Advanced chemicals

The electrolyte of lithium ion battery is composed of electrolyte lithium hexafluorophosphate (LiPF6) and organic solvents such as EC, EMC, DEC and DMC. Lithium hexafluorophosphate is crystallized by dissolving phosphorus pentachloride and lithium fluoride in anhydrous hydrogen fluoride, and its suppliers are mainly abroad, such as Merck of Germany and Stella of Japan. China is the third country in the world to industrially produce lithium hexafluorophosphate after Japan, and only a few domestic enterprises can produce it, such as Guangjin Hi-Tech, Tianjin Chemical Design and Research Institute, Shandong Feicheng Xingtai Chemical Plant, etc.

The electrolyte commonly used in lithium ion batteries is generally composed of organic solvent and electrolyte (lithium salt).

The requirements of solvents for lithium ion batteries include safety, oxidation stability, compatibility with negative electrode, conductivity and so on. Generally, solvents are required to have high dielectric constant and low viscosity. Lithium-ion batteries generally use polar aprotic solvents, and carbonate series (including cyclic carbonates such as EC and PC and chain carbonates such as DMC and EMC) are widely used at this stage. Electrolyte solvents are generally mixed solvents, and ethylene carbonate (EC) is the main component of most electrolytes because of its excellent film-forming effect. At present, the main solvents used in lithium batteries are binary or ternary mixed solvents based on EC, such as EC+DMC, EC+DEC, EC+DMC+EMC, etc.

Electrolyte is an important part of lithium electrolyte. At present, there are lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate (LIBF4). Among them, lithium hexafluorophosphate is the mainstream electrolyte with good conductivity and electrochemical stability.

But lithium hexafluorophosphate also has two disadvantages:

First, the thermal stability is poor;

Secondly, it is sensitive to moisture and hydrofluoric acid (HF) and prone to decomposition reaction.