Aluminium-ion battery

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

one Al3+ is equivalent to three Li+ ions

in conventional intercalation cathodes. Thus, since the ionic radii of

Al3+ (0.54 Å) and Li+ (0.76 Å)

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 behaviour.

Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity.

The inertness of aluminium and the ease of handling in an ambient environment is expected to offer significant safety improvements for this kind of battery. In addition, aluminium 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 the ability to exchange three electrons. This again means that the energy stored in aluminium batteries on a per-volume basis is higher than that in other metal-based batteries. Hence, aluminium 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.

Challenges: Aluminium-ion batteries have a relatively short shelf life. The combination of heat, rate of charge, and cycling can dramatically decrease energy capacity. One of the primary reasons for this short shelf life is the fracture of the traditional graphite anode, the Al ions being far larger than the Li-ions used in conventional battery systems.

When metal ion batteries are fully discharged, they can no longer be recharged. Ionic electrolytes, while improving safety and the long term stability of the devices by minimizing corrosion, are expensive to manufacture and purchase and may therefore be unsuited to the mass production of Al ion devices.

In addition, current breakthroughs are only in limited laboratory settings, where a lot more work needs to be done on scaling up the production for use in commercial settings.

Lithium-ion comparison 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.

Today's lithium-ion batteries have high power density (fast discharge) and high energy density (hold a lot of charges). They can also develop dendrites, similar to splinters, that can short-circuit a battery and lead to a fire. Aluminium also transfers energy more efficiently.

Inside a battery, atoms of the element — lithium or aluminium — give up some of their electrons, which flow through external wires to power a device. Because of their atomic structure, lithium ions can only provide one electron at a time; aluminium can give three at a time. Aluminium is also more abundant than lithium, lowering material costs.