According to a study published in Small, researchers led by Prof. HU Linhua from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences found that the electrochemical properties of NH₄V₄O₁₀ can be successfully improved by introducing oxygen vacancies.

"The introduction of oxygen vacancies accelerates the ion and charge transfer kinetics, reduces the diffusion barrier of zinc ions, and establishes a stable crystal structure during zinc ion (de-intercalation)," said LI Zhaoqian from the team.

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention among energy storage devices. Vanadium-based compounds have been identified as promising cathode materials for aqueous zinc-ion batteries due to their high specific capacity. However, the low intrinsic conductivity and sluggish Zn²⁺ diffusion kinetics seriously hinder their further practical application.

In this study, the researchers develop a facile hydrothermal approach to introduce oxygen vacancies into NH₄V₄O₁₀ nanobelts (referred to as VO-NVO) as a cathode material for high performance.

The generation of oxygen vacancies in the NVO lattice can accelerate the ion and charge transfer kinetics, reduce the diffusion barrier of zinc ions, and establish a stable crystal structure during zinc ion (de-intercalation). This defect engineering also facilitates the enhancement of the surface capacitive contribution of NVO due to the higher electrochemical surface reactivity and lower number of formation electrons required.

As a result, the obtained VO-NVO cathode exhibits a remarkable capacity, exceptional rate capability and ultra-long cycle stability.

This method of introducing oxygen vacancies provides an idea for solving the problem of high-performance AZIB cathodes, according to the team.

Electrochemical Reaction Kinetics and density functional theory calculations. (Image by LI Zhaoqian)

Charge Storage Mechanism. (Image by LI Zhaoqian)