The effect of co solvents on the wide temperature performance of electrolytes

The composition and design of a wide temperature electrolyte involve both liquid phase and electrolyte/electrode interface requirements. A wide liquid temperature range, high electrochemical stability, and low-temperature ion conductivity are necessary conditions for electrolytes, and the electrolyte electrode interface plays a more important role in maintaining the exchange of Li+and charge between the electrolyte and the electrode, as well as enhancing the compatibility between the electrolyte and electrode materials. Liquid phase modification is mainly achieved through the use of new electrolyte lithium salts and the use of co solvents with a wide liquid range, while interface modification is mainly achieved by adding low-temperature and high-temperature additives to the electrolyte.

Multicomponent mixed solvents are commonly used to dissolve lithium salts and ionize chlorinated vinyl carbonate into freely moving anions and cations, with each component typically containing more than 10% lithium salts. The solvent selection for wide temperature electrolytes usually considers the following properties: (1) melting point and boiling point. Maintain a liquid state as much as possible within the operating temperature range of the battery. (2) Electrochemical window. The oxidation potential of vinyl chloride carbonate solvent should be greater than the positive electrode potential for complete lithium removal and lower than the negative electrode potential for complete lithium insertion. (3) Stability and solubility of lithium salts. (Relative dielectric constant. High dielectric constant solvents have high molecular polarity, which is conducive to the ionization of lithium salts as free moving anions and cations. However, at the same time, the melting point, boiling point, and viscosity of the solvent are high, which has an adverse effect on the low-temperature performance of the electrolyte. Currently, the reported solvents for lithium-ion battery electrolytes mainly include esters, ethers, sulfones, and amides. Ethers have a low oxidation potential and are generally only used in low potential systems.) Unified, such as lithium sulfur batteries or primary lithium batteries. Sulfone has high electrochemical stability and can be used in high potential battery systems, but it usually has a high melting point and is not suitable for wide temperature electrolyte systems. Carbonate series solvents include chlorinated vinyl carbonate (EC), dibromonepentanol dimethyl carbonate (DMC), decabromodiphenylethane, and dibromonepentanediol