Carbons from biomass precursors as anode materials for lithium ion batteries: New insights into carbonization and graphitization behavior and into their correlation to electrochemical performance

We report a comprehensive and systematic study on the preparation and characterization of carbonaceous materials that are obtained from five different sustainable precursor materials and petroleum coke as reference material, particularly focusing on the correlation between the structural transformation of the precursors into carbons in dependence of heat treatment temperature (HTT) and their corresponding electrochemical characteristics as anode material in lithium ion batteries. The carbons were carbonized and graphitized in 200 °C steps, covering a broad temperature range from 800 °C to 2800 °C. So far, such a systematic synthesis approach has not been reported in literature. For biomass-derived carbons, we found a heterogeneous (discontinuous) graphitization process, i.e. a transformation from the amorphous to the graphitic phase via the turbostratic phase. A general trend was observed for the discharge capacity, i.e. a decrease of capacity from 800 °C to ≈1800–2000 °C, followed by an increase of capacity for temperatures >2000 °C. An increase of the 1st cyle Coulombic efficiency was found and could be directly correlated to the decrease of the “non-basal plane” surface area upon HTT. In addition, we found that the voltage efficiency and energy efficiency of the different carbons also increase with rising treatment temperatures.