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

Abstract

Graphite-silicon composites (GtSi) are recognized 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 the GtSi synthesis to 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 1000 Wh.L^-1. Finally, life-cycle analysis reveals that incorporating recycled graphite-derived silicon into GtSi|NMC cells minimally impacts the environment, with its contribution remaining lower than that of the cathode or current collector, highlighting a sustainable path to high-performance lithium batteries.