Preparation And Electrochemical Properties Of Ozonation Ultrafine Layered Graphite Electrode

With the rapid development of the economy,the number of use of energy is also increasing.In recent years,China has more and more imports of coal,oil and other traditional energy.The large use of these energy has also seriously damaged the ecological environment.In order to solve this problem,the development of new energy,improving energy efficiency and reducing pollution in the process of energy use have become a hot spot in the field of environmental and energy research.In the field of new energy,lithium ion battery has the characteristics of high specific energy,large capacity,good circulation,long service life,light weight,small volume,environmental protection and no pollution.It is the representative of modern high-performance battery.The battery electrode is the key factor that affects the performance of the battery.Therefore,the preparation of high-performance electrode materials,further improving the practical efficiency of lithium ion battery and reducing the consumption of energy has become the focus of current research.The composition,principle and advantages of lithium ion battery are introduced in this paper.The development status and problems of lithium ion batteries are summarized.The research status and modification methods of natural graphite materials are described in detail,and their advantages and disadvantages are analyzed.On this basis,natural layered graphite is modified by means of reducing the size of graphite and the chemical method of graphite surface oxidation,so as to improve specific capacity,rate and cycle performance of graphite.A series of analysis of its physical and electrochemical properties was carried out.(1)The 20?m commercial natural graphite was cut through the jet impactor to get 2 ?m layered graphite.After the graphite particles crushed,it keeps the original graphite crystal structure and agglomerate formation of 3D clusters structure,the graphite layer spacing increases,graphite edge defects increase damage stripping the formation of gaps.The surface area of graphite is increased by 226.5% and the density of vibratory solid is increased by 19.1%.The electrochemical performance of graphite after the particle size reduction is obviously improved,the first discharge specific capacity reaches 544mAh/g,compared with the increase of 100mAh/g of the large particle graphite.Under the charge and discharge conditions of 0.3C,0.5C and 1C,the multiplying performance increased 30mAh/g,38mAh/g and 60mAh/g respectively.However,the ultrafine layered graphite was prepared into a commercial battery,and the cycle stability decreased after 800 cycles under the charge and discharge current of 3C and 5C.It is considered that excessive surface defects and agglomeration degree lead to the unstable surface activity of graphite,thus unable to generate stable and dense SEI film,resulting in the exfoliation and excessive expansion of graphite.(2)The graphite of 2 ?m is treated by ozone aeration oxidation.The degree of graphite agglomeration is weakened,the edge structure of graphite particles is not changed,and the defect structure still exists.The electrochemical performance of graphite after surface modification is improved,and the first discharge capacity of graphite has not changed obviously,and the first charge and discharge efficiency is increased.Under the current intensity of 1C and 3C,the specific capacity increased by 20% and 15% compared with that of the pristine graphite.Under the condition of charge and discharge of 3C and 5C,the capacity retention rate increased by about 30% after 800 cycles of charge and discharge.The analysis shows that ozone surface oxidation does not destroy graphite structure,but even oxygen functional groups on the surface of graphite can help reduce the surface activity of graphite and form stable SEI film.The same oxidation method was used for 20 ?m graphite.The results showed that the electrochemical performance of graphite decreased significantly.It is considered that the oxidation of the large particles of graphite by the ozone aeration oxidation method is not uniform,resulting in the instability of the graphite surface and the inhibition of the electrochemical performance.