Construction Of Three-dimensional Cu@Zn-based Materials And Their Performance For Metal Battery Anode

With ever-increasing demand for high energy storage devices,metal batteries have received wide interests due to their high theoretical energy density and specific capacity.However,the issues of Li dendrite growth,volume expansion and side reaction,caused by uneven Li deposition,electrode surface side reaction,and unstable electrode/electrolyte interface,have severely handicapped the application and development of Li metal anodes.So far,many strategies have been developed to solve the above problems,such as designing three-dimensional collector materials,constructing artificial protective layers and modifying electrolytes.Among them,three-dimensional（3D）materials have been concentrated owing to the excellent structural stability,high specific surface area and high porosity.In the process of constructing 3D materials,the rational design of the electrode/electrolyte interface has an important impact on the performance of metal anodes.Synthesis of alloy-type materials（X）is one of the most effective approaches to limit lithium dendrites in Li metal anode（LMA）because of their satisfactory lithiophilicity and easy electrochemical reaction with lithium.However,current investigations have only focused on the influence of the resulted alloyed products（LiX）on the properties of LMA,but the alloying reaction process between Li⁺and X has been mostly ignored.Similar to LMBs,Zn metal battery（ZMB）suffer from uncontrollable Zn dendrite growth during repeated plating/stripping due to uneven zinc deposition caused by unstable thermodynamics,resulting in reduced Zn metal utilization,excessive side reactions,and even battery failure.Therefore,this thesis is based on the study of Cu foam metal collector,which is loaded with zinc metal on its surface and applied to the anode of metal battery to study and solve the problems faced by metal batteries.The research work mainly includes:（1）Manipulation of LiZn alloy process towards preparing high-efficiency lithium metal anodes.By masterly taking advantage of alloying reaction process,a novel approach is developed to effective inhibit lithium dendrites.A three-dimensional substrate material loaded with metallic Zn on the surface of Cu foam was synthesized by a simple electrodeposition process.During Li plating/stripping,both alloy reaction process between Li⁺and Zn and LiZn product are involved,which makes disordered Li⁺flux near substrate first react with Zn metal and then results in even Li⁺concentration for more uniform Li nucleation and growth.The full cell（Li-Cu@Zn-15//LFP）exhibits the reversible capacity of 122.5 mAh g^-1 and a high capacity retention of 95%is achieved after 180 cycles.This work provides a theoretical and experimental foundation for the development of alloy-type materials in energy storage devices.（2）Proposed growth mechanism of spherical Zn metal and its application in high-power Zn metal anodes.In this chapter,graphene quantum dots（GQDs）were electrochemically etched from graphite rods,and the GQDs with a low lattice mismatch for Zn drived the epitaxial Zn deposition,leading to even Zn deposition with more Zn（002）crystal plane exposed.Owing to the abundant negatively charged oxygen-containing functional groups,Zn²⁺is adsorbed around GQDs forming GQDs-Zn clusters in electroplating solution,and then GQDs work as active centers for Zn nucleation and growth,following the subsequent remainder Zn²⁺plating.The resulted spherical Zn metal completely covers the Cu foam substrate under the electro field driving,achieving its uniform deposition.Cu@GQDs@Zn-10 electrode exhibits ultra-long CE stability of 1861 cycles at 5 m A cm^-2 and 1 mAh cm^-2 with the superior average CE of 99.9%.The full cell demonstrates the considerable potential of spherical Zn metal anode for practical applications in ZMB.