The geared-up US Army soldier of the 21st century packs about 25 pounds of batteries on a typical mission, so it’s no surprise that the Army continually obsesses over improving its energy storage resources. In the latest twist, the Army is giving lithium-ion batteries another chance, only this time with a new liquefied gas electrolyte.
Next-Generation Energy Storage: Why The Army Wants To Make Liquefied Gas Electrolytes Happen
Conventional lithium-ion batteries deploy a liquid electrolyte, in which a lithium salt is dissolved by a solvent. Normally it’s a worry-free environment, despite the presence of the solvent. However, a defective or punctured battery can become a fire hazard.
Lithium-ion batteries are ubiquitous throughout modern life, and that thing about puncturing is not a concern for most people in most situations. However, it is a particular hazard for soldiers and their equipment, along with crushing and other potential impacts that may be incurred during field missions, which explains why the Army is keen on identifying the next generation of better, safer lithium-ion batteries.
The US Department of Defense took a big step into the future of lithium-ion energy storage a few years ago, when it lent an assist to help the Illinois startup NanoGraf develop a new silicon anode formula, aimed at reducing the weight and improving the performance of lithium-ion batteries.
Then came a $10 million award from the Army to help NanoGraf get a factory for its silicon formula off the ground in Chicago. Now the Army is following up with another $550,000 in funding, to hook up NanoGraf’s 3.8 Ah 18650 silicon anode battery cell with a liquified gas electrolyte developed by the California firm South 8 Technologies.
The six-month project will put the new battery through its paces in a series of temperature and nail penetration tests.
“Successful completion of the testing will validate the extreme cold temperature performance of the cell and maintain existing capacity and cycle life, allowing the cell to operate down to -60 degrees, and up to +60 celsius and pass the safety test,” NanoGraf explains.
What’s So Great About Liquified Gas Electrolytes?
The Army energy storage project follows an award of $3.152 million to South 8 from ARPA-E, the cutting edge funding office of the Energy Department, as part of a broader program to push the envelope on battery performance for electric vehicles. “The LiGas electrolyte uses non-toxic and non-corrosive gases that are liquefied under moderate pressures and can be contained in standard cylindrical cell cans,” explains ARPA-E.
“The technology has demonstrated excellent performance in conventional graphite/lithium-nickel-manganese-cobalt-oxide cells and offers many opportunities for cost reduction,” ARPE-E adds.
ARPA-E made the award in January, and the plan is for South 8 to work with a top tier EV stakeholder over the next three years to bring liquefied gas energy into the mainstream.
Apparently the Army is not waiting for the grass to grow, and for good reason. If all goes according to plan, the NanoGraf—South 8 mashup will result in a significant improvement in performance and soldier safety on missions.
“The liquefied gas electrolyte improves safety, increases energy density, achieves all-weather performance, enables fast-charge capability and reduces costs while also being compatible with existing lithium-ion cell production or gigafactory manufacturing processes and supply chains,” South 8 enthuses. “LiGas® makes lithium-ion batteries safer by removing the risk of thermal runaway, since the harmless liquefied gas can be safely vented.”
Where Did This New Energy Storage Formula Come From?
Liquefied gas electrolytes are new to the CleanTechnica radar, so we have some catching up to do.
One key development in the field popped up in 2017, from the lab of Shirley Meng at the University of California-San Diego Jacobs School of Engineering. Meng, who also serves as an official advisor to South 8, is credited as senior author on a study of liquefied gas electrolytes published in the journal Science on June 15, 2017, under the title, “Liquefied gas electrolytes for electrochemical energy storage devices.”
The authors explain that the anode and cathode in energy storage devices are separated to prevent short circuits, and that is true for both liquid and solid electrolytes. Building on previous work, they demonstrate that a similar separation can occur in fluorinated hydrocarbon gases that are liquefied under pressure. “Although a number of potential solvents were explored, the present study focuses on the use of hydrofluorocarbons, which are nontoxic and have relatively strong chemical bonds, allowing for a wide electrochemical window,” they note.
“The electrolytes show excellent stability in both batteries and capacitors, particularly at low temperatures,” they conclude.
Next Steps For Advanced Energy Storage & The US Army
Last summer, a team based at the Meng lab published a new study in the journal Nature Energy, in which they outlined “a route to sustainable, temperature-resilient lithium-metal batteries with fire-extinguishing properties that maintain state-of-the-art electrochemical performance.”
You can get all the details from Nature Energy under the title, “Fire-extinguishing, recyclable liquefied gas electrolytes for temperature-resilient lithium-metal batteries.” The Jacobs School blog also offers some interesting background on how the new study came about from a discussion between PhD student Yijie Yin and another graduate student, Yangyuchen Yang, who co-share first author credit on the study.
The discussion centered around a major defficiency in the electrolyte resulting from the 2017 work: “… the LGE electrolyte is not yet ‘perfect,’ because the saturated vapor pressure of the molecules used is high, and like most electrolytes, it is still flammable, which makes the safety and environmental protection of the system irrational,” the Jacobs blog poster explained.
In the search for a non-flammable solution, the researchers settled on two gas molecules that are the main ingredients in some types of fire extinguishers, those being 1,1,1,2 tetrafluoroethane and pentafluoroethane.
Meanwhile, new portable batteries are just one aspect of the Army’s search for the energy storage solutions of the future. The Army is also investing in new forms of large scale, long duration energy storage systems to provide for energy security at its facilities. That includes flow batteries, too.
Electric vehicles and EV batteries are another focus of attention from the US Army and the Department of Defense. They are casting a wide net, including legacy automakers with EV ambitions like GM as well as startups.
Among those in the running is Canoo, maker of an odd-looking lozenge-shaped but versatile electric platform, and Lucid Motors, which has reportedly signed onto a Defense Department initiative aimed at establishing a standard, interchangeable platform for EV batteries.
Find me on Spoutible: @TinaMCasey or LinkedIn @TinaMCasey or Mastodon @Casey or Post: @tinamcasey
Photo (cropped): The US Army is seeking improved portable energy storage systems to power electronic devices for Soldiers on missions (courtesy of US Army).
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