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

The increasing demands for conversion systems for clean energy, wearable devices powered by energy storage systems, and electric vehicles have greatly promoted the development of innovative current collectors to replace conventional metal-based foils, including those in multidimensional forms. In this study, carbon nanotubes (CNTs) with desirable features and ease of processing are used in the preparation of floating catalyst-chemical vapor deposition-derived CNT sheets for potential use as all-around current collectors in two representative energy storage devices: batteries and electrochemical capacitors. Due to their short and multidirectional electron pathways and multimodal porous structures, CNT-based current collectors enhance ion transport kinetics and provide many ion adsorption and desorption sites, which are crucial for improving the performance of batteries and electrochemical capacitors, respectively. By assembling activated carbon-CNT cathodes and prelithiated graphite-CNT anodes, high-performance lithium-ion hybrid capacitors (LIHCs) are successfully demonstrated. Briefly, CNT-based LIHCs exhibit 170% larger volumetric capacities, 24% faster rate capabilities, and 21% enhanced cycling stabilities relative to LIHCs based on conventional metallic current collectors. Therefore, CNT-based current collectors are the most promising candidates for replacing currently used metallic materials and provide a valuable opportunity to possibly redefine the roles of current collectors.