MnO2/Mn2O3 with self-triggered oxygen-defects for superior pseudocapacitive energy storage

Though tremendous efforts are devoted on structure engineering, most of Mn oxides show low capacity under wide work voltage actually caused by the limitation of sluggish reaction kinetics and inferior conductivity. Herein, we present an unprecedented self-improvement in electronic structure and Mn ions redox activity of MnO2/Mn2O3, carried out by a new mechanism of multiple Mn ions redox reaction with self-triggered oxygen-defect (Vo). It is disclosed that the MnO2/Mn2O3 electrode mainly indicates capacitive-like surface redox reaction between Mn3+ and Mn4+ when operating within 0-1.2 V, which evolves into an adjustable multiple redox reactions of Mn2+, Mn3+ and Mn4+ accompanied with the self-generation of abundant Vo after changing the lower cut-off work potential (LCWP) from 0 to -0.3 V. Theoretical and experimental results demonstrate the rich Vo in active structure induces new electronic states and electron redistribution between Mn and O, which increase total charge storage more than two-folds to 786. 7 C g(-1) (1 A g(-1)) by promoting multiple Mn ions redox reactions. During assembling MnO2/Mn2O3-based pseudocapacitor, a designed four-electrode system reveals fast reaction kinetics of anode assigns MnO2/Mn2O3 with more wide effective work potential, guiding the effective enhancement of energy density by selecting MoS2 as the anode.

Automated summary

Despite great efforts in structural engineering, most Mn oxides have low capacity due to sluggish reaction kinetics and poor conductivity under wide work voltage. A self-improvement in electronic structure and Mn ions redox activity of MnO2/Mn2O3 is achieved by a new mechanism of multiple Mn ions redox reaction with self-triggered oxygen-defect (Vo). The rich Vo induces new electronic states and electron redistribution between Mn and O, promoting multiple Mn ions redox reactions and increasing total charge storage by more than two-folds to 786.7 C g(-1) (1 A g(-1). A four-electrode system shows fast reaction kinetics and guides effective enhancement of energy density by selecting MoS2 as the anode.