A novel catalyst for high-energy aluminum-air flow batteries

October 15, 2018, Ulsan National Institute of Science and Technology
Novel catalyst for high-energy aluminum-air flow batteries
A new type of auminum-air flow battery, which is more energy efficient than the existing LIBs. Credit: UNIST

A recent study affiliated with UNIST has introduced a novel electric vehicle (EV) battery technology that is more energy efficient than gasoline-powered engines. The new technology involves replacing battery packs instead of charging them, bypassing the slow-charging issues of existing EV battery technology. It also provides lightweight, high-energy density power sources with little risk of burning or explosion. This breakthrough has been led by Professor Jaephil Cho and his research team in the School of Energy and Chemical Engineering at UNIST. Their findings have been published in Nature Communications.

The researchers developed a new type of aluminum-air flow battery for EVs. The new battery outperforms existing lithium-ion batteries in terms of higher density, lower cost, longer cycle life, and higher safety. Aluminum-air flow batteries are primary cells, which means they cannot be recharged via conventional means. In EVs, they produce electricity by replacing the aluminum plate and electrolyte. Considering the actual energy density of gasoline and aluminum of the same weight, aluminum is superior.

"Gasoline has an energy density of 1,700 Wh/kg, while an aluminum-air flow battery exhibits a much higher energy density of 2,500 Wh/kg with its replaceable electrolyte and aluminum," says Professor Cho. "This means with 1kg of aluminum, we can build a battery that enables an electric car to run up to 700km."

The new battery works much like metal-air batteries, producing electricity from the reaction of oxygen in the air with aluminium. Metal-air batteries, especially aluminium-air batteries, have attracted much attention as the next-generation battery due to their energy density higher than that of LIBs. Indeed, batteries that use aluminum, a lightweight metal, are lighter, cheaper, and have a greater capacity than a traditional LIB.

Despite their high energy , aluminum-air batteries are not widely used because of problems with high anode cost and byproduct removal when using traditional electrolytes. Professor Cho has solved this issue by developing a flow-based aluminum-air battery to alleviate the side reactions in the cell, where the electrolytes can be continuously circulated.

In the study, the research team prepared a silver nanoparticle seed-mediated silver manganate nanoplate architecture for the oxygen reduction reaction (ORR). They discovered that the silver atom can migrate into the available crystal lattice and rearrange the manganese oxide structure, thus creating abundant surface dislocations. Thanks to improved longevity and , the team anticipates that their aluminum-air flow battery system could potentially bring more EVs to the road with greater range and substantially less weight with zero risk of explosion.

"This innovative strategy prevented the precipitation of solid by-product in the cell and dissolution of a precious metal in air electrode," says Jaechan Ryu, first author of the study. "We believe that our AAFB system has the potential for a cost-effective and safe next-generation energy conversion system."

The discharge capacity of aluminum-air flow is 17 times that of conventional aluminum air batteries. Additionally, the capacity of newly developed silver-manganese oxide-based catalysts was comparable to that of the conventional platinum catalysts (Pt/C). As silver is 50 times less expensive than platinum, it is also competitive in terms of the price

Explore further: Stopping fires before they start—how a salty solution is giving lithium metal batteries a safety check

More information: Jaechan Ryu et al, Seed-mediated atomic-scale reconstruction of silver manganate nanoplates for oxygen reduction towards high-energy aluminum-air flow batteries, Nature Communications (2018). DOI: 10.1038/s41467-018-06211-3

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winthrom
not rated yet Oct 15, 2018
Does this mean an all electric personal aircraft with useful range?
Eikka
5 / 5 (1) Oct 15, 2018
Gasoline has an energy density of 1,700 Wh/kg


Gasoline has an energy density of around 8760 Wh per liter, or about 13,200 Wh per kg.They're assuming a ridiculously low efficiency of just 12.9% for the engine. An 18th century steam engine without a condenser would beat that.

https://hypertext...ik.shtml

The energy density of gasoline in a modern car engine is around 4,000 Wh/kg.
Eikka
not rated yet Oct 15, 2018
Does this mean an all electric personal aircraft with useful range?


Depends. They need to get the air to react with the aluminium, which means you need a whole filtration system and fans, compressors, etc. to get the air in and out of the battery fast enough. The battery needs to breathe, and the power it can put out is dependent on the amount of oxygen you can put in, and that pumping and filtering consumes a great deal of energy. The stated energy density can only be achieved at low power by assuming the pumping losses are neglible.

Furthermore, as the battery is reacting aluminium with oxygen which produces solid waste, the battery actually gets heavier as it discharges by a significant margin, so energy-for-energy it's no match for liquid fuels which get consumed during flight and make the plane lighter.
Eikka
not rated yet Oct 15, 2018
Another glaring issue is that the aluminium battery works by dissolving the aluminium in 6M potassium hydroxide solution, which is highly caustic and corrosive. It's not something you want to spill around.

That's a big problem when you think about how to change the electrolytes in and out of the battery. If the user has to connect and disconnect hoses, drops and spills are inevitable and then people get chemical burns. Even if it's done by robots, there's no quick connect hose that wouldn't leak one drop every time, and corrosion becomes an issue.

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