A review on solutions to overcome the structural transformation of manganese dioxide-based cathodes for aqueous rechargeable zinc ion batteries

The recent significant growth in aqueous rechargeable zinc ion batteries (ZIBs) as a replacement of lithium-ion (LIBs) and sodium-ion batteries (SIBs) is exceptionally feasible due to its high safety, environment friendliness, highly available resources and cost-efficiency. However, it is still a big challenge to develop a suitable cathode material for Zn2+ intercalation. This review exhibits the recent progress of manganese oxide (MnO2) as cathode material for ZIBs. Despite the significant use of MnO2 as a cathode for ZIBs, the numerous challenges such as dendrite formation, hydrogen evolution, formation of non-conductive by-products and metal dissolution along with undesirable side reactions are still under debate, which needs to be simply explained. This review summarizes all the mechanisms involved with different polymorphs of MnO2 cathode including an analysis of the issues mentioned above faced by cathodes, anodes and electrolytes. In addition, to overcome these issues, the feasible solutions such as surface coating, composite formation, defect engineering have also been discussed. Furthermore, a detailed study on electrolytes as well as anode-based modifications and suggestions to enhance the electrochemical performances of aqueous ZIBs were also reviewed.