Intertwined CNT Assemblies as an All-Around Current Collector for Volume-Efficient Lithium-Ion Hybrid Capacitors

Abstract

The increasing demands for conversionsystems for cleanenergy,wearable devices powered by energy storage systems, and electric vehicleshave greatly promoted the development of innovative current collectorsto replace conventional metal-based foils, including those in multidimensionalforms. In this study, carbon nanotubes (CNTs) with desirable featuresand ease of processing are used in the preparation of floating catalyst-chemicalvapor deposition-derived CNT sheets for potential use as all-aroundcurrent collectors in two representative energy storage devices: batteriesand electrochemical capacitors. Due to their short and multidirectionalelectron pathways and multimodal porous structures, CNT-based currentcollectors enhance ion transport kinetics and provide many ion adsorptionand desorption sites, which are crucial for improving the performanceof batteries and electrochemical capacitors, respectively. By assemblingactivated carbon-CNT cathodes and prelithiated graphite-CNTanodes, high-performance lithium-ion hybrid capacitors (LIHCs) aresuccessfully demonstrated. Briefly, CNT-based LIHCs exhibit 170% largervolumetric capacities, 24% faster rate capabilities, and 21% enhancedcycling stabilities relative to LIHCs based on conventional metalliccurrent collectors. Therefore, CNT-based current collectors are themost promising candidates for replacing currently used metallic materialsand provide a valuable opportunity to possibly redefine the rolesof current collectors.