Study On Copper Based Lithium Free Anode Of Lithium Ion Battery

Compared with traditional lithium-ion batteries,anode-free lithium metal batterries has great advantages in energy density,cost and safety,so it has attracted extensive attention of many researchers.There is no excess lithium deposited in advance on the anode current collector of the anode-free lithium metal batterries,and all the lithium needed in the battery cycle is provided by the lithium-rich electrode in the initial charging process,and deposited directly on the lithium-free anode current collector.At present,the application of lithium-free anode still faces many difficulties and challenges.The uneven deposition of lithium on the anode current collector leads to the growth of lithium dendrites and the generation of"Dead Li",which reduces the columbic efficiency of active lithium.The solid electrolyte interface film(SEI)formed spontaneously during the battery cycle is constantly broken and repaired.Resulting in a large amount of active lithium and electrolyte consumption,because there is no excess lithium supplement,battery capacity rapidly decay,so seriously affect the cycle life of anode-free battery.To solve the above problems,this thesis modified the copper base current collector by adding artificial interface layer and constructing three-dimensional porous current collector with composite structure,so as to improve the stability of anode interface.The main research contents are as follows:(1)The vacuum evaporation coating was used to artificially add nanometer layer of tin Lipophilic interface on the surface of copper foil,and the mechanism of interfacial coating was analyzed by means of material characterization and electrochemical testing.The results show that the introduction of nano tin interface layer can inhibit the side reaction between the anode active material and the electrolyte,improve the stability of the interface film,reduce the interface impedance and lithium cycle efficiency,and thus improve the cycle life of copper foil anode-free battery.(2)The Sn-CF composite three-dimensional porous copper base current collector was constructed by uniformly depositing a layer of nano-tin particles on the three-dimensional porous copper foam frame by pulsed electrodeposition.The three-dimensional porous structure provided sufficient storage space for the deposited lithium,effectively alleviated the huge volume change during the battery cycle,and reduced the contact resistance between the active lithium and the anode-free current collector.Lithium philic nano tin particles reduce the nucleation barrier of lithium,and provide more nucleation sites for lithium deposition,promote the uniform deposition of lithium,improve the coulomb efficiency and anode stability.the half cell can cycle 200 times stably at 1m A/cm~2-1m Ah/cm~2 and the coulomb efficiency is always maintained above95%.A full battery assembled with lithium iron phosphate(LFP)as electrode can stably cycle for more than 100 times and has 60%capacity retention rate.(3)The Ag-CF composite three-dimensional porous copper base current collector was constructed by growing highly lithium philic silver(Ag)on the three-dimensional porous copper foam frame by a simple combustion method.Thanks to the buffer of the three-dimensional porous structure on the anode volume change and the introduction of highly lithium philic silver nanoparticles,a good lithium deposition morphology was achieved and the impedance of the negative electrode interface film was greatly reduced.The stability of the anode interface and the cycle stability are significantly improved.The half cell can cycle 300 times stably and maintain the coulomb efficiency of more than 95%.