Extracting oxygen anions from ZnMn2O4: Robust cathode for flexible all-solid-state Zn-ion batteries

The pursuit of superb aqueous Zn-ion batteries (ZIBs) has driven the focus on solving their cathode limit. This study provides a readily accessible approach toward designing high-capacity ZnMn2O4 cathode by extracting oxygen anions. Experimental and computational results revealed the electronic conductivity, the Zn2+ diffusion kinetics, and the energy barrier of Zn mobility were well tailored by oxygen defects. The fabricated oxygen-deficient ZnMn2O4 cathode with the structural protection of conductive poly (3, 4-ethylenedioxythiophene) exhibited an outstanding capacity of 221 mA h g−1 at 0.5 mA cm−2, representing a state-of-the-art of current ZIBs cathodes. Moreover, a flexible and all-solid-state ZIBs was demonstrated, which delivered a superior energy density of 273.4 W h kg−1. Considering the new understanding about oxygen defects and the innovative concept of flexible ZIBs, this study is hoped to provide insightful guide for eco-friendly and portable energy storage systems.