Preparation And Performance Of Graphene-based Tungsten Oxide Composite Anode Materials For Li-ion Batteries

Carbon is an important ingredient of consisting all kinds of things, and also a major element of constituting all the life in nature. Graphene is a new member of the carbon family, it is a two-dimensional that consists of a single layer of carbon atoms. A lot of scientists have carried out a large numbler of studies about its outstanding physical and chemical properties such as a large specific surface area, excellent electrical conductivity, flexibility, mechanical properties and thermal stability. Owing to its unique structure, showing excellent cycle stability when as the lithium-ion battery anode, but its capacity is not very high, can not meet the demands of the products with high energy density. As a lithium-ion battery anode material, a transition metal oxide has become a well candidate and one of the potential electrode material, wherein the tungsten trioxide is the most stable at room temperature, without environmental pollution, low cost, high specific capacity. However, since the lithium ion insertion and deinsertion, can cause vlome expansion and contraction in the chanrge-discharge process, thereby resulting in destruction of the anode structure and enabling and solving the problem that energy density and cycle stability is poor.In view of the respective advantages of graphene and tungsten trioxide, we have investgated a large number of domestic and foreign literatures, and we will prepare the graphene and tungsten trioxide in this paper, and study the characters of structure and morphology, as well as its application in the lithium-ion batteries. These works mainly include the following areas:Firstly, in this study, we demonstrate a facile process to fabricate a layer-by-layer assembled 3D hierarchical sandwich-type architecture composed of 2D tungsten trioxide nanoplatelets and graphene(denoted as TTNPs-GS). When evaluated as anode materials, the sandwich-type architecture plays vital roles in endowing high electronic conductivity, accommodating large volume variation and achieving abundant ion transport paths, thus enabling superior lithium-ion storage performance. TTNPs-GS shows a good reversible capacity of 847 mAh/g(theoretical capacity of 693 mAh/g for tungsten trioxide), high-rate capability(292 mAh/g at 3600 mA/g) and long cycle life(615 m Ah/g with 118.9% capacity retention at 1080 mA/g after 1000 cycles).Secondly, We prepared the tungsten trioxide nanovolume with the radial length of 300 ~ 800 nm by wet chemical method, which was uniformly dispersed on the surface of the graphene by using polyvinylpyrrolidone as surfactant. Formed the nanocomposite material films that consists of graphene and tungsten trioxide nanovolume. Its morphology and structure were studied by using SEM and XRD, respectively. The results showed, its capacity can reach 550 mAh/g, at 100 mAh/g after 100 cycles and exhibited excellent cycle stability.