Mesoscale Phase Distribution in Li-ion Battery Electrode Materials
May 2013 SSRL Science
Summary by Lori Ann White, SLAC Office of Communications
Figure 1a) Chemical phase map obtained by linear combination fitting of XANES data at each pixel acquired with FF TXM at Beam Line 6-2 for a particle with nominal composition of Li0.74FePO4. b) STEM image of a fully delithiated sample. Figure adapted from Boesenberg et al. 2013 |
Li-ion batteries are key devices in the effort to develop efficient chemical
energy storage from sustainable energy sources. However, any effort to optimize
battery performance requires a deeper understanding of the fundamental
mechanisms of diffusion and phase transformation in battery electrodes. In this
study supported by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center
funded by the U.S. Department of Energy, scientists from Lawrence Berkeley
National Laboratory and SSRL used full-field transmission x-ray microscopy
coupled with x-ray absorption near-edge spectroscopy (FF TXM-XANES) at SSRL
Beam Line 6-2 to visualize the chemical phase transformations occurring in
single crystals of electrode materials, such as LiFePO4,
in Li-ion technologies.
In the study, the researchers used FF TXM-XANES to produce 30 nm chemical-
and spatial-resolution maps of the distribution of chemical species involved in
the transformation, in partially delithiated, micron-sized LiFePO4
plate-like crystals. They compared the maps to morphological information
collected by scanning transmission electron microscopy (STEM), building a
mesoscale picture of the interplay between crystal microstructure and redox
reactions, and tying this complex delithiation behavior to a combination of
kinetic limitations due to macroscopic defects in the crystals and
thermodynamic effects. Stresses accompanying the delithiation process led
to the cracking of the particles due to the buildup of strain at the phase
boundaries.
The results stress the role of microstructure as a kinetic
factor during redox transformations of a particle, especially when defects are
considered, and provide clues to the design of electrode materials with
enhanced utilization and durability. It also constitutes a highly
representative example of the capabilities of TXM-XANES to study processes
relevant to energy applications.
Primary Citations
U. Boesenberg, F. Meirer, Y. Liu, A. K. Shukla, R. Dell’Anna, T. Tyliszczak, G. Chen, J. C. Andrews, T. J. Richardson, R. M. Kostecki, J. Cabana, " Mesoscale Phase Distribution in Single Particles of LiFePO4 following Lithium Deintercalation", Chem. Mater. 25, 1664 (2013)
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Contact
Jordi Cabana, Lawrence Berkeley National Laboratory
