Novel Technique Extends Durability of Lightweight Batteries

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Researchers from Massachusetts Institute of Technology (MIT) used oil barrier between the aluminum electrode and the electrolyte to reduce corrosion in aluminum-air batteries

Metal-air batteries are light-weight and compact in size. However, these batteries degrade quickly due to corrosion at their electrode when not in use. Although non-rechargeable aluminum-air batteries are less expensive and more compact and lightweight than lithium-ion batteries, they can lose 80% of their charge in a month. To overcome the problem of corrosion in aluminum-air batteries, a team of researchers from MIT introduced an oil barrier between the aluminum electrode and the electrolyte. The oil is rapidly pumped away and is replaced with electrolyte as soon as the battery is used. According to the team, use of oil barrier reduces the energy loss to 0.02% a month. The research was published in the journal Science on November 08, 2018.

The new approach consists of a thin membrane, which is placed between the battery electrodes. Both sides of the membrane are filled with a liquid electrolyte when the battery is in use. However, oil is pumped into the side closest to the aluminum electrode when the battery is put on standby. This enables to protect the aluminum surface from the electrolyte on the other side of the membrane. Moreover, the novel system also benefits from aluminum’s property known as underwater oleophobicity, which states that aluminum repels oil from its surface when it is immersed in water. This allows the electrolyte to easily displace the oil from the aluminum surface when the battery is reactivated and electrolyte is pumped back in, thereby restoring the power capabilities of the battery.

The system is an aluminum-air prototype, which has longer shelf life as compared to conventional aluminum-air batteries. The team performed several tests and found that the system lasted for 24 days when the battery was first repeatedly used and then put on standby for one to two days. Moreover, the system was five times lighter and twice as compact as rechargeable lithium-ion battery packs for electric vehicles when oil and a pumping system are included in scaled-up primary aluminum-air battery packs. The research was supported by MIT Lincoln Laboratory.

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