Graphite felt decorated with porous NiCo₂O₄ nanosheets for high-performance pseudocapacitor electrodes

Substrate materials are of great significance for the development of pseudocapacitor electrodes. Herein, pseudocapacitive NiCo₂O₄ have been successfully grown on the 3D graphite felt (GF) substrate via a two-step method, including the prior co-deposition of Ni and Co ions on the GF and succeeding thermal transformation of Ni/Co precursors to spinel NiCo₂O₄. Porous NiCo₂O₄ nanosheets are formed on the surface of GF, yielding stand-alone nanocomposite electrodes. The experimental results show that the NiCo₂O₄/GF electrode achieves a remarkable specific capacitance of 2205 F g⁻¹ at a current density of 1 A g⁻¹, which remains 1790 F g⁻¹ when the current density is increased to 20 A g⁻¹. After cycling at a current density of 5 A g⁻¹ for 2000 cycles, the NiCo₂O₄/GF electrode still exhibits 90.7% of its original specific capacitance. Such encouraging rate capability and cycling stability of the NiCo₂O₄/GF electrode are attributed to the optimized structure of NiCo₂O₄ that functions synergistically with the underlying GF substrate to achieve excellent electron conductivity and enhanced ion diffusivity. Therefore, the as-synthesized binder-free NiCo₂O₄/GF electrode is a promising candidate for high-performance pseudocapacitors.