Study On The Morphology Transition Of Zinc And Carbon Nanotubes At The Heterogeneous Interface

Water-based rechargeable batteries are one of the most promising secondary batteries to replace lithium-ion batteries.Zinc metal electrodes have much higher volumetric energy density(5854 mAh L-1)than lithium and stronger compatibility with aqueous electrolytes.These advantages make zinc ion batteries gradually become the focus of research on aqueous batteries.However,the development of zinc-ion batteries has been hindered in terms of both positive and negative materials.The problem of negative electrode materials is particularly prominent.The common negative electrode,namely metallic zinc,will continue to consume zinc ions during the cycle due to corrosion,passivation layer,shape changes,dendrites and other problems,which will cause rapid decline of the overall performance of the battery.The use of neutral electrolyte obviously alleviates the problems of corrosion and passivation layer,but the problems of shape change and dendrites still exist.Researchers have found that zinc presents a unique plate-like deposition form on the few-layer graphene coating.This form of zinc has excellent cycle performance,which opens up a new direction for the regulation of zinc metal behavior.In this study,we took the surface of single-layer graphene grown on copper foil as the research object,and mainly studied the influence of the single-layer graphene interface on the deposition behavior of zinc metal.The research results indicate that:single-layer graphene is sufficient to change the deposition method on the zinc current collector.Under constant current conditions,when there is no graphene,zinc will be three-dimensionally nucleated along the copper steps on the copper current collector.On this basis,as the amount of deposition increases,zinc will be deposited as a loose and porous deposition layer;When graphene exists,zinc preferentially nucleates in two dimensions along the plane of the current collector,and the nucleation method will not be affected by steps and grain boundaries.As the amount of deposition increases,a dense island morphology will be formed.Under constant potential condition with high overpotential(-0.54 V vs Zn2+/Zn),the distribution of zinc nucleation and growth will be more uniform.When there is no graphene interface,zinc presents a tendency to nucleate and grow perpendicularly to the electrode plane,while on the graphene surface,zinc presents a way of nucleation and growth parallel to the electrode,which shows that the single-layer graphene interface does have the ability to control zinc deposition behavior,which can induce flat plate deposition of zinc during the nucleation stage.Structurally,the graphene interface can promote the preferential formation of the(002)plane of zinc.In addition,we have successfully obtained a large number of carbon nanotube rings with ring diameters ranging from 100 nm to 200 nm through the high-temperature reaction at the interface of carbon nanotubes and lithium nitride.In this reaction,600?is the critical temperature for obtaining carbon tube rings.Excessive lithium nitride or too high temperature will etch the carbon nanotubes,and only single-walled carbon nanotubes can be used to obtain carbon nanotube rings.Both of these two works involve the interaction of carbon-based materials with metals or metal compounds at the heterogeneous interface,providing new possibilities for the microscopic morphology control of materials.