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ISSN Imprimir: 2572-4258
ISSN On-line: 2572-4266
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THE ROLE OF MACROPORES IN THE STRUCTURE OF A POROUS ELECTRODE IN THE ELECTROCHEMICAL DOUBLE LAYER CAPACITOR: COMPUTER MODELING AND EXPERIMENTS
RESUMO
The role of macropores within the structure of a porous electrode in the electrochemical double layer capacitor (EDLC) has been studied theoretically (computer modeling) and experimentally (synthesis of activated carbons from alder wood by the thermochemical activation technique, manufacturing of electrodes and model cells). It is shown that an increase in the fraction of macropores in EDLC electrodes under galvanostatic charging leads to a linear decrease in the specific capacity. But this trend is preserved only up to a certain moment. If the volume fraction corresponding to macropores reaches approximately 30%, then a percolation cluster consisting entirely of macropores appears in the active layer of the EDLC electrode. After this, there are already two percolation clusters in the active layer: that of macropores and that of a mixture of micropores and mesopores. There is a competition between them. The macropore surface is the first to charge in the course of galvanostatic charging; the charging process has to be stopped, so that the surface of micropores and mesopores remains uncharged. The result is that the value of specific capacity turns to be small. Theoretical estimates and general conclusions have been supported experimentally in this study. The object of the study is activated carbon obtained from alder wood and electrodes on its basis. It is shown that a significant increase in the EDLC specific capacity and energy density is observed on decrease in the macropore volume in the electrode. It is also established that one can virtually provide the absence of macropores in such an activated carbon. Therefore, it is possible to obtain high specific electrochemical characteristics of such manufactured EDLC electrodes that exceed the known commercial counterparts by more than 20%.