Li₂Cu₃Zn Ternary Alloy As A Novel Anode Material For Lithium Secondary Batteries

With the increasing demand for longer endurance electronic equipment in modern society,the traditional graphite anode’s low energy density has been confirmed that it cannot satisfy the demand of people’s production and life.Therefore,the task of designing and developing the next generation of higher energy density batteries is urgent.The lithium metal anode（LMA）is considered as the most competitive candidate for the new generation of high energy density negative materials due to its low redox potential（-3.04V vs.standard hydrogen electrode）,low mass density(0.534 g·cm^-3)and ultra-high theoretical specific capacity(3860 m Ah·g^-1).However,lithium metal anode materials inevitably still have many disadvantages.In the cycle process,the lithium metal anode will inevitably produce uncontrolled lithium dendrites,and the continuous development of lithium dendrites will become"dead lithium",reducing the energy density of the battery.At the same time,the battery structure damage caused by volume expansion during the cycle is also one of the inevitable problems.In order to improve the above problems,many modification strategies have been known.In the thesis,a simple and feasible bulk phase modification scheme is selected,and a new composite alloy anode is prepared by a simple metal melting reaction,to achieve uniform deposition of lithium metal,restrain the volume expansion,and ensure that the lithium metal anode has achieved a relatively considerable cycle life and cycle stability.The specific experimental content includes the following three aspects:1.The density functional theory（DFT）calculation verifies the electroplating process of lithium Li||Li battery and Li||Li-Cu-Zn interatomic interactions within the cell;The Li-Zn（100）surface model and Li（100）surface model with the lowest surface energy were established to study the adsorption kinetics of lithium ions.The adsorption structures of lithium atoms with crystal structures of Li,Li-Zn and Li₂Cu₃Zn are shown.2.The Li-Cu-Zn composite alloy anode material with Li₂Cu₃Zn 3D skeleton structure was synthesized.The skeleton structure of Li₂Cu₃Zn ternary alloy can maintain good stability in the electrochemical cycle process,and the existence of active sites of Li-Zn alloy can induce uniform and dense deposition of lithium-ion.The 3D ternary alloy skeleton structure can effectively reduce the local current density in the anode,so the dendrite growth can be effectively inhibited.Li₂Cu₃Zn skeleton can also restrain the volume expansion well,so the overall electrochemical performance of lithium metal battery can be improved.3.Li-Cu-Zn@Foam Ni,a new composite cathode material based on Li₂Cu₃Zn ternary skeleton alloy cathode,was prepared by a simple foam nickel adsorption method.The outer skeleton of nickel foam can contain the lithium metal and restrain the volume change during the electrochemical cycle.In addition,the nickel skeleton is conducive to lower the local current density of the anode to inhibit the lithium dendrites.The Foam Ni outer frame is also good for maintaining the anode structure integrity when running the battery at a high current density.Therefore,the electrochemical performance of Li-Cu-Zn composite alloy anode can be improved based on the previous chapter to achieve longer cycle life and higher cycle stability.