Tailored LMO@COF composite electrodes for direct electrochemical lithium extraction from high-temperature brines

A composite electrode material, LiMn2O4-Pyr-2D, was designed by combining a 2D pyrazine-linked covalent organic framework (COF), namely Pyr-2D, with LiMn2O4 (LMO). Pyridine (Pyr) was used to form a planar and conjugated structure, which enabled the formation of ordered and stable molecular building blocks with regular pores and uniform element distribution. This structural design effectively mitigated the rate of Mn dissolution and the Jahn-Teller effect-induced structural collapse of LMO at high temperatures, thereby significantly enhancing its resistance to elevated temperatures and improving the efficiency of lithium extraction from geothermal brine. Furthermore, the fast ion diffusion rate at high temperatures was utilized to improve the lithium extraction efficiency. The experimental results demonstrate that LiMn2O4-Pyr-2D exhibited an initial discharge capacity of 154.00 mAh/g in a LiCl solution at 60 ℃ and maintained a capacity retention rate of 92.52% after 20 cycles of lithium extraction in geothermal water from Tibet at 60 ℃. The unit energy consumption was 0.46 Wh/mol with an extraction capacity was 47.03 mmol/g. Overall, this approach introduces a novel and highly efficient method for electrochemically extracting lithium from high-temperature brine.