Lithium Ion Battery Graphite Anodes
Lithium ion batteries are becoming increasingly popular in vehicles as they offer an alternative to burning fossil fuels. However, these batteries also require a large amount of graphite for their anodes to cope with the flow of lithium ions during charging and discharging. It is thought that a typical EV uses up to 10 kg of graphite and in some cases even more. This could lead to a 10% increase in demand for flake graphite, if EV adoption rates continue at current levels.
Graphite is the most commonly used material in battery anodes due to its relatively low cost and high energy density. However, the performance of graphite anodes depends on a number of factors including cycling performance and the formation of a protective SEI layer.
In the present study, binder-free natural graphite anodes were cycled in lithium ion batteries with different EC electrolytes (EC/EMC). In order to analyze the morphology and performance of the anode material, transmission electron microscopy with energy dispersive X-ray spectroscopy was performed. This was complemented by multi-nuclear magnetic resonance spectroscopy of D2O extracts from the cycled anodes.
The results show that the morphology of the graphite particles can influence the polarization of the SEI film. When the graphite particles are coated by small spherical carbon particles, the polarization of the SEI is reduced and the deposition of metallic Li is mitigated. Furthermore, the morphology of the anode material influences the extent of the deposited Li on the SEI layer and the corresponding anode capacity.
