Advanced Oxygen‐Vacancy Ce‐Doped MoO3 Ultrathin Nanoflakes Anode Materials Used as Asymmetric Supercapacitors with Ultrahigh Energy Density

Abstract Asymmetric supercapacitors (ASC) meet the high power and energy demand in energy storage devices; however, the low capacitance of the anode materials severely hinders the development of ASCs. MoO 3 with its high theoretical capacity is an ideal anode material, but its low electrical conductivity limits the application of capacitive energy storage. Herein, abundant oxygen vacancies Ce‐doped MoO 3 (OV‐MoO 3 /Ce) ultrathin nanoflakes anode materials with a thickness of 1.51‐2.01 nm are constructed by a simple hydrothermal method. It is found that the nanostructure of MoO 3 can be controllably changed from thick nanobelts into ultrathin nanoflakes by adjusting the Ce doping concentration. And Ce doping in the OV‐MoO 3 lattice can additionally introduce abundant oxygen vacancies without introducing Ce oxide and other impurities. Benefiting from the synergy of ample oxygen vacancies, high specific surface area, and accelerated ion diffusion and charge mobility, the optimized OV‐MoO 3 /Ce electrode achieves a high specific capacitance (1439.0 F g ‐1 at 2 mV s ‐1 and 1446.3 F g ‐1 at 5 A g ‐1 ) and good cycle stability. More impressively, the ASC assembled using optimized OV‐MoO 3 /Ce as anode materials can provide an ultrahigh energy density of 150.0 Wh kg ‐1 at a power density of 800 W kg ‐1 , and the practical demonstration of the assembled ASC device highlights its great potential for high energy storage.