The function of phenylphosphonic acid on diversifying the property of manganese dioxide applied in the aqueous zinc-ion battery

The manganese-based rechargeable aqueous zinc-ion batteries have garnered significant attention due to their advantageous properties including high theoretical specific capacity, low cost, simple preparation, and environmental friendliness. The properties of the manganese-based cathode material depend strongly on its crystalline structure, the particle size, the morphology, and the functional elements, which plays a crucial role in further determining the electrochemical performance of the battery system. In this study, we disclose a distinctive function of phenylphosphonic acid (H2PP) in diversifying the intrinsic properties and electrochemical performance of manganese dioxide (MnO2) as the cathode material in the aqueous zinc-ion battery. By adding H2PP during preparation, the growth of MnO2 can be induced to form γ-MnO2 and α-MnO2, depending on the amount of H2PP used, in contrast to β-MnO2 prepared without the addition of H2PP. Moreover, the morphology of the cathode material can also be differentiated. Additionally, MnO2 can be functionalized by P-based groups from H2PP. By incorporating 0.5 % H2PP, a porous γ-MnO2 with a large specific surface area and high ionic conductivity is formed, which results in the battery exhibiting a high specific capacity of 225 mAh/g at the current density of 1 A/g, along with decent cycling performance.