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EmbelRed | Project overview

 

The project addresses reductions of voltage losses in the electrolyte for a given current density. There are three sources of voltage losses: (1) The ohmic losses: caused by the non-ideal ionic and electronic transport through the membrane, electrodes and the electrolyte. (2) Activation polarization losses, which refer to the kinetics of the reaction related to the charge-transfer reactions at electrodes. (3) Concentration polarization losses, which are caused by the concentration gradients of species and are thus related to the mass transport of the species within the electrode surface.

Polarization losses occur at the electrode surface and consequently, the electrode (and hence the cell stack) will play an important role on the performance of the battery. Increasing the specific surface area in porous electrodes is convenient because it can compensate slow reactions and low concentrations of electroactive species. Also in flow cells, permeable electrodes facilitate the mass transport, reduce pressure drop and hence, decrease pumping costs. As a result, high surface area with high porosity and permeability are good characteristics of the electrodes, but incompatible with each other.

Most investigations on the improvement of electrodes are focused on carbon-based materials e.g. carbon paper and graphite felts. The studies are centred on modifying their porosity, reducing the resistivity by compression, and enhancing their catalytic activity by means of pretreatments (mostly acid and heat treatments). However, the poor control on their morphological characteristics (porosities, fiber lengths and fineness) and material quality makes difficult a systematic approach to improve the understanding of the physical and chemical processes occurring at the electrode surface.

In this project, we aim to improve this understanding with the use of embroidered electrodes, which allows us a high degree of control on their morphological characteristics and the spatial distribution of their properties.

This will permit us to achieve the following benefits:

• The direct integration of sensing electrodes to monitor in situ electrochemical processes.
• The development of an empirical systematic approach in combination with theoretical fundamentals and formation of models.
• New scientific results towards the deeper understanding of the electrochemical processes inside 3D electrodes.