Preparation And Electrochemical Properties Of LiF/Li-Sb (or Sn) Artificial SEI Membranes

Lithium metal is considered as one of the most promising anode materials due to its high theoretical capacity of 3860 m Ah g^-1 and minimum reduction potential of-3.04V.However,the serious safety problems and fast capacity decay of lithium anode caused by uncontrolled dendrite growth hinder the practical application of lithium anode.In this paper,Li F/Li-Sb（Li F/Li-Sn）artificial solid electrolyte interface（ASEI）was prepared based on Li F/Li_xM（M=Sb,Sn）materials to solve the dendrite growth problem of lithium anode in lithium metal batteries,and its electrochemical performance was studied.Li Fe PO₄ full battery with lithium metal anode modified which is by Li F/Li_xM（M=Sb,Sn）ASEI has significantly improved the cycle life and capacity retention rate compared with that of Li Fe PO₄ full battery with pure lithium anode.In order to solve the dendrite problem of lithium metal anode and improve the stability of lithium metal anode,Li F/Li-Sb ASEI was prepared successfully.The ASEI consists of Li F phase and lithiophilic alloy（Li-Sb）phase.The Li F phase with good electrical insulation and high mechanical modulus can reduce the probability of electron tunneling through SEI and induce the lateral migration of Li⁺,while the Li-Sb alloy phase with high Li⁺conductivity can promote the rapid passage of Li⁺through ASEI.The synergistic action of the them causes Li⁺to pass through ASEI rapidly and uniformly deposit on the surface of lithium metal anode,thus inhibiting the formation of lithium dendrites.With the protection of the lithium metal anode in this ASEI,the lithium symmetric battery has excellent electrochemical performance in stable plating and stripping(more than 760 hours of cycle for a lithium symmetric battery with a capacity of 1 m Ah cm^-2).The Li Fe PO₄ full battery with Li F/Li-Sb ASEI has a higher capacity retention rate（up to 87.7%after 500 cycles at 1 C）compared with the pure lithium anode.On the basis of the above experiments,in order to further simplify the difficulty of sample preparation,the ASEI of Li F/Li-Sn was prepared successfully,and the influence of the ASEI on the electrochemical performance of lithium metal batteries was studied.The synergistic action of the Li F phase with high mechanical modulus and good electronic insulation and the Li-Sn alloy phase with lithiophilic property gives lithium symmetric batteries good electrochemical performance in plating and stripping(850 h for symmetric batteries with capacity of 1 m Ah cm^-2).Even at a deposition capacity of30 m Ah cm^-2,it still has good cycling performance.Li Fe PO₄ full battery with Li F/Li-Sn ASEI have higher capacity retention（the capacity retention rate is 86.3%after 1000cycles at 5 C）,compared with that of Li Fe PO₄ full battery with pure lithium anode.The prepared lithium metal anode protected by Li F/Li_xM（M=Sb,Sn）ASEI provides an alternative path to develop lithium metal batteries with long life and high safety.