Electrolyte additive and nonaqueous electrolyte and lithium ion battery containing the same

Abstract

The application discloses an electrolyte additive, a nonaqueous electrolyte containing the additive and a lithium ion battery. The application provides a lithium ion electrolyte additive shown in formula (I) for constructing a good interface film between a positive electrode and an electrolyte, ensuring the stability of a high-nickel positive electrode material in a lithium ion battery cycle process, and keeping the impedance of the battery at a low level, thereby improving the power and cycle performance of the high-nickel positive electrode lithium ion battery. Further, when the electrolyte additive shown in formula (I) and tetraethenylsilane and / or propenyl-1,3-sulfonic acid lactone are simultaneously added, the two components play a synergistic role, further reducing the initial internal resistance of the high-nickel positive electrode lithium battery and improving the cycle performance.

Description

Technical Field

[0001] This article relates to lithium-ion battery technology, and more particularly to an electrolyte additive and its preparation method, a non-aqueous electrolyte containing the electrolyte additive and its preparation method, and lithium-ion batteries. Background Technology

[0002] With the continued growth in sales of new energy vehicles, higher demands are being placed on the energy density and lifespan of lithium-ion batteries. Therefore, developing lithium-ion batteries with long cycle life and high specific energy has become a development trend. Ternary cathode materials, due to their high voltage and high specific capacity, have become the preferred material for high-energy-density batteries. However, during cycling, they are prone to side reactions with the electrolyte, leading to capacity decay, shortened lifespan, and even safety issues in lithium-ion batteries.

[0003] The current problem of rapid cycle degradation in high-nickel cathode materials is mainly caused by the instability of the cathode-electrolyte interface. To address this issue, on the one hand, the cathode material can be modified, such as through doping or coating, but this process is complex and leads to a significant increase in cost. On the other hand, the electrolyte composition can be optimized, such as by adding 1,3-propanesulfonate lactone (PS) or tripropenyl phosphate (TPP), but these additives often result in greater battery impedance and cannot balance the battery's power performance and cycle performance. Summary of the Invention

[0004] This application proposes a lithium-ion electrolyte additive with the structure shown in Formula (I) to construct a high-performance interfacial film between the cathode and the electrolyte, ensuring the stability of the high-nickel cathode material during lithium-ion battery cycling, while also maintaining a low battery impedance, thereby improving the power and cycle performance of the high-nickel cathode lithium-ion battery. Furthermore, adding the electrolyte additive shown in Formula (I) simultaneously with tetravinylsilane (TVSI) and / or propylene-1,3-sulfonyl lactone (PST) can ensure both a low internal resistance level and good high-temperature performance in the lithium-ion battery.

[0005] In a first aspect, embodiments of this application provide an electrolyte additive having the structure shown in formula (I): ; In formula (I), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups.

[0006] Secondly, embodiments of this application also provide a method for preparing the above-mentioned electrolyte additive, wherein the reaction route of the preparation method includes: ; In formulas (I) and (II), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups; The preparation method includes the following steps: In an organic solvent, the compound shown in formula (II) is reacted with a sulfonating agent to produce the electrolyte additive shown in formula (I).

[0007] Thirdly, embodiments of this application provide a non-aqueous electrolyte for lithium-ion batteries, the non-aqueous electrolyte comprising lithium salt, organic solvent, additive A and additive B; Wherein, additive A is one or a combination of two of tetravinylsilane (TVSI) and propylene-1,3-sulfonyl lactone (PST); and additive B is the electrolyte additive described in the first aspect.

[0008] Fourthly, embodiments of this application provide a method for preparing a non-aqueous electrolyte for lithium-ion batteries, which includes the following steps: In an inert gas atmosphere, lithium salt, additive A, and additive B are dissolved in an organic solvent to obtain the non-aqueous electrolyte.

[0009] Fifthly, embodiments of this application provide a high-nickel ternary cathode system lithium-ion battery, which includes a cathode, a cathode, a separator, and the non-aqueous electrolyte described in the third aspect or the non-aqueous electrolyte prepared by the preparation method described in the fourth aspect.

[0010] The technical solution of this application embodiment has the following beneficial effects compared with the prior art: Compared with commonly used electrolyte additives for protecting the positive electrode, the electrolyte additive shown in formula (I) provided in this application ensures good cycle performance of high-nickel positive electrode lithium-ion batteries and has a lower initial internal resistance than commonly used additives.

[0011] In the embodiments of this application, when the electrolyte additive shown in formula (I) is used simultaneously with tetravinylsilane (TVSI) and / or propylene-1,3-sulfonyl lactone (PST), the lithium-ion battery exhibits lower internal resistance, better rate performance, and better cycle performance under high temperature conditions.

[0012] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application may be realized and obtained by means of the methods described in the description. Detailed Implementation

[0013] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0014] In a first aspect, embodiments of this application provide an electrolyte additive having the structure shown in formula (I): ; In formula (I), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups.

[0015] The Si-O groups in the electrolyte additive shown in formula (I) of this application can enhance the strength and stability of the interfacial film by forming a polymer-derived passivation layer with [-O-Si-O-] as the structural unit. Simultaneously, the Si-O groups can capture acidic substances such as HF, reducing the damage to the interfacial film caused by harmful substances. Furthermore, the N in pyridine has a lone pair of electrons, which can coordinate with water, greatly mitigating the decomposition of LiPF6. Moreover, during the first charging process in the lithium-ion battery formation step, due to the presence of unsaturated bonds in the additive structure, its LUMO energy level is lower than that of the solvent, allowing it to preferentially undergo reduction decomposition on the negative electrode side compared to the solvent. The N, S, and other elements contained therein can react with Li... + The reaction results in an interfacial film containing more inorganic components, such as Li2SO3, which can improve the permeability of lithium ions and reduce the internal resistance of high-nickel lithium-ion batteries.

[0016] In one exemplary embodiment, the C1-C3 alkyl group includes methyl, ethyl, n-propyl, and isopropyl.

[0017] In one exemplary embodiment, the electrolyte additive shown in formula (I) has the following structure: .

[0018] Secondly, embodiments of this application also provide a method for preparing the electrolyte additive described in the first aspect, the reaction route of which is as follows: ; In formulas (I) and (II), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups. Optionally, the C1-C3 alkyl groups include methyl, ethyl, n-propyl, and isopropyl. The preparation method includes the following steps: In an organic solvent, the compound shown in formula (II) is reacted with a sulfonating agent to produce the electrolyte additive shown in formula (I).

[0019] In one exemplary embodiment, the organic reagent is dichloromethane.

[0020] In one exemplary embodiment, the sulfonating agent is selected from any one or more of fuming sulfuric acid, chlorosulfonic acid, etc., and may be selected as fuming sulfuric acid.

[0021] In one exemplary embodiment, when the sulfonating agent is fuming sulfuric acid, the molar ratio of the compound represented by formula (II) to fuming sulfuric acid based on SO3 is 1: (2.2 to 6.0), optionally 1: (2.5 to 4.0), for example 1:3.

[0022] In one exemplary embodiment, the reaction temperature is from 0°C to 100°C, optionally from 40°C to 80°C, such as, but not limited to, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and 80°C.

[0023] In one exemplary embodiment, the reaction time is 4 h to 10 h, optionally 6 h to 8 h, such as, but not limited to, 6 h, 6.5 h, 7.0 h, 7.5 h, 8.0 h.

[0024] Thirdly, embodiments of this application provide a non-aqueous electrolyte for lithium-ion batteries, the non-aqueous electrolyte comprising lithium salt, organic solvent, additive A and additive B; Wherein, additive A is one or a combination of two of tetravinylsilane (TVSI) and propylene-1,3-sulfonyl lactone (PST); and additive B is the electrolyte additive described in the first aspect.

[0025] Additives A and B play a synergistic role in the formation of the interfacial film. During the formation and charging process, additives A and B preferentially undergo oxidation reactions on the positive electrode side, thereby forming a stable and dense positive electrode electrolyte interfacial film on the positive electrode surface, further improving the protection of the positive electrode side, and taking into account both low internal resistance and high temperature performance.

[0026] In one exemplary embodiment, the additive B has the following structure: .

[0027] In one exemplary embodiment, based on the total mass of the non-aqueous electrolyte (100%), the mass percentage of additive B in the non-aqueous electrolyte is 0.1% to 5.0%, for example, but not limited to, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8%, and 5.0%. In another exemplary embodiment, the mass percentage of additive B in the non-aqueous electrolyte is 1% to 3%.

[0028] In one exemplary embodiment, additive A is tetravinylsilane (TVSI). In another exemplary embodiment, additive A is propylene-1,3-sulfonyl lactone (PST). In yet another exemplary embodiment, additive A is a combination of tetravinylsilane (TVSI) and propylene-1,3-sulfonyl lactone (PST) in a mass ratio of 1:(0.1 to 10), optionally 1:(1 to 3), which ensures good high-temperature performance while maintaining low cost. Ratios below this range result in poor high-temperature performance, while ratios above this range lead to increased costs without significant improvement in performance.

[0029] In one exemplary embodiment, based on the total mass of the non-aqueous electrolyte (100%), the mass percentage of additive A in the non-aqueous electrolyte is 0.1% to 5.0%, for example, but not limited to, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8%, and 5.0%. In another exemplary embodiment, the mass percentage of additive A in the non-aqueous electrolyte is 0.5% to 3%.

[0030] In one exemplary embodiment, the mass ratio of additive A to additive B is 1:(0.4 to 3), for example, but not limited to, 1:(0.5 to 1). Within this range, the inorganic component content of the interfacial component in the formation stage is higher, resulting in better lithium-ion permeability and better performance in forming the interfacial film.

[0031] In one exemplary embodiment, the lithium salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0032] In one exemplary embodiment, the mass percentage of the lithium salt in the non-aqueous electrolyte is 5% to 20%, based on the total mass of the non-aqueous electrolyte being 100%, for example, but not limited to 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0033] In one exemplary embodiment, the organic solvent includes at least one of cyclic carbonates and linear esters. In another exemplary embodiment, the cyclic carbonate includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC); the linear ester includes, but is not limited to, at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl acetate (EA), ethyl propionate (EP), and propionic acid propionate (PP).

[0034] In one exemplary embodiment, with the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the organic solvent in the non-aqueous electrolyte is 74% to 94%, such as, but not limited to, 74%, 75%, 76%, 78%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, and 94%.

[0035] Fourthly, embodiments of this application provide a method for preparing a non-aqueous electrolyte for lithium-ion batteries, which includes the following steps: In an inert gas atmosphere, lithium salt, additive A, and additive B are dissolved in an organic solvent to obtain the non-aqueous electrolyte.

[0036] The inert gas atmosphere can be argon.

[0037] Fifthly, embodiments of this application provide a high-nickel ternary cathode system lithium-ion battery, which includes a cathode, a cathode, a separator, and the non-aqueous electrolyte described in the third aspect or the non-aqueous electrolyte prepared by the preparation method described in the fourth aspect.

[0038] In one exemplary embodiment, the active material of the positive electrode includes a high-nickel positive electrode active material. In another exemplary embodiment, the high-nickel positive electrode material may be represented as LiNi. x Co y Mn z O2 (x+y+z=1.0, where x≥0.6, 0<y<0.4 and 0<z<0.4), for example, but not limited to LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2.

[0039] In one exemplary embodiment, the active material of the negative electrode is selected from graphite negative electrodes and silicon-containing negative electrodes. In one exemplary embodiment, the graphite negative electrode includes, but is not limited to, at least one of artificial graphite, hard carbon, natural graphite, and mesophase microspheres. In one exemplary embodiment, the silicon-containing negative electrode includes, but is not limited to, at least one of nano-silicon negative electrodes, silicon-oxygen negative electrodes, and silicon-carbon negative electrodes.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0041] Example 1 Preparation of Additive B-1 The reaction route for preparing additive B-1 is as follows: ; Preparation methods include: To a reactor containing 0.1 mol of the compound represented by Formula II-1 (CAS: 108094-04-8, purchased from Sigma-Aldrich), 200 mL of inert solvent dichloromethane was added. Fuming sulfuric acid, a sulfonating agent, was added dropwise with stirring. The molar ratio of the compound represented by Formula II-1 to fuming sulfuric acid (calculated as SO3) was 1:3. The reaction temperature was controlled at 50 °C, and the reaction time was 7 h, to selectively sulfonate the pyridine ring in the structure. After the reaction was completed, the mixture was quenched with water, separated, and the organic phase was dried and concentrated to obtain additive B-1. 1 H NMR (400 MHz, DMSO-d6): δ 8.92 (d, J = 2.0 Hz, 2H), 8.76 (d, J = 2.0 Hz, 2H), 8.31 (dd, J = 2.0, 2.0 Hz, 2H), 0.35 (s, 12H). Example 2: Preparation of lithium-ion batteries using non-aqueous electrolytes and high-nickel ternary cathode systems. This embodiment provides a non-aqueous electrolyte for lithium-ion batteries, which, based on 100% of the total mass of the non-aqueous electrolyte for lithium-ion batteries, contains the following components: 13% lithium hexafluorophosphate (LiPF6), 3% additive A (in which the mass ratio of tetravinylsilane (TVSI) and propylene-1,3-sulfonyl lactone (PST) is 1:1), 2.0% additive B-1, and the balance being an organic solvent (the mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) is EC:EMC:DEC = 2:3:5).

[0042] Non-aqueous electrolytes for lithium-ion batteries are prepared by the following method: In an argon-filled glove box, organic solvents are mixed and lithium hexafluorophosphate (LiPF6) is slowly added. After the LiPF6 is completely dissolved, additives A and B are added and stirred until completely dissolved to obtain the non-aqueous electrolyte for lithium-ion batteries.

[0043] This embodiment also provides a lithium-ion battery based on a high-nickel ternary cathode system with a non-aqueous electrolyte, the preparation method of which includes: (1) Mix LiNi in a weight ratio of 97:1.5:1.5 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black Super P, and binder polyvinylidene fluoride (PVDF) are mixed and dispersed in N-methyl-2-pyrrolidone (NMP) to form a positive electrode slurry. After the positive electrode slurry is coated on both sides of an aluminum foil, it is then baked, rolled, and cut to obtain a positive electrode sheet. Artificial graphite, conductive carbon black Super P, and binder SBR were mixed in a weight ratio of 92:4:4 and dispersed in deionized water to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil and then baked, rolled, and cut to obtain a negative electrode sheet. A 15 μm thick PP material separator was prepared. (2) The positive electrode, negative electrode and separator prepared in step (1) are wound to obtain a bare cell; (3) The bare cell is placed into an aluminum-plastic packaging film, and the above electrolyte is injected and sealed to obtain a lithium-ion battery.

[0044] Example 3 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0045] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that the proportion of additive B-1 in the non-aqueous electrolyte for lithium-ion batteries is 0.1%.

[0046] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0047] Example 4 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0048] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that the proportion of additive B-1 in the non-aqueous electrolyte for lithium-ion batteries is 5.0%.

[0049] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0050] Example 5 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0051] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that additive A in the non-aqueous electrolyte for lithium-ion batteries is replaced with 3% propylene-1,3-sulfonyl lactone (PST).

[0052] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0053] Example 6 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0054] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that additive A in the non-aqueous electrolyte for lithium-ion batteries is replaced with 3% tetravinylsilane (TVSI).

[0055] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0056] Example 7 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0057] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that the amount of additive A in the non-aqueous electrolyte for lithium-ion batteries is 0.1%.

[0058] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0059] Example 8 This embodiment provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0060] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that the amount of additive A in the non-aqueous electrolyte for lithium-ion batteries is 5%.

[0061] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0062] Comparative Example 1 This comparative example provides a non-aqueous electrolyte for lithium-ion batteries, which differs from Example 2 in that the additive is replaced with 1% vinylene carbonate.

[0063] This comparative example also provides a high-nickel ternary cathode system lithium-ion battery based on a non-aqueous electrolyte, which differs from the lithium-ion battery in Example 2 in that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this comparative example.

[0064] Comparative Example 2 This comparative example provides a lithium-ion battery electrolyte, referring to Example 3 in CN120357030A.

[0065] The lithium-ion battery electrolyte comprises a non-aqueous organic solvent, a lithium salt, and additives, wherein the additives include film-forming additives and organic compounds as shown in the following structural formula: In this configuration, based on the mass of the lithium-ion battery electrolyte, the organic compound accounts for 3.5% of the total mass; the film-forming additive is fluoroethylene carbonate, and based on the mass of the lithium-ion battery electrolyte, the film-forming additive accounts for 1.5% of the total mass; the mass ratio of the organic compound as shown in Structural Formula I to the film-forming additive is 3.5:1.5; the non-aqueous organic solvent is a combination of ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and dimethyl carbonate, with a mass ratio of ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and dimethyl carbonate of 30:5:35:20, and based on the mass of the lithium-ion battery electrolyte, the non-aqueous organic solvent accounts for 80% of the total mass; and the lithium salt is lithium bis(oxalato)borate, and based on the mass of the lithium-ion battery electrolyte, the lithium salt accounts for 15% of the total mass.

[0066] The preparation method of the above-mentioned lithium-ion battery electrolyte includes the following steps: (1) In a glove box filled with argon, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate and dimethyl carbonate are mixed in a mass ratio of 30:5:35:20 to obtain a non-aqueous organic solvent.

[0067] (2) At 30°C, lithium bis(oxalato)borate is added to the non-aqueous organic solvent, followed by the addition of fluoroethylene carbonate and an organic compound as shown in structural formula I. After stirring evenly, a lithium-ion battery electrolyte is obtained. In the lithium-ion battery electrolyte, the mass percentage of lithium bis(oxalato)borate is 15%, the mass percentage of fluoroethylene carbonate is 1.5%, and the mass percentage of the organic compound is 3.5%.

[0068] This comparative example also provides a high-nickel ternary cathode system lithium-ion battery based on a non-aqueous electrolyte, which differs from the lithium-ion battery in Example 2 in that the non-aqueous electrolyte is replaced with the electrolyte of this comparative example.

[0069] Comparative Example 3 This comparative example provides a lithium-ion battery electrolyte, referring to Example 1 in CN101673852A.

[0070] The lithium-ion battery electrolyte was prepared by the following method: 60 g of vinyl carbonate (EC), 30 g of methyl ethyl carbonate (EMC) and 60 g of diethyl carbonate (DMC) were mixed into a mixed solvent; 19.54 g of LiPF6 electrolyte was added to the mixed solvent, the concentration of LiPF6 in the electrolyte was 1M, and then 2.54 g (1.5 wt%) of film-forming additive vinylene carbonate (VC) and 8.6 g (5%) of flame retardant additive 3,5-dichloropyridine were added to the mixture, and the mixture was stirred until all solids were completely dissolved to obtain the organic electrolyte. This comparative example also provides a high-nickel ternary cathode system lithium-ion battery based on a non-aqueous electrolyte, which differs from the lithium-ion battery in Example 2 in that the non-aqueous electrolyte is replaced with the electrolyte of this comparative example.

[0071] Comparative Example 4 This comparative example provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0072] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that only 5% of additive A (in which the mass ratio of TVSI and PST is 1:1) is added to the non-aqueous electrolyte for lithium-ion batteries, while additive B is not added.

[0073] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this comparative example.

[0074] Comparative Example 5 This comparative example provides a non-aqueous electrolyte for lithium-ion batteries and a high-nickel ternary cathode system based on the non-aqueous electrolyte for lithium-ion batteries.

[0075] The difference between the non-aqueous electrolyte for lithium-ion batteries and Example 2 is that only 5% of additive B is added to the non-aqueous electrolyte for lithium-ion batteries, while additive A is not added.

[0076] The difference between the lithium-ion battery and the lithium-ion battery in Example 2 is that the non-aqueous electrolyte is replaced with the non-aqueous electrolyte of this example.

[0077] Performance testing: The high-nickel ternary cathode lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to performance tests, including initial internal resistance (DCR) testing and high-temperature cycle performance testing. The specific test methods are as follows: Initial internal resistance (DCR) test: Under an environment of 25±2 ℃, after the battery is adjusted to a specified 50% SOC (state of charge), it is left to stand for 2 hours. A 4C current (I) is applied to the battery and discharged continuously for 30 s. The initial voltage (U0) and the termination voltage (U1) before and after the current application are recorded, and ΔU is calculated. The internal resistance is calculated according to Ohm's law: DCR = (U0-U1) / I.

[0078] High-temperature cycle performance test: At 45±2 ℃, the lithium-ion battery was subjected to charge-discharge cycle tests at a charge / discharge rate of 1C / 1C within the range of 2.75V to 4.25V, and the discharge capacity of the battery in the first cycle and the discharge capacity after 500 cycles were recorded. The capacity retention rate after 500 cycles = discharge capacity after 500 cycles / discharge capacity in the first cycle × 100%.

[0079] The test results are shown in Table 1.

[0080] Table 1. As can be seen from the data presented above, compared with the embodiments of this application and Comparative Examples 1-3, the interfacial film formed by the additive combination in the embodiments of this application has a lower internal resistance, indicating that the interfacial film contains more inorganic components, resulting in better lithium-ion permeability. Comparing Example 2 with Comparative Examples 4 and 5, it can be seen that when additives A and B are used together, they exert a synergistic effect, ensuring both low internal resistance and good high-temperature cycling performance in the high-nickel ternary cathode lithium battery system. Comparative Examples 2, 5, and 6 show that the simultaneous use of tetravinylsilane and propylene-1,3-sulfonyl lactone in additive A, along with the synergistic use of additive B, can further ensure both low impedance and good high-temperature performance in the high-nickel lithium-ion battery.

[0081] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An electrolyte additive, characterized in that, The electrolyte additive has the structure shown in formula (I): ； In formula (I), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups.

2. The electrolyte additive according to claim 1, characterized in that, The C1-C3 alkyl groups include methyl, ethyl, n-propyl, and isopropyl.

3. The electrolyte additive according to claim 1, characterized in that, The electrolyte additive shown in formula (I) has the following structure: 。 4. The method for preparing the electrolyte additive according to any one of claims 1 to 3, characterized in that, The reaction route of the preparation method includes: ； In formulas (I) and (II), R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl groups; The preparation method includes the following steps: In an organic solvent, the compound shown in formula (II) is reacted with a sulfonating agent to generate the electrolyte additive shown in formula (I); Optionally, the organic reagent is dichloromethane; and / or The sulfonating agent is selected from any one or more of fuming sulfuric acid and chlorosulfonic acid, and may be selected from fuming sulfuric acid; when the sulfonating agent is fuming sulfuric acid, the molar ratio of the compound shown in formula (II) to fuming sulfuric acid based on SO3 is 1:(2.2 to 6.0), and may be selected from 1:(2.5 to 4.0); and / or The reaction temperature is from 0 °C to 100 °C, optionally from 40 °C to 80 °C; and / or The reaction time is 4 h to 10 h, and can be selected as 6 h to 8 h.

5. A non-aqueous electrolyte for lithium-ion batteries, characterized in that, The non-aqueous electrolyte includes lithium salt, organic solvent, additive A, and additive B; Wherein, additive A is one or a combination of two of tetravinylsilane and propenyl-1,3-sulfonyl lactone; and additive B is the electrolyte additive according to any one of claims 1 to 3.

6. The non-aqueous electrolyte according to claim 5, characterized in that, The additive B has the following structure: ; and / or Based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of additive B in the non-aqueous electrolyte is 0.1% to 5.0%, and can be selected as 1% to 3%.

7. The non-aqueous electrolyte according to claim 5, characterized in that, Additive A is tetravinylsilane; or Additive A is propylene-1,3-sulfonyl lactone; or Additive A is a combination of tetravinylsilane and propenyl-1,3-sulfonyl lactone in a mass ratio of 1:(0.1 to 10), optionally 1:(1 to 3); and / or Based on the total mass of the non-aqueous electrolyte (100%), the mass percentage of additive A in the non-aqueous electrolyte is 0.1% to 5.0%, optionally 0.5% to 3%; and / or The mass ratio of additive A to additive B is 1:(0.4 to 3), optionally 1:(0.5 to 1); and / or The lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis(trifluoromethyl)imide, and lithium bis(fluorosulfonyl)imide; and / or Based on the total mass of the non-aqueous electrolyte (100%), the lithium salt content in the non-aqueous electrolyte is 5% to 20% by mass; and / or The organic solvent comprises at least one of cyclic carbonates and linear esters; wherein the cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and the linear ester comprises at least one of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, and propionic acid; and / or Based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the organic solvent in the non-aqueous electrolyte is 74% to 94%.

8. The method for preparing the non-aqueous electrolyte according to any one of claims 5 to 7, characterized in that, Includes the following steps: In an inert gas atmosphere, lithium salt, additive A, and additive B are dissolved in an organic solvent to obtain the non-aqueous electrolyte.

9. A high-nickel ternary cathode system lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte as described in any one of claims 5 to 7 or a non-aqueous electrolyte prepared by the preparation method described in claim 8.

10. The lithium-ion battery according to claim 9, characterized in that, The active material of the positive electrode includes a high-nickel positive electrode active material; optionally, the high-nickel positive electrode material is represented as LiNi. x Co y Mn z O2, where x + y + z = 1.0, x ≥ 0.6, 0 < y < 0.4 and 0 < z < 0.4; and / or The active material of the negative electrode is selected from graphite negative electrode and silicon-containing negative electrode; optionally, the graphite negative electrode includes at least one of artificial graphite, hard carbon, natural graphite and mesophase microspheres; the silicon-containing negative electrode includes at least one of nano-silicon negative electrode, silicon-oxygen negative electrode and silicon-carbon negative electrode.

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