Vanadium and Niobium MXenes-Bilayered V2O5 Asymmetric Supercapacitors

MXenes offer high metallic conductivity and redox capacitance that are attractive for high-power, high-energy storage devices. However, they operate limitedly under high anodic potentials due to irreversible oxidation. Pairing them with oxides to design asymmetric supercapacitors may expand the voltage window and increase the energy storage capabilities. Hydrated lithium preintercalated bilayered V2O5 ( delta-LixV2O5 center dot nH(2)O) is attractive for aqueous energy storage due to its high Li capacity at high potentials; however, its poor cyclability remains a challenge. To overcome its limitations and achieve a wide voltage window and excellent cyclability, it is combined with V2C and Nb4C3 MXenes. Asymmetric supercapacitors employing lithium intercalated V2C (Li-V2C) or tetramethylammonium intercalated Nb4C3 (TMA-Nb4C3) MXenes as the negative electrode, and a delta-LixV2O5 center dot nH(2)O composite with carbon nanotubes as the positive electrode in 5 m LiCl electrolyte operate over wide voltage windows of 2 and 1.6 V, respectively. The latter shows remarkably high cyclability-capacitance retention of approximate to 95% after 10 000 cycles. This work highlights the importance of selecting appropriate MXenes to achieve a wide voltage window and a long cycle life in combination with oxide anodes to demonstrate the potential of MXenes beyond Ti3C2 in energy storage.

Automated summary

MXenes offer high conductivity and capacitance, which are attractive for energy storage devices. However, their operation is limited under high anodic potentials due to irreversible oxidation. Pairing them with oxides in asymmetric supercapacitors can expand the voltage window and increase energy storage capabilities.