Effect of annealing on the MnO2 cathodes for high-performance aqueous Zn-ion batteries.

Zinc ion batteries (ZIBs) are increasingly prominent due to their cost-effectiveness, abundance, environmental safety, mature processing methods, high volumetric energy density, and compatibility with aqueous electrolytes. However, a significant challenge lies in finding a suitable cathode material with high capacity and structural stability. Manganese dioxide (MnO 2) is a promising candidate for ZIB cathodes in aqueous systems, surpassing other metal oxides in potential. However, MnO 2 cathodes encounter challenges, including rapid capacity degradation and limited cyclic stability. Enhancing the structural stability of host materials during intercalation presents a significant avenue for increasing cathode capacity. In this study, we employed a hydrothermal method to synthesize MnO 2 , followed by annealing in an argon atmosphere at 300 °C for 4 h for MnO 2 -300 and 400 °C for 2 h for MnO 2 -400 to bolster its structural integrity. The properties of annealed samples MnO 2 -300 and MnO 2 -400 are compared with pristine samples (MnO 2 -P). Initially, XRD analysis is conducted to compare their structures, followed by a comparison of electrochemical properties, including Cyclic Voltammetry (CV) and charge-discharge analysis. MnO 2 -400 exhibits a higher initial capacity (149.3 mAhg−1 at 0.1 Ag-1) than MnO 2 -300 (129.0 mAhg−1 at 0.1 Ag-1) and MnO 2 -P (107.9 mAhg−1 at 0.1 Ag-1). An extended cycling test of up to 500 cycles also indicates that annealing MnO 2 in an Ar atmosphere enhances structural stability and capacity compared to the unannealed sample. [ABSTRACT FROM AUTHOR]