Energy storage has been called the Holy Grail of renewable energy, but battery storage has its own Holy Grail — a solid state battery.

Scientists at the Joint Center for Energy Storage Research (JCESR) say they have taken a step closer to developing a solid state battery, that is, one that uses a solid electrolyte, which would give it a higher energy density and make it less flammable and safer than batteries that use liquid electrolytes, such as most existing lithium-ion batteries.

However, while the technology is promising, commercializing it could take more than 10 years.

'Why not leapfrog?'

Scientists at the Lawrence Berkeley National Laboratory and Argonne National Laboratory were working on a magnesium battery, which offers higher energy density than lithium, but had few viable options for a liquid electrolyte, which tends to corrode other battery parts.

“Magnesium is such a new technology, it doesn’t have any good liquid electrolytes,” Gerbrand Ceder, a Berkeley Lab senior faculty scientist, said in a statement. “We thought, ‘Why not leapfrog and make a solid-state electrolyte?’”

They came up with magnesium scandium selenide spinel. Computer models indicated that the compound had good “magnesium mobility,” that is, it could transmit electrically charged magnesium ions between cathode and anode.

They synthesized the material in the lab and tested it at Argonne using nuclear magnetic resonance (NMR) spectroscopy, a technology similar to magnetic resonance imaging (MRI), which is used as a medical diagnostic tool.

The tests were among the first to prove that magnesium ions could move through the material as rapidly as the theoretical studies had predicted. “We have identified a new class of solid conductors that can transport magnesium ions at unprecedented speed,” Pieremanuele Canepa, a postdoctoral fellow at Berkeley Lab, said in a statement.

Canepa, with his Berkeley colleague Shou-Hang Bo, were the lead authors of the paper in Nature Communications, “High magnesium mobility in ternary spinel chalcogenides.” JCESR, a Department of Energy innovation hub, sponsored the study. Berkeley and Argonne are part of the DOE’s network of national research laboratories.

Potential game changer

A solid electrolyte for either lithium-ion or magnesium-ion batteries “could be game-changing,” James Frith, energy storage analyst at Bloomberg New Energy Finance, told Utility Dive via email.

A solid electrolyte would improve the energy density of a battery both in terms of weight and volume. A solid electrolyte could also improve battery safety, an issue with existing lithium-ion batteries, almost all of which use a liquid electrolyte. Liquid electrolytes have the potential to create a short circuit between the anode and cathode that can start a fire.

The JCESR finding could also contribute to efforts to use magnesium as a replacement for lithium in batteries, a hot topic among scientific researchers for years.

In addition to being potentially safer, magnesium is more abundant and easier to mine than lithium. Magnesium is the eighth most abundant element in the Earth’s crust. Lithium is the 25th most abundant element, but is relatively rare, occurring in rocks or dissolved in seawater or brine from which it has to be extracted. In addition, a magnesium ion has two positive charges, while lithium only has one, which essentially means magnesium can store almost twice as much energy in the same volume.

“For magnesium-ion batteries, finding any electrolyte that is less corrosive than the current electrolytes is a major advantage,” Frith said. “If magnesium-ion batteries using Berkeley Lab's solid electrolyte can make it out of the lab, their key advantage will be cost.”

Magnesium cost advantage

Frith noted that magnesium costs about $2,500 per ton compared with lithium’s cost of about $125,000 per ton. In addition, magnesium-ion battery cathodes do not contain cobalt, which is expensive.

That cost differential is driving researchers and startups around the world to pursue the development of a solid-state battery and to move beyond lithium-ion chemistries. That was one of the rationales Exelon made for its recent investment in Volta Energy Technologies, a startup that tests and evaluates energy storage technologies.

Researchers in Switzerland are also working on developing a battery that would use magnesium and sodium in a solid electrolyte. They say they have developed a solid, magnesium-based electrolyte, but are still a long way from having a “complete and functional prototype.”

More solid state research

Early this year, researchers at the University of Texas at Austin announced they have developed a lithium-ion battery that uses a solid state glass electrolyte. The team, which included senior research fellow Maria Helena Braga, was led by 94-year-old John Goodenough, the co-inventor of the lithium-ion battery. They published their findings in the journal Energy & Environmental Science.

Goodenough’s team said their new battery cells have at least three times the energy density as current lithium-ion batteries, allow for a greater number of charging and discharging cycles, and can be recharged in minutes rather than hours. They also said a glass electrolyte would enable the substitution of low cost sodium for lithium.

The UT Austin team is working on several patents and is looking to work with battery manufacturers to develop and test new materials in electric vehicles (EVs) and energy storage devices.

Electric vehicle needs

For EVs, a lot is riding on developing more powerful, long-lasting batteries. In November, EV maker Fisker, along with battery maker Sakti3, filed patents for a solid-state battery they say will enable EV ranges of more than 500 miles on a single charge and charging times as low as one minute.

They said their battery will have 2.5 times the energy density of lithium-ion batteries. Fisker expects “automotive applications” to be “production grade ready from 2023 onwards.”

“The way the industry stands at the moment, EVs lead the way in terms of technology and stationary storage follows in its path,” Frith said.

The path from the lab to market is long, anywhere from five to 10 years. For a technology like JCESR’s solid magnesium electrolyte, it could be even longer. Canepa points out that his team does not yet even have a prototype battery. “The li-ion cell of your phones was first tested 35 years ago,” he noted.

Frith called the Fisker technology “very promising,” but said the real question is “Can the manufacturing of these solid state batteries be integrated into the current lithium-ion manufacturing capacity?”

That capacity is about to get much larger. There are several gigafactories under construction around the globe that will contribute to economies of scale and could drive further cost reductions for li-ion batteries, even as li-ion energy density increases year by year.

New technologies may be better, but they also are often more costly. That means any competitor seeking to unseat li-ion is playing catch up in a very competitive race. For new battery technologies, one route to commercial development would be to deploy them first in high-end EVs where increased energy density is seen as an advantage, despite the increased cost, Frith told Utility Dive.