In-Situ Electrochemical Liquid Transmission Electron Microscopy Study Of Zinc Deposition

Rechargeable ion batteries are widely used,but still facing various challenges,such as electrolyte decomposition during battery operation,solid electrolyte membrane formation,dendrite growth,etc.,which exclude them from high power and high performance applications.Understanding the changes in materials during electrochemical processes is beneficial to improve cycle life,charge and discharge performance of batteries.And understanding the behavior of complex electrochemical environments is critical to the development of advanced materials for next-generation rechargeable ion batteries.Dendrites have always been the biggest safety hazard of ion batteries.They will continue to grow after formation,so that they penetrate the separator membrane of the battery,causing internal short circuit of the battery,finally battery failure or even burning.How to understand and study the formation of dendrites from the atomic structure level has always been a research hotspot in the field of materials science.Among them,rechargeable zinc-based batteries have been receiving attention because zinc is inexpensive and abundant,and zinc metal can function in an aqueous environment,which allows zinc batteries to use water-based electrolytes.And zinc batteries are cheaper and safer than non-aqueous electrolytes.In-situ liquid transmission electron microscopy can observe solid-liquid interface changes and perform nanoscale imaging.The experiment use the liquid cell micromachining technology of the research group.The electron microscope sample holder and in-situ liquid cell were processed and modified.Combining with the electrochemical workstation to study the deposition and dissolutionof zinc under cyclic voltammetry and potentiostatic method.The main findings are as follows:(1)The electrochemical liquid cell is designed as a three-electrode structure and processing electron microscope sample holder.Combined with an electrochemical workstation to prove the feasibility of this experiment.(2)In the conditions of cyclic voltammetry(-0.7 V-o V)and potentiostatic inethod(-0.7 V),The deposition growth and dissolution process of zinc dendrite and zinc nanosheets are dedicated to understanding the relationship among dendrite growth,potential and concentration.The process of zincation on the surface of the electrode was observed,and during the process of dendrite dissolution,dead zinc was observed.(3)In the experimental conditions of potentiostatic method(-0.7 V),the growth of nanocages were observed.The two-dimensional projection area of the nanocage was linear with time.The ? value was 0.5.It can be seen that the growth of the nanocage is diffusion control.(4)In the experimental conditions of potentiostatic method(-0.7 V),this experiment observes that nanoparticles move from the solution to the surface of the dendrites,and then continue to grow with the dendrites.The velocity appears to increase and decrease during the movement,which may relate to the electric double layer.(5)In the conditions of cyclic voltammetry(-0.7 V-o V),it is observed that the growth of nanoparticles on the surface of dendrites is related to potential,which is known as electrochemical reaction,not electron beam effect.