Reaction Mechanism, Challenges, and Strategies of High-Energy-Density Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted considerable research interest for large-scale energy storage due to the natural abundance and wide geographic distribution of sodium. Among various cathode materials, conversion-type cathodes have garnered particular attention due to their element richness, high specific capacity, and enhanced safety and reliability. However, their practical application faces challenges, including huge volume expansion, incomplete reversible conversion reactions, and severe side reactions. This review summarizes the unique advantages and critical issues of conversion-type cathode materials, along with recent advances in various cathodes for SIBs. First, the reaction mechanisms of different conversion-type cathode materials are analyzed and summarized to provide theoretical foundations for practical implementation. Particularly, we propose novel countermeasures addressing common cathode challenges, offering new perspectives for future research on these materials. Notably, composite conversion-type cathodes demonstrate substantial potential as evidenced by their remarkable energy density. Future research should focus on in-depth investigations of reaction mechanisms, modification strategies, and characterization techniques for conversion-type cathodes, thereby advancing the development of high-energy-density cathode materials.