Author(s): Kevan Williams
Mentor(s): Jason Porter
Institution BYU
Effectively recycling spent batteries is essential to a sustainable energy future. The primary purpose of battery recycling is the recovery of precious metals like Lithium (Li), Nickel (Ni), Cobalt (Co), and Manganese (Mn). One method for battery recycling is pyrometallurgy, which uses extreme heats to melt down batteries, this requires high amounts of energy and loses precious metals in the process. Another method for battery recycling is hydrometallurgy, which uses solvents to leach precious metals from batteries. However, many promising solvents for hydrometallurgy are volatile and/or toxic which creates environmental and waste management challenges. This research focuses on hydrometallurgy using deep eutectic solvents (DESs). DESs are composed of a hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) that, when mixed, form a liquid with lower melting temperatures than either of the two original components. Many DESs are benign and biodegradable, which reduces the chemical hazards and waste management challenges associated with current hydrometallurgical methods. Previous research has shown that DESs can effectively leach precious metals from spent batteries. Leaching metals with DESs requires time, but the addition of heat can accelerate the dissolution kinetics and facilitate leaching. Increased temperature can cause degradation of the DES, making it unsuitable for industrial use. This research will show which DESs will be stable for industrial use. This research assesses the thermal stability of various deep eutectic solvents using spectroscopic methods. Infrared (IR) spectroscopy is typically used to characterize the chemical bonds in a substance. UV-Visible (UV-Vis) spectroscopy is often used to identify color changes. Changes in the IR and UV-Vis spectra of a DES when exposed to heat indicate that thermal decomposition has occurred. These methods provide rapid screening for thermal decomposition of potential solvents. DESs have been provide by researchers at the Colorado School of Mines, and spectroscopic measurements of DESs have been taken during heating, as well as post-cooling. Spectral results show that most DESs are thermally stable, however a small number experience degradation. This data facilitates battery recycling by providing an assessment of which DESs are thermally stable and which are not. These results are shared with partners who will choose the best DESs based on other factors such as leaching efficiency and solubility.