Influence of structural properties on (de-)intercalation of ClO4− anion in graphite from concentrated aqueous electrolyte

Abstract

Graphite intercalation compounds (GICs) are widely known for their remarkable multifold physico-chemical properties and their numerous state-of-the-art applications, such as energy storage, sensors, lubrication, catalysis, magneto-optics, superconductivity, etc. However, the properties of GICs largely depend on the synthesis technique, structure, and morphology of the graphite; the size and properties of the intercalant species and its concentration in the host material. Accordingly, in the field of electrochemical energy storage, the appearance of novel ionic systems and detailed investigations of GICs are highly desired. In this study, two different types of graphite, natural graphite (NG) and kish graphite (KG), were used to gain insights into the intercalation of ClO4− anion in graphite from a concentrated Al(ClO4)3 aqueous electrolyte solution through extensive electrochemical studies and various in situ and ex situ spectroscopic characterization techniques. An analysis of cyclic voltammograms indicated the presence of surface-controlled charge storage along with diffusion-controlled ion intercalation into the interlayer spaces in NG and KG. Additionally, a comparative study on the electrochemical behavior of these two types of graphite showed differences that can be correlated with their structural properties. These findings open new perspectives for GIC formation in concentrated aqueous electrolytes and applications in electrochemical energy storage.