Scaling up Si–C composite synthesis from recycled graphite for high-energy density and low-environmental impact batteries

Abstract

Graphite-silicon (GtSi) composites are recognized as promising materials as a replacement of graphite in lithium battery anodes because of their high specific capacity of around 1000 mAh g⁻¹ and their mitigated volume change in cycling. Taking advantage of the recent progress in used battery treatment, we investigate the production of GtSi from recycled graphite as a strategy for material upcycling. The present paper reports the scaling-up of GtSi synthesis to a 25 gram scale. To manage the risk associated with this growth process involving pyrophoric reagents and hydrogen gas evolution at 400 °C under 10 bar, the kinetic and thermodynamic parameters of diphenylsilane thermal decomposition were accurately measured. The scaled-up synthesis of GtSi then allowed the use of relevant roll-to-roll battery electrode fabrication and assembly of 40 mAh GtSi|NMC811 pouch cells and demonstrated a high energy density of 984 Wh L⁻¹. Finally, life cycle assessment has been used to identify environmental hotspots for GtSi and GtSi|NMC cell fabrication. Lab-scale primary data were used to draw transparent and clear life cycle inventories, thus contributing to filling data gaps, typically a bottleneck in LCAs of novel battery materials and technologies.