Scientists Investigate New Analytical Methods for Upcycling Lithium-Ion Batteries

Scientists Investigate New AnalyticalMethods for Upcycling Lithium-IonBatteries
Published on: September 26, 2023
Caroline Hroncich

The demand for lithium-ion batteries is growing. These batteries, which are used
to power personal electronics, electric vehicles, medical equipment, and more,are made from lithium, cobalt, and graphite, which are typically mined in small
quantities (1).
Because of the limited quantities available of these materials, scientists arelooking for more sustainable methods of manufacture–and a group ofresearchers from the Energy Research Institute at Nanyang Technological
University in Singapore are doing just that (2).
The team, led by Sim Ying, PhD, a research fellow at the Institute, devised amethod for recovering high-purity silicon from expired solar panels to produce
lithium-ion batteries for electric cars. This type of high-purity silicon is often
discarded after 25-30 years, the operational lifespan of a solar panel.
Many traditional methods for separating high purity silicon from solar panels canbe costly and use toxic chemicals. Ying and the team are experimenting with a
new extraction method that uses phosphoric acid, a substance that is common in
the food and beverage industry.
Spectroscopy spoke to Ying about the spectroscopic methods the team used toanalyze the elemental content of the purified silicon wafers and why this kind ofwork is important for sustainability.
The techniques
Ying and the team used a variety of spectroscopy and other methods to monitor
and manufacture lithium-ion batteries. The team first soaked the expired solar
cell in hot diluted phosphoric acid for 30 minutes to remove aluminum and silver.
The process is then repeated using fresh phosphoric acid, which results in a puresilicon wafer. The scientists reported a recovery rate of 98.9% and a purity of99.2%, which is comparable to other currently available methods.
“The team first manually ground the recovered silicon to fine powder to ensure
homogeneity for the subsequent analysis,” Ying told Spectroscopy in an email.
“We have then employed X-ray diffraction (XRD) to qualitatively identify thecrystalline components present in the recovered silicon. To quantify the amountsof residual metals, X-ray fluorescence (XRF) analysis is performed.”
The researchers also used scanning electron microscopy (SEM) with energydispersive X-ray spectroscopy (EDS) to characterize the silicon wafer. This
enabled the capture of high-resolution images on the surface morphology andallows the detection of elemental compositions, Ying said.
“The close-up images provide us with information on the effect of the chemicaltreatment performed on the surface of the wafer,” Ying said. “Additionally, it hasenabled us to identify any precipitate deposit on the surface of the recoveredsilicon.”https://www.spectroscopyonline.com/view/scientists-investigate-new-analytical-methods-upcycling-lithium-ion-batteries

Scientists Investigate New Analytical Methods for Upcycling Lithium-Ion Batteries
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The team also used inductively coupled plasma-optical emission spectroscopy(ICP-OES) to quantify the amount of aluminum, silicon, and silver that wasdissolved in each of the chemical treatments.
“The technique is selected to provide insights on how the changes in chemicaltreatment conditions can influence the dissolution efficiency,” Ying said.
Once the battery is assembled, the team used impedance spectroscopy toevaluate the charge transfer resistance between the electrode’s active material,silicon, and the lithium ions at the electrode-electrolyte interface. The upcycled
silicon performed similarly to new, commercially bought silicon, the researchers
said.
“This method also enables the measurement of electrode ohmic resistance,
which comprises the conduction of lithium ions through the electrolyte andelectronic conduction through the electrode,” Ying said. “By taking all thesemeasurements, we can gain a more insightful understanding of the battery'sperformance.”
The benefits of upcycling
Many of the raw materials used in these batteries are mined from geographicalregions where trade policies could limit the availability of metals and have animpact on prices (1). As the demand of these batteries grows, upcycling, or
creating new products out of waste materials, could provide a viable solution to
help keep prices low and production high.
“Silicon-based anodes are being adopted at a rapid pace by the burgeoning
electric vehicle (EV) industry,” Ying said. “This escalating demand for siliconbased lithium-ion batteries (LIBs) could potentially result in a supply challenge,
given the high purity of silicon that is required. Achieving such high purity
necessitates complex purification processes, like the energy-intensive Siemens
process, which has a considerable carbon footprint.”
This method also makes it easier to dispose of solar panels and can be moreenvironmentally friendly than traditional methods, Ying added.
“By repurposing silicon from waste sources, we not only alleviate disposal
problems but also reduce the carbon footprint associated with solar panels,” Yingsaid. “This approach provides a sustainable source of silicon for lithium-ionbatteries.”
References
1. Mayyas, A.; Steward, D.; Mann, M. The Case for Recycling: Overview andChallenges in the Material Supply Chain for Automotive Li-Ion Batteries.
Sustainable Materials and Technologies 2019, 19,
DOI:10.1016/j.susmat.2018.e00087.
2. Sim, Y.; Tay, Y. B.; Ankit; Lin, X.; Mathews, N. Simplified Silicon Recovery from
Photovoltaic Waste Enables High Performance, Sustainable Lithium-Ion Batteries.
Solar Energy Materials and Solar Cells 2023, 257, 112394.
DOI:10.1016/j.solmat.2023.112394.
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https://www.spectroscopyonline.com/view/scientists-investigate-new-analytical-methods-upcycling-lithium-ion-batteries