Improved Modified Donnan Model accurately describes CDI equilibrium data

In an American-Israel-Dutch-Polish cooperation, the existing "normal" modified-Donnan model to describe the electrical double layer structure in (micro-)porous carbons, was significantly improved (ergo: the i-mD model) without jeopardizing the model's mathematical simplicity, allowing it to be incorporated in transport theory, and allowing it to be solved using simple spreadsheet-software such as Excel. This i-mD model was published in a special issue of the Journal of Solid State Electrochemistry, commemorating the late prof. V.S. Bagotsky. The i-mD model has the same advantage as the classical mD-model (developed in 2011 for CDI) namely that it is mathematically simple and can be used for transport modeling in porous carbons (note that the Gouy-Chapman-Stern theory will fail for sufficiently small pores, as the inherent pore overlap is not included in GCS theory), but in addition describes salt adsorption at high salinity much better. This was a weak point of the "normal" mD-model. The improvement consists of a slightly different formulation, not introducing more mathematical "fit"-parameters, and actually, the new model has a strong physical background, based on attractive ion-ion correlation forces. Prof. Martin Bazant (MIT), the senior author of the paper, comments "It is quite remarkable how such a simple model fits data so beautifully. I was very surprised myself. As far as I know, the simple form of the ion correlation force expression that we present, is new. Possibly in the future we will find out if we need a more accurate expression, but for the moment this simple model works like a charm, and it has a physical basis which has the advantage that further extensions such as considering the case of ionic mixtures becomes possible."

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