Issues and opportunities of manganese-based materials for enhanced Zn-ion storage performances

Owing to the low cost and high safety, aqueous zinc-ion batteries (ZIBs) are one of the most attractive candidates to the post lithium-ion batteries. Among the reported cathode materials for ZIBs, manganese (Mn)-based materials hold high promise due to their abundant resources, various crystal structures, high operating voltages (>1.2 V) and decent reversible capacities (>200 mA h g⁻¹). However, Mn-based materials suffer poor cycling stability and rate capability. To address these obstacles, various strategies have been developed and some progress has been achieved. In this review, an overview on the structural influence in the energy storage mechanisms and the challenges of Mn-based materials for aqueous ZIBs was given, and four main strategies including Mn²⁺ addition in electrolyte, structural adjustment, functional modification and architecture construction, are emphasized and discussed. Moreover, we analyze the advantages and disadvantages of these strategies, provide new insights for the design of high-performance Mn-based ZIBs, and sort out the applications and future opportunities of ZIBs in flexible energy storage devices.