Grant Hill1,Chong Liu1
University of Chicago1
Due to the rising demand of Li-ion battery powered vehicles, the lithium supply chain is projected to experience strain in the coming decades. This strain can be mitigated by developing new Li extraction methods that can access unconventional Li sources such as seawater. Electrochemical Li extraction has demonstrated high selectivity and recovery rates from dilute Li sources; the insertion host material selection plays a key role in the overall performance. However, few materials have been explored nor have materials been tailored for Li extraction from these multi-cation solutions. With this in mind, we have explored the role of particle size and morphology of layered cobalt oxide on Li extraction from mixed Li and Na solutions. We have found that large particles form a core-shell structured (NaLi)<sub>1-x</sub>CoO<sub>2</sub> by non-Faradaic ion exchange using parent LiCoO<sub>2</sub> with Na ions. Using electrochemical intercalation, this material successfully extracted Li from 1:20,000 Li to Na aqueous solution to 7.6:1 Li: Na, which is a Li selectivity of 1.5 x 10<sup>5</sup> over Na. Decreasing the particle size, parent Na<sub>1-x</sub>CoO<sub>2</sub> was used to extract dilute Li from an organic solution and maintain high selectivity for multiple Li extraction sequences. After significant structural changes from the first Li extraction, high Li recovery performance can be maintained over multiple extraction sequences. Additionally, we also report C-rate dependence during the intercalation recovery step, indicating the importance of method development for optimizing material performance. This work highlights the importance of understanding the phase separation behavior of Li and Na in layered transition metal oxides for improved Li recovery capacity and lifetime.