Partial sulfur doping induced lattice expansion of NiFe2O4 with enhanced electrochemical capacity for supercapacitor application

Nickel ferrite exhibits many advantages as electrode materials in the application of supercapacitor, such as high energy capacity and excellent cycle stability. Whereas, compared with identical-metal sulfides, the specific capacitance of NiFe2O4 is still insufficient. Hence, to combine the superiorities of oxides and sulfides, partial sulfur doping NiFe2O4 is obtained through hydrothermal synthesis method. Analyzed by Vienna Ab-initio Simulation Package (VASP) software and high-resolution transmission electron microscopy, the lattice parameters of NiFe2O4 are confirmed to be expanded by introducing sulfur atoms, which is beneficial to electrochemical performances. At a current density of 1 A/g, the specific capacitance of partial sulfur doping NiFe2O4 is calculated to be 284 F/g, higher than that of the original NiFe2O4 of 182.2 F/g. Moreover, a maximum energy density of 21.14 Wh/kg is achieved at a power density of 375 W/kg. This work shows that partial sulfur doping could improve the electrochemical performance of NiFe2O4. To sum up, this work provides an effective way to enhance the poor electrochemical performance of oxides, greatly encouraging the application of oxides in energy storage field.