Single Lithium-Ion\nConductor Decorated LiMn<sub>2</sub>O<sub>4</sub> with High Selectivity\nand Stability for Electrochemical\nLithium Extraction

Spinel LiMn<sub>2</sub>O<sub>4</sub> (LMO) is commonly\nused for\nelectrochemically extracting lithium ions from brine. However, its\ncycle stability is significantly reduced due to Mn<sup>2+</sup> dissolution.\nHere, we report high-performance LMO particles decorated by Li<sub>1.5</sub>Al<sub>0.5</sub>Ge<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> (LAGP) as an electrode for electrochemical lithium extraction. Compared\nwith bare sample, the modified electrode presents higher Li-ion selectivity\nbecause LAGP is a single Li-ion conductor, and as a result of avoiding\nthe cointercalation of other ions in brine, the sample exhibits a\nhigher Li-ion extraction capacity of 2.44 mmol·g<sup>–1</sup>. The cycling stability is also improved in LMO with LAGP coating\nby alleviating the loss of manganese, indicating a reduced Mn loss\nof 0.20% after 100 cycles compared to the LAGP free counterpart of\n0.47%. Our work demonstrates an effective method for lithium purification\nfrom brine, and the detailed mechanism is also studied systematically.