High-capacity and selective lithium-ion recovery via Ti3C2Tx@SnO₂ composite electrodes using hybrid capacitive deionization

The increasing demand for lithium in renewable energy storage has underscored the importance of developing sustainable and efficient recovery techniques, with hybrid capacitive deionization (HCDI) emerging as a promising approach through the use of advanced electrode materials. Herein, we outline the facile synthesis and comprehensive characterization of a Ti 3 C 2 T x MXene@SnO₂ composite electrode using SEM, TEM, XRD, FTIR, and XPS analyses to evaluate its performance in Li + ion adsorption compared to other monovalent metal ions (K + and Na + ). The structure–function relationship of the composite electrode was investigated, revealing that the incorporation of SnO₂ nanoparticles into Ti 3 C 2 T x MXene mitigates layer restacking, facilitates ion diffusion, and improves electrical conductivity. The influence of applied voltage and flow rate on lithium-ion transport dynamics was evaluated, revealing a salt adsorption capacity (SAC) of 191.7 mg·g −1 and an ASAR of 0.135 mg·g −1 ·s −1 . In a ternary ion system, the electrode exhibited notable lithium selectivity, with ion removal efficiency ƞ ƞ M values of 42.4 %, 23.2 %, and 28.6 % for Li + , K + , and Na + , respectively, and selectivity coefficients of ρ k Li = 1.82 and ρ Na Li = 1.48 . The recovery studies highlighted a trade-off between high single-ion adsorption capacity and fast surface-driven kinetics of Na⁺ and K⁺, and the stronger, structurally anchored capture of Li⁺ that dominants in competitive ternary system. Moreover, the electrode achieved a SAC of 103.4 mg·g −1 with an initial LiCl concentration set at 5 mM, and retained 82.7 % of this value after 20 adsorption–desorption cycles, demonstrating outstanding long-term cycling stability. These results highlight the Ti 3 C 2 T x @SnO₂ composite as a highly efficient and durable electrode for lithium recovery, offering critical insights into the development of sustainable MXene-based energy storage and desalination technologies.