Reviewed by Lexie CornerJul 30 2024
Rice University researchers' most recent study, published in Advanced Functional Materials, offers a speedy, effective, and environmentally friendly approach for selective lithium recovery utilizing microwave radiation and a rapidly biodegradable solvent.
Sohini Bhattacharyya (left) and Salma Alhashim. Image Credit: Gustavo Raskosky/Rice University
Lithium, the “white gold” of sustainable energy, is a fundamental component in batteries of all sizes, from phones and laptops to grid-scale energy storage devices.
Despite its relative abundance, the silvery-white metal could soon be in limited supply due to a complicated sourcing environment caused by the electric vehicle (EV) boom, net-zero aspirations, and geopolitical considerations.
The lithium-ion battery (LIB) global market, valued at more than $65 billion in 2023, is predicted to expand by more than 23 % over the next eight years, exacerbated by existing lithium supply difficulties.
Rice University researchers, led by Pulickel Ajayan, are attempting to improve the environmental impact and efficiency of extracting lithium from discarded batteries.
The results reveal that the novel approach can recover up to 50 % of the lithium in wasted LIB cathodes in as short as 30 seconds, eliminating a critical bottleneck in LIB recycling technology.
We have seen a colossal growth in LIB use in recent years, which inevitably raises concerns as to the availability of critical metals like lithium, cobalt, and nickel that are used in the cathodes.
Sohini Bhattacharyya, Study Lead Author and Postdoctoral Fellow, Rice University
Conventional recycling procedures frequently use harsh acids, while alternative eco-friendly solvents such as deep eutectic solvents (DESs) have battled for efficiency and economic feasibility. Furthermore, existing recycling technologies recover less than 5% of lithium, which is mostly due to contamination and loss throughout the process and the energy-expensive nature of recovery.
The recovery rate is so low because lithium is usually precipitated last after all other metals, so our goal was to figure out how we can target lithium specifically. Here, we used a DES that is a mixture of choline chloride and ethylene glycol, knowing from our previous work that during leaching in this DES, lithium gets surrounded by chloride ions from the choline chloride and is leached out into solution.
Salma Alhashim, Study Lead Author and Ph.D. Student, Rice University
Other metals, such as cobalt or nickel, must be leached using both choline chloride and ethylene glycol. Knowing that only choline chloride can absorb microwaves, the researchers immersed the battery waste material in the solvent and exposed it to microwave radiation.
Bhattacharyya added, “This allowed us to leach lithium selectively over other metals. Using microwave radiation for this process is akin to how a kitchen microwave heats food quickly. The energy is transferred directly to the molecules, making the reaction occur much faster than conventional heating methods.”
Compared to traditional heating methods such as an oil bath, microwave-assisted heating can achieve comparable efficiency over 100 times faster. For example, utilizing the microwave-based technique, the researchers discovered that it took 15 minutes to reach 87 % of the lithium, compared to 12 hours for the same recovery rate using oil bath heating.
Alhashim stated, “This also shows that selectivity towards specific elements can be achieved simply by tuning the DES composition. Another advantage is solvent stability: Because the oil bath method takes so much longer, the solvent begins to decompose, whereas this does not happen with the short heating cycles of a microwave.”
This innovative technology has the potential to significantly improve the economic and environmental effects of LIB recycling, providing a long-term solution to a rising worldwide issue.
This method not only enhances the recovery rate but also minimizes environmental impact, which makes it a promising step toward deploying DES-based recycling systems at scale for selective metal recovery.
Pulickel Ajayan, Benjamin M. and Mary Greenwood Anderson, Professor of Engineering, Rice University
Journal Reference:
Lv, Y., et. al. (2024) Experimental demonstration of magnetic tunnel junction-based computational random-access memory. Advanced Functional Materials. doi:10.1038/s44335-024-00003-3