S.C. Dey, S.-M. Cho, S. Appikatla, Z.A. Combs, W.J. Sagues, S. Park
North Carolina State University,
United States
Keywords: Bio-oil, crosslinking, bioresin, hard carbon, anode, sodium-ion batteries
Summary:
Sodium-ion batteries (SIBs) are becoming increasingly popular as an alternative to lithium-ion batteries (LIBs) particularly for grid-scale energy storage applications. Currently, the preferred SIB anode is hard carbon having a disordered microstructure unlike crystalline graphite (preferred anode for LIBs). This study aimed to produce hard carbon anode material via carbonization of humin-type bioresins at 1400 °C in inert nitrogen atmosphere. The bioresins were prepared through crosslinking of pyrolysis bio-oil feedstock using glyoxylic acid and glyoxal crosslinkers at varying ratios (1:0.1, 1:0.5, and 1:1) in acidic environment. Within the scope of this study, hard carbon prepared at 1:0.5 ratio of bio-oil to glyoxal crosslinker demonstrated most promising electrochemical performance (fourth cycle reversible capacity: 131.21 mAh/g and first cycle Coulombic efficiency: 66.34%) in SIB half-cells compared to other samples. The enhanced interlayer spacing (d002 = 0.3702 nm) and presence of relatively higher fraction of single layer graphitic carbon contributed to the optimal electrochemical performance of this sample. The findings of this study suggest new opportunities for valorizing pyrolysis bio-oil which is considered a complex feedstock with limited industrial applications at present.