The Structural Regulation Of Multilayer Graphene Oxide Film Based On Thermal Diffusion Reduction As Anode For Lithium Metal Batterries

Lithium metal anode is considered as one of the best anode for the new generation of secondary battery because of its high energy density and low reduction potential.However,its practical application restricted seriously by the problems of dendrite and volume expansion of lithium.Constructing a three-dimensional host and optimizing the electrochemical behavior of electrons/ions is one of the effective strategies to solve these problems of lithium.In this paper,a serious of practically reduced graphene oxide film（Pr GO）with three-dimensional structure was prepared by point contact thermal diffusion technique.Using Pr GO as a three-dimensional host for the anode of lithium metal,the influence of its structure on the negative electrode properties of lithium metal was compared,and the influence of Pr GO on the deposition/stripping behavior of lithium and the change of solid electrolyte interphase（SEI）layer were further explored.（1）PrGO with good lithium affinity was prepared by point contact thermal diffusion reduction.At the same time,all kinds of oxygen-containing functional groups on the graphene with the theoretical value of lithium adsorption were regulated by the reduction temperature.Combination with the quantity,type and proportion of oxygen containing functional groups and conductivity of Pr GO.the potential relationships between the conductivity,specific surface area and the electrochemical property were discussed.Pr GO-400 is the optimal host for the synthesis of lithophilicity and conductivity.As results,the uniform lithium stripping/deposition of the composite anode with the best host structure achieved.Then the lithium and graphene composite anode was prepared by self diffusion of molten lithium liquid（Pr GO@Li）,based on the good lithium affinity of Pr GO and capillary action of porous structure.（2）The symmetric battery based on PrGO@Li electrodes maintained a stable cycle of low overpotential under the current density of 5 m A cm^-2 and 10 m A cm^-2.The Pr GO@Li-400 had the lowest overpotential and the longest cycle performance.This is attributed to pr GO-400 being the best value for lithophilicity and conductivity combined.These results were further confirmed by the 2000 stable cycles of low overpotential with 75 m V at 20 m A cm^-2high current density.Through in-situ observation of the stripping/deposition behaviors Pr GO@Li-400 showed uniform stripping/deposition,while the stripping/deposition behavior of Bare Li was uneven.The surface morphology of the stripping/deposition showed that the surface of Pr GO@Li-400 was always smooth,while pits were formed during the stripping of Bare Li,and a large number of dendrites are formed during subsequent deposition.At the same time,the SEI layer on Pr GO@Li-400 surface exhibited a more stable and higher ionic conductivity composition.COMSOL results of lithium ion concentration distribution at the electrode interface and electrode morphology evolution showed that the surface of Pr GO@Li-400 electrode showed uniform lithium deposition,maintained a smooth morphology,and presented higher and more uniform lithium ion concentration distribution on the surface.