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

Abstract In this work, Li preintercalated λ‐Li x MnO 2 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 1.5 MnO 2 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 1.5 MnO 2 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 1.5 MnO 2 achieved outstanding lithium selectivity with a separation factor ≈32.7 at a Mg 2+ /Li + molar ratio of 30 in synthetic brine. Importantly, λ‐Li 1.5 MnO 2 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.