PV Silicon Recovery for Lithium Ion Battery Anodes
Authors: Coyle Jaclyn , Green Jeff , Veith Gabriel M. , Keyser Matthew 
Published: December 2024

As solar photovoltaic (PV) devices across the globe reach the end of their approximately 30-year lifetimes, an emerging challenge is how to handle the waste from large volumes of end-of-life (EOL) PV modules. It is projected that the cumulative mass of EOL PV modules could be up to 8 million tonnes (Mt) by 2030 so recovery of high value materials from these EOL modules through a cost efficient recycling process would minimize environmental impacts compared to disposing them in landfills[1]. A typical recycling process for EOL PV modules involves mechanical disassembly, separation of the tempered cover glass and silicon wafer followed by purification and recovery of other constituents such as Pb or Ag with the goal of reinstating the recovered materials as a PV module. However, since new module prices continue to decline and the recovered PV modules typically have a shorter lifetime and lower efficiency, the economic value of using the recovered PV materials to manufacture a new PV module is uncertain[2]. Since silicon, particularly boron-doped, is a promising candidate for next-generation anodes for lithium-ion batteries (LIB), recovering the silicon from PV modules for use in LIB anodes could be an attractive alternative. A ball milling process was developed at Oak Ridge National Laboratory to prepare ball milled silicon from washed silicon boules as well as EOL PV modules sourced from a commercial PV module recycler. In this talk we will be discussing the purification process, contaminant removal requirements and key anode performance metrics of recycled PV silicon materials. Organic acid washing with and without microwave-treatment as the heat source was conducted on ball milled boron-doped silicon and reference undoped silicon. The organic acid washing was conducted several times and followed by centrifugation and drying to attempt to remove unwanted contaminant species and compared to a single step microwave-assisted process. The initial carbon species present after ball milling the silicon remained on the ball milled silicon based on FTIR data and the structure of the ball milled silicon was unchanged based on XRD analysis. Elemental analysis and half cells tests were conducted to observe the effect of boron-doping and contaminants inherent to the EoL PV Si material with pristine boron-doped silicon showing noticeably better performance than non-doped ball milled silicon or contaminated silicon PV silicon. Determining the maximum amount of each potential contaminant from PV panels will help facilitate these materials being introduced into local supply chains as a silicon precursor material for more highly engineered silicon anode materials.

IRENA, I.-P., End-of-Life Management: Solar Photovoltaic Panels 2016: International Renewable Energy Agency and International Energy Agency Photovoltaic Power Systems.

A. Wade, P.S., K. Drozdiak, E. Brutsch. Beyond Waste – The Fate of End-of-Life Photovoltaic Panels from Large Scale PV Installations in the EU. The Socio-Economic Benefits of High Value Recycling Compared to Re-Use. in 33rd European Photovoltaic Solar Energy Conference and Exhibition. 2017.