V. Focused Fundamental Research - EERE - U.S. Department of ...

Sastry – U. Michigan
V.E.2 Thermo-electrochemistry, Capacity Degradation and Mechanics with SEI Layer (U. Michigan)
Table V - 5: Change in surface atomic concentration of each element
Table V - 6 shows changes in element quantities for
different temperatures resulting from XPS measurements.
The quantity of phosphorus was significantly increased as
the temperature increased. This was due to higher
decomposition of the LiPF 6 at high temperatures. Also, a
relatively large amount of oxygen and lithium was
observed at high temperatures, indicating that more SEI
layer components such as lithium alkyl carbonate, Li 2 CO 3 ,
and LiF formed at high temperatures.
Table V - 6: SEI element quantity change
Conclusions and Future Directions
A multiphysics model of thermo-electrochemistry
using self-assembled structure has demonstrated the
differences in predicted reaction current density from the
pseudo-2D model. Also, volume-averaging theory was
applied for the fluxes and perturbations to the micro
simulations in order to calculate effective diffusivities and
conductivities of the aggregated system. The developed
model will be extended to the linking of macro and microscale
simulation. Capacity and power fade due to the SEI
layer have been modeled by considering film resistance
and the double-layer charging current. The simulation has
revealed that capacity fade is accelerated as film resistance
increases. Also, the stress evolution due to misfit between
the phases inside the particle and SEI layer has been
demonstrated. This result will be used to evaluate the
mechanical stability of the SEI layer and capacity fade due
to mechanical failure. Several experimental techniques (ex
situ and/or in situ) were applied to validate the SEI layer
formation model and characterize the SEI layer; these
included film resistance change due to the SEI layer and
SEI layer component change. These experimental
techniques will in the future be applied with new
techniques such as AFM-based nanoindentation to
measure Young's modulus of the surface layer.
FY 2011 Publications/Presentations
1. 2011 DOE Annual Peer Review Meeting Presentation.
2. Gupta, A., Seo, J.H., Zhang, X., Du, W., and Sastry,
A.M., 2011, "Effective transport properties of
LiMn2O4 electrode via particle-scale modeling,"
Journal of the Electrochemical Society, v. 158 (5), pp.
A487-497.
3. Seo, J.H., Chung, M.D., Park, M., Han, S.W., Zhang,
X., and Sastry, A.M., 2011, "Generation of realistic
particle structures and simulations of internal stress: a
numerical/AFM study of LiMn2O4 particles," Journal
of the Electrochemical Society, v. 158 (4), pp. A434­
442.
4. Chung, M.D., Seo, J.H., Zhang, X., and Sastry, A.M.,
2011, "Implementing realistic geometry and measured
diffusion coefficients into single particle electrode
modeling based on experiments with single LiMn2O4
spinel particles," Journal of the Electrochemical
Society, v. 158 (4), pp. A371-378.
5. Park, J., Seo, J.H., Plett, G., Lu, W., and Sastry, A.M.,
2011, "Numerical simulation of the effect of the
dissolution of LiMn2O4 particles on Li-ion battery
performance," Electrochemical and Solid-State
Letters, v. 14 (2), pp. A14-18.
6. Park, J., Lu, W., and Sastry, A.M., 2011, "Numerical
simulation of stress evolution in lithium manganese
dioxide particles due to coupled phase transition and
intercalation," Journal of the Electrochemical Society,
v. 158 (2), pp. A201-206.
7. M. Zhu, J. Park, and , “Particle Interaction and
Aggregation in Cathode Material of Li-Ion Batteries:
A Numerical Study”, 2011, J. Electrochem. Soc. 158
A1155.
FY 2011 Annual Progress Report 635 Energy Storage R&D