title: Dependence on Crystal Size of the Nanoscale Chemical Phase Distribution and Fracture in LixFePO₄.
abstract: The performance of battery electrode materials is strongly affected by inefficiencies in utilization kinetics and cycle life as well as size effects. Observations of phase transformations in these materials with high chemical and spatial resolution can elucidate the relationship between chemical processes and mechanical degradation. Soft X-ray ptychographic microscopy combined with X-ray absorption spectroscopy and electron microscopy creates a powerful suite of tools that we use to assess the chemical and morphological changes in lithium iron phosphate (LiFePO4) micro- and nanocrystals that occur upon delithiation. All sizes of partly delithiated crystals were found to contain two phases with a complex correlation between crystallographic orientation and phase distribution. However, the lattice mismatch between LiFePO4 and FePO4 led to severe fracturing on microcrystals, whereas no mechanical damage was observed in nanoplates, indicating that mechanics are a principal driver in the outstanding electrode performance of LiFePO4 nanoparticles. These results demonstrate the importance of engineering the active electrode material in next generation electrical energy storage systems, which will achieve theoretical limits of energy density and extended stability. This work establishes soft X-ray ptychographic chemical imaging as an essential tool to build comprehensive relationships between mechanics and chemistry that guide this engineering design.
authors.affiliation: †Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States.|‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|§Department of NanoEngineering, University of California, San Diego, La Jolla, California 92121, United States.|∥Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Young-Sang
authors.initials: YS
authors.lastname: Yu
authors.affiliation: †Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Chunjoong
authors.initials: C
authors.lastname: Kim
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Shapiro
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Maryam
authors.initials: M
authors.lastname: Farmand
authors.affiliation: §Department of NanoEngineering, University of California, San Diego, La Jolla, California 92121, United States.
authors.forename: Danna
authors.initials: D
authors.lastname: Qian
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Tolek
authors.initials: T
authors.lastname: Tyliszczak
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: A L David
authors.initials: AL
authors.lastname: Kilcoyne
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Rich
authors.initials: R
authors.lastname: Celestre
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Stefano
authors.initials: S
authors.lastname: Marchesini
authors.affiliation: ⊥Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: John
authors.initials: J
authors.lastname: Joseph
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Denes
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Tony
authors.initials: T
authors.lastname: Warwick
authors.affiliation: #Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Fiona C
authors.initials: FC
authors.lastname: Strobridge
authors.affiliation: #Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.|∇Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.
authors.forename: Clare P
authors.initials: CP
authors.lastname: Grey
authors.affiliation: ‡Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Howard
authors.initials: H
authors.lastname: Padmore
authors.affiliation: §Department of NanoEngineering, University of California, San Diego, La Jolla, California 92121, United States.
authors.forename: Ying Shirley
authors.initials: YS
authors.lastname: Meng
authors.affiliation: ∥Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Kostecki
authors.affiliation: †Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Jordi
authors.initials: J
authors.lastname: Cabana
keywords: High resolution chemical imaging; LiFePO4; battery materials; chemo-mechanical coupling; redox phase transformations