Expression of the polarization curve

Yet what interests an electrical engineer wishing to integrate an electrochemical component into a generator is its component as a whole cell, given that an electrode does not work on its own. The quasi-static function of such a component is therefore characterized by the polarization curve, i.e. the relation linking the difference in 

The inversion was performed in section 1.9, leading to activation overvoltages, when we can discount the influence of the variation in concentration of the species, i.e. the influence of diffusion. What about the expression which integrates this phenomenon of diffusion Let us return to the expressions [1.28]  

We can rewrite these expressions by expressing the activity of the species as a function of the limit currents defined in section 1.12  

We invert the above ejqrressions to express the overvoltages of the positive electrode and the negative electrode  

In each expression, the hypotheses made enabled us to separate two terms corresponding to two closely coupled phenomena, which are the charge transfer and the transport of species. Thus, we recognize the first term, identified as an activation overvoltage rj, related to charge transfer, shown in section 1.9. The second term 

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