High-temperature-resistant start-stop lithium battery and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant start-stop type lithium battery and a preparation method thereof, and belongs to the technical field of lithium batteries. The lithium battery comprises a positive plate, an electrolyte, a diaphragm, a negative plate and an aluminum shell, the electrolyte comprises a lithium salt, an additive and a solvent, the lithium salt comprises an electrolyte inorganic lithium salt, lithium trifluoromethanesulfonimide and lithium difluoro bis (oxalate) phosphate; the solvent is prepared from chain carbonate, fluoroethylene carbonate, vinyl ethyoxyl ethyl acrylate and 1, 2-di (2-cyanoethyoxyl) ethane; the additive comprises tris (2-cyanoethyl) borate and cyanosilyl phosphate, wherein the cyanosilyl phosphate contains a siloxane chain, a phosphate group and a cyano group. Through the synergistic effect of all the components under the optimal proportion, the electrolyte system can effectively inhibit solvent decomposition, electrode structure collapse and harmful side reactions at high temperature, and the prepared start-stop type lithium battery can show excellent cycle life, capacity retention rate and safety in a high-temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a high-temperature resistant start-stop lithium battery and its preparation method. Background Technology

[0002] The start-stop battery is the foundation of a car's start-stop system and determines the level of development of the system. The start-stop battery must not only withstand the instantaneous high current during start-stop and the rapid charging and discharging during driving, but also provide continuous and stable power to the vehicle's electrical equipment after the engine is turned off. Its operating environment is extremely harsh.

[0003] Traditional lead-acid batteries, due to their low power density, short cycle life, slow response speed, and large size and weight, can no longer meet the requirements of modern high-efficiency start-stop systems for rapid charging and discharging, high cycle count, and compact space.

[0004] Therefore, lithium batteries, which have high power density, long cycle life and fast charge and discharge capabilities, are considered an ideal alternative power source for start-stop systems. However, applying lithium batteries to automotive start-stop systems, especially when they operate for extended periods in high-temperature, enclosed environments such as engine compartments, faces severe technical challenges.

[0005] In summer, the temperature inside a car engine compartment can remain above 60°C for extended periods, and even reach 80°C in some areas. Under these high temperatures, the carbonate-based electrolyte in conventional lithium-ion batteries undergoes violent decomposition, reacting with the positive electrode active material through oxidation and with the negative electrode solid electrolyte interface film through reduction. This generates a large amount of gas and consumes active lithium. This not only leads to increased internal pressure and battery swelling failure, but also drastically accelerates capacity decay and power reduction, severely impacting the battery's cycle life and reliability. Summary of the Invention

[0006] This invention provides a high-temperature resistant start-stop lithium battery and its preparation method, which can solve the problem of severe performance degradation of lithium batteries used in start-stop systems at high temperatures in the prior art.

[0007] The objective of this invention can be achieved through the following technical solutions: A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum shell; The electrolyte includes lithium salt, additives, and solvent; The lithium salt includes electrolyte inorganic lithium salt, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate. The solvents include chain carbonates, fluoroethylene carbonates, vinyl ethoxyethyl acrylates, and 1,2-bis(2-cyanoethoxy)ethane. The additives include tris(2-cyanoethyl)borate and cyanosilicon phosphate; The structural formula of the cyanosilyl phosphate is as follows: .

[0008] In the above technical solution, the lithium salt includes three components. Lithium batteries used in automotive start-stop systems need to meet long-term high-temperature resistance requirements. However, single-electrolyte inorganic lithium salts (such as LiPF6) have poor high-temperature resistance, are prone to decomposition to produce HF, corroding the electrodes, and are sensitive to moisture. This invention simultaneously adds lithium trifluoromethanesulfonylimide and lithium difluorodioxalate phosphate. On the one hand, lithium trifluoromethanesulfonylimide is a lithium salt with high thermal stability and is not sensitive to moisture. Its addition improves the thermal stability and hydrolysis resistance of the lithium salt system, and its large anionic structure helps suppress lithium dendrite growth under high-rate discharge. On the other hand, lithium difluorodioxalate phosphate preferentially decomposes at both the positive and negative electrodes, forming a robust, dense interface film rich in LiF and PO components with high ionic conductivity, preventing further decomposition of the electrolyte and dissolution of transition metal ions at high temperatures. The three lithium salts work synergistically to improve thermal stability and interface strengthening capabilities while ensuring basic performance, thus enhancing high-temperature resistance.

[0009] Based on the above lithium salt system, this invention designs and optimizes the solvent system by adding fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane to the chain carbonate system. Chain carbonates are easily oxidized and decomposed at high temperatures, while fluoroethylene carbonate can partially inhibit the decomposition of the electrolyte solvent and form an excellent solid electrolyte interphase (SEI) film on the electrode surface, thereby reducing battery impedance and improving the battery's specific capacity and cycle stability. Vinyl ethoxyethyl acrylate contains double bonds and ethoxy segments. Due to the presence of double bonds, it can undergo partial polymerization at higher battery temperatures, forming a polymer protective layer on the positive electrode surface. This inhibits the oxidative decomposition of the electrolyte at high positive electrode potentials, coats the positive electrode active material, and reduces positive electrode structural collapse and transition metal dissolution during high-temperature cycling. The ethoxy segments impart good polarity to the solvent, making it compatible with other solvents. 1,2-bis(2-cyanoethoxy)ethane contains multiple cyano groups. The cyano group has extremely high polarity and a strong complexing effect on transition metal ions. It can "capture" metal ions dissolved from the positive electrode, prevent them from migrating to the negative electrode surface and damaging the SEI film, and suppress high-temperature capacity decay.

[0010] This invention adds additives to the electrolyte, including tris(2-cyanoethyl)borate and cyanosilicon phosphate. The tris(2-cyanoethyl)borate contains both boronic acid ester and cyano groups. The boronic acid ester groups contribute to the formation of a stable boron-containing interfacial film, thereby improving the Li... +Regarding mobility, the cyano group plays a role in complexing transition metal ions, preferentially acting on the positive electrode surface, forming a double protection with the cyano compound in the aforementioned solvent. As can be seen from the structural formula, the cyanosilyl phosphate ester of this invention is a compound that simultaneously integrates a siloxane chain, a phosphate group, and a cyano group. The siloxane chain exhibits good flexibility and high thermal stability, the phosphate ester is an excellent flame retardant and film-forming component, the cyano group is a strongly polar group and a metal ion chelating agent, and the P=O / O-Si bond present in the structure enhances the interfacial adsorption performance of the compound. At high temperatures, its cyano group and phosphate ester participate in the formation of a more stable and robust SEI / CEI film, and the siloxane structure imparts better elasticity to the interfacial film. Meanwhile, cyanosilicon phosphate can form a synergistic effect with the solvent vinyl ethoxyethyl acrylate. Due to the introduction of the cyano group, which is a very strong electron-withdrawing group, the chemical bonds attached to it are weakened, making these positions more susceptible to free radical attack. At high temperatures, the double bonds of vinyl ethoxyethyl acrylate are activated, and a free radical polymerization reaction occurs. At this time, the cyanosilicon phosphate is embedded in the polymer network, forming a polymer-inorganic composite protective layer on the electrode surface that combines chemical bonding and physical anchoring. This layer has flexibility (siloxane), flame retardancy (phosphate ester), and strong metal ion chelating ability (cyano group), while also having good ion transport channels, thus enhancing the high-temperature resistance of the battery.

[0011] Furthermore, the lithium salt concentration in the solvent is 1-1.5 mol / L. The lithium salt concentration needs to balance ionic conductivity and viscosity; too high a concentration will increase viscosity, while too low a concentration will result in poor conductivity and affect high-temperature performance.

[0012] Furthermore, the additive is 0.12-0.30% of the electrolyte mass.

[0013] Furthermore, the electrolyte inorganic lithium salt is one of LiPF6 and LiBF4. LiPF6 and LiBF4 are commonly used lithium salts that provide basic ionic conductivity while also acting synergistically with other lithium salts.

[0014] Furthermore, the mass ratio of the electrolyte inorganic lithium salt, lithium trifluoromethanesulfonylimide, and lithium difluorodioxazophosphate in the lithium salt is 1:(0.4-0.6):(0.15-0.3).

[0015] Furthermore, the chain carbonate is at least one selected from dimethyl carbonate, diethyl carbonate, and ethylene carbonate. Chain carbonates are commonly used solvents, providing basic solubility and conductivity, while also acting synergistically with other solvents.

[0016] Further, the mass ratio of the chain carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate and 1,2-bis(2-cyanoethoxy)ethane in the solvent is 1:(1.5-2.0):(0.2-0.4):(0.1-0.2).

[0017] Furthermore, the mass ratio of the tris(2-cyanoethyl)borate ester to the cyanosilicon phosphate ester is 1:(1.0-1.4).

[0018] Furthermore, the positive electrode sheet includes a positive current collector and a positive electrode material coated on the positive current collector; The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder; The positive electrode active component is either lithium iron phosphate (LFP) or lithium nickel cobalt manganese oxide (LCO). Lithium iron phosphate (LFP) has excellent thermal stability (decomposition temperature > 300℃), making it suitable for high-temperature applications; LFP has higher energy density, making it suitable for applications emphasizing battery life. Both are mainstream positive electrode materials for start-stop batteries.

[0019] Furthermore, the negative electrode sheet includes a negative electrode current collector and a negative electrode material coated on the negative electrode current collector; The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder; The negative electrode active component is at least one of graphite and soft carbon.

[0020] Furthermore, the preparation method of the cyanosilicon phosphate is as follows: Under a nitrogen atmosphere, cyanogen bromide was weighed and added to a flask. Tris(trimethylsilyl)phosphite was weighed according to a molar ratio of 1:1 to cyanogen bromide and placed in a dropping funnel. The system was heated to 50-55°C, and tris(trimethylsilyl)phosphite was added dropwise while stirring. After the addition was complete, the reaction was continued at a constant temperature and stirred for 2-4 hours. The temperature was then raised to 60°C and the reaction was continued for 20-40 minutes. The reaction was completed, and the product was obtained by cooling.

[0021] The reaction formulas for the above preparation process are as follows:

[0022] This invention also provides a method for preparing a high-temperature resistant start-stop lithium battery, which includes the following steps: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell; Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0023] The beneficial effects of this invention are: (1) The lithium salt in the electrolyte of this invention adopts a ternary composite system of electrolyte inorganic lithium salt, lithium trifluoromethanesulfonylimide, and lithium difluorodioxanol phosphate. Lithium trifluoromethanesulfonylimide has high thermal stability and is resistant to hydrolysis, which can improve the thermal safety of the overall lithium salt system and inhibit the growth of lithium dendrites. Lithium difluorodioxanol phosphate can preferentially decompose on the electrode surface to form a dense and highly conductive ion-conducting interface film rich in LiF and PO components, which effectively blocks the continuous decomposition of the electrolyte and the dissolution of positive electrode metal ions at high temperatures. The three components work synergistically to significantly enhance the thermal stability and interfacial mechanochemical stability of the battery while ensuring the basic conductivity.

[0024] (2) Traditional carbonate electrolytes are prone to volatilization and oxidative decomposition at high temperatures. In this invention, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane are introduced into the chain carbonate base solvent. Fluoroethylene carbonate helps to form a low-impedance, stable SEI film. Vinyl ethoxyethyl acrylate can polymerize at high temperatures to form a polymer protective layer on the positive electrode surface, which inhibits the oxidative decomposition of the electrolyte and protects the positive electrode structure. The multiple cyano groups in 1,2-bis(2-cyanoethoxy)ethane can strongly complex with transition metal ions dissolved from the positive electrode, preventing them from damaging the negative electrode SEI film, thereby slowing down the high-temperature capacity decay.

[0025] (3) In this invention, an additive is added to the electrolyte. The additive tris(2-cyanoethyl) borate has both the film-forming promoting effect of borate and the metal ion chelating function of cyano. The designed and prepared cyanosilyl phosphate integrates siloxane chain (flexible and heat-resistant), phosphate group (flame-retardant film formation) and cyano (strong polar chelation). Its P=O / O-Si structure enhances the interfacial adsorption capacity. At high temperature, the additive can undergo a synergistic reaction with vinyl ethoxyethyl acrylate in the solvent to form a polymer-inorganic composite protective layer that combines chemical bonding and physical anchoring. This protective layer has elasticity, flame retardancy, strong ion chelating ability and good ion conductivity, which greatly improves the mechanical strength and high temperature stability of the SEI / CEI film.

[0026] (4) Through the synergistic effect of each component under optimized ratio, the electrolyte system can effectively suppress solvent decomposition, electrode structure collapse and harmful side reactions at high temperature, and construct a stable dual-electrode interface film with high ionic conductivity. The start-stop lithium battery prepared by this invention can exhibit excellent cycle life, capacity retention and safety under high temperature environment, and solves the pain point of severe performance degradation of existing start-stop batteries at high temperature. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Preparation Example 1

[0029] Preparation of cyanosilicon phosphate: Under a nitrogen atmosphere, cyanogen bromide was weighed and added to a flask. Tris(trimethylsilyl)phosphite was weighed according to a molar ratio of 1:1 to cyanogen bromide and placed in a dropping funnel. The system was heated to 55°C, and tris(trimethylsilyl)phosphite was added dropwise while stirring. After the addition was completed, the reaction was continued at a constant temperature and stirred for 3 hours. The temperature was then raised to 60°C and the reaction was continued for 30 minutes. The reaction was completed, and the product was obtained by cooling.

[0030] Example 1

[0031] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0032] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0033] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0034] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0035] The diaphragm is a PP / PE / PP three-layer membrane.

[0036] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0037] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0038] Example 2

[0039] The only difference from Example 1 is that the mass ratio of ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane in the solvent is adjusted to 1:1.8:0.2:0.15.

[0040] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0041] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.2:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0042] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0043] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0044] The diaphragm is a PP / PE / PP three-layer membrane.

[0045] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0046] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0047] Example 3

[0048] The only difference from Example 1 is that the mass ratio of ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane in the solvent is adjusted to 1:1.8:0.4:0.15.

[0049] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0050] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.4:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0051] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0052] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0053] The diaphragm is a PP / PE / PP three-layer membrane.

[0054] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0055] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0056] Example 4

[0057] The only difference from Example 1 is that the mass ratio of (2-cyanoethyl) borate ester and cyanosilicon phosphate ester (prepared in Preparation Example 1) in the additive is adjusted to 1:1.0.

[0058] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0059] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at a total electrolyte mass of 0.20%. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.0.

[0060] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0061] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0062] The diaphragm is a PP / PE / PP three-layer membrane.

[0063] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0064] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0065] Example 5

[0066] The only difference from Example 1 is that the mass ratio of (2-cyanoethyl) borate ester and cyanosilicon phosphate ester (prepared in Preparation Example 1) in the additive is adjusted to 1:1.4.

[0067] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0068] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.4.

[0069] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0070] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0071] The diaphragm is a PP / PE / PP three-layer membrane.

[0072] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0073] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0074] Example 6

[0075] The only difference from Example 1 is that the additive is adjusted to 0.12% of the total mass of the electrolyte.

[0076] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0077] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at a total electrolyte mass of 0.12%. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0078] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0079] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0080] The diaphragm is a PP / PE / PP three-layer membrane.

[0081] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0082] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0083] Example 7

[0084] The only difference from Example 1 is that the additive is adjusted to 0.30% of the total mass of the electrolyte.

[0085] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0086] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at a total electrolyte mass of 0.30%. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0087] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0088] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0089] The diaphragm is a PP / PE / PP three-layer membrane.

[0090] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0091] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0092] Example 8

[0093] The only difference from Example 1 is that the mass ratio of LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxalate phosphate in the lithium salt is adjusted to 1:0.6:0.15.

[0094] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0095] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.6:0.15. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0096] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0097] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0098] The diaphragm is a PP / PE / PP three-layer membrane.

[0099] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0100] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0101] Example 9

[0102] The only difference from Example 1 is that the mass ratio of LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxalate phosphate in the lithium salt is adjusted to 1:0.4:0.3.

[0103] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0104] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.4:0.3. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0105] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0106] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0107] The diaphragm is a PP / PE / PP three-layer membrane.

[0108] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0109] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0110] Comparative Example 1

[0111] The only difference from Example 1 is that cyanosilicon phosphate is not added to the electrolyte additive.

[0112] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0113] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate.

[0114] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0115] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0116] The diaphragm is a PP / PE / PP three-layer membrane.

[0117] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0118] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0119] Comparative Example 2

[0120] The only difference from Example 1 is that the electrolyte additive is replaced with tris(trimethylsilyl)phosphite instead of cyanosilicon phosphate.

[0121] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0122] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at a total electrolyte mass of 0.20%. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.3:0.15. The additive is (2-cyanoethyl) borate and tris(trimethylsilyl) phosphite, with a mass ratio of 1:1.2.

[0123] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0124] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0125] The diaphragm is a PP / PE / PP three-layer membrane.

[0126] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0127] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0128] Comparative Example 3

[0129] The only difference from Example 1 is that vinyl ethoxyethyl acrylate is not added to the electrolyte solvent.

[0130] A high-temperature resistant start-stop lithium battery includes a positive electrode, an electrolyte, a separator, a negative electrode, and an aluminum casing.

[0131] The electrolyte comprises a solvent, a lithium salt at a solvent concentration of 1.2 mol / L, and an additive at 0.20% of the total electrolyte mass. The lithium salt in the electrolyte is LiPF6, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate, with a mass ratio of 1:0.5:0.20. The solvent is ethylene carbonate, fluoroethylene carbonate, and 1,2-bis(2-cyanoethoxy)ethane, with a mass ratio of 1:1.8:0.15. The additive is (2-cyanoethyl) borate and cyanosilicon phosphate (prepared in Preparation Example 1), with a mass ratio of 1:1.2.

[0132] The positive electrode sheet includes a positive current collector and a positive electrode material coated on the current collector. The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder (PVDF) in a mass ratio of 95:3:2. The positive electrode active component is a ternary lithium nickel cobalt manganese oxide material, and the double-sided coating density of the positive electrode sheet is 120 g / m². 2 .

[0133] The negative electrode sheet comprises a negative electrode current collector and a negative electrode material coated on the current collector. The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder (SBR+CMC) in a mass ratio of 96:2:2. The negative electrode active component is artificial graphite, and the double-sided coating surface density of the negative electrode sheet is 75 g / m². 2 .

[0134] The diaphragm is a PP / PE / PP three-layer membrane.

[0135] Lithium-ion battery manufacturing: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell.

[0136] Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

[0137] The electrochemical performance of the lithium batteries prepared in Examples 1-9 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0138] 60℃ Cyclic Performance Test: The lithium batteries prepared in the examples and comparative examples were subjected to a cyclic performance test. The initial SOC of the cyclic test battery was 80%. The batteries were placed in a 60℃ constant temperature chamber and left to stand for 6 hours. They were charged at a constant current of 3C to 4.2V and then discharged at a constant current of 3C to 2.8V. This was recorded as one cycle. The above cycle was repeated. After 300 cycles, the capacity retention rate of the battery was tested.

[0139] 80°C High Temperature Test: Prepare lithium batteries for the examples and comparative examples. Test the initial SOC of the batteries = 80%. Place the lithium batteries prepared for the examples and comparative examples in an 80°C constant temperature chamber for 32 hours. Charge them at 3C constant current to 4.2V and then discharge them at 3C constant current to 2.8V. Calculate the capacity retention rate of the batteries.

[0140] Table 1

[0141] As shown in Table 1, the high-temperature cycle performance of the lithium battery in Example 1 of this invention is significantly better than that in Comparative Examples 1 and 2. The cyanosilicon phosphate additive enhances the battery's high-temperature resistance, enabling it to exhibit excellent cycle life as a start-stop lithium battery under high-temperature conditions. Combining the test results of Example 1 and Comparative Example 3, the addition of vinyl ethoxyethyl acrylate can slow down the capacity decay of the battery at high temperatures and improve its high-temperature stability.

[0142] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0143] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant start-stop lithium battery, characterized in that, It includes the positive electrode, electrolyte, separator, negative electrode, and aluminum shell; The electrolyte includes lithium salt, additives, and solvent; The lithium salt includes electrolyte inorganic lithium salt, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate. The solvents include chain carbonates, fluoroethylene carbonates, vinyl ethoxyethyl acrylates, and 1,2-bis(2-cyanoethoxy)ethane. The additives include tris(2-cyanoethyl)borate and cyanosilicon phosphate; The structural formula of the cyanosilyl phosphate is as follows: 。 2. The high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The lithium salt concentration in the solvent is 1-1.5 mol / L.

3. The high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The additive is 0.12-0.30% of the electrolyte mass.

4. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The electrolyte inorganic lithium salt is one of LiPF6 and LiBF4.

5. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The mass ratio of the electrolyte inorganic lithium salt, lithium trifluoromethanesulfonylimide, and lithium difluorodioxane phosphate in the lithium salt is 1:(0.4-0.6):(0.15-0.3).

6. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The mass ratio of the chain carbonate, fluoroethylene carbonate, vinyl ethoxyethyl acrylate, and 1,2-bis(2-cyanoethoxy)ethane in the solvent is 1:(1.5-2.0):(0.2-0.4):(0.1-0.2).

7. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The mass ratio of the tris(2-cyanoethyl)boronic acid ester to the cyanosilicon phosphate ester is 1:(1.0-1.4).

8. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode material coated on the positive current collector; The positive electrode material includes a positive electrode active component, conductive carbon black, and a positive electrode binder; The positive electrode active component is one of lithium iron phosphate material and ternary lithium nickel cobalt manganese oxide material; The negative electrode sheet includes a negative electrode current collector and a negative electrode material coated on the negative electrode current collector; The negative electrode material includes a negative electrode active component, conductive carbon black, and a negative electrode binder; The negative electrode active component is at least one of graphite and soft carbon.

9. A high-temperature resistant start-stop lithium battery according to claim 1, characterized in that, The preparation method of the cyanosilicon phosphate is as follows: Under a nitrogen atmosphere, cyanogen bromide was weighed and added to a flask. Tris(trimethylsilyl)phosphite was weighed according to a molar ratio of 1:1 to cyanogen bromide and placed in a dropping funnel. The system was heated to 50-55°C, and tris(trimethylsilyl)phosphite was added dropwise while stirring. After the addition was complete, the reaction was continued at a constant temperature and stirred for 2-4 hours. The temperature was then raised to 60°C and the reaction was continued for 20-40 minutes. The reaction was completed, and the product was obtained by cooling.

10. A method for preparing a high-temperature resistant start-stop lithium battery, characterized in that, The method for preparing a high-temperature resistant start-stop lithium battery as described in any one of claims 1-9 includes the following steps: Step 1: Stack the positive electrode, separator, and negative electrode in sequence to form a bare cell; Step 2: Place the bare battery cell inside the aluminum shell, weld it, inject electrolyte, and then obtain the lithium battery through sealing, formation, and capacity testing processes.

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