Lithium ion battery

Abstract

The invention provides a lithium ion battery, the lithium ion battery comprises an electrolyte and a negative pole piece, the negative pole piece comprises a negative active material, and the negative active material comprises a silicon element; the electrolyte comprises a first additive and a second additive, the structural formula of the first additive is shown as a formula I, and the structural formula of the second additive is shown as a formula II. In the lithium ion battery provided by the invention, the first additive and the second additive can be electrically polymerized and jointly attached to the surfaces of the positive electrode plate and the negative electrode plate during operation of the lithium ion battery adopting the silicon-containing negative electrode plate, so that the stability and the interface smoothness of an electrode interface film can be maintained; and the lithium ion battery has high energy density and also has relatively good fast-charge cycle performance and high-temperature storage performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a lithium-ion battery. Background Technology

[0002] Graphite anodes possess high stability, capable of withstanding tens of thousands of charge-discharge cycles in lithium-ion batteries; however, their relatively low theoretical specific capacity limits their further application in high-energy-density systems. Silicon, on the other hand, boasts extremely high theoretical specific capacity (4200 mAh / g) and low lithium intercalation potential, and can provide Li+ in multiple directions. + While silicon-based lithium-ion batteries have de-intercalation / de-intercalation channels, they also suffer from poor conductivity, easy particle breakage, unstable growth of the solid electrolyte interphase (SEI) film, and volume expansion. These problems ultimately lead to poor fast-charging cycle capability and high-temperature storage performance of silicon-based lithium-ion batteries. Summary of the Invention

[0003] The purpose of this application is to provide a lithium-ion battery that improves both fast-charge cycle performance and high-temperature storage performance while maintaining high energy density. The specific technical solution is as follows:

[0004] This application provides a lithium-ion battery, which includes an electrolyte and a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes silicon.

[0005] The electrolyte includes a first additive and a second additive, the first additive having the structural formula shown in Formula I.

[0006] R1, R2, and R3 are each independently selected from H, F, C1 to C4 alkyl, C1 to C4 fluoroalkyl, C2 to C4 alkenyl, C2 to C4 fluoroalkenyl, C2 to C4 alkynyl, C2 to C4 fluoroalkynyl, C5 to C7 cycloalkyl, unsubstituted or R 01 Substituted phenyl, R 02 Substituted benzyl,

[0007] R 01 R 02 Each is independently selected from F, C1 to C4 alkyl, C2 to C4 alkenyl, C2 to C4 alkynyl, C1 to C4 fluoroalkyl, C2 to C4 fluoroalkenyl, and C2 to C4 fluoroalkynyl;

[0008] The structural formula of the second additive is shown in Formula II.

[0009] R4 is selected from C1 to C6 alkyl, C2 to C6 alkenyl, and C2 to C6 alkynyl;

[0010] R5-R8 are each independently selected from halogens and C1 to C6 alkyl groups;

[0011] M is an alkali metal, selected from Li, Na, or K;

[0012] Y + It is a monovalent cation, selected from , , or .

[0013] In one embodiment, the first additive is selected from at least one of the following compounds: .

[0014] In one embodiment, the second additive is selected from at least one of the following compounds: .

[0015] In one embodiment, the mass ratio of the first additive to the second additive is 1:(0.01 to 5), preferably 1:(0.1 to 2), and more preferably 1:(0.1 to 1).

[0016] In one embodiment, the mass percentage of the first additive is 0.01% to 5%, preferably 0.1% to 2%, based on the total mass of the electrolyte.

[0017] In one embodiment, the second additive has a mass percentage content of 0.01% to 2%, preferably 0.1% to 1%, based on the total mass of the electrolyte.

[0018] In one embodiment, the electrolyte further includes a third additive selected from at least one of vinylene carbonate and fluoroethylene carbonate; the third additive has a mass percentage content of 1% to 23% based on the total mass of the electrolyte.

[0019] In one embodiment, the third additive is vinylene carbonate and fluoroethylene carbonate; based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 0.05% to 3%, and the mass percentage of fluoroethylene carbonate is 2% to 20%.

[0020] In one embodiment, the electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; the lithium salt has a mass percentage content of 6% to 20% based on the total mass of the electrolyte.

[0021] In one embodiment, the lithium salt is lithium hexafluorophosphate and lithium difluorosulfonylimide in a mass ratio of 8:(0.5 to 1.5).

[0022] In one embodiment, the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector; the negative electrode material layer includes the negative electrode active material.

[0023] In one embodiment, the silicon element content is 0.5% to 15% by mass, based on the total mass of the negative electrode material layer.

[0024] In one embodiment, the lithium-ion battery further includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector; the positive electrode material layer includes a positive electrode active material;

[0025] The positive electrode active material is selected from LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, and LiNi. x Co y Mn 1-x- y At least one of O2, wherein 0 < x < 1, 0 < y < 1, 0 < 1 - xy < 1;

[0026] Preferably, the positive electrode active material is LiNi. x Co y Mn 1-x-y O2, 0.3≤x≤0.98.

[0027] This application provides a lithium-ion battery comprising an electrolyte and a negative electrode. The negative electrode comprises a negative electrode active material, which includes silicon. The electrolyte comprises a first additive and a second additive. The first additive has the structural formula shown in Formula I, and the second additive has the structural formula shown in Formula II. In the lithium-ion battery provided by this application, the first and second additives can undergo electropolymerization during operation of the lithium-ion battery using a silicon-containing negative electrode and jointly adhere to the surfaces of the positive and negative electrode sheets. This maintains the stability and smoothness of the electrode interface film, enabling the lithium-ion battery to have both high energy density and good fast-charge cycle performance and high-temperature storage performance. Detailed Implementation

[0028] The technical solutions of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0029] Additives in the electrolyte constitute only a small portion of the electrolyte in a lithium-ion battery, but appropriate amounts of additives can form an SEI film (also referred to as an interface film in this application) on the surface of the negative electrode material layer, reducing the risk of side reactions after direct contact between the negative electrode active material and the electrolyte. Therefore, improving the stability of the SEI film by controlling the additive composition of the electrolyte is crucial for improving the electrochemical performance of silicon-based lithium-ion batteries. Addressing the problems of electrode interface damage during cycling, poor fast-charge cycle performance, and poor high-temperature storage performance in existing silicon-based lithium-ion batteries, this application provides a lithium-ion battery comprising an electrolyte containing a first additive and a second additive, and a silicon-containing negative electrode sheet, enabling the lithium-ion battery to achieve both high energy density and good fast-charge cycle performance and high-temperature storage performance.

[0030] This application provides a lithium-ion battery, which includes an electrolyte and a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes silicon.

[0031] The electrolyte includes a first additive and a second additive, the first additive having the structural formula shown in Formula I.

[0032] R1, R2, and R3 are each independently selected from H, F, C1 to C4 alkyl, C1 to C4 fluoroalkyl, C2 to C4 alkenyl, C2 to C4 fluoroalkenyl, C2 to C4 alkynyl, C2 to C4 fluoroalkynyl, C5 to C7 cycloalkyl, unsubstituted or R 01 Substituted phenyl, R 02 Substituted benzyl,

[0033] R 01 R 02 Each is independently selected from F, C1 to C4 alkyl, C2 to C4 alkenyl, C2 to C4 alkynyl, C1 to C4 fluoroalkyl, C2 to C4 fluoroalkenyl, and C2 to C4 fluoroalkynyl;

[0034] The structural formula of the second additive is shown in Formula II.

[0035] R4 is selected from C1 to C6 alkyl, C2 to C6 alkenyl, and C2 to C6 alkynyl;

[0036] R5-R8 are each independently selected from halogens and C1 to C6 alkyl groups; preferably, R5-R8 are selected from F.

[0037] M is an alkali metal, selected from Li, Na, or K;

[0038] Y + It is a monovalent cation, selected from , , or .

[0039] The inventors discovered that the first additive undergoes electropolymerization during lithium-ion battery operation, resulting in silicon-based deprotection and fluorophosphate decomposition, forming a composite SEI film and positive electrode electrolyte interface film (CEI film) rich in siloxane networks and LiF. The byproduct Li3PO4 formed during the decomposition process can reduce the impact of transition metal dissolution; the byproduct LiF can reduce the impedance of the SEI film; and the byproduct PO3F2... - It possesses the ability to bind transition metal ions, preventing them from diffusing to the negative electrode and damaging the SEI film. The cross-linked siloxane network has a decomposition temperature exceeding 300°C and low solubility, providing a flexible framework for inorganic products such as LiF and Li3PO4, better adapting to the effects of silicon negative electrode expansion. However, the Si-O network structure polymerized solely by the first additive is insufficient to fully form the organic cross-linked framework of the SEI film. Furthermore, PF bonds are easily induced by external factors, such as trace amounts of water in the electrolyte, leading to bond breakage and F removal, causing a sharp increase in electrolyte acidity, which can damage the stability of the positive electrode active material, accelerate the dissolution of transition metal ions, and also accelerate the dissolution of the SEI film, hindering the application of high-content first additives. The second additive has a lower least unoccupied molecular orbital (LUMO) energy level and preferentially decomposes during lithium-ion battery operation, forming an interface film rich in Li2SO4, Li3PO4, Li2CO3, and LiF. This can reduce the interface film impedance and allow for the formation of more Li... +Vacancies and the space charge layer formed between interface defects can further improve the conductivity of the interface film, thereby establishing excellent SEI and CEI films for lithium-ion batteries. Simultaneously, the second additive contains the electronegative group -CN, which can coordinate with transition metals, inhibiting transition metal dissolution and tunneling. The lone pair electrons of the -CN component can act as sacrificial agents for HF (generated by the reaction of electrolyte components with trace amounts of water, or by the decomposition of electrolyte components) and H2O (trace amounts of water in lithium-ion batteries, at the ppm level), forming stable F(O)·HN hydrogen bonds with HF, or with HF and H2O. This helps ensure the stable operation of the positive electrode active material, which is sensitive to HF and H2O, during cycling, further guaranteeing the operational stability of the lithium-ion battery. The second additive, sulfonic acid containing unsaturated groups, also undergoes polymerization. Compared to the polymerization of carbonates, it exhibits higher stability and provides high-performance inorganic components for both SEI and CEI films. It can adapt to volume changes during lithium-ion battery operation, enabling the lithium-ion battery to possess both high strength and suitable elasticity. It can synergistically work with the Si-O network structure of the first additive to ensure the stable operation of lithium-ion batteries with silicon-containing anodes. Furthermore, the second additive has low solubility, less than 2 wt% in electrolyte. Using only the second additive is insufficient to ensure the integrity of the positive and negative electrode films; therefore, the first and second additives are used in combination. Silicon possesses extremely high theoretical specific capacity and low lithium intercalation potential, and can provide Li+ in multiple directions. + Insertion / deintercalation channels. Using the electrolyte comprising the first and second additives of this application, combined with silicon-containing negative electrode sheets, can not only improve the capacity of lithium-ion batteries but also alleviate problems such as unstable SEI film growth and volume expansion caused by silicon. The combined use of the two additives allows for electropolymerization during lithium-ion battery operation, enabling them to adhere together to the surfaces of the positive and negative electrode sheets, maintaining the stability and smoothness of the electrode interface film, promoting stable cycling of silicon-based lithium-ion batteries, and thus enabling lithium-ion batteries to have both high energy density and good fast-charge cycle performance and high-temperature storage performance.

[0040] In one embodiment, the first additive is selected from at least one of the following compounds: compound I-1 (CAS No.: 2708941-25-5), Compound I-2 (CAS No.: 4419-25-9), Compound I-3 (CAS No.: 13683-39-1), Compound I-4 (CAS No.: 4414-27-1), Compound I-5 (CAS No.: 4414-26-0), Compound I-6 (CAS No.: 4480-02-8), Compound I-7 (CAS No.: 2577172-95-1), Compound I-8 (CAS No.: 13683-40-4), Compound I-9 (CAS No.: 2577172-93-9), Compound I-10 (CAS No.: 2708941-27-7), Compound I-11 (CAS No.: 2287283-36-5), Compound I-12 (CAS No.: 6231-57-8), Compound I-13 (CAS No.: 1386-54-9), Compound I-14 (CAS No.: 2708941-26-6), Compound I-15 (CAS No.: 6231-58-9), Compound I-16 (CAS No.: 6231-59-0), Compound I-17 (CAS No.: 2577172-94-0), Compound I-18 Compound I-19 Compound I-20 Compound I-21 Compound I-22 The use of the first additive described above can effectively enhance its synergistic effect with the second additive, resulting in lithium-ion batteries with higher energy density, better fast-charge cycle performance, and better high-temperature storage performance.

[0041] In this application, compounds I-18 to I-22 can be prepared according to the following synthetic method: Under anhydrous conditions, sodium difluorophosphate is added to a reaction vessel, followed by ultra-dry acetonitrile solvent. The solid is stirred and dissolved at a controlled temperature of 20°C to 60°C. Then, chlorosilane is slowly added, maintaining a nitrogen atmosphere during the addition of chlorosilane and stirring continuously at 20°C to 60°C for 6 to 10 hours. After the reaction is complete, the mixture is allowed to stand at room temperature for 1 to 3 hours, then filtered to remove the solid precipitate. Nitrogen gas is then used to bubble the solvent and volatile byproducts to obtain the desired silane-based fluorophosphate product. The molar ratio of sodium difluorophosphate to chlorosilane is 1:(0.5 to 2). "Room temperature" refers to 25°C ± 5°C. Compound I-18 The raw material for the chlorosilane is trivinylchlorosilane (1871-21-2), compound I-19. The chlorosilane raw material is dimethylynyl butyl chlorosilane (2069196-19-4), compound I-20 The chlorosilane raw material is dimethyl(trifluoropropenyl)chlorosilane (89705-02-2), compound I-21 The chlorosilane raw material is tris(pentafluoroethyl)chlorosilane (1620665-21-5), compound I-22 The raw material for the chlorosilane is dimethyl (p-methylbenzyl)chlorosilane (1833-28-9).

[0042] In one embodiment, the first additive is selected from at least one of the following compounds: .

[0043] Using the first type of additive described above can better leverage its synergistic effect with the second additive, resulting in better fast-charge cycle performance and better high-temperature storage performance for lithium-ion batteries.

[0044] In one embodiment, the second additive is selected from at least one of the following compounds: .

[0045] Using the above-mentioned type of second additive can better exert the synergistic effect with the first additive, enabling lithium-ion batteries to have higher energy density, better fast-charge cycle performance and high-temperature storage performance.

[0046] In one embodiment, the mass ratio of the first additive to the second additive is 1:(0.01 to 5), preferably 1:(0.1 to 2), and more preferably 1:(0.1 to 1). For example, the mass ratio of the first additive to the second additive can be 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.4, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or a range of any two of these values. When the mass ratio of the first additive to the second additive is less than 1:5, the content of the second additive is too high compared to the first additive. This makes it difficult for the electrolyte to dissociate a large amount of the second additive, increasing the risk of electrolyte turbidity and lithium salt deposition. It also easily leads to uneven distribution of lithium salt concentration gradients, significant polarization, and excessively thick film formation with a large initial DCR, which is detrimental to improving the fast-charge cycle performance of lithium-ion batteries. When the mass ratio of the first additive to the second additive is greater than 1:0.01, the interfacial film formation is insufficient, and the synergistic effect of the first and second additives is difficult to fully exert, thus affecting the fast-charge cycle performance and high-temperature storage performance of lithium-ion batteries. The increase is not significant; by adjusting the mass ratio of the first additive and the second additive within the above range, the inorganic and organic components cross-link to form a film, which is beneficial to improving the stability of the lithium-ion battery interface film. This gives the interface film good toughness and a certain strength, which can resist the expansion of the silicon anode. It also enables the electrolyte and the positive and negative electrode interfaces to have good ionic conductivity, which is beneficial to the desolvation of lithium ions. At the same time, the moderate thickness of the interface film can reduce the lithium ion conduction path, which is beneficial to the fast charging performance. It also helps to improve the flatness of the positive and negative electrode surfaces, promotes the cycle stability of the lithium-ion battery, and thus enables the lithium-ion battery to have high energy density while having good fast charging cycle performance and high temperature storage performance.

[0047] In one embodiment, based on the total mass of the electrolyte, the mass percentage content of the first additive is 0.01% to 5%, preferably 0.1% to 2%. For example, the mass percentage content of the first additive can be 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range of any two of these values. Controlling the mass percentage content of the first additive within the above range allows for better synergy with the second additive, improving the flatness of the positive and negative electrode surfaces of the lithium-ion battery and reducing the risk of SEI film rupture due to excessively high internal inorganic salt content. This, in turn, enhances the fast-charge cycle performance and high-temperature storage performance of the lithium-ion battery.

[0048] In one embodiment, based on the total mass of the electrolyte, the mass percentage content of the second additive is 0.01% to 2%, preferably 0.1% to 1%. For example, the mass percentage content of the second additive can be 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or a range of any two of these values. Regulating the mass percentage content of the second additive within the above range allows for better synergy with the first additive, fully forming the organic cross-linked framework of the SEI film. Simultaneously, it reduces the probability of vertical adsorption on the surface of the negative electrode, improving the stability of the negative electrode surface structure and enhancing the flatness of the positive and negative electrode surfaces. This, in turn, improves the fast-charge cycle performance and high-temperature storage performance of the lithium-ion battery.

[0049] In one embodiment, the electrolyte further includes a third additive selected from at least one of vinylene carbonate and fluoroethylene carbonate; the mass percentage of the third additive is 1% to 23% based on the total mass of the electrolyte. For example, the mass percentage of the third additive can be 1%, 2%, 3%, 5%, 6%, 8%, 10%, 12%, 13%, 15%, 16%, 18%, 20%, 21%, 22%, 23%, or a range of any two of these values. Using the above-mentioned third additive and controlling its mass percentage within the above range allows for better dissociation of lithium salts and stronger binding ability with Li ions. It can participate in the first solvation sheath layer, forming a film earlier due to its strong reducing activity, reducing side reactions, and further enhancing the film-forming stability of the SEI film. Simultaneously, it provides more and more uniform inorganic sites for the first and second additives, resulting in a more uniform overall interfacial film. This leads to lithium-ion batteries having high energy density while also exhibiting better fast-charge cycle performance and high-temperature storage performance.

[0050] In one embodiment, the third additive is vinylene carbonate and fluoroethylene carbonate; based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 0.05% to 3%, and the mass percentage of fluoroethylene carbonate is 2% to 20%. For example, the mass percentage of vinylene carbonate can be 0.05%, 0.1%, 0.2%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or a range of any two of these values. The mass percentage of fluoroethylene carbonate can be 2%, 3%, 5%, 6%, 8%, 10%, 12%, 13%, 15%, 16%, 18%, 20%, or a range of any two of these values. Using this third additive enables lithium-ion batteries to have high energy density while also exhibiting better fast-charge cycle performance and high-temperature storage performance.

[0051] In one embodiment, the electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI). Using the aforementioned lithium salt can reduce the risk of gas generation in lithium-ion batteries and improve their fast-charge cycle performance and high-temperature storage performance.

[0052] In one embodiment, the lithium salt has a mass percentage content of 6% to 20% based on the total mass of the electrolyte. For example, the lithium salt mass percentage content can be 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a range of any two of these values. Controlling the lithium salt mass percentage content within the above range allows for an optimized balance between conductivity, safety, interface stability, thermal stability, and cost, thereby enabling the lithium-ion battery to simultaneously possess high energy density, good fast-charge cycle performance, and high-temperature storage performance.

[0053] In one embodiment, the lithium salt is lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide in a mass ratio of 8:(0.5 to 1.5). For example, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide can be 8:0.5, 8:0.6, 8:0.8, 8:1, 8:1.2, 8:1.3, 8:1.5, or a range of any two of these values. Using this lithium salt can further reduce the risk of gas generation in lithium-ion batteries, which is beneficial for further improving the fast-charge cycle performance and high-temperature storage performance of lithium-ion batteries.

[0054] In this application, the electrolyte further includes a solvent selected from at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl propionate, ethyl propionate, propyl acetate, methyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2-difluoroethyl acetate; the mass percentage of the solvent is from 50% to 93% based on the mass of the electrolyte. For example, the mass percentage of the solvent can be 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 93%, or a range of any two of these values, based on the mass of the electrolyte.

[0055] In one embodiment, the negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector; the negative electrode material layer includes a negative electrode active material, which includes silicon. The phrase "a negative electrode material layer disposed on at least one surface of the negative current collector" means that the negative electrode material layer can be disposed on one surface of the negative current collector along its thickness direction, or on two surfaces of the negative current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative current collector, or a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved. Silicon has extremely high theoretical specific capacity and low lithium intercalation potential, and can provide Li in multiple directions. + Insertion / deintercalation channels. Using the electrolyte of this application in conjunction with silicon-containing negative electrode sheets can not only improve the capacity of lithium-ion batteries, but also alleviate problems such as unstable growth and volume expansion of the SEI film caused by silicon, thereby improving the energy density, fast charge cycle performance and high-temperature storage performance of lithium-ion batteries.

[0056] In one embodiment, the silicon content by mass percentage is 0.5% to 15% based on the total mass of the negative electrode material layer. For example, the silicon content by mass percentage can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range of any two of these values. In this application, the silicon content in the negative electrode material layer can be controlled by adjusting the mass percentage of the silicon-containing negative electrode active material. Controlling the silicon content within the above range is beneficial for improving the lithium-ion battery capacity and avoids the risk of unstable SEI film growth and volume expansion due to excessive silicon, enabling the lithium-ion battery to simultaneously possess high energy density, good fast-charge cycle performance, and good high-temperature storage performance.

[0057] In one embodiment, the negative electrode active material may be a silicon-based material known in the art for use in lithium-ion batteries. For example, it may include at least one of the following silicon-based materials: elemental silicon, silicon oxides, silicon-carbon composites, and CVD silicon (i.e., silicon materials prepared by chemical vapor deposition). The negative electrode active material may also include carbon materials, such as at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, and nanocarbon.

[0058] In one embodiment, the lithium-ion battery further includes a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector; the positive electrode material layer comprises a positive electrode active material; the positive electrode active material is selected from LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, and LiNi. x Co y Mn 1-x- y At least one of O2, wherein 0 < x < 1, 0 < y < 1, 0 < 1 - xy < 1. The aforementioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the positive electrode current collector, or only a portion of the surface area; this application has no particular limitation, as long as the purpose of this application can be achieved. Using the above-mentioned types of positive electrode active materials is beneficial to improving the electrochemical performance of lithium-ion batteries, but there is a risk of dissolution of transition metal elements, and the decomposition byproduct of the first additive in this application is PO3F2. -It possesses the ability to bind transition metal ions, preventing them from diffusing to the negative electrode and damaging the SEI film, thereby overcoming the dissolution defects of the aforementioned positive electrode active material. Simultaneously, the second additive contains the highly electronegative group -CN, which coordinates with the transition metal, inhibiting its dissolution and tunneling. The lone pair electrons of the -CN component can act as sacrificial agents for HF and H2O, forming stable F(O)·HN hydrogen bonds with HF, or with both HF and H2O. This facilitates the stable operation of the aforementioned positive electrode active material during cycling, resulting in higher energy density, better fast-charge cycle performance, and better high-temperature storage performance in lithium-ion batteries.

[0059] In one embodiment, the positive electrode active material is LiNi. x Co y Mn 1-x-y For O2, 0.3 ≤ x ≤ 0.98. For example, x can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.98, or a range of any two of these values. Using this positive electrode active material can also improve the discharge specific capacity of lithium-ion batteries.

[0060] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil, aluminum alloy foil, nickel foil, or nickel alloy. The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite positive electrode current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0061] This application does not impose any particular limitation on the thickness of the positive electrode material layer and the positive electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided positive electrode material layer is 60 μm to 90 μm, and the thickness of the positive electrode current collector is 10 μm to 20 μm.

[0062] In one embodiment, the positive electrode material layer may further include a conductive agent. This application does not particularly limit the type of conductive agent, as long as it achieves the purpose of this application. For example, the conductive agent may include at least one of conductive carbon black (Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber. In one embodiment, the positive electrode material layer may further include a binder. This application does not particularly limit the type of binder, as long as it achieves the purpose of this application. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. This application does not particularly limit the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0063] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer; it can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0064] This application does not impose any particular limitation on the preparation method of the positive electrode sheet, as long as it achieves the purpose of this application. For example, the positive electrode sheet can be prepared by dispersing the positive active material, conductive agent, and binder in a certain proportion in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry with a solid content of 40wt% to 65wt%. The positive electrode slurry is uniformly coated on one surface of the positive current collector, and after drying, a positive electrode sheet with a single-sided coating of positive electrode material is obtained. Then, the above coating steps are repeated on the other surface of the positive current collector, and after drying, a positive electrode sheet with a double-sided coating of positive electrode material is obtained. After cold pressing, edge trimming, cutting, and slitting, the slitting is dried under vacuum conditions, and electrode tabs are welded to obtain the positive electrode sheet.

[0065] This application does not impose any particular limitation on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, or foamed copper can be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0066] This application does not impose any particular limitation on the thickness of the negative electrode material layer and the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 40 μm to 60 μm, and the thickness of the negative electrode current collector is 8 μm to 14 μm.

[0067] In one embodiment, the negative electrode material layer may further include a binder. This application does not particularly limit the type of binder, as long as it achieves the purpose of this application. For example, the binder may include at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). In one embodiment, the negative electrode material layer may further include a conductive agent. This application does not particularly limit the type of conductive agent, as long as it achieves the purpose of this application. For example, the conductive agent may include at least one selected from conductive carbon black (Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0068] The negative electrode material layer may also include a thickener, which may include, but is not limited to, at least one of sodium carboxymethyl cellulose (CMC-Na) and lithium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer; those skilled in the art can select them according to actual needs, as long as the purpose of this application can be achieved.

[0069] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0070] This application does not impose any particular limitation on the preparation method of the negative electrode sheet, as long as it can achieve the purpose of this application. For example, the negative electrode sheet can be prepared by dispersing the negative electrode active material, conductive agent, binder and thickener in a certain proportion in a solvent (e.g., deionized water) to form a negative electrode slurry with a solid content of 40wt% to 60wt%. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided coating of negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided coating of negative electrode material layer is obtained. After cold pressing, edge trimming, cutting, and slitting, the slitting is dried under vacuum conditions, and electrode tabs are welded to obtain the negative electrode sheet.

[0071] In this application, the lithium-ion battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the separator material can be selected from, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), glass fiber, polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), and polyamide (PA). The type of separator can include at least one of woven membrane, ceramic membrane, nonwoven fabric, microporous membrane, composite membrane, rolled membrane, and spun membrane.

[0072] This application does not impose any particular limitation on the thickness of the diaphragm, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be from 4 μm to 20 μm.

[0073] In this application, the lithium-ion battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of lithium-ion batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0074] The preparation process of the lithium-ion battery in this application is well known to those skilled in the art, and this application does not have any particular limitations. For example, the preparation process of the lithium-ion battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, separator and negative electrode sheet in sequence, and winding, folding and other operations as needed to obtain a wound electrode assembly, placing the electrode assembly into the housing, injecting the electrolyte into the housing and obtaining the lithium-ion battery through vacuum sealing, standing, formation and capacity testing.

[0075] In this application, during the charging and discharging process of a lithium-ion battery, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator, positioned between the positive and negative electrode plates, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0076] Example

[0077] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0078] Test methods and equipment:

[0079] Fast charging cycle performance test:

[0080] At 25℃, the lithium-ion battery was charged at a constant current of 3C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C. It was then discharged at a constant current of 1.0C to 2.75V, which was recorded as one charge-discharge cycle. This charge-discharge cycle was repeated 1000 times. The discharge capacity of the first and 1000th cycles was recorded and denoted as A1 and A2, respectively. 1000 Capacity retention (%) after 1000 cycles at 25℃ (3CC / 1DC) = A 1000 / A1×100%.

[0081] High-temperature storage performance test:

[0082] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 0.5 hours to allow it to reach a constant temperature. It was then charged at a constant current of 1C to a voltage of 4.25V, followed by constant voltage charging at 4.25V until a cutoff current of 0.05C was reached. Afterward, it was discharged at a constant current of 1C until a voltage of 2.5V was reached, and the initial discharge capacity was recorded as B0. The lithium-ion battery was then charged at a constant current of 1C to a voltage of 4.25V, followed by constant voltage charging at 4.25V until a cutoff current of 0.05C was reached. Finally, the lithium-ion battery was placed in a 60°C explosion-proof oven and stored for 30 days. Afterward, the lithium-ion battery was removed and cooled to room temperature. At 25℃, the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C, and then discharged at a constant current of 1C to a voltage of 2.5V. This constitutes one charge-discharge cycle. The above charge-discharge cycle was repeated for 3 weeks, and the discharge capacity of the third week was recorded as B2. The capacity recovery rate (%) after 30 days of storage at 60℃ is calculated as B2 / B0 × 100%.

[0083] Energy density test:

[0084] The lithium-ion battery was placed in a constant temperature chamber at 25℃±2℃ and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C until the voltage reached 4.25V, followed by charging at a constant voltage of 4.25V until the current reached 0.05C, and then discharging at a constant current of 0.2C until the voltage reached 2.5V. The discharge energy was recorded. Volumetric energy density = discharge energy / (length of lithium-ion battery × width of lithium-ion battery × thickness of lithium-ion battery). The length, width, and thickness of the lithium-ion battery were measured using a micrometer, with each value measured three times, and the average value was taken as the final result.

[0085] Example 1-1

[0086] <Preparation of Electrolyte>

[0087] In an argon-atmospheric glove box (water content <10ppm, oxygen content <1ppm), ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed uniformly at a mass ratio of 3:7 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI), first additive compound I-1, and second additive compound II-1 were added and mixed uniformly to obtain an electrolyte. Based on the total mass of the electrolyte, the mass percentage of LiPF6 was 15%, the mass percentage of LiFSI was 1%, the mass percentage of the first additive was 1%, the mass percentage of the second additive was 0.5%, and the balance was the base solvent.

[0088] <Preparation of the positive electrode>

[0089] LiNi, the positive electrode active material 0.9 Co 0.05 Mn 0.05 O2, conductive carbon black (SuperP) and carbon nanotubes, and polyvinylidene fluoride (PVDF) binder were mixed evenly at a mass ratio of 94:2.5:1.5:2 and added to N-methylpyrrolidone (NMP). The mixture was then stirred under vacuum to obtain a positive electrode slurry with a solid content of 53 wt%. This slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil current collector. After drying at 85°C, a single-sided positive electrode sheet with a 76 μm coating thickness was obtained. The above steps were repeated on the other surface of the aluminum foil to obtain a double-sided positive electrode sheet. After cold pressing, edge trimming, cutting, and slitting, the slitting was dried at 85°C under vacuum for 10 hours. Electrode tabs were then welded to obtain a 70 mm × 54 mm positive electrode sheet with a positive electrode material layer areal density of 30 mg / cm³. 2 .

[0090] <Preparation of Negative Electrode Sheets>

[0091] The negative electrode active material, silicon-based material SiC-XCVD silicon (purchased from Jiangxi Zichen Technology Co., Ltd.), carbon material artificial graphite, conductive agent conductive carbon black (SuperP, SP), thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber emulsion (SBR) were thoroughly mixed in a mass ratio of 20:75:2:1:2, added to deionized water, and stirred under vacuum to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry was uniformly coated onto one surface of a 9μm thick copper foil current collector, and dried at 85℃ to obtain a single-sided negative electrode sheet with a coating thickness of 49μm. The above steps were repeated on the other surface of the copper foil to obtain a double-sided negative electrode sheet. After cold pressing, edge trimming, cutting, and slitting, the slitting was dried at 85℃ under vacuum for 12 hours, and electrode tabs were welded to obtain a negative electrode sheet with a specification of 74mm×58mm and an areal density of 12mg / cm³ for the negative electrode material layer. 2 .

[0092] <Preparation of the diaphragm>

[0093] The diaphragm was purchased from Shenzhen Xingyuan Material Technology Co., Ltd., model PE, with a 9μm thick polyethylene porous polymer film as the substrate, and a 2μm adhesive coating on both sides of the substrate.

[0094] <Preparation of Lithium-ion Batteries>

[0095] The prepared positive electrode, separator, and negative electrode are stacked sequentially and wound to obtain an electrode assembly, wherein the separator serves as an insulator between the positive and negative electrode. The electrode assembly is placed in a housing (made of nickel-plated stainless steel), and the negative current collector is welded to the housing using laser welding. Moisture is removed at 85°C, and after drying, the prepared electrolyte is injected with an injection coefficient of 4.5 g / Ah. After vacuum sealing, settling, formation, and capacity testing, a lithium-ion battery with dimensions of 4.0 mm × 80 mm × 100 mm is obtained. The settling time is 24 hours, and formation is completed at 45°C with a 0.1C charge to 4.25V (forming a passivation layer).

[0096] Examples 1-2 to Examples 1-15

[0097] Except for the following in <Preparation of Electrolyte>, where the mass percentages of the first and second additives are adjusted according to Table 1, the mass percentage of the base solvent is changed accordingly, and the mass percentages of other components in the electrolyte remain unchanged, the rest is the same as in Example 1-1.

[0098] Examples 1-16 to Examples 1-23

[0099] Except for adjusting the types of the first and second additives according to Table 1 in the <Preparation of Electrolyte>, the rest is the same as in Example 1-1.

[0100] Examples 1-24 to Examples 1-28

[0101] Except for the preparation of the negative electrode sheet, in which the mass ratio of silicon-based material SiC-XCVD silicon and carbon material artificial graphite in the negative electrode active material layer is adjusted so that the mass percentage of Si in the negative electrode material layer is as shown in Table 1, and the mass percentage of the negative electrode active material in the negative electrode material layer remains unchanged, the rest is the same as in Example 1-1.

[0102] Examples 2-1 to 2-8

[0103] Except for the addition of the third additive as shown in Table 2 in the <Preparation of Electrolyte>, and the adjustment of the type and mass percentage of the third additive according to Table 2, the mass percentage of the base solvent is changed accordingly, and the mass percentage of other components in the electrolyte remains unchanged, the rest is the same as in Example 1-1.

[0104] Examples 2-9 to 2-15

[0105] Except for the preparation of the electrolyte, in which the type and mass percentage of lithium salt are adjusted according to Table 2, the mass percentage of the base solvent is changed accordingly, and the mass percentage of other components in the electrolyte remains unchanged, the rest is the same as in Example 1-1.

[0106] Comparative Example 1-1

[0107] Except that in the <Preparation of Electrolyte>, the first and second additives are not added, the mass percentage of the base solvent is changed accordingly, and the mass percentage of other components in the electrolyte remains unchanged, the rest is the same as in Example 1-1.

[0108] Comparative Examples 1-2 to 1-3

[0109] Except that in the <Preparation of Electrolyte>, no second additive is added, and the mass percentage of the first additive is adjusted according to Table 1, the mass percentage of the base solvent is changed accordingly, and the mass percentage of other components in the electrolyte remains unchanged, the rest is the same as in Example 1-1.

[0110] Comparative Examples 1-4 to 1-5

[0111] Except that in the <Preparation of Electrolyte>, the first additive is not added, and the mass percentage of the second additive is adjusted according to Table 1, the mass percentage of the base solvent is changed accordingly, and the mass percentage of other components in the electrolyte remains unchanged, the rest is the same as in Example 1-1.

[0112] Comparative Examples 1-6

[0113] Except for adjusting the type of the first additive according to Table 1 in the <Preparation of Electrolyte>, the rest is the same as in Example 1-1.

[0114] Table 1

[0115] Note: " / " in Table 1 indicates that there are no corresponding preparation parameters.

[0116] Table 2

[0117] Note: In Table 2, " / " indicates that there are no corresponding preparation parameters.

[0118] Based on the results of Examples 1-1 to 1-28, Examples 2-1 to 2-15, and Comparative Examples 1-1 to 1-6 in Tables 1 and 2, it can be seen that the silicon-based lithium-ion batteries using the first and second additives of this application have a high capacity retention rate of 3CC / 1DC after 1000 cycles at 25°C, a high capacity recovery rate after 30 days of storage at 60°C, and a high energy density. This indicates that the lithium-ion batteries have good fast-charging cycle performance and high-temperature storage performance while having high energy density.

[0119] As can be seen from Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-5, by adjusting the content of the first additive, the content of the second additive, and the mass ratio of the first additive to the second additive within the scope of this application, silicon-based lithium-ion batteries can have a high capacity retention rate of 3CC / 1DC after 1000 cycles at 25°C and a high capacity recovery rate after 30 days of storage at 60°C. This indicates that lithium-ion batteries using silicon-containing anodes have good fast-charging cycle performance and high-temperature storage performance.

[0120] As can be seen from Examples 1-1, 1-16 to 1-23 and Comparative Examples 1-6, the use of the first and second additives of this application can improve the capacity retention rate of silicon-based lithium-ion batteries after 1000 cycles at 25°C and 3CC / 1DC and the capacity recovery rate after 30 days of storage at 60°C, thereby improving the fast-charging cycle performance and high-temperature storage performance of silicon-based lithium-ion batteries.

[0121] In this application, the silicon content in the negative electrode material layer remains unchanged, and the energy density of the silicon-based lithium-ion battery also remains essentially unchanged. As can be seen from Examples 1-1, 1-24 to 1-28, with the increase of silicon content in the negative electrode material layer, the energy density of the lithium-ion battery significantly improves. Simultaneously, the fast-charging cycle performance and high-temperature storage performance show a trend of first increasing and then decreasing. The results indicate that by controlling the silicon content in the negative electrode material layer within the scope of this application, the lithium-ion battery can achieve both high energy density and better fast-charging cycle performance and high-temperature storage performance. In Examples 1-24, the addition of a small amount of Si can reduce the crosstalk of Li ions to the graphite-containing negative electrode, and Si has a lower desolvation energy, which accelerates lithium-ion migration, thus resulting in poorer fast-charging cycle performance and high-temperature storage performance of the lithium-ion battery.

[0122] As can be seen from Examples 1-1 and 2-1 to 2-8, using the third additive of this application and adjusting its content within the scope of this application can further improve the fast-charge cycle performance and high-temperature storage performance of silicon-based lithium-ion batteries. As can be seen from Examples 1-1 and 2-9 to 2-15, using the lithium salt of this application and adjusting the lithium salt content within the scope of this application can enable lithium-ion batteries to simultaneously possess good fast-charge cycle performance and high-temperature storage performance; using a lithium salt containing lithium hexafluorophosphate and lithium difluorosulfonylimide and adjusting their mass ratio within the scope of this application can further improve the fast-charge cycle performance and high-temperature storage performance of lithium-ion batteries.

[0123] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0124] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0125] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A lithium-ion battery, comprising an electrolyte and a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode active material, and the negative electrode active material comprises silicon. The electrolyte includes a first additive and a second additive, the first additive having the structural formula shown in Formula I. in, R1, R2, and R3 are each independently selected from H, F, C1 to C4 alkyl, C1 to C4 fluoroalkyl, C2 to C4 alkenyl, C2 to C4 fluoroalkenyl, C2 to C4 alkynyl, C2 to C4 fluoroalkynyl, C5 to C7 cycloalkyl, unsubstituted or R 01 Substituted phenyl, R 02 Substituted benzyl, R 01 R 02 Each is independently selected from F, C1 to C4 alkyl, C2 to C4 alkenyl, C2 to C4 alkynyl, C1 to C4 fluoroalkyl, C2 to C4 fluoroalkenyl, and C2 to C4 fluoroalkynyl; The structural formula of the second additive is shown in Formula II. R4 is selected from C1 to C6 alkyl, C2 to C6 alkenyl, and C2 to C6 alkynyl; R5-R8 are each independently selected from halogens and C1 to C6 alkyl groups; M is an alkali metal, selected from Li, Na, or K; Y + It is a monovalent cation, selected from , , or .

2. The lithium-ion battery according to claim 1, wherein, The first additive is selected from at least one of the following compounds: 。 3. The lithium-ion battery according to claim 1, wherein, The second additive is selected from at least one of the following compounds: 。 4. The lithium-ion battery according to claim 1, wherein, The mass ratio of the first additive to the second additive is 1:(0.01 to 5), preferably 1:(0.1 to 2), and more preferably 1:(0.1 to 1).

5. The lithium-ion battery according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of the first additive is 0.01% to 5%, preferably 0.1% to 2%.

6. The lithium-ion battery according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of the second additive is 0.01% to 2%, preferably 0.1% to 1%.

7. The lithium-ion battery according to claim 1, wherein, The electrolyte also includes a third additive, which is selected from at least one of vinylene carbonate and fluoroethylene carbonate; the mass percentage of the third additive is 1% to 23% based on the total mass of the electrolyte.

8. The lithium-ion battery according to claim 7, wherein, The third additive is vinylene carbonate and fluoroethylene carbonate; based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 0.05% to 3%, and the mass percentage of fluoroethylene carbonate is 2% to 20%.

9. The lithium-ion battery according to claim 1, wherein, The electrolyte also includes a lithium salt selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; the lithium salt has a mass percentage content of 6% to 20% based on the total mass of the electrolyte.

10. The lithium-ion battery according to claim 9, wherein, The lithium salt is lithium hexafluorophosphate and lithium difluorosulfonylimide in a mass ratio of 8:(0.5 to 1.5).

11. The lithium-ion battery according to any one of claims 1 to 10, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector; the negative electrode material layer includes the negative electrode active material; Based on the total mass of the negative electrode material layer, the mass percentage of silicon is 0.5% to 15%.

12. The lithium-ion battery according to any one of claims 1 to 10, wherein, The lithium-ion battery further includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector; the positive electrode material layer includes a positive electrode active material. The positive electrode active material is selected from LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, and LiNi. x Co y Mn 1-x-y At least one of O2, wherein 0 < x < 1, 0 < y < 1, 0 < 1 - xy < 1; Preferably, the positive electrode active material is LiNi. x Co y Mn 1-x-y O2, 0.3≤x≤0.98.

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