Unlocking the Potential of Cathode Materials in Rechargeable Calcium Batteries: Structural Design and Electrochemical Mechanisms

ABSTRACT Rechargeable calcium batteries (RCBs) hold significant promise for large‐scale energy storage due to the abundance and low cost of calcium, as well as its potential to deliver high energy densities through multi‐electron transfer mechanisms. However, the practical application of RCBs remains hindered by the lack of high‐performance cathode materials. Despite notable advancements in developing various cathode materials, challenges such as slow Ca 2 + diffusion, poor electronic conductivity, and instability at the cathode/electrolyte interface still persist. This review provides an in‐depth analysis of the current status of cathode materials for RCBs, including metal sulfides, metal oxides, Prussian blue analogs, polyanionic compounds, and organic molecules. Drawing insights from other multi‐valent metal systems like Mg and Zn, the review explores optimization strategies for these materials, such as structural engineering, electronic modification, electrolyte solvation enhancement, and interface design between cathode and electrolyte. These strategies aim to improve ion transport, enhance stability, and boost the overall efficiency of RCBs. The future success of RCBs depends on overcoming these challenges through the development of novel materials and a deeper understanding of their electrochemical behaviors, paving the way for high‐performance, scalable, and cost‐effective energy storage solutions.