天然高分子を用いた電気二重層キャパシタ用電解質の調製及びキャラクタリゼーション

関西大

Preparation and characterization of nonaqueous electrolyte from natural polymers for electric double-layer capacitors [論文要旨及び審査の要旨]

関西大

Synthesis and Characterization of Nanofiber of Oxidized Cellulose from Nata De Coco

Oxidized cellulose (OC) nanofiber was successfully prepared from the dry sheet of Nata De Coco (DNDC) using the mixture system of HNO3/H3PO4–NaNO2 for the first time. The carboxyl content of the OC was investigated at different conditions (HNO3/H3PO4 ratios, reaction times, and reaction temperatures). The results revealed that the carboxyl content of the OC increased along with the reaction time, which yielded 0.6, 14.8, 17.5, 20.9, 21.0, and 21.0% after 0, 6, 12, 36, and 48 hours, respectively. The reaction yields of the OC ranged between 79% and 85% when using HNO3/H3PO4 ratio of 1 : 3, 1.4% wt of NaNO2 at 30°C at different reaction times. From the structural analysis, the OC products showed a nanofibrous structure with a diameter of about 58.3–65.4 nm. The Fourier transform infrared spectra suggested the formation of carboxyl groups in the OC after oxidation reaction. The crystallinity and crystalline index decreased with an increase of reaction time. The decrease of crystallinity from oxidation process agreed with the decrease of degree of polymerization from the hydrolysis of β-1,4-glycosidic linkages in the cellulose structure. The thermal gravimetric analysis results revealed that the OC products were less thermally stable than the raw material of DNDC. In addition, the OC products showed blood agglutinating property by dropping blood on the sample along with excellent antibacterial activity

Preparation and Characterization of Electrospun Gelatin Nanofibers for Use as Nonaqueous Electrolyte in Electric Double-Layer Capacitor

A novel nanofibrous gel electrolyte was prepared via gelatin electrospinning for use as a nonaqueous electrolyte in electric double-layer capacitors (EDLCs). An electrospinning technique with a 25 wt% gelatin solution was applied to produce gelatin electrospun (GES) nanofiber electrolytes. Structural analysis of the GES products showed a clearly nanofibrous structure with fiber diameters in the 306.2–428.4 nm range and exhibiting high thermal stability, high tensile strength, and a stable form of nanofibrous structure after immersion in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4). After testing over a range of spinning times, GES electrolytes that were produced at 25 min (GES-25) had a suitable thickness for the assembly of EDLC with the optimized tensile properties and were used to fabricate EDLC test cells with EMImBF4. These test cells were compared to those with pure EMImBF4 and a separator as an electrolyte. The electrochemical properties of the test cells were characterized by charge-discharge testing, discharge capacitance, and alternative current (AC) impedance measurements. AC impedance measurements showed that the test cell with the GES-25/EMImBF4 gel electrolyte showed slightly poorer contact with the electrode when compared to that with pure EMImBF4, whereas exhibited comparable IR drop and discharge capacitance (calculated capacitance retention was 56.6%). The results demonstrated that this novel gel electrolyte can be used as a nonaqueous electrolyte in order to improve the safety in EDLCs

Preparation and Electrochemical Performance of Chitosan-based Gel Polymer Electrolyte Containing Ionic Liquid for Non-aqueous Electric Double Layer Capacitor

A novel gel polymer electrolyte based on chitosan with 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) is prepared with a new procedure and applied to electric double layer capacitors (EDLCs). The chitosan-based gel polymer electrolyte causes less liquid leakage than the previous one. In this electrolyte system, EMImBF4 plays the roles of both a solvent for dissolving chitosan and a charge carrier ion for EDLC application. The present chitosan solution for gel polymer electrolytes shows acidity, and its acidity is raised by increasing the amount of EMImBF4 and the preparation temperature. The electrochemical stability of the electrolyte is decreased as the acidity of its chitosan solution increases. At 25°C, an EDLC cell with the electrolyte containing 70 wt.% EMImBF4 showed good charge-discharge performance and lower electrode/electrolyte interfacial resistance than those of a liquid-phase EMImBF4 system