Li~+ Insertion/extraction Mechanism Of Manganese-based Gel Electrode And Its Application On Lithium Extraction From Brine

Lithium is widely used in various industrial fields,such as nuclear fusion,battery,ceramic glass,lubricant,cement,and aircraft products,it is a key element of the modern electric vehicle revolution and a very valuable green resource.Lithium ores,brine lake,and seawater contain a large amount of lithium,the former is well utilized and the latter is not effectively developed.If effective lithium recovery technology can be developed,the recovery of lithium ions from aqueous solution will be a huge source of lithium resources.Electrochemical extraction of lithium is a lithium extraction technology assisted by the electric field,which is based on the principle of lithium ion battery and uses special channels of lithium cathode materials to effectively separate Li+from other metal ions.Compared with the traditional lithium extraction technology,electrochemical extraction of lithium has the advantages of high selectivity,low energy consumption,high efficiency,and high energy utilization.In this work,we using the sol-gel method and oxidative chemical polymerization method to synthesize the PPy/Al2O3/LMO composite electrode with double layer structure for the first time.The SEM,HRTEM,XRD,and EDS characterization proved that the particle size of the material was uniform and non-agglomerated,the outer layer of LMO was uniformly covered by Al2O3 and PPy and the boundary is clearly visible,the surface coating of PPy and Al2O3 has not change the crystal structure of LMO.Electrochemical test results in organic electrolytes show that the coating material does not change the two-step reaction mechanism of spinel LMO.PPy/Al2O3/LMO has better discharge capacity,coulombic efficiency,and rate performance than bare LMO.After 100 cycles,the charge transfer resistance of PPy/Al2O3/LMO is lower than that of LMO,indicating that it has good structural stability and cycle reversibility.Study on the mechanism of Li+ insertion/extraction in 1M LiCl aqueous electrolyte.The CV results show that Li+is dominated by diffusion control during the electrode insertion/extraction process.Al2O3 has high electronic conductivity and chemical stability.PPy has the characteristics of good environmental stability,high conductivity,and good redox characteristics.Therefore,the LMO structural stability and reusability are effectively improved during the galvanostatic charge-discharge process,and it has good structural integrity and electrochemical reversibility even at higher rates.Through galvanostatic charge-discharge and ex-situ XRD tests show that the PPy/Al2O3/LMO lattice has no obvious expansion or contraction,the peak shift and intensity changes of the material are reversible,and Li+ insertion/extraction has good reversibility.After multiple charge-discharge cycles,the lattice structure of PPy/Al2O3/LMO is more stable than that of bare LMO.In this paper,PPy/Al2O3/LMO as the positive electrode and activated carbon(AC)as the negative electrode constitute a PPy/Al2O3/LMO//AC asymmetric lithium ion supercapacitor,which has the advantages of high cost-effectiveness,good cycle stability,high selectivity,and high capacity in brine.Circulating lithium extraction was performed in simulated brine.After 15 cycles,the separation efficiency of lithium ions was 97.37%.The amount of lithium extracted in simulated brine was 1.81 mmol/g,and the energy consumption was 1.41 Wh·mol-1 Li+.These results show that PPy/Al2O3 modified LMO has higher extraction efficiency and long-term stability in complex brines.