Enhancing sodium-ion storage in lignin-based ultrafine carbon fibers via single-walled carbon nanotube reinforcement and mild phosphoric acid activation
摘要
Hardwood Kraft lignin-based ultrafine carbon fibers (HKL-CFs) face significant challenges as anode materials for sodium-ion batteries (SIBs), including low specific capacity and inferior initial Coulombic efficiency (ICE), which limit their practical application. To address these issues, we introduce a synergistic approach combining single-walled carbon nanotubes (SWCNTs) reinforcement with mild phosphoric acid activation to improve the sodium storage performance of HKL-CFs. This study systematically examines the influence of SWCNTs on the chemical structure and thermal properties of HKL fibers, as well as the combined effects of SWCNTs incorporation and phosphoric acid treatment on the morphology, microstructure, and electrochemical behavior of the resulting carbon fibers. Our findings indicate that while SWCNT addition does not alter the chemical structure of HKL fibers, it significantly affects the fiber morphology, microcrystalline structure, and ultimately the sodium storage performance. The HKL-CFs modified with 0.5 wt% SWCNTs delivered the best electrochemical properties, exhibiting an initial discharge capacity of 533.7 mA h g−1, an ICE of 36.4%, and remarkable rate capability—recovering 95.6% of its initial capacity after cycling at current densities ranging from 50 to 5000 mA g−1. Moreover, a reversible capacity of 176 mA h g−1 was retained after 100 cycles. Although the performance enhancement remains moderate, the strategy presented herein offers a viable route for further optimizing the electrochemical properties of sustainable lignin-based carbon fibers for energy storage applications.
Graphical abstract