Preparation And Lithium Storage Performance Of Silicon-conducting Polymer Composites

With the rapid development of new industrial technology, such as renewable energy storage and Electric Vehicle applications, there are growing demands for the lithium ion batteries with high energy density as well as high power performance. Traditional anode materials, such as graphite whose theoretical specific capacity is limited to 372mAh/g could not meet the demand of lithium-ion batteries. Exploring high-capacity anode material has been one of the targets for lithium ion batteries and silicon is one of the hot topics as anode candidate due to the high theoretical capacity of 4200mAh/g. However, the low conductivity, huge volume expansion and poor cycling performance of silicon severely restrict its commercial application. The conductive copolymer matrix can provide fast electronic transfer channels and buffer the great volume changes of Si during the cycling process. The thesis as-prepared Si-(conductive polymer) composite electrodes successfully achieve higher capacity and better cycling performance than the bare nano-Si anode.1. A new polythiophene-coated silicon composite anode material was prepared by in-situ oxidative polymerization reaction at room temperature with chloroform as solvent. The structure of this material was characterized by infrared spectroscopy,which proved that the oxidative polymerization of thiophene occurs mainly in αposition, with the α-α type polythiophene as the primary product. Through explorations of experiments, it is observed when silicon and thiophene feed ratio is7:3, and the molar ratio of catalyst to thiophene is 4:1, the composite materials obtained by evocative polymerized for 10 h have excellent electrochemical cycling performance. These composites can still reserve 479 mAh/g specific capacity after 50charge-discharge cycles.2. Using aniline, pyrrole and nano silicon as the raw materials, a novel Si/poly(aniline-co-pyrrole)(Si/PANI-PPy) composite anode material was prepared by in-situ chemical oxidation polymerization method. Fourier transform infrared spectroscopy and X-ray diffraction were used to character the structure of samples in this study. The effects of preparation conditions(mass ratio of silicon/aniline-co-pyrrole, different pH value and times) on the electrochemicalperformance of composite anode materials were studied. The results show that mass ratio of silicon/aniline-co-pyrrole have great influence on the electrochemical performance of the Si-poly(aniline-co-pyrrole) materials. When the mass ratio of Silicon and aniline, pyrrole is 1:1, the specific capacity of the composite electrode retains 637 m Ah/g after 50 cycles.