Suppressing Charge Disproportionation of MnO2 Cathodes in Rechargeable Zinc Ion Batteries via Cooperative Jahn-Teller Distortion

Abstract

MnO2 is a promising candidate material as intercalative cathodes in rechargeable aqueous zinc ion batteries (ZIBs). It is renowned for its low cost, minimal toxicity, and high energy density; however, severe capacity fading from the dissolution of MnO2 remains a critical challenge that must be overcome to achieve improved cycling performance. In this study, surface coating of MnO2 with dicyandiamide is proposed as a method to significantly reduce the dissolution of MnO2 by addressing the fundamental cause of MnO2 dissolution, which is the charge disproportionation (CD) reaction of Mn3+. Experimental and computational methods are used to demonstrate that the surface coating triggers cooperative Jahn-Teller distortion of Mn4+ to alleviate lattice distortion and impede the CD reaction. Thus, the cycling stability of MnO2 is significantly improved, exhibiting 170 % higher capacity in comparison with pristine MnO2 and 99.9 % coulombic efficiency under a 1C rate condition. Resolving the orbital degeneracy with surface modification will open a new and prospective path for superior cycling performance of MnO2-based ZIBs.