Lithium Ion Batteries With Metal Oxide/Carbon Composite Anode Materials Research

In the last century,mankind has carried on the large-scale industrial production,which consumes a lot of resources on the earth.Nowadays,with the rapid development of industrial,construction and transportation,energy consumption rate is also improved.However,the amount of energy on earth is limited and non-renewable,oil and natural gas will be consumed in the near future.Energy is the human survival and development of the important material base,therefore,energy storage and the development of new energy become the important subject facing today's society.Energy storage has been used in every aspect of human life,and lithium ion batteries with high energy density,low self-discharge,cycle stability,long service life,the advantages of the use safety,acts as a main role in terms of energy storage.However,with the development of electronic devices and electric vehicle industry,already commercialized carbon negative electrode materials which have the low theoretical capacity?372 mAh g-1?,already cannot satisfy the requirement of people on the properties of lithium ion batteries.Metal oxide and sulfide have been increasingly appreciated by the people because of high specific capacity.In addition,metal oxide and sulfide is abundant in nature and low-cost ideal as anode materials for commercial production.But there are serious defects of metal oxide and sulfide,such as low electronic conductivity,low rate of lithium ion diffusion,serious volume effect,which restrict it cannot to commercial applications.Therefore,in order to develop a new type of metal oxides and sulfides electrode materials,must overcome these shortcomings and modify the material,so as to improve the conductivity of the material and ratio performance.Reasonable structural design and optimization will be carried on to combine metal oxide and sulfide with other material can make up for the disadvantage and improve electrochemical performance.In this paper,the main rersearch is that preparation of sandwich structured FeS₂-graphite composites and CoMoO₄ nanorods-graphene compositeHydrogen energy is considered to be a highly efficient and clean energy among many new energy which attract the attention of people.,The most promising way to prepare hydrogen energy is electrolyzed water,but the existing catalysts are mainly noble metal catalysts,which is very expensive and scarce,so it is difficult to carry out large-scale practical application.From the above,it is very necessary to develop a kind of high efficient catalyst without noble metal.MoS₂,as a kind of metal sulfide,exhibits excellent catalytic performance of hydrogen evolution,and it is rich in natural reserves and low price.The activity of hydrogen evolution is determined by the number of catalytic active sites,and MoS₂ active site only exists at the edge which can not meet the requirement of catalytic hydrogen evolution,so it is necessary to modify it.In this paper,we constructed nanosized materials with special structure as high-efficient catalysts for HER,with maximally exposed edges.1)we develop new FeS₂-graphite sandwich-like composite through a hydrothermal method using FeCl₃-GIC via high temperature burning process as precursor,which delivers good lithium storage properties.The fluffy graphite layer can enhance the mechanical strength and toughness,which could only counteract the volume variation to a certain degree,so as to ensure that the active substance will not fall off,improve the cycling stability and rate capability of the material.In addition,graphite can improve the conductivity of the composite electrode material,but also conducive to the rate of material performance.A reversible capacity of 427 mAh g-1 can be retained after 1000 cycles,showing the high capacity retention of 89%.2)CoMoO₄ nanorods-graphene sheet composites have been prepared via a simple hydrothermal method with 1D-2D heterogeneous feature.The excellent rate performance is due to the1 D feature of CoMoO₄ nanorods that can shorten lithiumtransport path and the 2D graphene sheets that can improvethe electrical conductivity,both of which can enhance the conversion reaction kinetics of anode materials.The charge–discharge test of CoMoO₄-based anode is performed at high current density of 5 A g-1 for the first time.Even at this high rate,the CoMoO₄-G electrode can still achieve high capacity of 615 mAh g-1.Noting that,the discharge capacities can keep over 610 mAh g-1 all throughout the 200 cycles,exhibiting remarkably excellent cycling stability.3)we control MoS₂ nanosheets vertically anchored on C₃N₄ substrate for fabrication of MoS₂-C₃N₄ hybrid catalyst via hydrothermal process,which assures maximally exposed edges of active MoS₂ materials.In addition,the tight binding of defects and lattice distortion can improve the efficiency of electron transfer,thus enhancing the catalytic activity.