A surface chemistry assistant strategy to high power/energy density and cost-effective cathode for sodium ion battery

In this work, high power/energy density (6750 W kg−1/364.2 Wh kg−1) Na2.4Fe1.8(SO4)3 (NFS) composite has been achieved by surface chemistry assistant effective carbon coating at 350 °C with highly improved electrochemical performance as cathode materials for sodium ion batteries (SIBs). The prepared NFS/C composite shows superb electrochemical performance of high capacity (100.2 mAh g−1 at 1C), great cyclability (95.0 mAh g−1 after 100 cycles at 1 C) and excellent rate performance (95.1 mAh g−1 at 5 C, 91.3 mAh g−1 at 10 C). The full battery of NFS/C coupled with TiO2 anode material also exhibits high reversible capacity of 87.0 mAh g−1 at 10 C with an average discharge voltage over 3.0 V. The outstanding performance of this NFS/C composite originates from highly improved electron conductivity by surface chemistry enhanced effective carbon coating and restricted particle size. This NFS/C composite has fully demonstrated the high-voltage and low cost advantages of polyanion type sulfate materials. It can be one of the most pragmatic candidates for large scale energy storage cathode material in SIBs. This synthesis method for low temperature carbon coating can also be useful for other electrode materials especially those may decompose or reduce at high temperature.