Study On Pre-installed SEI Layer And Polydopamine Modified Copper Current Collector Of Lithium Metal Anode

With the rapid development of new energy market,the research of high energy density battery becomes urgent.lithium metal anode is considered as a promising anode for the next generation of lithium batteries due to its high theoretical specific capacity（3860 m Ah/g）and the lowest electrode potential（-3.04 V）.However,dendrite growth and puncture often occur during the cycling process of lithium metal anode,which leads to the decrease of battery capacity and internal short circuit.Based on the above problems,in this paper,the surface of copper collector was modified by pre-set SEI layer and in-situ growth of polydopamine,and lithium metal anode with artificial SEI layer was prepared by electrodeposition.The curing temperature of polyvinylidene fluoride coating on copper foil was80℃and the curing time was 10 h.At 1.0 m A/cm² current density and 1.0 m Ah/cm²lithium deposition capacity,the coulomb efficiency of PVDF coating modified electrode is increased from 85%to 95%compared with blank copper foil.The coulombic efficiency of the composite coating modified electrode was further improved by adding SnF₂ as the active additive,reaching more than 99%;And the cycle life is increased from less than 100 cycles to 230 cycles;It is found that S n²⁺in the composite coating is irreversibly reduced to Sn in the cycling process;The results of half cell and symmetrical cell tests show that the composite coating can reduce the overpotential of lithium nucleation and deposition at about 52 m V and 23m V,respectively,while that of blank copper foil is about 90 m V and 65 m V,respectively.A poly dopamine（PDA）layer was grown in situ on the surface of copper foil collector,and the contact angle between the electrode surface and electrolyte was increased from 37.9°down to 15.2°,The wettability of the electrode surface is improved;The coulomb efficiency of PDA layer modified electrode increased from85%of blank copper foil to 92%;The nucleation overpotential and deposition overpotential of lithium on the electrode surface are about 50 m V and 35 m V,respectively.SnF₂/PVDF composite coating was prepared on the surface of copper foil containing PDA layer.The coulomb efficiency of the electrode was increased to more than 98%at 1.0 m A/cm² current density and 1.0 m Ah/cm² lithium deposition capacity,and the cycle life was increased to 250 cycles.The above research work provides a new idea for the research and development of lithium metal anode.