Because of their high energy-storage density, materials such as metal oxides, sulfides, and fluorides are promising electrode materials for lithium-ion batteries in electric vehicles and other technologies.
Because of their high energy-storage density, materials such as metal oxides, sulfides, and fluorides are promising electrode materials for lithium-ion batteries in electric vehicles and other technologies. However, their capacity fades very rapidly. Now, scientists studying an electrode made of an inexpensive and nontoxic iron-oxide material called magnetite have proposed a scenario—described in the May 20 online issue of Nature Communications—that explains why.
“Magnetite, among other conversion-type electrode materials (i.e., materials that get converted into entirely new products when they react with lithium), can store more energy than today’s electrode materials because they can accommodate more lithium ions,” said study lead Dong Su, leader of the Electron Microscopy Group at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory. “However, the capacity of these materials degrades very quickly and is dependent on the current density. For example, our electrochemical testing of magnetite revealed that its capacity drops very quickly within the first 10 high-rate charge and discharge cycles.”
Read more at DOE/Brookhaven National Laboratory
Image: The fade in battery capacity is due to the formation and thickening of internal and surface passivation layers during charge and discharge cycles. For the electrochemical reactions to occur, lithium ions (Li+) and electrons (e-) must travel through all these layers to reach active nanoparticles (NPs) at the electrode. Top: Fe3O4 (iron oxide) sample after three cycles. Bottom: Fe3O4 sample after 100 cycles. The development of kinetic barriers during long-term cycling limits electrochemical reactions to such an extent that no reduction-oxidation reactions occur at the electrode materials after 100 cycles. CREDIT: DOE/Brookhaven National Laboratory
