Hydrophilic Modification Using Polydopamine on Core–Shell Li_1.6Mn_1.6O₄@Carbon Electrodes for Lithium Extraction from Lake Brine

Abstract

Lithium extraction from salt-lake brine is important to ensure a sustainable supply of lithium and meet its increasing demand for use in electric vehicles and large-scale energy storage devices. However, it remains challenging to separate Li+ ions from coexisting ions in the brine. Here, we propose a combined strategy of a core–shell structure and hydrophilic modification of a Li1.6Mn1.6O4 electrode to efficiently extract lithium from brine with a high sodium ion content. Core–shell Li1.6Mn1.6O4@carbon was derived from polydopamine-encapsulated Li1.6Mn1.6O4 via calcination. The ∼2 nm carbon shell protects Mn from leaching during lithium extraction. Compared with bare Li1.6Mn1.6O4, the lithium extraction capacity of the modified electrode increases from 20 to 39.6 mg/g in a brine with a high Na–Li ratio (Na/Li = 44.78 by weight). The coating of polydopamine on the Li1.6Mn1.6O4@carbon electrode reduces the water contact angle from 119 to 86.9°, resulting in a hydrophilic surface. Using an electrochemical adsorption method, the lithium extraction capacity and desorption ratio reach 65.6 mg/g and 86.0%, respectively, which are superior to the performance of the current membrane capacitive deionization and electrochemical method. The modified electrode shows high lithium-ion selectivity and excellent stability due to the reversible redox reactions during lithium extraction/release. The strategy proposed here provides insights into the structural design of electrodes for the highly efficient separation of lithium from brine.

Direct Lithium Extraction Using Intercalation Materials

“…Intercalation materials have been reported for use in ionexchange adsorption to extract Li + from brines. These materials in many cases have been manganese or titanium oxides, including LiMn 2 O 4 , [63] Li 1.33 Mn 1.67 O 4 , [64,65] Li 4 Mn 5 O 12 , [66] Li 1.6 Mn 1.6 O 4 , [63,67,68] and its combination with Li 2 MnO 3 or MnO 2 , [69] Li 2 TiO 3 , [70][71][72][73][74] and Li 4 Ti 5 O 12 . [75,76] Titanium-based intercalation materials have generally reported greater stability than manganese-based materials, particularly with regards to resisting dissolution in acidic solutions.…”

Bifunctional Modification Enhances Lithium Extraction from Brine Using a Titanium-Based Ion Sieve Membrane Electrode

“…Despite their individual limitations, combining two or more traditional technologies or using them in tandem may simultaneously achieve high separation efficiency and high extraction capacity . Reported examples include the reaction-coupled separation technology , and electrochemically switched ion exchange. , We have previously proposed an adsorption-coupled electrochemical technique that combines lithium-ion sieves with an external electric field, resulting in excellent lithium extraction ability without using acids. , …”

“…16,17 We have previously proposed an adsorption-coupled electrochemical technique that combines lithium-ion sieves with an external electric field, resulting in excellent lithium extraction ability without using acids. 18,19 Mn-based ion sieves have been developed for Li + extraction. Due to the special electronic structure of Mn 3+ , the Jahn− Teller effect causes severe lattice structure distortion of the LiMn 2 O 4 precursor in an acidic environment.…”

Electrochemical Lithium Extraction with Gas Flushing of Porous Electrodes

“…Most of the previous research on electrochemical lithium extraction focused on improving electrode materials [20][21][22][23][24] and optimizing charging and discharging conditions [25][26][27]. The researches on electrochemical lithium extraction operating system are very limited.…”