title: Batteries. Capturing metastable structures during high-rate cycling of LiFePO₄ nanoparticle electrodes.
abstract: The absence of a phase transformation involving substantial structural rearrangements and large volume changes is generally considered to be a key characteristic underpinning the high-rate capability of any battery electrode material. In apparent contradiction, nanoparticulate LiFePO4, a commercially important cathode material, displays exceptionally high rates, whereas its lithium-composition phase diagram indicates that it should react via a kinetically limited, two-phase nucleation and growth process. Knowledge concerning the equilibrium phases is therefore insufficient, and direct investigation of the dynamic process is required. Using time-resolved in situ x-ray powder diffraction, we reveal the existence of a continuous metastable solid solution phase during rapid lithium extraction and insertion. This nonequilibrium facile phase transformation route provides a mechanism for realizing high-rate capability of electrode materials that operate via two-phase reactions.
authors: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors: Hao
authors: H
authors: Liu
authors: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors: Fiona C
authors: FC
authors: Strobridge
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors: Olaf J
authors: OJ
authors: Borkiewicz
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors: Kamila M
authors: KM
authors: Wiaderek
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors: Karena W
authors: KW
authors: Chapman
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors: Peter J
authors: PJ
authors: Chupas
authors: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA. cpg27@cam.ac.uk.
authors: Clare P
authors: CP
authors: Grey