Construction And Electrochemical Performances Of LithiophiLic Protection Films On Lithium Metal Anode Surfaces

Lithium metal cathode is known as the"holy grail"cathode for lithium secondary batteries due to its extremely high theoretical specific capacity(3860 mAh g^-1)and lowest electrode potential（-3.04 V vs.H⁺/H₂）.However,the application of lithium metal anode is currently limited by several major defects,including large volume changes during charging and discharging,unstable native SEI film,disordered growth of lithium dendrites,and pulverization of the electrode structure,resulting in short cycle life,low Coulomb efficiency,and safety hazards of lithium metal anode.In this paper,we construct a lithium-philic interfacial protection layer at the interface of lithium-metal anode to promote the uniform deposition of lithium metal and obtain a high-performance lithium-metal anode from the interfacial protection of lithium-metal anode.The specific research work is as follows:（1）Construction of lithium-philic Ag cladding layer at the lithium-metal anode interface and its performance study.AgNO₃ solution is applied dropwise to the lithium metal anode interface,and the lithium reduction reaction is used to form a lithium-philic Ag cladding layer at the lithium anode interface.The super-lithium-philic Ag can reduce the deposition overpotential of lithium metal at the anode interface and promote the uniform deposition of lithium metal.In addition,the reaction of AgNO₃ and lithium metal to form LiNO₃ can further improve the Li⁺conduction at the anode interface and improve the cycling stability of the lithium metal anode.Therefore,the obtained symmetric cell with Ag@Linegative electrode has a lithium deposition overpotential of～7 mV after 1200 h of stable cycling at a current density and lithium deposition/stripping capacity of 2 mA cm^-2-1 mAh cm^-2.The Li-S cell with Ag@Licomposite negative electrode and sulfur cathode pairing still has a reversible capacity of 600 mAh g^-1 after 200 cycles at 0.2 C.The performance significantly better than that of the pure Li-metal cathode.（2）Construction of lithium-philic Ag/polymer cladding layer at lithium-metal anode interface and its performance study.A mixed solution of AgNO₃ and polymer was drop-coated onto the lithium-metal anode interface to form a lithium-philic Ag/polymer composite cladding layer.This inorganic-organic composite protective layer not only exhibits the super lithium-philic property of Ag and the fast ion conduction property of LiNO₃,but also has the excellent mechanical flexibility of polymer,which can effectively maintain the structural stability of the lithium-philic interfacial protective layer.Therefore,the obtained Ag/PEG@Lianode can effectively inhibit lithium dendrite growth,obtain uniform lithium deposition/exfoliation morphology,and exhibit excellent cycling stability.the symmetric cell with Ag/PEG@Lianode has a lithium deposition overpotential of～7 mV after 2000 h of stable cycling at a current density and lithium deposition/exfoliation capacity of 2 mA cm^-2-0.5 mAh cm^-2.the Ag@Licomposite negative electrode and high nickel ternary NCM811 cathode paired button cell with discharge capacities of 181,145,137,128,and 102 mAh g^-1 at 0.1,0.2,1,2,and 5 C,respectively;reversible capacities of 163and 153 mAh g^-1 remain after 150 cycles at 0.5 and 1 C.