A collaborative strategy with ionic conductive Na2SiO3 coating and Si doping of P2-Na0.67Fe0.5Mn0.5O2 cathode: An effective solution to capacity attenuation

Abstract As a promising cathode material, the layered oxide P2-Na0.67Fe0.5Mn0.5O2 has the obviously advantage of environmental friendliness, low cost and high theoretical capacity (290 mAh g−1), but the unfavored phase transitions lead to fast capacity decay during charge and discharge process. Surface modification and element substitution of cathode materials are emphasized for guaranteeing excellent electrochemical performance. Herein, we propose a collaborative strategy that the surface of layered P2-Na0.67Fe0.5Mn0.5O2 modified with conducting ionic Na2SiO3 nanolayers, 4.06 nm in thickness, which can inhibit side effects between the material and the electrolyte, ensure Na-ion diffusion coefficient, reduce the polarization and improve the cycling stability of the material. Furthermore, the partial element substitution of Si4+ during the coating process can be conducive to the extraction and embedding of sodium ions and able to stabilize the crystal structure of the materials resulting from a smaller radius of Si4+ and a higher bond energy of Si-O, which can enhance rate performance and thermal stability of the cathode materials. Above all, the collaborative strategy with ionic conductive Na2SiO3 coating and Si doping is reliable and effective to display preferable electrochemical properties for sodium-ion batteries.