US Army Finds New Design For Light Cheap Lithium Battery

Researchers at Georgia Tech backed by the U.S. Army Research Laboratory have developed a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte. This opens a potential for less expensive, lighter and safer batteries that are a vital need for our warfighters.

The growing popularity of lithium-ion batteries in recent years has put a strain on the world’s supply of cobalt and nickel – two metals integral to current battery designs – and sent prices surging.

In a bid to develop alternative designs for lithium-based batteries with less reliance on those scarce metals, researchers at the Georgia Institute of Technology, funded by the Army Research Office, have developed a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte. The Army Research Office is an element of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory, the Army’s corporate research laboratory.

Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering explains, “Electrodes made from transition metal fluorides have long shown stability problems and rapid failure, leading to significant skepticism about their ability to be used in next generation batteries. But we’ve shown that when used with a solid polymer electrolyte, the metal fluorides show remarkable stability – even at higher temperatures – which could eventually lead to safer, lighter and cheaper lithium-ion batteries.”

In a typical lithium-ion battery, energy is released during the transfer of lithium ions between two electrodes – an anode and a cathode, with a cathode typically comprising lithium and transition metals such as cobalt, nickel and manganese. The ions flow between the electrodes through a liquid electrolyte.

Dr. Robert Mantz, division chief, electrochemistry at the Army Research Office said, “Professor Yushin has identified a novel approach to enable the use of iron fluoride cathodes and addresses issues with dimensional changes and parasitic side reactions to develop lithium batteries. Soldier-wearable technologies are expected to increase significantly, as will the need for power and energy sources to operate them. This research could make battery power more readily available to soldiers in a form that is safe and easily transportable.”

For the study, published in the journal Nature Materials, the research team fabricated a new type of cathode from iron fluoride active material and a solid polymer electrolyte nanocomposite. Iron fluorides have more than double the lithium capacity of traditional cobalt or nickel-based cathodes. In addition, iron is 300 times less expensive than cobalt and 150 times less costly than nickel.

To produce such a cathode, the researchers developed a process to infiltrate a solid polymer electrolyte into the prefabricated iron fluoride electrode. They then hot pressed the entire structure to increase density and reduce any voids.

Two central features of the polymer-based electrolyte are its ability to flex and accommodate the swelling of the iron fluoride while cycling and its ability to form a very stable and flexible interphase with iron fluoride. Traditionally, that swelling and massive side reactions have been key problems with using iron fluoride in previous battery designs.

Yushin describes the new battery’s potential, “Cathodes made from iron fluoride have enormous potential because of their high capacity, low material costs and very broad availability of iron. But the volume changes during cycling as well as parasitic side reactions with liquid electrolytes and other degradation issues have limited their use previously. Using a solid electrolyte with elastic properties solves many of these problems.”

The research team then tested several variations of the new solid-state batteries to analyze their performance over more than 300 cycles of charging and discharging at elevated temperature of 122° Fahrenheit, noting that they outperformed previous designs using metal fluoride even when those were kept cool at room temperatures.

The researchers found that the key to the enhanced battery performance was the solid polymer electrolyte. In previous attempts to use metal fluorides, it was believed that metallic ions migrated to the surface of the cathode and eventually dissolved into the liquid electrolyte, causing a capacity loss, particularly at elevated temperatures. In addition, metal fluorides catalyzed massive decomposition of liquid electrolytes when cells were operating above 100° Fahrenheit. However, at the connection between the solid electrolyte and the cathode, such dissolving doesn’t take place and the solid electrolyte remains remarkably stable, preventing such degradations, the researchers wrote.

Kostiantyn Turcheniuk, research scientist in Yushin’s lab and a co-author of the manuscript noted, “The polymer electrolyte we used was very common, but many other solid electrolytes and other battery or electrode architectures – such as core-shell particle morphologies – should be able to similarly dramatically mitigate or even fully prevent parasitic side reactions and attain stable performance characteristics.”

In the future, the researchers aim to develop new and improved solid electrolytes to enable fast charging and also to combine solid and liquid electrolytes in new designs that are fully compatible with conventional cell manufacturing technologies employed in large battery factories.

Mantz said, “The successful implementation of these materials into batteries would enable significant increases in battery safety and weight, thus reducing the weight of batteries required for Soldier Power.”

One more great reason to be proud of American military prowess. Plus throw in that the technology will very likely make it into civilian use really quickly. One can almost count on this technology as the military will drive on until they get the goal, come what may. But we can be sure, one way or another, there will be more battery power, in a better battery at a cheaper price. The U.S. Army is on it. Count on it.