Study On Preparation Of Film Electrode With Diversified Modification And Its Application In Lithium Extraction

With the rapid development of lithium battery-related new-energy industries,the supply of lithium resources will not be able to meet the demand for lithium products in the future.In recent years,the electrochemical lithium extraction process based on LiMn₂O₄/Li_1-xMn₂O₄"rocking chair"electrode system has gradually become the research hotspot with its high Li⁺selectivity,commercial and green process.However,its electrosorption efficiency,cycle performance,and energy consumption still need to be improved.This paper researches the two aspects of surface modification and structural optimization.The conductivity performance of traditional electrode materials is enhanced by the modification of the LiMn₂O₄ surface.The N-doped carbon encapsulation LiMn₂O₄ electrode（LMOE@CN-4）is prepared by the in-situ polymerization and high-temperature annealing of PPy,and the N-doped carbon encapsulation layer introduced to the surface of LiMn₂O₄crystal.The results show that the N-doped carbon encapsulation layer effectively reduces the transmission resistance of ions and electrons of LMOE@CN-4,which greatly improves the electrosorption rate of LMO@CN-4,and the average adsorption time is shortened from 120min to about 40 min.In addition,under the high temperature,the crystal structure of LiMn₂O₄is optimized,which improves the Li⁺selective performance of LMO@CN-4,and the Li/Mg separation coefficient increases from 340.91 to 453.08.The carbon encapsulation layer also effectively mitigates the capacity loss of LMOE@CN-4,and the capacity retention rate increases by 23%after 50 cycles.By optimizing the crystal structure of LMO,its electrochemical adsorption of lithium extraction in low concentration Li⁺solution enhances.Hollow porous-LiMn₂O₄（H-LMO）is prepared by the self-template method,and the effect of a hollow porous structure with the large specific surface area of H-LMO is investigated.Compared with the black-LiMn₂O₄（B-LMO）,the specific surface area of H-LMO increases from 3.88 m²/g to 10.89 m²/g,the maximum Li⁺electrochemical adsorption capacity is 39.01 mg/g;the Li/Mg separation coefficient is 581.67.The electrochemical adsorption capacity of H-LMO reaches 11.93 mg/g within 20 min in the solution with a Li⁺concentration of 60 mg/L,and the energy consumption was about 22.62 Wh/mol Li.Compared with the B-LMO electrode,the capacity increases by 213%;the energy consumption decreases by 16%;the average valence state of Mn increases from 3.40 to 3.53.The lithium extraction performance and the cycle stability of the H-LMO are improved.After 50 charge and discharge cycles,the charge and discharge capacity retention rate of the H-LMO electrode increases by about 25%,compared with B-LMO.The surface modification and structure optimization research show that the optimization of internal parameters and external structure of the crystal can effectively improve the lithium extraction performance of LMOE,and enhance the application potential of LiMn₂O₄/Li_1-xMn₂O₄ rocking chair electrode system in low-grade brine...