The Preparation And Properties Of Preset Solid Electrolyte Membrane Metal Lithium Anode

Compared to conventional lithium ion battery?LIB?anode materials,metallic lithium?Li?has a higher theoretical specific capacity?3860 mAh/g?and a low electrochemical potential?3.04 V?.Therefore,Li anode has long been regarded as the ultimate solution for high-capacity energy storage systems.However,Li anode is facing many challenges in actual use.For example,due to the low diffusion capacity of lithium ions on the surface of lithium metal,Li dendrites are easily generated during the deposition process,which easily cause short circuits in the battery;and as the cycle progresses,the solid electrolyte interface?SEI?is repeatedly broken and formed,consuming electrolyte,resulting in capacity attenuation.Therefore,it is necessary to develop an effective Li anode protection technology to inhibit the growth and stable interface of Li dendrites.In this thesis,a man-made SEI is preliminarily placed on the surface of the negative current collector by a simple design process,and the Li anode protected by a preset SEI is obtained by electrodeposition.A method of preparing a preset solid electrolyte interface?PSEI?was designed by experiments.The steps of current collector pretreatment,coating liquid preparation,coating film solidification,assembled battery,and Li electrodeposition were sequentially performed.First,a SEI and a PSEI/Li anode were successfully prepared.A PSEI using MOF?UIO-66?,polydopamine?PDA?,LiF,lithiumbis?trifluoromethanesulphonyl?imide?LiTFSi?,nano-Al₂O₃,and LiF+LiTFSi+nano-Al₂O₃?ALL?as additives was prepared.Among them,the SEI with ALL as an additive exhibits the most excellent electrochemical cycle stability performance under a half-cell.In the first 230 laps,the capacity retention rate reached98%.The amount of ALL added was optimized by orthogonal experiments.Under the cycling conditions of 0.5 mA/cm² and 1 mA h/cm²,the PSEI based on the best addition amount of ALL exhibited a long cycle of 280 cycles in the Li-ALL/Cu half-cell,and its coulomb efficiency?CE?is maintained at around 99%.A PSEI/Li anode?ALL/Li/Cu?was prepared and assembled with LFP,S cathode materials ALL/Li/Cu-LFP,ALL/Li/Cu-S full cell,among which ALL/Li/Cu-LFP full battery shows good cycle stability?CE of about 98%?and good capacity retention?90%?after 100 cycles at 1 C current density,and is compared with Li-LFP Group,which has less polarization performance.The ALL and ALL/Li/Cu were analyzed by XRD,XPS,SEM and other test methods.The SEM test results show that the surface of the Li deposited has a flatter topography;The XRD test results show that the PSEI has excellent stability before and after the cycle;The XPS results show that ALL isolates the electrolyte from contact with Li to some extent,thereby suppressing side reactions between them.Through these test results,it can be concluded that the PSEI prepared by the experiment has certain effects on inhibiting dendrites on the surface of Li.