A research team in India has developed a novel recycling process to recover silicon and native silica (SiO₂) from end-of-life (EoL) crystalline silicon solar cells for use as electrode materials in energy-storage applications. Different substrates were evaluated with the recovered silicon to assess their impact on charge-storage mechanisms.
“The significant increase in cumulative photovoltaic installed capacity has led to a sharp rise in EoL modules, creating an urgent need for sustainable waste management,” the researchers said. “This study presents an eco-friendly approach by integrating recycled PV waste into electrode materials for lithium-ion (Li-ion) electrochemical systems, with an emphasis on substrate-dependent faradaic charge-storage behavior.”
The process begins with manual dismantling and removal of aluminum frames from waste modules, followed by thermal treatment at 480 C to decompose and remove the EVA encapsulant, backsheet, and residual glass. The recovered silicon cell fragments were then isolated and ball-milled at 450 rpm for 6 h to obtain a micron-sized powder, followed by sequential alkaline and acid leaching using sodium hydroxide (NaOH) and hydrochloric acid (HCl) for purification.
Process optimization was carried out by varying the NaOH:HCl molar ratio, with a 1:1.25 ratio delivering the highest silicon recovery of around 97.75%. The purified powder was then mixed with carbon nanotubes (CNTs) as a conductive additive, polyvinylidene fluoride (PVDF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a solvent in an 80:10:10 weight ratio to form a slurry. The slurry was coated onto copper foil, indium tin oxide (ITO)-coated glass, and graphite sheets as current collectors, followed by vacuum drying at 90–100 °C.
| Image: CSIR- National Physical Laboratory, RSC Sustainability,
CC BY 4.0
The recovered material was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Raman spectroscopy. Morphological analysis was performed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and atomic force microscopy (AFM).
Thermogravimetric analysis (TGA) was used for thermal characterization, while Brunauer–Emmett–Teller (BET) analysis was used to determine surface area. Electrochemical performance was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge (GCD).
“The electrodes fabricated on copper foil and ITO exhibited diffusion-controlled, battery-type behavior, whereas those on graphite substrates showed capacitive charge-storage characteristics,” the researchers reported. “Cyclic voltammetry and electrochemical impedance spectroscopy confirmed good interfacial properties, while galvanostatic charge–discharge tests demonstrated stable performance over 500 cycles.”
The specific capacitance values for electrodes on Cu foil, ITO, and graphite were calculated at 143.23 F g, 30.53 F g, and 163.92 F g, respectively. “Therefore, electrodes fabricated on copper foil and ITO are suitable for silicon-based electrodes in Li-ion electrochemical systems, while graphite-based electrodes show promise for sustainability-driven energy-storage applications,” the team concluded.
The method was presented in “Recycling of solar cells recovered from waste panels into efficient silicon-based composite electrodes for energy-storage applications,” published in RSC Sustainability. Researchers from the National Physical Laboratory of India (CSIR) and India’s Academy of Scientific and Innovative Research (AcSIR) have participated in the research.
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