Aluminium-ion batteries are conceptually similar to lithium-ion batteries, but possess an aluminium anode instead of a lithium anode. While the theoretical voltage for aluminium-ion batteries is lower than lithium-ion batteries, 2.65 V and 4 V respectively, the theoretical energy density potential for aluminium-ion batteries is 1060 Wh/kg in comparison to lithium-ion's 406 Wh/kg limit.[3] The large difference in energy density potential is due to the fact that aluminium ions have three valence electrons while lithium ions only have one. Aluminium is also more abundant than lithium, lowering material costs.[4]