Controlling lithium cobalt oxide phase transition using molten fluoride salt for improved lithium-ion batteries

LiCoO₂ is a widely used lithium-ion battery cathode material known for its high energy density. However, its practical capacity is limited by a harmful phase transition at high voltages. This study demonstrates a method to control this phase transition by treating LiCoO₂ particles with a molten salt of MgF₂-LiF. This treatment facilitates Mg diffusion and doping into the LiCoO₂ bulk and forms a stable coating layer on the surface. Ex situ X-ray diffraction analysis confirms the inhibition of the harmful phase transition and the emergence of a different phase when charged to 4.7 V. The modified LiCoO₂ exhibits improved electrochemical performance at high voltages, providing a strategy for achieving ultra-high energy density LiCoO₂ cathodes.

Mayumi Mikami, Jo Saito, Teruaki Ochiai, Masahiro Takahashi, Tatsuyoshi Takahashi, Yohei Momma, Kazutaka Kuriki, Rihito Wada, Kazune Yokomizo, Genki Kobayashi, Shinichi Komaba, Shunpei Yamazaki