Ammonium fluoride-mediated waste silicon cuttings into silicon-graphite composite electrodes for lithium-ion batteries

The large-scale manufacturing of photovoltaic cells generates substantial silicon waste, especially in the form of fine cuttings from wafer slicing, which poses environmental concerns but also represents a valuable resource for upcycling into functional materials such as battery anodes. Herein, we report a sustainable pathway to convert these waste silicon cuttings into silicon–carbon composite anodes via ammonium fluoride (NH 4 F) mediated carbonization in the presence of graphite. The decomposition of NH 4 F generates reactive species that both etches and functionalizes Si surfaces to improve carbon coating conformity and interfacial bonding with graphite, producing composites that show improved first-cycle coulombic efficiency, rate capability. Comprehensive structural, morphological, and chemical analysis conducted using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N 2 adsorption/desorption isotherm revealed induced modification by NH 4 F during carbonization. The optimized composite with 10% silicon loading (10-Si-Gr) shows a high initial coulombic efficiency (ICE) of 79%, a discharge capacity of 525 mAh g –1 , and a reversible charge capacity of 415 mAh g –1 , surpassing the theoretical capacity of graphite (372 mAh g –1 ). Furthermore, it supports 85 % capacity retention after 200 cycles. This work highlights a facile, sustainable strategy for upcycling of waste silicon cuttings into practical anode materials, contributing to both environmental waste reduction and advancement of next-generation energy storage technologies .