On how interactions influence kinetic limitations in alkali-ion batteries. Application to Li-ion intercalation into graphite through voltammetric experiments

Here, we report on a novel study for battery application regarding the impact of interactions in charge transfer and diffusional features in finite-size systems. An easy way to represent these features is the construction of a map called zone diagram for voltammetry simulations, where different domains are related with a characteristic charge transfer-diffusional limitation. This is particularly relevant for alkali-ion intercalation into hosts, since interactions between inserted ions have demonstrated to have a strong influence on the electrochemical behaviour of these systems. The Frumkin isotherm is used here as a general model to understand the simplest scenarios, which introduces interactions between inserted particles in their thermodynamic descriptions. We show how the impact of these interactions becomes more evident for systems that present a reversible charge transfer. On the contrary, for irreversible reactions, features tend to become independent of interactions. Finally, we apply the methodology to understand some features of Li-ion intercalation in graphite films. It comes out that for this system, a surface wave (adsorption like) behaviour could only be reached in experiments lasting more than a year. This explains the large hysteresis found in experiments. We also constructed a sweep rate-film thickness zone diagram, to present the results in a more straightforward fashion to experimentalists.