Aluminum-ion batteries are a class of rechargeable battery in which aluminum ions provide energy by flowing from the negative electrode of the battery, the anode, to the positive electrode, the cathode. When recharging, aluminum ions return to the negative electrode, and can exchange three electrons per ion. This means that insertion of one Al3+

is equivalent to three Li+ ions in conventional intercalation cathodes. Thus, since the ionic radii of Al3+ (0.54 A) and Li+ (0.76 A) are similar, significantly higher models of electrons and Al3+ ions can be accepted by the cathodes without much pulverization. The trivalent charge carrier, Al3+ is both the advantage and disadvantage of this battery. While transferring 3 units of charge by one ion significantly increase the energy storage capacity but the electrostatic intercalation of the host materials with a trivalent cation is too strong for well-defined electrochemical behavior. Rechargeable aluminum-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. The inertness of aluminum and the ease of handling in an ambient environment is expected to offer significant safety improvements for this kind of battery. In addition, aluminum possesses a higher volumetric capacity than Li, K, Mg, Na, Ca and Zn owing to its high density (2.7 g/cm3 at 25 °C) and ability to exchange three electrons. This again means that the energy stored in aluminum-batteries on a per volume basis is higher than that in other metal-based batteries. Hence, aluminum-batteries are expected to be smaller in size. Al-ion batteries also have a higher number of charge-discharge cycles. Thus, Al-ion batteries have the potential to replace Li-ion batteries