Performance and mechanism of ether-based binder (KH-PE) in electrochemically switched ion exchange lithium extraction from salt lake brine with high Mg/Li ratio

The high Mg/Li ratio is a core bottleneck leading to the low efficiency of lithium extraction from salt lake brine using Electrochemically Switched Ion Exchange (ESIX) technology. As a key component in the ESIX system, the binder significantly influences ion separation performance. This study employs KH-PE, which contains ether groups, as a binder to fabricate a LiMn 2 O 4 /C/KH-PE composite film electrode. Experiments show that compared with the LiMn 2 O 4 /C/PVDF film electrode prepared with the traditional PVDF binder, this composite film electrode exhibits excellent magnesium ion transport inhibition in high Mg/Li ratio solutions. Based on these findings, this paper further explores its underlying mechanism, attributing it to the strong interaction between the ether groups and magnesium ions. This interaction induces the formation of Mg 2 + -rich interfacial region on the film surface during the adsorption process, thereby effectively repelling magnesium ions from the solution through the Donnan effect. ESIX experiments conducted in brine demonstrate that the LiMn 2 O 4 /C/KH-PE film electrode achieves a high Mg/Li separation factor of 2538, showing excellent lithium selectivity. In summary, the application of the ether-containing KH-PE binder provides an effective approach to overcome the challenge of competitive adsorption between magnesium and lithium under high Mg/Li ratio conditions.