Through the Maze of Multivalent‐ion Batteries: A Critical Review on the status of the research on cathode materials for Mg2+ and Ca2+ ions insertion

This review paper aims at addressing the status of transition metal‐based cathode materials for Mg 2+ and Ca 2+ ‐based multivalent ion batteries on a critical standpoint, providing a comprehensive overview. Multivalent‐based ions battery (MIB) technologies are among the most promising post‐Lithium electrochemical energy storage devices currently studied, but still they fall short in several aspects due to their early stage of research. In addition, difficult experimental conditions related to the electrolyte systems and the cathode materials require an additional quote of care when performing experiments. In this review, a global approach is undertaken, from an introduction to electrolytes to the studied insertion parameters that allow a fast (de)insertion of multivalent ions. Then the currently studied structural classes of cathode materials and a critic comment on data reporting, which are among the focal points of the actual state‐of‐the‐art research, are thoroughly discussed.