Magnesium is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole.
Pellion Technologies is using computational screens to identify a suitable cathode for magnesium-ion batteries.
Magnesium is the eighth most abundant element in the earth’s crust. Pellion Technologies hopes to make magnesium-ion batteries abundant on the earth’s surface.
In 2009, Khosla Ventures provided Massachusetts-based Pellion with seed capital (here's Mr. Khosla talking about energy storage). In 2010, ARPA-E awarded the startup a $3.2 million grant. Now, the company is willing to talk about its progress.
According to Pellion, its rechargeable magnesium battery will have a higher energy density (energy per unit volume) and specific energy (energy per unit weight) than today’s lithium-ion batteries, which are used in portable electronics and electric vehicles.
Click Image To Enlarge
Josh Nevin, Pellion’s VP of Operations and Business Development says.
“Because magnesium-ions transfer two electrons per atom, if you intercalate magnesium instead of lithium into a suitable cathode, you get twice the energy density right off the bat. The other key is the magnesium metal anode, [which] provides much higher energy density than conventional lithium-ion anodes. The net result is a battery with up to three times the energy density of state-of the-art lithium-ion batteries”
Pellion also claims that its magnesium battery will have a longer cycle life than today’s lithium-ion battery.
Nevin also said.
“When you cycle a lithium anode, the lithium metal that plates grows like moss on a tree. This can eventually lead to problems. We don’t have that problem with magnesium, [which] plates in a nice, uniform distribution. Our team has been able to demonstrate over 3,000 cycles at 100 percent depth of discharge with less than 15 percent capacity fade.”
Magnesium is not only plentiful, but also inexpensive and safe. In addition, magnesium batteries have the potential to be drop-in replacements for lithium-ion batteries.
So far, so good. But to commercialize a rechargeable battery that uses a magnesium metal anode, Pellion must also select a complementary cathode. That’s the rub; previous efforts to develop a magnesium battery have failed to identify a suitable cathode.
In 2000, Doron Aurbach, a Professor of Chemistry at Israel’s Bar-Ilan University, demonstrated the first rechargeable magnesium battery. The discovery generated significant, if short-lived, interest. Aurbach had used a less-than-ideal cathode and therefore demonstrated a battery with low energy density.
For the next decade, neither Aurbach nor his colleagues were able to identify a better cathode. As a result, interest in magnesium batteries waned.
Nevin said.
“Many researchers simply moved on. We think that was shortsighted. Professor Aurbach’s battery really had phenomenal performance and was only limited by its cathode.”
To identify a better cathode, Pellion begins with a computational screen. As the company zeroes in on potential targets, it engages in targeted synthesis and electrochemical testing.
Nevin said.
“Before we make any material, we compute its fundamental properties in a high-performance computing environment, literally at the electron level. We compute voltage, capacity, and mobility. We conduct very fundamental science, computationally, well before we synthesize anything in the lab.”
Pellion's co-founders are Gerbrand Ceder, a Professor of Materials Science and Engineering at MIT, and Kristin Persson, a chemist at Lawrence Berkeley National Laboratory. The company’s team includes Edward Buiel, the former CTO of Axion Power, and Aurbach, who serves as a scientific advisor.
By leveraging its high-throughput techniques, Pellion has already tested more than 10,000 cathode candidates. The company has zeroed in on about a dozen materials -- Nevin won’t go into further detail -- which it is testing and cycling in its lab. Pellion has also developed “several classes of electrolytes” -- again, no additional details, for now -- for potential use in its magnesium battery.
Of course, magnesium is but one of many potential lithium alternatives. Researchers and entrepreneurs are exploring Li-S, Li-air, Li-cobalt, Zn-air and Na-metal halide, among many other approaches. And Pellion isn’t alone in working to commercialize magnesium-ion batteries. Earlier this year, Toyota revealed that it too is developing a magnesium battery.
Toyota has estimated that its magnesium battery won’t be available until 2020. In June, ARPA-E acknowledged Pellion was one of its riskier projects.
Still, the Pellion team is undeterred and believes it is well on its way to solving magnesium’s historic challenges. For example, a longstanding challenge in magnesium battery development has been magnesium’s lower mobility relative to lithium, which has limited magnesium’s rate of charge and discharge.
Nevin said.
“With our computations, we have shown there are materials with magnesium mobility comparable to that of lithium in common lithium-ion systems. Magnesium mobility is not nearly the problem many feared.”
COMMENTARY: According to the Department of Energy, Pellion Technologies, an MIT spin-out company,
"will develop inexpensive high-energy-density rechargeable magnesium-ion batteries with the potential to disrupt current energy storage technologies for electric and hybrid-electric vehicles. To develop a game-changing 33 magnesium-ion battery, Pellion will leverage high throughput computational materials design, coupled with accelerated materials synthesis and electrolyte optimization, to identify new high-energy density magnesium cathode materials and compatible electrolyte chemistries. If successful, this project will develop the first commercial magnesium-ion battery and will establish U.S. technological leadership in this exciting new high energy battery chemistry for electrified vehicle applications."
If you click on the Pellium Technologies link, you must have permission to view their website, so it's difficult to learn more about their magnesium-ion battery technology.
In January 10, 2011 Bloomberg interviewed Jeffrey Makarewicz, the engineer managing the U.S. magnesium-ion battery project for Toyota, and he said in an interview at the North American International Auto Show in Detroit:
“Going from nickel-metal hydride to lithium ion, you essentially double the energy capacity. Lithium ion theoretically, under ideal conditions, has a capacity of about 2,000 kilowatt hours. That’s still not enough to really make a very competitive battery that’s necessary for future plug-in, electric and hybrid-electric vehicles.”
I was hoping to find more information about magnesium-ion technology, and found this interesting article by an LG Chemical Company magnesium-ion battery pack that consists of 220 cells for a 16,500 Wh capacity.2. The literature from LG Chemical reports information on their 10 AH cell weighing 243 g each; a 20 AH cell would weigh about 486 g (made by keeping 2-10 AH cells in parallel). Of these 20 AH cells, 220 should weigh 107 kg with an assembled weight of 120 kg.
The Use of Magnesium in Lightweight Lithium-Ion Battery Packs
The fact that magnesium is cheap and very plentiful on earth, something that lithium definitely is not, makes it very attractive as an alternative to replace lithium in today's electric batteries for laptops, smartphones, and electric vehicles. If Pellion Technologies can can develop a suitable cathode, this could be very interesting indeed. I look forward to following this company and will present any updates.
Courtesy of an article dated November 17, 2011 appearing in GreenTechMedia
Comments