Construction Of Lithium Metal Anode Based On Structural Design Of Copper Current Collector

Facing the practical needs of high specific energy batteries,lithium metal with extremely high theoretical specific capacity(3861 mAh g-1)and high electronegativity(-3.04 V vs.standard hydrogen electrode)has become a potential alternative material for battery anode.However,during the battery cycling,problems such as dendritic growth and volume expansion in the lithium metal anode lead to poor battery cycling stability,which can result in severe safety hazards during the practical application of lithium metal batteries.In this study,based on the structural design of the copper current collector,the methods to achieve a stable lithium metal anode have been explored through two strategies of surface modification of copper foil and construction of lithiophilic three-dimensional porous copper mesh.The main research results are as follows:(1)A modified copper foil with a surface etching reaction layer was prepared by oxygen plasma eaching copper foil,the main composition of the etching reaction layer is copper oxide with a gradient oxidation degree.The study revealed the influence of the gradient oxide layer on the plating/stripping behavior of lithium metal.The results show that the uniformly distributed nano/submicron particles and voids on the surface of the copper foil can reduce the surface current density of the current collector,guide the orderly deposition of Li,and provide an effective space for Li deposition.The gradient oxide layer can deeply react with Li to become the artificial SEI layer rich in Li2O,which can effectively regulate the transport and transfer of Li+and further control the formation of lithium dendrites.The modified current collector can cycle stably for more than 1100 hours under the conditions of 1 mA cm2 and 1 mAh cm-2,and the average hysteresis voltage is only about 20 mV.(2)A porous copper frame with uniform distribution of meso/macropores was obtained through the dealloying reaction of the brass mesh,and Ag was introduced into the frame by the displacement reaction of Cu and Ag+,finally a copper-based lithiophilic 3D anode frame was constructed.The study revealed the influence of the spatial distribution of Ag in the 3D framework on the plating/stripping behavior of lithium metal.The results show that the 3D porous framework can effectively reduce the current density of the electrode and provide sufficient growth space for lithium metal.Ag can combine with Li to form alloy,which promotes the uniform nucleation of Li and induces Li growth from "bottom to up" in the framework to avoid the volume expansion of the anode and the formation of lithium dendrites.The current collector can cycle stably for more than 1300 hours under the conditions of 1 mA cm-2 and 1 mAh cm-2,and the average hysteresis voltage is only about 10 mV.