2 research outputs found
Composite Gel Polymer Electrolyte for Improved Cyclability in Lithium–Oxygen Batteries
Gel
polymer electrolytes (GPE) and composite GPE (cGPE) using one-dimensional
glass microfillers have been developed for their use in lithium–oxygen
batteries. Using glass microfillers, tetraglyme solvent, UV-curable
polymer, and lithium salt at various concentrations, the preparation
of cGPE yielded free-standing films. These cGPEs, with 1 wt % of microfillers,
demonstrated increased ionic conductivity and lithium transference
number over GPEs at various concentrations of lithium salt. Improvements
as high as 50% and 28% in lithium transference number were observed
for 0.1 and 1.0 mol kg<sup>–1</sup> salt concentrations, respectively.
Lithium–oxygen batteries containing cGPE similarly showed superior
charge/discharge cycling for 500 mAh g<sup>–1</sup> cycle capacity
with as high as 86% and 400% increase in cycles for cGPE with 1.0
and 0.1 mol kg<sup>–1</sup> over GPE. Results using electrochemical
impedance spectroscopy, Raman spectroscopy, and scanning electron
microscopy revealed that the source of the improvement was the reduction
of the rate of lithium carbonates formation on the surface of the
cathode. This reduction in formation rate afforded by cGPE-containing
batteries was possible due to the reduction of the rate of electrolyte
decomposition. The increase in solvated to paired Li<sup>+</sup> ratio
at the cathode, afforded by increased lithium transference number,
helped reduce the probability of superoxide radicals reacting with
the tetraglyme solvent. This stabilization during cycling helped prolong
the cycling life of the batteries
Tunable Size and Spectral Properties of Fluorescent NanoGUMBOS in Modified Sodium Deoxycholate Hydrogels
Microstructures of sodium deoxycholate hydrogels were altered considerably in the presence of variable tris(hydroxymethyl)aminomethane (TRIS) concentrations. These observations were confirmed by use of X-ray diffraction, polarized optical microscopy, rheology, and differential scanning calorimetry measurements. Our studies reveal enhanced gel crystallinity and rigidity with increasing TRIS concentrations. The tunable hydrogel microstructures obtained under various conditions have been successfully utilized as templates to synthesize cyanine-based fluorescent nanoGUMBOS (nanoparticles from a group of uniform materials based on organic salts). A systematic variation in size (70–200 nm), with relatively low polydispersity and tunable spectral properties of [HMT][AOT] nanoGUMBOS, was achieved by use of these modified hydrogels. The gel microstructures are observed to direct the size as well as molecular self-assembly of the nanomaterials, thereby tuning their spectral properties. These modified hydrogels were also found to possess other interesting properties such as variable morphologies ranging from fibrous to spherulitic, variable degrees of crystallinity, rigidity, optical activity, and release profiles which can be exploited for a multitude of applications. Hence, this study demonstrates a novel method for modification of sodium deoxycholate hydrogels, their applications as templates for nanomaterials synthesis, as well as their potential applications in biotechnology and drug delivery