Controlled Preparation Of Cu_xO Thin Films And Studies On Their Physical/Electrochemical Properties

With the limitation of fossil fuels and increasingly prominent environmental problems,new energy sources have received more and more attention due to their environmental protection and renewable characteristics.Lithium-ion batteries are considered to be the most promising energy storage device because of their high energy/power density and cycle stability.In recent years,the development of new energy vehicles has made lithium-ion batteries attract attention and become the preferred energy storage device for new energy vehicles.The key to the research of lithium-ion batteries is the electrode materials.The traditional graphite anodes can not meet the increasing energy density requirements.Therefore,searching for anode materials with higher energy density has become a research hotspot.Cu_xO oxides have become the focus of research because of their high theoretical capacity,environmental friendliness,and low cost.This type of material exhibits superior performance as a negative electrode material for lithium-ion batteries.But it has also some disadvantages,such as the poor conductivity and the serious volume expansion/contraction during the process of deintercalation,causing the structure to collapse,which seriously degrades the electrochemical cycle stability of the battery.The ways to solve these problems mainly include:compounding with carbon-based materials,nanomaterialization of materials and thinning of materials,etc.Nanostructures can alleviate stress changes caused by volume expansion during charge and discharge,and can effectively shorten the diffusion path of lithium ions improving the electrochemical performance of the material.The thin film electrode has good mechanical strength and large specific surface area,which can increase the contact area between the electrode material and the electrolyte,as well as shorten the diffusion distance of the lithium-ions.The shorter the diffusion distance of the ions is,the smaller electrical resistance of the electrode material is.Therefore,in this article the electrochemical performance of Cu_xO will be studied by using nanostructure thin film electrode.The main contents are as follows:1)Cu_xO films with different Cu oxidized valence states were prepared by magnetron sputtering.Experiment results indicate that different phases of copper?CuO,Cu₂O and Cu₄O₃?can be obtained by adjusting the pressure and flow ratio of oxygen to argon during the deposition.On this basis,we constructed the processing phase diagram of Cu_xO,and further conducted the crystal structure,surface morphology,optical band gap and electronic transportation properties characterization on three kinds of Cu_xO.Moreover,a new method based on KPFM for distinguish the oxide state of Cu in Cu_xO was proposed.2)The Cu_xO films with nano-array structure were obtained by the method of“grazing incidence”deposition.The electrochemical properties of different phases were analyzed and compared.The cycle performance tests showed that the efficiency and cycle stability of CuO phase were better than those of the other two phases.3)We chose CuO as the negative electrode,matching the positive electrode of lithium cobalt oxides,and aluminum plastic film to design a pouched full battery.The CuO thin film anode can maintain good cycle performance in this pouched battery.