A dry-method negative material, a preparation method thereof, a dry-method negative electrode and a lithium ion battery

Abstract

The present application relates to the technical field of battery manufacturing, and in particular to a dry-method negative material, a preparation method thereof, a dry-method negative electrode and a lithium ion battery. To improve the first coulomb efficiency, rate capability and cycle stability of the high-load dry-method negative electrode, the present application introduces a polymer coating layer with specific chemical structure and ion conduction characteristics, thereby effectively inhibiting the reduction side reaction of PTFE in the dry-method negative electrode under low potential conditions, reducing the irreversible loss of active lithium, and simultaneously improving the interface bonding performance and lithium ion transmission capacity of the negative electrode tab.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, specifically to a dry-process negative electrode material and its preparation method, a dry-process negative electrode, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as highly efficient electrochemical energy storage devices, have been widely used in electric vehicles, portable electronic devices, and large-scale energy storage systems due to their high energy density, excellent cycle life, and good safety performance. With the rapid development of the new energy industry, further improving the energy density of lithium-ion batteries has always been a core issue of common concern to both academia and industry. Over the past thirty years, improvements in energy density have mainly relied on two technological paths: on the one hand, developing high-specific-capacity positive and negative electrode active materials to increase the energy storage capacity per unit mass or volume; on the other hand, optimizing electrode structure design to increase the volume fraction or areal density of active materials in the electrode. As the intrinsic specific capacity of active materials gradually approaches its theoretical limit, simply relying on improvements to the material system is no longer sufficient to achieve continuous breakthroughs in energy density. Constructing high-capacity, thick electrodes has become an important technological direction for realizing high-energy-density lithium-ion batteries.

[0003] Dry electrode technology is a solvent-free electrode fabrication technique that has emerged in recent years. It uses physical methods such as mechanical shearing, hot pressing, or rolling to directly composite and form a monolithic electrode from active materials, conductive agents, and dry binders under solvent-free conditions. Compared to traditional wet coating processes, dry electrodes offer significant advantages in the fabrication of thick electrodes. However, dry electrode technology still faces several critical challenges in the fabrication of negative electrode sheets. Existing dry negative electrode systems commonly use polytetrafluoroethylene (PTFE) as a binder, but PTFE has limited electrochemical stability within the negative electrode operating potential range. Under low potential conditions, PTFE is prone to reduction and decomposition, leading to irreversible consumption of active lithium, resulting in a decrease in the battery's initial coulombic efficiency and capacity decay. Simultaneously, PTFE itself has limited interfacial bonding ability to the negative electrode active material, making it difficult to maintain stable particle contact and structural integrity in high-load, thick electrodes over long periods, thus affecting the battery's cycle stability. Therefore, how to balance the electrochemical stability and bonding performance of the binder system in dry negative electrodes has become a key technological bottleneck restricting the further development of high-energy-density dry negative electrodes.

[0004] To address the aforementioned issues, existing technologies have attempted to introduce a polymer coating layer onto the surface of the negative electrode active material to physically isolate PTFE from direct contact with the active material, thereby suppressing reduction side reactions. For example, CN119542390A uses polymers such as carboxymethyl cellulose, polyvinylidene fluoride (PVDF), or polymethyl methacrylate (PMMA) as a protective layer, which can improve the initial coulombic efficiency of the battery to some extent. However, commonly used polymers such as carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), and PMMA have low lithium-ion conductivity, which can easily form ion transport bottlenecks in high-capacity electrodes, limiting rate performance and capacity utilization.

[0005] In addition to good interfacial stability and adhesion, the lithium-ion conductivity of polymer coating materials also significantly impacts the electrochemical performance of thick electrodes. Polyethylene oxide (PEO) polymers, for example, have ether-oxygen groups on their molecular chains that can coordinate with lithium ions, enabling lithium-ion migration and conduction through the thermal motion of polymer chain segments, thus improving the electrode's ion dynamics to some extent. However, PEO has relatively low adhesion, making it difficult to meet the requirements for long-term cycling.

[0006] In summary, existing dry anode technologies lack a coating material system that can simultaneously meet the following requirements without introducing solvents: (1) It has good electrochemical stability under the low potential environment of the negative electrode, so as to effectively suppress the reduction side reaction of PTFE and reduce the loss of active lithium; (2) It has a high interfacial bonding ability to enhance the structural stability between active materials and between them and current collectors in high-load thick electrodes; (3) It has high lithium-ion conductivity, avoiding the decrease in rate performance and capacity caused by the additional ion transport resistance introduced by the coating layer. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a modified bonding system suitable for dry-process anodes. By introducing a specific polymer coating layer on the surface of the anode active material, the system effectively suppresses the PTFE reduction side reaction while maintaining the advantages of the dry process, and balances electrode structural stability and lithium-ion transport performance, thereby improving the first coulombic efficiency, rate performance, and cycle stability of high-load dry-process anodes.

[0008] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a dry-process negative electrode material, comprising a negative electrode material matrix and a polymer coating layer covering the surface of the negative electrode material matrix; the polymer coating layer is formed of a polymer containing polar functional groups, wherein the polar functional groups are cyano groups, which can coordinate with lithium ions to construct continuous lithium ion transport channels in the negative electrode active layer, thereby improving the ionic conductivity of the electrode. The polymer coating layer is used to isolate the dry-process binder from direct contact with the negative electrode active material, thereby suppressing the reduction side reaction of the dry-process binder under the low potential environment of the negative electrode and enhancing the structural stability of the negative electrode. Furthermore, the polymer coating layer forms a physical and / or chemical anchoring effect with the dry-process binder to enhance the cohesive strength of the electrode.

[0009] Furthermore, the material of the polymer coating layer is selected from at least one of polyacrylonitrile and polyacrylonitrile derivatives.

[0010] Furthermore, the polyacrylonitrile derivative is a copolymer formed by acrylonitrile monomer and at least one of the following monomers: acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and hydroxyethyl acrylate; the mass fraction of acrylonitrile monomer in the copolymer is 10% to 90%. The cyano group is responsible for constructing faster ion transport channels, while the comonomer imparts better mechanical properties (elasticity, strength, adhesion, etc.) to the polymer by lowering its glass transition temperature, enabling it to maintain the integrity of the electrode structure when faced with the expansion of the negative electrode material.

[0011] The polymer coating layer of this invention is formed from a polymer with highly polar groups (cyano groups), and its lithium-ion conductivity is significantly higher than that of conventional coating materials such as carboxymethyl cellulose, polyvinylidene fluoride, and polymethyl methacrylate. This allows for the construction of more continuous and efficient lithium-ion transport channels in dry-process high-load negative electrodes. Furthermore, the negative electrode material matrix is ​​selected from one or more of graphite, silicon, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0012] Furthermore, the mass ratio of the negative electrode material matrix to the polymer coating layer is 99.5~96:0.5~4.

[0013] Secondly, the present invention provides a method for preparing a dry negative electrode material, comprising the following steps: (1) Add the polymer coating material to the solvent and dissolve it completely to obtain a polymer solution; (2) The polymer solution is mixed with the negative electrode material matrix to obtain a mixed slurry; (3) The mixed slurry is dried to obtain a negative electrode material with the polymer coating layer on its surface.

[0014] Furthermore, the solvent is selected from at least one of tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and water; the solid content of the polymer solution is 1% to 10%.

[0015] Furthermore, the solid content of the mixed slurry is 40% to 80% to avoid problems such as solid-liquid separation or uneven polymer dispersion during the drying process.

[0016] Secondly, the present invention provides a dry negative electrode, comprising a negative current collector and a negative active layer disposed on the negative current collector, wherein the negative active layer comprises an active material, a conductive agent and a dry binder.

[0017] Furthermore, the negative electrode current collector is copper foil; the active material is a dry-process negative electrode material; the conductive agent is selected from at least one of carbon black, carbon nanotubes, and graphene; and the dry-process binder is polytetrafluoroethylene.

[0018] After the above components are mixed evenly, a self-supporting electrode film is formed under mechanical shearing and external pressure, and then combined with the negative electrode current collector to obtain a dry negative electrode.

[0019] Furthermore, the number-average molecular weight of the polytetrafluoroethylene is 5 × 10⁻⁶. 6 ~8×10 6 The areal density of the dry-process negative electrode is 5~50 mg / cm³. 2 .

[0020] Furthermore, the mass ratio of the dry-process negative electrode material, the conductive agent, and the polytetrafluoroethylene binder is 95~98:0.5~3:1~4.

[0021] Fourthly, the present invention provides a lithium-ion battery, including the aforementioned dry-process negative electrode.

[0022] Compared with the prior art, the present invention has the following advantages: This invention introduces a polymer coating layer with specific chemical structures and ion transport properties. While maintaining the high active material loading advantage of dry-process electrodes, it effectively suppresses the reduction side reaction of PTFE in dry-process anodes under low potential conditions, reduces irreversible lithium loss, and simultaneously improves the interfacial adhesion and lithium-ion transport capacity of the anode sheet. This results in improved initial coulombic efficiency, rate performance, and cycle stability of the dry-process anode. Especially in high-load electrodes, ion transport capacity significantly deteriorates with increasing electrode thickness. Using a functional binder system with higher ion transport capacity is even more significant for improving battery coulombic efficiency and rate performance. Detailed Implementation

[0023] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0024] Comparative Example 1 Graphite, conductive carbon black, and polytetrafluoroethylene (PTFE) were dry-mixed at a mass ratio of 98:1:1. The PTFE was then subjected to shear force to fiberize it into a three-dimensional network structure. The fiberized powder was subsequently rolled to a surface density of 5 mg / cm³. 2 The self-supporting membrane was finally rolled together with copper foil to obtain a dry negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, such as capacity, initial efficiency, rate performance, and cycle stability, was tested.

[0025] Comparative Example 2 1.00 g of carboxymethyl cellulose (CMC) powder was dissolved in 9.00 g of deionized water to prepare a 10 wt% CMC polymer solution. The CMC solution and graphite powder were uniformly mixed at a graphite to CMC solid mass ratio of 99:1 to form a graphite slurry, which was then dried at 100 °C for 6 hours to obtain a CMC-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were dry-mixed at a mass ratio of 98:1:1, and then subjected to shear force to fiberize the PTFE into a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 5 mg / cm³. 2 A self-supporting film was formed and finally rolled together with copper foil to obtain a dry-process negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, including capacity, initial efficiency, rate performance, and cycle stability, was tested. The ionic conductivity of CMC powder was tested. A CMC polymer solution was coated onto the surface of copper foil and dried at 100°C to obtain a CMC film with a thickness of approximately 20 micrometers. Its adhesion was tested using a peel strength tester.

[0026] Comparative Example 3 1.00 g of CMC powder was dissolved in 9.00 g of deionized water to prepare a 10 wt% CMC polymer solution. The CMC solution and graphite powder were uniformly mixed at a graphite to CMC solid mass ratio of 99:1 to form a graphite slurry, which was then dried at 100 °C for 6 hours to obtain a CMC-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were dry-mixed at a mass ratio of 98:1:1, and then subjected to shear force to fiberize the PTFE into a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 10 mg / cm³. 2The self-supporting membrane was finally rolled together with copper foil to obtain a dry negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, such as capacity, initial efficiency, rate performance, and cycle stability, was tested.

[0027] Comparative Example 4 1.00 g of polyvinylidene fluoride (PVDF) powder was dissolved in 9.00 g of N-methylpyrrolidone to prepare a 10 wt% PVDF polymer solution. The PVDF solution and graphite powder were uniformly mixed at a graphite to PVDF solid mass ratio of 99:1 to form a graphite slurry, which was then dried at 100 °C for 6 hours to obtain a PVDF-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were dry-mixed at a mass ratio of 98:1:1, and then subjected to shear force to fiberize the PTFE into a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 5 mg / cm³. 2 A self-supporting film was formed and finally rolled together with copper foil to obtain a dry-process negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, including capacity, initial efficiency, rate performance, and cycle stability, was tested. The ionic conductivity of PVDF powder was tested. A PVDF polymer solution was coated onto the surface of copper foil and dried at 100°C to obtain a PVDF film with a thickness of approximately 20 micrometers. Its adhesion was tested using a peel strength tester.

[0028] Comparative Example 5 Silicon carbon material (nominal capacity 514 mAh / g), conductive carbon black, and polytetrafluoroethylene (PTFE) were dry-mixed at a mass ratio of 98:1:1. The PTFE was then subjected to shear force to fiberize it into a three-dimensional network structure. The fiberized powder was subsequently rolled to a surface density of 5 mg / cm³. 2 The self-supporting membrane was finally rolled together with copper foil to obtain a dry negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, such as capacity, initial efficiency, rate performance, and cycle stability, was tested. Example 1

[0029] 1.00 g of polyacrylonitrile (PAN) powder was dissolved in 9.00 g of dimethyl sulfoxide to prepare a 10 wt% PAN polymer solution. The PAN solution and graphite powder were uniformly mixed at a graphite to PAN solid mass ratio of 99:1 to form a graphite slurry, which was then dried at 100 °C for 6 hours to obtain a PAN-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were dry-mixed at a mass ratio of 98:1:1, and then subjected to shear force to fiberize the PTFE into a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 5 mg / cm³. 2 A self-supporting film was formed and finally rolled together with copper foil to obtain a dry-process negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, including capacity, initial efficiency, rate performance, and cycle stability, was tested. The ionic conductivity of PAN powder was tested. A CMC polymer solution was coated onto the surface of copper foil and dried at 100°C to obtain a CMC film with a thickness of approximately 20 micrometers. Its adhesion was tested using a peel strength tester. Example 2

[0030] 1.00 g of PAN powder was dissolved in 9.00 g of dimethyl sulfoxide to prepare a 10 wt% PAN polymer solution. The PAN solution was then uniformly mixed with graphite powder at a graphite to PAN solid mass ratio of 99:1 to form a graphite slurry. This slurry was subsequently dried at 100 °C for 6 hours to obtain a PAN-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were then dry-mixed at a mass ratio of 98:1:1. The PTFE was then subjected to shear force to fiberize, forming a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 10 mg / cm³. 2 The self-supporting membrane was finally rolled together with copper foil to obtain a dry negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box, and its electrochemical performance, such as capacity, initial efficiency, rate performance, and cycle stability, was tested. Example 3

[0031] 1.00 g of acrylonitrile-acrylic acid copolymer (PAN-PAA) powder (60% acrylonitrile monomer and 40% acrylic acid monomer) was dissolved in 9.00 g of tetrahydrofuran to prepare a 10 wt% PAN-PAA polymer solution. The PAN-PAA solution was uniformly mixed with graphite powder at a graphite to PAN-PAA solid mass ratio of 99:1 to form a graphite slurry, which was then dried at 100 °C for 6 hours to obtain a PAN-PAA-coated graphite anode material. This coated graphite, conductive carbon black, and PTFE were dry-mixed at a mass ratio of 98:1:1, and then subjected to shear force to fiberize the PTFE into a three-dimensional network structure. The fiberized powder was then rolled to a surface density of 5 mg / cm³. 2 A self-supporting film was formed and finally rolled together with copper foil to obtain a dry-process negative electrode sheet. Using this electrode sheet as the working electrode and a lithium metal sheet as the counter electrode, a CR2032 coin cell was assembled in an argon-protected glove box. Its electrochemical performance, including capacity, initial efficiency, rate capability, and cycle stability, was tested. The ionic conductivity of PAN-PAA powder was tested. A PAN-PAA polymer solution was coated onto the surface of copper foil and dried at 100°C to obtain a PAN-PAA film with a thickness of approximately 20 micrometers. Its adhesion was tested using a peel strength tester. Example 4

[0032] 1.00 g of acrylonitrile-methyl acrylate copolymer (PAN-PMA) powder (80% acrylonitrile monomer and 20% methyl acrylate monomer) was dissolved in 9.00 g of dimethylformamide (DMF) to prepare a 10 wt% solution. The solution was mixed with the polymer solids at a mass ratio of 98:2 and dried to obtain PAN-PMA-coated graphite. Subsequent dry electrode preparation processes were the same as in Example 1. Example 5

[0033] 1.00 g of acrylonitrile-butyl acrylate copolymer (PAN-PBA) powder (70% acrylonitrile monomer and 30% butyl acrylate monomer) was dissolved in 9.00 g of tetrahydrofuran to prepare a 10 wt% solution. The silicon-carbon composite material (nominal capacity 514 mAh / g) was mixed with the polymer solids at a mass ratio of 97:3 and dried to obtain PAN-PBA-coated silicon-carbon material. Subsequent dry electrode preparation processes were the same as in Comparative Example 5. Example 6

[0034] 1.00 g of acrylonitrile-butyl acrylate-hydroxyethyl acrylate terpolymer (PAN-PBA-PHEA) powder (acrylonitrile monomer content 60%, butyl acrylate monomer content 30%, hydroxyethyl acrylate monomer content 10%) was dissolved in 9.00 g of tetrahydrofuran to prepare a 10 wt% solution. The silicon-carbon composite material (nominal capacity 514 mAh / g) was mixed with the polymer solids at a mass ratio of 98.5:1.5 and dried to obtain PAN-PBA-PHEA-coated silicon-carbon material. Subsequent dry electrode preparation processes were the same as in Comparative Example 5.

[0035] The test results of Comparative Examples 1-5 and Examples 1-6 are shown in Tables 1 and 2.

[0036] Table 1 Comparison of Ionic Conductivity and Adhesion experiment Material <![CDATA[Adhesive force / N cm -1 > <![CDATA[Ionic conductivity / S cm -1 > Comparative Example 2 CMC 1.02 <![CDATA[2.32×10 -5 ]]> Comparative Example 4 PVDF 0.6 <![CDATA[2.56×10 -6 ]]> Example 1 PAN 1.24 <![CDATA[1×10 -3 ]]> Example 3 PAN-PAA (6:4) 1.32 <![CDATA[6.11×10 -4 ]]> Example 4 PAN-PMA (8:2) 1.28 <![CDATA[8.42×10 -4 ]]> Example 5 PAN-PBA (7:3) 1.45 <![CDATA[5.50×10 -4 <!-- 5 -->]]> Example 6 PAN-PBA-PHEA (6:3:1) 1.52 <![CDATA[4.85×10 -4 ]]> Table 2 Comparison of Electrochemical Performance and Electrode Thickness sample 0.05C initial discharge capacity (mAh / g) First-efficacy (%) 1C capacity retention rate (%) Capacity retention rate (%) after 200 cycles Electrode expansion rate (%) after 200 cycles Comparative Example 1 181 46 40 51 101 Comparative Example 2 296 77 42 63 77 Comparative Example 3 260 68 23 36 86 Comparative Example 4 205 53 29 52 90 Comparative Example 5 206 39 22 23 143 Example 1 313 82 79 84 38 Example 2 308 80 72 76 44 Example 3 327 86 76 87 41 Example 4 319 84 75 89 40 Example 5 421 80 69 63 59 Example 6 437 83 71 61 71 As shown in Table 1, PAN and its derivatives, due to the presence of cyano groups, have better adhesion and ionic conductivity than CMC and PVDF, which is beneficial for improving the ion conduction performance of the electrode.

[0037] Referring to Table 2, a comparison of Comparative Example 1 with Examples 1, 3, and 4 shows that the solution provided by the present invention can effectively isolate the dry binder from direct contact with the negative electrode active material, thereby suppressing the reduction side reaction of the dry binder at a low negative electrode potential and improving the first discharge capacity, first efficiency, and cycle performance.

[0038] Comparing Examples 1, 3, and 4 with Comparative Examples 2 and 4, it can be seen that the present invention is significantly superior to CMC and PVDF in suppressing side reactions, improving electrochemical performance, and reducing electrode expansion rate (increasing cohesion).

[0039] As can be seen from the comparison between Example 2 and Comparative Example 3, the present invention helps to improve the ion conduction characteristics of high-load electrode, thereby further improving its overall electrochemical performance, and verifying the role of the coating material in improving ion conductivity.

[0040] As can be seen from the comparison of Examples 5 and 6 with Comparative Example 5, the present invention also has the effects of suppressing side reactions, improving electrochemical performance and reducing electrode expansion rate in silicon-based anodes.

[0041] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0042] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dry-process negative electrode material, characterized in that, It includes a negative electrode material matrix and a polymer coating layer covering the surface of the negative electrode material matrix; the polymer coating layer is formed by a polymer containing polar functional groups, wherein the polar functional groups are cyano groups, and the polymer coating layer is used to isolate the dry binder from direct contact with the negative electrode active material, and to form a physical and / or chemical anchoring effect with the dry binder.

2. The dry-process negative electrode material according to claim 1, characterized in that, The polymer coating material is selected from at least one of polyacrylonitrile and polyacrylonitrile derivatives.

3. The dry-process negative electrode material according to claim 2, characterized in that, The polyacrylonitrile derivative is a copolymer formed by acrylonitrile monomer and at least one of the following monomers: acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and hydroxyethyl acrylate; the mass fraction of acrylonitrile monomer in the copolymer is 10% to 90%.

4. The dry-process negative electrode material according to claim 1, characterized in that, The negative electrode material matrix is ​​selected from one or more of graphite, silicon, silicon-carbon composite material, and silicon-oxygen composite material; the mass ratio of the negative electrode material matrix to the polymer coating layer is 99.5~96:0.5~4.

5. A method for preparing the dry-process negative electrode material according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Add the polymer coating material to the solvent and dissolve it completely to obtain a polymer solution; (2) The polymer solution is mixed with the negative electrode material matrix to obtain a mixed slurry; (3) The mixed slurry is dried to obtain a negative electrode material with the polymer coating layer on its surface.

6. The method for preparing a dry-process negative electrode material according to claim 5, characterized in that, The solvent is selected from at least one of tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and water; the solid content of the polymer solution is 1% to 10%.

7. The method for preparing a dry-process negative electrode material according to claim 5, characterized in that, The solid content of the mixed slurry is 40% to 80%.

8. A dry-process negative electrode, characterized in that, It includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, wherein the negative electrode active layer includes the dry negative electrode material, conductive agent and dry binder as described in any one of claims 1 to 4.

9. A dry-process negative electrode according to claim 8, characterized in that, The mass ratio of the dry-process negative electrode material, conductive agent, and polytetrafluoroethylene binder is 95~98:0.5~3:1~4.

10. A lithium-ion battery, characterized in that, Includes the dry negative electrode as described in claim 8.