Research On Nano-tungsten Oxide-based Materials As Anode Materials For Lithium-ion Batteries

The increasing consumption of world's energy has caused much environment and energy problems duo the rapid growth of population and diminishing fossil resource.Rechargeable lithium ion batteries?LIBs?,as a new tape of energy storage device,are crucial for portable electronic and electric vehicles in the future.LIBs also have attracted much attention due to their high-performance power source with high power and energy densities.Therefore,investigating nanostructured electrode materials with high energy densities is desirable for enhancing the electrochemical performance of lithium-ion batteries.Recently many efforts have concentrated on transition metal oxide materials as the anode materials for lithium-ion batteries due to their high theoretical capacity to replace the graphite anode(372mAhg^-1),such as WO₃,MnO₂,SnO₂,Co₃O₄,MoO₃,etc.However,they usually suffer from poor conductivity and structural instability.As is known,among these transition metal oxide,tungsten trioxide?WO₃?has been extensively investigated for its physiochemical properties and potential applications,such as gas senors,photocatalysis and supercapacitors,it also has been examined as an promising anode material for lithium ion batteries due to its high theoretical capacity(693mAhg^-1)and better electronic conductivity(10-10^-6Scm^-1)than some of other oxides.In this paper,we used some methods to synthesized some composites of tungsten trioxides with special structure and metal doping tungsten trioxides to enhance their electrochemical properties.The uniformly flower-like WO₃/CoWO₄/Co nanostructures were synthesized via a facile one-step hydrothermal reaction with solid heteropolyacid of W and Co as precursors and followed by heating process and calcination under the air condition.The as-prepared WO₃/CoWO₄/Co composite showed a high discharge capacity of1104mAhg^-11 after 40 cycles at 100 mAg^-1,and delivered excellent rate performance of1074,685,509,335mAhg^-11 at 200,400,800,1600 mAg^-1,respectively.The excellent electrochemical performance of WO₃/CoWO₄/Co nanostructures is attributed to the uniform dispersion of discrete nanoparticles,and it also can be highly optimized by the freestanding combination of Co-doped tungsten trioxide and cobalt tungstate,which helps to provide high specific capacity,high rate cycling and stable life performance.Double metal?chromium and silver?-doped hexagonal tungsten trioxide microspheres are synthesized via a facile hydrothermal method followed by calcination under air condition.The as-prepared?Cr,Ag?-WO₃ as anode materials delivers the high initial capacity of 1992.78 mAhg^-11 and retains a specific capacity of823.75mAhg^-11 after 50 cycles at current density of 100 mAg^-1,and shows the excellent rate performance of 1276.25,790.98,645.98,476.76 and 344.98mAg^-11 at the current density of 100,200,400,800 and 1600 mAg^-1,respectively.Synthetizing special morphology of h-WO₃ and doping chromium and silver into the crystal structure of h-WO₃ help to provide high rate capability and cycling stability.WO₃ nanorods/graphene nanocomposites?WO₃/RGO?were prepared by the solvothermal treatment of tungsten hexachloride and graphene in Diethylene glycol.The electrochemical performance of WO₃/RGO as anode materials for lithium-ion batteries was investigated by galvanostatic charge-discharge tests,cyclicvoltammetry?CV?,and electrochemical impedance spectroscopy?EIS?.The discharge capacity of the composite at the first cycle was 1181 mAhg^-1,and about 521 mAhg^-11 of reversible capacity remained after 100 cycle sat the current density of 100 mAg^-1.WO₃/RGO exhibited excellent cycling stability and rate performance,and has potential in advanced lithium-ion batteries.