Interface Structure Design And Electrochemical Properties Of Zinc Metal Anodes For Aqueous Battery

Aqueous zinc metal batteries（AZMB）show great application prospects in grid-scale energy storage due to their advantages of high intrinsic safety and low cost.However,the practical application of AZMB has been hampered by many challenges,including inhomogeneous electrochemical plating of metallic Zn and corrosion side reaction of Zn metal in aqueous electrolyte.To address these issues,this dissertation aims to improve the electrochemical/chemical stability of metallic Zn through the rational design of Zn metal anode interfacial structure and regulation of the operation conditions.The main achievement of this thesis is as follows:1.To solve the problem of inhomogeneous electrochemical plating of metallic Zn caused by the multi-component native passivation of commercial Zn foil,a Zn metal anode with fresh interface is prepared by a simple chemical polishing strategy,and the effect of the fresh interface on the nucleation and growth of metallic Zn during electrochemical deposition is investigated.The fresh interface of Zn electrode enables the uniformity of the electric field on the electrode surface,and increases the electrochemically active area of the electrode,which help to realize the homogeneous plating of metallic Zn.Due to these effects,the polished Zn anode cycles stably for over 200 h at 1 m A cm^-2 and 0.50 m Ah cm^-2.2.To address the issue of corrosion,a zinc oxalate interfacial layer is in situ grown on the surface of Zn metal foil during chemical polishing process.A stable interfacial layer is constructed while removing the native passivation,helping to achieve a corrosion-resistant and dendrite-free Zn metal anode.This interfacial layer can effectively avoid the direct contact between the Zn metal electrode and the aqueous electrolyte,thus reducing the corrosion of metallic Zn.At the same time,the high resistivity and high ionic conductivity of the interfacial layer promote the deposition of metallic Zn below the interfacial layer,avoiding the uneven deposition of metallic Zn.Due to the dual effects of the zinc oxalate interface layer,the as-achieved Zn electrode exhibites stable cycling for 400 h at 5 m A cm^-2 and 1 m Ah cm^-2.Pairing with a Mn O₂ cathode,the cells show cycling stability under 0.50C for 100 cycles with 86.27%capacity retention.3.To further inhibit the corrosion and promote the electrodeposition uniformity of Zn metal anode,a texture modulation strategy is developed to change the growth behavior of corrosion products and metallic Zn deposit.A highly stable interfacial layer is generated on the surface of Zn metal anode,improving its electrochemical stability.Experimental results and theoretical calculaions reveal that the conformal growth of zinc hydroxide sulfate（ZHS）with dominating（001）facet is realized on（002）plane-dominated Zn metal foil for the good lattice match with each other.The ZHS possesses high Zn²⁺conductivity and low electronic conductivity,and works as a heterogeneous interface layer of metallic Zn electrode,which regulates electrochemical Zn plating behavior and suppresses side reactions simultaneously.Moreover,low self-diffusion barrier along（002）plane promotes the 2D diffusion and the horizontal electrochemical plating of metallic Zn for（002）-textured Zn electrode.Consequently,the as-achieved Zn electrodes exhibit remarkable cycling stability for 7000cycles at 2 m A cm^-2 and 0.50 m Ah cm^-2 in symmetric cells.The Mn O₂|Zn cells exhibit cycling stability for 1000 cycles under 10 C with 92.74%capacity retention.This work has suppressed the corrosion side reaction in aqueous Zn metal batteries by using texture modulation,which promotes the development of high performance Zn metal anodes.4.To investigate the influence of the operation conditions on the electrodeposition behavior of metallic Zn,the dynamic deposition process of metallic Zn is in situ observed using an optical microscope system,and the critical parameter governing the electrodeposition stability of the metallic Zn are uncovered.The critical parameters governing the electrodeposition stability of the metallic Zn electrode are uncovered,that is,the competition among crystallographic thermodynamics and Zn²⁺-ion diffusion.High electrolyte concentration facilitates the ion diffusion,leading to a densely packed morphology with high conformity for the deposits at high current densities.Significantly,a long-term cycling-stable Zn metal electrode is realized under 50 m A cm^-2 in both Zn||Zn symmetrical cells and Mn O₂|Zn full cells.The findings in this work shed light on the fundamental understanding of Zn metal nucleation and growth under various battery operating conditions,guiding the design of high-power and long-cycling Zn metal batteries.