Cobalt–Nickel Mixed Metal Sulfide Hollow Nanocages with Enhanced Surface-Induced Capacitive Storage for Hybrid Supercapacitor
Juncheng Qi, Haoyan Duan, Zhiling Peng, Jun Wang, Boxiang Ma, Zehui Yuan, Huifang Zhang
Abstract
Transition metal sulfides with hollow architecture are considered as important electrode materials in electrochemical supercapacitors owing to their high electrochemical activity and surface permeability. Here, we report an effective multistep strategy for synthesizing cobalt–nickel mixed metal sulfide (denoted as CoNiS) nanocages with well-defined interior voids. First, NiCo-LDH was synthesized through an ion-exchange reaction between ZIF-67 and Ni 2+ ions and then converted to CoNiS hollow nanocages through a sulfidation reaction. Depending on the ion-exchange reaction temperature, two types of CoNiS products with hollow nanocages and collapsed structures can be obtained. When evaluated as electrodes for supercapacitors, CoNiS hollow nanocages manifest improved electrochemical performance compared to the collapsed one, including a high capacity of 598.8 C g –1 at 1 A g –1, a capacity retention of 59.9%, and an outstanding cycle stability of 70.1% after 10,000 cycles. The electrochemical reaction kinetics indicate that the high capacity and rate capability of CoNiS hollow nanocages may be attributed to their much more surface-induced capacitive behavior. Moreover, a hybrid supercapacitor (HSC) constructed with hollow CoNiS can deliver a maximum energy density of 103.6 Wh kg –1 at a power density of 833.3 W kg –1, suggesting the potential of the novel CoNiS with a hollow nanocage morphology for high-performance supercapacitors.