Construction of porous disc-like lithium manganate for rapid and selective electrochemical lithium extraction from brine

摘要

In order to satisfy the growing global demand for lithium, selective extraction of lithium from brine has attracted extensive attention. LiMn_(2)O_(4)-based electrochemical lithium recovery system is one of the best choices for commercial applications because of its high selectivity and low energy consumption.However, the low ion diffusion coefficient of lithium manganate limits the further development of electrochemical lithium recovery system. In this work, a novel porous disc-like LiMn_(2)O_(4) was successfully synthesized for the first time via two-step annealing manganese(Ⅱ) precursors. The as-prepared LiMn_(2)O_(4) exhibits porous disc-like morphology, excellent crystallinity, high Li^(+)diffusion coefficient(average 7.6×10^(-9)cm^(2)·s^(-1)), high cycle stability(after 30 uninterrupted extraction and release cycles, the crystal structure hardly changed) and superior rate capacity(93.5% retention from 10-120 mA·g^(-1)). The porous structure and disc-like morphology further promote the contact between lithium ions and electrode materials. Therefore, the assembled electrochemical lithium extraction device with LiMn_(2)O_(4) as positive electrode and silver as negative electrode can realize the rapid and selective extraction of lithium in simulated brine(adsorption capacity of lithium can reach 4.85 mg·g^(-1) in 1 h). The mechanism of disc-like LiMn_(2)O_(4) in electrochemical lithium extraction was proposed based on the analysis of electrochemical characterization and quasi in situ XRD. This novel structure may further promote the practical application of electrochemical lithium extraction from brine.