Preparation And Performance Of Nano-composite Polymer Electrolytes

The polymer lithium-ion batteries are considered as one of the best candidates for next generation power sources due to their high energy density, safety and reliability and environmental protection. However, there are still some practical problems of battery cycle performance and safety issue to be solved, for example, thermal stability and low ionic conductivity at room temperature.Therefore, the PEO-based composite polymer electrolytes have been researched and improved mainly by the following two methods:1. Research showed that the room temperature conductivity of polymer electrolyte system could be significantly improved when plasticizer was added into PEO16/LiC104 system, but some new problems have been found, such as poor interface stability, and bad mechanical properties. The main effects of plasticizer on polymer electrolytes as follows:(1) Reduce the glass transition temperature of polymer electrolyte temperature, increase the mobility of polymer chain segments which will improve the transport of charge carrier; (2) The polar of polymer matrix has been improved by the interaction of polymer molecules and dipole and then promoting the dissociation of lithium salt in polymer electrolyte. Meanwhile, the coordination bond between polymer and lithium-ion has been broken which caused that more lithium-ion can move in the amorphous rather than crystalline phase.2. Investigation indicated that the ionic conductivity, thermal stability and other properties could be greatly improved when nano-particles were added into PEO16/LiC104.The addition of nano-particles in polymer electrolytes could decrease the crosslink between polymer chains and lithium ions, result in increasing the ionic conductivity, meanwhile, the glass transition temperature (Tg), melting temperature (Tm) and crystallinity (Xc) was decreased.In this paper, polymer electrolytes have been prepared by solution casting method using different types, size and surface properties of nano-particles and plasticizer. The polymer electrolytes were characterized by DSC, TGA and EIS methods. The electrochemical properties and thermal properties of PEs were systematic studied. Main works are as follows:1) The effects of proportion and size of nano-particles on polymer electrolytes were studied.2) The effects of surface structure of nano-particles on polymer electrolytes were studied.