| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 93 === These years, many research groups have pointed out that a solid polymer electrolyte (SPE) doped with ceramic nano-particles could provide a new Li-ion transport pathway and improve its conductivity. However, the role of the added ceramic nano-particles on Li-ion transport in the modified SPE is still unclear. In this research, the synthesized TiO2 nanoparticles were used to modify the SPE (composite polymer electrolyte, CPE). The role of the TiO2 on Li-ion transport in the CPE was investigated by systematically designing a series of experiments.
It was found that the nano-sized TiO2 synthesized by the Ti(OC2H5)4 possesses pure Anatase crystalline phase and its particle size is around 5 nm. By the introduction of the nano-sized TiO2 into SPE, its crystalline domain is destroyed, and its glass transition temperature (Tg) declines with an increase the content of TiO2, indicating that the mobility of polymer chain is improved. It was also observed that the TiO2 nanoparticles were dispersed very well in the matrix of the composite polymer electrolyte. Increasing the content of the Li salt leads to an increase in the amount of ion pairs in the SPE. As a result, the TiO2 could not be incorporated well into the composite polymer electrolyte with 20% of Li salt. In the CPE system, the interaction between TiO2 and ClO4- was evidenced by virtue of FTIR/ATR. There are three Li-ion environments involving ion pair(Li+-ClO4-), coordination between Li ion and oxygen atom with higher electro-negativity in the polymer chain and coordination between Li ion and oxygen atom on the surface of TiO2in the CPE. By analyzing the Li ion environments at various temperatures, it is observed that the introduction of the nano-sized TiO2 indeed declines the number of ion pairs and the coordination between Li ion and oxygen atom on the surface of TiO2 is dominant in the Li environment at the lower temperature.
The role of TiO2 on Li ion transport in the CPE was successfully explored by virtue of FTIR/ATR, XRD, DSC, TEM, XAS and solid state NMR. The transport mechanism of lithium ion in the CPE is also proposed.
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