Synthesis of MnO₂@TiO₂ composite electrodes via hydrolysis and calcination for high stability zinc-ion batteries

Aqueous Zn/MnO₂ batteries have extensively attracted attentions for their superior comprehensive performance. However, the poor structural stability and dissolution of MnO₂ have seriously prevented its further development. Therefore, TiO₂ is introduced for coating MnO₂ to improve its electrochemical stability. Firstly, TiO₂ used as a protective layer could hamper the direct contact between the electrode and the electrolyte, and effectively inhibiting the dissolution of manganese. Secondly, TiO₂ has good mechanical strength to alleviate to the volume change of MnO₂ during the charge/discharge processes, which consolidates the stability of the electrode material. Finally, TiO₂ could improve the electrical conductivity of the composite material, achieving lower polarization and good electron/ion transport. As a result, Zn/MnO₂@TiO₂-2 exhibits extraordinary electrochemical performance with a rate capacity of 245.16 mAh g⁻¹ at 0.2 A g⁻¹ and maintains a capacity of 137.09 mAh g⁻¹ after 1000 cycles at 1 Ag⁻¹. Even at a high current density of 3 A g⁻¹, it has a capacity of 93.35 mAh g⁻¹ after 1500 cycles, and the capacity retention rate is 97.47%. This work provides the inspiration and foundation method for designing high-performance Zn/MnO₂ batteries.