Lithium ion battery and method of manufacturing the same

Abstract

The application provides a lithium ion battery and a preparation method thereof. The battery and the preparation method comprise: a composite lithium metal negative electrode comprising lithium metal and lithium nitrate attached to the surface of the lithium metal; the gel polymer electrolyte comprises, in terms of mass percentage: 1-10 wt% of a comonomer, 60-85 wt% of an organic solvent, 5-20 wt% of a lithium salt and 0-10 wt% of an additive; the organic solvent comprises a cyclic fluorinated carbonate, a chain fluorinated carbonate and a fluorinated ether compound; the comonomer is an acrylate monomer; and the mass percentage of lithium nitrate in the composite lithium metal negative electrode is less than or equal to 25%. In the lithium ion battery, the lithium nitrate attached to the surface of the lithium metal can be decomposed into Li3N on the surface of the negative electrode to form a stable and uniform Li3N-rich SEI film. The three solvents are fluorinated solvents, and through the above two aspects, the lithium ion battery can simultaneously have high energy density and excellent room temperature and high temperature cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a lithium-ion battery and its preparation method. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, the requirements for their electrochemical components (e.g., batteries) are becoming increasingly stringent. For example, batteries are not only required to be lightweight, but also to have short charging times and long operating lifespans. Among the various battery types, lithium metal batteries have garnered significant attention in research and development due to their highest energy density. Currently, improving the cycle performance of lithium metal batteries has become a key focus of research in this field.

[0003] By combining artificial solid electrolyte membrane (SEI) with lithium metal anode, gel electrolyte, and novel lithium metal electrolyte, high energy density of lithium-ion batteries can be achieved while achieving long-term cycling at both room temperature (25 degrees Celsius) and high temperature (45 degrees Celsius).

[0004] The specific capacity of lithium metal as the anode can reach 3860 mAh / g, which is more than ten times higher than the theoretical specific capacity of graphite (372 mAh / g). However, lithium metal has the lowest chemical potential (-3.04V) and very high reactivity. In the battery, it reacts with the electrolyte, consuming lithium, increasing battery impedance, and ultimately leading to cycle failure. Therefore, while using metal as the anode material can significantly improve energy density, it also drastically shortens cycle life.

[0005] There are two important directions for improving the cycle performance of lithium metal batteries: 1. Forming a stable solid electrolyte interphase (SEI) film on the surface of the lithium metal anode. A uniform and stable SEI can reduce the reactivity of lithium metal with the electrolyte and inhibit the formation of lithium dendrites, effectively improving the cycle performance of the battery. The SEI can be formed by adjusting the electrolyte composition, reducing the electrolyte on the anode surface, or by artificially synthesizing it on the anode surface. 2. Developing electrolytes with low reactivity with the lithium metal anode. The electrolyte can be liquid, gel, or all-solid. Reducing the reactivity of the electrolyte with lithium metal can effectively improve the battery's cycle coulombic efficiency and cycle life. Summary of the Invention

[0006] The main objective of this invention is to provide a lithium-ion battery and its preparation method, so as to solve the problem that existing lithium-ion batteries cannot simultaneously achieve high energy density and excellent room temperature and high temperature cycle performance.

[0007] To achieve the above objectives, according to one aspect of the present invention, a lithium-ion battery is provided, comprising a composite lithium metal anode, a positive electrode, and a gel polymer electrolyte. The composite lithium metal anode comprises lithium metal and lithium nitrate attached to the surface of the lithium metal. The gel polymer electrolyte comprises, by mass percentage: 1–10 wt% comonomer, 60–85 wt% organic solvent, 5–20 wt% lithium salt, and 0–10 wt% additives. The organic solvent comprises cyclic fluorocarbonate, chain fluorocarbonate, and fluoroether compounds. The comonomer is an acrylate monomer. The mass percentage of lithium nitrate in the composite lithium metal anode is ≤25%.

[0008] Furthermore, the mass percentage of lithium nitrate in the aforementioned composite lithium metal anode is 2-20%.

[0009] Further, by mass percentage, the above organic solvent comprises: 1 to 40 parts of cyclic fluorocarbonate, 1 to 70 parts of chain fluorocarbonate, and 1 to 40 parts of fluoroether compound; wherein the general chemical formula of the cyclic fluorocarbonate is shown in Formula I:

[0010]

[0011] R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine atoms, and C1 to C4 atoms. 12 Alkyl groups, C1-C 12 Fluoroalkyl, C3-C 12 cycloalkyl, C3-C 12 Fluorinated cycloalkyl groups, C2-C 12 alkenyl, C2~C 12 Fluoroalkenyl, C3~C 12 heterocyclic groups and C3-C 12 Any one of the fluorinated heterocyclic groups, and at least one of R1, R2, R3 and R4 is selected from fluorine atoms, C1 to C4. 12 Fluoroalkyl, C3-C 12 Fluorinated cycloalkyl groups, C2-C 12 Fluorinated alkenyl groups and C3-C 12 The fluorinated heterocyclic group is selected from any one of the substituents; preferably, R1, R2, R3 and R4 are each independently selected from any one of hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 cycloalkyl, C3-C6 fluorocycloalkyl, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C3-C6 heterocyclic group and C3-C6 fluoroheterocyclic group, and at least one of R1, R2, R3 and R4 is selected from any one of the substituents of fluorine atom, C1-C6 fluoroalkyl, C3-C6 fluorocycloalkyl, C2-C6 fluoroalkenyl and C3-C6 fluoroheterocyclic group; preferably, the cyclic fluorocarbonate is selected from Any one or more of the following; and / or, the general chemical formula of the chain fluorocarbonate is shown in Formula II:

[0012]

[0013] Among them, R5 and R6 are each independently selected from hydrogen, fluorine atoms, C1 to C2 atoms. 12 Alkyl groups, C1-C 12 Fluoroalkyl, C1-C 12 alkoxy groups, C1-C 12 fluoroalkoxy, C2-C 12 alkenyl, C2~C 12 Fluoroalkenyl, C6-C 26 aryl, C6-C 26 Any one of the fluoroaryl groups, and at least one of R5 and R6 is selected from C1 to C6. 12 Fluoroalkyl, C1-C 12 fluoroalkoxy, C2-C 12 Fluoroalkenyl and C6~C 26 The fluoroaryl group is selected from any one of the substituents; preferably, R5 and R6 are each independently selected from hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C1-C6 fluoroalkoxy, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C6-C 12 aryl, C6-C 12 The fluoroaryl group is selected from any one of the following, and at least one of R5 and R6 is selected from C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, C2-C6 fluoroalkenyl, and C6-C6 fluoroalkyl groups. 12 Any one of the substituents in the fluoroaryl group; preferably, the chain fluorocarbonate is selected from...

[0014] Any one or more of the following; and / or, the general chemical formula of the fluoroether compound is shown in Formula III:

[0015]

[0016] R7 and R8 are each independently selected from C1 to C2. 10 Halogenated alkyl groups, C1-C 10 Halogenated alkoxy groups, C2-C 10 The halogenated alkenyl group is selected from any one of the following: preferably, R7 and R8 are each independently selected from any one of C1-C6 haloalkyl, C1-C6 haloalkoxy, and C2-C6 haloalkenyl groups; preferably, the fluoroether compound is...

[0017] Furthermore, the aforementioned comonomers include acrylate monomers with a network cross-linked structure and chain acrylate monomers, wherein the acrylate monomers with a network cross-linked structure are ethoxylated trimethylolpropane triacrylate and / or trimethylolpropane triacrylate; and / or, the chain acrylate monomers are selected from any one or more of ethyl acetoacetate, methyl methacrylate, ethyl acrylate and decaacrylate; and / or, the mass ratio of the acrylate monomers with a network cross-linked structure to the chain acrylate monomers is 1:(0.1-20).

[0018] Furthermore, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium di(oxalate borate), lithium di(fluorooxalate borate), lithium di(fluorooxalate borate), lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

[0019] Furthermore, the above-mentioned additives are selected from any one or more of the following: fluoroethylene carbonate, ethylene ethylene, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, methane disulfonate, 4-trifluoromethyl ethylene carbonate, 1,3,2-dioxazolthiophene-2,2-dioxide, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, succinic anhydride, propylene sulfite, propylene-1,3-sulfonyl lactone, bis(trimethylsilyl)sulfate, lithium nitrate, N-methyl-butylpyrrolidone bis(trifluoromethanesulfonyl)imide, N-methyl-propylpiperidine bis(trifluoromethanesulfonyl)imide, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

[0020] According to another aspect of the present invention, a method for preparing the above-mentioned lithium-ion battery is provided. The method includes: step S1, mixing lithium nitrate with oil to obtain a mixed solution, coating the mixed solution on a rolling mill, and mechanically rolling a lithium metal matrix using the rolling mill to obtain a composite lithium metal anode; step S2, mixing raw materials including comonomers, organic solvents, lithium salts and additives to obtain a mixed liquid; step S3, stacking a positive electrode, a separator and a composite lithium metal anode in sequence to obtain a laminate, welding tabs and placing the laminate in an aluminum-plastic film, and sequentially performing vacuum sealing, injection of mixed liquid, standing and in-situ polymerization and formation to obtain a lithium-ion battery.

[0021] Further, in step S1 above, the mass percentage of lithium nitrate in the mixed solution is 2-20%; and / or, the oil is selected from Group I base oil and / or ester oil; and / or, during the mechanical rolling process, the total deformation of the thickness of the lithium metal matrix is ​​5-100%, and the water content in the mechanical rolling environment is <0.5ppm.

[0022] Furthermore, in step S2 above, the raw materials also include an initiator, which is azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0023] Furthermore, in step S3 above, the in-situ polymerization temperature is 45–80°C, and / or the in-situ polymerization time is 2–24 h.

[0024] Applying the technical solution of this application, on the one hand, lithium nitrate adhering to the lithium metal surface in a lithium-ion battery can decompose into Li3N on the negative electrode surface, forming a stable and uniform Li3N-rich SEI film. This Li3N-rich SEI film, due to its high lithium-ion conductivity, low resistivity, and high Young's modulus, is considered to effectively promote uniform lithium deposition / stripping, suppress the formation of lithium dendrites and dead lithium, thereby improving the cycle stability of the battery. On the other hand, all three solvents are fluorinated solvents. Among them, cyclic fluorocarbonates have excellent solubility for lithium salts and can also form C and O-containing organic polymer SEIs on the negative electrode surface, exhibiting excellent performance after combining with inorganic LiF and Li3N. Chain-like fluorocarbonates can participate in the formation of F-rich films on both the positive and negative electrodes, and can also adjust the viscosity of the electrolyte. Furthermore, their use in conjunction with cyclic fluorocarbonates helps reduce the reactivity of the electrolyte at the positive electrode, which is beneficial for long battery cycle life. Fluoroether compounds have excellent lithium-ion solubility and serve as the primary solvent for lithium transport. During lithium solvation, they form a stable five-membered ring structure, which enhances the battery's lithium solvation capability. Through these two effects, lithium-ion batteries can simultaneously achieve high energy density and excellent cycle performance at both room temperature and high temperature. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0026] As analyzed in the background section of this application, existing lithium-ion batteries have the problem of simultaneously achieving high energy density and excellent room temperature and high temperature cycling performance. In order to solve this problem, this application provides a lithium-ion battery and its preparation method.

[0027] In a typical embodiment of this application, a lithium-ion battery is provided, comprising a composite lithium metal anode, a positive electrode, and a gel polymer electrolyte. The composite lithium metal anode comprises lithium metal and lithium nitrate attached to the surface of the lithium metal. The gel polymer electrolyte, by mass percentage, comprises: 1–10 wt% comonomer; 60–85 wt% organic solvent; 5–20 wt% lithium salt; and 0–10 wt% additives. The organic solvent includes cyclic fluorocarbonates, chain fluorocarbonates, and fluoroether compounds; the comonomer is an acrylate monomer; and the mass percentage of lithium nitrate in the composite lithium metal anode is ≤25%.

[0028] On the one hand, lithium nitrate adhering to the lithium metal surface in lithium-ion batteries can decompose into Li3N on the negative electrode surface, forming a stable and uniform Li3N-rich SEI film. This Li3N-rich SEI film, due to its high lithium-ion conductivity, low resistivity, and high Young's modulus, is considered to effectively promote uniform lithium deposition / stripping, inhibit lithium dendrite formation and dead lithium formation, thereby improving the battery's cycle stability. On the other hand, all three solvents are fluorinated solvents. Cyclic fluorocarbonates have excellent solubility for lithium salts and can form C and O-containing organic polymer SEIs on the negative electrode surface, exhibiting excellent performance when combined with inorganic LiF and Li3N. Chain-like fluorocarbonates can participate in the formation of F-rich films on both the positive and negative electrodes, and can also adjust the electrolyte viscosity. Furthermore, their use in conjunction with cyclic fluorocarbonates helps reduce the electrolyte's reactivity at the positive electrode, which is beneficial for long battery cycle life. Fluoroether compounds have excellent lithium-ion solubility and serve as the primary solvent for lithium transport. During lithium solvation, they form a stable five-membered ring structure, which enhances the battery's lithium solvation capability. Through these two effects, lithium-ion batteries can simultaneously achieve high energy density and excellent cycle performance at both room temperature and high temperature.

[0029] In some embodiments of this application, the mass percentage of lithium nitrate in the composite lithium metal anode is 2-20%.

[0030] Lithium nitrate on the surface of the composite lithium metal anode decomposes during the electrochemical process after battery assembly, generating Li3N, a highly efficient and stable SEI film component. If the mass percentage of lithium nitrate is less than 2%, the amount of Li3N generated is insufficient to form a dense SEI film, failing to effectively suppress lithium dendrite formation and leading to poor cycle performance. Conversely, if the mass percentage exceeds 20%, lithium nitrate will precipitate on the lithium surface, potentially reducing electrolyte stability and causing excessively thick localized SEI films inside the battery, increasing internal resistance and affecting kinetic performance. Controlling the mass percentage of lithium nitrate between 2% and 20% helps to further optimize the surface structure of the composite lithium metal anode, forming a more uniform and stable SEI film, effectively reducing the risk of electrolyte decomposition, and improving battery cycle stability and energy efficiency.

[0031] Furthermore, the mass percentage of lithium nitrate in the composite lithium metal anode can be 2%, 3%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 13%, 15%, 18%, 19%, or 20%. Of course, the mass percentage of lithium nitrate in the composite lithium metal anode can be any value within the range of 2% to 20%, preferably any value within the range of 2% to 10%, which will not be elaborated further here. In some embodiments of this application, the organic solvent, by mass percentage, includes: 1 to 40 parts of cyclic fluorocarbonate; 1 to 70 parts of chain fluorocarbonate; and 1 to 40 parts of fluoroether compound; wherein the general chemical formula of the cyclic fluorocarbonate is shown in Formula I:

[0032]

[0033] R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine atoms, and C1 to C4 atoms. 12 Alkyl groups, C1-C 12 Fluoroalkyl, C3-C 12 cycloalkyl, C3-C 12 Fluorinated cycloalkyl groups, C2-C 12 alkenyl, C2~C 12 Fluoroalkenyl, C3~C 12 heterocyclic groups and C3-C 12 Any one of the fluorinated heterocyclic groups, and at least one of R1, R2, R3 and R4 is selected from fluorine atoms, C1 to C4. 12 Fluoroalkyl, C3-C 12 Fluorinated cycloalkyl groups, C2-C 12 Fluorinated alkenyl groups and C3-C 12The fluorinated heterocyclic group is selected from any one of the substituents; preferably, R1, R2, R3 and R4 are each independently selected from any one of hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 cycloalkyl, C3-C6 fluorocycloalkyl, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C3-C6 heterocyclic group and C3-C6 fluoroheterocyclic group, and at least one of R1, R2, R3 and R4 is selected from any one of the substituents of fluorine atom, C1-C6 fluoroalkyl, C3-C6 fluorocycloalkyl, C2-C6 fluoroalkenyl and C3-C6 fluoroheterocyclic group; preferably, the cyclic fluorocarbonate is selected from Any one or more of the following; and / or, the general chemical formula of the chain fluorocarbonate is shown in Formula II:

[0034]

[0035] Among them, R5 and R6 are each independently selected from hydrogen, fluorine atoms, C1 to C2 atoms. 12 Alkyl groups, C1-C 12 Fluoroalkyl, C1-C 12 alkoxy groups, C1-C 12 fluoroalkoxy, C2-C 12 alkenyl, C2~C 12 Fluoroalkenyl, C6-C 26 aryl, C6-C 26 Any one of the fluoroaryl groups, and at least one of R5 and R6 is selected from C1 to C6. 12 Fluoroalkyl, C1-C 12 fluoroalkoxy, C2-C 12 Fluoroalkenyl and C6~C 26 The fluoroaryl group is selected from any one of the substituents; preferably, R5 and R6 are each independently selected from hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C1-C6 fluoroalkoxy, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C6-C 12 aryl, C6-C 12 The fluoroaryl group is selected from any one of the following, and at least one of R5 and R6 is selected from C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, C2-C6 fluoroalkenyl, and C6-C6 fluoroalkyl groups. 12 Any one of the substituents in the fluoroaryl group; preferably, the chain fluorocarbonate is selected from... Any one or more of the following; and / or, the general chemical formula of the fluoroether compound is shown in Formula III:

[0036]

[0037] R7 and R8 are each independently selected from C1 to C2. 10 Halogenated alkyl groups, C1-C 10 Halogenated alkoxy groups, C2-C 10 The halogenated alkenyl group is selected from any one of the following: preferably, R7 and R8 are each independently selected from any one of C1-C6 haloalkyl, C1-C6 haloalkoxy, and C2-C6 haloalkenyl groups; preferably, the fluoroether compound is...

[0038] The organic solvent system with the above specific ratio plays an important role in the gel polymer electrolyte, affecting the electrochemical performance and cycle stability of lithium-ion batteries. The specific technical effects and principles are as follows:

[0039] Cyclic fluorocarbonate forms a LiF-rich electrolyte interphase (SEI) film on the negative electrode surface, composed of lithium ion (LiF) and organic polymers. LiF exhibits good conductivity for lithium ions but high impedance to electrons, which helps improve the stability of the SEI film and reduces lithium dendrite formation. The organic polymer component ensures the flexibility of the SEI film, reducing SEI film rupture caused by volume changes during battery charging and discharging. However, excessively high cyclic fluorocarbonate content increases electrolyte viscosity, affecting lithium ion transport, while excessively low content may lead to insufficient SEI film formation, limiting its contribution to improving battery performance. Therefore, controlling the content of cyclic fluorocarbonate within 1 to 40 parts is an important parameter for optimizing the SEI membrane composition and maintaining electrolyte fluidity and electrochemical stability. The content of cyclic fluorocarbonate can be controlled at 1, 2, 5, 8, 10, 12, 13, 15, 17, 19, 20, 22, 25, 30, 32, 35, 38, or 40 parts. Of course, the content of cyclic fluorocarbonate can be any value within the range of 1 to 40 parts, which will not be elaborated further here.

[0040] Excessive content of chain fluorocarbonate may reduce the solubility of other components in the electrolyte (such as lithium salt), affecting the electrolyte conductivity and battery performance. Controlling the content of chain fluorocarbonate from 1 to 70 parts can effectively regulate the physicochemical properties of the electrolyte, including reducing viscosity, increasing the solubility of lithium salt, and maintaining the supply of fluorine (F) required for SEI film formation. The content of chain fluorocarbonate can be 1 part, 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 13 parts, 15 parts, 17 parts, 19 parts, 20 parts, 22 parts, 25 parts, 30 parts, 32 parts, 35 parts, 38 parts, 39 parts, 40 parts, 41 parts, 45 parts, 50 parts, 53 parts, 55 parts, 60 parts, 65 parts, 67 parts, or 70 parts. Of course, the content of chain fluorocarbonate can be any value within the range of 1 to 70 parts, which will not be elaborated here.

[0041] Excessive fluoroether compound content may increase its volatility within the battery, while insufficient fluoroether compound content may affect the lithium-ion transport rate. Maintaining the fluoroether compound content between 1 and 40 parts can ensure sufficiently high electrolyte conductivity while reducing volatility, allowing the battery to maintain excellent performance under different temperature conditions. The fluoroether compound content can be 1, 2, 5, 8, 10, 12, 13, 14, 15, 16, 17, 19, 20, 22, 25, 30, 32, 35, 38, or 40 parts. Of course, the fluoroether compound content can be any value within the range of 1 to 40 parts, which will not be elaborated further here.

[0042] In summary, controlling the specific content ratio of cyclic fluorocarbonates, chain fluorocarbonates, and fluoroether compounds within the above-mentioned range not only optimizes the formation of the SEI film, improves its stability and flexibility, and reduces the internal impedance of the battery, but also regulates the physicochemical properties of the electrolyte, including viscosity, conductivity, and stability, thereby significantly improving the cycle performance and safety of lithium-ion batteries under normal and high temperature conditions.

[0043] Furthermore, the preferred types of cyclic fluorocarbonates, chain fluorocarbonates, and fluoroether compounds are more conducive to improving the synergistic effect among the three, thereby enhancing the battery's ability to solvate lithium.

[0044] In some embodiments of this application, the comonomer includes a network-crosslinked acrylate monomer and a chain-like acrylate monomer, wherein the network-crosslinked acrylate monomer is ethoxylated trimethylolpropane triacrylate, and / or trimethylolpropane triacrylate; and / or, the chain-like acrylate monomer is selected from any one or more of ethyl acetoacetate, methyl methacrylate, ethyl acrylate, and decaacrylate; and / or, the mass ratio of the network-crosslinked acrylate monomer to the chain-like acrylate monomer is 1:(0.1-20).

[0045] The network-crosslinked acrylate monomers form a three-dimensional network structure through self-crosslinking, which endows the gel polymer electrolyte with good mechanical strength and stability. This structure can effectively prevent lithium dendrite penetration, reducing the adverse effects of lithium dendrites on battery performance and safety. Simultaneously, the three-dimensional network structure can restrict electrolyte movement, reduce electrolyte volatilization, and improve electrolyte retention in the battery, thereby improving battery stability under different temperature conditions. The chain-like acrylate monomers are mainly responsible for providing pathways for lithium ion transport in the electrolyte. Their chain structure allows lithium ions to flow freely within the polymer backbone, improving the electrolyte's conductivity. However, an excessively high proportion of chain-like monomers may lead to insufficient rigidity of the polymer framework, potentially failing to effectively prevent lithium dendrite growth; conversely, an excessively low proportion of chain-like monomers results in insufficient flexibility of the copolymer and inadequate lithium ion conduction capacity, which may reduce lithium ion transport capacity and affect the battery's kinetic performance. This approach achieves a balance between flexibility and rigidity by optimizing the structure and ratio of comonomers. Specifically, the flexible segments are used to transport lithium ions, while the rigid segments provide the overall rigidity of the framework. This not only improves the effective transport of lithium ions but also provides sufficient mechanical strength to suppress lithium dendrites. It achieves a balance between the stability of the gel polymer electrolyte structure and the lithium ion transport performance, thereby improving the battery's cycle performance, kinetic performance, and safety, especially its performance under room temperature and high temperature conditions. This provides strong technical support for the development of high-energy-density lithium-ion batteries.

[0046] In addition, the copolymer framework formed by the above acrylate monomers can encapsulate the electrolyte within the framework, reducing the reactivity of the electrolyte with the positive and negative electrodes, thereby improving the interfacial stability of the positive and negative electrodes. It can also reduce the amount of electrolyte used, thereby improving the long-cycle performance of the battery.

[0047] In some embodiments of this application, the mass ratio of the above-mentioned network cross-linked acrylate monomer to the chain acrylate monomer can be 1:0.1, 1:0.5, 1:1, 1:2, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18 or 1:20. Of course, the mass ratio of the network cross-linked acrylate monomer to the chain acrylate monomer can be any value within 5% to 100%. Preferably, the total deformation of the thickness of the lithium metal matrix can be any value within 1:(0.1 to 20). Further, it is preferred that the total deformation of the thickness of the lithium metal matrix can be any value within 1:(1 to 10), which will not be elaborated here. In some embodiments of this application, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

[0048] Lithium salts primarily function as lithium ions in electrolytes, and their type and content directly affect the electrolyte's conductivity. Preferred lithium salts exhibit higher lithium-ion conductivity, which helps improve the lithium-ion transport rate within the battery, thereby enhancing its charge-discharge performance and kinetics, reducing internal resistance, and increasing energy and power density.

[0049] In some embodiments of this application, the additive is selected from any one or more of the following: fluoroethylene carbonate, ethylene ethylene, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, methane disulfonate, 4-trifluoromethyl ethylene carbonate, 1,3,2-dioxazolthiophene-2,2-dioxide, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, succinic anhydride, propylene sulfite, propylene-1,3-sulfonyl lactone, bis(trimethylsilyl)sulfate, lithium nitrate, N-methyl-butylpyrrolidone bis(trifluoromethanesulfonyl)imide, N-methyl-propylpiperidine bis(trifluoromethanesulfonyl)imide, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

[0050] The selection and use of the above-mentioned additives have a significant impact on the electrochemical performance, cycle stability, and safety of lithium-ion batteries. By improving the characteristics of the SEI film and optimizing electrolyte performance, the cycle performance, kinetic performance, and safety of the battery are enhanced. The synergistic effect of these additives with lithium salts, copolymer frameworks, and artificial solid electrolyte membranes achieves a comprehensive improvement in battery energy density, cycle stability, and safety, making them an important component of high-performance lithium metal battery design.

[0051] In another typical embodiment of this application, a method for preparing a lithium-ion battery is provided. Step S1: Lithium nitrate is mixed with oil to obtain a mixed solution. The mixed solution is coated on a rolling mill. After mechanically rolling the lithium metal matrix using the rolling mill, a composite lithium metal anode is obtained. Step S2: Raw materials including comonomers, organic solvents, lithium salts, and additives are mixed to obtain a mixed liquid. Step S3: A positive electrode, a separator, and a composite lithium metal anode are stacked in sequence to obtain a laminate. After welding tabs, the laminate is placed in an aluminum-plastic film and sequentially undergoes vacuum sealing, injection of the mixed liquid, standing and in-situ polymerization, and formation to obtain a lithium-ion battery.

[0052] In step S1, lithium nitrate is dissolved in a specific oil and uniformly coated onto a rolling mill, and then mechanically rolled to process the lithium metal substrate. The key to this process is to uniformly distribute lithium nitrate on the surface of the lithium metal anode, thus laying the foundation for the formation of a Li3N-rich SEI film on the lithium metal anode surface. This step cleverly solves the problems in existing technologies where the extremely low solubility of lithium nitrate in the electrolyte leads to insufficient formation of a Li3N-rich SEI film, and excessive addition results in precipitation in the electrolyte. In step S2, the mixture obtained by mixing comonomers, organic solvents, lithium salts, and additives provides a balance between rigidity and flexibility, effectively preventing lithium dendrite penetration while maintaining electrolyte fluidity. In step S3, through vacuum encapsulation, injection of the mixture, settling, and in-situ polymerization, a gel polymer electrolyte is formed, perfecting the lithium-ion battery structure. The formation process further improves the stability of the SEI film and the electrochemical performance of the battery. This series of assembly and preparation steps ensures close contact between the various components inside the battery and uniform distribution of the electrolyte inside the battery. The lithium-ion battery obtained by the above preparation method can simultaneously achieve high energy density and excellent room temperature and high temperature cycling performance.

[0053] In some embodiments of this application, in step S1, the mass percentage of lithium nitrate in the mixed solution is 2-20%; and / or, the oil is selected from Group I base oil and / or ester oil; and / or, during the mechanical rolling process, the total deformation of the thickness of the lithium metal matrix is ​​5-100%, and the water content in the mechanical rolling environment is <0.5ppm.

[0054] Insufficient lithium nitrate concentration results in an inadequate concentration to form a Li3N-rich SEI film, limiting its protective effect on the lithium metal surface and increasing the likelihood of internal side reactions, thus impacting battery cycle performance and safety. Excessive lithium nitrate concentration, on the other hand, may cause precipitation on the lithium surface, affecting not only the uniformity and stability of the SEI film but also potentially damaging the internal battery structure and reducing performance consistency. Type I base oils, ester oils, or mixtures thereof offer good coatability and compatibility on the lithium metal surface, promoting uniform distribution of lithium nitrate and forming an effective SEI film. By precisely controlling the mass ratio of lithium nitrate, the choice of oil, the deformation of the lithium metal matrix, and the water content of the mechanical rolling environment, lithium nitrate is added to the oil used during lithium strip rolling. Through the lithium strip preparation process, lithium nitrate is uniformly coated onto the lithium metal surface. After battery assembly, the lithium nitrate decomposes into Li3N on the negative electrode surface, forming a stable and uniform SEI, thereby improving battery cycle stability. If the substrate deformation is too small, the mechanical heat generated during rolling is insufficient, making it impossible to uniformly coat the rolling oil containing dissolved lithium nitrate. Conversely, if the substrate deformation is too large, strip breakage is likely to occur during rolling, affecting production efficiency. Therefore, the total thickness deformation of the lithium metal substrate should be controlled between 5% and 100% during rolling. This ensures appropriate deformation of the lithium metal during mechanical rolling, achieving uniform coating of lithium metal and reducing the risk of lithium dendrite formation, while preventing lithium metal breakage due to excessive deformation, which would affect battery assembly and performance. Lithium metal readily reacts with water, producing hydrogen gas and corrosive byproducts. This not only consumes the lithium source but also increases the internal impedance of the battery, ultimately leading to a significant decrease in battery cycle performance. Controlling the water content in the operating environment to <0.5ppm helps reduce the risk of lithium metal reacting with water.

[0055] Furthermore, the mass percentage of lithium nitrate in the mixed solution can be 2%, 3%, 5%, 6%, 7%, 9%, 10%, 11%, 13%, 15%, 18%, 19%, or 20%. Of course, the mass percentage of lithium nitrate in the mixed solution can be any value within the range of 2% to 20%. Preferably, the mass percentage of lithium nitrate in the mixed solution can be any value within the range of 2% to 10%. Further, it is preferred that the mass percentage of lithium nitrate in the mixed solution can be any value within the range of 2% to 5%. This will not be elaborated further here.

[0056] Furthermore, the total deformation of the thickness of the lithium metal matrix can be 5%, 6%, 7%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. Of course, the total deformation of the thickness of the lithium metal matrix can be any value within the range of 5% to 100%. Preferably, the total deformation of the thickness of the lithium metal matrix can be any value within the range of 5% to 50%. Further, it is preferred that the total deformation of the thickness of the lithium metal matrix can be any value within the range of 5% to 10%. This will not be elaborated further here.

[0057] In some embodiments of this application, in step S2, the raw materials further include an initiator, which is azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0058] Initiators such as azobisisobutyronitrile (AIBN) generate free radicals through decomposition, which initiate the polymerization of comonomers, ensuring efficient initiation and precise control of the polymerization reaction. The resulting gel polymer electrolyte has good mechanical strength, conductivity, and electrochemical stability, and works synergistically with other battery components to effectively improve the cycle performance and safety of lithium-ion batteries under normal and high temperature conditions.

[0059] In some embodiments of this application, in step S3, the temperature of in-situ polymerization is 45–80°C, and / or the time of in-situ polymerization is 2–24 h.

[0060] Temperature control during in-situ polymerization is a crucial parameter for ensuring the formation of gel polymer electrolytes. At 60°C, the polymerization reaction proceeds stably, promoting effective bonding between comonomers and forming a gel polymer framework with a three-dimensional network structure. This temperature range is chosen to balance the polymerization rate and product quality. Too low a temperature will slow down the polymerization reaction, potentially leading to incomplete gel polymer electrolyte formation and affecting the electrolyte's uniformity and stability; while too high a temperature may trigger side reactions, causing structural damage to the gel polymer electrolyte and affecting battery cycle performance and safety. Sufficient time ensures the polymerization reaction proceeds fully, allowing the comonomers to form a uniform and dense gel polymer electrolyte, improving its mechanical strength and conductivity. Insufficient polymerization time may result in incomplete polymerization, a loose electrolyte structure, and affect lithium-ion transport efficiency and battery cycle stability; while excessive time may cause over-polymerization, leading to excessive electrolyte solidification, reducing its fluidity, and affecting battery kinetic performance. By precisely controlling the temperature and time of in-situ polymerization, this technical solution can ensure the quality of gel polymer electrolyte formation, achieving high mechanical strength, good conductivity, and stable electrochemical performance. These meticulous process control parameters ensure good compatibility of the gel polymer electrolyte among the internal components of the battery, improving the battery's cycle performance, kinetic performance, and safety.

[0061] Furthermore, the in-situ polymerization temperature can be 45℃, 46℃, 47℃, 49℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃. Of course, the in-situ polymerization temperature can be any value within the range of 45℃ to 80℃. Preferably, the in-situ polymerization temperature can be any value within the range of 45℃ to 60℃. Further, it is preferred that the in-situ polymerization temperature can be any value within the range of 45℃ to 50℃. These details will not be elaborated further here.

[0062] Furthermore, the in-situ polymerization time can be 2h, 3h, 4h, 5h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 23h, or 24h. Of course, the in-situ polymerization time can be any value within 2h to 24h. Preferably, the in-situ polymerization time can be any value within 2h to 10h. Further, it is preferred that the in-situ polymerization time can be any value within 2h to 6h. These will not be elaborated further here.

[0063] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0064] Example 1

[0065] 1. Preparation of composite lithium metal anodes

[0066] X wt.% lithium nitrate was dissolved in a Group I base oil and stirred until homogeneous. The solution was then coated onto a rolling mill and physically rolled to bond the lithium metal onto a copper foil negative electrode current collector with a thickness of approximately 12 μm. By adjusting the roller pressure, lithium was coated on one side of the copper current collector, with a thickness controlled to approximately 50 μm. After cutting and slitting, the coated material was stored in a dry argon-atmosphere glove box for later use. The water content in the mechanical rolling environment was <0.5 ppm. During the mechanical rolling process, the total deformation of the lithium metal matrix thickness was 80%.

[0067] 2. Preparation of the positive electrode

[0068] Nickel-cobalt-manganese (NCM) positive electrode active material, conductive agent (Super P conductive carbon), and binder polyvinylidene fluoride were mixed in a weight ratio of approximately 97:1.4:1.6. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry with a solid content of approximately 72 wt%. The positive electrode slurry was uniformly coated onto a positive electrode current collector aluminum foil, dried, and then cold-pressed, cut, and slit. Finally, it was dried under vacuum at approximately 85°C for about 4 hours to obtain the positive electrode.

[0069] 3. Preparation of the diaphragm

[0070] Polyethylene (PE) with a thickness of approximately 15 μm is used as the diaphragm.

[0071] 4. Gel polymer

[0072] In a dry argon atmosphere, the cyclic fluorocarbonate shown in Formula A, the chain fluorocarbonate shown in Formula B, and the fluoroether compound shown in Formula C are mixed uniformly with a fluorinated organic solvent. Then, the lithium salt shown in Formula D and the additive shown in Formula E are added to the resulting mixed solution and dissolved uniformly to obtain a mixed liquid. Next, a network cross-linked ethoxylated trimethylolpropane triacrylate and a chain acetoacetic acid methyl methacrylate with a mass ratio of 1:Y are added to the mixture. Azobisisobutyronitrile (AIB) is added as an initiator at a mass ratio of 0.5 wt% of the total monomers. After stirring uniformly, the mixture is awaited for injection.

[0073]

[0074] 5. Preparation and Testing of Lithium Metal Batteries

[0075] The positive electrode, separator, and artificial solid electrolyte membrane composite lithium metal negative electrode are stacked in sequence and then layered. After welding the tabs, the electrode is placed in the outer packaging aluminum-plastic film, vacuum sealed, injected with a mixed solution, left to stand at room temperature for 24 hours, and then heated at 60°C for 12 hours for in-situ polymerization to obtain a gel polymer electrolyte. The process includes formation (0.02C constant current charging to 3.75V, and then 0.1C constant current charging to 4.3V), shaping, capacity testing, and other steps to obtain a soft-pack stacked lithium metal battery.

[0076] The operation methods of the remaining embodiments and comparative examples are the same as those in Embodiment 1, except that some parameters are different, as shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] Comparative Example 9

[0081] The difference from Example 1 is that the contents of cyclic fluorocarbonate A, chain fluorocarbonate B, fluoroether compound C (wt%), and lithium salt D are 13wt%, 65wt%, 14wt%, and 4wt%, respectively, and a soft-pack stacked lithium metal battery is finally obtained.

[0082] Example 7

[0083] The difference from Example 1 is that the ratio of network cross-linked structure / chain structure 1:Y = 1:0.1, which ultimately yields a soft-pack stacked lithium metal battery.

[0084] Example 8

[0085] The difference from Example 1 is that the ratio of the network cross-linked structure to the chain structure 1:Y = 1:20, which ultimately yields a soft-pack stacked lithium metal battery.

[0086] Example 9

[0087] The difference from Example 1 is that during the mechanical rolling process, the total deformation of the lithium metal matrix thickness is 5%, ultimately resulting in a soft-pack stacked lithium metal battery.

[0088] Example 10

[0089] The difference from Example 1 is that during the mechanical rolling process, the total deformation of the thickness of the lithium metal matrix is ​​100%, and a soft-pack stacked lithium metal battery is finally obtained.

[0090] Example 11

[0091] The difference from Example 1 is that during the mechanical rolling process, the total deformation of the lithium metal matrix thickness is 4%, ultimately resulting in a soft-pack stacked lithium metal battery.

[0092] Example 12

[0093] The difference from Example 1 is that during the mechanical rolling process, the total deformation of the thickness of the lithium metal matrix is ​​105%, and a soft-pack stacked lithium metal battery is finally obtained.

[0094] The obtained lithium metal batteries were subjected to cycle tests on a charge-discharge device, charged to 4.3V at a charging rate of 0.3C and then discharged to 3V at a discharging rate of 1C, and this cycle was repeated. Table 2 shows the test results of the examples and comparative examples.

[0095] Table 2

[0096]

[0097]

[0098] As can be seen from the test results of Examples 1 to 4, combining the artificial solid electrolyte membrane composite lithium metal anode and the gel polymer electrolyte provided by the present invention in lithium metal batteries is beneficial to improving the room temperature cycle performance and high temperature cycle performance of lithium metal batteries.

[0099] Comparing Example 2 with Examples 1, 3, and 4, it can be seen that the addition of additives improves the cycle performance of lithium metal batteries to some extent, but the additives facilitate lithium deposition in the negative electrode film formation.

[0100] Comparing Comparative Example 1 with Example 1, it can be seen that if lithium nitrate is not added during the preparation of the lithium metal anode to form a Li3N-rich SEI film, the cycle performance of the battery will be greatly affected.

[0101] Comparing Comparative Example 2 with Example 1, it can be seen that if too much is added, lithium nitrate will precipitate on the lithium surface, which will not only affect the cycle performance of the battery, but also affect the consistency of the battery.

[0102] Comparing Comparative Example 3 with Example 1, it can be seen that if the copolymer monomer is not added and a gel polymer electrolyte is not formed, the cycle performance of the battery, especially the high-temperature cycle performance, will be greatly affected. This is because the copolymer framework will trap the electrolyte within the framework, reducing the reactivity of the electrolyte with the positive and negative electrodes, thereby improving the interfacial stability of the positive and negative electrodes, and thus improving the long-term cycle performance of the battery.

[0103] Comparing Comparative Example 4 with Example 1, it can be seen that if too much copolymer monomer is added, the degree of electrolyte curing will be too high, the kinetic performance of the battery will decrease, which will greatly affect the room temperature cycling performance of the battery.

[0104] Comparing Examples 5 and 6 with Example 1, it can be seen that the mass ratio of network crosslinked structure to chain structure in the copolymer needs to be appropriate. If the mass ratio of chain monomers is too low, the copolymer will lack flexibility and have insufficient lithium-ion conduction capacity. If the mass ratio of chain monomers is too high, the copolymer will lack rigidity and will not be able to effectively prevent lithium dendrite penetration.

[0105] Comparing Comparative Examples 5, 6, and 7 with Example 1, it is evident that these three solvents need to be used in combination to achieve better cycling performance. Fluorinated solvents form a LiF-based SEI on the negative electrode surface and are more oxidation-resistant on the positive electrode side, which is beneficial for the long-cycle performance of lithium metal batteries.

[0106] Comparing Comparative Example 8 with Example 1, it can be seen that the lithium salt content cannot be too high. If it is too high, the viscosity of the electrolyte will be too high, and the battery will have difficulty cycling normally.

[0107] Comparing Comparative Example 9 with Example 1, it can be seen that the concentration of lithium salt cannot be too low. If it is too low, the lithium ion strength is insufficient to support charge-discharge cycles, thereby affecting the cycle performance.

[0108] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0109] On the one hand, lithium nitrate adhering to the lithium metal surface in lithium-ion batteries can decompose into Li3N on the negative electrode surface, forming a stable and uniform Li3N-rich SEI film. This Li3N-rich SEI film, due to its high lithium-ion conductivity, low resistivity, and high Young's modulus, is considered to effectively promote uniform lithium deposition / stripping, inhibit lithium dendrite formation and dead lithium formation, thereby improving the battery's cycle stability. On the other hand, all three solvents are fluorinated solvents. Cyclic fluorocarbonates have excellent solubility for lithium salts and can form C and O-containing organic polymer SEIs on the negative electrode surface, exhibiting excellent performance when combined with inorganic LiF and Li3N. Chain-like fluorocarbonates can participate in the formation of F-rich films on both the positive and negative electrodes, and can also adjust the electrolyte viscosity. Furthermore, their use in conjunction with cyclic fluorocarbonates helps reduce the electrolyte's reactivity at the positive electrode, which is beneficial for long battery cycle life. Fluoroether compounds have excellent lithium-ion solubility and serve as the primary solvent for lithium transport. During lithium solvation, they form a stable five-membered ring structure, which enhances the battery's lithium solvation capability. Through these two effects, lithium-ion batteries can simultaneously achieve high energy density and excellent cycle performance at both room temperature and high temperature.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, comprising a composite lithium metal anode, a positive electrode, and a gel polymer electrolyte, characterized in that, The composite lithium metal anode comprises lithium metal and lithium nitrate attached to the surface of the lithium metal; the gel polymer electrolyte comprises, by mass percentage: 1~10wt% comonomer; 60~85wt% organic solvent; 5~20wt% lithium salt; 0~10wt% additives; The organic solvent includes 1-40 parts of cyclic fluorocarbonate, 1-70 parts of chain fluorocarbonate and 1-40 parts of fluoroether compound. The comonomer is an acrylate monomer; The mass percentage of lithium nitrate in the composite lithium metal anode is ≤25%; The mass percentage of lithium nitrate in the composite lithium metal anode is greater than 0%. The comonomer includes a network cross-linked acrylate monomer and a chain acrylate monomer, wherein the mass ratio of the network cross-linked acrylate monomer to the chain acrylate monomer is 1:(0.1~20).

2. The lithium-ion battery according to claim 1, characterized in that, The mass percentage of lithium nitrate in the composite lithium metal anode is 2-20%.

3. The lithium-ion battery according to claim 1 or 2, characterized in that, The general chemical formula of the cyclic fluorocarbonate is shown in Formula I: Formula I R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine atoms, and C1~C4 atoms. 12 Alkyl, C1~C 12 Fluoroalkyl, C3~C 12 cycloalkyl, C3~C 12 Fluorinated cycloalkyl groups, C2~C 12 alkenyl, C2~C 12 Fluoroalkenyl, C3~C 12 heterocyclic groups and C3~C 12 The fluorinated heterocyclic group is selected from any one of the following, and at least one of R1, R2, R3 and R4 is selected from fluorine atoms, C1~C4. 12 Fluoroalkyl, C3~C 12 Fluorinated cycloalkyl groups, C2~C 12 Fluoroalkenyl and C3~C 12 Any one of the substituents in the fluorinated heterocyclic group; And / or, the general chemical formula of the chain fluorocarbonate is shown in Formula II: Formula II R5 and R6 are each independently selected from hydrogen, fluorine atoms, and C1~C atoms. 12 Alkyl, C1~C 12 Fluoroalkyl, C1~C 12 alkoxy groups, C1~C 12 fluoroalkoxy, C2~C 12 alkenyl, C2~C 12 Fluoroalkenyl, C6~C 26 aryl, C6~C 26 Any one of the fluoroaryl groups, and at least one of R5 and R6 is selected from C1 to C6. 12 Fluoroalkyl, C1~C 12 fluoroalkoxy, C2~C 12 Fluoroalkenyl and C6~C 26 Any one of the substituents in the fluorinated aryl group; And / or, the general chemical formula of the fluoroether compound is shown in Formula III: Formula III R7 and R8 are each independently selected from C1 to C2. 10 Halogenated alkyl groups, C1~C 10 Halogenated alkoxy groups, C2~C 10 Any one of the haloalkenyl groups.

4. The lithium-ion battery according to claim 3, characterized in that, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 cycloalkyl, C3-C6 fluorocycloalkyl, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C3-C6 heterocyclic group, and C3-C6 fluoroheterocyclic group, and at least one of R1, R2, R3, and R4 is selected from any one of fluorine atom, C1-C6 fluoroalkyl, C3-C6 fluorocycloalkyl, C2-C6 fluoroalkenyl, and C3-C6 fluoroheterocyclic group, and at least one of the substituents.

5. The lithium-ion battery according to claim 4, characterized in that, The cyclic fluorocarbonate is selected from , and Any one or more of the following.

6. The lithium-ion battery according to claim 3, characterized in that, R5 and R6 are each independently selected from hydrogen, fluorine atom, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C1-C6 fluoroalkoxy, C2-C6 alkenyl, C2-C6 fluoroalkenyl, C6-C 12 aryl, C6~C 12 The R5 and R6 are selected from any one of the fluoroaryl groups, and at least one of them is selected from C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, C2-C6 fluoroalkenyl and C6-C6 fluoroalkyl groups. 12 Any one of the substituents in the fluorinated aryl group.

7. The lithium-ion battery according to claim 6, characterized in that, The chain fluorocarbonate is selected from , and Any one or more of the following.

8. The lithium-ion battery according to claim 3, characterized in that, R7 and R8 are each independently selected from any one of C1-C6 haloalkyl, C1-C6 haloalkoxy, and C2-C6 haloalkenyl groups.

9. The lithium-ion battery according to claim 8, characterized in that, The fluoroether compound is and / or .

10. The lithium-ion battery according to claim 1 or 2, characterized in that, The acrylate monomers of the network cross-linked structure are ethoxylated trimethylolpropane triacrylate and / or trimethylolpropane triacrylate; And / or, the chain-like acrylate monomer is selected from any one or more of ethyl acetoacetate methacrylate, methyl methacrylate, ethyl acrylate, and decaacrylate.

11. The lithium-ion battery according to claim 1 or 2, characterized in that, The lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

12. The lithium-ion battery according to claim 1 or 2, characterized in that, The additive is selected from any one or more of the following: fluoroethylene carbonate, ethylene ethylene, lithium dioxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, methane disulfonate, 4-trifluoromethyl ethylene carbonate, 1,3,2-dioxazolthiophene-2,2-dioxide, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, succinic anhydride, propylene sulfite, propylene-1,3-sulfonyl lactone, bis(trimethylsilyl)sulfate, lithium nitrate, N-methyl-butylpyrrolidone bis(trifluoromethanesulfonyl)imide, N-methyl-propylpiperidine bis(trifluoromethanesulfonyl)imide, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

13. A method for preparing a lithium-ion battery according to any one of claims 1 to 12, the method comprising: Step S1: Lithium nitrate is mixed with oil to obtain a mixed solution. The mixed solution is coated on a rolling mill. The lithium metal matrix is ​​mechanically rolled using the rolling mill to obtain a composite lithium metal anode. Step S2: Mix the raw materials including comonomer, organic solvent, lithium salt and additives to obtain a mixture; Step S3: The positive electrode, separator and the composite lithium metal negative electrode are stacked in sequence to obtain a laminate. After welding the tabs, the laminate is placed in an aluminum-plastic film and then sequentially vacuum-sealed, injected with the mixture, left to stand and in-situ polymerized, and formed to obtain the lithium-ion battery.

14. The preparation method according to claim 13, characterized in that, In step S1, the mass percentage of lithium nitrate in the mixed solution is 2-20%. And / or, the oil is selected from Group I base oils and / or ester oils; And / or, during the mechanical rolling process, the total deformation of the thickness of the lithium metal matrix is ​​5-100%, and the water content in the mechanical rolling environment is <0.5ppm.

15. The preparation method according to claim 13 or 14, characterized in that, In step S2, the raw material further includes an initiator, which is azobisisobutyronitrile and / or azobisisoheptanenitrile.

16. The preparation method according to claim 13 or 14, characterized in that, In step S3, the temperature of the in-situ polymerization is 45~80℃, and / or the time of the in-situ polymerization is 2~24h.

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