Sulfur-Doped Nickel–Cobalt Double Hydroxide Electrodes for High-Performance Asymmetric Supercapacitors
Zhicheng Shi, Juncheng Zhu, Zhong Li, Qindan Xiao, Jiliang Zhu
Abstract
In this work, an effective strategy was proposed to improve the electrochemical performance of nickel–cobalt layered double hydroxide (NiCo-LDH) by controlling the sulfur doping. The prepared NiCo-LDH material with a 7.5% mol S dopant compared to LDH (NiCo-LDH-S7.5) possesses a unique nanosheet spherical structure, so it can expose more active sites and make better contact with the electrolyte. The synthesized NiCo-LDH-S7.5 has an outstanding specific capacitance of 2417.7 F g–1 at 1 A g–1. Meanwhile, the sulfur dopant significantly improves the electrical conductivity of the electrode material, enhancing the rate performance of the electrode. When the current density increases from 1 to 20 A g–1, the electrode retains a specific capacitance of 81.8%. In addition, we also manufactured an asymmetric supercapacitor using NiCo-LDH-S7.5 and activated carbon as positive and negative electrodes, respectively. Also, it exhibits an exceptionally high energy density of 73.54 Wh kg–1 at a power density of 375 W kg–1 and excellent cyclic stability (90.19% performance remained after 5000 cycles at 2 A g–1). The supercapacitor has been tested to power 88 LEDs (∼2 V) in series, indicating great potential for practical application.