What are the classification of electrolyte lithium salt? What are the characteristics of traditional inorganic electrolyte lithium salts?

Lithium salt, as a component of a lithium ion battery, affects the performance of the battery. There are many types of electrolyte lithium salts, which can be divided into inorganic anion lithium salts and organic anion lithium salts according to the types of anions. They can also be simply divided into fluoride-containing lithium salts and non-containing according to whether the anions contain fluorine. Fluoride lithium salt, this article will introduce four widely used inorganic electrolyte lithium salt.

The inorganic anion lithium salts mainly include lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6) and lithium hexafluorophosphate (LiPF6).

Lithium perchlorate (LiClO4)

LiClO4 is the longest-studied lithium salt with appropriate conductivity, thermal stability and oxidation stability, but because it is a strong oxidant, for safety reasons, the international lithium battery industry It is generally believed that it is only suitable for research work systems, but not for practical batteries.

Lithium tetrafluoroborate (LiBF4)

LiBF4 is a common additive of lithium salt. Compared with LiPF6, LiBF4 has a wider operating temperature range, better stability at high temperature and better performance at low temperature.

LiBF4 can also enhance the film-forming ability of electrolyte to the electrode and inhibit the corrosion of Al foil. However, due to the small radius of BF4 - and the difficulty of dissociation, the ionic conductivity of LiBF4 based electrolyte is low. Therefore, LiBF4 has great limitations when it is used as lithium electrolyte alone, and is often used in combination with lithium salt with high conductivity.

Lithium hexafluoroarsenate (LiAsF6)

Among the known lithium salts, LiPF6-based electrolyte has the best cycle efficiency, relatively good thermal stability and almost the highest electrical conductivity. However, the potential carcinogenic effects of Asv reduction products limit its application.

Lithium hexafluorophosphate (LiPF6)

LiPF6 has good electrochemical stability, does not corrode the current collector, and is easily soluble in carbonate organic solvents. At the same time, due to the large radius of PF6- and weak association at room temperature, LiPF6 solution has high ionic conductivity. Although LiPF6 has poor thermal stability and is easy to hydrolyze, it is still the most widely used among the four traditional inorganic electrolyte lithium salts The most commercially valuable.