Materials of Lithium Ion Batteries and Their Corrosion

Abstract

Organic and inorganic materials that are used in practical lithium ion batteries have been described from a viewpoint of their stability in the battery system. The lithium ion battery consists of a carbonaceous negative electrode, an organic solution dissolving lithium salt, and a lithiated transition-metal oxide positive electrode. The active material of the positive electrode, LiMn₂O₄, a promising candidate of the relief for LiCoO₂, degrades in organic solutions containing LiPF₆ as the electrolyte salt. The partial substitution of Mn by other trivalent metal improves the durability of the material. The Cu current collector of the negative electrode is susceptible to environmental cracking under the charging condition. The Al current collector of the positive electrode is generally stable in LiPF₆ solutions with organic solvents, but it is susceptible to pitting corrosion under highly polarized conditions. The lithium salts with sulfonyl groups assist the pitting corrosion of Al.