New Electrode Made From Iron Oxide Nanoparticles Boosts Battery Capacity

An inexpensive, new electrode made from iron oxide nanoparticles has the potential to notably extend the potential range of electric vehicles, according to the researchers that developed it.

Along with being inexpensive, and capable of storing higher charge densities than the conventional electrodes used in lithium-ion batteries, the new electrode is also well suited for large-scale manufacturing.

The iron oxide nanoparticles in question replace the graphite that is usually used as the anode — iron oxides have a considerably higher charging capacity than graphite, but are somewhat slower to charge. And there is also the issue of the lithium ions that migrate into the material damaging the anode after only a few charging cycles. The new anode addresses both of these issues.

The A*STAR Institute of Materials Research and Engineering has more:

The researchers made 5-nanometer-wide particles of an iron oxide known as α-Fe2O3, simply by heating iron nitrate in water. They mixed the particles with a dust called carbon black, bound them together with polyvinylidene fluoride and coated the mixture onto copper foil to make their anodes.

During the first round of charging and discharging, the anodes showed an efficiency of 75-78%, depending on the current density used. After ten more cycles, however, the efficiency improved to 98%, almost as high as commercial lithium-ion batteries. Research by other teams suggests that during the first few cycles, the iron oxide nanoparticles are broken down until they reach an optimum size.

After 230 cycles the anode’s efficiency remained at 97%, with a capacity of 1,009 milliamp hours per gram (mA h g−1 ) — almost three times greater than commercial graphite anodes. The material experienced none of the degradation problems that have plagued other iron oxide anodes.

The researchers are now focusing on optimizing the nanoparticle synthesis, and also on increasing the efficiency of the anode’s first few charging cycles.

The new anode was developed by Zhaolin Liu of the A*STAR Institute of Materials Research and Engineering, Singapore, and Aishui Yu of Fudan University, China — along with others.