A negative electrode sheet and its preparation method, sodium-ion battery

Abstract

This invention provides a negative electrode sheet, its preparation method, and a sodium-ion battery. The negative electrode sheet includes a current collector, a base coating, and a negative electrode active material layer disposed along its thickness direction; the base coating includes a sodium source material and a conductive agent. The sodium-ion battery made from this negative electrode sheet exhibits good initial charge-discharge performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a negative electrode sheet and its preparation method, and a sodium-ion battery. Background Technology

[0002] Sodium-ion batteries, with their abundant resources and low cost, are considered one of the most promising alternatives to lithium-ion batteries. However, compared to the mature graphite anode materials for lithium-ion batteries, developing high-performance sodium-ion anode materials still faces key challenges. Hard carbon, due to its unique microstructure and good sodium storage performance, has become the most commercially promising sodium-ion anode material. However, its irreversible capacity loss during charge and discharge due to solid-liquid interface film formation results in low initial coulombic efficiency and poor rate performance, limiting its widespread application.

[0003] In existing technologies, sodium replenishment techniques are commonly used to compensate for initial capacity loss. For example, sodium metal foil is placed between the negative electrode and the separator, or sodium-rich compounds are added to the electrodes as a sodium replenishing agent. However, metallic sodium is chemically reactive, requiring strict control of the production environment and processes, and poses safety hazards. Furthermore, some sodium-rich compounds have high decomposition voltages or poor compatibility with electrode slurries and electrolytes, thus reducing the initial performance and process stability of the battery, limiting its practical application. Summary of the Invention

[0004] This invention provides a negative electrode sheet and its preparation method, as well as a sodium-ion battery, which has good initial charge-discharge performance.

[0005] According to one aspect of the present invention, a negative electrode sheet is provided, comprising a current collector, a base coating, and a negative electrode active material layer disposed along its thickness direction; the base coating comprises a sodium source material and a conductive agent.

[0006] In this invention, by adding a sodium source material to the base coating, the sodium source material maintains its chemical stability. During the first charge and discharge of the battery, the sodium source material provides additional sodium ions, which compensate for the irreversible capacity loss caused by SEI film formation, effectively improving the battery's first charge and discharge efficiency. Therefore, the sodium-ion battery provided by this solution exhibits superior first charge and discharge performance.

[0007] Preferably, the sodium source material includes Na2P. During the first charge and discharge of the battery, the Na2P in the sodium source material decomposes. The decomposition products not only provide additional sodium ions but also serve as a dense and stable SEI film composed of inorganic components. This SEI film is less prone to rupture during battery cycling, reducing side reactions and lowering battery polarization. Furthermore, this SEI film offers lower resistance to sodium ion transport, increasing the sodium ion transport rate and thus further improving the battery's first charge and discharge efficiency and rate performance.

[0008] Preferably, the mass ratio of sodium source material to conductive agent is 1:(1~5). Controlling the mass ratio of sodium source material to conductive agent within the range of 1:(1~5) ensures sufficient sodium source material in the base coating, thereby fully utilizing its sodium replenishment function to enhance the sodium ion transport rate. Furthermore, the conductive agent forms a continuous and stable conductive network, promoting uniform electron transport and further improving the battery's initial charge / discharge efficiency, cycle stability, and rate performance.

[0009] Preferably, the conductive agent includes at least one of carbon nanotubes and carbon black. When the conductive agent includes at least one of carbon nanotubes and carbon black, the unique tubular hollow structure and surface defects of carbon nanotubes can serve as a rapid diffusion path for sodium ions during battery charging and discharging, thereby increasing the sodium ion transport rate and improving the rate performance of the battery. Furthermore, the sodium source material can form chemical bonds with the carbon atoms at the defect sites of the carbon nanotubes. These chemical bonds allow the sodium source material to adhere more stably to the surface of the conductive agent, ensuring the stability of the electrode structure and further improving the cycle stability of the battery. Carbon black can optimize the slurry flowability to meet the requirements of the coating process.

[0010] Preferably, the conductive agent includes carbon nanotubes; the carbon nanotubes include multi-walled carbon nanotubes; the content of multi-walled carbon nanotubes in the base coating is 1% to 3% by mass percentage. When multi-walled carbon nanotubes are used as the conductive agent, the good mechanical strength and flexible network structure of the multi-walled carbon nanotubes can effectively buffer the volume change stress of the electrode during charging and discharging, thereby maintaining the integrity of the electrode structure.

[0011] Preferably, the diameter of the multi-walled carbon nanotubes is 10~20 nm.

[0012] Preferably, the specific surface area of ​​the multi-walled carbon nanotubes is 200~300 m². 2 / g.

[0013] Preferably, the conductive agent includes carbon nanotubes and carbon black; the carbon nanotubes include multi-walled carbon nanotubes; the carbon black includes acetylene black; and the mass ratio of multi-walled carbon nanotubes to acetylene black is 1:(3~67).

[0014] Preferably, the current collector is made of aluminum foil.

[0015] According to another aspect of the present invention, a method for preparing a negative electrode sheet is provided, comprising the following steps: coating a current collector with a primer slurry, drying the primer slurry to obtain a base coating layer; subsequently coating an active material slurry on the base coating layer, drying the active material slurry to obtain a negative electrode sheet; wherein the primer slurry comprises an oil-based solvent and a sodium source material.

[0016] Preferably, the solvent includes N-methylpyrrolidone. The oil-based properties of N-methylpyrrolidone help to isolate the sodium source material from air during the preparation process, thereby reducing the possibility of Na2P hydrolysis or oxidation and helping to maintain the chemical stability of the sodium source material in the undercoat.

[0017] Preferably, the sodium source material accounts for 20% to 25% of the total mass of the primer slurry, calculated by mass percentage.

[0018] Preferably, the oil-based solvent accounts for 70% to 80% of the total mass of the primer slurry, calculated by mass percentage.

[0019] According to another aspect of the present invention, a sodium-ion battery is provided, comprising a negative electrode sheet or a negative electrode sheet prepared by the above-described preparation method. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Example 1 This embodiment provides a method for preparing a negative electrode sheet, including the following steps: S1-1. Preparation of the primer slurry: The first binder, the first conductive agent, and the sodium source material are mixed in a mass ratio of 1:7.5:2.5, and then an oil-based solvent is added to obtain the primer slurry. In the materials used above, the oil-based solvent is N-methylpyrrolidone, the first binder is PVDF, the first conductive agent is composed of multi-walled carbon nanotubes and acetylene black in a mass ratio of 1:3, and the sodium source material is Na2P. By mass percentage, the oil-based solvent accounts for 75% of the total mass of the primer slurry, and the multi-walled carbon nanotubes account for 2% of the total mass of the primer slurry.

[0022] S1-2. Preparation of the base coating: The above-mentioned base coating slurry is coated on an aluminum foil with a thickness of 12 μm, and then the base coating slurry is dried at a temperature of 140°C to form a base coating on the surface of the aluminum foil with a thickness of 3 μm.

[0023] S2-1. Preparation of negative electrode active material slurry: The negative electrode active material, the second binder, and the second conductive agent are mixed evenly in a mass ratio of 8:1:1 to obtain the negative electrode active material slurry. Among the materials used above, the negative electrode active material is KHC-1 (Guangdong Kaijin), the second binder is LA133, and the second conductive agent is Super P (Swiss Temir).

[0024] S2-2. Preparation of negative electrode active material layer: The above-mentioned negative electrode active material slurry is coated on the base coating layer, and then dried in a vacuum drying oven at 90°C for 1 hour, thereby forming a negative electrode active material layer on the surface of the base coating layer. The single layer thickness of the negative electrode active material layer is 85μm.

[0025] Example 2 This embodiment provides a method for preparing a negative electrode sheet, including the following steps: S1-1. Preparation of the primer slurry: The first binder, the first conductive agent, and the sodium source material are mixed in a mass ratio of 1:7.5:2.5, and then an oil-based solvent is added to obtain the primer slurry. In the materials used above, the oil-based solvent is N-methylpyrrolidone, the first binder is PVDF, the first conductive agent is composed of multi-walled carbon nanotubes and acetylene black in a mass ratio of 1:67, and the sodium source material is Na2P. By mass percentage, the oil-based solvent accounts for 75% of the total mass of the primer slurry, and the multi-walled carbon nanotubes account for 1% of the total mass of the primer slurry.

[0026] S1-2. Preparation of the base coating: The above-mentioned base coating slurry is coated on an aluminum foil with a thickness of 12 μm, and then the base coating slurry is dried at a temperature of 140°C to form a base coating on the surface of the aluminum foil with a thickness of 3 μm.

[0027] S2-1. Preparation of negative electrode active material slurry: The negative electrode active material, the second binder, and the second conductive agent are mixed evenly in a mass ratio of 8:1:1 to obtain the negative electrode active material slurry. Among the materials used above, the negative electrode active material is KHC-1 (Guangdong Kaijin), the second binder is LA133, and the second conductive agent is Super P (Swiss Temir).

[0028] S2-2. Preparation of negative electrode active material layer: The above-mentioned negative electrode active material slurry is coated on the base coating layer, and then dried in a vacuum drying oven at 90°C for 1 hour, thereby forming a negative electrode active material layer on the surface of the base coating layer. The single layer thickness of the negative electrode active material layer is 80μm.

[0029] Example 3 This embodiment provides a method for preparing a negative electrode sheet, including the following steps: S1-1. Preparation of the primer slurry: The first binder, the first conductive agent, and the sodium source material are mixed in a mass ratio of 1:7.5:2.5, and then an oil-based solvent is added to obtain the primer slurry. In the materials used above, the oil-based solvent is N-methylpyrrolidone, the first binder is PVDF, the first conductive agent is composed of multi-walled carbon nanotubes and acetylene black in a mass ratio of 1:21.7, and the sodium source material is Na2P. By mass percentage, the oil-based solvent accounts for 75% of the total mass of the primer slurry, and the multi-walled carbon nanotubes account for 3% of the total mass of the primer slurry.

[0030] S1-2. Preparation of the base coating: The above-mentioned base coating slurry is coated on an aluminum foil with a thickness of 12 μm, and then the base coating slurry is dried at a temperature of 140°C to form a base coating on the surface of the aluminum foil with a thickness of 3 μm.

[0031] S2-1. Preparation of negative electrode active material slurry: The negative electrode active material, the second binder, and the second conductive agent are mixed evenly in a mass ratio of 8:1:1 to obtain the negative electrode active material slurry. Among the materials used above, the negative electrode active material is KHC-1 (Guangdong Kaijin), the second binder is LA133, and the second conductive agent is Super P (Swiss Temir).

[0032] S2-2. Preparation of negative electrode active material layer: The above-mentioned negative electrode active material slurry is coated on the base coating layer, and then dried in a vacuum drying oven at 90°C for 1 hour, thereby forming a negative electrode active material layer on the surface of the base coating layer. The single layer thickness of the negative electrode active material layer is 90μm.

[0033] Example 4 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that in the raw materials used to prepare the primer slurry, an equal mass of Na3P is used to replace Na2P in Example 1. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0034] Example 5 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of material constant, the mass ratio of the sodium source material to the first conductive agent is adjusted to 1:1. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0035] Example 6 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of material constant, the mass ratio of the sodium source material to the first conductive agent is adjusted to 1:2. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0036] Example 7 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of material constant, the mass ratio of the sodium source material to the first conductive agent is adjusted to 1:4. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0037] Example 8 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of material constant, the mass ratio of the sodium source material to the first conductive agent is adjusted to 1:5. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0038] Example 9 This embodiment prepares a negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that in the preparation of the primer slurry, an equal mass of acetylene black is used to replace multi-walled carbon nanotubes. Apart from the above differences, the materials, formulation ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0039] Example 10 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that in the process of preparing the base coating slurry, an equal mass of multi-walled carbon nanotubes is used to replace the acetylene black in Example 1. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0040] Example 11 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of binder, first conductive agent and sodium source material unchanged, the mass ratio of binder to the sum of first conductive agent and sodium source material is adjusted to 1:8. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0041] Example 12 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of binder, first conductive agent and sodium source material unchanged, the mass ratio of binder to the sum of first conductive agent and sodium source material is adjusted to 1:9. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0042] Example 13 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of binder, first conductive agent and sodium source material unchanged, the mass ratio of binder to the sum of first conductive agent and sodium source material is adjusted to 1:11. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0043] Example 14 This embodiment prepares the negative electrode sheet according to the preparation method provided in Example 1. The difference between this embodiment and Example 1 is that, in the process of preparing the base coating slurry, while keeping the total amount of binder, first conductive agent and sodium source material unchanged, the mass ratio of binder to the sum of first conductive agent and sodium source material is adjusted to 1:12. Apart from the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0044] Comparative Example 1 This comparative example prepares a negative electrode sheet according to the preparation method provided in Example 1. The difference between this comparative example and Example 1 is that in the preparation of the primer slurry, an equal mass of the first conductive agent is used to replace the sodium source material. Apart from the above differences, the materials, formulation ratios and preparation operations used in this comparative example are strictly consistent with those in Example 1.

[0045] Comparative Example 2 The negative electrode provided in this comparative example is aluminum foil.

[0046] Comparative Example 3 This comparative example provides a method for preparing a negative electrode sheet, including the following steps: S1-1. Preparation of primer slurry: The first binder and the first conductive agent are mixed at a mass ratio of 1:10 to obtain the primer slurry. In the materials used above, the solvent is N-methylpyrrolidone, the first binder is PVDF, and the first conductive agent is composed of multi-walled carbon nanotubes and acetylene black at a mass ratio of 1:33. By mass percentage, the oil-based solvent accounts for 75% of the total mass of the primer slurry, and the multi-walled carbon nanotubes account for 2% of the total mass of the primer slurry.

[0047] S1-2. Preparation of the base coating: The above-mentioned base coating slurry is coated on an aluminum foil with a thickness of 12 μm, and then the base coating slurry is dried at a temperature of 140°C to form a base coating on the surface of the aluminum foil with a thickness of 3 μm.

[0048] S2-1. Preparation of negative electrode active material slurry: The negative electrode active material, the second binder, the second conductive agent, and the sodium source material are mixed evenly in a mass ratio of 8:1:1:2.95 to obtain the negative electrode active material slurry. The negative electrode active material is KHC-1 (Guangdong Kaijin), the second binder is LA133, the second conductive agent is Super P (Swiss Temira), and the sodium source material is Na2P.

[0049] S2-2. Preparation of negative electrode active material layer: The above-mentioned negative electrode active material slurry is coated on the base coating layer, and then dried in a vacuum drying oven at 90°C for 1 hour, thereby forming a negative electrode active material layer on the surface of the base coating layer. The single layer thickness of the negative electrode active material layer is 85μm.

[0050] Preparation Example The button cell battery casing is of model CR2032, the separator is a 20μm separator, and the electrode is the negative electrode provided in Examples 1-14 and the negative electrode provided in Comparative Examples 1-3. In a glove box filled with argon gas, the button sodium-ion battery is prepared by assembling the battery casing, placing the negative electrode, adding electrolyte, placing the separator, adding electrolyte, placing the sodium sheet, placing the gasket, and then the battery casing.

[0051] Test case 1. Test subject: The button sodium-ion battery prepared in the preparation example is used as the test subject in this test example.

[0052] 2. Test items: (1) Initial charge and discharge performance test: The test subject was subjected to a 0.2C charge and discharge test using a button battery charge and discharge tester (Wuhan Landian, CT2001A), with a voltage range of 0.01-2.5V.

[0053] (2) Rate performance test: The button battery charge and discharge tester (Wuhan Landian, CT2001A) was used to conduct 1C and 3C charge and discharge tests on the test objects, with a voltage range of 0.01-2.5V.

[0054] 3. Test Results Table 1. Relevant performance test results of the test subjects

[0055] The relevant performance test results of the button sodium-ion batteries prepared in the preparation examples are shown in Table 1. The initial charge-discharge performance of the button sodium-ion batteries made from the negative electrode sheets provided in Examples 1 to 14 is generally better than that of Comparative Examples 1 to 3.

[0056] The difference between Comparative Example 1 and Examples 1-14 is that no sodium source material was added to the negative electrode sheet during its preparation. Test results show that the initial charge-discharge efficiency of the negative electrode sheets provided in Examples 1-14 is superior to that of Comparative Example 1. This is because, since no sodium source material was added to the undercoat layer of the negative electrode sheet in Comparative Example 1, the sodium ions consumed in forming the SEI film on the negative electrode surface during the initial charge-discharge process come from the positive electrode material. This reduces the amount of active sodium ions available for insertion / extraction, leading to a decrease in initial charge-discharge efficiency. Simultaneously, the irreversible loss of sodium ions in the sodium-ion battery during cycling is reduced, effectively improving the stability of the electrode structure, as evidenced by increased 1C and 3C capacity retention rates.

[0057] The difference between Comparative Example 2 and Examples 1-14 is that the negative electrode sheet provided in Comparative Example 2 is aluminum foil, without a base coating layer or a negative electrode active material layer. The test results show that the initial charge-discharge efficiency of the negative electrode sheets provided in Examples 1-14 is better than that of Comparative Example 2. This is because Comparative Example 2 only uses aluminum foil as the negative electrode, lacking a base coating layer and a negative electrode active material layer, thus failing to form a complete sodium-ion battery negative electrode structure. This negative electrode lacks both the active material required for sodium ion insertion / extraction and the sodium source material, resulting in a lower initial charge-discharge efficiency than Examples 1-14.

[0058] Compared to Example 1, the negative electrode sheet provided in Comparative Example 3 had sodium source material added to the negative electrode active material layer during the preparation process. The test results show that the initial charge-discharge efficiency, 1C capacity retention rate, and 3C capacity retention rate of the negative electrode sheet provided in Example 1 are all superior to those of Comparative Example 3. This is because Comparative Example 3 placed the sodium source material in the negative electrode active layer, causing the sodium source material to undergo side reactions and be lost before cycling, thus damaging the electrode's conductivity and ion transport network, resulting in a decrease in the initial charge-discharge efficiency and the 1C and 3C capacity retention rates.

[0059] Compared to Example 1, the difference in the composition of the negative electrode sheet provided in Example 4 is that the sodium source material used is Na3P. The test results show that the first charge / discharge efficiency, 1C capacity retention rate, and 3C capacity retention rate of the negative electrode sheet provided in Example 1 are all superior to those of Example 4. This is because, during the first charge / discharge of the battery, Na2P in the sodium source material decomposes. The decomposition products not only provide additional sodium ions but also form a dense and stable SEI film composed of inorganic components. This SEI film is less prone to rupture during battery cycling, reducing side reactions and lowering battery polarization. Furthermore, this SEI film has lower resistance to sodium ion transport, increasing the sodium ion transport rate, thereby further improving the battery's first charge / discharge efficiency and rate performance.

[0060] Compared with Example 1, the difference in the composition of the negative electrode sheets provided in Examples 5-8 is the mass ratio of sodium source material to conductive agent. The test results show that the initial charge / discharge efficiency, 1C capacity retention rate, and 3C capacity retention rate of the negative electrode sheets provided in Examples 1, 5, and 6 are all superior to those in Examples 7 and 8. This indicates that controlling the mass ratio of sodium source material to conductive agent within the range of 1:(1-5) can fully utilize the sodium replenishment function to improve the sodium ion transport rate, and the conductive agent forms a continuous and stable conductive network, promoting the uniformity of electron transport, thereby further improving the initial charge / discharge efficiency and rate performance of the battery.

[0061] Compared to Example 1, the difference in the composition of the negative electrode sheets provided in Examples 9 and 10 lies in the conductive agent used during the preparation of the base coating slurry. The test results show that the initial charge-discharge efficiency, 1C capacity retention rate, and 3C capacity retention rate of the negative electrode sheet provided in Example 1 are all superior to those in Examples 9 and 10. This is because Example 1 uses a combination of carbon nanotubes and carbon black. During battery charge-discharge, the unique tubular hollow structure and surface defects of carbon nanotubes can serve as a rapid diffusion path for sodium ions, increasing the sodium ion transport rate and thus improving the battery's rate performance. Furthermore, the sodium source material can form chemical bonds with the carbon atoms at the defect sites of the carbon nanotubes. These chemical bonds allow the sodium source material to adhere more stably to the surface of the conductive agent, maintaining the stability of the electrode structure and further improving the battery's cycle stability. Carbon black can optimize the slurry flowability to meet the requirements of the coating process.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A negative electrode sheet, characterized in that: It includes a current collector, a base coating, and a negative electrode active material layer arranged along its thickness direction; The base coating includes a sodium source material and a conductive agent.

2. The negative electrode sheet as described in claim 1, characterized in that: The sodium source material includes Na2P.

3. The negative electrode sheet as described in claim 2, characterized in that: The mass ratio of the sodium source material to the conductive agent is 1:(1~5).

4. The negative electrode sheet as described in claim 1, characterized in that: The conductive agent includes at least one of carbon nanotubes and carbon black.

5. The negative electrode sheet as described in claim 4, characterized in that: The conductive agent includes carbon nanotubes; the carbon nanotubes include multi-walled carbon nanotubes; the content of the multi-walled carbon nanotubes in the base coating is 1% to 3% by mass percentage.

6. The negative electrode sheet as described in claim 4, characterized in that: The conductive agent includes carbon nanotubes and carbon black; the carbon nanotubes include multi-walled carbon nanotubes; the carbon black includes acetylene black; and the mass ratio of multi-walled carbon nanotubes to acetylene black is 1:(3~67).

7. A method for preparing a negative electrode sheet as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A primer slurry is coated onto the current collector, and the primer slurry is dried to obtain a base layer; then an active material slurry is coated onto the base layer, and the active material slurry is dried to obtain a negative electrode sheet; wherein, the primer slurry includes an oil-based solvent and the sodium source material.

8. The preparation method according to claim 7, characterized in that: The sodium source material accounts for 20% to 25% of the total mass of the primer slurry, calculated as a percentage by mass.

9. The preparation method according to claim 7, characterized in that: The oil-based solvent accounts for 70% to 80% of the total mass of the primer slurry, calculated by mass percentage.

10. A sodium-ion battery, comprising the negative electrode sheet according to any one of claims 1 to 6 or the negative electrode sheet prepared by the preparation method according to any one of claims 7 to 9.

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