Boosting energy storage capacity: Transition metal-modified binary nickel hydroxide hydrate composites for supercapattery application

Transition metal hydroxycarbonates are extensively studied in energy storage devices for their unique features: high redox activity, low polarization, better structural stability, and high energy features. Therefore, CuNi, MnNi, and CoNi carbonate hydroxide hydrate binary composites were synthesized as battery-grade electrode materials for supercapatteries, aiming to enhance conductivity through synergistic effects and tailored morphologies. The morphological modifications and their influence on the electrochemical performance have been systematically investigated. Copper-based nickel carbonate hydroxide hydrate (Cu@NCHH) composite grown on Ni-foam (NF) among the other pairs yields the highest specific capacity/specific capacitance of 736.50C g⁻¹/1486.38 F g⁻¹ owing to its highly exposed electroactive sites for rapid and better intercalation/de-intercalation of OH⁻ ions into the bulk material. Supercapattery fabricated by Cu@NCHH/NF coupled with activated carbon electrode (AC/NF) exhibits outstanding energy storage capacity (42.20 Wh/kg) with a maximum power density of 12.29 kW/kg. The device also displays a significant improvement in cycling performance up to 161 % over 1000 cycles and 97 % over 5000 cycles with almost 100 % coulombic efficiency. Overall, this work provides a facile and efficient method to produce highly performing binder-free binary nickel carbonate hydroxide hydrate composite (M@NCHH/NF) for supercapattery.