The Mining and Refining Challenges to Produce High Purity Lithium
Delivering high purity lithium for lithium-ion batteries
Scott Hanton is the editorial director of Lab Manager. He spent 30 years as a research chemist, lab manager, and business leader at Air Products and Intertek. He earned...
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Ian Ireland, of Prairie Lithium, holds a PhD in Chemistry from the University of Alberta. He has more than 20 years of industrial experience in fields ranging from ultra-high sensitivity analysis of biomolecules, large scale organic synthesis, and GMP manufacture of cancer vaccines, bioremediation, environmental consulting, waste to energy systems, and industrial wastewater treatment. He has particular expertise in analytical chemistry, as well as product, technology, and process development. In his capacity as lead scientist and corporate officer, he has successfully developed multiple technologies from lab scale to commercial deployment for industrial applications.
Q: Tell me about Prairie Lithium and the key aims of the business?
A: Prairie Lithium is a lithium (Li) brine and technology development company based out of Regina, Saskatchewan, Canada. We use direct Li extraction (DLE) as part of a proprietary process to selectively capture the Li contained in subsurface brines. Subsurface brines consist of ancient seawater, often significantly concentrated via evaporation, that saturates the sediments deposited over hundreds of millions of years in an ancient sea bed that extends through North America east of the Rocky Mountains. These brines lie in multiple layers extending as much as 2-3 km below the Earth’s surface and contain three to eight times the concentration of salts as our modern oceans. Prairie Lithium is currently developing our first commercial project to mine Li from these subsurface brines in SK.
Q: What kinds of businesses are interested in high purity Li?
A: Primarily Li ion battery (LIB) manufacturers and, by extension, the industries that use LIBs to power their products, like electric vehicles, phones, and computers. There are other industries like industrial grease manufacturers and medicine, but they aren’t driving the increase in demand. We are expecting a huge increase in demand for LIBs over the next decade spurred primarily by electric vehicles. Most automakers are developing all electric vehicle fleets, and there is a steady demand for more. Climate change mitigation and air quality improvement are the primary reasons that electric vehicle demand is rapidly rising. The growing demand is expected to significantly outstrip current Li production capability. The demand for LIBs will also impact other metals required for their production like cobalt, nickel, and manganese.
Q: What are the key needs and requirements of these Li customers?
A: The key needs for LIBs are high purity Li salts—either lithium carbonate or lithium hydroxide monohydrate (LiX). While the current standard is 99.5 percent pure Li salt, battery manufacturers really want at least 99.9 percent pure, and are interested in getting 99.99 percent, or even 99.999 percent pure product. Low impurity rates in the Li salts are critical to battery performance and safety. Impurities, like sodium, have led to battery failure, overheating, and fires.
Q: What are the steps you must undertake to deliver high purity Li to customers—from finding to refining?
A: Prairie Lithium is looking at an unconventional Li approach. We have found what appears to be the best Li enriched brine reserves in western Canada. The subsurface brines contain from 15-300 ppm Li, considerably enriched over modern seawater, which contains about 0.2 ppm Li. The Li brines are evaluated by atomic absorption (AA) or inductively coupled plasma (ICP) testing. AA can be an effective field test to find higher concentrations of Li, but ICP is often needed to evaluate the range and concentration of metal impurities. Once interesting sites are identified, we must produce the brine to surface, carry out the DLE process, and then convert the lithium concentrate to battery grade LiX.
The DLE process selectively removes the Li from the brine and returns the rest of the brine to the subsurface layer. The process can selectively remove 99 percent of the Li from the brine and return 97- 99 percent of the contaminant cations to the brine.
Q: What are the key impurities that must be addressed to produce high purity Li?
A: The key cation impurities are essentially the same as found in seawater, but at much higher concentrations: sodium, potassium, calcium, magnesium, etc. Key anion impurities include boron and silicon (as borates and silicates), chlorine, and sulfates.
Q: What is the most challenging aspect of supplying high purity Li to lithium-ion battery customers?
A: Key challenges include finding the right Li reserves, developing new technology to isolate the Li for high purity products, and analyzing materials with trace components in the presence of high concentrations of similar elements.
Q: What types of analytical testing are required—from mining to refining—to satisfy your customers’ needs?
A: The most important is high sensitivity metals analysis. In the brines, we are measuring relatively low levels of Li in the presence of very high concentrations of the other cations. In the purified Li salts, we need to analyze for trace levels of metal cations in the presence of a huge excess of Li. Because Li is “sticky”, we need to significantly dilute the samples to ensure acceptable reproducibility of the measurements, and this requires high sensitivity, low ppb levels, for the other metals.
In addition to the metals, we also need to measure the concentrations of moisture, carbonate, hydroxide, and other anions like chloride and sulfate. Modern ICP-triple quadrupole (QQQ) mass spectrometry methods can provide much of these measurements including chlorine, sulfur, and even carbon. The only element that we can’t really deliver with ICP-QQQ these days is fluorine. We can augment the ICP measurements with titrations for carbonate, hydroxide and Karl Fisher for moisture. The titration experiments are mature and trusted technology.
Another important test is for hydrocarbons. Crude oil can also be found in the same subsurface layers as the enriched brines. It is important to test hydrocarbons down below 1 ppm in the field to protect our extraction process from fouling. Fluorescence is an effective way to measure low levels of hydrocarbon in the field because crude oil has some natural fluorescence, and it can be a very sensitive technique.
Q: What is the most important analytical test required to deliver high purity Li?
A: ICP. For the brine samples, ICP-OES gives the necessary sensitivity. But for LiX purity, we use ICP-QQQ because it gives us the sensitivity to measure impurities down to 0.001 percent.
Q: What improvements in analytical testing will be needed over the next decade or so to enable your business to thrive?
A: Sensitivity is still the key for purity analysis. Current ICP-QQQ instruments can provide what is needed, but we still need standardized protocols for Li analysis that are accepted across the Li industry. Battery manufacturers want certainty that they will receive consistent LiX purity from batch to batch. They also need certificates of analysis (CoA) that can be directly correlated to battery performance. It would be great to have validated data sets accompany the products, so purity results were consistently evaluated. One issue today is that less sensitive techniques can generate higher purity levels on a CoA due to not being able to quantitate all of the very low-level contaminants. The same sample analyzed with ICP-OES, ICP/MS, and ICP-QQQ will show progressively lower purity as more contaminants are quantified with the greater sensitivity of the instruments. It’s not clear where the driving force for standardized testing will originate. It might come from an independent body like ASTM, or it might come from within the industry, like from the battery manufacturers themselves.
