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"A new membrane marks an important step toward more efficient extraction of lithium which is needed for reusable batteries. The design can also be used to extract other essential elements like cobalt and nickel. ...
The membrane developed by the team extracts lithium using considerably less energy, while maintaining higher selectivity.
The membrane collects lithium through a process called electrodialysis. An electrical current is applied to the brine which pushes lithium ions to pass through the membrane, whilst other elements like sodium, calcium and magnesium get left behind. ...
The team were able to create such an effective membrane by inserting nanoparticles of lithium titanium oxide (LTO) into it. The crystal structure of LTO is the perfect size for lithium ions to move across without allowing for other elements to pass through. ..."
"... the researchers demonstrated near-perfect lithium selectivity by repurposing solid-state electrolytes (SSEs) as membrane materials for aqueous lithium extraction. While originally designed for the rapid conduction of lithium ions in solid-state batteries — where there are no other ions or liquid solvents — the highly ordered and confined structure of SSEs was found to enable unprecedented separation of both ions and water in aqueous mixtures. ..."
From the abstract:
"Precise separation of ions of the same polarity and similar valence and size remains a critical need in resource recovery from waste streams. Here, we report the rational design and scalable fabrication of a thin film nanocomposite (TFN) cation exchange membrane to achieve precise selectivity for lithium over competing cations.
The precise selectivity is realized by an ultrathin polyamide (PA) layer incorporated with amine functionalized β-monoclinic lithium titanium oxide (N-LTO) nanoparticles using a scalable interfacial polymerization process that allows high N-LTO loading while minimizing interfacial defects.
The TFN membrane demonstrates superior Li+ permeability, with Li+/Ca2+ and Li+/Na+ selectivity reaching 173.90 and 13.58, respectively. The Li+/Na+ selectivity is attributed to the Li+-exclusive transport pathway in the layered structure of the N-LTO, while size exclusion by the highly cross-linked N-LTO-PA also contributes to the Li+/Ca2+ selectivity.
Molecular dynamics simulation shows that the electrical field drives Li+ dehydration and accelerates the migration of the dehydrated Li+ while Na+ is blocked due to its larger size than the Li+ cavity. The high Li+ selectivity and permeability enable energy-efficient, precise, and chemical-free lithium extraction using the electrodialysis process. The TFN membrane architecture also allows simple and scalable fabrication of a multi-functional polymer-inorganic nanocomposite membrane."
Rice researchers develop efficient lithium extraction method, setting stage for sustainable EV battery supply chains (original news release) "Solid-state electrolyte membranes revolutionize lithium harvesting with near-perfect selectivity"
A rationally designed scalable thin film nanocomposite cation exchange membrane for precise lithium extraction (open access)
Fig. 1: TFN-CEM with high and uniform loading of N-LTO.
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