Mn²⁺-doped (NH₄)₂V₄O₉ cathode materials for highly stable aqueous zinc-ion batteries

Due to their high specific capacity, ammonium vanadate salts are commonly utilized as cathode materials for aqueous zinc-ion batteries (AZIBs). However, their inferior efficiency and rate performance have hindered widespread adoption. In order to address these issues, we developed evenly distributed hybrid nanosheets (NVM) of (NH₄)₂V₄O₉ and MnV₂O₆ by introducing manganese ions into (NH₄)₂V₄O₉ through the hydrothermal technique. The results show that AZIB exhibits outstanding rate performance, stable cycle performance, and good efficiency characteristics when NVM as electrode materials. The AZIB has a high specific capacity of 500 mAh g⁻¹ at a current density of 0.1 A·g⁻¹. And it maintains a specific capacity of 350 mAh g⁻¹ after 100 cycles at 1 A·g⁻¹. It exhibits good stable cycle performance, the specific capacity is 140 mAh g⁻¹ after 1000 cycles at 5 A·g⁻¹, retaining 98% of its initial capacity. The addition of manganese ions can reduce the electrode’s diffusion impedance and increase its diffusion coefficient, resulting in a lower voltage window of 0.13 V. The large capacity and high energy efficiency of NVM materials make the battery more widely used in practical applications.