Honeycomb-like δ-MnO2/NCP integrated cathode for advanced aqueous zinc-ion batteries

Abstract

The short cycle life and weak electrical conductivity of manganese dioxide (MnO2) are critical limitations for its application as cathode material in aqueous zinc ion batteries (AZIBs). Herein, we introduce the honeycomb-like δ-MnO2/NCP integrated cathodes, which are developed by the δ-MnO2 nanosheet in situ growing on hollow Ni@C microsphere (denoted as NBM). The hollow microsphere is self-assembled from the graphene carbon layer wrapping Ni nanoparticles (denoted as NCP) by pyrolyzing nickel-based metal-organic frameworks (MOFs). The enhanced NBM electrodes deliver a 352 mAh g − 1 ultra-high specific capacity at 0.1 A g − 1 while maintaining a 125 mAh g − 1 specific capacity at 2 A g − 1. With 81% capacity retention and 99.4% high average coulomb efficiency after 2000 cycles at 2 A g − 1, the NBM electrodes exhibit exceptional cycling stability. Experimental and theoretical results show that NBM electrodes possess excellent electrochemical properties, which are attributed to the high specific surface area of the honeycomb structure, enhanced electrical conductivity, suitable adsorption energy, and low diffusion energy barrier. Moreover, the hollow microsphere structure of NCP promotes fast diffusion of ion/electron and relieves structure collapse of δ-MnO2. This work suggests a promising avenue for developing advanced AZIBs cathode materials.