Functions of low crystallinity in lithium-rich positive electrode

Abstract

Intensive research is being conducted to further improve the performance of lithium-ion secondary batteries. Conventional cathode materials exhibit excellent charge-discharge cycle characteristics because only Li ions are extracted and inserted while maintaining the crystalline structure of the material. In contrast, lithium-rich layered oxide (LLO) materials with a low-crystalline structure have achieved high energy density and extraction/insertion of a large amount of Li ions. Herein, the existence of a low-crystalline phase in the LLO structure, formed by a crystal structure change accompanying the migration of pillar metal ions that support the Li deficient layer during extraction of Li-ions, is revealed by pair distribution function (PDF) analysis.