There she goes again. The much-recognized research scientist Linda Nazar of the University of Waterloo has been carving her name into the solid-state battery field, and she has just one-upped herself. Along with her research group at Waterloo, Nazar has developed a new chloride-based electrolyte that could replace its liquid cousin without much fuss while delivering the same high performance, if not better.
Why Replace A Liquid Electrolyte?
The liquid platform of lithium-ion EV batteries has received much praise for performance improvements over the past decade or so, as showcased by an ever-growing list of electric vehicle makers. However, researchers have already been aiming for a sea change in electrolyte design, the basis of which is to replace the liquid with a solid material.
If all goes according to plan, the solid-state battery of the future will provide automakers with lower costs, lighter weight, a smaller footprint, and improved efficiency. The supply chain could also be streamlined, partly because a solid-state battery doesn’t need the kind of fire safety engineering required of liquid electrolytes.
Researchers are still hammering out the technology details, but automakers and other energy storage stakeholders are already cottoning on to the idea. Ford and BMW are among those looking to ditch liquid electrolytes, as are Daimler, Stellantis, Kia, and Hyundai, among others. You can also add GM to the next-generation energy storage list.
Solving The Solid-State Battery Puzzle
One of Nazar’s big energy storage breakthroughs was announced during the summer of 2020. In collaboration with postdoctoral research associate Zhizhen Zhang and fellow Professor Pierre-Nicholas Roy, Nazar’s group focused on resolving one key part of the solid-state battery puzzle, which is how to match or beat the conductivity of liquid electrolytes. To get an idea of the scope of the challenge, try swimming through a concrete wall instead of a pool of water.
“Very few solid-state electrolytes have ion conductivity as high as liquid organic electrolytes so Nazar and her group are speeding up the motion of lithium ions in solid-state batteries using the paddlewheel effect, which is the coordinated motion of atoms,” Waterloo explained in a press release. “The rotational motion of normally static negative ions (ie, anions) in the solid-state electrolyte framework help drive the motion of the Li+ positive ions (ie, cations) to speed up ion diffusion.”
“In fact, it turns out that the anion ‘building blocks’ that comprise the solid framework are not rigid, but undergo rotational motion,” Nazar elaborated.
Another Piece Falls Into Place
Nazar’s group worked on the paddle wheel project in collaboration with the Joint Center for Energy Storage Research. Helmed by Argonne National Laboratory, JCESR is one of the Energy Innovation Hubs established under the purview of the US Department of Energy.
The latest breakthrough is another Nazar-JCESR mashup. This one involves a new chemistry for a solid-state battery.
“This electrolyte, composed of lithium, scandium, indium and chlorine, conducts lithium ions well but electrons poorly,” JCESR explains. “This combination is essential to creating an all-solid-state battery that functions without significantly losing capacity for over a hundred cycles at high voltage (above 4 volts) and thousands of cycles at intermediate voltage.”
“The chloride nature of the electrolyte is key to its stability at operating conditions above 4 volts — meaning it is suitable for typical cathode materials that form the mainstay of today’s lithium-ion cells,” they add.
As described by JCESR, the typical solid-state battery chemistry focuses on sulfides, but that involves a complex ripple effect on battery design to prevent degradation above 2.5 volts. The conventional workaround involves coating the cathode material.
Refocusing the chemistry on a chloride electrolyte was part of the solution for Nazar group. JCESR notes that approach has been tried by other researchers, but Nazar’s group came up with a unique twist.
“The decision to swap out half of the indium for scandium based on their previous work proved to be a winner in terms of lower electronic and higher ionic conductivity,” JCESR explains.
“Chloride electrolytes have become increasingly attractive because they oxidize only high voltages, and some are chemically compatible with the best cathodes we have,” Nazar adds. “There’s been a few of them reported recently, but we designed one with distinct advantages.”
The Winding Road To The Best EV Battery Ever
Speaking of supply chains, in terms of overall sustainability of the best EV battery ever is the one that never gets used, at least not in a car. E-bikes, scooters, and other small electrified mobility devices win the day in terms of overall impact, including the use of rare earths and other raw materials.
In addition to environmental issues, supply chains are impacted by geopolitics and terror attacks, as recently underscored by the weeks-long while actions in Canada that disrupted two key NATO members — Canada and the US, too — the NATO allies face immanent war in Europe against Russia.
With that in mind, our friends over at the American Chemical Society have this to say about indium:
“Indium is a silvery-white metal named for its indigo blue line in the atomic spectrum. Relatively scarce on the Earth’s crust, indium is found with zinc sulfide ores, as well as iron, lead and copper ores.
“The vast majority (~90%) of indium is isolated as a byproduct of zinc mining. The top producers of indium are China (40%), Korea (31%), Canada (9%) and Japan (9%).
“There is no indium production in the United States. China controls between 43% and 66% of the world’s indium reserves,” ACS adds.
Interesting! From the USA’s perspective, the situation looks not much better for scandium. According to the Royal Society of Chemistry’s latest data, the largest producers are China, Russia, and Malaysia, though the US is among the top three reserve holders. For the record, China tops the RCS’s list of reserve holders, followed collectively by Russia and the Commonwealth of Independent States, which includes Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Tajikistan, Turkmenistan, Uzbekistan, and of course Ukraine .
The US Geological Survey also strikes a gloomy note regarding domestic production of scandium in the US. As of 2019, the principle source for domestic use was China, though they list some production capability at facilities in Iowa, Arizona, and Illinois.
“Although global exploration and development projects continued in anticipation of increased demand, the global scandium market remained small relative to most other metals,” USGS concluded.
Somebody better step up their game, and quick. If solid-state battery makers want to get their hands on more scandium, they’ll have to fend off competing users including that “other” electric vehicle technology, solid oxide fuel cells.
Follow me on Twitter @TinaMCasey.
Photo: This 1977 GM Electrovette powered by nickel-zinc energy storage technology would look even better with a new solid-state battery on board (photo courtesy of General Motors).
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