Fast Fabrication of High-Performance Supercapacitor Electrodes Based on Two-Dimensional Trimetallic Zinc Manganese Cobalt-Layered Double Hydroxide Nanosheets Derived from Metal-Organic Frameworks

Abstract

Layered double hydroxides (LDHs) synthesized via hydrothermal methods often suffer from restacking, leading to a reduced specific surface area and fewer active sites. Additionally, the use of binders in the electrode preparation process can introduce dead volumes, which, in turn, decrease the capacitance. To address this issue, we present the rational design of binder-free electrodes made of trimetallic zinc manganese cobalt-layered double hydroxide (ZnMnCo-LDH) nanosheets on nickel foam (NF) that are derived from metal-organic frameworks (MOFs). Cobalt-based MOF nanoflakes grow on NF, and ion exchange reactions produce the trimetallic ZnMnCo-LDH. The synthesis process of trimetallic ZnMnCo-LDH electrodes involves varying amounts of zinc and manganese precursors and synthesizes bimetallic layered double hydroxides (LDHs) using similar experimental conditions for performance comparison. At the optimized conditions, the ZnMnCo-LDH electrode exhibits the highest specific capacitance (CF) of 1508 F/g at 20 mV/s. Furthermore, we fabricate an asymmetric supercapacitor (ASC) with a ZnMnCo-LDH positive electrode and an Ultraphene negative electrode. This ASC provides excellent energy storage performance with an appreciable energy density of 40.1 Wh/kg and a power density of 700 W/kg. Also, superior cycling stability with a CF retention of 95% and a Coulombic efficiency of 94% is achieved after 10,000 charge/discharge cycles.