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The development of asymmetric supercapacitors (ASCs) with high power and energy density is greatly restricted by the low capacitance of the anode materials. V2O5 is a promising anode material with high theoretical capacity, but its low conductivity and high dissolution are not conducive to applications in energy storage. Herein, oxygen-vacancy PEDOT/V2O5 ultrathin nanosheets with a thickness of about 4.4 nm are fabricated by the oxidative polymerization of EDOT monomers on V2O5 nanosheets in the absence of other oxidants. The results of XPS and EPR confirm that the polymerization of PEDOT increases the oxygen vacancy concentration of V2O5. The PEDOT/V2O5 nanosheets exhibit a specific capacitance of 406 F g−1 at 2 mV s−1 and excellent cyclic stability in the mixed organic electrolyte of dimethyl carbonate and ethylene carbonate. The energy density of ASCs composed of PEDOT/V2O5 as the anode and activated carbon as the cathode reaches 65 W h kg−1 at a power density of 1490 W kg−1. This means that PEDOT/V2O5 has enormous potential in high-energy storage. [ABSTRACT FROM AUTHOR]

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. MoO3 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 MoO3 (OV‐MoO3/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 MoO3 can be controllably changed from thick nanobelts into ultrathin nanoflakes by adjusting the Ce doping concentration. And Ce doping in the OV‐MoO3 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‐MoO3/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‐MoO3/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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low crystallinity defect-rich NiO nanosheet array is constructed by electrochemical activation. • Electrochemical activation can finely regulate the structure of NiO nanosheet array. • Electrochemical activation increases the capacitance of NiO from 308 to 914 F g−1. • Soft-pack supercapacitor offers up to 38.5 Wh kg−1 energy density at 2700 W kg−1 power density. • The relationships of method, structure and performance is discussed in detail and proposed. Nickel oxide (NiO) with high theoretical capacity is considered a promising energy storage material, however, its actual capacitance and stability are unsatisfactory. In this work, a facile electrochemical activation is proposed to significantly improve the electrochemical performance of porous NiO nanosheet arrays on carbon cloth (CC) in-situ prepared by facile hydrothermal method and subsequent high-temperature calcination. Experimental characterization and density functional theory calculations have shown that this electrochemical activation process can introduce more oxygen vacancies and defects, reduce the crystallinity and nickel valence state of NiO, increase the structural looseness of the nanosheet array and electrical conductivity as well as adsorption energy for hydroxide. By utilizing these structural regulations, the specific capacitance of electrochemically activated NiO/CC is significantly enhanced from 308 to 914 F g−1. The soft-pack asymmetric supercapacitor offers a high energy density of 38.5 Wh kg−1 and exhibit an ultralong lifespan of up to 20,000 cycles with 96.2% capacitance retention. Such a soft-pack asymmetric supercapacitor illuminates different electronic devices, demonstrating enormous potential in practical applications. [ABSTRACT FROM AUTHOR]