Anode chemistry in calcium ion batteries: A review

Large-scale energy storage and scientific research rapidly promote the research and exploration of calcium ion batteries (CIBs) due to the abundant reservation of calcium and the competitive redox potential of Ca/Ca2+. However, several critical issues hindered its development, especially the unsatisfactory performance of anode materials due to the poor plating/stripping reversibility Ca metal and sluggish de-solvation kinetics of Ca2+ ion in the electrolyte. This review aims to provide a timely access to the state-of-art advance in anode chemistry of CIBs. Firstly, an overview on the development history of CIBs is presented. Then, a comprehensive understanding on the challenges facing CIBs is elaborated. The advancements on the development of appropriate salts and electrolytes to achieve highly reversible plating/stripping of calcium metal anode are systematically discussed. As alternative to metallic calcium anode, suitable anode candidates for hosting calcium ions are summarized, including alloying, intercalation, and organic electrodes systems. Finally, critical challenges for metallic calcium and alternative anode materials are envisioned, followed by their important future directions for the development and application in CIBs.