[1][2] Al has 50 times (23.5 megawatt-hours m-3) the energy density of Li-ion batteries and is even higher than coal.
[4] While transferring 3 units of charge by one ion significantly increases the energy storage capacity, the electrostatic intercalation of the electrodes with a trivalent cation is too strong for well-defined electrochemical behaviour.
[7] The inertness and ease of handling of aluminium in an ambient environment offer safety improvements compared with Li-ion batteries.
A battery can maximize its energy output levels by: Since 2020,[10] the most commonly used electrolyte for rechargeable Al batteries are acidic room temperature non-aqueous ionic liquids (IL) made of aluminium chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride ([EmIm]Cl).
[11][13] The electrolyte and water exothermically react to form gasses such as H2, Cl2 and HCl which causes cell expansion/distortion and reduction in performance (lower Coulombic efficiency, irreversible decay of capacity).
[12][13] The end result is an unstable cell, safety issues due to leakage and corrosion, and more complex and costly manufacturing requirements.
[13] Aside from improving moisture stability, the added advantage of this solution is its increased safety and flexible architecture.
They can also develop dendrites that can short-circuit and catch fire whereas the non-volatile and nonflammable ionic liquid electrolyte in the Al battery improves its safety.
[19] Ionic liquid electrolytes, while improving safety and the long term stability of the devices by minimizing corrosion, are expensive and may therefore be unsuitable.
The thicker anode features faster kinetics, and the prototype operated for 10k cycles without signs of failure.
[22] Around 2010,[16] Oak Ridge National Laboratory (ORNL) developed and patented a high energy density device, producing 1,060 watt-hours per kilogram (Wh/kg).
[24] Vanadium oxide has an open crystal structure with greater surface area and reduced path between cathode and anode.
[26][27] The battery was made of an aluminium anode, liquid electrolyte, isolation foam, and a graphite cathode.
[28] In 2016, the lab tested these cells through collaborating with Taiwan's Industrial Technology Research Institute (ITRI) to power a motorbike using an expensive electrolyte.
In June 2015, the High Specific Energy Aluminium-Ion Rechargeable Batteries for Decentralized Electricity Generation Sources (ALION) project was launched by a consortium of materials and component manufacturers and battery assemblers as a European Horizon 2020 project led by the LEITAT research institute.
[31][32] The project objective is to develop a prototype Al-ion battery that could be used for large-scale storage from decentralized sources.
The project sought to achieve an energy density of 400 Wh/kg, a voltage of 48 volts and a charge-discharge life of 3000 cycles.
3D printing of the battery packs allowed for large Al-ion cells developed, with voltages ranging from 6 to 72 volts.
[34] In 2022, MIT researches reported a design that used cheap and nonflammable ingredients, including an aluminium anode and a sulfur cathode, separated by a molten chloro-aluminate salt electrolyte.
[37] In 2019 researchers from Queensland University of Technology developed cryptomelane based electrodes as cathode for aluminium ion battery with an aqueous electrolyte.
[8] The team constructed batteries with aluminium anodes, pristine or modified few-layer graphene cathodes, and an ionic liquid with AlCl3 salt as the electrolyte.
[39] In December 2017 a Zhejiang University team announced a battery using graphene films as cathode and metallic aluminium as anode.
The 3H3C (Trihigh Tricontinuous) design results in a graphene film cathode with excellent electrochemical properties.
Claimed properties:[40][41] Another approach to an aluminium battery is to use redox reactions to charge and discharge.