Preparation Of Carbon-based Nanocomposite Anodes And Their Application In Lithium Batteries

In recent years,the promotion of electric vehicles and various consumer electronic products has made the new energy systems such as lithium batteries attracting topic.However,compared with fossil fuels,the mediocre energy density and cycle life of lithium batteries restrict the attainable driving mileage of electric automobiles and become the biggest concern for the public to buy new energy vehicles.Commercial lithium batteries are still struggling in the search for an ideal balance of energy density,cycle life,rate capability and battery safety.The graphite anode of the commercial lithium battery has the advantages of low cost,non-toxicity and harmlessness,but its low specific capacity has been difficult to meet the demand for high energy density batteries.In order to break through the energy density limitations of lithium batteries,researchers have used various methods to find the next generation of alternative anode materials.Among them,the use of carbon-based composites has been proved to be an effective strategy.At present,the mainstream form of lithium batteries is still lithium-ion battery.While as lithium metal batteries are the ultimate choice for lithium batteries,their research has also received wide attention.In this thesis,two types of carbon-based composites,of CoSe/Co particles coated with nitrogen-doped graphitic carbon nanosheets and carbon-silver hollow nanospheres,are applied to the anodes of lithium ion battery and lithium metal battery,respectively.It is expected that the reasonable designed structure can effectively enhance the electrochemical performance.The main contents of this thesis include:（1）With cobalt-based metal organic framework（ZIF-67）,selenium powder and dicyandiamide（DCDA）as precursors,the synthesis of CoSe and graphitic carbon coating were simultaneously achieved in one step high temperature process,forming a unique structure of CoSe/Co nanoparticles coated in nitrogen-doped graphitic carbon nanosheets.Thanks to the stable structure and the pseudo-capacitance effect,the material exhibits good electrochemical performance when used in lithium ion anodes.The specific capacity is about 630 mAh after 100 cycles at a current density of 0.2 A g^-1,and 640 mAh g^-1 after 500 cycles at a current density of 1 A g^-1.（2）The polymerization of 3-aminophenol and formaldehyde is carried out simultaneously with the silver mirror reaction to obtain silver-phenolic resin nanospheres,which are subsequently partially dissolved using acetone obtain silver-phenolic resin hollow nanospheres.Then,the products are carbonized at high temperature to obtain silver-carbon hollow nanospheres.The material was used as lithium metal anode matrix,and the influence of the carbon shell thickness on the coulombic efficiency during cycling was investigated.