A laser-enabled low carbon emission pyrometallurgical approach to recycle Li-ion batteries via silicothermic reductions

Abstract

In response to the growing shift from graphite to silicon in Li-ion battery anodes, we propose a novel low-carbon pyrometallurgical recycling method that uses silicon as the reducing agent. Silicon was chosen as the reductant because, as the emerging high-capacity anode material, it not only integrates seamlessly with next-generation battery chemistries but also offers a substantially lower carbon footprint than conventional carbon-based reducing agents. The thermodynamics and reaction mechanism between LiCoO₂ and Si are investigated using differential thermal and thermogravimetric analyses. The reaction products are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. When heated to 1500 °C, LiCoO₂ undergoes simultaneous decomposition and melting, reacting with Si to produce cobalt spheres. Through a laser-enabled recycling process for only 30 s with a laser power of 2 kW, LiCoO₂ is reduced via silicothermic reaction to a Co–Si alloy with only a small amount of slag (Li₂SiO₃ and Li₂Co(SiO₄)). This successful use of silicon paves the way for a cleaner, more sustainable battery recycling strategy.