title: Direct view on the phase evolution in individual LiFePO4 nanoparticles during Li-ion battery cycling.
abstract: Phase transitions in Li-ion electrode materials during (dis)charge are decisive for battery performance, limiting high-rate capabilities and playing a crucial role in the cycle life of Li-ion batteries. However, the difficulty to probe the phase nucleation and growth in individual grains is hindering fundamental understanding and progress. Here we use synchrotron microbeam diffraction to disclose the cycling rate-dependent phase transition mechanism within individual particles of LiFePO4, a key Li-ion electrode material. At low (dis)charge rates well-defined nanometer thin plate-shaped domains co-exist and transform much slower and concurrent as compared with the commonly assumed mosaic transformation mechanism. As the (dis)charge rate increases phase boundaries become diffuse speeding up the transformation rates of individual grains. Direct observation of the transformation of individual grains reveals that local current densities significantly differ from what has previously been assumed, giving new insights in the working of Li-ion battery electrodes and their potential improvements.
authors.affiliation: Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
authors.forename: Xiaoyu
authors.identifier: http://orcid.org/0000-0001-5648-6829
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: van Hulzen
authors.affiliation: Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
authors.forename: Deepak P
authors.initials: DP
authors.lastname: Singh
authors.affiliation: European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220, 38043 Grenoble Cedex, France.
authors.forename: Alex
authors.initials: A
authors.lastname: Brownrigg
authors.affiliation: European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220, 38043 Grenoble Cedex, France.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Wright
authors.affiliation: Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
authors.forename: Niels H
authors.initials: NH
authors.lastname: van Dijk
authors.affiliation: Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
authors.forename: Marnix
authors.initials: M
authors.lastname: Wagemaker