UC Riverside

Silicon (Si) is a high-capacity anode material that can be used to replace or be added in the graphite anode in the next generation lithium-ion (Li-ion) batteries. Tremendous research and development efforts from both academic and industrial sectors are devoted to commercializing Si-based anode materials in the near future, however, successful cases of Si-anode commercialization are still lacking. The technical challenges are most originated from two fundamental properties of Si as a Li storage material: inevitable volume change during lithiation-delithiation and inferior electronic conductivity comparing to graphite. The former results to continuous degradation of the electronic connection in the electrodes and continuous rapture of the solid electrolyte interphase (SEI); the latter seriously limits the areal loading of the Si-based materials in the electrode thus difficult to achieve practical high-capacity. In addition to the challenges from the material properties, the industrial production process is equally or more important to the commercialization of Si-based anode materials. Such a production process not only must be scalable with economic feasibility feasible but also technologically robust to achieve optimal properties of the Si anode materials.

Among the numerous production methods reported to date, magnesiothermic reduction reaction (MRR) remains a viable candidate for Si material production process. Since Bao and co-workers reported Si synthesis via thermal reduction of silicon oxide by magnesium (Mg), many studies on Si-based anode materials from MRR has been reported. However, there remains some challenges: Due to the exothermic nature of MRR, it is difficult to control the microstructure of the obtained Si due to the fusing of Si. Generation of byproducts magnesium silicate (Mg2SiO4) or magnesium silicide (Mg2Si) is another severe challenge of MRR. These byproducts are induced due to discrepant atoms mobilities in Si-Mg-O system and the chemical stability of the interface between MgO, SiO2 and Si. Finally, the kinetics of MRR is not well understood therefore it has been difficult to optimize the MRR process.