Oxygen-Deficient β-MnO2@Graphene Oxide Cathode for High-Rate and Long-Life Aqueous Zinc Ion Batteries

Highlights The concurrent application of vacancy enrichment and surface coating in β-MnO 2 electrode can both improve the intercalation kinetics and inhibit the Mn dissolution. The oxygen-deficient β-MnO 2 @graphene oxide electrode delivers a reversible capacity of 129.6 mAh g −1 after 2000 cycles at 4C, outperforming the state-of-the-art MnO 2 -based cathodes. The excellent performance is rooted in the strong binding of graphene oxide on defective β-MnO 2 and the regulated structural evolution into the Zn x Mn 2 O 4 phase. Recent years have witnessed a booming interest in grid-scale electrochemical energy storage, where much attention has been paid to the aqueous zinc ion batteries (AZIBs). Among various cathode materials for AZIBs, manganese oxides have risen to prominence due to their high energy density and low cost. However, sluggish reaction kinetics and poor cycling stability dictate against their practical application. Herein, we demonstrate the combined use of defect engineering and interfacial optimization that can simultaneously promote rate capability and cycling stability of MnO 2 cathodes. β-MnO 2 with abundant oxygen vacancies (V O ) and graphene oxide (GO) wrapping is synthesized, in which V O in the bulk accelerate the charge/discharge kinetics while GO on the surfaces inhibits the Mn dissolution. This electrode shows a sustained reversible capacity of ~ 129.6 mAh g −1 even after 2000 cycles at a current rate of 4C, outperforming the state-of-the-art MnO 2 -based cathodes. The superior performance can be rationalized by the direct interaction between surface V O and the GO coating layer, as well as the regulation of structural evolution of β-MnO 2 during cycling. The combinatorial design scheme in this work offers a practical pathway for obtaining high-rate and long-life cathodes for AZIBs.