Synergy of TiO2 and polydopamine dual coating of recycled photovoltaic silicon waste enables superior-performance silicon anodes for lithium-ion batteries

Recycling of photovoltaic silicon (Si) waste (WSi), which accounts for around 30 % of Si losses in the production of solar wafers, has been prioritized to meet the needs of sustainable energy and the circular economy. If WSi can be employed as the anodes of lithium-ion batteries (LIBs), the recycling of WSi should be effectively achieved. Herein, to form high-performance WSi-derived anodes, a Si/TiO₂/polydopamine (PDA) composite was prepared by sol-gel method and subsequent in-situ polymerization. The as-prepared Si/TiO₂/PDA composite consists of a Si core, an amorphous TiO₂ intermediate layer buffering the volume change of Si along with a PDA outer layer alleviating the expansion/contraction of Si together with promoting charge transfer. The Si-O-Ti bonds were formed between the Si core and the TiO₂ intermediate layer. Synergy of TiO₂ and PDA enables superior performance Si/TiO₂/PDA possessing a reversible discharge capacity of 1757.1 mAh g⁻¹ after 70 cycles at 0.2 A g⁻¹ (65.1 % retention), indicating good cyclability, and super rate performance (1243.9 mAh g⁻¹ at 2 A g⁻¹). Lithium-ion full cell with Si/TiO₂/PDA anode and LiNi_0.5Co_0.2Mn_0.3O₂ cathode retains 113.2 mAh g⁻¹ (81.1 % retention) after 100 cycles at 0.5 C.