A lithium-ion battery

Abstract

This invention provides a lithium-ion battery comprising a positive electrode and an electrolyte; the positive electrode comprises lithium iron phosphate as the positive electrode active material; the electrolyte comprises additive a and additive b; additive a comprises vinylene carbonate; additive b comprises a compound with the structure shown in formula (I) and a compound with the structure shown in formula (II). This invention uses two additives in combination to partially replace vitamin C, reducing the amount of vitamin C required. Furthermore, compared to the SEI formed by the reduction of vitamin C, the SEI structures formed by the compounds with the structures shown in formula (I) and (II) are more dense, exhibiting a stronger effect in suppressing interfacial side reactions and providing better improvement in high-temperature cycling compared to vitamin C.

Description

[0001] This application is a divisional application filed on December 27, 2024, with application number 202411952747.7, entitled "A Lithium-ion Battery". Technical Field

[0002] This invention belongs to the technical field of lithium iron phosphate battery electrolyte additives, and relates to a lithium-ion battery, particularly a lithium-ion battery, and the application of additives in lithium-ion battery electrolytes in reducing the amount of vinylene carbonate used in the electrolyte. Background Technology

[0003] Lithium iron phosphate (LFP) batteries are lithium-ion batteries that use lithium iron phosphate (LiFePO4) as the positive electrode material. LFP batteries possess a series of unique advantages, including high operating voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, and environmental friendliness. They also support stepless expansion, making them suitable for large-scale energy storage. They show promising application prospects in areas such as safe grid connection of renewable energy power plants, grid peak shaving, distributed power stations, UPS power supplies, and emergency power systems. Especially with the booming development of the electric vehicle industry in recent years, LFP batteries have captured a significant share in practical commercial applications. Furthermore, the continuous development of downstream application industries is placing higher demands on LFP batteries.

[0004] Lithium-ion batteries with lithium iron phosphate / graphite have always suffered from poor high-temperature cycling and storage performance. Although the addition of vinylene carbonate (VC) to the electrolyte can improve this, VC improves the cycling performance by encapsulating the graphite anode material and avoiding side reactions between the anode material and the electrolyte. However, VC's improvement on high-temperature cycling is limited and still cannot meet the requirements.

[0005] Therefore, finding a more suitable way to solve the aforementioned technical problems of existing lithium iron phosphate batteries has become one of the urgent problems to be solved by many leading researchers and scientific research companies in this field. Summary of the Invention

[0006] In view of this, the present invention provides an application of additives in lithium-ion batteries and lithium-ion battery electrolytes in reducing the amount of vinylene carbonate used in the electrolyte. The present invention employs a combination of additives with specific structures, resulting in a stronger inhibition of interfacial side reactions and a better improvement in high-temperature cycling performance compared to vinylene carbonate (VC).

[0007] This invention provides a lithium-ion battery, which includes a positive electrode and an electrolyte; The positive electrode sheet includes lithium iron phosphate as the positive electrode active material; The electrolyte includes additive a and additive b; The additive a includes vinylene carbonate; The additive b includes compounds with the structure shown in formula (I) and compounds with the structure shown in formula (II); ; In formula (I), M is selected from fluorinated or non-fluorinated C1-C4 alkyl groups; In equation (II), R1, R2, and R3 are each independently selected from H or -C. n H 2n+1 , where n ≤ 4; R4, R5, and R6 are each independently selected from vinyl, allyl, oxyvinyl, or oxyallyl; R7, R8, and R9 are each independently selected from hydrogen, methyl, or ethyl; The cohesive force of the positive electrode sheet, vinylene carbonate, the compound with the structure shown in formula (I), and the compound with the structure shown in formula (II) satisfy the following relationship: 50≤m×(a+b)≤600 (1); Where m is the cohesive force of the positive electrode sheet, in N / m; a is the mass percentage of vinylene carbonate in the electrolyte; and b is the sum of the mass percentages of the compounds with the structure shown in formula (I) and the compounds with the structure shown in formula (II) in the electrolyte. In the electrolyte, the mass content of the compound with the structure shown in formula (I) is 0.1% to 2.5%; In the electrolyte, the mass content of the compound with the structure shown in formula (II) is 0.1% to 0.6%.

[0008] This invention provides a lithium-ion battery. Compared with existing technologies, this invention argues that lithium iron phosphate batteries have poor high-temperature cycle performance. Although adding VC additive to the electrolyte can improve high-temperature cycle and storage performance, the improvement effect of VC on high-temperature cycle performance is limited, and excessive VC content will cause excessive impedance. Therefore, the VC content cannot be too high. Based on this, this invention specifically designs two additives with specific structures to be used in combination in the electrolyte of lithium iron phosphate batteries, thereby further improving the high-temperature performance of lithium iron phosphate batteries. Among them, the additive with the structure shown in formula (I) can improve high-temperature performance. After its addition, the amount of VC can be reduced, ensuring high-temperature performance while maintaining low impedance. The additive with the structure shown in formula (II) has better high-temperature performance than VC. Adding a small amount of the additive with the structure shown in formula (II) to match VC can also reduce the amount of VC and obtain even better high-temperature performance.

[0009] The electrolyte of the lithium iron phosphate battery provided by this invention contains an alkoxycarbonyl isothiocyanate compound with the structure shown in formula (I) and an alkenylalkyltrisilazane compound with the structure shown in formula (II). The compound with the structure shown in formula (I) is reduced at the negative electrode to form polythioamide, which is resistant to high temperatures and forms a stable SEI film with low impedance, thus improving the high-temperature cycling and storage performance of the lithium iron phosphate battery while improving its power. The compound with the structure shown in formula (II) can undergo polymerization and ring-opening reactions at the negative electrode, and the resulting SEI has a good electronic passivation effect on the interface, reducing interfacial side reactions on the negative electrode side and improving the high-temperature cycling and storage performance of the battery. This invention uses two additives in combination to partially replace VC, reducing the amount of VC added. Moreover, compared with the SEI formed by the reduction of VC, the SEI structure formed by the compounds with the structures shown in formula (I) and (II) is more dense and has a stronger effect in suppressing interfacial side reactions. Therefore, it is more effective than VC in improving high-temperature cycling. Detailed Implementation

[0010] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0012] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity materials used in the field of lithium-ion battery electrolytes.

[0013] This invention provides a lithium-ion battery, which includes a positive electrode and an electrolyte; The positive electrode includes lithium iron phosphate (LiFePO4) as the positive electrode active material. The electrolyte includes additive a and additive b; The additive a includes vinylene carbonate; The additive b includes compounds with the structure shown in formula (I) and compounds with the structure shown in formula (II); ; In formula (I), M is selected from fluorinated or non-fluorinated C1-C4 alkyl groups; In equation (II), R1, R2, and R3 are each independently selected from H or -C. n H 2n+1, where n ≤ 4; R4, R5, and R6 are each independently selected from vinyl, allyl, oxyvinyl, or oxyallyl; R7, R8, and R9 are each independently selected from hydrogen, methyl, or ethyl; The cohesive force of the positive electrode sheet, vinylene carbonate, the compound with the structure shown in formula (I), and the compound with the structure shown in formula (II) satisfy the following relationship: 50≤m×(a+b)≤600 (1); Where m is the cohesive force of the positive electrode sheet, in N / m; a is the mass percentage of vinylene carbonate in the electrolyte; and b is the sum of the mass percentages of the compounds with the structure shown in formula (I) and the compounds with the structure shown in formula (II) in the electrolyte. In the electrolyte, the mass content of the compound with the structure shown in formula (I) is 0.1% to 2.5%; In the electrolyte, the mass content of the compound with the structure shown in formula (II) is 0.1% to 0.6%.

[0014] In this invention, M is selected from fluorinated or non-fluorinated C1-C4 alkyl groups, or M is selected from fluorinated or non-fluorinated C2-C3 alkyl groups. Specifically, M can be fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, methyl, ethyl, propyl, or butyl.

[0015] In this invention, in equation (II), n ≤ 4, or n ≤ 3, or n ≤ 2. Specifically, n can be 1, 2, 3, or 4.

[0016] This invention employs alkoxycarbonyl isothiocyanate compounds with the structure shown in Formula (I) and alkenylalkyltrisilazane compounds with the structure shown in Formula (II). The compound with the structure shown in Formula (I) is reduced at the negative electrode to form polythioamide, which is heat-resistant and produces a stable SEI film with low impedance, ensuring high-temperature cycling and storage performance of the lithium iron phosphate battery while improving its power output. The compound with the structure shown in Formula (II) can undergo polymerization and ring-opening reactions at the negative electrode, generating an SEI that provides excellent electronic passivation at the interface, reducing interfacial side reactions on the negative electrode side and improving the battery's high-temperature cycling and storage performance. This invention uses two additives in combination to partially replace vitamin C, reducing the amount of vitamin C required. Furthermore, compared to the SEI formed by the reduction of vitamin C, the SEI structures formed by the compounds with the structures shown in Formula (I) and (II) are more dense and have a stronger effect in suppressing interfacial side reactions, thus providing better improvement in high-temperature cycling performance compared to vitamin C.

[0017] In this invention, the compound with the structure shown in formula (I) preferably includes at least one of the compounds with the structures shown in formulas (I1) to (I17): .

[0018] Furthermore, the compound with the structure shown in formula (I) is preferably an ethoxycarbonyl isothiocyanate, i.e., a compound with the structure shown in formula (I5).

[0019] The chemical compounds of the present invention with the structure of formula (I) are preferably compounds with the structure shown in formula (I5), and the battery has better cycle performance and storage performance.

[0020] In this invention, the compound with the structure shown in formula (II) preferably includes at least one of the compounds with the structures shown in formulas (II1) to (II16): .

[0021] Furthermore, the compound with the structure shown in formula (II) is preferably trivinyltrimethylcyclotrisilazane, i.e., the compound with the structure shown in formula (II13).

[0022] The chemical compound of the present invention with the structure of formula (II) is preferably a compound with the structure shown in formula (I5), and the battery has better high-temperature performance.

[0023] Lithium iron phosphate batteries have poor high-temperature cycle performance. Adding VC to the electrolyte can improve high-temperature cycle and storage performance. However, if the VC content is too high, it will cause excessive impedance. Therefore, the VC content cannot be too high. Additives of formula (I), such as ethoxycarbonyl isothiocyanate, can improve high-temperature performance. After addition, the amount of VC can be reduced, ensuring high-temperature performance while maintaining low impedance. Additive trivinyltrimethylcyclotrisilazane has better high-temperature performance than VC. Adding a small amount of additive of formula (II), such as trivinyltrimethylcyclotrisilazane, to match VC can also reduce the amount of VC and obtain better high-temperature performance.

[0024] In this invention, the mass content of the compound with the structure shown in formula (I) in the electrolyte is preferably 0.1% to 2.5%, more preferably 0.5% to 2.2%. In this invention, if the mass content of the compound with the structure shown in formula (I) is too low, a stable SEI film cannot be formed on the negative electrode; if it is too high, gas generation will occur, causing the battery to swell.

[0025] In this invention, the mass content of the compound with the structure shown in formula (II) in the electrolyte is preferably 0.1% to 0.6%, more preferably 0.2% to 0.5%. In this invention, if the mass content of the compound with the structure shown in formula (II) is too low, a stable SEI film cannot be formed on the negative electrode; if it is too high, the impedance will increase.

[0026] In this invention, additive formula (I) generates polythioamide at the negative electrode, resulting in multiple ion pathways, low interfacial impedance, and a stable SEI film. This improves the kinetic performance of the lithium iron phosphate battery while ensuring its high-temperature cycling and storage performance. However, excessive addition of additive formula (I) can increase gas production. Additive formula (II) undergoes polymerization and ring-opening reactions at the negative electrode, generating an SEI that provides excellent electronic passivation at the interface. However, it has fewer ion pathways and high interfacial impedance, meaning that while additive formula (II) improves the battery's high-temperature cycling and storage performance, it can degrade the battery's kinetic performance. Therefore, this invention further specifies the relationship between the content b1 of additive formula (I) and the content b2 of additive formula (II).

[0027] In this invention, the mass content of additive b in the electrolyte is preferably 0.1% to 3%, that is, the mass percentage of the compound with the structure shown in formula (I) is denoted as b1%, the mass percentage of the compound with the structure shown in formula (II) is denoted as b2%, b = b1 + b2, 0.1 ≤ b1 + b2 ≤ 3.0, and more preferably 0.5 to 2.5%.

[0028] In this invention, the mass ratio of the compound with the structure shown in formula (I) to the compound with the structure shown in formula (II) is preferably (1~15):1, that is, 1≤b1 / b2≤15. More preferably, it is (3~13):1.

[0029] In this invention, the mass content of vinylene carbonate in the electrolyte is preferably 0.5% to 2.5%, more preferably 0.5% to 2.0%. In this invention, if the mass content of vinylene carbonate is too low, the negative electrode side reaction increases; if it is too high, the coating effect on the negative electrode is too good, resulting in high impedance.

[0030] In this invention, the mass ratio of the compound with the structure shown in formula (I) to the compound with the structure shown in formula (II) to the mass of vinylene carbonate is preferably (0.2~2):1, more preferably (0.5~1.8):1. By maintaining the total mass of the compound with the structure shown in formula (I) and the compound with the structure shown in formula (II) and the mass ratio of VC within the above range, this invention results in better high-temperature performance and lower impedance of the battery.

[0031] In this invention, the preferred mass ratio of the vinylene carbonate to the compound with the structure shown in formula (I) is (0.5~5):1. By maintaining this ratio within the above range, the battery exhibits higher high-temperature performance, lower impedance, and less gas production.

[0032] In this invention, the preferred mass ratio of the vinylene carbonate to the compound with the structure shown in formula (II) is (2~10):1. Maintaining this ratio within the above range results in better high-temperature battery performance and avoids causing greater impedance.

[0033] In this invention, the positive electrode preferably includes a current collector and a positive electrode material coating laminated on the current collector.

[0034] In lithium-ion batteries, cohesion reflects the binding force between the positive electrode active material particles. Under suitable cohesion, the positive electrode sheet has good structural stability, which helps reduce the risk of iron dissolution during charging and discharging due to weak binding forces between positive electrode active material particles, resulting in exposed positive electrode particles and increased side reactions in the electrolyte. Increased iron dissolution allows dissolved iron ions to shuttle to the negative electrode and precipitate on its surface, causing loss of active lithium and reducing battery cycle life. At the same time, the iron deposited on the negative electrode exists in elemental form and acts as an active center, making the electrolyte more prone to reduction, increasing side reactions between the negative electrode and the electrolyte, and reducing the battery's high-temperature cycle performance.

[0035] This invention comprehensively considers the relationship between the cohesive force of the positive electrode, the VC content, and the additive content b. At high temperatures, lithium iron phosphate (LiFePO4) experiences increased iron leaching, which reaches the negative electrode, leading to increased side reactions between the negative electrode and the electrolyte. By increasing the cohesive force of the positive electrode, the electrode material is less prone to breakage, resulting in less exposed active surface area, less iron leaching, and fewer side reactions between the electrolyte and the material. This reduces the amount of VC and the content of additive b. When the cohesive force of the positive electrode is relatively low, the risk of iron leaching increases, requiring an increase in the sum of the VC content and the additive b content. Therefore, the value of m×(a+b) must be maintained within a certain range to ensure the high-temperature cycle performance of the battery.

[0036] In this invention, the cohesive force of the positive electrode sheet, vinylene carbonate, the compound with the structure shown in formula (I), and the compound with the structure shown in formula (II) preferably satisfy the following relationship: 50≤m×(a+b)≤600 (1); Where m is the cohesive force of the positive electrode sheet, in N / m; a% is the mass percentage of vinylene carbonate in the electrolyte; and b% is the sum of the mass percentages of the compounds with the structure shown in formula (I) and the compounds with the structure shown in formula (II) in the electrolyte.

[0037] Specifically, m×(a+b) can also be 100~500, or 200~400.

[0038] In this invention, the cohesive force of the positive electrode sheet preferably satisfies: 20≤m≤200, more preferably 50≤m≤180, and even more preferably 70≤m≤150. This invention controls the cohesive force within a suitable range, resulting in better structural stability of the positive electrode sheet and reducing the likelihood of exposed positive electrode material particles. It also avoids the need for special designs to achieve higher cohesive force, such as adding more binder, which would reduce the proportion of active material responsible for battery capacity and hinder capacity utilization.

[0039] In this invention, the mass percentage of the vinylene carbonate in the electrolyte, the mass percentage of the compound with the structure shown in formula (I) and the mass percentage of the compound with the structure shown in formula (II) in the electrolyte preferably satisfy: 0.1≤a+b≤5, more preferably 0.5≤a+b≤4.5, more preferably 1.0≤a+b≤4.0, more preferably 1.5≤a+b≤3.5, and more preferably 2.0≤a+b≤3.0.

[0040] In this invention, when the cohesive force m of the positive electrode sheet is less than or equal to 60, b / a is preferably greater than or equal to 2.5.

[0041] In this invention, when the cohesive force of the positive electrode sheet is less than a certain value, the risk of iron dissolution increases. Additive b improves the high-temperature cycle performance of the battery better than VC. Therefore, when the cohesive force of the positive electrode sheet is smaller, by controlling the sum of the VC content and the additive b content within the above range, the high-temperature cycle performance of the battery can be better improved.

[0042] In this invention, the method of adjusting the cohesion of the positive electrode is not limited. Specifically, it can be adjusted by the amount and type of binder.

[0043] In this invention, the lithium-ion battery preferably includes a negative electrode.

[0044] In this invention, the negative electrode preferably comprises a negative electrode active material. Specifically, the negative electrode active material preferably comprises graphite and / or silicon-based materials.

[0045] The present invention provides the application of compounds with the structure shown in formula (I) and compounds with the structure shown in formula (II) as additives in lithium-ion battery electrolytes to reduce the amount of vinylene carbonate used in the electrolyte.

[0046] The lithium-ion battery provided by this invention includes a positive electrode sheet, the active material layer of which includes lithium iron phosphate, and an electrolyte additive including VC (ethylene carbonate) at a mass percentage of a%. It also includes an additive X, which is selected from one or more of substance A (Formula I) and substance B (Formula II) (wherein the mass percentage of substance A is denoted as b1%, and the mass percentage of substance B is denoted as b2%). M is selected from fluorinated or non-fluorinated alkyl groups with 4 or fewer carbon atoms, such as fluorinated methyl, fluorinated ethyl, fluorinated propyl, fluorinated butyl, methyl, ethyl, propyl, and butyl. R1, R2, and R3 are independently selected from H or -C. n H 2n+1 Where n ≤ 4, R4, R5, and R6 are independently selected from vinyl, allyl, oxyvinyl, or oxyallyl, and R7, R8, and R9 are independently selected from H, methyl, or ethyl; .

[0047] In this invention, the application preferably includes the application of the compound with the structure shown in formula (I) in improving the high-temperature performance and / or storage performance of lithium-ion batteries, and more preferably the application of the compound with the structure shown in formula (I) in improving the high-temperature performance and storage performance of lithium-ion batteries.

[0048] In this invention, the application preferably includes the application of the compound with the structure shown in formula (II) in improving the high-temperature performance and / or storage performance of lithium-ion batteries, and more preferably the application of the compound with the structure shown in formula (II) in improving the high-temperature performance and storage performance of lithium-ion batteries.

[0049] The present invention provides an application of additives in lithium-ion batteries and lithium-ion battery electrolytes in reducing the amount of vinylene carbonate used in the electrolyte. The present invention specifically designs two additives with specific structures that are used in combination in the electrolyte of lithium iron phosphate batteries, thereby further improving the high-temperature performance of lithium iron phosphate batteries. Specifically, the additive with the structure shown in formula (I) can improve high-temperature performance; its addition can reduce the amount of VC used, ensuring high-temperature performance while maintaining low impedance. The additive with the structure shown in formula (II) has superior high-temperature performance compared to VC; adding a small amount of trivinyltrimethylcyclotrisilazane to match VC can also reduce the amount of VC used, while obtaining even better high-temperature performance.

[0050] The electrolyte of the lithium iron phosphate battery provided by this invention contains an alkoxycarbonyl isothiocyanate compound with the structure shown in formula (I) and an alkenylalkyltrisilazane compound with the structure shown in formula (II). The compound with the structure shown in formula (I) is reduced at the negative electrode to form polythioamide, which is resistant to high temperatures and forms a stable SEI film with low impedance, thus improving the high-temperature cycling and storage performance of the lithium iron phosphate battery while improving its power. The compound with the structure shown in formula (II) can undergo polymerization and ring-opening reactions at the negative electrode, and the resulting SEI has a good electronic passivation effect on the interface, reducing interfacial side reactions on the negative electrode side and improving the high-temperature cycling and storage performance of the battery. This invention uses two additives in combination to partially replace VC, reducing the amount of VC added. Moreover, compared with the SEI formed by the reduction of VC, the SEI structure formed by the compounds with the structures shown in formula (I) and (II) is more dense and has a stronger effect in suppressing interfacial side reactions. Therefore, it is more effective than VC in improving high-temperature cycling.

[0051] Furthermore, this invention also comprehensively considers the relationship between the cohesive force of the positive electrode, the VC content, and the additive content. At high temperatures, iron dissolution in lithium iron phosphate increases, reaching the negative electrode and causing increased side reactions between the negative electrode and the electrolyte. By increasing the cohesive force of the positive electrode, the electrode material is less prone to breakage, resulting in less exposed active material area, less iron dissolution, and fewer side reactions between the electrolyte and the material. This allows for a better reduction in the amount of VC and the content of additives. When the cohesive force of the positive electrode is relatively small, the risk of iron dissolution increases, so the sum of the VC content and the additive content must increase. Therefore, cohesive force × (VC content + additive content) must be kept within a certain range to better ensure the high-temperature cycle performance of the lithium iron phosphate battery.

[0052] To further illustrate the present invention, the following embodiments provide a detailed description of the application of additives in the electrolyte of a lithium-ion battery and the lithium-ion battery in reducing the amount of vinylene carbonate in the electrolyte. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0053] The present invention does not limit the method for detecting cohesive force. Those skilled in the art can detect the cohesive force of the positive electrode using conventional technical means. For example, the following method can be used for detection:

[0054] The battery was discharged at 0.33C, with a cutoff voltage of 2.5V. The positive electrode was removed and soaked in dimethyl carbonate (DMC) for 2 hours, then dried at 80°C.

[0055] Take a standard steel plate (50mm x 125mm) as the rigidity test base and wipe the surface of the steel plate clean with lint-free paper soaked in alcohol. Adhere one side of the 50mm x 125mm 3M double-sided tape to the steel plate, ensuring a smooth, wrinkle-free adhesion. Cut the positive electrode sheet with an active coating into a 50mm x 125mm sample for testing. Adhere the electrode sheet to be tested to the other adhesive side of the double-sided tape, and then apply another layer of double-sided tape to the electrode sheet surface, ensuring a smooth, wrinkle-free contact during the adhesion process. After pressing with a pressure roller, clamp the steel plate with one end of the universal testing machine's tensile grips and the 3M tape with the other end. Set the tensile testing machine's stroke to 100mm and perform a tensile test at a speed of 300mm / min. Set the tensile testing machine's stroke to 100m and record the curve in the tensile testing machine's software graph until it flattens out and the displacement is greater than 80mm, then stop the machine. The average tensile force value of the flattened portion of the curve is the cohesive force.

[0056] Test methods for VC content and additive (Formula 1 and / or Formula 2) content: The battery was discharged using a battery charging and discharging device under the following conditions: current 0.3C, cutoff voltage 2.5V. After recording the battery number / barcode, the battery was disassembled and the electrolyte collected in a glove box (H2O≤0.1ppm, O2≤0.1ppm). There are two methods for collecting the electrolyte: After removing the battery cover, ① if there is free electrolyte, collect it into a 5mL sample tube using a pipette and seal it with sealing tape to prevent leakage. ② if there is no free electrolyte, a hydraulic press (Beijing Heng'ao Technology Co., Ltd.'s FY-30 hydraulic press) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into a sample tube and seal it. ③ Add an appropriate amount of dichloromethane extractant to the battery and record the dichloromethane content. After adding dichloromethane, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Transfer it to an ultrasonic oscillator and oscillate for 12 hours to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of dichloromethane and electrolyte into a 5 mL sample tube and seal the sample tube with sealing glue. Inject the collected electrolyte sample into an Agilent Intuvo 9000 gas chromatograph-mass spectrometer using a microsyringe to obtain the GC-MS spectrum. Prepare EMC solutions of different concentrations using VC, formulas I1-I17, and II1-II16, and inject them into the Agilent Intuvo 9000 gas chromatograph-mass spectrometer to obtain the GC-MS spectrum of the standard substances. The GC-MS spectrum of the electrolyte to be tested is compared with that of a standard GC-MS spectrum to determine whether the electrolyte contains VC, formulas I1-I17, or formulas II1-II16 (for example, if a peak appears in the standard spectrum at the position where VC is located, the electrolyte is considered to contain VC; the same applies to other components). Then, the content of each component is determined based on its peak area.

[0057] Example 1

[0058] The battery was fabricated and tested according to the following process steps.

[0059] (1) Preparation of positive electrode sheet

[0060] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0061] (2) Preparation of negative electrode sheet

[0062] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0063] (3) Preparation of electrolyte

[0064] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. VC, additive b1 (ethoxycarbonyl isothiocyanate), and additive b2 (trivinyltrimethylcyclotrisilazane) were then added and thoroughly mixed.

[0065] (4) Preparation of the separating membrane

[0066] Polyethylene film was selected as the separator.

[0067] (5) Preparation of lithium-ion batteries

[0068] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0069] Example 2

[0070] The battery was fabricated and tested according to the following process steps.

[0071] (1) Preparation of positive electrode sheet

[0072] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0073] (2) Preparation of negative electrode sheet

[0074] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0075] (3) Preparation of electrolyte

[0076] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0077] (4) Preparation of the separating membrane

[0078] Polyethylene film was selected as the separator.

[0079] (5) Preparation of lithium-ion batteries

[0080] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0081] Example 3

[0082] The battery was fabricated and tested according to the following process steps.

[0083] (1) Preparation of positive electrode sheet

[0084] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0085] (2) Preparation of negative electrode sheet

[0086] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0087] (3) Preparation of electrolyte

[0088] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0089] (4) Preparation of the separating membrane

[0090] Polyethylene film was selected as the separator.

[0091] (5) Preparation of lithium-ion batteries

[0092] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0093] Example 4

[0094] The battery was fabricated and tested according to the following process steps.

[0095] (1) Preparation of positive electrode sheet

[0096] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0097] (2) Preparation of negative electrode sheet

[0098] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0099] (3) Preparation of electrolyte

[0100] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0101] (4) Preparation of the separating membrane

[0102] Polyethylene film was selected as the separator.

[0103] (5) Preparation of lithium-ion batteries

[0104] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0105] Example 5

[0106] The battery was fabricated and tested according to the following process steps.

[0107] (1) Preparation of positive electrode sheet

[0108] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0109] (2) Preparation of negative electrode sheet

[0110] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0111] (3) Preparation of electrolyte

[0112] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0113] (4) Preparation of the separating membrane

[0114] Polyethylene film was selected as the separator.

[0115] (5) Preparation of lithium-ion batteries

[0116] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0117] Example 6

[0118] The battery was fabricated and tested according to the following process steps.

[0119] (1) Preparation of positive electrode sheet

[0120] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0121] (2) Preparation of negative electrode sheet

[0122] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0123] (3) Preparation of electrolyte

[0124] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0125] (4) Preparation of the separating membrane

[0126] Polyethylene film was selected as the separator.

[0127] (5) Preparation of lithium-ion batteries

[0128] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0129] Example 7

[0130] The battery was fabricated and tested according to the following process steps.

[0131] (1) Preparation of positive electrode sheet

[0132] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0133] (2) Preparation of negative electrode sheet

[0134] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0135] (3) Preparation of electrolyte

[0136] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0137] (4) Preparation of the separating membrane

[0138] Polyethylene film was selected as the separator.

[0139] (5) Preparation of lithium-ion batteries

[0140] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0141] Example 8

[0142] The battery was fabricated and tested according to the following process steps.

[0143] (1) Preparation of positive electrode sheet

[0144] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0145] (2) Preparation of negative electrode sheet

[0146] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0147] (3) Preparation of electrolyte

[0148] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0149] (4) Preparation of the separating membrane

[0150] Polyethylene film was selected as the separator.

[0151] (5) Preparation of lithium-ion batteries

[0152] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0153] Example 9

[0154] The battery was fabricated and tested according to the following process steps.

[0155] (1) Preparation of positive electrode sheet

[0156] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0157] (2) Preparation of negative electrode sheet

[0158] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0159] (3) Preparation of electrolyte

[0160] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0161] (4) Preparation of the separating membrane

[0162] Polyethylene film was selected as the separator.

[0163] (5) Preparation of lithium-ion batteries

[0164] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0165] Example 10

[0166] The battery was fabricated and tested according to the following process steps.

[0167] (1) Preparation of positive electrode sheet

[0168] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0169] (2) Preparation of negative electrode sheet

[0170] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0171] (3) Preparation of electrolyte

[0172] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0173] (4) Preparation of the separating membrane

[0174] Polyethylene film was selected as the separator.

[0175] (5) Preparation of lithium-ion batteries

[0176] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0177] Example 11

[0178] The battery was fabricated and tested according to the following process steps.

[0179] (1) Preparation of positive electrode sheet

[0180] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0181] (2) Preparation of negative electrode sheet

[0182] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0183] (3) Preparation of electrolyte

[0184] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0185] (4) Preparation of the separating membrane

[0186] Polyethylene film was selected as the separator.

[0187] (5) Preparation of lithium-ion batteries

[0188] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0189] Example 12

[0190] The battery was fabricated and tested according to the following process steps.

[0191] (1) Preparation of positive electrode sheet

[0192] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.84:0.16. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0193] (2) Preparation of negative electrode sheet

[0194] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0195] (3) Preparation of electrolyte

[0196] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0197] (4) Preparation of the separating membrane

[0198] Polyethylene film was selected as the separator.

[0199] (5) Preparation of lithium-ion batteries

[0200] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0201] Example 13

[0202] The battery was fabricated and tested according to the following process steps.

[0203] (1) Preparation of positive electrode sheet

[0204] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.04:0.96. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0205] (2) Preparation of negative electrode sheet

[0206] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0207] (3) Preparation of electrolyte

[0208] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0209] (4) Preparation of the separating membrane

[0210] Polyethylene film was selected as the separator.

[0211] (5) Preparation of lithium-ion batteries

[0212] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0213] Example 14

[0214] The battery was fabricated and tested according to the following process steps.

[0215] (1) Preparation of positive electrode sheet

[0216] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.68:0.32. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0217] (2) Preparation of negative electrode sheet

[0218] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0219] (3) Preparation of electrolyte

[0220] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0221] (4) Preparation of the separating membrane

[0222] Polyethylene film was selected as the separator.

[0223] (5) Preparation of lithium-ion batteries

[0224] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0225] Example 15

[0226] The battery was fabricated and tested according to the following process steps.

[0227] (1) Preparation of positive electrode sheet

[0228] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.68:0.32. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0229] (2) Preparation of negative electrode sheet

[0230] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0231] (3) Preparation of electrolyte

[0232] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0233] (4) Preparation of the separating membrane

[0234] Polyethylene film was selected as the separator.

[0235] (5) Preparation of lithium-ion batteries

[0236] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0237] Example 16

[0238] The battery was fabricated and tested according to the following process steps.

[0239] (1) Preparation of positive electrode sheet

[0240] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.68:0.32. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0241] (2) Preparation of negative electrode sheet

[0242] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0243] (3) Preparation of electrolyte

[0244] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C, additive b1, and additive b2 were added and mixed thoroughly.

[0245] (4) Preparation of the separating membrane

[0246] Polyethylene film was selected as the separator.

[0247] (5) Preparation of lithium-ion batteries

[0248] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0249] Comparative Example 1

[0250] The battery was fabricated and tested according to the following process steps.

[0251] (1) Preparation of positive electrode sheet

[0252] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0253] (2) Preparation of negative electrode sheet

[0254] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0255] (3) Preparation of electrolyte

[0256] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, vitamin C was added and mixed thoroughly.

[0257] (4) Preparation of the separating membrane

[0258] Polyethylene film was selected as the separator.

[0259] (5) Preparation of lithium-ion batteries

[0260] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0261] Comparative Example 2

[0262] The battery was fabricated and tested according to the following process steps.

[0263] (1) Preparation of positive electrode sheet

[0264] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0265] (2) Preparation of negative electrode sheet

[0266] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0267] (3) Preparation of electrolyte

[0268] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Additive b1 was then added and mixed thoroughly.

[0269] (4) Preparation of the separating membrane

[0270] Polyethylene film was selected as the separator.

[0271] (5) Preparation of lithium-ion batteries

[0272] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0273] Comparative Example 3

[0274] The battery was fabricated and tested according to the following process steps.

[0275] (1) Preparation of positive electrode sheet

[0276] Lithium iron phosphate, acetylene black, and PVDF binder were mixed at a mass ratio of 98:1.2:0.8. NMP solvent was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained.

[0277] (2) Preparation of negative electrode sheet

[0278] The negative electrode active material graphite, conductive agent acetylene black, and binder SBR are mixed at a mass ratio of 96.5:1.5:2. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0279] (3) Preparation of electrolyte

[0280] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Additive b2 was then added and mixed thoroughly.

[0281] (4) Preparation of the separating membrane

[0282] Polyethylene film was selected as the separator.

[0283] (5) Preparation of lithium-ion batteries

[0284] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0285] In Examples 1-14 and Comparative Examples 1-3, b1 and b2 are (I5) ethoxycarbonyl isothiocyanate and (II13) trivinyltrimethylcyclotrisilazane, respectively; in Example 15, b1 and b2 are (I2) and (II3), respectively; and in Example 16, b1 and b2 are (I4) and (II9), respectively.

[0286] The performance of the lithium-ion batteries prepared in the embodiments and comparative examples of the present invention was tested. See Table 1, which shows the performance test data of the lithium-ion batteries prepared in the embodiments and comparative examples of the present invention.

[0287] Table 1

[0288] The contents in Table 1 are mass contents.

[0289] Among them, the test method for the DCR growth rate after 60 days of storage at 60℃ is as follows: The lithium-ion battery was capacitated and charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to the cutoff current of 0.05C, and discharged at 0.33C to 2.5V. This charge-discharge cycle was repeated three times, and the capacity of the third discharge cycle was taken as the battery capacity. The battery was then adjusted to 50% SOC and its DCR was tested: it was discharged at 0.33C to 50% of the capacity of the third capacitated cycle, allowed to stand for 2 hours, then discharged at 1C for 18 seconds at 50% SOC, allowed to stand for 40 seconds, and then charged at 1C for 10 seconds. The voltage during the 18-second discharge and 10-second charge processes was recorded, and the initial DCR1 was calculated.

[0290] Then, the battery was stored at 60℃ for 60 days. After the battery temperature dropped to room temperature, the battery underwent three cycles of capacitance testing under the same conditions. The battery was then charged to 50% SOC and the DCR was tested: It was discharged at 0.33C to 50% of its capacity (the third cycle capacity), allowed to stand for 2 hours, then discharged at 1C for 18 seconds at 50% SOC, allowed to stand for 40 seconds, and then charged at 1C for 10 seconds. The voltage during the 18-second discharge and 10-second charge processes was recorded, and the DCR2 after storage was calculated.

[0291] The battery DCR calculation method is as follows: take the voltage at the last second of rest as V0, the voltage after 18 seconds of discharge as V1, and the current during the discharge process as I, DCR=(V0-V1) / I; Calculate the DCR growth rate = (DCR2 - DCR1) / DCR1 × 100%.

[0292] Test methods for battery high-temperature cycle performance, i.e., high-temperature cycle capacity retention: High-temperature cycle performance tests were conducted on lithium-ion batteries. At a test temperature of 60°C, the lithium-ion batteries were left to stand for 120 minutes, fully charged at 1C constant current and constant voltage with a cutoff voltage of 3.65V and a cutoff current of 0.05C, left to stand for 20 minutes, and then discharged at 1C constant current to 2.5V. This constituted one cycle. The above steps were repeated for a total of 1000 cycles (1000 laps). The discharge capacity of the second lap (Q1) and the discharge capacity of the 1000th lap (Q2) were recorded. The high-temperature cycle capacity retention rate was calculated as Q2 / Q1 × 100%.

[0293] Based on the data in Table 1, and in conjunction with Examples 1-16 and Comparative Examples 1-3, it can be seen that the electrolytes in Examples 1-16 contain VC and additive b, while additive b1 was not added in Comparative Example 1 and additive b2 was not added in Comparative Example 2. From an energy perspective, when electrolyte additive b is not added, the high-temperature cycle performance and the DCR growth rate after 60 days of storage at 60°C are significantly increased.

[0294] Furthermore, as can be seen from Examples 1-5, when the electrolyte addition amount is 0.1-3%; b1 / b2 is 1-15; and the cohesive force and electrolyte additives a and b are in the range of 50-600 of formula m×(a+b), the battery exhibits better high-temperature cycling and a lower DCR growth rate.

[0295] In Examples 9 and 10, when the electrolyte addition amount is greater than 0.3% or less than 0.1%, the high-temperature cycling performance and battery DCR are slightly worse. In Examples 6 and 7, when the ratio of additive b1 to additive b1 in the electrolyte additive does not meet the range of 1-15, the high-temperature cycling performance and battery DCR are slightly worse.

[0296] As shown in Examples 12 and 13, when the cohesive force and additives a and b do not meet the formula range of 50-600, when the formula is lower than 50 or higher than 600, the high-temperature cycle performance and battery DCR of the battery are poor.

[0297] The foregoing has provided a detailed description of a lithium-ion battery and the application of additives in lithium-ion battery electrolytes in reducing the amount of vinylene carbonate used in the electrolyte. Specific examples have been used to illustrate the principles and implementation methods of the invention. The above descriptions of the embodiments are merely to help understand the method and core ideas of the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode and an electrolyte; The positive electrode sheet includes lithium iron phosphate as the positive electrode active material; The electrolyte includes additive a and additive b; The additive a includes vinylene carbonate; The additive b includes compounds with the structure shown in formula (I) and compounds with the structure shown in formula (II); ； In formula (I), M is selected from fluorinated or non-fluorinated C1-C4 alkyl groups; In equation (II), R1, R2, and R3 are each independently selected from H or -C. n H 2n+1 , where n ≤ 4; R4, R5, and R6 are each independently selected from vinyl, allyl, oxyvinyl, or oxyallyl; R7, R8, and R9 are each independently selected from hydrogen, methyl, or ethyl; The cohesive force of the positive electrode sheet, vinylene carbonate, the compound with the structure shown in formula (I), and the compound with the structure shown in formula (II) satisfy the following relationship: 50≤m×(a+b)≤600 (1); Where m is the cohesive force of the positive electrode sheet, in N / m; a is the mass percentage of vinylene carbonate in the electrolyte; and b is the sum of the mass percentages of the compounds with the structure shown in formula (I) and the compounds with the structure shown in formula (II) in the electrolyte. In the electrolyte, the mass content of the compound with the structure shown in formula (I) is 0.1% to 2.5%; In the electrolyte, the mass content of the compound with the structure shown in formula (II) is 0.1% to 0.6%.

2. The lithium-ion battery according to claim 1, characterized in that, The mass ratio of the compound with the structure shown in formula (I) to the compound with the structure shown in formula (II) is (1~15):

1.

3. The lithium-ion battery according to claim 1, characterized in that, Compounds with the structure shown in formula (I) include at least one of the compounds with the structures shown in formulas (I1) to (I17): 。 4. The lithium-ion battery according to claim 1, characterized in that, Compounds with the structure shown in formula (II) include at least one of the compounds with the structures shown in formulas (II1) to (II16): 。 5. The lithium-ion battery according to claim 1, characterized in that, The additive b is specifically ethoxycarbonyl isothiocyanate and trivinyltrimethylcyclotrisilazane.

6. The lithium-ion battery according to claim 1, characterized in that, In the electrolyte, the mass content (a%) of vinylene carbonate is 0.5% to 2.5%.

7. The lithium-ion battery according to claim 1, characterized in that, The total mass ratio of the compound with the structure shown in formula (I) to the compound with the structure shown in formula (II) to the mass of vinylene carbonate is (0.2~2):

1.

8. The lithium-ion battery according to claim 1, characterized in that, In the electrolyte, the mass content of the compound with the structure shown in formula (I) is 0.5% to 2.2%.

9. The lithium-ion battery according to claim 1, characterized in that, In the electrolyte, the mass content of the compound with the structure shown in formula (II) is 0.2% to 0.5%.

10. The lithium-ion battery according to claim 1, characterized in that, The mass content of additive b in the electrolyte is 0.1% to 3%.

11. The lithium-ion battery according to claim 1, characterized in that, The mass content of additive b in the electrolyte is 0.5% to 2.5%.

12. The lithium-ion battery according to claim 1, characterized in that, The cohesive force of the positive electrode sheet satisfies: 20≤m≤200.

13. The lithium-ion battery according to claim 1, characterized in that, The cohesive force of the positive electrode sheet satisfies: 50≤m≤180.

14. The lithium-ion battery according to claim 1, characterized in that, The cohesive force of the positive electrode sheet satisfies: 70≤m≤150.

15. The lithium-ion battery according to claim 1, characterized in that, The mass percentage of the vinylene carbonate in the electrolyte, the mass percentage of the compound with the structure shown in formula (I) and the mass percentage of the compound with the structure shown in formula (II) in the electrolyte satisfy the following condition: 0.1≤a+b≤5.

16. The lithium-ion battery according to claim 1, characterized in that, When the cohesive force m of the positive electrode sheet is less than or equal to 60, b / a is greater than or equal to 1.

5.

17. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery also includes a negative electrode; The negative electrode includes a negative electrode active material; The negative electrode active material includes graphite and / or silicon-based materials.

18. The application of compounds with the structure shown in formula (I) and compounds with the structure shown in formula (II) as additives in lithium-ion battery electrolytes in reducing the amount of vinylene carbonate used in the electrolyte; ； in, In formula (I), M is selected from fluorinated or non-fluorinated C1-C4 alkyl groups; In equation (II), R1, R2, and R3 are each independently selected from H or -C. n H 2n+1 , where n ≤ 4; R4, R5, and R6 are each independently selected from vinyl, allyl, oxyvinyl, or oxyallyl; R7, R8, and R9 are each independently selected from hydrogen, methyl, or ethyl; The lithium-ion battery is a lithium iron phosphate lithium-ion battery. In the electrolyte, the mass content of the compound with the structure shown in formula (I) is 0.1% to 2.5%; In the electrolyte, the mass content of the compound with the structure shown in formula (II) is 0.1% to 0.6%.

19. The application according to claim 18, characterized in that, The applications include the use of compounds with the structure shown in formula (I) in improving the high-temperature performance and / or storage performance of lithium-ion batteries; The applications include the use of compounds with the structure shown in formula (II) in improving the high-temperature performance and / or storage performance of lithium-ion batteries.

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