Lithium in kerogen, a potential resource and contributor to the global geochemical cycle

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Lithium (Li) resources are crucial for the U.S. to gain a significant market share in future battery production for vehicle electrification and energy storage. Research and development of Li deposits is fundamental to development of this clean energy resource, and in understanding how this valuable element moves through geological systems and is concentrated in economic reserves. Economic and sustainable use of Li reserves is therefore critical to the U.S. prosperity, welfare and national defense. Rechargeable Li ion batteries currently produce 30 GWh per yr of energy, and production trends are projected to increase above 200GWh over the next few years. Along with the U.S., China, Britain, France, India and Norway have announced plans to phase out gas/diesel cars in favor of electric vehicles using Li ion batteries, so it is necessary to ask whether there is sufficient raw materials to meet the growing global demand for Li, and how we can utilize the resources sustainably. Current knowledge of the distribution of Li in organic-rich reservoirs has been incomplete because past methods to isolate organics used acid digestions that also removed organic-Li. Technological advances for in situ chemical mapping of elements led to recognition that significant Li is associated with organics. The objectives of this research are to evaluate the concentrations of organically bound Li in natural kerogen (coal), its chemical properties (organic type, isotopic composition) and thermal stability. With this information Li migration from one source (organic) to another (mineral) can be recognized and may lead to identification of new deposits, and new strategies for Li extraction. The results will contribute to our understanding of the global cycling of Li, and could lead to new 'clean energy' resources for our society.Empirical studies of Li in black shales suggest that organic matter is a significant source of Li, but its role in global geochemical cycles has been largely overlooked. This study will use Nanoscale-Secondary Ion Mass Spectrometry (NanoSIMS) for in situ examination of kerogen at a spatial resolution (50 nm) that can produce maps of carbon vs. silicon rich phases without chemical extractions that alter their Li-content. The hypothesis is that Li is released from the organic matrix at temperatures where clays (ash) form and concentrate Li. To test the hypothesis, investigators will 1) evaluate the Li concentrations and isotopic compositions in the different host phases, 2) conduct hydrothermal experiments on coals to measure Li release from organic phases and isotopic changes, 3) survey variously ranked coals containing Li to determine if Li correlates with organics in lower ranked coals and silicates in the higher ranked coals. The results will document the natural isotopic composition of Li in various types of kerogen and will advance knowledge of organic-Li thermal stability and isotopic fractionation when released to pore fluids. NanoSIMS measurements of Li in nanopores of kerogen will be made to test the hypothesis that released-Li can migrate through these pores, tracing hydrocarbons. This information will help to evaluate the economic potential and thermal extractability of Li from organics. The broader impact to society is a better understanding of Li sources and geochemical cycling, which will enable strategies for extraction of a more sustainable energy source.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.