Alkali metal insertion into hard carbon – the full picture†
Carbon-based anodes are technologically highly relevant for Li and post-Li ion batteries. While the storage mechanism of Li in graphite is essentially understood, the alkali metal intercalation into carbon derivatives has been strongly debated. Here, we present a combined computational and experimental study on the intercalation of Li and Na into hard carbon, elaborating on the impact of different alkali metals on the storage mechanism. Our results give strong evidence that the intercalation of Li and Na into hard carbon follows the same route and moreover, shows that in operando Raman scattering is a sensitive and powerful tool for characterizing the intercalation mechanism in carbon based materials. In fact, by exploiting the so-called double resonance, even information on the electronic structure can be obtained. Finally, theoretical predictions for the insertion mechanism of K are presented.