High-Quality Single-Walled Carbon Nanotubes for Lithium-Ion Battery Cathodes

Single-walled carbon nanotubes (SWNTs) hold great promise as conductive agents in high-performance lithium-ion batteries owing to their exceptional electrical and mechanical properties. However, their synthesis is highly sensitive to temperature, which often leads to structural defects and poor dispersion. These issues considerably impede the formation of conductive networks and compromise the stability of battery performance. Therefore, precise temperature control is critical for improving the quality of SWNTs and facilitating their practical application. In this study, a mixed catalyst of ferrocene and sublimed sulfur was employed to systematically investigate the effect of reaction temperature on SWNTs synthesis. A uniform SWNTs slurry with low iron content was prepared, and the electrochemical performance of the as-synthesized SWNTs was evaluated using LiFePO4 as the cathode material. Raman spectroscopy and BET measurements revealed an exceptionally narrow optimal temperature window for high-quality SWNT growth. At 1000 °C, highly graphitized SWNTs with low defect density and high specific surface area were obtained. In contrast, lower temperatures resulted solely in multiwalled carbon nanotubes (MWNTs), while excessively high temperatures led to progressive degradation in SWNT properties. The SWNTs synthesized at 1000 °C significantly reduced the charge transfer resistance of LiFePO4 electrodes even at an ultralow loading of 0.2 wt %, endowing the electrodes with superior performance. This efficient and controllable synthesis strategy provides a robust foundation for the stable and large-scale production of SWNTs.