China Nonferrous Metallurgy

Aqueous zinc-ion batteries have broad application prospects in the field of large-scale energy storage due to their low cost, high safety and environmental friendliness. Thus, it is of vital importance to develop high-performance cathode materials. In this paper, a simple hydrothermal method was used to prepare (NH₄)₂V₄O₉ cathode materials. The structure and zinc storage performance of these materials synthesized under different pH values were investigated. It is found that the pH value has a significant influence on the crystallinity and phase purity of the material. The specimen obtained at pH=45 demonstrates the highest crystallinity and phase purity, showing the optimal electrochemical properties. Its reversible capacities at current densities of 01, 02, 05, 1, 2 and 5A·g^-1 are 3851, 3388, 2767, 23200, 1995 and 1581mAh·g^-1, respectively. A discharge capacity of 1218mAh·g^-1 is still maintained after 5000 cycles at a high current density of 5A·g^-1 as well as the capacity retention rate of 865%. The results show that the excellent cycling stability and rate capability of pure (NH₄)₂V₄O₉ electrode can benefit from the “pillar” effect of NH⁺₄ between the VO layers and the high pseudo capacitive contribution rate at a large current density.