Morphology-controllable preparation of NiFe₂O₄ as high performance electrode material for supercapacitor

NiFe₂O₄ (NFO) with different morphologies were successfully synthesized via a facile hydrothermal method of different precipitants. Results showed that the NFO obtained using urea as precipitant (NFO-U) formed a nanosheet shape, while the powders prepared using CH₃COONa (NFO-C) exhibited a nanoparticle structure. Both of the two NFO showed a good crystallinity. Conclusion was reached through the results of BET and electrochemical tests that layer structure would improve the properties through a larger specific surface area. Encouragingly, the specific capacitance of NFO-U could arrive 240.9 F/g at the current density of 1 A/g. It was worth noting that the cycle performance of NFO-U was excellent, of which the specific capacitance improved to 128% after 2000 cycles. In addition, an asymmetric supercapacitor (ASC) system was constructed utilizing NFO-U as positive electrode while activated carbon (AC) as negative electrode. The two-electrode system showed a good performance with energy density of 10.15 Wh/kg at a power density of 140 W/kg. Therefore, the construction of sheet-like structures greatly improved the electrochemical performance of NiFe₂O₄ materials.