Ultrafast Na-Ion Storage in Amorphization Engineered Hollow Vanadium Oxide/MXene Nanohybrids for High-Performance Sodium-Ion Hybrid Capacitors.

Abstract

Sodium ion hybrid capacitors (SIHCs) address the high power and energy requirements in energy storage devices but face significant challenges arising from the slow kinetics and cycling instability of the anode side. Introducing atomic disorder and employing structural engineering in anode materials proves to be effective strategies for achieving rapid charge storage. Here, it is demonstrated that N-doped MXene encapsulated amorphous vanadium oxide hollow spheres (VOx@N-MXene HSs) offer multidirectional open pathways and sufficient vacancies, enabling reversible and fast Na+ insertion/extraction. Machine learning potentials, coupled with molecular simulation techniques, confirm the presence of more abundant pores within the amorphous vanadium oxide (VOx) structure. The simulation of the charging/discharging process elucidates the authentic reaction path and structural evolutions of the VOx@N-MXene HSs, providing sufficient insight into the atomic-scale mechanisms associated with these structural superiorities. The full SIHCs devices demonstrate a high energy density of 198.3 Wh kg-1, along with a long-term cycling lifespan of 8000 cycles. This study offers valuable strategies into the intricate design and exploration of amorphous electrodes, contributing to the advancement of next-generation electrochemical energy devices.