Study On Modification Of Anode Interface For Anode-Free Batteries

The anode-free batteries have already attracted a lot of research interest due to their high specific energy density.Compared with the current traditional lithium-ion battery,the anode-free battery can greatly increase the energy density and give full play to the advantages of the high specific capacity of lithium metal.In an anode-free battery,all active lithium is initially stored in the cathode material.During the initial charging process,the active lithium is extracted from the cathode to the anode,and is directly electroplated on the bare current collector.Although there is no excessive lithium in the anode-free battery,all active lithium comes from the cathode material,but it still faces many challenges.Among them,uneven lithium deposition will accelerate the growth of lithium dendrites and reduce the utilization of active lithium;the repeated formation of solid electrolyte interface（SEI）will accelerate the consumption of electrolyte and active lithium,resulting in the degradation of battery.To solve these problems,it is very important to propose an effective modification strategy for the anode interface.In view of the above problems,this work was carried out from two aspects:modification of the anode current collector and the addition of an artificial interface layer.Two different interface modification methods were used to modify the current collector of the anode-free battery and further improve the stability of the interface.Modification of the anode current collector structure:construct a three-dimensional porous current collector.Prepare a single-sided honeycomb-shaped porous copper current collector by electrodeposition to reduce the volume change during the lithium deposition/dissolution process and improve the uniformity of local current distribution,thereby improving the stability of the anode interface.By adjusting the conditions of the electrodeposition treatment,a structure with completely different microscopic shapes can be obtained on the surface of the copper foil.The electrochemical performance of the prepared honeycomb porous copper structure is the best,and the cycle efficiency of the Li|Cu battery at a current density of 0.25m A/cm^-2 is increased from 62.6%to 90.7%.Scanning electron microscope results show that the honeycomb-shaped porous copper can effectively uniform the deposition and dissolution process of lithium,and maintain its original structure after cycling.The three-dimensional porous structure of the honeycomb porous copper contributes more space for the deposition of lithium,inhibits the volume change of lithium during the deposition/dissolution process,and improves its cycle stability and shelf stability as anode.Modification of adding artificial interface layer:chemical coating method and ion sputtering method are used to add graphene oxide and gold as artificial interface layer on copper foil.Through the characterization and analysis of the electrode morphology,impedance,and surface film components before and after the cycle,the mechanism of the interface film is studied.The research results show that the graphene oxide and gold artificial interface layer can reduce the reaction activity between the electrode and the electrolyte,thereby improving the stability of the SEI film,reducing the impedance of the interface film,and further improving the stability of the anode interface.