Browsing by Author "Pattanayak, Bhaskar"

Now showing 1 - 4 of 4

Flexible solid-like electrolytes with ultrahigh conductivity and their applications in all-solid-state supercapacitors
(2018-01-01)
Yang, Chih-Chieh
;
Lin, Hao-Yang
;
Kumar, Amit
;
Pattanayak, Bhaskar
;
Tsai, Hung-Yi
All-solid-state supercapacitors (ASSS) with solid-state electrolytes (SSEs) can be used to overcome the liquid leakage problem in devices. However, ionic conduction in solid electrolytes is one of the barriers to further improvements in ASSS. This paper describes the fabrication of a flexible SSE composed of poly(vinylidene fluoride-co-hexafluoropropylene), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and ethylene carbonate, which demonstrates an ultrahigh conductivity of 8.52 mS cm(-1) and a wide 5 V operation voltage window of -2 to +3 V. Electrodes composed of active carbon, multiwall carbon nanotubes, and polyvinylidene fluoride were used as both anode and cathode to assemble a symmetrical supercapacitor. The resultant supercapacitor exhibits a maximum power density of 3747 W kg(-1) at an energy density of 7.71 W h kg(-1) and a maximum energy density 17.1 W h kg(-1) at a power density of 630 W kg(-1). It displays excellent cycling stability with 91.3% of the initial specific capacitance after 3000 charging/discharging cycles. This flexible SSE in this study demonstrates a high potential for use in energy storage, conversion, and wearable device applications.
Peroxide induced volatile and non-volatile switching behavior in ZnO-based electrochemical metallization memory cell
(2017-09-20)
Simanjuntak, Firman Mangasa
;
Chandrasekaran, Sridhar
;
Pattanayak, Bhaskar
;
Lin, Chun-Chieh
;
Tseng, Tseung-Yuen
We explore the use of cubic-zinc peroxide (ZnO2) as a switching material for electrochemical metallization memory (ECM) cell. The ZnO2 was synthesized with a simple peroxide surface treatment. Devices made without surface treatment exhibits a high leakage current due to the self-doped nature of the hexagonal-ZnO material. Thus, its switching behavior can only be observed when a very high current compliance is employed. The synthetic ZnO2 layer provides a sufficient resistivity to the Cu/ZnO2/ZnO/ITO devices. The high resistivity of ZnO2 encourages the formation of a conducting bridge to activate the switching behavior at a lower operation current. Volatile and non-volatile switching behaviors with sufficient endurance and an adequate memory window are observed in the surface-treated devices. The room temperature retention of more than 10(4) s confirms the non-volatility behavior of the devices. In addition, our proposed device structure is able to work at a lower operation current among other reported ZnO-based ECM cells.
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%.
Templating synthesis of nickel cobaltite nanoflakes and their nanocomposites for making high-performance symmetric supercapacitors
(2019-12-01)
Yang, Chih-Chieh
;
Sun, Wen-Chien
;
Kumar, Amit
;
Pattanayak, Bhaskar
;
Tseng, Tseung-Yuen
Nickel cobaltite is one of the most popular pseudocapacitance materials for creating high-performance energy-storage devices because of its low cost, high electric conductivity, excellent electrochemical properties, and environmental friendliness. In this study, nickel cobaltite with nanoneedle morphology was synthesized by adopting the hydrothermal method. Change in the nickel cobaltite from nanoneedle to nanoflake morphology was induced by a template of the surface of a self-assembly graphene oxide (GO)/multiwall carbon nanotube (MWCNT) three-dimensional block matrix. Electrodes fabricated from the nanoflake nickel cobaltite, GO, and MWCNT composite exhibited high specific capacitance of 1525 F g(-1) at a current density of 1 A g(-1) and 1081 F g(-1) at a high current density of 100 A g(-1). When these composite electrodes were used as both the anode and cathode to assemble a symmetric super-capacitor with a 6 M KOH electrolyte, the supercapacitor exhibited a maximum energy density of 25.2 Wh kg(-1) and maximum power density of 5151 Wkg(-1). Moreover, it maintained an excellent cycling stability of 99.6% of the initial capacitance value after 7000 chargeedischarge cycles, demonstrating its remarkable potential for application in energy-storage and conversion devices. (C) 2019 The Author(s). Published by Elsevier Ltd.