Electrochemical characterization of manganese oxide cathode materials based on Na0.4MnO2

Cathode materials for lithium rechargeable batteries were prepared from Na0.4MnO2 by solution and molten salt ion-exchanges. The former process results in partial replacement of sodium while the latter results in complete exchange. The discharge characteristics depend upon the sodium content, with the partially lithiated material exhibiting hysteresis in the charge/discharge profile and differential capacity plots from stepped potential experiments. For the fully lithiated material, a complex voltage profile with several distinct plateaus corresponding to several two-phase regions is observed. No evidence of spinel formation during ion-exchange or electrochemical cycling is seen for this system.