Porous Fe2O3 nanospheres anchored on activated carbon cloth for high-performance symmetric supercapacitors

Metal oxides with nanostructures are promising electrode materials for supercapacitors, however, their cycling stability and rate performance still need to be improved for practical applications. To promote a device performance, it is important to develop an advanced electrode material as well as to design superior electrode architecture. Herein, porous Fe2O3 nanospheres anchored on activated carbon cloth (Fe2O3@ACC) is prepared as an excellent electrode material, which exhibits a large area specific capacitance up to 2775 mF cm−2 in 3 M LiNO3 between −0.8 and 0 V versus SCE. The symmetric structured supercapacitor assembled by two pieces of Fe2O3@ACC electrodes achieves 1.8 V operating voltage in 3 M LiNO3 aqueous electrolyte and area specific capacitance of 1565 mF cm−2 with excellent cycling stability, with 95% of initial capacitance retained after 4000 cycles, indicating fast ion-involved redox reactions on its surfaces. The Fe2O3@ACC symmetric supercapacitor can deliver an energy density of 9.2 mWh cm−3 at a power density of 12 mW cm−3 and an energy density of 4.5 mWh cm−3 at a power density of 204 mW cm−3. Li ion adsorption and diffusion mechanism on the (100) and (110) facets of Fe2O3 are explained by the calculations of density functional theory. The facile synthesis method and superior performance of the Fe2O3@ACC composite make it promising as an ideal electrode material for high-performance symmetric supercapacitors.