Effect of surface energies and nano-particle size distribution
on open circuit voltage of Li-electrodes
A. Van der Ven1*, M. Wagemaker2
1Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, MI,
48109
2Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft
University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands
Surface free energies become increasingly important in affecting voltage profiles and solubility limits of first-order phase transformations as electrode particles approach nanometer dimensions. Here, we show that the presence of a distribution in crystallite sizes at nanometer dimensions (<100 nm) can qualitatively modify the voltage profile around a first-order phase transformation. The plateau voltage of a first-order phase transformation depends on crystallite dimensions and a distribution of crystallite sizes leads to a spectrum of transformation voltages that produces a sloping voltage profile similar to that of a solid solution. This suggests that the voltage profile of a collection of nano-electrode particles can be tailored not only by modifying chemistry, but also with surface treatment and through control of particle size distribution.
Figure: (a) Four log-logistic distributions of spherical crystallite radii; (b) voltage profiles for the four distributions assuming ∆σ=σβ−σα=0.5 J/m2; (c)
voltage profiles for various values of ∆σ=σβ−σα using distribution II having a median radius of 30nm.
