A sodium ion battery and a preparation method thereof

Abstract

The present invention relates to a sodium-ion battery and a method for preparing the same. The sodium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and an aluminum shell. The positive electrode sheet's positive electrode slurry comprises a positive electrode active material, a conductive agent, a positive electrode binder, and a first additive. The negative electrode sheet's negative electrode slurry comprises a negative electrode active material, a conductive agent, a negative electrode binder, and a second additive. The first additive is at least one of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid, and the second additive is at least one of graphene and 1,3-butanediol. By adding different additives to the positive and negative electrode materials, the sodium-ion battery improves the slurry coating effect and enhances the subsequent processing performance and electrical performance of the electrode sheets.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium batteries, and in particular relates to a sodium ion battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, serving as the energy hub between energy and consumer devices, have been widely used in mobile phones, computers, electric vehicles, and other fields. However, lithium resources present several challenges: first, their total distribution is limited, with an abundance of only 0.0065% in the Earth's crust; second, their spatial distribution is uneven, with lithium deposits primarily concentrated in Australia and South America. Consequently, limited reserves and high costs have limited the widespread adoption of lithium-ion batteries.

[0003] Sodium resources are abundant on Earth, with an elemental content of approximately 23,000 ppm, and are distributed globally, regardless of geographical location. Therefore, sodium-ion batteries offer significant resource advantages over lithium-ion batteries. In the past two years, the industrialization of sodium-ion batteries has rapidly advanced. Compared to widely used lithium-ion batteries, sodium-ion batteries offer significant advantages, including low raw material costs, high thermal stability, and a wide operating temperature range. Their similar operating principles make them widely recognized as ideal secondary batteries for applications such as two-wheeled vehicles, low-speed electric vehicles, communications, and household energy storage.

[0004] Sodium-ion batteries are mainly divided into three structures: cylindrical sodium-ion batteries, soft-pack sodium-ion batteries, and square aluminum-shell sodium-ion batteries. Currently, the capacity of a single soft-pack sodium-ion battery or cylindrical sodium-ion battery is low. If these sodium-ion batteries are used in two-wheeled vehicles, energy storage systems, and low-speed electric vehicles, a large number of batteries need to be connected in series and parallel. This not only makes the battery pack assembly process more difficult, but also greatly increases the cost of the battery pack management system and reduces the safety of the battery pack. Square aluminum-shell sodium-ion batteries have greater capacity and energy density, so the development and optimization of the process of square aluminum-shell sodium-ion batteries is of great significance for their commercial application. However, existing square aluminum-shell sodium-ion batteries still have problems such as poor dispersion of negative and positive electrode slurries and poor stability, which seriously affect the slurry coating effect and the subsequent processing performance of the electrode, resulting in unsatisfactory battery electrical performance tests. Summary of the Invention

[0005] In order to overcome the above shortcomings, the purpose of the present invention is to provide a sodium ion battery, which improves the coating effect of the slurry and enhances the subsequent processing performance and electrical performance of the electrode by adding different additives to the positive electrode material and the negative electrode material respectively.

[0006] The technical solution adopted by the present invention to solve the above problems is: a sodium ion battery, including a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and an aluminum shell, the positive electrode slurry of the positive electrode sheet includes a positive electrode active material, a conductive agent, a positive electrode binder, and an additive one, and the additive one is at least one of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid; the negative electrode slurry of the negative electrode sheet includes a negative electrode active material, a conductive agent, a negative electrode binder, and an additive two, and the additive two is at least one of graphene and 1,3-butanediol.

[0007] The electrolyte includes a sodium salt, a solvent and an additive, wherein the sodium salt is one or more of sodium hexafluorophosphate NaPF6, sodium perchlorate NaClO4, sodium hexafluoroborate NaBF6, and sodium bis(trifluoromethylsulfonyl)imide NaTFSI; the solvent is one or more of ethylene carbonate EC, propylene carbonate PC, dimethyl carbonate DMC, ethyl methyl carbonate EMC, and diethyl carbonate DEC; and the additive is one or more of fluoroethylene carbonate FEC, 1,3-propylene sultone PST, propane sultone PS, and vinyl sulfate DTD.

[0008] Preferably, the mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder in the positive electrode slurry is 93.6-95.9:1.6-3.3:0.8-3.3, and the amount of the additive 1 added to the positive electrode slurry is 0.1%-0.5% of the total mass of the positive electrode slurry.

[0009] Preferably, the negative electrode slurry of the negative electrode sheet includes the negative electrode active material, the conductive agent, and the negative electrode binder in a mass ratio of 93.6-95.8:0.8-2.3:2.1-4.2, and the amount of the additive 2 added to the negative electrode slurry is 0.1%-0.5% of the total mass of the negative electrode slurry.

[0010] Preferably, the positive electrode active material is a layered oxide positive electrode material, and the negative electrode active material is hard carbon.

[0011] Preferably, the conductive agent is one or more of acetylene black, conductive carbon black, carbon fiber VGCF, carbon nanotube CNT, and Ketjen black.

[0012] Preferably, the positive electrode binder is one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), polybutyl acrylate (PBA), and polyacrylonitrile (PA).

[0013] Preferably, the negative electrode binder is one or more of styrene-butadiene rubber SBR / sodium carboxymethyl cellulose CMC, polyacrylic acid PAA, and LA132 / LA13 aqueous binder.

[0014] Another object of the present invention is to provide a method for preparing the above-mentioned sodium ion battery, comprising the following steps:

[0015] (1) Preparation of sodium ion battery positive electrode sheet: coating the positive electrode slurry on the positive electrode current collector, drying and rolling to form a positive electrode sheet;

[0016] (2) Preparation of sodium ion battery negative electrode sheet: coating the negative electrode slurry on the negative electrode current collector, drying and rolling to form the negative electrode sheet;

[0017] (3) Pole sheet die-cutting, slitting and winding: The pole sheet is cut into positive and negative tabs by laser die-cutting, and a separator is used to separate the single positive and negative electrode sheets and wind them into a roll core;

[0018] (4) Hot and cold pressing of core: hot pressing and cold pressing of the wound core in sequence;

[0019] (5) Cover plate welding: ultrasonically weld the positive electrode tab of the core package to the positive electrode connecting piece, ultrasonically weld the negative electrode tab to the negative electrode connecting piece, laser weld the positive electrode connecting piece to the positive electrode column of the cover plate, and laser weld the negative electrode connecting piece to the negative electrode column of the cover plate;

[0020] (6) Battery assembly: Fix the core pack and cover plate together to obtain a shaped core pack;

[0021] (7) Shelling: The shaped core package is encapsulated in the aluminum shell, and the cover is laser welded to the upper edge of the aluminum shell;

[0022] (8) Packaging: Baking, injecting electrolyte, and then undergoing chemical formation to obtain a sodium ion battery.

[0023] Preferably, in step (1), the positive electrode sheet (excluding the current collector) is coated with a double-sided density of 18-36 mg / cm 2 , compacted density is 3.0~3.3g / cm 3 .

[0024] Preferably, in step (2), the negative electrode sheet (excluding the current collector) is coated with a double-sided density of 6.8 to 13.8 mg / cm 2 , compacted density is 0.98~1.1g / cm 3 .

[0025] Preferably, the positive electrode current collector is one of aluminum foil, aluminum mesh, and carbon-coated aluminum foil.

[0026] Preferably, the negative electrode current collector is one of aluminum foil, aluminum mesh, carbon-coated aluminum foil, copper foil, copper mesh, and carbon-coated copper foil.

[0027] Preferably, in step (4), the hot pressing temperature is 90-100°C, the hot pressing time is 60 seconds, and the hot pressing pressure is 400-500 kgf; the cold pressing temperature is 10-15°C, the cold pressing time is 60 seconds, and the cold pressing pressure is 400-500 kgf. Preferably, in step (8), baking is carried out under vacuum conditions, the baking temperature is 95°C, the baking time is greater than 24 hours, and the moisture content after baking is less than 300 ppm.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] The present invention adds at least one of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid as an additive to the positive electrode slurry, effectively improving the coating effect of the positive electrode slurry, thereby improving the subsequent processing performance and electrical properties of the positive electrode sheet; and adds at least one of graphene and 1,3-butanediol as an additive to the negative electrode slurry, effectively improving the coating effect of the slurry, improving the expansion of the negative electrode sheet, and increasing the liquid absorption capacity of the negative electrode sheet, further improving the subsequent processing performance and electrical properties of the negative electrode sheet. Implementation Method

[0030] The present invention is described in further detail below with reference to the examples. Example 1

[0031] (1) Preparation of positive electrode sheets for sodium ion batteries: The positive electrode active material sodium nickel iron manganese oxide, the conductive agent (conductive carbon black and carbon nanotubes CNT with a mass ratio of 2:1), and the binder polyvinylidene fluoride PVDF are uniformly dispersed in the solvent NMP at a mass ratio of 95.6:2.3:2.1, and additive 1 (polyvinyl pyrrolidone, itaconic acid, and ascorbic acid are dissolved in the solvent NMP at a mass ratio of 2:1:1, with a solid content of 20%) is added, wherein the total mass of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid is 0.1% of the total mass of the positive electrode slurry. After thorough mixing, a positive electrode slurry is obtained, and the solid content of the positive electrode slurry is 60%; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet (excluding the current collector) is coated with a double-sided surface density of 21.8 mg / cm 2 After drying, it is rolled to form a positive electrode sheet with a compaction density of 3.0g / cm 3 .

[0032] (2) Preparation of negative electrode sheets for sodium ion batteries: The negative electrode active material hard carbon, conductive agent conductive carbon black, and binder (styrene-butadiene rubber SBR and sodium carboxymethyl cellulose CMC with a mass ratio of 2:1) are uniformly dispersed in solvent water at a mass ratio of 95:2:3, and additive 2 (graphene and 1,3-butanediol are dissolved in solvent deionized water at a mass ratio of 1:1, with a solid content of 30%) is added, wherein the total mass of graphene and 1,3-butanediol is 0.1% of the total mass of the negative electrode slurry. After fully mixing, the negative electrode slurry is obtained. The negative electrode slurry is coated on the negative electrode current collector aluminum foil. The negative electrode sheet (excluding the current collector) is coated with a double-sided surface density of 8.8 mg / cm 2 After drying, the negative electrode is rolled to form a compacted density of 0.98g / cm 3 .

[0033] (3) Pole sheet die-cutting and winding: The positive and negative pole ears are cut out of the pole sheet by laser die-cutting, and the positive and negative pole sheets are separated by a diaphragm and wound into a roll core.

[0034] (4) Hot and cold pressing of the core: The wound core is hot pressed by a hot press, with the temperature controlled at 95°C, the time controlled at 60s, and the core pressure of 400~500kgf; then cold pressed by a cold press, with the temperature controlled at 15°C, the time controlled at 60s, and the core pressure of 400~500kgf. (5) Cover plate welding: The positive electrode tab of the core package is ultrasonically welded to the positive electrode connecting piece, the negative electrode tab is ultrasonically welded to the negative electrode connecting piece, the positive electrode connecting piece is laser welded to the positive electrode column of the cover plate, and the negative electrode connecting piece is laser welded to the negative electrode column of the cover plate.

[0035] (6) Battery assembly: Use Mylar film to fix the core pack and cover together.

[0036] (7) Shelling: The shaped core package is encapsulated in the aluminum shell, and the cover is laser welded to the upper edge of the aluminum shell.

[0037] (8) Liquid filling and chemical composition: Bake at 95℃ under vacuum conditions for 24h, control the moisture content below 300ppm, then inject electrolyte, perform formation and high temperature aging, and laser weld the sealing nails to obtain a square sodium ion battery. The electrolyte sodium salt of the electrolyte is sodium hexafluorophosphate (NaPF6) with a concentration of 1.1mol / L; the solvent of the electrolyte is propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), mixed in a volume ratio of 2:2:1; 1.1% (based on the total mass of the electrolyte) of fluoroethylene carbonate FEC, 0.9% (based on the total mass of the electrolyte) of 1,3-propylene sultone PST, and 1% (based on the total mass of the electrolyte) of propane sultone PS are added to the electrolyte. The density of the electrolyte is 1.18g / cm 3 , the battery filling coefficient is 6.6g / Ah.

[0038] Ten batteries prepared in Example 1 were used for capacity separation at a rate of 0.33C. The charge and discharge cut-off voltage was 2.0-4.0V, the battery discharge capacity was above 25Ah, and the internal resistance was controlled below 1mΩ. The specific data are shown in Table 1.

[0039] Table 1

[0040]

[0041] Comparative Example 1

[0042] The only difference from Example 1 is that additive 1 is not added.

[0043] Comparative Example 2

[0044] The only difference from Example 1 is that additive 2 is not added.

[0045] The batteries prepared in Example 1 and Comparative Examples 1-2 were subjected to capacity division at a rate of 0.33C. The charge and discharge cut-off voltage was 2.0-4.0V, the battery discharge capacity was above 25Ah, and the internal resistance was controlled below 1mΩ. The specific data are shown in Table 2:

[0046] Table 2

[0047] Example 2

[0048] (1) Preparation of positive electrode sheets for sodium ion batteries: The positive electrode active material sodium nickel iron manganese oxide, the conductive agent (conductive carbon black and carbon nanotubes CNT with a mass ratio of 2:1), and the binder polyvinylidene fluoride PVDF are uniformly dispersed in the solvent NMP at a mass ratio of 95.3:2.5:2.2, and the additive 1 (polyvinyl pyrrolidone, itaconic acid, and ascorbic acid are dissolved in the solvent NMP at a mass ratio of 2:1:1, with a solid content of 20%) is added, wherein the total mass of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid is 0.3% of the total mass of the positive electrode slurry. After thorough mixing, the positive electrode slurry is obtained; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet (excluding the current collector) is coated with a double-sided surface density of 24.8 mg / cm 2 After drying, the positive electrode is rolled and formed, with a compaction density of 3.1g / cm 3 .

[0049] (2) Preparation of negative electrode sheets for sodium ion batteries: The negative electrode active material hard carbon, conductive agent conductive carbon black, and binder (styrene-butadiene rubber SBR / sodium carboxymethyl cellulose CMC) are uniformly dispersed in solvent water at a mass ratio of 94.7:2.1:3.2, and additive 2 (graphene and 1,3-butanediol are dissolved in solvent deionized water at a mass ratio of 1:1, with a solid content of 30%) is added. The total mass of graphene and 1,3-butanediol is 0.3% of the total mass of the negative electrode slurry. After fully mixing, the negative electrode slurry is obtained. The negative electrode slurry is coated on the negative electrode current collector aluminum foil. The negative electrode sheet (excluding the current collector) is coated with a double-sided surface density of 9.8 mg / cm 2 After drying, the negative electrode is rolled to form a compacted density of 0.99g / cm 3 .

[0050] (3) Pole sheet die-cutting and winding: The positive and negative pole ears are cut out of the pole sheet by laser die-cutting, and the positive and negative pole sheets are separated by a diaphragm and wound into a roll core.

[0051] (4) Hot and cold pressing of the core: The wound core is hot pressed by a hot press, with the temperature controlled at 95°C, the time controlled at 60s, and the core pressure of 3000~3500kgf; then cold pressed by a cold press, with the temperature controlled at 15°C, the time controlled at 60s, and the core pressure of 3000~3500kgf. (5) Cover plate welding: The positive electrode tab of the core package is ultrasonically welded to the positive electrode connecting piece, the negative electrode tab is ultrasonically welded to the negative electrode connecting piece, the positive electrode connecting piece is laser welded to the positive electrode column of the cover plate, and the negative electrode connecting piece is laser welded to the negative electrode column of the cover plate.

[0052] (6) Battery assembly: Use Mylar film to fix the core pack and cover together.

[0053] (7) Shelling: The shaped core package is encapsulated in the aluminum shell, and the cover is laser welded to the upper edge of the aluminum shell.

[0054] (8) Liquid filling and chemical composition: Bake at 95℃ under vacuum conditions for 48h, control the moisture content below 300ppm, then inject electrolyte, perform formation and high temperature aging, and laser weld the sealing nails to obtain a square sodium ion battery. The electrolyte sodium salt of the electrolyte is sodium hexafluorophosphate (NaPF6) with a concentration of 1.1mol / L; the solvent of the electrolyte is propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), mixed in a volume ratio of 2:2:1; 1.1% (based on the total mass of the electrolyte) of fluoroethylene carbonate FEC, 0.9% (based on the total mass of the electrolyte) of 1,3-propylene sultone PST, and 1% (based on the total mass of the electrolyte) of propane sultone PS are added to the electrolyte. The density of the electrolyte is 1.18g / cm 3 , the battery filling coefficient is 5.8g / Ah.

[0055] Ten batteries prepared in Example 2 were used for capacity separation at a rate of 0.33C. The charge and discharge cut-off voltage was 2.0-4.0V, the battery discharge capacity was above 100Ah, and the internal resistance was controlled below 1mΩ. The specific data are shown in Table 3.

[0056] Table 3

[0057] Example 3

[0058] (1) Preparation of positive electrode sheets for sodium ion batteries: The positive electrode active material sodium nickel iron manganese oxide, the conductive agent (conductive carbon black and carbon nanotubes CNT with a mass ratio of 2:1), and the binder polyvinylidene fluoride PVDF are uniformly dispersed in the solvent NMP at a mass ratio of 94.8:2.7:2.5, and additive 1 (polyvinyl pyrrolidone, itaconic acid, and ascorbic acid are dissolved in the solvent NMP at a mass ratio of 2:1:1, with a solid content of 20%) is added, wherein the total mass of polyvinyl pyrrolidone, itaconic acid, and ascorbic acid is 0.5% of the total mass of the positive electrode slurry. After thorough mixing, the positive electrode slurry is obtained; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet (excluding the current collector) is coated with a double-sided surface density of 30.6 mg / cm 2 After drying, it is rolled to form a positive electrode sheet with a compaction density of 3.2g / cm 3 .

[0059] (2) Preparation of negative electrode sheets for sodium ion batteries: The negative electrode active material hard carbon, conductive agent conductive carbon black, and binder (styrene-butadiene rubber SBR / sodium carboxymethyl cellulose CMC) are uniformly dispersed in solvent water at a mass ratio of 94.5:2.3:3.2, and additive 2 (graphene and 1,3-butanediol are dissolved in solvent deionized water at a mass ratio of 1:1, with a solid content of 30%) is added, wherein the total mass of graphene and 1,3-butanediol is 0.5% of the total mass of the negative electrode slurry. After fully mixing, the negative electrode slurry is obtained. The negative electrode slurry is coated on the negative electrode current collector aluminum foil. The negative electrode sheet (excluding the current collector) is coated with a double-sided surface density of 12.0 mg / cm 2 After drying, the negative electrode is rolled to form a compacted density of 1.03g / cm 3 .

[0060] (3) Pole sheet die-cutting and winding: The positive and negative pole ears are cut out of the pole sheet by laser die-cutting, and the positive and negative pole sheets are separated by a diaphragm and wound into a roll core.

[0061] (4) Hot and cold pressing of the core: The wound core is hot pressed by a hot press, with the temperature controlled at 95°C, the time controlled at 60s, and the core pressure at 3500~4000kgf; then cold pressed by a cold press, with the temperature controlled at 15°C, the time controlled at 60s, and the core pressure at 3500~4000kgf. (5) Cover plate welding: The positive electrode tab of the core package is ultrasonically welded to the positive electrode connecting piece, the negative electrode tab is ultrasonically welded to the negative electrode connecting piece, the positive electrode connecting piece is laser welded to the positive electrode column of the cover plate, and the negative electrode connecting piece is laser welded to the negative electrode column of the cover plate.

[0062] (6) Battery assembly: Use Mylar film to fix the core pack and cover together.

[0063] (7) Shelling: The shaped core package is encapsulated in the aluminum shell, and the cover is laser welded to the upper edge of the aluminum shell.

[0064] (8) Liquid filling and chemical composition: Bake at 95℃ under vacuum conditions for 48h, control the moisture content below 300ppm, then inject electrolyte, perform formation and high temperature aging, and laser weld the sealing nails to obtain a square sodium ion battery. The electrolyte sodium salt of the electrolyte is sodium hexafluorophosphate (NaPF6) with a concentration of 1.1mol / L; the solvent of the electrolyte is propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), mixed in a volume ratio of 2:2:1; 1.1% (based on the total mass of the electrolyte) of fluoroethylene carbonate FEC, 0.9% (based on the total mass of the electrolyte) of 1,3-propylene sultone PST, and 1% of propane sultone PS are added to the electrolyte. The density of the electrolyte is 1.18g / cm 3 , the battery filling coefficient is 5.3g / Ah.

[0065] Ten batteries prepared in Example 3 were used for capacity separation at a rate of 0.33C. The charge and discharge cut-off voltage was 2.0-4.0V, the battery discharge capacity was above 240Ah, and the internal resistance was controlled below 1mΩ. The specific data are shown in Table 4.

[0066] Table 4

[0067]

[0068] In addition to the above embodiments, the present invention also includes other implementation methods. Any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of protection of the claims of the present invention.

Claims

1. A sodium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and an aluminum shell, characterized in that: The positive electrode slurry of the positive electrode sheet includes a positive electrode active material, a conductive agent, a positive electrode binder, and an additive 1; the negative electrode slurry of the negative electrode sheet includes a negative electrode active material, a conductive agent, a negative electrode binder, and an additive 2; Polyvinyl pyrrolidone, itaconic acid and ascorbic acid in a mass ratio of 2:1:1 are dissolved in a solvent NMP to obtain an additive 1, wherein the solid content of the additive 1 is 20%; Graphene and 1,3-butanediol in a mass ratio of 1:1 are dissolved in deionized water as a solvent to obtain additive 2, and the solid content of additive 2 is 30%.

2. The sodium ion battery according to claim 1, wherein: The mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder in the positive electrode slurry is 93.6-95.9:1.6-3.3:0.8-3.3, and the amount of the additive 1 added to the positive electrode slurry is 0.1%-0.5% of the total mass of the positive electrode slurry.

3. The sodium ion battery according to claim 1, wherein: The negative electrode slurry of the negative electrode sheet includes a negative electrode active material, a conductive agent, and a negative electrode binder in a mass ratio of 93.6-95.8:0.8-2.3:2.1-4.2, and the amount of the additive 2 added to the negative electrode slurry is 0.1%-0.5% of the total mass of the negative electrode slurry.

4. The sodium ion battery according to claim 1, wherein: The positive electrode active material is a layered oxide positive electrode material, and the negative electrode active material is hard carbon.

5. The sodium ion battery according to claim 1, wherein: The conductive agent is one or more of acetylene black, conductive carbon black, carbon fiber VGCF, carbon nanotube CNT, and Ketjen black.

6. The sodium ion battery according to claim 1, wherein: The positive electrode binder is one or more of polyvinylidene fluoride PVDF, polyacrylic acid PAA, polytetrafluoroethylene PTFE, polybutyl acrylate PBA, and polyacrylonitrile PA.

7. The sodium ion battery according to claim 1, wherein: The negative electrode binder is one or more of styrene-butadiene rubber (SBR) / sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and LA132 / LA13 aqueous binder.

8. A method for preparing a sodium ion battery according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Preparation of sodium ion battery positive electrode sheet: coating the positive electrode slurry on the positive electrode current collector, drying and rolling to form a positive electrode sheet; (2) Preparation of sodium ion battery negative electrode sheet: coating the negative electrode slurry on the negative electrode current collector, drying and rolling to form the negative electrode sheet; (3) Pole sheet die-cutting, slitting and winding: The pole sheet is cut into positive and negative tabs by laser die-cutting, and a separator is used to separate the single positive and negative electrode sheets and wind them into a roll core; (4) Hot and cold pressing of the core: hot pressing and cold pressing of the wound core in sequence; (5) Cover plate welding: ultrasonically weld the positive electrode tab of the core package to the positive electrode connecting piece, ultrasonically weld the negative electrode tab to the negative electrode connecting piece, laser weld the positive electrode connecting piece to the positive electrode column of the cover plate, and laser weld the negative electrode connecting piece to the negative electrode column of the cover plate; (6) Battery assembly: Fix the core pack and cover plate together to obtain a shaped core pack; (7) Shelling: The shaped core package is encapsulated in the aluminum shell, and the cover is laser welded to the upper mouth of the aluminum shell; (8) Packaging: Baking, injecting electrolyte, and then undergoing chemical formation to obtain a sodium ion battery.

9. The method for preparing a sodium ion battery according to claim 8, wherein: In step (4), the hot pressing temperature is 90-100°C, the hot pressing time is 60s, and the hot pressing pressure is 400-500kgf; the cold pressing temperature is 10-15°C, the cold pressing time is 60s, and the cold pressing pressure is 400-500kgf.

10. The method for preparing a sodium ion battery according to claim 8, wherein: In step (8), the baking is carried out under vacuum conditions, the baking temperature is 95° C., the baking time is greater than 24 h, and the moisture content after baking is less than 300 ppm.

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