A multiphase coupling strategy to structurally stable manganese-based oxides cathode for high electrochemical performance sodium ion batteries

Abstract

Manganese (Mn) based oxides attract extensive attention as cathode materials for sodium (Na) ion batteries (SIBs) due to their high theoretical capacity and low cost. However, the Jahn-Teller distortion caused by the Mn (III) center and the phase transition of P2-O2 at high voltage (>4.0 V) limits its practical applications. In this work, a multiphase coupling scheme involving Na0.7MnO2.05 (P2), Na0.44MnO2 (T), and Na0.91MnO2 (Z) is presented to develop improved and available Mn based oxides cathode for superior electrochemical performance SIBs via solid state method. It is found that the optimal coupling at the molecular and atomic levels can be achieved by adjusting the regulation of morphology and grain size of the multiphase, which possesses larger interlayer spacing and fewer Mn3+ ions to suppress the Jahn-Teller lattice distortion of Mn3+ as well as the phase transition of P2-O2 at high voltage (>4.0 V). As a result, the as-prepared cathode delivers a high discharge specific capacity of 183.28 mA h g−1 at a rate of 0.5 C with a high-capacity retention of 77.2% after 100 cycles. Moreover, it also shows the fastest Na+ diffusion ability and kinetics properties, which is revealed by refined analysis of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves. This study presents a straightforward and scalable approach for developing novel cathode materials based on Mn oxides with excellent performance in sodium-ion batteries (SIBs).