225 research outputs found

    Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

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    Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10−3 S cm−1. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providing flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g−1 for standard metallic current collectors and (ii) 99.5 mAh g−1 for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed

    SYNTHESIS AND FUNCTIONALIZATION OF CIGS NANOPARTICLES FOR LBL DEPOSITION

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    poster abstractCopper Indium Gallium Diselenide (CIGS) solar cells have been used widely in thin film solar cells due to their high attainable efficien-cy and tunable band gap. The cost of solar cell manufacturing needs to be further reduced to make CIGS solar cells economically viable. The main objective of this research is to repeatedly and accurately synthe-size CIGS nanoparticles in a desired ratio to allow for an efficient band gap and dispersion in an aqueous solution for Layer-by-Layer (LbL) nanoassembly. CIGS nanoparticles have been synthesized by arrested precipitation in Oleylamine solution. The particles were purified utiliz-ing chloroform, ethanol, and water via centrifugation. The purified na-noparticles were down to a size of 15 nm with average size of 60 nm. A ligand exchange was performed to remove the capping agent, Oleylamine, and replace it with 11-mercaptoundecanoic acid, a thiol ligand. The thiol ligand used had charged functional groups resulting in the functionalized particles with expected high negative zeta potential for stable dispersion. Lastly, the nanoparticles were analyzed through the utilization of X-ray diffractive spectroscopy (XRD), transmittance spectroscopy, energy-dispersive x-ray spectroscopy (EDS) and a scan-ning electron microscope (SEM). Using the oppositely charged disper-sion in aqueous solutions, multiple size-controlled layers of CIGS can be obtained using Layer-by-Layer nanoassembly, creating a solar cell. The synthesis, characterization and functionalization results will be presented in the poster

    Layer-By-Layer Self-Assembly of CIGS Nanoparticles and Polymers for All-Solution Processable Low-Cost, High-Efficiency Solar Cells

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    poster abstractThin film solar cells made from copper indium gallium selenide (CIGS) materials have shown great potentials of providing low cost, high efficiency panels viable for wide spread commercial usage. Layer-by-layer (LbL) self-assembly is a low-cost, versatile nanofilm deposition process, however introduces polymers in the nanoparticles films, which reduces charge transport thereby affecting solar cell efficiency. This research aims to study various polymer materials to replace currently used insulating polymers in LbL, such as poly(sodium-4-styrenesulfonate) (PSS) and polyethyenimine (PEI). This poster will present processes and results of CIGS nanoparticles synthesis using controlled heating of CuCl, InCl3, GaCl3, and Se in oleyamine; functionalization of the particles to disperse in organic and aqueous-based solvents for LbL; and initial outcomes of CIGS, polymers LbL film fabrication and characterization. The size distribution of synthesized nanoparticles cleaned through alternate suspension and precipitation in chloroform and ethanol shows a peak at 72 nm. Particles light absorption properties measured with ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy shows good spectrum coverage with band edge near 1100 nm. The X-ray diffraction (XRD) results of the particles confirms the composition and tetragonal chalcopyrite crystal structure of CIGS materials. Chemical-bath-deposition of cadmium sulfide (CdS) and spray-coating of zinc oxide (ZnO) films are used along with LbL absorbing film in realization of a solar cell device. The fabricated devices are tested using semiconductor characterization instrument

    Convergence rate across the Nepal Himalaya and interseismic coupling on the Main Himalayan Thrust: Implications for seismic hazard

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    We document geodetic strain across the Nepal Himalaya using GPS times series from 30 stations in Nepal and southern Tibet, in addition to previously published campaign GPS points and leveling data and determine the pattern of interseismic coupling on the Main Himalayan Thrust fault (MHT). The noise on the daily GPS positions is modeled as a combination of white and colored noise, in order to infer secular velocities at the stations with consistent uncertainties. We then locate the pole of rotation of the Indian plate in the ITRF 2005 reference frame at longitude = − 1.34° ± 3.31°, latitude = 51.4° ± 0.3° with an angular velocity of Ω = 0.5029 ± 0.0072°/Myr. The pattern of coupling on the MHT is computed on a fault dipping 10° to the north and whose strike roughly follows the arcuate shape of the Himalaya. The model indicates that the MHT is locked from the surface to a distance of approximately 100 km down dip, corresponding to a depth of 15 to 20 km. In map view, the transition zone between the locked portion of the MHT and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the Himalaya. According to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data, this transition seems to happen in a zone where the temperature reaches 350°C. The convergence between India and South Tibet proceeds at a rate of 17.8 ± 0.5 mm/yr in central and eastern Nepal and 20.5 ± 1 mm/yr in western Nepal. The moment deficit due to locking of the MHT in the interseismic period accrues at a rate of 6.6 ± 0.4 × 10^(19) Nm/yr on the MHT underneath Nepal. For comparison, the moment released by the seismicity over the past 500 years, including 14 M_W ≥ 7 earthquakes with moment magnitudes up to 8.5, amounts to only 0.9 × 10^(19) Nm/yr, indicating a large deficit of seismic slip over that period or very infrequent large slow slip events. No large slow slip event has been observed however over the 20 years covered by geodetic measurements in the Nepal Himalaya. We discuss the magnitude and return period of M > 8 earthquakes required to balance the long term slip budget on the MHT
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