The rechargeable lithium-ion batteries that started in the early 1990’s, are extensively used in lots of electronic devices, including cellular phones, laptop computers, camcorders, cameras and... Show moreThe rechargeable lithium-ion batteries that started in the early 1990’s, are extensively used in lots of electronic devices, including cellular phones, laptop computers, camcorders, cameras and medical devices. Due to high energy and power density of lithium-ion batteries, they are one of the most useful batteries, and lots of researches and developments are still progressing, especially in electronic vehicle / hybrid electric vehicle (EV/HEV). However, current lithium-ion batteries have many problems, especially those related to its electrolyte system. Because this component contains flammable organic solvents, they have several disadvantages, such as leakage, instability, and difficulty in manufacture of large flat types of batteries. To eliminate these problems, the studies on Solid Polymer Electrolyte (SPE) system are now an active research area. In this thesis work, three different approaches have been executed to improve electrolyte properties of lithium-ion batteries. As a based material tosylate poly(ethylene glycol) was prepared, and a plasticizer was synthesized and incorporated into a conventional poly(ethylene oxide)-based Solid Polymer Electrolyte systems. First, to increase amorphousness in plasticizer, bisphenol-A was introduced, which has free rotating unit and only ionic conductivity was measured to verify. Secondly, hyperbranched poly(p-hydroxy styrene) derivatives were synthesized and used as the base matrix in SPEs. Polymers which have higher order of branching exhibited higher ionic conductivity, and it was assumed that branching structure lowered crystallinity. Finally, we synthesized 3-chloropropanesulfonyl-trifluoromethanesulfonylimide (LiCPSI) and attached to hyperbranched poly(p-hydroxy styrene) to verify that how hyperbranched structure would affect the ionic conductivity. Major characterization techniques include ionic conductivity, cyclic voltammetry (CV) and thermogravimetric analysis (TGA). Show less
