Browsing by Author "Hsieh, Han-Wei"

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Real-time investigation of the structural evolution of electrodes in a commercial lithium-ion battery containing a V-added LiFePO4 cathode using in-situ neutron powder diffraction
(2013-12-15)
Hu, Chih-Wei
;
Sharma, Neeraj
;
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Peterson, Vanessa K.
In-situ neutron powder diffraction was employed to investigate the structural evolution of the electrode materials in a commercial lithium-ion battery used for electric buses in Taiwan. The battery, containing a vanadium-added LiFePO4 cathode, does not exhibit a delayed phase transition between LiFePO4 (triphylite) and FePO4 (heterosite) suggesting that the delayed phase transition can be suppressed through the use of vanadium-added LiFePO4 cathodes, which also enhances the capacity and prolongs the cycle life of these batteries. Furthermore, we characterize the readily reversible structural change of the anode (LixC6 where 0 < x <= 1) and correlate this to battery voltage. (C) 2013 Elsevier B.V. All rights reserved.
Recent advances in liquid-crystal THz filters
(2018-01-01)
Huang, Chia-Yi
;
Chen, Wei-Yuan
;
Chiu, Jing-Ya
;
Chang, Hsiao-Shan
;
Liu, Jia-Kai
Liquid crystal polymer (LCP) films are rolled into hollow cylinders. The hollow cylinders are measured by a terahertz spectrometer. Experimental results reveal that the transmittance spectra of the hollow cylinders have peaks at specific frequencies due to Fabry-Perot resonance, and the frequencies of the peaks can be tuned by changing the thicknesses and rolled layers of the LCP films. Therefore, the rolled LCP films can be used to develop terahertz filters.
Vanadium Substitution of LiFePO4 Cathode Materials To Enhance the Capacity of LiFePO4-Based Lithium-Ion Batteries
(2012-11-22)
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Wu, Pin-Jiun
;
Liu, Heng-Jui
;
Hu, Chih-Wei
The mechanism of enhancing the capacity of the LiFePO4 cathodes in lithium ion batteries by the addition of a small amount of vanadium, which locate on the lithium site and induce lithium vacancies in the crystal structure, is reported in this article. As a result, the capacity increases from 138 mAh/g found for pristine LiFePO4 to 155 mAh/g for the V-added compound, and the conductivity increases from 4.75 x 10(-4) S/cm for the LiFePO4 without V addition to 1.9 x 10(-2) S/cm for the V-added compound. A possible model to facilitate the enhancement of conductivity and capacity is described with evidence supported by X-ray powder diffraction, X-ray absorption spectroscopy, and neutron powder diffraction data.