Improved electrochemical performance of B doped O'3-NaMnO2 for Na-ion battery

Abstract

O'3-NaMnO2 possesses a high theoretical capacity due to its high initial sodium content as a cathode material in Na-ion batteries. However, complex phase transition from O'3 to P3, even to O1 phase caused by the gliding of layered structure occurred during Na extraction, leads to the collapse of the layered structure, and causes loss of battery capacity. To improve the structural stability of layered O'3-NaMnO2 cathode, the electrochemically inert B3+ with good affinity for oxygen was selected to substitute the Mn3+ in O'3-NaMnO2 and a series of O'3-NaBxMn1-xO2 (x=0, 0.05, 0.1, 0.15, 0.25) oxides were obtained by optimized preparation methods. The average effective radius of the transition-metal layer is reduced after B doping, making the structure more stable. At the same time, B inhibits the Jahn-Teller distortion caused by Mn3+. Among them, NaB0.1Mn0.9O2 shows improved cycle and rate performance. In-situ XRD and EIS results reveal that the enhanced electrochemical performance is resulted from the higher structure reversibility than O'3-NaMnO2.