Lithium battery anode compounding principle (substantially the same as the whole machine ingredients)
1. Physical and chemical properties of raw materials.
(1) Graphite: Non-polar substance, easily contaminated by non-polar substances, easy to disperse in non-polar substances; not easy to absorb water, and not easy to disperse in water. Contaminated graphite, after being dispersed in water, is easy to re-agglomerate. The general particle diameter D50 is about 20 μm. The particles are various in shape and irregular, and are mainly spherical, flaky, fibrous, and the like.
(2) Water-based adhesive (SBR): small molecular line * chain emulsion, very soluble in water and polar solvents.
(3) Anti-precipitation agent (CMC): a polymer compound that is easily soluble in water and polar solvents.
(4) Isopropanol: a weakly polar substance, which reduces the polarity of the binder solution and improves the compatibility of the graphite and the binder solution; has a strong defoaming effect; and easily catalyzes the binder network。 Chain to increase bond strength。
Ethanol: weakly polar substance, which can reduce the polarity of the binder solution after adding, improve the compatibility of graphite and binder solution; has strong defoaming effect; easily catalyzes the adhesive line* to crosslink and improve the bonding strength (The effect of isopropanol and ethanol is essentially the same, and cost factors can be considered in mass production and then which one to add).
(5) Deionized water (or distilled water): A diluent is added as needed to change the flow of the slurry.
2. Pretreatment of raw materials:
A。 Mixing to homogenize the raw materials and improve consistency。
B, 300 ~ 400 ° C atmospheric pressure baking, remove surface oil substances, improve the compatibility with water binder, round the surface of the graphite edge (some materials to keep the surface special, not allowed to bake, otherwise the efficiency is reduced)。
(2) Water binder: Dilute properly to improve dispersibility.
3。 Blending, wetting and dispersing:
(1) Graphite is different from the binder solution* and is not easily dispersed.
(2) The graphite may be initially wetted with an aqueous alcohol solution and then mixed with the binder solution.
(3) The stirring concentration should be appropriately reduced to improve dispersion.
(4) The dispersion process is to reduce the distance between polar and non-polar materials and increase the potential energy or surface energy. Therefore, for the endothermic reaction, the overall temperature decreases when stirring. If the conditions permit, the stirring temperature should be raised appropriately to make the heat absorption easy, while improving the fluidity and reducing the difficulty of dispersion.
(5) The stirring process, such as adding a vacuum degassing process, removes the gas and promotes solid-liquid adsorption, and the effect is better.
(6) The principle of dispersion and dispersion are related to the contents of the positive electrode ingredients。
4. Dilute. The slurry is adjusted to a suitable concentration to facilitate coating.
Fourth, lithium battery Note on the ingredients:
1. Prevent mixing of other impurities;
2. Prevent slurry splashing;
3。 The concentration of the slurry (solid content) should be gradually adjusted from high to low to avoid adding trouble;
4。 Pay attention to scraping and scraping the bottom during the mixing process to ensure uniform dispersion;
5, the slurry should not be left for a long time to avoid precipitation or even reduction;
6。 The materials to be baked must be sealed and cooled before they can be added to avoid the change of the material quality of the components;
7. The length of the mixing time is mainly based on equipment energy and material loading; the use of the stirring paddle is replaced by the difficulty of slurry dispersion. If the replacement cannot be replaced, the rotation speed can be adjusted from slow to fast to avoid damage to the equipment;
8。 The slurry is sieved before discharge to remove large particles to prevent breakage during coating;
9. Strengthen the training of the ingredients to ensure that they have the professional knowledge to avoid a major disaster;
10, the key to the ingredients is to spread evenly, master the center, other ways can be adjusted。