NEW CATHODE COULD TRIPLE ENERGY DENSITY
A collaboration led by scientists at the University of Maryland (UMD), the US Department of Energy’s (DOE) Brookhaven National Laboratory, and the US Army Research Lab have developedand studied a new cathode material - a modified and engineered form of iron trifluoride (FeF3) - that could triple the energy density of lithium-ion battery electrodes. Their open-access paper is published in Nature Communications.
The materials normally used in lithium-ion batteries are based on intercalation chemistry. While efficient, this type of chemical reaction only transfers a single electron, so the cathode capacity is limited, explains Enyuan Hu, a chemist at Brookhaven and one of the lead authors of the paper. However, some compounds like FeF3 are capable of transferring multiple electrons through a more complex reaction mechanism, called a conversion reaction.
Despite FeF3’s potential to increase cathode capacity, the compound has not historically worked well in lithium-ion batteries due to three complications with its conversion reaction: poor energy efficiency (hysteresis); a slow reaction rate; and side reactions that can cause poor cycling life.
To overcome these challenges, the team added cobalt and oxygen atoms to FeF3 nanorods through a process called chemical substitution. This allowed the scientists to manipulate the reaction pathway and make it more reversible.