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Shixia Chen1 2 Shuguang Deng1

1, School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona, United States
2, School of Resource, Environmental and Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China

Wearable energy sources are in urgent demand due to the rapid development of wearable electronics. Supercapacitors possess a high power density and long cycle lifetime, thus developing flexible high-performance supercapacitors is a promising route to meet the demand for wearable energy sources. The realization of high-performance flexible supercapacitors strongly relies on the electrical properties and mechanical integrity of the constitutive materials and their ingenious assembly into free-standing and binderless skeleton. Pseudocapacitive metal (e.g., nickel, cobalt, and manganese) hydroxides/oxides provide multiple oxidation states for reversible Faradaic reactions which have been extensively pursued to realize efficient supercapacitors devices. However, the faradaic nature of bulk pseudoactive material with limited diffusion length restrains the capacitance contribution within the surface and/or near the surface of the material. Thus, a method to control the structure of the material should be found to improve the charge and ion-transfer efficiency of the flexible pseudoactive material. Core–shell structure with different pseudocapacitive materials can provide more electroactive sites, higher electrical conductivity, faster ion-electron transport, which might lead to unprecedented electrochemical performance. Herein, we design and fabricate a new and hierarchically core-shell structured hybrid of electroactive material coating (NiMn-glucose-LDH) on in situ grown NiCo2S4 nanotube arrays on a flexible carbon fiber cloth (CFC), denoted as NiMn-G-LDH@NiCo2S4. Highly conductive NiCo2S4 nanotube arrays grown on a flexible CFC, which can serve not only as a superior pseudocapacitive material but also as a three-dimensional (3D) conductive scaffold for loading additional electroactive materials. Glucose intercalated NiMn LDH (NiMn-G-LDH) could significantly improve the ion diffusion coefficient with the expansion of the interlayer distance. Inheriting the merits of NiMn-G-LDH and NiCo2S4 nanotube, the free-standing NiMn-G-LDH@NiCo2S4 hybrid could synchronously achieve the excellent rate performance and cycle stability. The electrochemical investigation shows that the NiMn-G-LDH@NiCo2S4 have a significantly enhanced specific capacitance (1,793 Fg-1 at 1Ag-1) , rate capability (~70% retention at 20 A g-1) and cycling performance (keep ~82% after 1000 cycles) that far exceed those of the reported individual NiCo2S4 and NiMn LDH electrodes.

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