Dynamic solubility limits in nanosized olivine LiFePO4.

Because of its stability, nanosized olivine LiFePO(4) opens the door toward high-power Li-ion battery technology for large-scale applications as required for plug-in hybrid vehicles. Here, we reveal that the thermodynamics of first-order phase transitions in nanoinsertion materials is distinctly different from bulk materials as demonstrated by the decreasing miscibility gap that appears to be strongly dependent on the overall composition in LiFePO(4). In contrast to our common thermodynamic knowledge, that dictates solubility limits to be independent of the overall composition, combined neutron and X-ray diffraction reveals strongly varying solubility limits below particle sizes of 35 nm.

Direct observation of space charge induced hydrogen ion insertion in nanoscale anatase TiO2.

Space charge induced 2H+ densities up to 2H+ (0.17)TiO2 are observed directly using neutron diffraction on two different nanoscale particle sizes of anatase TiO2 immersed in sulfuric acid, and consistent with experimental evidence modelling shows that these ions show rapid self diffusion.

Large impact of particle size on insertion reactions. A case for anatase Li(x)TiO2.

Insertion reactions are of key importance for Li ion and hydrogen storage materials and energy storage devices. The particle size dependence of insertion reactions has been investigated for lithiated anatase TiO2, revealing progressively increasing Li capacity and Li-ion solubility for decreasing particle sizes, strongly deviating from the expected Li-rich and Li-poor phase separation as occurs in the bulk material. The phase diagram alters significantly, changing the materials properties already at sizes as large as 40 nm.

The influence of size on phase morphology and Li-ion mobility in nanosized lithiated anatase TiO2.

Sustainable energy storage in the form of Li-ion batteries requires new and advanced materials in particular with a higher power density. Nanostructuring appears to be a promising strategy, in which the higher power density in nanosized materials is related to the dramatically shortened Li-ion diffusion paths. However, nanosizing materials also changes intrinsic material properties, which influence both ionic and electronic conductivity.