Electrochemical intercalation can enable lithium extraction from dilute water sources. However, during extraction, co-intercalation of lithium and sodium ions occurs, and the response of host materials to this process is not fully understood. This aspect limits the rational materials designs for improving lithium extraction. Here, to address this knowledge gap, we report one-dimensional (1D) olivine iron phosphate (FePO₄) as a model host to investigate the co-intercalation behavior and demonstrate the control of lithium selectivity through intercalation kinetic manipulations. Via computational and experimental investigations, we show that lithium and sodium tend to phase separate in the host. Exploiting this mechanism, we increase the sodium-ion intercalation energy barrier by using partially filled 1D lithium channels via non-equilibrium solid-solution lithium seeding or remnant lithium in the solid-solution phases. The lithium selectivity enhancement after seeding shows a strong correlation with the fractions of solid-solution phases with high lithium content (i.e., Li_xFePO₄ with 0.5 ≤ x < 1). Finally, we also demonstrate that the solid-solution formation pathway depends on the host material’s particle morphology, size and defect content.

电化学插层可以从稀水源中提取锂。然而，在萃取过程中，会发生锂离子和钠离子的共嵌入，而主体材料对此过程的反应尚不完全清楚。这方面限制了改进锂提取的合理材料设计。在这里，为了解决这一知识空白，我们报告了一维 (1D) 橄榄石磷酸铁 (FePO ₄) 作为模型主体来研究共插层行为并通过插层动力学操作证明对锂选择性的控制。通过计算和实验研究，我们表明锂和钠倾向于在主体中相分离。利用这种机制，我们通过非平衡固溶锂晶种或固溶相中的残余锂使用部分填充的一维锂通道来增加钠离子嵌入能垒。晶种后锂选择性的提高与高锂含量的固溶相分数（即 Li _x FePO ₄0.5 ≤ x < 1)。最后，我们还证明了固溶体形成途径取决于主体材料的颗粒形态、尺寸和缺陷含量。