EDLstruct - Effect of carbon electrodes porous structure and electrolyte properties on the formation and composition of the electrical double-layer

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The formation of an electrical double-layer (EDL) in a porous conductive electrode, e.g., from activated carbon (AC), represents one of the most appealing strategies for fast storage of energy and, consequently, for the realization of high power energy storage devices. However, the existing models of EDL which consider the electrolyte border with a flat surface cannot be applied to the case of microporous (<2 nm) AC electrodes. Recently, in-situ techniques have provided important information about the EDL properties in AC electrodes, yet they were implemented with a unique electrolyte and a unique type of porous carbon. Therefore, the objective of the EDLstruct project is to implement a variety of organic electrolytes with a variety of carbons of well-defined porous structure in order to study: i) the influence of pore size and molecules size on the ions/solvent ratio under polarization, and ii) to find correlations between the EDL structure and the decay of electrochemical performance of carbon electrodes depending on temperature and electrodes potential. In order to realize this program, strong competence in carbonaceous materials (PUT group) as well as in electrolytes (FSU Jena group) is needed. In addition, the use of in-operando techniques (PUT) is required to monitor the effects of molecular fluxes and EDL decomposition during polarization of electrodes. Hence, the research objectives will be reached by conducting 5 work packages. FSU Jena will design a number of non-aqueous electrolytes (WP1), while PUT will design and characterize ACs with different structural properties (WP2). The electrochemical performance of AC electrodes in combination with the considered electrolytes will be investigated by both groups. In order to acquire information about the double-layer formation, post-mortem analyses of polarized electrodes by thermoprogrammed desorption and in-operando electrical dilatometry will be carried out by PUT (WP3). The influence of the electrode-electrolyte interaction on the thermal stability of the double-layer will be investigated in WP4 by FSU Jena (TGA/DSC) and PUT (electrochemical on-line mass spectrometry). The experimental results will be critically discussed in WP5, giving rise to publications and presentations at international conferences.