Scientists from Australia and China have developed the world’s first non-toxic aluminum-radical battery based on water. The concept of the invention was outlined in an article published in the Journal of the American Chemical Society (JACS).
Aluminum-ion batteries (AIB) have gained significant attention from scientists due to their potential cost-effectiveness, as aluminum is the third most abundant element in the Earth’s crust (8.1%). AIBs are also capable of storing more energy per unit volume compared to lithium-ion batteries (LIB), thus offering higher energy density.
One of the main challenges of aluminum-ion batteries is the slow transport of Al3+ ions, resulting in low cathode efficiency. To address this issue, polymers with alternating donor and acceptor components are used as cathodes. However, these polymers result in low battery output voltage.
To demonstrate the possibility of creating a safe and efficient aluminum-radical battery, researchers investigated the behavior of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) in organic and aqueous electrolytes.
TEMPO is an electrode material with high redox potential widely used as a cathode material in multivalent metal-ion batteries. However, TEMPO has not been applied in aluminum-ion batteries due to an undesirable and irreversible side process called disproportionation, where the same compound acts as both a reducer and an oxidizer.
The researchers discovered that disproportionation in commonly used organic electrolytes, such as Al(OTf)3, can be turned into a reversible process by switching to a water-based environment. This allowed for the creation of the first aluminum-ion battery design based on water with radical polymers. The battery demonstrated fire resistance, stability in air, and maintained a stable output voltage of 1.25 volts and a capacity of 110 milliampere-hours per gram over 800 recharge cycles with losses of only 0.028% per cycle.
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