Molten salt electrochemical synthesis of NiSi₂–SiNRs anodes from photovoltaic waste silicon

The rapid expansion of the photovoltaic industry has generated heavily oxidized waste silicon (wSi), which hinders efficient recycling owing to its small particle size and uncontrolled surface oxidation. This study introduces a molten salt electrochemical strategy for converting photovoltaic wSi into NiSi₂–silicon nanorods (NiSi₂–SiNRs) as high-performance anode materials for lithium-ion batteries. A stable oxidized passivation layer is formed on the wSi surface via controlled oxidation. Moreover, in situ generated nickel oxide catalyzes the formation of highly active NiSi₂ droplets. The molten salt electric field modulates the surface energy of silicon, while particle integration drives localized directional growth, enabling the self-assembly of NiSi₂–SiNRs composites. These NiSi₂–SiNRs anodes exhibit rapid ion transport and effective strain buffering. The high aspect ratio of SiNRs and the presence of retained NiSi₂ facilitate both longitudinal and transverse Li⁺ diffusion. Owing to their robust structural design, the NiSi₂–SiNRs anode achieves an excellent initial Coulombic efficiency of 91.61% and retains 72.99% of its capacity after 800 cycles at 2 A·g⁻¹. This study establishes a model system for investigating silicide/silicon interfaces in molten salt electrochemical synthesis and provides an effective strategy for upcycling photovoltaic wSi into high-performance lithium-ion battery anodes.