Na2mn3o7@Al2o3 Prepared with a Simple Method as Advanced Cathode Materials for Sodium Ion Batteries

Abstract

Recently, Na2Mn3O7 has greatly attracted the attention and interest of scholars due to its small voltage hysteresis (<0.05 V) and high theoretical specific capacity. However, its lower capacity retention and electrochemically performance limit its application. This work reports the facile surface coating of Na2Mn3O7 cathode material by electrochemically inert Al2O3 of different mass ratio for sodium ion batteries. The electrochemical test results indicate that the 5 wt% Na2Mn3O7@Al2O3 material exhibits outstanding cyclic stability and rate capability. It displays a prominent specific capacity of 115 mAh g-1 (at a current density of 50 mA g-1, 1.5-4.6 V) and a capacity retention of 61.2% after 50 cycles. A discharge-specific capacity of 52.7 mAh g-1 is also obtained at a high current density of 4C, and most notably, a high discharge-specific capacity of 117.9 mAh g-1 is still maintained when the current density returns to 0.1C. This suggests a superior structural stability of this material. The subsequent cyclic voltammetry (CV) and electrochemical impedance spectroscopy(EIS) tests also support this point.

Keywords: Na2Mn3O7, Al2O3-coated, structural stability, cathode