Prepation And Electrochemical Performance Of Metal Oxides On Flexible Materials

Lithium-ion batteries(LIBs)are kinds of green and pollution-free energy storage device.It is widely favored in the new energy field because of its high energy density,good safety performance,no memory effect and long cycle life.Studies have shown that metal oxides have higher theoretical specific capacity,but their volume changes greatly during the process of rapid charging and discharging,which causes electrode pulverization and affects the recycling performance of the batteries.At the same time,low electrical conductivity of metal oxide nanomaterials affecting the overall function of the batteries.This paper is devoted to the preparation of metal oxides on flexible materials.By organically combining flexible materials with metal oxides,metal oxide flexible electrodes that fully exhibit the advantages of metal oxides and flexible materials are prepared.Electrodes made of flexible materials as current collectors can not only withstand a certain degree of stretching,improve toughness,but also can be folded or crimped,and the research ideas of flexible electronic devices are widened.The main component of carbon cloth is carbon,which can be biodegradable in nature and is an environmentally friendly material.In the experiment:First,the electrode material was prepared on a flexible material by various methods and characterized by composition analysis and microscopic morphology analysis to determine the characteristics of the material;then,the prepared material was assembled into a lithium/sodium ion batteries to investigate its electrochemical performance;finally,study the problems existing in lithium/sodium ion batteries and improve them to prepare new anode materials with long life,high power and large capacity.In this paper,different synthetic methods were used to prepare high performance metal oxide/carbon cloth flexible electrode materials.The specific research contents are as follows:(1)The intrinsic poor electrical and large volume expansion upon cycling of ZnO raise up challenging kinetic issues.In this work,ZnO@TiO₂ core/shell nanorod arrays heterostructure grown directly on carbon cloth is designed and fabricated.The atomic layer deposition coated TiO₂ thin layer can not only function as an efficient stress buffer during electrochemical reaction,but also provide enhanced electronic conductivity by forming a heterostructure with ZnO.The ZnO@TiO₂ nanorod arrays on carbon cloth can simultaneously achieve the high capacity and high-rate long cycle life(1000m A h/g for250 cycles at 1 A/g),which is far superior to that of bare ZnO nanorod arrays on carbon cloth without TiO₂ shell.The density functional theory calculations reveal the strong chemical coupling between ZnO and TiO₂,which realizes band gap tailoring and significant charge redistribution of both ZnO and TiO₂.Such a unique structure endows the as prepared ZnO@TiO₂ on carbon cloth great potential as high performance three-dimensional flexible electrode in Li-ion batteries.(2)Prepared self-supported Co₃O₄ interlaced nanotube arrays directly on carbon cloth(CC)as an integrated binder-free flexible anode through facile hydrothermal and immersion process.This simple method preparation composite Co₃O₄ interlaced nanotube arrays directly on carbon cloth solved problems of the expansion volume and poor conductivity during charge/discharge.Compared with pure Co₃O₄,the Co₃O₄ interlaced nanotube arrays directly on carbon cloth possess excellent cyclability stability(1140 m A h/g for 350 cycles at 1 A/g),good rate performance(680 m A h/g at a high current density of 5 A/g)and exhibits high initial coulombic efficiency(about 85%).This method of combined the special structure of Co₃O₄ with flexible carbon cloth can be extended to other metal oxides,which has great potential as flexible lithium ion battery material.(3)Three-dimensional(3D)TiO₂ nanotubes(NTs)on carbon cloth(CC)(TiO₂NTs/CC)were synthesized by a method involving formation of a ZnO@TiO₂ nanorod(NRs)on CC(ZnO@TiO₂ NRs/CC)structure and a subsequent chemical etching process of ZnO NRs template.The 3D TiO₂ NTs/CC have been applied as flexible anodes for sodium ion batteries(SIBs).The TiO₂ NTs/CC yielded high specific capacity and good cycling stability,superior to that of some reported TiO₂ nanocomposites.The TiO₂ NTs/CC delivers a reversible capacity of 260 m A h g^-1 and 85.1%capacity retention over 150cycles at current density of 0.25 C(1 C=335 m A g^-1).It also exhibits high rate capacity of200 m A h g^-1 at 0.5 C.Even at a high rate of 1.0 C,the TiO₂ NTs/CC can still maintain a high capacity of 100 m A h g^-1.It was observed that the electrochemical performance of the TiO₂ NTs/CC was much better than that(150 m A h g^-1 for up to 150 cycles)of a solid TiO₂NRs/CC counterpart,which also demonstrated the capacity enhancement and good cycling stability.