Application of Carbon Fiber Cloth Super-Capacitor: Capacitive Deionization Device and Energy Storage Module
Date Issued
2012
Date
2012
Author(s)
Chien, Ting-Yu
Abstract
In the study, two applications of carbon fiber cloth (CFC) supercapacitor were investigated: capacitive deionization (CDI) and large-scale energy storage module.
On the basis of non-ideal reactor analysis, deionization process in a planar type CDI reactor was analyzed. The deionization capacity can be determined by conductivity measurement, and adsorption time distribution, E(t), represents the behavior of capacitive deionization, including the fraction of adsorbed ions at certain time and the effects of flow rate, cell number, and feed concentration on time of deionization step. Cumulative function, F(t), obtained by integrating E(t) can reveal the processing efficiency via slope change. Additionally, characterization of the CDI process can be achieved by normalized adsorption time distribution, E(theta); an characterization equation was obtained by applying lognormal model in the fitting of E(theta). By using characterization equation and fitting of mean adsorption time which was done by nonlinear surface fitting method and equation addition fitting method, E(t) can be reconstructed for any operation condition; as a result, behavior and time of deionization step can be evaluated. The analysis is beneficial to practical use because it can estimate the performance in advance by determining corresponding process time and reactor size. Further improvement can focus on the estimation of deionization capacity, and if it is integrated together, a complete CDI process analysis relating to deionization capacity, process time, and reactor size can be achieved.
The planar stack configuration was also applied in the investigation of large-scale carbon fiber cloth supercapactior module. The C/A ratio of CFC, potential window, the material of current collector and separator, and the module configuration were optimized before scaling up the supercapacitor module. Each CFC cell of 15 cm × 15 cm can deliver 110 F and 1.5 V at 0.2 A. The results of Large-scale CFC supercapacitor submodule connected in parallel and serial were studied; a 11-cell serial submodule can deliver 11.2 F and 16V, and a 6-cell parallel submodule can deliver 840 F and 1.5V. In addition, the trend of parallel/serial connection was studied, and by fitting equations, the electrochemical properties of module no matter how the cells are connected can be evaluated. It is believed that the study of large-scale module set up and the evaluation of module performances can be applied to the preparation and design of large-scale modules because it includes thorough information about scaling up from small-scale cell to large-scale module.
Subjects
Capacitive deionization
Large-scale supercapacitor module
Supercapacitor
Carbon fiber cloth
Process analysis
Type
thesis
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