Direct-spun carbon nanotube sheet: A flexible, ultralight, stackable three-dimensional current collector for high-performance lithium-ion batteries

Among the key components of a battery electrode, current collectors hold significant importance for the energy density of lithium ion batteries (LIBs) as metal foils account for a significant proportion of the total mass. Carbon nanotube sheet (CNTS) has garnered considerable attention because of its fascinating material features such as high electrical conductivity, low density, and excellent flexibility. In this study, we demonstrate the utilization of a direct-spun CNTS as a current collector in order to enhance the electrochemical performance and replace the conventional current collector, that is, aluminum (Al) foil, in LIBs. When the CNTS coated with NCM811 (NCM811/CNTS) is evaluated in LIBs, it delivers superior rate capability and cycle stability compared with Al foil-based and buckypaper-based NCM811 electrodes. It is because the CNTS with a large surface area and high electrical conductivity establishes a number of electronic pathways to the cathode electrode. In addition, the porous structure of the CNTS efficiently enhances the adhesive properties of the electrodes. Due to the synergistic benefits of CNTS, cells with stacked NCM811/CNTS electrodes are successfully fabricated. Electrode stacking with multiple NCM811/CNTS electrodes exhibits improved areal capacity and stable cycle stability, suggesting a new strategy to replace the concept of conventional thick electrodes. Moreover, pouch cells with LTO/CNTS as an anode and NCM811/CNTS as a cathode display stable electrochemical performance even under mechanical deformation (e.g., folding/unfolding)