Recent Progress in Cathode Materials for Ca-Ion Batteries

Exploring alternative battery systems to lithium-ion batteries becomes essential and urgent with the explosive growth of the electric vehicle and energy storage markets. Benefiting from resource abundance, low redox potential of Ca metal, and prospective high volumetric capacity, rechargeable calcium-ion batteries (CIBs) have recently attracted considerable attention in the field of energy storage. There is a breakthrough in the study of reversible precipitation/stripping of Ca metal at room temperature for anodes, but the cathodes for CIBs still suffer from low reversible capacity and poor cycle stability. This paper provides a comprehensive overview and recent progress of the cathode materials for CIBs, including metal oxides, Prussian blue analogs, polyanion materials, and organic cathodes. The features and modification strategies of each type of cathode material are discussed thoroughly. Finally, current issues of CIB cathodes and prospective solutions are presented.