Adverse effects of interlayer-gliding in layered transition-metal oxides on electrochemical sodium-ion storage
Layered sodium transition-metal oxides are the most widely investigated electrodes for sodium-ion batteries (SIBs), which are a promising technology for large-scale static energy storage. Compared with their lithium counterparts, layered sodium transition-metal oxides exhibit multiple oxygen sublattices depending on the sodium concentration, and therefore phase transitions involving rearrangements of the intercalation host frequently occur during charge–discharge. Herein we summarize existing literature reports on layered sodium oxide electrodes and analyze the effects of host rearrangements on electrochemical properties. It was demonstrated that phase transitions associated with the gliding of transition-metal slabs are unfavorable for battery performance in several crucial aspects, including energy efficiency, rate capability, and cycle stability. Desirable layered electrodes for SIBs should maintain a stable intercalation host enabling rapid sodium-ion transport within a wide range of sodium concentration.