Layered MnO2@PDA as cathode material toward high-performance aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) can benefit from a deep understanding of the electrochemical reaction mechanism of cathode materials, which can assist in resolving issues such as cathode dissolution and electrostatic interactions. We reported a straightforward two-step synthesis of polydopamine coated MnO₂ (MnO₂@PDA) and revealed the energy storage mechanisms in AZIBs. The layered structure of MnO₂ creates a generous passage for the insertion of H⁺/Zn²⁺ ions. Simultaneously, the plethora of functional groups within PDA exerts a robust desolvation effect, bolstering the transfer rate of H⁺/Zn²⁺. This effect significantly enhances the overall efficiency and performance of cathode. The AZIBs, incorporating MnO₂@PDA cathode material, consequently exhibit a satisfactory cycling capacity (412 mAh g⁻¹ at 0.1 A g⁻¹) and a superb specific energy (561.6 Wh kg⁻¹ at 136.34 W kg⁻¹). This work provides a new path for design strategies and catalytic mechanisms of MnO₂@PDA cathode.