The electrolyte, also known as the "blood" of lithium batteries, is the carrier of lithium ion transport, determining the ion conductivity, operating temperature range, and long-term stability of the battery cell. It is mainly composed of solvents, lithium salts, and functional additives in proportion, and its production, transportation, and use all require extremely high environmental humidity, making it prone to react with water vapor.
Lithium salt is the conductive core of the electrolyte, which dissociates lithium ions when dissolved in a solvent, ensuring that ions can migrate back and forth between the positive and negative electrodes during the charging and discharging process. The solvents are mostly organic carbonate mixed systems, and different types of solvents are combined to balance the ability to dissolve lithium salts, low-temperature fluidity, and electrochemical stability window. A single solvent is difficult to meet multiple requirements such as high voltage, low temperature, and long cycle at the same time, so the industry commonly uses compound solvents.
The proportion of additives added is not high, but their role is crucial. Some additives assist in forming a high-quality SEI film on the negative electrode, inhibiting the continuous decomposition of the electrolyte; Some can enhance the high-voltage resistance of battery cells; Some also have the functions of flame retardancy, gas suppression, and improving low-temperature performance. Formula is the core technology of electrolyte manufacturers, and there are significant differences in electrolyte formulas for power cells, energy storage cells, and consumer digital cells used for different purposes.
The electrolyte preparation is completed in a sealed and anhydrous workshop. After purification and dehydration of the raw materials, they are stirred and mixed under an inert atmosphere, filtered and tested, and then filled and stored. After injecting the electrolyte into the battery cell, a certain soaking time is required to allow the electrolyte to fully penetrate the pores of the electrode. If the purity of the electrolyte is insufficient and the moisture exceeds the standard, it will cause problems such as gas production in the battery cell, rapid increase in internal resistance, and accelerated cycling decay.
