Electrolyte for lithium ion battery and lithium ion battery thereof

Abstract

The application discloses an electrolyte of a lithium ion battery and a lithium ion battery thereof, and at least comprises an organic solvent, a lithium salt and boron trifluoride-propargyl alcohol lithium; wherein the boron trifluoride-propargyl alcohol lithium has the following structural formula: the application adds the specific boron trifluoride-propargyl alcohol lithium, and through implementation and application verification, can effectively inhibit the side reaction of a ternary lithium ion battery under a high-temperature environment, stabilize the positive and negative electrode interface, reduce electrode material deterioration and active lithium consumption, and simultaneously significantly improve the high-temperature cycle life and high-temperature storage performance of the battery.

Description

Technical Field

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

[0002] With the rapid development of new energy vehicles and energy storage systems, ternary lithium-ion batteries have become the mainstream choice in the power battery field due to their advantages of high energy density, stable voltage platform, and high tap density. They are widely used in various portable electronic devices, new energy vehicles, and large-scale energy storage scenarios. However, the performance stability of ternary lithium-ion batteries, especially their cycle life and storage performance under high-temperature environments, remains a core bottleneck restricting their further promotion and application, and a key technical problem that the industry urgently needs to solve.

[0003] The normal operating temperature range of ternary lithium-ion batteries is typically -30℃ to 60℃, with the ideal operating range being 0℃ to 45℃. When the temperature exceeds 45℃, the internal side reactions of the battery will be significantly amplified, leading to rapid performance degradation. Furthermore, under high-temperature cycling conditions, the electrolyte is prone to decomposition reactions, and the resulting byproducts will deposit on the electrode surface, hindering lithium-ion transport. At the same time, it will accelerate the dissolution and structural degradation of the positive electrode material, resulting in irreversible loss of battery capacity and a significant reduction in cycle life. Existing experimental data shows that at high temperatures above 60℃, the cycle life of ternary batteries is even less than half that at room temperature. In high-temperature storage scenarios, especially long-term high-temperature storage under full charge, problems such as byproduct accumulation and increased rock salt phase will occur on the surface of the positive electrode material of ternary batteries. The dissolved transition metal elements will deposit on the surface of the negative electrode, damaging the SEI, consuming active lithium, leading to increased battery capacity loss rate and significantly increased internal resistance, seriously affecting the storage reliability and long-term service performance of the battery.

[0004] Electrolyte, as the "blood" of ternary lithium-ion batteries, directly determines the battery's high and low temperature performance, cycle life, storage stability, and safety performance, and is a key component for regulating the battery's high-temperature performance. Current technologies mainly improve the high-temperature performance of ternary batteries by optimizing the electrolyte formulation and adding functional additives. Commonly used high-temperature additives include sulfonate lactones such as 1,3-propanesulfonate lactone (PS) and 1,4-butanesulfonate lactone (BS), and additives containing unsaturated bonds such as vinyl ethylene carbonate (VEC), propene sulfonate lactone (PST), tetravinylsilane (TVS), and propargyl phosphate (TPL). Sulfonate ester additives have a relatively mild effect in inhibiting electrolyte decomposition at high temperatures, which is beneficial for long cycle life, but they also pose strong carcinogenicity and are subject to restrictions under EU REACH regulations. While these additives containing unsaturated bonds significantly improve high-temperature performance and help inhibit electrolyte decomposition at high temperatures, they also lead to excessively high battery impedance, affecting kinetic performance such as rate discharge or low-temperature discharge, and further improvements are needed.

[0005] Domestic invention patent applications with publication numbers CN115197259A and CN116715691A have respectively reported the synthesis of boron trifluoride lithium methacrylate, which is used as an additive in high-voltage systems (>4.4 V) to improve high-temperature performance. However, due to the limited oxidation resistance of acrylic acid residues in its structure, such additives still suffer from oxidative decomposition under long-term high-voltage cathode action, leading to problems such as CEI film rupture, transition metal dissolution, and capacity decay. In long-term cycling, the deposition of its decomposition products also leads to a rapid increase in interfacial impedance, resulting in a decline in battery performance.

[0006] The domestic invention patent application with publication number CN118173890A discloses the application of synthesized boron trifluoride lithium pyrosulfate as an additive. However, since lithium pyrosulfate is quite sensitive to moisture, even trace amounts of moisture can cause it to decompose and generate sulfuric acid and dissociate byproducts such as BF3, which can damage the SEI / CEI membrane, trigger side reactions and increase impedance. Therefore, there is still a need for improvement.

[0007] Therefore, the applicant seeks technical solutions to improve the above-mentioned technical problems. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide an electrolyte for a lithium-ion battery and a lithium-ion battery thereof, which adds a specific boron trifluoride-propynyl alcohol lithium. Through practical application, it has been proven that it can effectively suppress the side reactions of ternary lithium-ion batteries under high temperature environment, stabilize the positive and negative electrode interface, reduce electrode material degradation and active lithium consumption, and significantly improve the high temperature cycle life and high temperature storage performance of the battery.

[0009] The technical solution adopted in this invention is as follows: An electrolyte for a lithium-ion battery comprises at least: an organic solvent, a lithium salt, and boron trifluoride-propynyl alcohol lithium; wherein the boron trifluoride-propynyl alcohol lithium has the following structural formula: .

[0010] Preferably, the mass of the boron trifluoride-lithium propargyl alcohol accounts for 0.1%-6% of the total mass of the electrolyte.

[0011] Preferably, the organic solvent includes any one or a mixture of several of the following: ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, acetonitrile, and sulfolane.

[0012] Preferably, the lithium salt comprises lithium hexafluorophosphate (LiPF6) and a second lithium salt; wherein the second lithium salt comprises any one or a mixture of several of lithium tetrafluoroborate (LiBF4), lithium bis(oxalate-borate) (LiBOB), lithium difluorooxalate-borate (LiDFOB), lithium difluorodi(oxalate-phosphate) (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0013] Preferably, the lithium hexafluorophosphate (LiPF6) accounts for 8%-15% of the total mass of the electrolyte; the second lithium salt accounts for 0%-10% of the total mass of the electrolyte, preferably 0.1%-3%, or preferably 3%-8%.

[0014] Preferably, the electrolyte further comprises 0.1%-10% by mass of an additive, more preferably 0.3%-5%, and even more preferably 0.5%-3%; wherein the additive comprises any one or a mixture of several of the following additives: Carbonate additives; Sulfate ester additives; Boronate ester additives; Phosphate ester additives; Sulfonate lactones or alkyl sulfonates are additives; Nitrile additives.

[0015] Preferably, the preparation of the boron trifluoride-propynyl alcohol lithium includes at least the following steps: S1. Dissolve propynyl alcohol in a first solvent to form a solution, then add organic / inorganic lithium dropwise to the solution to react and obtain a reaction solution. Post-process the reaction solution to obtain a solid-phase lithium salt intermediate. S2. The solid lithium salt intermediate obtained in step S1 and the boron trifluoride source are reacted in the atmosphere of the second solvent for 0.5-3 hours, and the reaction temperature is set between -10℃ and 30℃ to obtain the reaction product; the reaction product is filtered, washed and dried to obtain the boron trifluoride-propynyl alcohol lithium.

[0016] Preferably, the organic / inorganic lithium is one or a mixture of several of lithium hydride, bis(trimethylsilyl)aminolithium, lithium diisopropylamine, and lithium tert-butoxide; the boron trifluoride source is boron trifluoride gas or boron trifluoride complex liquid; the boron trifluoride complex liquid is selected from one of boron trifluoride-dimethyl carbonate complex liquid, boron trifluoride-diethyl ether complex liquid, boron trifluoride-acetonitrile, boron trifluoride-methyl ethyl carbonate complex liquid, and boron trifluoride-diethylene glycol dimethyl ether complex liquid.

[0017] Preferably, a lithium-ion battery includes a positive electrode material, a negative electrode material, and an electrolyte according to the lithium-ion battery described above.

[0018] Preferably, the cathode material is selected from lithium transition metal oxides; wherein the lithium transition metal oxide is LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, Li 1+a Mn 1-x M x O2, LiCo 1-x MxO2, LiFe 1-x M x PO4, Li2Mn 1-x At least one of O4, wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, and F, and 0 ≤ a < 0.2, 0 ≤ x < 0.2; The negative electrode material is selected from at least one of graphite, silicon-carbon composite material, and lithium titanate.

[0019] This invention adds a specific boron trifluoride-propynyl alcohol lithium to the electrolyte. Through practical application, it has been proven that this can effectively suppress side reactions of ternary lithium-ion batteries under high-temperature conditions, stabilize the positive and negative electrode interfaces, reduce electrode material degradation and active lithium consumption, and significantly improve the high-temperature cycle life and high-temperature storage performance of the battery.

[0020] More preferably, the preparation method of boron trifluoride-propynyl alcohol lithium provided by the present invention is simple, has mild reaction conditions, does not have high reaction requirements, has high product yield, and has a simple purification method, making it suitable for large-scale industrial production. Detailed Implementation

[0021] This embodiment proposes an electrolyte for a lithium-ion battery, comprising at least: an organic solvent, a lithium salt, and boron trifluoride-lithium propargyl alcohol; wherein, the boron trifluoride-lithium propargyl alcohol has the following structural formula: Preferably, in this embodiment, the mass of boron trifluoride-lithium propynyl alcohol accounts for 0.1%-6% of the total mass of the electrolyte, more preferably 0.5%-4%, even more preferably 0.9-1.1%, and most preferably 1%.

[0022] Preferably, in this embodiment, the organic solvent includes any one or a mixture of several of the following: ethylene carbonate EC, propylene carbonate PC, butenyl carbonate BC, fluoroethylene carbonate FEC, dimethyl carbonate DMC, ethyl methyl carbonate EMC, diethyl carbonate DEC, methyl propyl carbonate MPC, methyl acetate MA, ethyl acetate EA, propyl acetate PA, butyl acetate BA, methyl propionate MP, ethyl propionate EP, propyl propionate PP, methyl butyrate MB, ethyl butyrate EB, γ-butyrolactone γ-GBL, acetonitrile AN, and sulfolane TMS.

[0023] Preferably, in this embodiment, the lithium salt includes lithium hexafluorophosphate (LiPF6) and a second lithium salt; wherein the second lithium salt includes any one or a mixture of several of lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluorooxalato)borate (LiDFOB), lithium difluorodi(oxalato)phosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); more preferably, in this embodiment, the mass of lithium hexafluorophosphate (LiPF6) accounts for 8%-15% of the total mass of the electrolyte; the mass of the second lithium salt accounts for 0%-10% of the total mass of the electrolyte, preferably 0.1%-3% (equivalent to being used as an additive), or preferably 3%-8%.

[0024] Preferably, in this embodiment, it further includes an additive comprising 0.1%-10% of the total mass of the electrolyte, more preferably 0.3%-5%, and more preferably 0.5%-3%; wherein the additive comprises any one or a mixture of several of the following additives: Carbonate additives: Typical choices include ethylene carbonate (VC) and / or fluoroethylene carbonate (FEC); Sulfate ester additives: Typical options include vinyl sulfate DTD and / or cyclic trimethylene sulfate; Boronate additives: Tris(trimethylsilane)boronate (TMSB) is a typical example. Phosphate ester additives: Tris(trimethylalkyl) phosphate (TMSP) is a typical example. Sulfonate lactones or alkyl sulfonates: Typical options include 1,3-propanesulfonate lactone (PS) and / or 1,4-butanesulfonate lactone (BS), methylene disulfonate (MMDS), etc. Nitrile additives: Typical options include butadionitrile, adiponitrile, glutaronitrile, 1,3,6-hexanetrionitrile (HTCN), 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(cyanoethoxy)propane, 1,2,3,4-tetra(cyanoethoxy)butane, etc.

[0025] Preferably, in this embodiment, the preparation of boron trifluoride-propynyl alcohol lithium includes at least the following steps: S1. Propylene alcohol is dissolved in a first solvent to form a solution, and then organic / inorganic lithium is added dropwise to the solution to react and obtain a reaction solution. The reaction solution is then post-treated to obtain a solid-phase lithium salt intermediate. In step S1, the first solvent is selected from one or a mixture of several of dichloromethane, trichloromethane, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, diethyl ether, tetrahydrofuran, ethyl acetate, methyl formate, ethylene carbonate, and methyl tert-butyl ether. The organic / inorganic lithium is selected from one or a mixture of several of lithium hydride, bis(trimethylsilyl)aminolithium, lithium diisopropylamine, and lithium tert-butoxide. Preferably, in step S1, the amount of the first solvent added is 3.0-10.0 times the mass of propynyl alcohol, more preferably 5.0-6.0 times, and even more preferably 4.0-6.0 times; the molar ratio of organic / inorganic lithium to propynyl alcohol is 1:(0.9-1.2), and the excess portion can be removed by a post-processing step; the dropping temperature of organic / inorganic lithium is -20℃ to 0℃, preferably -10℃ to 0℃; the dropping time of organic / inorganic lithium is controlled at 0.5-3.5 hours, as excessively rapid dropping will lead to excessively high local reaction concentration, triggering side reactions and reducing the yield of solid-phase lithium salt intermediates; after the dropping is completed, the reaction continues for 0.5-3 hours, preferably 0.5-1.5 hours, to ensure that propynyl alcohol and organic / inorganic lithium react fully.

[0026] Preferably, in step S1, the post-processing includes filtration and washing; wherein, the reaction solution is filtered to obtain a solid intermediate insoluble in the first solvent; then the solid intermediate is washed to remove byproducts soluble in the first solvent, to obtain a solid lithium salt intermediate with a purity ≥98%; more preferably, during washing, a detergent is used to wash the solid intermediate once or multiple times, the detergent being selected from any one of diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; and each time the detergent is added, the amount is 1.0-5.0 times the molar amount of organic / inorganic lithium, preferably 1.5-3.5 times.

[0027] S2. The solid lithium salt intermediate obtained in step S1 and the boron trifluoride source are reacted in the atmosphere of the second solvent for 0.5-3 hours (preferably 0.5-1.5 hours) at a temperature of -10℃ to 30℃ (preferably 5℃ to 25℃) to obtain the reaction product; the reaction product is filtered, washed and dried to obtain boron trifluoride-propynyl alcohol lithium; Preferably, in step S2, the boron trifluoride source is either boron trifluoride gas or a boron trifluoride complex liquid. It should be further noted that in this step, the reaction system can be selected according to the form of the boron trifluoride raw material: if boron trifluoride gas is used, a closed pressurized reactor is used as the reaction device, and the preferred gas flow rate is 0.1-0.5 L / (min·mol solid lithium salt intermediate), with continuous stirring to ensure sufficient gas-liquid contact; if a boron trifluoride complex liquid is used, a conventional closed reaction flask can be used, simplifying the operation process. The boron trifluoride complex liquid exhibits higher stability, is easier to store and use, and is safer. The properties are superior to boron trifluoride gas, making it a more preferred reaction raw material. More preferably, when using a boron trifluoride complex liquid, boron trifluoride and a second solvent are pre-mixed, and then the boron trifluoride complex liquid is added dropwise. The dropwise addition temperature is recommended to be between -5°C and 5°C, more preferably between -2°C and 2°C. The reaction is then continued at 5°C to 25°C. Preferably, in this embodiment, the boron trifluoride complex liquid is selected from one of the following: boron trifluoride-dimethyl carbonate complex liquid, boron trifluoride-diethyl ether complex liquid, boron trifluoride-acetonitrile, boron trifluoride-ethyl methyl carbonate complex liquid, and boron trifluoride-diethylene glycol dimethyl ether complex liquid.

[0028] Preferably, in this embodiment, the second solvent is selected from one or a mixture of several of dichloromethane, chloroform, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, diethyl ether, tetrahydrofuran, ethyl acetate, methyl formate, ethylene carbonate, and methyl tert-butyl ether; the molar ratio of boron trifluoride to the solid lithium salt intermediate is (1.0-5.0):1, more preferably (1.0-1.5):1. An appropriate excess of boron trifluoride can ensure that the solid lithium salt intermediate can achieve a more complete reaction under the second solvent atmosphere, thereby improving the yield of the target product; Since a reaction temperature that is too low will result in a slow coordination reaction rate, while a temperature that is too high may lead to the decomposition of the boron trifluoride complex or the degradation of the target product, it is more preferable that in this step S2, the temperature conditions are set to 5°C to 10°C and the reaction time is controlled to 0.5-1.5 hours to ensure that the solid lithium salt intermediate and boron trifluoride undergo a full coordination reaction in the second solvent atmosphere to generate boron trifluoride lithium salt.

[0029] Preferably, in this embodiment, the following steps are also included: S3. The boron trifluoride-lithium propynyl alcohol reaction product obtained in step S2 is filtered, and then the filter is washed once or multiple times with a detergent, and then dried to obtain a boron trifluoride-lithium salt product containing nitrile / acetylene functional groups; wherein, the detergent is any one of diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; more preferably, the number of washing times is 2-4 times; and each time the amount of detergent added is 1.0-5.0 times the molar amount of boron trifluoride, preferably 1.6-4.0 times, which can effectively remove unreacted boron trifluoride, trace intermediates and other impurities; preferably, in this step S3, the drying treatment adopts vacuum drying, the drying temperature is 20-50℃, the pressure is set at -0.09 to -0.1MPa, and the drying time is 6-10 hours to ensure that the product moisture content is ≤50ppm, so as to avoid the adverse effect of moisture on its application in lithium-ion batteries.

[0030] In a specific embodiment of the present invention, the preparation method of the electrolyte for lithium-ion batteries is recommended to be as follows: An organic solvent is pre-prepared, and after freezing the organic solvent for 1-3 hours, lithium salt is added to the organic solvent for mixing. Finally, boron trifluoride-lithium propynyl alcohol and other additives are added and mixed to obtain the electrolyte for lithium-ion batteries. Alternatively, lithium salts such as LiPF6 and LiFSI can be pre-dissolved in a specific solvent (such as DMC or EMC), and then the corresponding solvent or additives are added for mixing. During this process, stirring or cooling operations can be performed to mix into a homogeneous solution, thus obtaining the final lithium-ion battery electrolyte. It should be noted that the electrolyte preparation process used in the embodiments of this application is a conventional technical means in the art, and in order to save space, this embodiment will not be elaborated in detail.

[0031] Preferably, this embodiment also provides a lithium-ion battery, including a positive electrode material, a negative electrode material, and an electrolyte according to the above-described lithium-ion battery; preferably, in this embodiment, the positive electrode material is selected from lithium transition metal oxides; wherein, the lithium transition metal oxide is LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, Li 1+a Mn 1-x M x O2, LiCo 1- x MxO2, LiFe 1-x M x PO4, Li2Mn 1-x At least one of O4, wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, and F, 0≤a<0.2, 0≤x<0.2; the negative electrode material is selected from at least one of graphite, silicon-carbon composite material, and lithium titanate.

[0032] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0033] Based on the above-described implementation schemes, this application further proposes the following specific embodiments: First, it should be noted that the reagent raw materials used in the following specific embodiments and comparative examples of the present invention are sourced from the following: Unless otherwise specified, all raw materials are ordinary commercially available products.

[0034] The test methods used in the specific embodiments and comparative examples of this invention are as follows: The structure of the product was determined by nuclear magnetic resonance using a JEOL JNM-ECZL400S spectrometer. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1:

[0035] Propylene alcohol (5.60 g, 0.1 mol) was added to 30 g of diethyl ether, followed by the dropwise addition of lithium hydride (0.79 g, 0.1 mol) over 30 min in a cold bath at -5 °C. The mixture was then heated to room temperature (25 °C) and the reaction continued for 2 hours. The resulting reaction solution was filtered to obtain a solid, which was then washed twice with 20 mL of tetrahydrofuran to obtain a crude solid (the solid-phase lithium salt intermediate). This crude solid was added to 60 mL of tetrahydrofuran and then incubated at 0 °C. 16.5 g of boron trifluoride-dimethyl carbonate complex liquid (0.105 mol) was added dropwise over 30 min at a temperature of 25°C. After the addition was complete, the mixture was allowed to return to room temperature and reacted for another 60 min. The mixture was then filtered, washed twice with 20 mL of diethyl ether, and dried overnight at 40°C to obtain a white solid product (i.e., lithium boron trifluoride-propynyl alcohol). The product purity was 99.3%, and the yield was 93.5%. The product structure is as follows: ; The product's NMR characterization is as follows: 1 H NMR (400 MHz, acetonitrile-d): 4.30 (dd, 2h), 2.51 (s, 1h) 11 B NMR (400 MHz, acetonitrile-d): δ=-2.25ppm 19 F NMR (400 MHz, acetonitrile-d): δ=-152.3ppm. Example 2: First, prepare the electrolyte according to the following procedure:

[0036] Preparation is carried out in a glove box under N2 atmosphere, with the water content of the organic solvent <10 ppm; the electrolyte (total mass fraction 100%) includes: The organic solvent has a mass fraction of 85.5%, specifically composed of ethylene carbonate EC and ethyl methyl carbonate EMC in a mass ratio of 3:7. Lithium salt, specifically 1.0 mol·L⁻¹. -1 Lithium hexafluorophosphate (LiPF6); The product provided in Example 1 accounts for 0.5% of the electrolyte by mass. The rest are other additives, specifically composed of: fluoroethylene carbonate FEC, propanesulfonate lactone PS, ethylene sulfate DTD, and lithium difluorooxalate borate LiDFOB = 1:0.5:2:1 (mass ratio); After mixing the organic solvents in a fixed ratio, the mixture is cooled to a freezing temperature of 1.5-2 hours to obtain an organic solvent mixture. Lithium salt is added and mixed evenly. Finally, the product provided in Example 1 and other additives are added and mixed evenly before use. Then, the lithium-ion battery is manufactured according to the following process:

[0037] Preparation of the battery positive electrode: Using methylpyrrolidone (NMP) as a solvent, 2% (w / w) of polyvinylidene fluoride (PVDF) was uniformly dispersed to obtain a mixture. Then, 2% (w / w) of carbon nanotubes (CNTs) were added and uniformly mixed. Next, 96% (w / w) of the positive electrode active material (NCM613) was added and mixed evenly. The mixture was then uniformly coated onto aluminum foil using a coating machine. After drying, rolling, and cutting, the positive electrode sheet was formed with an areal density ranging from 350 to 450 g / cm³. 2 (Double-sided); Preparation of the battery negative electrode: Using deionized water as a solvent, 1% by mass of carboxymethyl cellulose (CMC) was uniformly dispersed to obtain a mixed solution. Then, 2% by mass of conductive carbon black (SP) and 96% by mass of negative electrode active material (specifically, vapor-deposited silicon-carbon composite material, material model SH-SO2) were added and uniformly mixed. Finally, 1% by mass of styrene-butadiene rubber (SBR) was added and uniformly mixed. After uniform mixing, the mixture was evenly coated onto copper foil using a coating machine. After drying, rolling, and cutting, the negative electrode sheet was formed with an areal density ranging from 200 to 350 g / cm³. 2(Double-sided)

[0038] Example 3: The remaining technical solutions of Example 3 are the same as those of Example 2, except that in Example 3, the mass fraction of the product provided in Example 1 in the electrolyte is increased to 1.0%, and the mass fraction of the organic solvent is correspondingly reduced.

[0039] Example 4: The remaining technical solutions of Example 4 are the same as those of Example 2, except that in Example 4, the mass fraction of the product provided in Example 1 in the electrolyte is increased to 4.0%, and the mass fraction of the organic solvent is correspondingly reduced.

[0040] Comparative Example 1: The rest of the technical solutions of Comparative Example 1 are the same as those of Example 2, except that the electrolyte in Comparative Example 1 does not contain the product provided in Example 1.

[0041] Comparative Example 2: The rest of the technical solutions of Comparative Example 2 are the same as those of Comparative Example 1, except that: in Comparative Example 2, lithium difluorophosphate (LiPO2F2) accounting for 0.5% of the total mass of the electrolyte is added to the electrolyte provided in Comparative Example 1.

[0042] Comparative Example 3: The rest of the technical solutions of Comparative Example 3 are the same as those of Comparative Example 1, except that: in Comparative Example 3, lithium difluorophosphate (LiPO2F2) accounting for 1.0% of the total mass of the electrolyte is added to the electrolyte provided in Comparative Example 1.

[0043] Comparative Example 4: The rest of the technical solutions of Comparative Example 4 are the same as those of Comparative Example 1, except that: in Comparative Example 4, lithium trifluoroborate methacrylate accounting for 1.0% of the total mass of the electrolyte is added to the electrolyte provided in Comparative Example 1.

[0044] Comparative Example 5: The rest of the technical solutions of Comparative Example 5 are the same as those of Comparative Example 1, except that in Comparative Example 5, 1.0% of lithium trifluoroborate acrylate by mass of the electrolyte is added to the electrolyte provided in Comparative Example 1.

[0045] Therefore, the following pouch cells were obtained: those assembled from Examples 2-4 and Comparative Examples 1-5, respectively; wherein the electrolyte usage of each pouch cell was 3.5-4.5 g / Ah; and then the following performance comparison tests were performed on each pouch cell: Three groups of each soft-pack battery corresponding to Examples 2-4 and Comparative Examples 1-5 were prepared. Each group was tested by cycling 100, 200 and 300 times at 45°C and storing for 28 days at 55°C. The charge and discharge conditions used in each cycle test were: charge / discharge rate of 1C / 1C and voltage range of 2.75 V-4.4 V. Please refer to Table 1 below for the measured capacity retention of lithium-ion batteries:

[0046] The measured performance of lithium-ion batteries at 55°C for 28 days is shown in Table 2 below:

[0047] Based on the test results of the above embodiments and comparative examples, it can be seen that the present invention, by introducing boron trifluoride-lithium propargyl alcohol, improves the high-temperature cycle life and high-temperature storage performance of the battery without significantly increasing the initial internal resistance. It should be further noted that, through further implementation and verification, when the mass ratio of boron trifluoride-lithium propargyl alcohol in the electrolyte is 0.9-1.1%, its high-temperature cycle stability and high-temperature storage performance are significantly better. Among them, when the mass ratio of boron trifluoride-lithium propargyl alcohol in the electrolyte is 1.0%, its high-temperature cycle stability and high-temperature storage performance are optimal.

[0048] The core advantages of introducing boron trifluoride-lithium propynyl alcohol in this application are: the ability to form a dense, low-resistance composite passivation film on the electrode surface, suppressing side reactions between the electrolyte and the electrode; the ability to effectively slow down the increase in interfacial impedance under high-temperature conditions, maintaining stable ion transport channels; and the ability to significantly improve the capacity retention and recovery rate of the battery under high-temperature environments, thereby improving the long-term stability and reliability of the battery. In summary, the introduction of boron trifluoride-lithium propynyl alcohol additive into the electrolyte formulation system in this invention can significantly improve the high-temperature cycling and storage performance of lithium-ion batteries, and has good prospects for industrial application.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An electrolyte for a lithium-ion battery, characterized in that, It includes at least: an organic solvent, a lithium salt, and boron trifluoride-propynyl alcohol lithium; wherein, the boron trifluoride-propynyl alcohol lithium has the following structural formula: 。 2. The electrolyte of the lithium-ion battery according to claim 1, characterized in that, The mass of the boron trifluoride-lithium propargyl alcohol is 0.1%-6% of the total mass of the electrolyte.

3. The electrolyte of the lithium-ion battery according to claim 1, characterized in that, The organic solvent includes any one or a mixture of several of the following: ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, acetonitrile, and sulfolane.

4. The electrolyte of the lithium-ion battery according to claim 1, characterized in that, The lithium salt includes lithium hexafluorophosphate (LiPF6) and a second lithium salt; wherein the second lithium salt includes any one or a mixture of several of lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluorooxalato)borate (LiDFOB), lithium difluorodioxalato)phosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

5. The electrolyte of the lithium-ion battery according to claim 4, characterized in that, The lithium hexafluorophosphate (LiPF6) accounts for 8%-15% of the total mass of the electrolyte; the second lithium salt accounts for 0%-10% of the total mass of the electrolyte, preferably 0.1%-3%, or preferably 3%-8%.

6. The electrolyte of the lithium-ion battery according to claim 1, characterized in that, It also includes additives comprising 0.1%-10% of the total mass of the electrolyte, preferably 0.3%-5%, more preferably 0.5%-3%; wherein the additives comprise any one or a mixture of several of the following additives: Carbonate additives; Sulfate ester additives; Boronate ester additives; Phosphate ester additives; Sulfonate lactones or alkyl sulfonates are additives; Nitrile additives.

7. The electrolyte of the lithium-ion battery according to claim 1, characterized in that, The preparation of the boron trifluoride-propynyl alcohol lithium includes at least the following steps: S1. Dissolve propynyl alcohol in a first solvent to form a solution, then add organic / inorganic lithium dropwise to the solution to react and obtain a reaction solution. Post-process the reaction solution to obtain a solid-phase lithium salt intermediate. S2. The solid lithium salt intermediate obtained in step S1 and the boron trifluoride source are reacted in the atmosphere of the second solvent for 0.5-3 hours, and the reaction temperature is set between -10℃ and 30℃ to obtain the reaction product; the reaction product is filtered, washed and dried to obtain the boron trifluoride-propynyl alcohol lithium.

8. The electrolyte of the lithium-ion battery according to claim 7, characterized in that, The organic / inorganic lithium is one or a mixture of several of lithium hydride, bis(trimethylsilyl)aminolithium, lithium diisopropylamine, and lithium tert-butoxide; the boron trifluoride source is boron trifluoride gas or boron trifluoride complex liquid; the boron trifluoride complex liquid is selected from one of boron trifluoride-dimethyl carbonate complex liquid, boron trifluoride-diethyl ether complex liquid, boron trifluoride-acetonitrile, boron trifluoride-methyl ethyl carbonate complex liquid, and boron trifluoride-diethylene glycol dimethyl ether complex liquid.

9. A lithium-ion battery, characterized in that, It includes positive electrode material, negative electrode material, and electrolyte of lithium-ion battery according to any one of claims 1-8.

10. The lithium-ion battery according to claim 9, characterized in that, The cathode material is selected from lithium transition metal oxides; wherein the lithium transition metal oxide is LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, Li 1+ a Mn 1-x M x O2, LiCo 1-x MxO2, LiFe 1-x M x PO4, Li2Mn 1-x At least one of O4, wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, and F, and 0 ≤ a < 0.2, 0 ≤ x < 0.2; The negative electrode material is selected from at least one of graphite, silicon-carbon composite material, and lithium titanate.

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