Zinc ion stabilized MnO2 nanospheres for high capacity and long lifespan aqueous zinc-ion batteries

Abstract

Rechargeable zinc-ion batteries based on Zn/MnO₂ in neutral aqueous electrolytes are promising for grid-scale energy storage applications owing to their favorable merits of high safety, low cost and environmental benignity. However, MnO₂ cathodes are subjected to the challenging issues of poor cyclability and low rate capability. Herein, we report a facile chemical method for the preparation of mesoporous MnO₂ flower-like nanospheres with the layered framework stabilized by hydrated Zn²⁺ pillars. The MnO₂ cathode could deliver a reversible specific capacity of 358 mA h g⁻¹ at 0.3 A g⁻¹ after 100 cycles, a high rate capacity of 124 mA h g⁻¹ at 3.0 A g⁻¹, and excellent operating stability over 2000 cycles. Structural and morphological investigations demonstrate an energy storage mechanism of co-insertion/extraction of H⁺ and Zn²⁺ accompanied by deposition/dissolution of zinc sulfate hydroxide hydrate flakes on the electrode surface. The superior electrochemical performance makes the zinc ion stabilized MnO₂ promising for high capacity and long lifespan zinc-ion batteries.