Electrochemical performance of Na4MnCr(PO4)3/C cathode affected by different transition metal dopants for sodium ion batteries

Abstract

Na4MnCr(PO4)3 (NMCP) has been considered as one kind of privileged cathodes with high energy density for sodium ion batteries (SIBs) due to three-electron redox reaction during the insertion/extraction process. Nevertheless, its practical use is restricted by its low intrinsic conductivity and serious Jahn-Teller distortions. Herein, a facile doping strategy was presented to address the above issues, and the effects of different kinds and quantities of transition metal dopants on electrochemical performance of NMCP were systemically studied. The results reveal that Ni50-NMCP/C has the most effective doping composition, showing a discharge capacity of 143.0 mAh g−1 at 50 mA g−1 and long-term cyclic stability with capacity retention of 55.7 % at 1000 mA g−1 over 500 cycles, higher than those of the pristine NMCP (106.6 mAh g−1 at 50 mA g−1 and 38.8 % capacity retention at 1000 mA g−1). The substitution of Ni2+ for Mn2+ promotes electron conductivity and structural stability, rendering improved electrochemical performance. Moreover, the promising electrochemical performance of Ni50-NMCP/C//HC full cell demonstrates the anode's potential for use. This study indicates a quick way to understand the effects of elemental doping on NMCP and explore novel high energy and high stability cathodes for SIBs.