Continuous Preparation of a Flexible Carbon Nanotube Film from Lignin as a Sulfur Host Material for Lithium–Sulfur Batteries

Lignin is an abundant natural polymer and a green biomass precursor containing over 60% carbon. However, high-value and sustainable material production from lignin remains underutilized. Here, a flexible carbon nanotube (CNT) film is continuously fabricated via floating catalyst chemical vapor deposition (FCCVD) using lignin as the carbon source. The as-prepared CNT film exhibits high conductivity (4.19 × 104 S m–1) and can directly serve as an electrode material without further processing. Moreover, the adaptable CNT film displays strong mechanical properties (54.53 MPa) and fatigue resistance, making it an excellent flexible host for lithium–sulfur (Li–S) batteries. The intertwined CNTs provide efficient electron transport, accelerating the reaction kinetics. Consequently, the Li–S cells with CNT film-based cathodes maintained capacities of 706.1 and 435.3 mA h g–1 after 200 cycles at 0.5 and 1.0 C, respectively. Foldable Li–S pouch cells with CNT film-based cathodes also powered LED lights. This green, low-cost, straightforward fabrication of lignin-based CNT films as sulfur hosts provides an attractive alternative for valorizing abundant lignin into high-value materials at scale.