Precisely size-controlled nanoporous LiMn2O4 for enhanced lithium extraction via hybrid capacitive deionization

Hybrid capacitive deionization (HCDI) employing LiMn 2 O 4 (LMO) electrodes is a promising approach for Li + extraction from brines, where rational structural engineering of LMO is essential for performance improvement. In this study, we developed a co-precipitation-calcination strategy to synthesize nanoporous LMO (NLMO), in which calcination temperature control enables controlled particle growth and structural optimization. The optimized NLMO, benefiting from its tailored particle size, crystallinity, and porous structure, exhibits markedly enhanced Li + adsorption. With a large specific surface area of 80.15 m 2  g −1 , it provides abundant active sites and thus achieves an adsorption capacity of 29.31 mg g −1 at 1.0 V. In addition, the downsized particle dimension shortens Li + diffusion paths, boosting the adsorption rate to 1.46 mg g −1  min −1 . Notably, the porous structure buffers volume expansion during cycling, enabling the electrode to maintain structural stability. As a result, the NLMO electrode maintains 83.04 % of its capacity even after 1000 consecutive charge–discharge cycles. In addition, a high separation factor of 233.63 was achieved for Li + /Mg 2+ in brine with a Mg 2+ /Li + ratio of 20. Application studies further confirm that the electrode effectively recovers high-purity Li + from simulated salt lakes (Baqiancuo, Silver Peak, Uyuni, and Dong Taijinar) and actual low-grade oil and gas field produced water. These results demonstrate that the optimized NLMO demonstrates significant potential as a high-performance electrode for selective Li + extraction from different raw solutions.