Upcycling silicon from expired solar panels into lithium-ion batteries

Scientists from NTU Singapore have devised an efficient method of recovering high-purity silicon from expired solar panels to produce lithium-ion batteries that could help meet the increasing global demand to power electric vehicles. 

High-purity silicon makes up the majority of solar cells, yet they are typically discarded at the end of their operational lifespan after 25 to 30 years. It is challenging to separate the silicon from other solar cell components such as aluminium, copper, silver, lead, and plastic. Moreover, recycled silicon has impurities and defects, making it unsuitable for other silicon-based technologies.

Existing methods to recover high-purity silicon are energy-intensive and involve highly toxic chemicals, making them expensive and limiting their widespread adoption among recyclers. 

The NTU researchers overcame the challenges through a new extraction method using phosphoric acid, a substance commonly used in the food and beverage industry.

The NTU approach demonstrated a higher recovery rate and purity than present silicon recovery technologies. The process is also more efficient, involving just a single reagent (phosphoric acid), whereas conventional methods include at least two types of chemicals (highly acidic and highly alkaline)