Aluminium carbon battery is an emerging battery technology based on aluminium anodes and cathodes made from carbon /graphite. The materials are abundant, and the production of these batteries might be even simpler than today’s Li-ion batteries (depending on the electrolyte). The charge-discharge mechanism is based on deposition and stripping of aluminium on the anode, while anions from the electrolyte are intercalating into the carbon cathode. The most commonly employed electrolyte is based on the AlCl3 salt dissolved in the ionic liquid EmimCl. The active anion with respect to the cathode intercalation reaction is normally claimed to be AlCl4-, even if the size of this anion is much larger than the interlayer spacing of graphite. In addition, side reactions (partly reversible) lead to the formation of surface products that might be crystalline in nature. Operando X-ray diffraction studies are therefore well suited for improved understanding of this intercalation reaction.