Binder‐Free NiCo(PO ₄ ) ₃ Nanosheet Electrode for Supercapattery With Enhanced Ion Transport and Long‐Term Stability

ABSTRACT Binder‐free electrodes are emerging as a transformative solution in electrochemical energy storage systems, offering direct electron transport pathways and eliminating the limitations imposed by insulating binders. In this work, we report the synthesis of nickel‐cobalt phosphate dihydrate (NCP) grown directly on nickel foam using a simple hydrothermal method carried out at 180°C for 12 h. This straightforward approach yielded a distinctive flake and nanosheet morphology, resulting in abundant electroactive sites, enlarged surface area, and open channels for rapid ion diffusion. Electrochemical investigation revealed the remarkable performance of the NCP electrode. Cyclic voltammetry (CV) demonstrated a specific capacity of 118.8 C/g (215 F/g) at 5 mV/s, while galvanostatic charge‐discharge (GCD) measurements confirmed a specific capacity of 98.8 C/g (178.9 F/g) at 1 A/g within a 0.55 V potential window. To evaluate practical applicability, a supercapattery device was assembled using the binder‐free NCP electrode as the positive electrode and activated carbon (AC) as the negative electrode. The NCP//AC device delivered a specific capacity of 87.7 C/g at 0.5 A/g. Most notably, the device demonstrated outstanding electrochemical stability, maintaining 92.9% capacity retention after 5000 cycles at 2 A/g. These findings highlight the efficacy of the hydrothermal approach and the synergistic role of Ni and Co in stabilizing the phosphate framework. The NCP electrode, with its unique nanosheet architecture, emerges as a promising candidate for next‐generation, high‐performance supercapattery.