Influence of the electrode nano/microstructure on the electrochemical properties of graphite in aluminum batteries

TL;DR

This study investigates how the micro and nanostructure of graphite electrodes affects their electrochemical performance in aluminum batteries, revealing porosity loss and ion trapping as key factors in capacity irreversibility.

Contribution

It introduces a comprehensive characterization approach linking graphite microstructure modifications to electrochemical behavior in aluminum batteries.

Findings

Porosity decreases significantly during initial cycles.

Microstructural changes lead to ion trapping.

The methodology can be applied to other carbon materials.

Abstract

Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4 in graphite, has been fully characterized by correlating the micro/nanostructural modification to the electrochemical performance. To achieve this aim a combination of X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and computed tomography (CT) has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon-based energy-related materials. Introduction