Fabrication And Electrochemical Investigation Of MWO₄?M=Co,Ni? Nanoparticles As High-performance Anode Materials For Lithium-ion Batteries

In recent years,with the increasing demand for clean energy,people pay more and more attention on various kinds of green energy storage equipments.The lithium-ion batteries?LIBs?has been used as the most promising energy storage technology because of its high energy density,high power density,long cycle life,safety,environment friendly and other advantages,widely used in all kinds of intelligent electronic equipments,electric bicycles,electric automobiles and other fields.In recent years,the majority of scholars devote themselves to the research and development of new electrode materials for lithium ion batteries.However,the commercial graphite electrodes with low energy density and poor safety performance limit the development of the lithium-ion batteries in some degree.So in recent years,many scholars devote themselves to the exploitation and improvement on anode materials for lithium-ion batteries,which is in order to satisfy the growing requirements for high performance LIBs and ensure the demands of the market.Tungsten?W?,as an important component element of modern high-tech materials,has been widely used in many fields,such as electronic optical materials,new functional materials,special alloys and organic metal oxides.In the field of new energy materials,tungsten compounds,such as oxides,nitrides,and oxysalts,have been proved to be feasible anode materials for lithium-ion batteries.Double metal tungstates as a part of the tungsten oxysalts,such as Fe WO₄,Mn WO₄ and Zn WO₄,their lithium storage performances as anode materials for lithium-ion batteries have been demonstrated.The cobalt tungstate?Co WO₄?and nickel tungstate?Ni WO₄?as typical double metal tungstate,which has been applied to various catalysts,dielectric ceramics and supercapacitors,but their lithium storage performances as anode materials for lithium-ion batteries has rarely been reported,so we decided to adopt appropriate methods to synthesis of Co WO₄ and Ni WO₄ samples and explore their electrochemical properties as anode materials for lithium-ion batteries.In this paper,the main research is as follows:In this work,the Co WO₄ and Ni WO₄ samples were successfully synthesized by a facile one-step hydrothermal method.The micromorphology of obtained Co WO₄ and Ni WO₄ samples was uniform nanoparticles with the size of 40 60 nm by structural characterization including X-ray diffraction?XRD?,scanning electron microscopy?SEM?,energy dispersive spectrometer?EDS?and transmission electron microscopy?TEM?.When tested as anode materials for lithium-ion batteries,Co WO₄ nanoparticles exhibited a stabilized reversible capacity of 980 m Ah/g at 200 m A/gafter 120 cycles and 632 m Ah/g at 1000 m A/g even after 400 cycles.And the discharge capacity was as high as 550 m Ah/g at 400 th cycles for Ni WO₄ nanoparticles.Two tungstates all show excellent electrochemical performance,which is not only attributed to the synergy of different metal elements but also due to thier unique microstructure,uniform size and morphology.On one hand,the unique structure can shorten the diffusion length for electrons and lithium ions and increase the contact area of the electrode and the electrolyte,which can enhance the capacity and rate performance of materials.On the other hand,also can effectively alleviate volume expansion caused by lithium-ion insertion and extraction during charge-discharge process,prevent the electrode material powder and maintain conductive network integrity,which can enhance the cycle performance of materials.