Li‐Ions Pre‐intercalation Strategy of Manganese Oxides for Capacitive Deionization‐Based Selective Lithium Extraction From Low‐grade Brine

In this work, Li preintercalated λ-Li_xMnO₂ with tunable lithium content is synthesized, which exhibited excellent electrochemical performance and dual-mode electrochemical storage behavior. Double-layer capacitive and diffusion-controlled Faradaic processes play a role in the charge-discharge process, leading to an enhanced lithium selective adsorption capacity. When employed in hybrid capacitive deionization (HCDI), the λ-Li_1.5MnO₂ obtains a Li⁺ adsorption capacity of 33.68 mg g^-1 in 32.74 mg L^-1 Li⁺ ion solution and low energy consumption of 0.19 Wh g^-1. Moreover, the λ-Li_1.5MnO₂ electrode exhibited outstanding cycling stability, with a significant capacity retention rate of 80% and a manganese mass dissolution rate of 1.2% over 100 intercalation/deintercalation cycles. λ-Li_1.5MnO₂ achieved outstanding lithium selectivity with a separation factor ≈32.7 at a Mg²⁺/Li⁺ molar ratio of 30 in synthetic brine. Importantly, λ-Li_1.5MnO₂ achieved a high Li⁺ adsorption capacity and good selectivity in Lop Nor, the low-grade original brine of the XieLi salt flats, making it a candidate electrode for lithium extraction from low-grade original brine. The pre-intercalation strategy offers a viable option for rationalizing other intercalation electrode materials for electrochemical lithium extraction from low-grade original brine.