Preparation of dendritic nano-Si through low-temperature molten salt electrolysis of Al-Si alloys as advanced lithium-ion battery anodes

This study proposes a low-temperature molten salt electrolysis strategy to prepare dendritic nanostructured silicon (nSi) from Al-Si alloys for high-performance lithium-ion battery anodes. The method uses the 403 K AlCl 3 -NaCl-KCl molten salt as electrolyte, in which aluminum is selectively removed from Al-Si (AlSi 12 , AlSi 20 , AlSi 30 ) alloys through anodic dissolution while metallic aluminum is recovered at the cathode. The resulting nSi exhibits tunable porosity dependent on the Al content in Al-Si, and the AlSi 12 -derived nSi 12 shows the highest specific surface area (48.7 m 2  g −1 ) and pore volume (0.21 cm 3  g −1 ) with interconnected 30–50 nm dendritic structures. When evaluated as anodes, nSi 12 demonstrates superior electrochemical performance with initial Coulombic efficiency of 91.1% at 1 A g −1 , retaining 2441 mAh g −1 after 100 cycles (or 80.0% capacity retention). The enhanced performance stems from its porous architecture buffering volume expansion, as evidenced by the electrode expansion after 100 cycles of 26% for nSi 12 versus 60.4% for nSi 30 . Comparative analysis reveals lower charge transfer resistance and higher Li + diffusion coefficient in nSi 12 . This method achieves an Al recovery rate of 95%, offering an energy-efficient, closed-loop approach for nanostructured silicon production with dual advantages in sustainable manufacturing and high-performance energy storage.