LCI Comparison of Silicon and Graphite Anodes Manufactured Using Different Techniques

Most commercial lithium ion cells contain 5 – 10 wt% silicon in their predominantly graphite anodes, but the challenge of operating anodes with high silicon contents remains. One promising approach is to use plasma enhanced chemical vapour deposition (PECVD), rather than the standard composite coating approach with binders and solvents. There is a perception that CVD processes consume too much energy to be cost competitive, but this may neglect the large energy consumption associated with graphitisation. The most objective way to resolve this is to use a life cycle analysis comparison for different anode types.<br/><br/>A life cycle inventory (LCI) has been developed for four anode compositions; graphite, graphite with 10 wt% SiOx, 70 % silicon powder, and PECVD silicon. The first three anodes use binders and conductive carbon, in an aqueous mix. The fourth incorporates new primary data from a PECVD process using hexamethyl disiloxane as reactant, rather than the more common (and pyrophoric) silane. The LCI analysis calculates both the actual energy consumption, and kg CO₂-e values reflecting emissions of greenhouse gases, NOx, and SOx. Initial results suggest that the PECVD process should not be excluded, based on energy consumption and overall emissions.