Molten salt electrochemical synthesis NiSi2-SiNRs anodes from photovoltaic waste silicon

The booming photovoltaic industry produces substantial amounts of severely oxidized waste silicon (wSi), posing increasing challenges for recycling due to its small particle sizes and uncontrolled oxidation. This study proposes a molten salt electrochemical approach to convert photovoltaic waste silicon into NiSi2-doped silicon nanorods (NiSi2-SiNRs) as high-performance anode materials for lithium-ion batteries. By regulating the oxidation process, a stable oxidized passivation layer is constructed on the surface of waste silicon powder. Simultaneously, in situ introduced nickel oxide catalyzes the formation of highly active NiSi2 droplets. The molten salt electric field modulates the surface energy of silicon, while particle integration induces localized directional growth, enabling self-assembly into NiSi2-SiNRs composites. The resulting NiSi2-SiNRs anode demonstrates rapid ion permeation and effective strain buffering. The high aspect ratio of silicon nanorods, combined with retained NiSi2, enhances both longitudinal and transverse Li+ diffusion rates. Benefiting from robust coupling design, the NiSi2-SiNRs anode achieves an exceptional initial Coulombic efficiency (ICE) of 91.61% and maintains 72.99% capacity retention after 800 cycles at 2 A g-1. This work not only establishes a model system for investigating silicide/silicon interfaces in molten salt electrochemistry but also provides an effective strategy for valorizing photovoltaic waste silicon and advancing high-performance lithium-ion battery anodes.