Commonly used lithium-ion battery electrolytes are generally composed of organic solvents and electrolytes (lithium salts).
Requirements for solvents in lithium-ion batteries include safety, oxidation stability, negative electrode compatibility, conductivity, etc. The overall requirement is that the solvent has a high dielectric constant, low viscosity and other characteristics. . Lithium-ion batteries generally use aprotic polar solvents, and the carbonate series (including cyclic carbonates such as EC and PC and chain carbonates such as DMC and EMC) are widely used at this stage. Usually, the electrolytic solvent is a mixed solvent. Ethylene carbonate (EC) has become the main component of most electrolytes due to its excellent film-forming effect. The main solvent currently used in lithium batteries ismixed binary or ternary solvents. such as EC+DMC, EC+DEC, EC+DMC+EMC, etc.
The electrolyte is an essential component of lithium electrolyte. Currently, electrolytes include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LIBF4), etc. Among them, lithium hexafluorophosphate has good properties of conductivity and electrochemical stability, it is the current mainstream electrolyte. However, lithium hexafluorophosphate also has two disadvantages: first, poor thermal stability; second, it is sensitive to moisture and hydrofluoric acid (HF) and is prone to decomposition reactions. Although people are working hard to find new electrolytes to achieve a better combination of conductivity, thermal stability and water resistance, no electrolyte capable of completely replacing lithium hexafluorophosphate hasyet been found.
A small amount of certain additives may also be added to the electrolyte to improve certain aspects of performance. There are many types of additives that can be selected and used depending on the purpose of the battery.