Conformal poly 3,4-ethylene dioxythiophene skin stabilized ε-type manganese dioxide microspheres for zinc ion...

Manganese dioxide (MnO₂) is an important active material for energy storage. Constructing microsphere-structured MnO₂ is key for practical application due to the high tapping density for high volumetric energy density. However, the unstable structure and poor electrical conductivity hinder the development of MnO₂ microspheres. Herein, Poly 3,4-ethylene dioxythiophene (PEDOT) is painted conformally on ε-MnO₂ microspheres to stabilize the structure and enhance the electrical conductivity via in-situ chemical polymerization. When used for Zinc ion batteries (ZIBs), the obtained material (named MOP-5) with high tapping density (1.04 g cm^-3) delivers a superior volumetric energy density (342.9 mWh cm^-3) and excellent cyclic stability (84.5% after 3500 cycles). Moreover, we find the structure transformation of ε-MnO₂ to ZnMn₃O₇ during the initial few cycles of charge and discharge, and the ZnMn₃O₇ provides more reaction sites for Zinc ions from analysis of the energy storage mechanism. The material design and theoretical analysis of MnO₂ in this work may provide a new idea for future commercial applications of aqueous ZIBs.