Rational design of porous nest-like basic Co-Ni carbonates on carbon cloth with optimized electrode process for efficient electrochemical energy storage

Abstract

Bimetallic compound-based electrodes are composed of two different metallic elements with high electrical conductivity, electrochemical activity, and considerable theoretical capacity for supercapacitors. However, conventionally grown nickel-cobalt-based compounds tend to aggregate, greatly reducing the material surface's charge diffusion channels. Hence, by a series of processes to optimize the morphology and crystal structure, the porous nest-like Ni_0.75Co_0.25(CO₃)_0.125(OH)₂·0.38 H₂O (NCCO-2) derived from cobalt metal-organic frameworks (Co-MOF) are successfully anchored on activated carbon cloth (ACC). The unique microstructure with high specific surface area and abundant microstructure enables the NCCO@ACC-2 self-supported positive electrode with enhanced kinetics and optimized charge storage behavior, thus presenting an extraordinary capacitance of 7.18 F cm⁻² and superior electrochemical stability. To assemble an asymmetric supercapacitor (ASC), nitrogen-doped ACC (NAC) is prepared as the negative electrode. Its rough surface has a large number of oxidized functional groups, graphite microstructure and defect sites for charge transfer and ion adsorption, thereby also achieving a capacitance of 8.18 F cm⁻². The NCCO@ACC-2//NAC ASC exhibits outstanding energy density (1.09 mWh cm⁻²), power density (17 mW cm⁻²) and cycle stability and rate performance. This study provides a new method for preparing high-specific-capacity nickel-cobalt-based composite materials through nanoscale structure control, and the stable and efficient strategy has broad application prospects.