Researchers develop molten air batteries due to their high-energy density for commercial potential in electric vehicles and energy storage. Again and all due to their high-energy density! So Back in 2014, Molten air batteries have significantly increased storage capacity over lithium batteries for electric vehicles!

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For starters and at a simple level, batteries are made up of three separate parts. They are the anode, cathode, and some form of electrolyte. When a battery is connected to an electric circuit, a chemical reaction takes place in the electrolyte. Thereby causing ions to flow through it one way, and electrons to flow through the outer circuit in the other direction.

So consequently electric vehicles offer many advantages. For example and including reducing greenhouse gas emissions and the country’s dependence on imported petroleum. Yet, at least one barrier stands in the way or is becoming less of an issue is their large-scale adoption and range anxiety.

Now while the 2014 electric vehicle Nissan Leaf, for example, has a range of just 84 miles. That’s on a fully charged battery. The current e-golf has only 111 miles of range.

As ChemistryWorld reports in 2013:

Inexpensive batteries with better energy storage densities are needed for many applications. For example, one barrier to the large-scale adoption of electric cars is the limited distance they can travel before their battery needs recharging.

Stuart Licht and his group at George Washington University think their molten air batteries could be the answer. They made three different versions of the battery using iron, carbon or vanadium boride as the molten electrolyte. Just like metal–air batteries, molten air batteries use oxygen from the air as the cathode material instead of an internal oxidizer, which makes them light. And similar to very high-energy density vanadium boride–air batteries. So molten air batteries can store many electrons per molecule.

Another important advantage of molten air batteries is that, unlike some other high-energy batteries, the molten air battery is rechargeable. The high electrochemical activity of their molten electrolytes enables electrons to be stuffed back into the electron-storing material via unusual electrochemical pathways.

So with support from the National Science Foundation, researchers at George Washington University, led by Stuart Licht think they have developed a novel solution. Now they’re calling it the molten air battery.

These new rechargeable batteries, which use molten electrolytes, oxygen from air, and special “multiple electron” storage electrodes. They have the highest intrinsic electric energy storage capacities of any other batteries to date. Their energy density, durability and cost effectiveness. All give them the potential to replace conventional electric car batteries. Comments from Licht, a professor in GWU’s Columbian College of Arts and Sciences’ Department of Chemistry.

The researchers started with iron, carbon or vanadium boride. That’s for their ability to transfer multiple electrons. As a result, molten air batteries made with iron, carbon or vanadium boride. They can store three, four and 11 electrons per molecule. Mind you and respectively, giving them 20 to 50 times the storage capacity of a lithium-ion battery. That which is only able to store one electron per molecule of lithium.

“Molten air introduces are an entirely new class of batteries,” Licht said.

Other multiple-electron-per-molecule batteries the Licht group has introduced, such as the super-iron or coated vanadium boride air battery, also have high storage capacities. But they had one serious drawback: They were not rechargeable. Rechargeable molten batteries (without air), such as a molten sulfur battery. Because they have been previously investigated. Yet are limited by a low storage capacity.

The new molten air batteries, by contrast, offer the best of both worlds. That’s a combination of high-energy storage capacity and reversibility. As the name implies, air acts as one of the battery electrodes, while simple nickel or iron electrodes can serve as the other. “Molten” refers to the electrolyte, which is mixed with reactants for iron, carbon or vanadium boride, then heated until the mixture becomes liquid. The liquid electrolyte covers the metal electrode and is also exposed to the air electrode.

The batteries are able to recharge in electric vehicles by electrochemically reinserting a large number of electrons. The rechargeable battery uses oxygen directly from the air, not stored, to yield high battery capacity. The high activity of molten electrolytes is what allows this charging to occur, according to Licht.

The electrolytes are all melted to a liquid by temperatures between 700 and 800 degrees Celsius. This high-temperature requirement is challenging to operate. Especially inside an electric vehicle. However such temperatures are also reached in conventional internal combustion engines.

In conclusion, the researchers are working on their model. All to make the high-energy density batteries viable candidates. All for extending electric cars’ driving range. In the Licht group’s latest study, the molten air battery operating temperature is lowered to 600 degrees Celsius or less. The new class of molten-air batteries could also be used for large-scale energy storage for electric grids.

— Lisa Van Pay, George Washington University
— Lauren Ingeno, George Washington University

Source: National Science Foundation, June 27, 2014