Ni‐MnO2/Graphene as Cathode Material for Super‐Capacity Aqueous Rechargeable Zn‐Ion Battery

Abstract

The development of cathode materials is an effective way to improve the electrochemical performance of zinc‐ion batteries (ZIBs). Herein, Ni2+‐doped MnO2/graphene nanocomposites (denoted as NMO/rGO) are synthesized by hydrothermal and mechanical ball milling methods as cathode materials for ZIBs. The NMO/rGO electrode shows a super capacity, excellent rate performance, and good cycling stability. The specific discharge capacity can reach 431.5 mAh g−1 at 0.1 A g−1. Moreover, the specific capacity retention rate is 56% after 2200 cycles at 2 A g−1. The excellent electrochemical performance is attributed on the one hand to the stable insertion of Ni2+, which affects the MnO bond and weakens the electrostatic interaction between MnO2 and Zn2+ and on the other hand, the strong interaction (MnOC bond) is formed between NMO and rGO through ball milling, which improves the electrical conductivity and mitigates the volume expansion. Notably, mechanical ball milling can also introduce oxygen vacancies for MnO2, thus increasing the active sites for redox reactions and significantly improving the electrochemical performance of the materials.