Preparation method of sodium-ion battery negative electrode plate with composite coating and application of sodium-ion battery negative electrode plate

Abstract

The invention provides a preparation method of a sodium-lithium ion battery negative plate with a composite coating and the negative plate, and belongs to the field of lithium batteries. The preparation method is as follows; mixing hard carbon, a conductive agent, an oil-based binder and an organic solvent to prepare oily slurry, and then coating the oily slurry on a current collector for drying to form an oil-based active material layer; the method comprises the following steps: mixing hard carbon, a conductive agent, a water-based binder and deionized water to prepare water-based slurry, coating the water-based slurry on a current collector coated with an oil-based layer, and drying to form a sodium-ion battery negative electrode plate, so that the oil-based layer and the water-based layer are combined, the good flexibility and cohesiveness of the oil-based layer are fully exerted, and the service life of the sodium-ion battery negative electrode plate is prolonged. And the water system layer is environment-friendly and low in cost, so that the overall performance of the pole piece is improved. The oil system layer can enhance the bonding strength between the electrode material and the current collector and greatly reduce the falling of the active substance in the charging and discharging process; and the water system layer provides a good channel for sodium ion transmission, so that the rate capability of the battery is improved, and the service life of the battery is prolonged.

Description

TECHNICAL FIELD

[0001] The application provides a method for preparing a sodium lithium ion battery negative sheet with a composite coating and a negative sheet thereof, and belongs to the field of lithium batteries. BACKGROUND

[0002] With the growing demand for clean energy and sustainable energy storage solutions worldwide, the development of battery technology has become a key area. Lithium ion batteries have made significant progress in the past few decades and are widely used in mobile electronic devices, electric vehicles, and energy storage systems. However, the limited availability and uneven distribution of lithium resources, as well as its rising cost, have prompted people to seek alternative battery technologies. Sodium ion batteries, due to their abundant sodium resources, low cost, and similar electrochemical principles to lithium ion batteries, have become one of the most promising next-generation battery technologies, showing broad application prospects in large-scale energy storage, low-speed electric vehicles, and other fields.

[0003] Traditional sodium battery negative sheets have certain limitations in terms of cycle stability, rate performance, and energy density. For example, single oil-based sheets have good flexibility and adhesion, but the use of organic solvents in the preparation process poses environmental pollution and safety hazards, and the cost is relatively high; while single water-based sheets are environmentally friendly and low-cost, but lack in adhesion strength and certain performance of the electrode material. Therefore, it is of great practical significance to develop a sodium battery negative sheet with excellent comprehensive performance. SUMMARY

[0004] To solve the above problems, the application provides a method for preparing a sodium ion battery negative sheet with a composite coating and a negative sheet thereof, which combines an oil-based layer and a water-based layer to fully utilize the good flexibility and adhesion of the oil-based layer, and the environmental friendliness and low cost of the water-based layer, thereby improving the overall performance of the sheet.

[0005] To achieve the above-mentioned purpose, the method for preparing a sodium ion battery negative sheet with a composite coating, the sodium battery negative sheet includes a current collector, and an oil-based layer and a water-based layer arranged on the surface of the current collector in sequence; wherein the oil-based layer is formed by coating and drying an oil-based slurry, the oil-based slurry includes hard carbon, a conductive agent and an oil-based binder, the water-based layer is formed by coating and drying a water-based slurry, and the water-based slurry includes hard carbon, a conductive agent and a water-based binder.

[0006] According to the method for preparing a sodium ion battery negative sheet with a composite coating, the mass ratio of hard carbon, conductive agent and oil-based binder in the oil-based slurry is (93.5-94.8%):(1.7-2.3%):(3.5-4.3%), and the hard carbon, conductive agent and oil-based binder are added to an organic solvent and stirred at high speed in a blender to form.

[0007] According to the method for preparing a composite-coated sodium-ion battery negative electrode sheet, the solid content in the oil-based slurry is 48.3%-50.7%.

[0008] According to the method for preparing a sodium ion battery negative electrode sheet with a composite coating, the mass ratio of the components in the aqueous slurry is hard carbon: conductive agent: aqueous binder = (94.1-95.0%): (1.7-2.3%): (3.3-3.6%). The hard carbon, conductive agent and aqueous binder are added to deionized water and stirred at high speed in a blender to prepare an aqueous slurry.

[0009] According to the method for preparing a composite-coated sodium-ion battery negative electrode sheet, the solid content of the aqueous slurry is 43.4%-45.7%.

[0010] According to the method for preparing a negative electrode sheet for a sodium ion battery with a composite coating, the thickness of the oil-based layer after drying is 5-8 μm.

[0011] According to the method for preparing a composite-coated sodium-ion battery negative electrode sheet, the conductive agent is acetylene black or carbon black, or a combination of the two.

[0012] According to the method for preparing a composite-coated sodium-ion battery negative electrode sheet, the oil-based binder is polyvinylidene fluoride with a molecular weight of 700,000-1.2 million.

[0013] According to the method for preparing a composite-coated sodium-ion battery negative electrode sheet, the aqueous binder is a mixture of a thickener and a binder, the thickener is one or both of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose, the binder is styrene-butadiene rubber, and the weight ratio of the thickener to the binder is 1:(1.35-1.6).

[0014] Comprehensive Performance Improvement: By combining an oil-based layer with an aqueous layer, the oil-based layer's excellent flexibility and adhesion, along with the aqueous layer's environmentally friendly and low-cost advantages, enhances the electrode's overall performance. The oil-based layer strengthens the bond between the electrode material and the current collector, reducing the shedding of active material during charge and discharge. The aqueous layer provides a good channel for sodium ion transport, helping to improve the battery's rate performance.

[0015] Cost reduction and environmental protection: The introduction of the aqueous layer reduces the use of organic solvents, reduces production costs, and reduces pollution to the environment, which is in line with the development concept of green chemistry.

[0016] Improved Cycling Stability and Energy Density: Experiments have shown that sodium-ion batteries assembled using the sodium battery negative electrode sheet prepared in this invention exhibit significant improvements in both cycling stability and energy density. In charge-discharge cycle tests conducted at a current density of 1C, the capacity retention rate reached over 95% after 1,000 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : The present invention is coated after the pole piece structure.

[0018] Figure 2 : Performance of sodium-ion batteries at different rates.

[0019] Figure 3 : 1C charge and discharge cycle life of sodium ion batteries. DETAILED DESCRIPTION

[0020] The content of the present invention is described below with specific content: The present invention discloses a method for preparing a sodium ion battery negative electrode sheet with a composite coating. The sodium battery negative electrode sheet includes a current collector, and an oil-based layer and a water-based layer sequentially arranged on the surface of the current collector. The oil-based layer is formed by coating and drying an oil-based slurry. The oil-based slurry includes hard carbon, a conductive agent, and an oil-based binder. The mass ratio of hard carbon: conductive agent: oil-based binder is (93.5-94.8%): (1.7-2.3%): (3.5-4.3%). The solid content of the oil-based slurry is 48.3%-50.7%.

[0021] The aqueous layer is formed by coating and drying an aqueous slurry, which includes hard carbon, a conductive agent and an aqueous binder; the mass ratio is hard carbon: conductive agent: aqueous binder = (94.1-95.0%): (1.7-2.3%): (3.3-3.6%), and the solid content of the aqueous slurry is 43.4%-45.7%.

[0022] The conductive agent is either acetylene black or carbon black, or a combination of both. The oil-based binder is polyvinylidene fluoride with a molecular weight of 700,000-1.2 million. The aqueous binder is a mixture of a thickener and a binder, with the thickener being either or both sodium carboxymethyl cellulose and lithium carboxymethyl cellulose. The binder is styrene-butadiene rubber, and the weight ratio of thickener to binder is 1:(1.35-1.6).

[0023] The preparation steps are as follows: (1) Preparation of oily slurry: Mix hard carbon, conductive agent, and oily binder evenly, add them into organic solvent, and stir them at high speed in a blender to prepare oily slurry; apply the oily slurry on the current collector, bake and dry the oily layer to a thickness of 5-8 μm. A pole piece forming an oil-based active material layer; (2) Preparation of aqueous slurry: Mix hard carbon, conductive agent, and aqueous binder evenly, add to deionized water, and stir at high speed in a blender to prepare aqueous slurry; (3) The aqueous slurry is coated on the electrode of the oil-containing active material layer and baked to form the negative electrode of the sodium ion battery.

[0024] The prepared composite coating electrode is prepared into a sodium ion battery through rolling, winding and assembly steps.

[0025] The following specific implementation cases describe the invention in detail, and the present invention does not limit the implementation parameters of the embodiments. Example 1

[0026] (1) 1896 g of hard carbon, 34 g of conductive agent and 70 g of polyvinylidene fluoride were mixed evenly. The conductive agent was a mixture of acetylene black and carbon black. The mass addition ratio was 1:1. The mixture was added to 1960 g of organic solvent and mixed evenly to prepare an oily slurry. (2) The oily slurry is evenly coated on the current collector, baked to prepare the negative electrode sheet of the sodium ion battery, and the peel strength of the negative electrode sheet is tested; (3) The negative electrode sheet is prepared into a sodium ion battery through processes such as rolling, winding, and assembly; (4) Test the different rate performance and 1C charge-discharge cycle life of sodium-ion batteries; Example 2

[0027] (1) 1896 g of hard carbon, 34 g of conductive agent and 70 g of polyvinylidene fluoride were mixed evenly. The conductive agent was a mixture of acetylene black and carbon black. The mass addition ratio was 1:1. The mixture was added to 1960 g of organic solvent and mixed evenly to prepare an oily slurry. (2) The oily slurry is evenly coated on the current collector, and after baking, the coating is 8 μm thick. (3) 1896 g of hard carbon, 34 g of conductive agent, and 70 g of aqueous binder were mixed evenly. The conductive agent was a mixture of acetylene black and carbon black in a mass addition ratio of 1:1. The mixture was added to 1960 g of deionized water and mixed evenly to prepare an aqueous slurry. The aqueous binder was a mixture of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 1:1:2.8. (4) The aqueous slurry prepared in step (3) is evenly coated on the negative electrode sheet prepared in step (2), and after drying, the composite coating is prepared on the negative electrode sheet of the sodium ion battery, and the peel strength of the negative electrode sheet is tested; (5) The negative electrode sheet is prepared into a sodium ion battery through processes such as rolling, winding, and assembly; (6) Test the different rate performance and 1C charge and discharge cycle life of sodium ion batteries. Example 3

[0028] (1) 1896 g of hard carbon, 34 g of conductive agent, and 70 g of aqueous binder were mixed evenly. The conductive agent was a mixture of acetylene black and carbon black, and the mass addition ratio was 1:1. The mixture was added to 1960 g of deionized water and mixed evenly to prepare an aqueous slurry. The aqueous binder was a mixture of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber. The mass ratio of each substance in the mixture was 1:1:2.8. (2) The aqueous slurry is evenly coated on the current collector, and after baking, it is prepared into a sodium ion battery negative electrode sheet, and the peel strength of the negative electrode sheet is tested; The appearance and peel strength of the negative electrode sheets of Examples 1-3, and the 10C rate performance and cycle comparison results of the batteries of Examples 1-2.

[0029] The lithium battery products produced in the above embodiment were tested and the following data results were obtained: Group Pole outsourcing Peel strength N / cm Example 1 The surface is smooth and without abnormalities 9.37、8.97 Example 2 Surface normal, no abnormalities 8.84、8.76 Example 3 Edge powder loss 4.12、3.97 Table 1 Comparison of appearance and peel strength of negative electrode sheets of Examples 1-3 It can be seen from the table that by combining the oil-based layer and the water-based layer, the good flexibility and adhesion of the oil-based layer, as well as the environmental protection and low cost advantages of the water-based layer are fully utilized. The oil-based layer can enhance the bonding strength between the electrode material and the current collector, and reduce the shedding of active materials during the charge and discharge process; the water-based layer provides a good channel for the transmission of sodium ions, which helps to improve the rate performance of the battery.

[0030] Group 10C discharge capacityAh 1C charge and discharge cycle Example 1 1.1252 1000 times capacity retention rate 93.8% Example 2 1.1232 1000 times capacity retention rate 95.9% Table 2 Comparison results of 10C discharge rate performance and cycle times of the battery cells of Examples 1 and 2 Experimental data shows that sodium-ion batteries assembled using the sodium battery negative electrode sheet prepared in this invention have significantly improved cycling stability and energy density. In charge-discharge cycle tests at a current density of 1C, the capacity retention rate reached over 95% after 1,000 cycles.

Claims

1. A method for preparing a composite-coated sodium-ion battery negative electrode sheet, characterized in that: The sodium battery negative electrode plate includes a current collector, and an oil-based layer and a water-based layer sequentially arranged on the surface of the current collector; wherein the oil-based layer is formed by coating and drying an oil-based slurry, the oil-based slurry including hard carbon, a conductive agent, and an oil-based binder; and the water-based layer is formed by coating and drying an water-based slurry, the water-based slurry including hard carbon, a conductive agent, and a water-based binder. The preparation steps are as follows: (1) Preparation of oily slurry: Mix hard carbon, conductive agent, and oily binder evenly, add them to an organic solvent, and stir them at high speed in a blender to prepare an oily slurry; apply the oily slurry on the current collector, and bake to form a pole piece with an oily active material layer; (2) Preparation of aqueous slurry: Mix hard carbon, conductive agent, and aqueous binder evenly, add to deionized water, and stir at high speed in a blender to prepare aqueous slurry; (3) The aqueous slurry is coated on the electrode of the oil-containing active material layer and baked to form the negative electrode of the sodium ion battery.

2. The method for preparing a composite coating sodium ion battery negative electrode sheet according to claim 1, characterized in that: The mass ratio of hard carbon: conductive agent: oil-based binder added in the oily slurry is (93.5-94.8%): (1.7-2.3%): (3.5-4.3%). The hard carbon, conductive agent and oil-based binder are added to an organic solvent and stirred at high speed in a blender.

3. The method for preparing a composite coating sodium ion battery negative electrode sheet according to claim 2, characterized in that: The solid content in the oil-based slurry is 48.3%-50.7%.

4. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 1, wherein: The mass ratio of each component in the aqueous slurry is hard carbon: conductive agent: aqueous binder = (94.1-95.0%): (1.7-2.3%): (3.3-3.6%). The hard carbon, conductive agent and aqueous binder are added to deionized water and stirred at high speed in a blender to prepare the aqueous slurry.

5. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 4, characterized in that: The solid content of the aqueous slurry is 43.4%-45.7%.

6. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 1, characterized in that: The thickness of the oil-based layer after drying is 5-8 μm.

7. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 1, characterized in that: The conductive agent is acetylene black, carbon black or a combination of the two.

8. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 2, characterized in that: The oil-based binder is polyvinylidene fluoride with a molecular weight of 700,000-1.2 million.

9. The method for preparing a composite-coated sodium-ion battery negative electrode sheet according to claim 4, characterized in that: The water-based binder is a mixed liquid of a thickener and a binder, the thickener is one or both of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose, the binder is styrene-butadiene rubber, and the weight ratio of the thickener to the binder is 1:(1.35-1.6).

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