Zinc ion stabilized MnO2 nanospheres for high capacity and long lifespan aqueous zinc-ion batteries
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 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 mAh g-1 at 0.3 A g-1 after 100 cycles, a high rate capacity of 124 mAh 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+ accompanying with deposition/dissolution of zinc sulfate hydroxide hydrate flakes on the electrode surface. The superior electrochemical performance enables the zinc ion stabilized MnO2 to hold a promise for high capacity and long lifespan zinc-ion batteries.