Copper ions-intercalated manganese dioxide self-supporting mesoporous carbon electrode for aqueous zinc-ion batteries†

In aqueous zinc-ion batteries (AZIB), layered manganese dioxide (δ-MnO₂) is considered to be a suitable cathode material due to its high theoretical capacity, suitable operating voltage and Zn²⁺/H⁺ co-intercalation mechanism. However, the strong coulomb interaction between Zn²⁺ and δ-MnO₂ results in the slow diffusion dynamics of Zn²⁺ in the electrochemical process, which affects the structural stability of the cathode. Herein, we report a structural design that stabilizes the δ-MnO₂-layered structure by pre-intercalation of Cu²⁺ to expand the layer spacing, and thus improve H⁺-transfer kinetics. Compared with the bulk δ-MnO₂, the modified cathode showed excellent electrochemical performances, including a highly reversible capacity of 280 mA h g⁻¹ at 1 A g⁻¹ and 62.5% capacity retention after 1500 cycles at 5 A g⁻¹. The results shown above confirmed the possibility of increasing the capacity contribution of H⁺ through structural design, and provides a novel idea for the development of high-performance cathode materials.

Keywords: Aqueous zinc-ion batteries; Layered manganese dioxide; Pre-intercalation; Self-supporting electrode.