Interfacial-lattice coupling in AlF₃-modified LiTi₂(PO₄)₃ enables highly selective lithium extraction via hybrid capacitive deionization

With the booming new energy industry causing lithium scarcity, high-efficiency lithium extraction from salt-lake brines has become a global research focus. Hybrid capacitive deionization (HCDI) offers an energy-efficient and operationally simple strategy for selective Li⁺ recovery from salt-lake brines. However, as a promising intercalation electrode candidate for such HCDI systems, the bottlenecks of LiTi₂(PO₄)₃ (LTP)-based electrodes are their limited Li⁺ adsorption capacity and selectivity, caused by increased lattice constants. Herein, AlF₃-coated LTP with a reduced lattice constant is constructed by combining co-precipitation, sintering, and AlF₃ deposition, enhancing both its Li⁺ adsorption capacity and selectivity. Compared to the pristine LTP, 2 wt% AlF₃-coated LTP (LA-2) exhibits a higher Li⁺ diffusion coefficient and lower intercalation energy, leading to higher capacity, greater selectivity, and lower energy consumption. In an HCDI system, LA-2 achieves a Li⁺ intercalation capacity of 24 mg g⁻¹ and a low Li⁺ extraction energy consumption of 2.59 Wh mol⁻¹. In the brine of natural salt lakes in Tibet, LA-2 shows excellent selectivity for Li⁺ over Na⁺, Mg²⁺, Ca²⁺ and K⁺ with a coefficients of 144, 104, 89 and 78, respectively. These findings demonstrate that AlF₃-coated LTP with a reduced lattice constant delivers high potential for electrochemical lithium extraction in practical applications.