Binder- and Additive-Free Electrophoretic Deposition of Solvothermally Synthesized Nickel–Cobalt Layered Double Hydroxide for High-Performance Asymmetric Solid-State Supercapacitor

Due to their excellent electrochemical properties, transition-metal-based layer double hydroxides (LDH) are emerging as electrode materials for efficient energy storage and conversion applications. Herein, we present a straightforward approach for electrode fabrication via the electrophoretic deposition (EPD) method of solvothermally synthesized bimetallic NiCo-LDH without using any additive or binder. The fabrication of electrodes using EPD is demonstrated to be superior to conventional drop-cast deposition (DCD). Notably, the EPD technique yields a superior specific capacitance (Cs) of 1470 F/g, i.e., a 144% improvement over the electrode fabricated using the DCD technique (602 F/g) at 2 A/g with NiCo-LDH. The electrochemical impedance spectroscopy confirmed favorable charge transport with NiCo-LDH deposited via EPD. The flower-like morphology of NiCo-LDH nanosheets has an enhanced specific surface area of 100 m2/g, providing more electrochemically active sites that exhibit higher Cs values compared to Ni-LDH (1250 F/g) and Co-LDH (850 F/g) fabricated with EPD. The fabricated solid-state asymmetric supercapacitor device with NiCo-LDH//AC electrode exhibits an energy density of 43.7 Wh/kg with a power density of 750 W/kg. The excellent durability of the device is confirmed by retaining ∼80% capacitance after 5000 charge–discharge cycles at 20 A/g. The superior energy storage capacity of the synthesized NiCo-LDH is attributed to the optimal structural combination and the EPD electrode fabrication.