Layered Co/Ni-free oxides for sodium-ion battery cathode materials

Sodium-ion batteries (SIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs) due to the similar electrochemical properties of sodium and lithium and the abundance and low cost of sodium resources. Layered transition metal oxide materials are a promising kind of cathode materials because of their flexible compositions of transition metal elements and favorable specific capacities. In particular, the relatively low-cost or price-stable layered Co/Ni-free cathode oxide materials (such as Mn-, Fe-, Cr-, and V-based oxides) for SIBs show great potential to either complement or replace LIBs to meet the rapidly growing demands of clean energy due to their comparable or even superior rate and cycle performances compared with those of the layered Co/Ni-containing oxides.