A unique morphology and interface dual-engineering strategy enables the holey C@VO2 cathode with enhanced storage kinetics for aqueous Zn-ion batteries

Abstract

Sluggish transport kinetics and unstable host structure are major obstacles that impede the development of advanced cathode materials for high-performance aqueous Zn-ion batteries (AZIBs). In this work, we report the rational design of holey carbon-encapsulated vanadium dioxide nanobelts (denoted as holey C@VO₂) via a unique dual-engineering strategy combining the morphology and interface. As the cathode material for AZIBs, it can deliver a specific capacity of 386.9 mA h g⁻¹ at 0.2 A g⁻¹, as well as an excellent high-rate performance of 332 mA h g⁻¹ at 5 A g⁻¹ with capacity retention of 84.3% after 600 cycles. The reaction mechanism of the holey C@VO₂ electrode was systematically studied by combining in situ and ex situ technologies, which reveals the synergistic intercalation/de-intercalation behavior of H⁺/Zn²⁺, accompanied by the reversible formation/decomposition of a sheet-like by-product. Moreover, the study of in situ electrochemical impedance spectra also confirms the stable electronic transport process that occurs in the holey C@VO₂ electrode upon cycling. Therefore, the superior electrochemical performance of such an electrode should be mainly benefited from the efficient transport kinetics and abundant reaction sites. Such a unique strategy proposed in this work, as well as the systematic studies of the reaction mechanism is expected to not only provide scientific guidance for designing other advanced cathodes, but also pave the way to a deep understanding of the fundamentals of AZIBs.