Scalable gas-phase synthesis of 3D microflowers confining MnO2 nanowires for highly-durable aqueous zinc-ion batteries

Abstract

Beneficial from high specific capacity and wide potential window, manganese dioxide (MnO2) as cathode material holds great promise in aqueous Zn-ion batteries (ZIBs). However, the bottleneck of MnO2 cathodes is their capacity fading and structural degradation during cycles. Herein, an environmentally benign and scalable gas-phase spray drying strategy is put forward to obtain 3D microflowers confining MnO2 nanowires (MNWs) in conductive graphene nanosheets (GNSs). Remarkably, 3D microflowers not only provide high connectivity for rapid ions/electrons transfer, but also maintain the structural integrity owing to the GNSs as robust skeleton, while the internal void space among the cross-linked MNWs can accommodate their large volume change during cycles. As a result, the 3D MNWs@GNSs microflowers as cathode exhibit excellent electrochemical behaviors in aqueous ZIBs, including large reversible specific capacity (~306.8 mAh g−1), remarkable rate capability and cycling stability (~97.5% retention after 10000 cycles). The strong durability is superior to those of reported MnO2 based cathodes in aqueous ZIBs. Furthermore, the electrochemical process with high reversibility is effectively demonstrated by in-situ Raman investigation. As a proof of concept, flexible aqueous ZIBs are fabricated and represent stable electrochemical performance under various deformation states, indicating their potential applications in portable and wearable electronics.