UNIVERSITY PARK, Pa. — With an electric current and hydrogen peroxide, researchers at Penn State have developed a more efficient way to extract lithium, a key component in the batteries used in electric vehicles and portable electric devices, directly from ore found in the common mineral spodumene. The process could facilitate a 35.6% reduction in cost and a 75.3% reduction in CO2 emissions compared to traditional, less sustainable extraction methods, according to the team, led by Feifei Shi, assistant professor of energy engineering at Penn State.
The researchers published their findings in the journal Nature Communications.
There are two common ways to harvest lithium: through large brine lakes or from lithium ore buried within rock formations. Currently, 70% of lithium is harvested through brines due to its low cost, but both have substantial adverse effects, according to the researchers.
The brine method can take many months and usually involves evaporating large lakes of a highly concentrated salt solution and chemically separating the lithium salt from sodium. Once the solution is completely evaporated, the remaining soil becomes almost barren and cannot support much plant life, according to Zhang.
The other traditional method is to leach lithium from ore, which requires strong acids or bases and extreme temperatures as high as 1,100 degrees Celsius. Under elevated temperatures, spodumene’s atomic density is reduced, so acid can facilitate the chemical reactions needed to replace lithium ions with hydrogen ions, freeing the lithium for extraction. Maintaining that temperature on a commercial scale requires substantial energy consumption, while the need for highly concentrated acid adds additional costs and safety hazards, according to the researchers.
“Firstly, just think of the heavy-duty infrastructure required to withstand that heat daily; it’s costly and a potential danger for workers,” Shi said. “Secondly, we cannot compromise our environment just to produce lithium. The potential of a more sustainable way to create electric vehicles could act as a multiplier and help us achieve net zero emissions.”
The research team’s novel method applies the electrical field to the mineral to electrochemically leach or dissolve the solid-state lithium resources into a soluble, liquid form. Compared to traditional leaching methods, dissolving the ions through electrochemistry does not require elevated temperatures, high pressure or high concentration of leaching agent to change the mineral’s natural state.
In the first trials, the current excited electrons in the mineral, which freed some lithium ions but not enough to scale the approach for an optimized commercial application. Shi recommended using hydrogen peroxide to promote leaching, which would lower the leaching reaction’s barriers and facilitates a more efficient transport of electrons.
In their studies, the researchers observed 92.2% efficiency, which is comparable to traditional methods. However, their method requires less processing time, since the mediator does not add impurities that require additional separation.
“Extracting lithium from brine requires you to wait for the water to slowly evaporate, you cannot control how fast you produce the salt, and you can only generate more by increasing the surface area — so more salt ponds and more adverse effects,” Shi said. “However, with our method we can add as much spodumene as we want and simply increase the electrical current to generate, or accelerate, the leaching reaction.”
Zhen Lei, professor of energy and environmental economics at Penn State and co-author on the study, highlighted the potential reduction in cost and carbon emissions compared to current methods.
“One key factor for the cost saving and emission reduction is that our method involves electricity only and very efficiently, unlike the existing method that uses both electricity and natural gas as energy input,” Lei said. “Another key factor for the cost saving is that our method involves far fewer chemicals. If our method can work well on large-scale lithium extraction, it has great potential to reduce the environmental footprint.”
For Zhang, the next step is to develop an electrochemical method to selectively recover the lithium into solid precursors like lithium chloride or lithium hydroxide that the industry can directly use.
“Leaching is just the first chapter,” Zhang said. “We extracted lithium from ores to water, now we need to develop it into solid phase to complete the story.”
Shi said there is more work and additional research to come at Penn State.
“We really think this is a revolution,” Shi said. “Electrochemistry is going to open the door to a lot of interesting, interdisciplinary research around mining or mineral processing.”
Additional Penn State contributors include Jianwei Lai, a graduate student of energy and mineral
engineering; Yang Yang, assistant professor of engineering science and mechanics; and research assistant Joseph Wolf, undergraduate student of energy and mineral engineering. Ying Han, who was postdoctoral scholar in engineering science and mechanics at Penn State at the time of the research and is now at the University of California Irvine, also contributed.
The research was supported by the Penn State Institute of Energy and the Environment Seed Grant Program, the U.S. National Science Foundation and the U.S. Department of Energy through the Advanced Battery Materials Research Program.