Two Dimensional Silicene Nanosheets: A New Choice of Electrode Material for High-Performance Supercapacitor

Two dimensional (2D) nanomaterials, including graphene, layered double hydroxides, layered transition metal dichalcogenides, and Mxenes, have demonstrated versatility in the fields of bioengineering, sensor, energy storage and conversion by virtue of unique mechanical, thermal, optical, and electrical properties. Nevertheless, integrating silicon-based materials into high-performance energy devices is relatively scarce and highly appreciable because of the challenging production technology. Herein, we reported that silicene was triumphantly assembled into a high-voltage symmetric supercapacitor, which possesses a wide operating potential window (0-3 V), a maximum specific capacitance of 0.41 mF cm^-2, a high energy density of 1.22 mJ cm^-2, a high power density of 0.49 mW cm^-2, and an excellent cycling stability of 96.6% capacitance retention after 10 000 cycles. The comprehensive performance of the silicene high-voltage symmetric supercapacitor is superior to that of the reported silicon-based materials. First-principles calculations reveal that monolayer or few-layer silicene with shorter ion diffusion pathways and higher utilization efficiency of active sites improves ion transport and electron transfer kinetics on the surfaces. To the best of our knowledge, it is the first time that silicene has been applied to the field of supercapacitors. This work will open up new horizons toward the material science research of electrochemical energy devices as well as help to promote the development of the high-performance supercapacitor industry.