The Electrochemical Properties Of Three Dimensional Porous Metal Oxide-Carbon Composite Coatings

Lithium-ion batteries are among the most important rechargeable energy storage devices with a wide range of applications,such as portable electronic devices and electrical/hybrid vehicles.The development of clean energy vehicles,especially pure electrical vehicles call for new anode materials with higher capacities,better cyclic and rate performance.Some transition metal oxides have received extensive attention due to the higher specific capacity than commercial graphite electrodes.Cu-supported Metal oxide carbon composite coating composite coatings with three dimensional(3D)network structures were successfully fabricated through simple knife coating technique.Three dimensional porous SnO₂-C and ZnO-C composite coatings constructed by interconnected branches were fabricated by annealing Cu foils with films formed by knife coating DMF solution containing SnCl₂ or zinc nitrate,polyacrylonitrile(PAN)and poly(methyl methacrylate)(PMMA)on their surface in vacuum.The electrochemical properties of metal oxide carbon composite coating prepared by this method are studied by studying these two kinds of composite coatings.The composition and phase composition of the composite coating were analyzed by means of XRD,Raman,XPS and TGA test methods.SEM,TEM and bet tests were used to analyze the microstructure of the composite coatings and the situation of the nano pores.Finally,the cycle performance and rate performance of the composite coating were analyzed by electrochemical test.The results show The SnO₂-C composite coating is composed of a porous amorphous carbon base with a width of 0.1-1 mu m.Carbon based branches contain a large number of1-5nm of the size of the micro pores,and a large number of diameter nm 30-100 in the quasi spherical amorphous SnO₂ nanoparticles.The composite coating have high a capacity of642 mAh/g at a current density of 50 mA/g after 100 cycles,they also exhibit impressive rate capability of 533 m Ah/g,463 mAh/g,397 mAh/g,364 mAh/g,314 mAh/g and 276 mAh/g,at current density of 200 mA/g,500 mA/g,1 A/g,2 A/g,5 A/g and 10 A/g.ZnO-C composite coating is also formed by the width of 0.1-1 mu m carbon based branches connected to each other to form a continuous three-dimensional network structure,carbon based branches containing ZnO nanoparticles and size of about 2nm of the micro pores.Under current density of 0.1A/g,the ZnO-C composite coating electrodes exhibit specific capacity of 855mAh/g after 100 cycles without capacity fading during cycling;under high current density of 5A/g,the electrodes deliver specific capacity of 418mAh/g,51.3%of the specific capacity under current density of 0.1A/g.The preparation method is simple in process,and the prepared two kinds of composite coatings have good electrochemical performance,especially excellent magnification performance,so that they have the hope to become the next generation of lithium battery anode material candidates.