LiMn₂O₄ (LMO) electrochemical lithium-ion pump has gained widespread attention due to its green, high efficiency, and low energy consumption in selectively extracting lithium from brine. However, collapse of crystal structure and loss of lithium extraction capacity caused by Mn dissolution loss limits its industrialized application. Hence, a multifunctional coating was developed by depositing amorphous AlPO₄ on the surface of LMO using sol-gel method. The characterization and electrochemical performance test provided insights into the mechanism of Li⁺ embedment and de-embedment and revealed that multifunctional AlPO₄ can reconstruct the physical and chemical state of LMO surface to improve the interface hydrophilicity, promote the transport of Li⁺, strengthen cycle stability. Remarkably, after 20 cycles, the capacity retention rate of 0.5AP-LMO reached 93.6% with only 0.147% Mn dissolution loss. The average Li⁺ release capacity of 0.5AP-LMO//Ag system in simulated brine is 28.77 mg/(g h), which is 90.4% higher than LMO. Encouragingly, even in the more complex Zabuye real brine, 0.5AP-LMO//Ag can still maintain excellent lithium extraction performance. These results indicate that the 0.5AP-LMO//Ag lithium-ion pump shows promising potential as a Li⁺ selective extraction system.