Trigger a multi-electron reaction by tailoring electronic structure of VO2 toward more efficient aqueous zinc metal batteries

Abstract

VO₂ (B) is recognized as a promising cathode material for aqueous zinc metal batteries (AZMBs) owing to its remarkable specific capacity and its unique, expansive tunnel structure, which facilitates the reversible insertion and extraction of Zn²⁺. Nonetheless, challenges such as the inherent instability of the VO₂ structure, poor ion/electron transport and a limited capacity due to the low redox potential of the V³⁺/V⁴⁺ couple have hindered its wider application. In this study, we present a strategy to replace vanadium ions by doping Al³⁺ in VO₂. This approach activates the multi-electron reaction (V⁴⁺/V⁵⁺), to increase the specific capacity and improve the structural stability by forming robust V⁵⁺O and Al³⁺O bonds. It also induces a local electric field by altering the local electron arrangement, which significantly accelerates the ion/electron transport process. As a result, Al-doped VO₂ exhibits superior specific capacity, improved cycling stability, and accelerated electronic transport kinetics compared to undoped VO₂. The beneficial effects of heterogeneous atomic doping observed here may provide valuable insights into the improvement electrode materials in metal-ion battery systems other than those based on Zn.

Keywords: Aqueous zinc metal battery; Electronic structure; Multi-electron reaction; VO(2).