Binder‐Free LiMn₂O₄ Nanosheets on Carbon Cloth for Selective Lithium Extraction from Brine via Capacitive Deionization

Abstract

In this study, a three-step strategy including electrochemical cathode deposition, self-oxidation, and hydrothermal reaction is applied to prepare the LiMn₂ O₄ nanosheets on carbon cloth (LMOns@CC) as a binder-free cathode in a hybrid capacitive deionization (CDI) cell for selectively extracting lithium from salt-lake brine. The binder-free LMOns@CC electrodes are constructed from dozens of 2D LiMn₂ O₄ nanosheets on carbon cloth substrates, resulting in a uniform 2D array of highly ordered nanosheets with hierarchical nanostructure. The charge/discharge process of the LMOns@CC electrode demonstrates that visible redox peaks and high pseudocapacitive contribution rates endow the LMOns@CC cathode with a maximum Li⁺ ion electrosorption capacity of 4.71 mmol g^-1 at 1.2 V. Moreover, the LMOns@CC electrode performs outstanding cycling stability with a high-capacity retention rate of 97.4% and a manganese mass dissolution rate of 0.35% over ten absorption-desorption cycles. The density functional theory (DFT) theoretical calculations verify that the Li⁺ selectivity of the LMOns@CC electrode is attributed to the greater adsorption energy of Li⁺ ions than other ions. Finally, the selective extraction performance of Li⁺ ions in natural Tibet salt lake brine reveals that the LMOns@CC has selectivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>α</mml:mi> <mml:msup><mml:mi>Mg</mml:mi> <mml:mrow><mml:mn>2</mml:mn> <mml:mo>+</mml:mo></mml:mrow> </mml:msup> <mml:msup><mml:mi>Li</mml:mi> <mml:mo>+</mml:mo></mml:msup> </mml:msubsup> <mml:annotation>$\alpha _{{\mathrm{Mg}}^{2 + }}^{{\mathrm{Li}}^ + }$</mml:annotation></mml:semantics> </mml:math> = 7.48) and excellent cycling stability (100 cycles), which would make it a candidate electrode for lithium extraction from salt lakes.