THESIS
2014
xiii, 80 pages : illustrations (some color) ; 30 cm
Abstract
High-performance solid-state polymer electrolytes are considered as a promising
alternative for liquid electrolytes widely used in electrochemical-based energy storage devices
such as rechargeable batteries, fuel cells and supercapacitors, etc. Because of their solid nature,
polymer electrolytes offer many advantages compared with conventional liquid ones such as
no leakage, high reliability, light weight, high breakdown voltage, and ease of processing.
However, most solid polymer electrolytes have low room temperature ion conductivity which
is insufficient for practical applications. Although polymer gel electrolytes show good ion
conductivity, they show poor mechanical stability. To overcome these issues, novel solid-state
polymer electrolytes possessing both high ion conducti...[
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High-performance solid-state polymer electrolytes are considered as a promising
alternative for liquid electrolytes widely used in electrochemical-based energy storage devices
such as rechargeable batteries, fuel cells and supercapacitors, etc. Because of their solid nature,
polymer electrolytes offer many advantages compared with conventional liquid ones such as
no leakage, high reliability, light weight, high breakdown voltage, and ease of processing.
However, most solid polymer electrolytes have low room temperature ion conductivity which
is insufficient for practical applications. Although polymer gel electrolytes show good ion
conductivity, they show poor mechanical stability. To overcome these issues, novel solid-state
polymer electrolytes possessing both high ion conductivity and good mechanical strength are
needed.
In the present research, composite polymer electrolyte membranes based on polyvinylidene
fluoride-co-hexafluoropropylene-lithium bis (oxalate) borate (LiBOB) via the solution casting
methods have been prepared and characterized. The effect of salt concentration and inorganic
filler concentration on electrochemical and physical properties are studied. An optimized ionic
conductivity of 6×10
-5 Scm
-1 for solid PVDF-HFP/LiBOB (1:1 wt. %) has been achieved and
an ionic conductivity up to 1.1 × 10
-4 Scm
-1 has been attained in PVDF-HFP/LiBOB/SiO
2 (6
wt.%) at room temperature, which is almost one order of magnitude higher than those of
conventional solid polymer electrolyte. The improvement is mainly attributed to a much
improved ion mobility. It is found the large anion BOB- having a weak interaction with Li
+ can help the Li salt dissolution in PVDF-HFP while SiO
2 can suppress crystallinity and increase
amorphous phase, leading to a significantly enhanced ion conductivity. A variety of techniques
such as Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR)
spectroscopy, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron
Micrographs (SEM) are performed to elucidate the relationship between the structural and
dynamic properties of the hybrid electrolyte and the ion mobility.
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