Silicon-based materials have attracted considerable interest for the development of energy storage devices because of their ease of integration with the existing silicon semiconductor technology. Herein, we have prepared siloxene sheets—a two-dimensional (2D) silicon material—and investigated their energy storage properties via fabrication of a symmetric supercapacitor (SSC) device containing 0.5 M tetraethylammonium tetrafluoroborate as the electrolyte. The formation of 2D siloxene sheets functionalized with oxygen, hydrogen, and hydroxyl groups was confirmed through X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and laser Raman mapping analyses. Cyclic voltammetric studies of the siloxene SSC device revealed the presence of pseudocapacitance in the siloxene sheets that arose from an intercalation/deintercalation phenomenon. The galvanostatic charge–discharge profiles of the device displayed sloped symmetric triangular curves with a maximum specific capacitance of 2.18 mF cm−2, high energy density of 9.82 mJ cm−2, good rate capability, and excellent cycling stability of 98% capacitance retention after 10000 cycles. The siloxene SSC device delivered a maximum power density of 272.5 mW cm−2, which is higher than those of other silicon- and carbon-based SSCs, highlighting their potential for application in energy storage.
