https://www.pv-magazine.com/2023/09/14/single-reagent-tech-to-reuse-silicon-from-end-of-life-pvpanels-achieves-recovery-rate-of-98-9/

Single-reagent tech to reuse silicon fromend-of-life PV panels achieves recovery rateof 98.9%
Scientists in Singapore developed a single-reagent approach to recover silicon in recycled PV
panels that reportedly offers high recovery rates compared to double-reagent methods. The
recycled silicon was then effectively reused in anodes intended for applications in lithium-ionbatteries.
SEPTEMBER 14, 2023 EMILIANO BELLINIImage: Nanyang Technological University (NTU)
A group of scientists led by Nanyang Technological University (NTU) in Singapore hasdeveloped a process to recycle silicon from end-of-life PV panels that reportedly offers arecovery rate of up to 98.9%.
“The NTU approach demonstrated a higher recovery rate and purity than present silicon
recovery technologies,” the research's lead author, Sim Ying, told pv magazine. “We usedthe recovered silicon in a lithium-ion battery anode and tested it for efficiency. Results
showed that it performed similarly to new, commercially bought silicon.”
In the paper “Simplified silicon recovery from photovoltaic waste enables high performance,sustainable lithium-ion batteries,” published in Solar Energy Materials and Solar Cells, theresearch team explained that the common approaches for recycling silicon from PV panels
use two reagents – nitric acid (HNO3) and potassium hydroxide (KOH) – to separate themetals from silicon cells.
Despite their effectiveness and accessibility, these two reagents generate both acidic andalkaline post-treatment solutions that need to be treated separately and require a posttreatment to remove the anti-reflective coating (ARC) from the recovered silicon.
“Furthermore, the KOH step in the double reagent approach has detrimental effect on therecovery yield and purity of recovered silicon,” the researchers said.
For their new process, the academics used only one reagent – phosphoric acid (H3PO4) –which they claimed eliminates the need for all above-mentioned post-treatments. Moreover,this reagent is also always used in the etching paste used for ARC removal and, by targeting
directly the ARC layer, is able to separate the silver (Ag) and aluminum (Al) from the wafersurface.
The scientists said that the proposed technique is able to efficiently leach out the Al anddetach the Ag electrodes from the solar cells, while also being capable of removing the ARC
with minimal generation of precipitates during the treatment. “Use of H3PO4 does not lead toSi dissolution, as seen in both the double reagent approaches,” they explained, noting that
their sample achieved a recovery rate of 98.9% with a purity of 99.2%.
The research group utilized the recycled silicon in a lithium-ion battery anode and found it
performed similarly to new, commercially bought silicon. “The long-term cycling of therecovered silicon managed to retain 62.3% of its initial specific capacity (1086.6 mAh g 1)
after 500 cycles while maintaining high coulombic efficiency of over 99%,” it added,
referring to the performance of the tested storage system.
“The comparable performance between our upcycled silicon-based lithium-ion battery andthe newly purchased ones proves that the NTU approach is feasible,” said Ying. “Weenvision our faster and cheaper silicon recovery method to be a positive boost for thedevelopment of EV batteries. Aside from EVs, there are also potential applications such as
thermoelectric devices.”