Applications of sodium alginate and preparation methods of lithium-ion battery electrode sheets

Abstract

This invention discloses an application of sodium alginate and a method for preparing lithium-ion battery electrode sheets, relating to the field of materials technology. The method for preparing lithium-ion battery electrode sheets includes the following steps: thoroughly mixing electrode active materials, conductive additives, and binders, and then grinding them into powder; adding a mixed solvent of water and ethanol to the powder, grinding it thoroughly into a slurry, and then coating it onto copper foil; drying the treated copper foil in a stepped manner, then rolling and cutting it into small round sheets to obtain the lithium-ion battery electrode sheets; wherein the binder is sodium alginate. This invention uses sodium alginate, a water-based binder with a high Young's modulus, and provides a complete electrode sheet preparation process, offering good safety performance and cost advantages. The prepared electrode sheets are uniform, crack-free, and exhibit excellent cycle stability. This process is simple to operate, low in cost, and highly repeatable between batches, possessing green, safe, and environmentally friendly characteristics, making it an environmentally friendly technology.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to the application of sodium alginate and a method for preparing lithium-ion battery electrode sheets. Background Technology

[0002] In recent years, environmental and energy problems have become increasingly severe. Developing large-scale electrochemical energy storage is an effective way to alleviate the uneven distribution of energy in time and space. Lithium-ion batteries have long been considered a highly efficient and convenient energy storage device, and electrode materials, as an important component of the battery, are usually composed of active materials and conductive current collectors. Conductive agents and binders are added to the active materials to bond them together with the conductive layer of the electrode. Finally, after drying and rolling, the battery electrode is formed.

[0003] Currently, publicly available electrode manufacturing processes in China generally use PVDF as a binder. This necessitates the use of oily solvents such as N-methylpyrrolidone as diluents when preparing the active material slurry. However, due to its low Young's modulus, PVDF's bonding performance is far from meeting the requirements of electrode materials. Furthermore, when negative electrodes utilize materials such as silicon oxide, PVDF cannot effectively release the stress generated by the volume expansion effect during charging and discharging, easily leading to material performance degradation or even failure. Additionally, organic binders have drawbacks such as high toxicity and poor safety and environmental friendliness.

[0004] Therefore, selecting a suitable adhesive to replace PVDF and developing a related electrode fabrication process are urgent problems to be solved. Summary of the Invention

[0005] In view of this, this application provides an application of sodium alginate and a method for preparing lithium-ion battery electrode sheets, aiming to improve the current problem that PVDF binders are not applicable to certain materials, especially silicon-based anodes.

[0006] To achieve the above objectives, this invention discloses the application of sodium alginate as an aqueous binder in the preparation of lithium-ion battery electrode sheets.

[0007] This invention also discloses a method for preparing a lithium-ion battery electrode sheet, comprising the following steps:

[0008] Step 1: After thoroughly mixing the electrode active material, conductive additives, and binder, grind them into powder;

[0009] Step 2: Add the mixed solvent of water and ethanol to the powder described in Step 1, grind it thoroughly into a slurry, and then coat it onto the copper foil;

[0010] Step 3: After the copper foil processed in step 2 is dried in a stepped manner, it is rolled and cut into small round pieces to obtain lithium-ion battery electrode sheets.

[0011] The adhesive is sodium alginate.

[0012] In a preferred embodiment of the present invention, in step 1, the electrode active material is a silicon-carbon anode material with a diameter of 100 nm, and the conductive additive is conductive carbon black.

[0013] In a preferred embodiment of the present invention, in step 1, the mass ratio of the electrode active material, the conductive additive, and the binder is 3:1:1.

[0014] In a preferred embodiment of the present invention, in step 2, the volume ratio of water to ethanol in the mixed solvent is 7:1, and the mass-volume ratio of the powder to the mixed solvent is 100:1.6 (mg / mL).

[0015] In a preferred embodiment of the present invention, in step 2, the thickness of the copper foil is 10 μm, and the thickness of the paste coated on the copper foil is 25 μm.

[0016] In a preferred embodiment of the present invention, step 2, before coating the copper foil with the slurry, further includes a step of modifying the surface of the copper foil: adding a wetting agent to the surface of the copper foil to remove surface air, modifying its surface, and facilitating the scraping and covering of the electrode material.

[0017] Preferably, the wetting agent is ethanol.

[0018] In a preferred embodiment of the present invention, in step 3, the stepped drying method is as follows: the temperature is raised from room temperature to 60°C at a rate of 10°C / min, and dried for 4 hours under normal pressure; then the temperature is transferred to a vacuum drying oven, raised to 105°C at a rate of 5°C / min, kept at that temperature for 24 hours, and then lowered to room temperature at a rate of 10°C / min.

[0019] In a preferred embodiment of the present invention, in step 3, the force applied during rolling is 100 N.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention utilizes sodium alginate, a water-based binder with a high Young's modulus, and provides a complete electrode preparation process to complement it. This method offers good safety performance and cost advantages. The electrode sheets prepared using this method are uniform, crack-free, and exhibit excellent cycle stability. The process is simple to operate, low in cost, and highly reproducible between batches. Using ethanol and water as a mixed solvent, it is green, safe, and environmentally friendly, making it a truly eco-friendly technology.

[0022] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope (SEM) image of the cross-section of the battery electrode sheet prepared in Example 1 of the present invention;

[0024] Figure 2 SEM images of the electrode surface prepared for Example 1;

[0025] Figure 3 An optical photograph of the electrode sheet coated in Example 1;

[0026] Figure 4 An optical photograph of the electrode sheet coated in Comparative Example 2;

[0027] Figure 5 An optical photograph of the electrode sheet after drying in Example 1;

[0028] Figure 6 Optical photograph of the electrode sheet after drying (Comparative Example 3);

[0029] Figure 7 An optical photograph of the electrode sheet coated in Comparative Example 4;

[0030] Figure 8 The graph shows the cycle stability test results of the assembled half-cell for Comparative Example 4.

[0031] Figure 9 The graph shows the cycle stability test results of the assembled half-cell for Comparative Example 5. Detailed Implementation

[0032] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0033] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0034] Example 1:

[0035] (1) Mix 30 mg of silicon-carbon anode material (approximately 100 nm in diameter), 10 mg of conductive carbon black and 10 mg of sodium alginate, and grind the powder in a mortar for 1 h.

[0036] (2) Add 0.8 mL of a mixed solvent of water and ethanol (volume ratio 7:1) to the powder in step (1), and grind it thoroughly for 30 min to form a slurry;

[0037] (3) A certain amount of ethanol is first added to the rough side of the 10 μm thick copper foil to wet it. The purpose is to remove the air on the surface and slightly modify the surface so that the electrode material can be better coated and covered.

[0038] (4) Apply the slurry from step (2) to the copper foil surface to a thickness of 25 μm. After application, leave the surface on a table for 30 min.

[0039] (5) Transfer the electrode from step (4) to an oven, heat it from room temperature to 60 ℃ at a rate of 10 ℃ / min, and dry it for 4 h under normal pressure. Then transfer it to a vacuum drying oven, heat it to 105 ℃ at a rate of 5 ℃ / min, keep it at that temperature for 24 h, and then cool it to room temperature at a rate of 10 ℃ / min before taking it out.

[0040] (6) The removed electrode sheet is rolled and pressed with a force of 100N; after rolling, it is cut into small round pieces to assemble the battery.

[0041] Comparative Example 1

[0042] (1) Mix 30 mg of silicon-carbon anode material (approximately 100 nm in diameter), 10 mg of conductive carbon black and 10 mg of sodium alginate, and grind the powder in a mortar for 1 h.

[0043] (2) Add 0.8 mL of water to the powder from step (1) and grind it thoroughly for 30 min to form a slurry;

[0044] (3) Apply the slurry from step (2) to the rough side of a 10 μm thick copper foil, with a coating thickness of 25 μm. After coating, place it on a table for 30 min.

[0045] (4) Transfer the electrode from step (3) to an oven, heat it from room temperature to 60 ℃ at a rate of 10 ℃ / min, and dry it for 4 h under normal pressure. Then transfer it to a vacuum drying oven, heat it to 105 ℃ at a rate of 5 ℃ / min, keep it at that temperature for 24 h, and then cool it to room temperature at a rate of 10 ℃ / min before taking it out.

[0046] (5) The removed electrode sheet is rolled and pressed with a force of 100 N; after rolling, it is cut into small round pieces to assemble the battery.

[0047] Comparative Example 2

[0048] (1) Mix 30 mg of silicon-carbon anode material (approximately 100 nm in diameter), 10 mg of conductive carbon black and 10 mg of sodium alginate, and grind the powder in a mortar for 1 h.

[0049] (2) Add 0.8 mL of a mixed solvent of water and ethanol (volume ratio 7:1) to the powder in step (1), and grind it thoroughly for 30 min to form a slurry;

[0050] (3) A certain amount of ethanol is first added to the rough side of the 10 μm thick copper foil to wet it. The purpose is to remove the air on the surface and slightly modify the surface so that the electrode material can be better coated and covered.

[0051] (4) Apply the slurry from step (2) to the copper foil surface to a thickness of 25 μm. After application, leave the surface on a table for 30 min.

[0052] (5) Transfer the electrode from step (4) to a vacuum drying oven, raise the temperature to 105 °C at a rate of 5 °C / min, keep it at that temperature for 24 h, and then lower it to room temperature at a rate of 10 °C / min before taking it out.

[0053] (6) The removed electrode sheet is rolled and pressed with a force of 100 N; after rolling, it is cut into small round pieces to assemble the battery.

[0054] Comparative Example 3

[0055] (1) Mix 30 mg of silicon-carbon anode material (approximately 100 nm in diameter), 10 mg of conductive carbon black and 10 mg of sodium alginate;

[0056] (2) Add 0.8 mL of a mixed solvent of water and ethanol (volume ratio 7:1) to the powder in step (1), and grind it thoroughly for 30 min to form a slurry;

[0057] (3) A certain amount of ethanol is first added to the rough side of the 10 μm thick copper foil to wet it. The purpose is to remove the air on the surface and slightly modify the surface so that the electrode material can be better coated and covered.

[0058] (4) Apply the slurry from step (2) to the copper foil surface to a thickness of 25 μm. After application, leave the surface on a table for 30 min.

[0059] (5) Transfer the electrode from step (4) to a vacuum drying oven, raise the temperature to 105 °C at a rate of 5 °C / min, keep it at that temperature for 24 h, and then lower it to room temperature at a rate of 10 °C / min before taking it out.

[0060] (6) The removed electrode sheet is rolled and pressed with a force of 100 N; after rolling, it is cut into small round pieces to assemble the battery.

[0061] Comparative Example 4

[0062] (1) Mix 30 mg of pure silicon material (approximately 50 nm in diameter), 10 mg of conductive carbon black and 10 mg of sodium alginate, and grind the powder in a mortar for 1 h;

[0063] (2) Add 0.8 mL of a mixed solvent of water and ethanol (volume ratio 7:1) to the powder in step (1), and grind it thoroughly for 30 min to form a slurry;

[0064] (3) A certain amount of ethanol is first added to the rough side of the 10 μm thick copper foil to wet it. The purpose is to remove the air on the surface and slightly modify the surface so that the electrode material can be better coated and covered.

[0065] (4) Apply the slurry from step (2) to the copper foil surface to a thickness of 25 μm. After application, leave the surface on a table for 30 min.

[0066] (5) Transfer the electrode from step (4) to an oven, heat it from room temperature to 60 ℃ at a rate of 10 ℃ / min, and dry it for 4 h under normal pressure. Then transfer it to a vacuum drying oven, heat it to 105 ℃ at a rate of 5 ℃ / min, keep it at that temperature for 24 h, and then cool it to room temperature at a rate of 10 ℃ / min before taking it out.

[0067] (6) The removed electrode sheet is rolled and pressed with a force of 100 N; after rolling, it is cut into small round pieces to assemble the battery and test the performance of the half cell.

[0068] Comparative Example 5

[0069] (1) Mix 30 mg of pure silicon material (approximately 50 nm in diameter), 10 mg of conductive carbon black and 10 mg of PVDF, and grind the powder in a mortar for 1 h;

[0070] (2) Add 0.8 mL of N-methylpyrrolidone to the powder from step (1) and grind it thoroughly for 30 min to form a slurry;

[0071] (3) Apply the slurry from step (2) to the rough side of a 10 μm thick copper foil, with a coating thickness of 25 μm. After coating, place it on a table for 30 min.

[0072] (4) Transfer the electrode from step (3) to an oven, heat it from room temperature to 60 ℃ at a rate of 10 ℃ / min, and dry it for 4 h under normal pressure. Then transfer it to a vacuum drying oven, heat it to 105 ℃ at a rate of 5 ℃ / min, keep it at that temperature for 24 h, and then cool it to room temperature at a rate of 10 ℃ / min before taking it out.

[0073] (5) The removed electrode sheet is rolled and pressed with a force of 100 N. After rolling, it is cut into small round pieces to assemble the battery and test the battery performance. The cycle current density is 0.1 A / g.

[0074] The above provides a detailed description of the method for preparing lithium-ion battery electrode sheets using an aqueous adhesive according to this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a lithium-ion battery electrode sheet, characterized in that, Includes the following steps: Step 1: After thoroughly mixing the electrode active material, conductive additives, and binder, grind them into powder; Step 2: Add the mixed solvent of water and ethanol to the powder described in Step 1, grind it thoroughly into a slurry, and then coat it onto the copper foil; Step 3: After the copper foil processed in step 2 is dried in a stepped manner, it is rolled and cut into small round pieces to obtain lithium-ion battery electrode sheets. The adhesive is sodium alginate. In step 1, the electrode active material is a silicon-carbon anode material with a diameter of 100 nm, and the conductive additive is conductive carbon black; In step 1, the mass ratio of the electrode active material, conductive additive, and binder is 3:1:1; In step 2, the volume ratio of water to ethanol in the mixed solvent is 7:1, and the mass-volume ratio of the powder to the mixed solvent is 100 mg: 1.6 mL. In step 2, the copper foil has a thickness of 10 μm, and the slurry coating on the copper foil has a thickness of 25 μm. In step 2, before coating the copper foil with the slurry, the step of modifying the surface of the copper foil is also included: adding a wetting agent to the surface of the copper foil to remove surface air and modifying its surface to facilitate the coating and coverage of the electrode material; the wetting agent is ethanol; In step 3, the step-by-step drying method is as follows: the temperature is raised from room temperature to 60 ℃ at a rate of 10 ℃ / min, and dried for 4 h under normal pressure; then it is transferred to a vacuum drying oven, heated to 105 ℃ at a rate of 5 ℃ / min, kept at that temperature for 24 h, and then cooled to room temperature at a rate of 10 ℃ / min. In step 3, the force applied during rolling is 100 N.

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