Magnesium Energy Storage Means Never Having To Pay More For An EV

April 4th, 2018 by Tina Casey

The Intertubes were all aflutter last week with a report that electric vehicles will soon cost less than gasmobiles. That’s mainly because the cost of EV batteries will keep dropping. Less noticed in the report was a warning that continued reliance on lithium-ion energy storage could put a crimp in the works. Among other things, that’s because more people will want more EVs, which will put upward pressure on the cost of lithium for all those EV batteries.

So, who said we have to keep relying on lithium for EV batteries?

Energy Storage And EV Ownership

Electric cars are more expensive to buy than gasmobiles, mainly because EV batteries are far more expensive than gas tanks.

Until recently, that’s provided EV naysayers with ample ammunition for shooting down the prospects for electric mobility.

On the flip side, EV ownership can involve significantly lower fuel and maintenance costs. As far back as 2013, Edmunds ran a five-year cost-of-ownership calculation for GM’s Volt gas-electric hybrid and showed how low fuel and maintenance costs can result in a more favorable outcome for EV owners (GM’s zero waste policy is more icing on the green cake, by the way).

By 2017 energy storage costs were dropping so fast that a consensus began forming around the prospect of EVs reaching parity with gasmobiles at the point of purchase, too. The question now is how soon will that happen.

Just last week, Bloomberg updated its EV cost outlook with this observation (emphasis added):

Electric cars may be cheaper than their petroleum counterparts by 2025 if the cost of lithium-ion batteries continues to fall.

Some models will cost the same as combustion engines as soon as 2024 and become cheaper the following year, according to a report by Bloomberg New Energy Finance. For that to happen, battery pack prices need to fall even as demand for the metals that go into the units continues to rise, the London-based researcher said on Thursday.

Ruh-roh. If you caught that thing about metals and demand, run right out and buy yourself a cigar. What they mean is that rising demand for lithium could exert upward pressure on the cost of EV batteries, leading to higher costs for EVs.

To be clear, that doesn’t mean EVs will always cost more than gasmobiles. But, it does mean that price parity could be pushed farther into the future.

Magnesium Energy Storage To The Rescue…

One obvious solution is to develop energy storage technology that relies on cheap, abundant materials, and that’s where the magnesium thing comes in.

How abundant is magnesium? This abundant, says Wikipedia:

Magnesium is the ninth most abundant element in the universe. It is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus.

Oh wait, not that one. This one:

Magnesium is the eighth most abundant element in the Earth’s crust and the fourth most common element in the Earth (after iron, oxygen and silicon), making up 13% of the planet’s mass and a large fraction of the planet’s mantle. It is the third most abundant element dissolved in seawater, after sodium and chlorine.

Back in 2010, our friends over at ARPA-E ran the numbers on magnesium and came up with this (emphasis added):

Currently, most Li-Ion batteries used in EVs provide a driving range limited to 100 miles on a single charge and account for more than half of the total cost of the vehicle. To compete in the market with gasoline-based vehicles, EVs must cost less and drive farther. An EV that is cost-competitive with gasoline would require a battery with twice the energy storage of today’s state-of-the-art Li-Ion battery at 30% of the cost.

ARPA-E zeroed in on magnesium energy storage, not just because of the abundance thing but also because of the potential for beating lithium-ion batteries on range…

Prototype magnesium batteries demonstrate excellent electrochemical behavior, delivering thousands of charge cycles with very little fade.

…and eight years later, magnesium energy storage is not quite ready for prime time.

Phooey!

…Eventually!

Magnesium batteries have twice the energy density of lithium-ion batteries, which is a good thing. However, in order to recharge they need a highly corrosive liquid electrolyte, which is a bad thing.

Using a conventional, less corrosive electrolyte is out of the picture because it messes with the surface of the magnesium, and then the battery can’t recharge.

Researchers have been pursuing various pathways to blow past that obstacle, and a team at the National Renewable Energy Laboratory is pretty confident they’re on the right track (for those of you new to the topic, the electrolyte is the part of the battery that stores the charge; the other two parts are the anode and cathode, which collect and discharge).

This is the track:

…the researchers developed an artificial solid-electrolyte interphase from polyacrylonitrile and magnesium-ion salt that protected the surface of the magnesium anode.

Got all that? You can get more details from the journal Nature under the title, “An Artificial Interphase Enables Reversible Magnesium Chemistry in Carbonate Electrolytes:”

Here, we engineer an artificial Mg2+-conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements for electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V 2 O 5 full-cell in the water-containing, carbonate-based electrolyte.

There ya go. The key phrase is “highly reversible Mg chemistry,” meaning that the battery efficiently recharges.

Don’t hold your breath too much for that magnesium EV battery of the future. So far the work has been demonstrated at the prototype stage. There is more tinkering to do before this thing goes mobile.

On the other hand, magnesium batteries could be on the verge of becoming a thing, at least on a small scale. A company called Pellion Technologies won more than $3 million in funding from ARPA-E for its magnesium energy storage system back in 2009. By 2016 the company caught the eye of Motorola Solutions for energy storage applications in mobile, wireless and robotics fields.

If you have any more recent news about Pellion, drop us a note in the comment thread. Or maybe tell us how to get inside their website if you can figure that out.

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Image: by John Frenzl / NREL.









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