Recent Advances in Surface Coatings of Layered Cathode Materials for High-Performance Sodium-Ion Batteries

Layered transition metal oxides (layered materials) have the advantages of simple synthesis methods, high average operating voltages, and good specific capacity, and are therefore promising cathode materials for sodium-ion batteries (SIBs). However, the capacity retention of these materials is poor due to the dissolution of transition metals caused by the detrimental reactions of the electrode with the electrolyte and the rupture of the electrode due to volume expansion during cycling. Studies have discovered that surface modification can effectively improve the aforementioned problems. This paper reviews the effects of different coating materials (e. g., carbon coatings, metal oxide coatings, phosphate coatings, etc.) on the performances of layered cathode materials and analyzes the reasons for the improved performance. In addition, the limitations of different coating materials and coating methods are presented, and future developments are proposed.