Mainstream Optimization Strategies for Cathode Materials of Sodium-Ion Batteries

Sodium-ion batteries are promising candidates for grid-scale energy storage due to its abundance and similarities to lithium-ion batteries, whereas the lack of ideal cathode materials limits their practical development. Apart from exploring novel materials, applying optimization strategies on existing potential cathode materials is demonstrated to be effective and efficient in improving their electrochemical properties toward their theoretical best capabilities. Reported strategies include element doping, surface coating, morphology and structure design, defect engineering, etc. Herein, focusing on oxide and polyanionic cathode materials, a comprehensive and systematic review on emerging optimization strategies is provided by discussing representative studies of each. Corresponding fundamental principles, their applicable ranges, and common influences on properties are analyzed. Finally, the perspectives on the current impediments and future directions in the field are presented.