Designing locally ordered structures of MnO2 for high-rate cathodes in aqueous zinc-ion batteries†

Abstract

Although significant efforts have been devoted to Mn-based oxide electrodes in aqueous zinc ion batteries (AZIBs), achieving high power density is hindered by their intrinsic properties, such as sluggish ion diffusion kinetics and inadequate electronic conductivity. This study presents a design for a locally ordered crystalline structure to address these challenges. The design incorporates locally ordered MnO₂ (LOM) nanocrystallites, which create locally ordered regions with long-range amorphous structures, shortening ion transfer pathways. The structure can also induce defects, interfaces and lattice distortions, enhancing the number of active sites for ion storage and facilitating ion transfer. Notably, the electronic conductivity of LOM is further enhanced by introducing new energy levels stemming from the heterointerface created between locally ordered and disordered regions. As a result, the rate performance of AZIBs is significantly improved, delivering a capacity of 146 mA h g⁻¹ at 10 A g⁻¹. This structure design represents a promising advancement in developing high-rate performance electrode materials for AZIBs.