Synergistic Fe/Cr Co‐Doping and Graphene Compositing Boost Ni ₄ OHF ₇ ‐Based Supercapacitor Electrodes

ABSTRACT

Nickel hydroxyfluoride (Ni ₄ OHF ₇ ) has attracted increasing attention due to its high theoretical capacitance, yet its rate capability and cycling stability remain to be substantially improved. Here, we achieve dual optimization through elemental doping and support interaction, doping with Fe and Cr to enhance the rate capability, and compositing with reduced graphene oxide (rGO) to improve cycling stability. Experimental results show that the introduction of Cr, with lower electronegativity, further elevates the electronic state of the host element, while rGO facilitates the uniform distribution of active materials. The comprehensively optimized electrode material, denoted NFCHF/G, delivers a specific capacitance of 2852 F g ⁻¹ at a current density of 1 A g ⁻¹ , and retains 80% of its initial specific capacitance after 10,000 cycles. An asymmetric supercapacitor (ASC) based on NFCHF/G//AC achieves a maximum energy density of 71.9 Wh kg ⁻¹ at a power density of 750 W kg ⁻¹ , demonstrating promising application prospects. This work provides a reliable strategy for the development of hydroxyfluoride‐based electrode materials and is expected to better meet future energy demands.