公益社団法人 日本金属学会

In this talk, we present two types of challenges that we are currently focusing. One is the development of the cathode materials for MRBs. Based on the similarity between spinel and rocksalt structures, we show that some spinel oxides (e.g., MgCo2O4, etc) can be cathode materials for Mg rechargeable batteries around 150 °C. The Mg insertion into spinel lattices occurs via “intercalation and push-out” process to form a rocksalt phase in the spinel mother phase. The other one is the dual-ion battery system, in which two types of carriers, such as Li and Mg ions, are used for the electrode reactions. Sluggish solid-phase diffusion has been an essential issue in developing intercalation electrode materials using multivalent ions. Compared to monovalent Li ions, the diffusion of multivalent ions is still not well understood. Here, combining first-principles calculations with electrochemical experiments, it is shown that the diffusion of divalent Mg ions is significantly facilitated in Li–Mg dual-cation systems, and the activation energy is remarkably reduced by the concerted interactions of the preceding Li ions and following Mg ions. Thus, making dual-ion systems is a promising way to construct high-energy-density, rechargeable batteries with multivalent ions.