Exploring nature-behaviour relationship of carbon black materials for potassium-ion battery electrodes

An essential component of a working electrode is the conductive additive: whether it is used in very low amounts or constitutes the conductive matrix, its electrochemical response is not negligible. Commercially diffused carbon black species (i.e., Super P, Super C65, and Super C45) still lack an in-depth electrochemical characterisation in the emerging field of potassium-ion battery systems, which are on the way towards large-scale stationary storage application. Thus, this work aims to provide strong tools to discriminate their active role in such secondary cells. First, the effect of their pseudo-amorphous structure on the storage mechanism of potassium ions, which tend mainly to adsorb on their surface rather than intercalate within graphene layers, leading to a pseudocapacitive response, is discussed. Then, Dunn’s and Trasatti’s methods are considered to identify the potential ranges in which surface-dominated reactions occur, quantifying their weight at the same time. This observation is surely linked with surface properties and exposed functional groups; thus, X-ray photoelectron spectroscopy is exploited to correlate electrochemical features with both pristine and cycled surfaces of the carbon black species.