Oxide cathodes for sodium-ion batteries:Designs,challenges,and perspectives

Sodium-ion batteries(SIBs),which are an alternative to lithium-ion batteries(LIBs),have attracted increasing attention due to their low cost of Na resources and similar Na storage mechanism to LIBs.Compared with anode materials and electrolytes,the development of cathode materials lags behind.Therefore,the key to improving the specific energy and promoting the application of SIBs is to develop high-performance sodium intercalation cathode materials.Transition-metal oxides are one of the most promising cathode materials for SIBs owing to their excellent energy density,high specific discharge capacity,and environmentally friendly nature.In the present work,the latest progress in the research of transition-metal oxides is summarized.Moreover,the existing challenges are discussed,and a series of strategies are proposed to overcome these drawbacks.This review aims at providing guidance for the development of metal oxides in the next stage.