Electrochemical characterization of hollow urchin-like MnO2 as high-performance cathode for aqueous zinc ion batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) based on MnO2 cathode and Zn anode has attracted an increased attention for energy storage for their low cost, high safety and environmental friendliness. However, the essentially poor conductivity and unstable structure change of MnO2 cathode during electrochemical reaction usually lead to low discharge capacity and rapid fading for AZIBs. To alleviate these problems, a hollow urchin-like MnO2 was synthesized by a modified one-step hydrothermal method. The as-proposed unique morphology with large surface can effectively shorten the ion diffusion distance and alleviate the collapse of the structure. The urchin-like MnO2 cathode shows a high reversible specific capacity of 324.9 mAh g−1 at 0.1 A g−1 (0.32C). Meanwhile, a long-term stability up to 5000 cycles with a retained capacity of 124 mAh g−1 at a high current density of 1.5 A g−1 (5C) is obtained, which is obviously superior to a common spherical MnO2. Ex-situ analysis reveals a H+ and Zn2+ co-insertion reaction mechanism for the as-obtained cathode. The remarkably electrochemical performance suggests the hollow urchin-like MnO2 a promising cathode for AZIBs.