Snowflake-like core-shell α-MnO2@δ-MnO2 for high performance asymmetric supercapacitor

• DOI: 10.1016/j.electacta.2017.08.146
• Publication Date: 2017-08-30T23:32:50Z
• Authors: Yu Li; Zongying Xu; Dawei Wang; Jing Zhao; Huaihao Zhang
• Keywords: Horizontal scan rate; Power density; Chemical bath deposition

Abstract Novel three-dimensional (3D) snowflake-like α-MnO 2 @δ-MnO 2 (3D-MnO 2 ), with hierarchical core-shell nanostructures, was synthesized by a facile hydrothermal route and chemical bath deposition method. The 3D-MnO 2 can improve the defects of single-phase MnO 2 as electrode materials. The microstructure and chemical composition of as-prepared samples were characterized by a series of means, such as XRD, SEM, TEM, HRTEM, XPS and BET. The morphology of α-MnO 2 , δ-MnO 2 and 3D-MnO 2 were 3D star-like nanowires, tremella-like nanosheets and 3D snowflake-like hierarchical nanostructures, respectively. From its unique interconnected hierarchical structure, the 3D-MnO 2 possessed the highest specific capacitance ( C m ) (260.5 F g −1 at a current density of 0.3 A g −1 , about 2.7 times of α-MnO 2 and 1.5 times of δ-MnO 2 ), good rate performance and excellent cycling stability (94.7% capacitance retention after 3000 cycles). Furthermore, an asymmetric supercapacitor (3D-MnO 2 //AC) was successfully assembled, 3D-MnO 2 as positive electrode and activated carbon (AC) as negative electrode. Meanwhile, the optimized 3D-MnO 2 //AC device with a voltage window of 2.0 V delivered a maximum energy density of 36.6 Wh kg −1 at a power density of 0.3 kW kg −1 .