Preparation And Electrochemical Performances Of Li Metal Composite Anodes Based On 3D Lithiophilic Skeletons

Lithium metal anode,due to its ultra-high theoretical specific capacity(3860 m Ah g^-1)and very low electrode potential（-3.04 V vs.H⁺/H₂）,is considered to be the most ideal anode material for high energy density batteries.However,there are some inherent problems such as serious growth of Li dendrites,great change of electrode volume and instability of SEI film in the process of repeated charge and discharge cycle of Li metal anode,which lead to short cycle life of Li metal battery and serious safety risks.In this paper,based on the three-dimensional structural design of the Li metal anode,a high-performance skeleton-type Li metal composite anode is constructed by in-situ growth of the lithiophilic coating on the surface of the three-dimensional skeletons.On this basis,the influence mechanism of the structure stability and electron/ion conduction characteristics on the electrochemical performance of the lithiophilic coating on the three-dimensional skeletons surface was investigated.The main research content of this paper is as follows:（1）Preparation of highly stable lithiophilic skeletons based on MOF-derived nanoarray and its performance of Li metal anode.Ni-MOF nanosheet array was in-situ coated on the surface of commercial nickel foam skeleton.After heat treatment,porous carbon nanosheet array NiO-C was formed,which was derived from MOF and loaded with nano-NiO.Due to the high lithiophilic of NiO and the strong adsorption of porous carbon nanosheet array,the molten Li metal can be quickly filled into the nickel foam skeletons covered by NiO-C nanosheet array（NiO-C@NF）to obtain the skeleton Li metal composite anode NiO-C@NF/Li.The porous carbon nanosheet array structure of NiO-C coating can effectively maintain the stability of NiO lithiophilic sites during Li impregnation and filling and subsequent plating/stripping cycles,thus effectively reducing local current density,accommodating electrode volume strain,promoting rapid,long-term and uniform deposition of Li metal,and inhibiting the growth of Li dendrites.Therefore,the Li plating/stripping efficiency of NiO-C@NF lithiophilic framework is as high as 95.7%;The skeleton-structured NiO-C@NF/Li composite anode battery has very low Li plating overpotential.When the current density and Li plating/stripping capacity are 1 m A cm^-2-1 m Ah cm^-2,3 m A cm^-2-1 m Ah cm^-2and 5m A cm^-2-5 m Ah cm^-2,After stable cycling for 1000 h,Li plating overpotential was～7,26 and 94 m V,respectively.The Li-S battery,which is paired with NiO-C@NF/Li composite anode and sulfur cathode,has a reversible capacity of 650 m Ah g^-1 after 200cycles of 0.2 C,which is significantly better than that of bare Li metal anode.（2）Preparation of Ag-Li₂Se@carbon cloth fiber skeletons with electron/ion mixed conduction and its performance of Li metal anode.Ag₂Se with high lithiophilic was coated on commercial carbon cloth fiber by in-situ growth method.The Ag₂Se coating reacts with the molten Li metal to form Ag and Li₂Se coating with fast electron conduction,and the three-dimensional electron/ion mixed conductivity Ag-Li₂Se@CFC skeletons and the skeletons structured Ag-Li₂Se@CFC/Li composite anode are obtained successfully.Combined with experimental and theoretical simulation results,it is found that Ag nanoparticles in Ag-Li₂Se@CFC skeleton have strong lithiophilic,and can be used as heterogeneous nucleation sites for Li metal deposition,inducing uniform plating and stripping of Li metal in Ag-Li₂Se@CFC skeletons.Due to the synergistic effect of Ag heterogeneous nucleation site and three-dimensional electron/ion mixed conduction path in Ag-Li₂Se@CFC skeleton,the Ag-Li₂Se@CFC/Li composite anode can effectively inhibit the growth of Li dendrites.The symmetrical cell still has excellent cyclic stability and very low Li plating overpotential（3 m V）after 1000 cycles at 1 m A cm^-2 current density.Therefore,Ag-Li₂Se@CFC/Li composite anode and Li Fe PO₄,Li Ni_0.8Co_0.1Mn_0.1O₂,or S/C composite cathode when paired into a button cell,compared with bare Li metal anode,show better cycle stability and rate performance.