of the CEI / SEI film, resulting in 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 6.

[0162] For Comparative Example 7, lacking Compound I, its high-temperature storage performance and room-temperature and high-temperature cycling performance showed only limited improvement compared to the blank control. Similar to Comparative Example 6, the absence of Compound I meant that the additive composition of Comparative Example 7 lacked an additive that could interact with cobalt ions, preventing it from effectively immobilizing free cobalt ions in the electrolyte system and thus failing to effectively prevent cobalt ions from migrating to the negative electrode. Simultaneously, the lack of Compound I prevented HMDI from rapidly forming organic polymers at the positive and negative electrodes, thus hindering its effective replenishment of the CEI and SEI films. Ultimately, this resulted in 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.

[0163] In summary, this embodiment adds HFE458, Compound I, and isocyanate compounds as additives to the electrolyte. Compound I and isocyanate compounds remove trace amounts of H2O and HF, laying the foundation for the subsequent formation of CEI and SEI films. Then, through the synergistic effect of HFE458, Compound I, and isocyanate compounds, CEI and SEI films with higher ionic conductivity, chemical stability, and density are generated, and side reactions such as cobalt ion dissolution and electrolyte decomposition are suppressed. At the same time, the performance of the positive and negative electrode dual-interface films is optimized, which can effectively prevent the CEI film from being damaged under high voltage and thus prevent the damage to the positive electrode material structure. This significantly improves the high-temperature storage stability, room temperature and high-temperature cycling performance of lithium-ion batteries.

[0164] Therefore, the electrolyte in this embodiment can significantly improve the high voltage resistance, high temperature storage performance, and cycle performance of lithium-ion batteries.

[0165] 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 in that, The electrolyte comprises: Lithium salts Non-aqueous solvents, and additive; The additives include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, isocyanate compounds, and compounds with the structure shown in Formula I: ； 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%, based on the total mass of the electrolyte.

3. The electrolyte according to claim 1, characterized in that, The isocyanate compounds include at least one of terephthalic diisocyanate, toluene-2,4-diisocyanate and 4,4'-diisocyanate dicyclohexylmethane; The content of the isocyanate compound is 1.5-5%, based on the total mass of the electrolyte.

4. The electrolyte according to any one of claims 1-3, characterized in that, The content of the compound is 0.5-3%, based on the total mass of the electrolyte.

5. The electrolyte according to claim 1, characterized in that, 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. The lithium salt content is 5-20%, based on the total mass of the electrolyte.

6. The electrolyte according to claim 1, characterized in that, The non-aqueous solvent is selected from at least one of carbonates, fluorocarbonates, carboxylic acid esters, fluorocarboxylic acid esters, ethers, and fluoroethers.

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, 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 69-92.5%, based on the total mass of the electrolyte.

8. The electrolyte according to claim 1, characterized in that, The electrolyte also includes other additives; The other additives also include at least one of vinylene sulfate, triallyl phosphate, and ethylene glycol bis(propionitrile) ether; The content of the other additives is 0.5-3.5%, based on the total mass of the electrolyte.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes: Positive electrode sheet; Negative electrode plate; Diaphragm; and The electrolyte according to any one of claims 1-8.

10. The lithium-ion battery according to claim 9, characterized in that, 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, LiCo 1-y MyO2, LiFe 1-y M y PO4 and Li2Mn 1-y M y At least one of O4; 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; The lithium-ion battery operates at a voltage of 3.0-4.5V.

Images