High-Energy-Density Asymmetric Supercapacitor Based on Free-Standing Ti<sub>3</sub>C<sub>2</sub>T<i><sub>X</sub></i>@NiO-Reduced Graphene Oxide Heterostructured Anode and Defective Reduced Graphene Oxide Hydrogel Cathode
Wei‐Wen Chen, Chunfeng Hao, Zenghui Qiu, Xin Zhang, Haijun Xu, Bingzhe Yu, Shaowei Chen
Abstract
The rational design of an asymmetric supercapacitor (ASC) with an expanded operating voltage window has been recognized as a promising strategy to maximize the energy density of the device. Nevertheless, it remains challenging to have electrode materials that feature good electrical conductivity and high specific capacitance. Herein, a 3D layered Ti3C2TX@NiO-reduced graphene oxide (RGO) heterostructured hydrogel was successfully synthesized by uniform deposition of NiO nanoflowers onto Ti3C2TX nanosheets, and the heterostructure was assembled into a 3D porous hydrogel through a hydrothermal GO-gelation process at low temperatures. The resultant Ti3C2TX@NiO-RGO heterostructured hydrogel exhibited an ultrahigh specific capacitance of 979 F g–1 at 0.5 A g–1, in comparison to that of Ti3C2TX@NiO (623 F g–1) and Ti3C2TX (112 F g–1). Separately, a defective RGO (DRGO) hydrogel was found to exhibit a drastic increase in specific capacitance, compared to untreated RGO (261 vs 178 F g–1 at 0.5 A g–1), owing to abundant mesopores. These two materials were then used as free-standing anode and cathode to construct an ASC, which displayed a large operating voltage (1.8 V), a high energy density (79.02 Wh kg–1 at 450 W kg–1 and 45.68 Wh kg–1 at 9000 W kg–1), and remarkable cycling stability (retention of 95.6% of the capacitance after 10,000 cycles at 10 A g–1). This work highlights the unique potential of Ti3C2TX-based heterostructured hydrogels as viable electrode materials for ASCs.