The performance of silica sol directly affects the coating effect; therefore, relevant standards specify clear requirements for its physicochemical properties. Here are some key indicators:
Solid Content: Solid content refers to the mass percentage of silica in the silica sol, typically between 10% and 40%. Too low a solid content will result in an excessively thin coating, affecting performance; too high a content may increase viscosity, affecting coating uniformity.
Particle Size Distribution: Silica sol particles generally range from 5 to 100 nanometers in size. Smaller particle sizes result in better coating density and uniformity. However, excessively small particles may cause agglomeration, affecting stability.
pH Value: The pH value of silica sol is typically between 2 and 11. Acidic silica sol (pH 2-4) and alkaline silica sol (pH 9-11) are suitable for different process requirements. pH value also affects the stability of the colloid, therefore, it must be strictly controlled.
Viscosity: Viscosity affects the feasibility of the coating process and is typically controlled within the range of 1 to 100 mPa·s. Excessively high viscosity may lead to uneven coating, while too low viscosity may cause sagging.
Viocity: Viscosity affects the feasibility of the coating process and is typically controlled within the range of 1 to 100 mPa·s. Excessively high viscosity may lead to uneven coating, while excessively low viscosity may cause sagging. Impurity content: Metal ions (such as Na⁺, K⁺, Fe³⁺, etc.) and organic residues must be strictly controlled, otherwise the cycle life and safety of the battery may be affected.