Recovery of Nano-Structured Silicon from End-of-Life Photovoltaic Wafers with Value-Added Applications in Lithium-Ion Battery

Abstract

Millions of residential and industrial solar panels installed in the late 1980s and early 1990s are approaching the end of their life, resulting in the drastic accumulation of a potential source of environmental pollutiongiven the presence of hazardous materials, such as lead. The foreseen crisis, however, can be turned into a great opportunity by value-added recovery of precious solar-grade silicon (Si) to the highly desired nanostructured silicon for lithium-ion batteries (LIBs). Herein, we demonstrate a potential end-of-life management option for photovoltaic (PV) panels, representing a step toward producing greener and more energy-efficient Si for batteries. We show that leaching the recovered silicon wafers in critically tuned alkali-acid leaching baths effectively removes the major impurities: lead (Pb), silver (Ag), and aluminum (Al). The ultrapure Si is then nanosized via industrially scalable milling routes to meet the requirements of expansion-tolerant Si anodes for LIBs delivering capacities as high as 1400 mAh g −1 .

Effect of Size and Shape on Electrochemical Performance of Nano-Silicon-Based Lithium Battery

“…This deleterious volume change stimulated the development of Si nanomaterials, because Si at the nano scale can withstand swelling without fracture during LiB cycling. This has been demonstrated for a variety of morphologies including Si nanoparticles (SiNP) [ 6 , 7 , 8 , 9 , 10 , 11 ], Si nanowires (SiNW) [ 3 , 12 , 13 , 14 ], Si nanotubes [ 15 , 16 ], and Si porous nanomaterials [ 17 , 18 , 19 ]. However, nanostructuration can be a costly process that needs to be carefully optimized for a dedicated application.…”

“…A critical diameter was also predicted by a mechanical numerical model [ 23 ] at 90 nm for SiNPs and 70 nm for SiNWs. By contrast, several electrochemical studies in LiB investigated the impact of particle size on Si-based anode cycling for small [ 6 , 8 ] and large [ 7 , 8 , 9 ] SiNPs, with the best results at diameters of 20–50 nm. As for SiNWs, some studies have suggested the optimal diameter as being around 30 nm [ 10 , 24 ].…”

“…However, these highly controlled growth processes produce insufficient (~1 mg) quantities of material for assembling a lithium-ion battery (requiring >100 mg for typical coin cell electrodes). Typical scalable processes developed for industrial synthesis of SiNPs [ 28 , 29 ] and SiNWs [ 9 , 30 , 31 ] produce nanomaterial either with a very wide size distribution or with a limited ability to change the diameter. The synthesis of a series of nano-silicon materials of fine-tuned size in a large scale is, thus, a challenge for materials chemists.…”

An Investigation of the Recovery of Silicon Photovoltaic Cells by Application of an Organic Solvent Method

“…The result obtained from our tests was a back-sheet specific surface density of 0.72 g/cm 3 .The mass of the back-sheet (assumed to remain constant throughout the EVA dissolution process) was subtracted from the mass obtained before and after the EVA dissolution to obtain the initial (mi) and final (mf) mass of the other PV sheet section constituents. The percentage detachment (δ) is given by Equation 1 as: δ = ((mimf) *100) / mi [1] Using the expression, percentage detachment was estimated and plotted. It can be seen from Figure 8 that toluene has a superior dissolution capability compared to hexane at ambient conditions.…”

“…The idea is to provide much needed material for the manufacture of new PV modules while addressing the matter of waste management and minimization. Recycling of end-of-life modules could also alleviate the energy burden associated with the fabrication of crystalline-silicon solar cells via the Siemens process (1) (8). The process is reported to be one of the most energy intensive stages in the production of silicon PV modules (9).…”