The crucial role of impurity of photovoltaic silicon waste in dictating the performance of lithium-ion battery anodes

Photovoltaic silicon waste (WSi) can be used to manufacture Si-based anodes for lithium-ion batteries as a means of reducing production costs as well as achieving the high-value recycling of secondary resources. However, the mechanism by which trace metal impurities in WSi affect battery performance remains unclear. The present work quantitatively analyzed the key role of metal impurities physically doped into WSi in determining the performance of Si-based anodes. A paradoxical phenomenon in which metal impurities in WSi powders decreased the conductivity of the material was identified. Doping with magnetic metal impurities was also found to increase the magnetic strength of WSi powders while significantly enhancing the self-discharge effect of Si-based anodes. The mechanism responsible for this effect was revealed based on in situ monitoring and quantitative characterization. Trace metal impurities in WSi-based anodes were shown to spontaneously undergo electrochemical corrosion reactions, resulting in the formation of metal dendrites in the battery and the decomposition of the electrolyte. As a result, the battery performance became unstable and prone to safety hazard. The results of this research provide theoretical support for the value-added recycling of WSi based on manufacturing highly stable, safe Si-based anodes for lithium-ion batteries.