Optimizing Synthesis Temperature for Lignin-Derived Hard Carbon Anode for High Cycling Capacity in Sodium-Ion Batteries

This comprehensive study sheds light on the promising potential of lignin-derived carbonaceous materials as sustainable and cost-effective anode materials for sodium-ion batteries, contributing to the development of eco-friendly energy storage technologies. Lignin, a complex and abundant biopolymer, undergoes a facile pyrolysis process to produce carbonaceous materials. The unique microstructure of lignin-derived carbon, characterized by a relatively high surface area and interconnected porous network, facilitates efficient sodium ion diffusion and accommodates volume changes during cycling. The effects of pre-treatment methods, carbonization conditions, and structural modifications of lignin on the electrochemical performance are systematically investigated. Furthermore, the electrochemical mechanisms underlying the sodiation/desodiation processes in lignin-derived carbon (LDC) based anodes are elucidated through advanced characterization techniques, including in situ spectroscopy and microscopy. Among the different hard carbon materials, pre-pyrolyzed lignin-derived carbon LDC-300–1400 (300 shows which pre-treatment pyrolysis temperature was used and 1400 is the post-pyrolysis temperature in °C) shows the most favourable outcomes, demonstrating a reversible capacity of 359 mAh g −1 , 1st cycle coulombic efficiency of 81%, and good rate capabilities. Hydrothermally pre-treated LDCs show a slightly lower specific capacity value reaching up to 337 mAh g −1 .