Processing-Structure-Property Relationships for Lignin-Based Carbonaceous Materials Used in Energy-Storage Applications

Lignin, an abundant organic polymer and a byproduct of pulp and biofuel production, has potential applications owing to its high carbon content and aromatic structure. Processing-structure relationships are difficult to predict because of the heterogeneity of lignin. This work discusses the roles of unit operations in the carbonization process of softwood lignin, and their resulting impacts on the material structure and electrochemical properties in application as the anode in lithium-ion cells. The processing variables include the lignin source, temperature, and duration of thermal stabilization, pyrolysis, and reduction. Materials are characterized at the atomic and microscales. High-temperature carbonization, at 2000 degrees C, produces larger graphitic domains than at 1050 degrees C, but results in a reduced capacity. Coulombic efficiencies over 98% are achieved for extended galvanostatic cycling. Consequently, a properly designed carbonization process for lignin is well suited for the generation of low-cost, high-efficiency electrodes.