Accommodating High Transformation Strains in Battery Electrodes via the Formation of Nanoscale Intermediate Phases: Operando Investigation of Olivine NaFePO4 [Accommodation of High Transformation Strain in Battery Electrodes via Formation of Nanoscale Intermediate Phases: Operando Structure Investigation of Olivine Sodium Iron Phosphate]
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Southern Denmark (Denmark)
- Rice Univ., Houston, TX (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States)
Virtually all intercalation compounds used as battery electrodes exhibit significant changes in unit cell volume during use. NaxFePO4 (0 < x < 1, NFP) olivine, of interest as a cathode for sodium-ion batteries, is a model for topotactic, high strain systems as it exhibits one of the largest discontinuous volume changes (~17% by volume) during its first-order transition between two otherwise isostructural phases. Using synchrotron radiation powder X-ray diffraction (PXD) and pair distribution function (PDF) analysis, we discover a new strain-accommodation mechanism wherein a third, <10 nm scale nanocrystalline phase forms to buffer the large lattice mismatch between primary phases. The new phase has a and b lattice parameters matching one crystalline endmember phase and c lattice parameter matching the other, and is not detectable by powder diffraction alone. Finally, we suggest that this strain-accommodation mechanism may apply to systems with large transformation strains but in which true “amorphization” does not occur.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1373931
- Journal Information:
- Nano Letters, Vol. 17, Issue 3; ISSN 1530-6984
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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