Browsing by Author "Phuoc-Anh Le"

Now showing 1 - 4 of 4

A new redox phloroglucinol additive incorporated gel polymer electrolyte for flexible symmetrical solid-state supercapacitors
(2019-06-01)
Phuoc-Anh Le
;
Van-Truong Nguyen
;
Yen, Po-Jen
;
Tseng, Tseung-Yuen
;
Wei, Kung-Hwa
We reported a new and environmentally friendly phloroglucinol additive incorporated polyvinyl alcohol-LiClO4 gel polymer electrolyte for flexible symmetrical solid-state supercapacitors. The incorporation of 10 wt% phloroglucinol into PVA-LiClO4 gel polymer electrolytes results in much higher specific capacitance (114 F g(-1)) than that without phloroglucinol (60 F g(-1)), an increase of 90%, because of the redox reaction of phloroglucinol in the system. We used the PVA-LiClO4 with 10 wt% phloroglucinol as a gel polymer electrolyte in combination with nitrogen-doped graphene nanosheet-based electrodes as the anode and cathode to fabricate a symmetrical solid-state supercapacitor. The fabricated supercapacitor involving the phloroglucinol redox additive has an energy density of 2.3 W h kg(-1) at a power density of 150 W kg(-1), which is higher than the one without a redox additive (1.9 W h kg(-1) at a power density of 150 W kg(-1)). Moreover, the supercapacitor involving the redox additive has good stability; its capacitance remains at up to similar to 94% after 5000 charge/discharge cycles.
Cathodic plasma-induced syntheses of graphene nanosheet/MnO2/WO3 architectures and their use in supercapacitors
(2020-05-10)
Huang, Shih-Yu
;
Phuoc-Anh Le
;
Yen, Po-Jen
;
Lu, Yi-Chun
;
Sahoo, Sumanta Kumar
In this study, we synthesized new 0.01-2 mu m graphene nanosheet/MnO2WO3(G/MnO2/WO3) architectures through an electrochemically induced cathodic plasma process in a single batch at a lower temperature (70 degrees C) and for a shorter time (2 h) than those required for the syntheses of similar structures when using a hydrothermal method. We first obtained 0.01-1 mu m leaf-like graphene (G) nanosheets, then 0.1-0.3 mu m long and approximately 10 nm diameter petiole-like MnO2 nanowires on the G nanosheets, and finally 0.20-2.0 mu m petal-like WO3 on MnO2/G - thereby forming the G/MnO2/WO3 architectures - as evidenced using scanning electron microscopy and transmission electron microscopy. We deciphered the step-wise reaction mechanism behind the formation of the G/MnO2/WO3 architectures during the plasma process. The high surface area of 291 m(2) g(-1) in the G/MnO2/WO3 architecture was contributed mainly by the G nanosheets, providing a suitable surface area for diffusion of the charge carriers during the charging and discharging process. As a result, an electrode incorporating the G/MnO2/WO3 architectures exhibited an excellent specific capacitance of 620 F g(-1) - 45 and 200% higher than those of G/MnO2 (421 F g(-1)) and G (189 F g(-1)) electrodes, respectively - at a current density of 0.5 A g(-1). Moreover, the G/MnO2/WO3-incorporated electrode exhibited good electrochemical cycling stability, with 90% capacitance retention over 5000 cycles at 1 A g(-1). Such new G/MnO2/WO3 heterojunction structures, not only provide high-performance electrode applications, but also suggest a potential approach toward fabricating other heterojunction structures having high surface areas for energy storage applications. (C) 2020 Elsevier Ltd. All rights reserved.
Role of precursors mixing sequence on the properties of CoMn2O4 cathode materials and their application in pseudocapacitor
(2019-11-14)
Pattanayak, Bhaskar
;
Simanjuntak, Firman Mangasa
;
Panda, Debashis
;
Yang, Chih-Chieh
;
Kumar, Amit
In this study, the effect of oxygen vacancy in the CoMn2O4 on pseudocapacitive characteristics was examined, and two tetragonal CoMn2O4 spinel compounds with different oxygen vacancy concentrations and morphologies were synthesized by controlling the mixing sequence of the Co and Mn precursors. The mixing sequence was changed; thus, morphologies were changed from spherical nanoparticles to nanoflakes and oxygen vacancies were increased. Electrochemical studies have revealed that tetragonal CoMn2O4 spinels with a higher number of oxygen vacancies exhibit a higher specific capacitance of 1709 F g(-1) than those with a lower number of oxygen vacancies, which have a higher specific capacitance of 990 F g(-1). Oxygen vacancies create an active site for oxygen ion intercalation. Therefore, oxidation-reduction reactions occur because of the diffusion of oxygen ions at octahedral/tetrahedral crystal edges. The solid-state asymmetric pseudocapacitor exhibits a maximum energy density of 32 Wh.kg(-1) and an excellent cyclic stability of nearly 100%.
Transparent Flexible Heteroepitaxy of NiO Coated AZO Nanorods Arrays on Muscovites for Enhanced Energy Storage Application
(1970-01-01)
Van-Qui Le
;
Phuoc-Anh Le
;
Wu, Shu-Chi
;
Lai, Yu-Hong
;
Lin, Yan-Gu
Transparent flexible energy storage devices are considered as important chains in the next-generation, which are able to store and supply energy for electronic devices. Here, aluminum-doped zinc oxide (AZO) nanorods (NRs) and nickel oxide (NiO)-coated AZO NRs on muscovites are fabricated by a radio frequency (RF) magnetron sputtering deposition method. Interestingly, AZO NRs and AZO/NiO NRs are excellent electrodes for energy storage application with high optical transparency, high conductivity, large surface area, stability under compressive and tensile strain down to a bending radius of 5 mm with 1000 bending cycles. The obtained symmetric solid-state supercapacitors based on these electrodes exhibit good performance with a large areal specific capacitance of 3.4 mF cm(-2), long cycle life 1000 times, robust mechanical properties, and high chemical stability. Furthermore, an AZO/NiO//Zn battery based on these electrodes is demonstrated, yielding a discharge capacity of 195 mAh g(-1) at a current rate of 8 A g(-1) and a discharge capacity of over 1000 cycles with coulombic efficiency to 92%. These results deliver a concept of opening a new opportunity for future applications in transparent flexible energy storage.