Army Team Reports New Cathode Chemistry

By Battery Power Staff

May 13, 2019 | Researchers at the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory, the Army’s corporate research laboratory known as ARL, and the University of Maryland have identified a new cathode chemistry. The work was published last week in Nature (DOI: 10.1038/s41586-019-1175-6).

The team reports a halogen conversion–intercalation chemistry in graphite that produces composite electrodes with a capacity of 243 milliampere-hours per gram (for the total weight of the electrode) at an average potential of 4.2 volts versus Li/Li+.

The new chemistry could significantly increase the lithium-ion battery energy density while preserving safety due to the aqueous nature of the electrolyte, said Dr. Kang Xu, an ARL fellow and senior research chemist in a statement. “Such a high energy, safe and potentially flexible new battery will likely give the Soldiers what they need on the battlefield: reliable high energy source with robust tolerance against abuse,” he added. “It is expected to significantly enhance the mobility and lethality of the Soldier while unburdening logistics requirements.”

Building on their previous discoveries of the intrinsically safe “water-in-salt electrolytes (WiSE)” and the technique to stabilize graphite anodes in WiSE, the team’s development of the novel cathode chemistry further extends available energy for aqueous batteries to a previously unachievable level.

The researchers, led by Chunsheng Wang, R.F. and F.R. Wright Distinguished Chair Professor in UMD’s Department of Chemical & Biomolecular Engineering and Department of Chemistry and Biochemistry; Kang Xu, ARL Fellow, and Oleg Borodin, ARL scientist, developed the battery into a testable stage with button cell configuration that is typically used as a test vehicle in research labs, and characterized in details the conversion – intercalation chemistry that is responsible for the increased energy density. More research is needed to scale it up into a practical large-scale battery, Kang said.

“This new cathode chemistry… combines both high energy density of non-aqueous systems and high safety of aqueous systems,” said the first author of the paper, Chongyin Yang, an assistant research scientist in the Department of Chemical and Biomolecular Engineering at College Park.

The ARL researchers are particularly interested in the chemistry’s impact for soldiers. Soldiers often carry 15-25 pounds of batteries and decreasing that weight would be greatly beneficial. But beyond portable batteries for soldiers, the aqueous battery chemistry could also be used in applications that involve large energies at kilowatt or megawatt levels or where battery safety and toxicity are primary concerns, including non-flammable batteries for airplanes, naval vessels, or spaceships, or in civilian applications for portable electronics, electric vehicles and large-scale grid storage.

In a quote included in the paper’s press release, Jeff Dahn, Dalhousie University in Canada, called the chemistry, “the most creative new battery chemistry I have seen in at least 10 years. The fact that the LiCl and LiBr reversibly convert and form halogen intercalated graphite is truly incredible. The team has demonstrated encouraging reversibility for 150 cycles and have shown that high energy densities should be attainable in 4-volt cells that contain no transition metals and no non-aqueous solvents. It remains to be seen if a practical long-lived commercial cell can be developed, but I am very excited by this research.”