Suppressing the Unfavorable Surface Layer Growth on Na0.44MnO2 Cathode by a NaTi2(PO4)3 Coating To Improve Cycling Stability and Ultrahigh Rate Capability

The tunnel-type Na0.44MnO2 as a potential cathode for sodium-ion batteries suffers from issues of manganese dissolution and surface layer outgrowth during cycling, which lead to poor electrochemical performances. It is found by ex situ scanning and transmission electron microscopies that applying a coating of NASICON-type NaTi2(PO4)3 (NTP) on the surface of Na0.44MnO2 particles can markedly suppress the surface layer growth phenomenon and improve the cycling stability and rate capability of this cathode material. The 2 wt % NTP-coated sample delivers a capacity retention of 99.0% after 100 cycles at 1C and a capacity of 82.2 mAh g–1 at 20C (71% of 0.1C capacity).