The article doesn't mention the cathode, it just says the electrolyte is urea (CO(NH2)2) into which you can dissolve aluminum chloride (AlCl3) or, more precisel

The article doesn't mention the cathode, it just says the electrolyte is urea (CO(NH2)2) into which you can dissolve aluminum chloride (AlCl3) or, more precisely, an ionized variant like AlCl4- or Al2Cl7-. Changing between those two frees up some electrons. The cathode is probably lithium manganese dioxide, it changes between MnO2 and Li+ and LiMnO2. An aluminum-ion electrochemistry reaction is described here: https://en.wikipedia.org/wiki/Aluminium-ion_battery#Electrochemistry https://en.wikipedia.org/wiki/Aluminium-ion_battery#Electroc... Note that it's oxidation as in oxidation/reduction, using chloride ions, not oxidation as in oxygen. Turning aluminum oxide into aluminum is done with acid/base reactions and high temperatures, I don't think it's achievable with rechargeable electrochemistry.