The speed at which the ions make their way through the electrode material is also slow compared to that in electrolyte.

The current strategy to improve performance is to nanostructure the electrode particles—to make them very small, and by doing so to shorten the existing route within the electrode material. The battery performance of materials nanostructured in this way has failed to meet expectations, according to the research team.

The researchers at Delft University of Technology’s Reactor Institute Delft (RID) used neutron-diffraction research technology to investigate the particle size dependence of insertion reactions for lithiated anatase TiO₂, and discovered that when the electrode particles are scaled down, the properties of the material structure change significantly. The phase balance that is generally present in this type of material changes and even disappears completely if the electrode sections become small enough.

Based on these findings, the researchers can predict how the nanostructures will affect the performance of the Li-ion batteries. They have concluded that the performance of nanostructured electrode materials in Li-ion batteries is largely dependent on the material and the exact particle size. At a more general level, their findings are important for applications in which small ions diffuse into nanocrystals, such as hydrogen storage and the formation of alloys.

Resources:

• “Large Impact of Particle Size on Insertion Reactions. A Case for Anatase Li_xTiO₂”; Marnix Wagemaker, Wouter J. H. Borghols, and Fokko M. Mulder; J. Am. Chem. Soc.; 2007