Speaker
Description
Since the hard carbons (HCs) has emerged as promising negative electrode materials for sodium-ion batteries, numerous research has been done on the factors impacting their electrochemical performance. Nevertheless, one of the most debatable question remains the sodium-ion insertion mechanism. Recently, we report electron paramagnetic resonance (EPR) spectroscopy as a comprehensive method to monitor the interaction of sodium into carbons derived from spent coffee grounds and used as electrodes in sodium-ion cells [1].
Herein, we applied the ex-situ EPR spectroscopy to monitor the sodium-ion insertion into hard carbons derived from lignin precursors. As precursors industrial biowaste was selected, i.e. kraft lignin and technical hydrolysis lignin. The HCs were prepared by pyrolysis at high temperatures (800 and 1300 oC) and under a constant Ar-flow. Depending on the biomass origin and synthesis temperature, the HCs show clearly distinguishable texture. The electrochemical insertion of sodium into hard carbons were carried out in model Na-cells consisting of sodium metal as counter electrode and in presents of carbonate-based sodium electrolyte (1M NaPF6:PC). At selected potential stages during the first electrochemical sodiation, the cells were stopped and ex-situ EPR spectroscopy was employed. The EPR analysis reveals the correlations between textural features - sodium intercalation - sodium cluster formation - storage performance. This insight into sodium storage mechanism can serve as a guiding point in the design of more efficient carbon electrode materials.