Li-Assisted Structural and Morphological Engineering of Ni-Co Phosphate Nanoarchitectures for High-Performance...

The electrochemical properties of transition-metal phosphates could be considerably improved through structural and morphological tuning. In this work, Li-assisted Ni-Co phosphate (Li-NCP) electrodes were grown directly onto nickel foam via a straightforward one-pot hydrothermal technique, and the influence of Li⁺ assistance on the structural, morphological, and electrochemical properties was studied in detail. Structural tuning and variations in the local coordination environments resulting from Li⁺-assisted hydrothermal synthesis were analyzed using XRD and FTIR spectroscopy. The morphological tuning of the electrode from stacked platelets to flower-like structures made up of interconnected needle-like nanostructures was observed by FESEM. Among all the electrodes fabricated in this study, the Li-2 electrode showed exceptional electrochemical performance, with areal capacitances of 10,828 mF cm^-2 at 3 mA cm^-2 and 4144 mF cm^-2 at 20 mA cm^-2. The charge-transfer resistance determined by EIS was extremely low (0.0571 Ω), indicating superior charge-transfer kinetics. The optimized electrode retains 70% of its capacitance after 5000 cycles. A hybrid Li-2//graphite solid-state supercapacitor worked stably within a 1.2 V potential window, and two devices in series successfully powered a red LED, demonstrating the practical potential of the developed electrode for advanced energy storage applications.