Release, Transport, and accumulation of lithium in shale brines

In order to mitigate climate change, diversifying the sources of lithium supply is crucial for the decarbonization of energy sector through enhanced renewable electricity generation and electrified transportation. Shale brines have been recently found to be containing significant amount of lithium, but relevant subsurface phenomena regarding its origin, fate, and transport are unknown. Here we present a suite of geochemical experiments to elucidate the initial presence of lithium in shale rocks and its release mechanism from solid phase into fluid, and numerical modeling to estimate the resources of lithium in shale brines by addressing its fate and transport. We find that the majority of lithium is inorganically bound as an interlayer cation of clay in shale rock, while a sparingly small portion is organically bound. Hydrothermal reaction experiments for leaching lithium reveal that calcium ion in fluid has strongest impact on lithium to be released into fluid, while sodium ion has minimal impact. From the numerical modeling combined with the experimental findings, average concentration of lithium in shale brines mimicking Marcellus Shale system is estimated to be about 135 ppm under calcium ion dominancy in pore fluid, which shows excellent match with actually measured values from produced Marcellus Shale brines. This study provides the understanding of fundamental phenomena addressing release, transport, and accumulation of lithium in geologic system, and hence contributes to the enhancement of sources of lithium supply for energy decarbonization.