Preparation And Battery Electrochemical Properties Of Macroporous C/SiO₂Composites

The thesis, which uses macroporous silica as carrier and utilizes the structure directing effectand capillary effect of macroporous silica, obtains the large-sized macroporous composite material.Through in situ hydrolysis and recrystallization at a high temperature of the large-sizedmacroporous composite material, we obtain two composite materials, i.e. C/SiO₂/SnO₂andC/SiO₂/Sb₂O₃, which are directly applied as a cathode of lithium ion battery to observe theelectrochemical behavior. The researches of this article are as follows:Firstly, on the basis of previous researchers’ work about this experiment, by using a novelsilica as carrier, PAN/SiO₂composites was made by immersing the support in the acrylonitrilesolution to undergo polymerization within the pore. After final calcination we can get maroporousconducting C/SiO₂composite. The carbon in the composites, which exists in form of three-layersandwich structure, was shaped as a continuous film covering the silica layer. The conductivity ofC/SiO₂was related to the concentration of acrylonitrile solution and the thickness of the carbonfilm. When the concentration of acrylonitrile was33wt%, the novel C/SiO₂composite exhibitedvolume resistance of17cm can be reduced after coating twice.Secondly, by using the macroporous conducting C/SiO₂composite as a substrate, through insitu hydrolysis and recrystallization at high temperature to obtain the composites of C/SiO₂/SnO₂,the characterization of all kinds of materials shows that the C/SiO₂/SnO₂composite material hasthree-dimensional large-sized diameter structure. SnO₂exists in the form of microcrystal inaperture and wall of hole, which is closely attached to electric conduntion and carbon membranes.After applying it to lithium batteries anode material directly and observing the electrochemicalbehavior, the capacity date shows C/SiO₂have good cycle stability. And it’s a suitable material foruse with high specific capacity anode material for composite. We find that C/SiO₂/SnO₂has highercharge-discharge capacity and good cycling performance, which is almost twice that of the former.Lastly, by using the C/SiO₂composite as a substrate, the composites of C/SiO₂/SnO₂areobtained through in situ hydrolysis and recrystallization at high temperature. Through thecharacterization of all kinds of material, it is found that recrystalization of Sb₂O₃was carried out athigh temperature to obtain the3D macroporous C/SiO₂/Sb₂O₃composites. The material has a largesized macroporous three-dimensional skeleton structure, crystal Sb₂O₃uniform load in the three-dimensional skeleton. And when applying it to lithium batteries anode material directly,C/SiO₂/Sb₂O₃shows higher charge-discharge capacity and good cycling performance for the jointeffort of the aperture three-dimensional skeleton of large sized of support and regulation, goodelectrical conductivity and recycling of carbon materials as well as crystal Sb₂O₃high-capacity.After20cycles, the capacity retains480mAh·g^-1, almost eights times of C/SiO₂.