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Title: Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4

Abstract

The delithiation mechanisms occurring within the olivine-type class of cathode materials for Li-ion batteries have received considerable attention because of the good capacity retention at high rates for LiFePO4. A comprehensive mechanistic study of the (de)lithiation reactions that occur when the substituted olivine-type cathode materials LiFe$$_x$$Co1–$$_x$$PO4 ($x$ = 0, 0.05, 0.125, 0.25, 0.5, 0.75, 0.875, 0.95, 1) are electrochemically cycled is reported here using in situ X-ray diffraction (XRD) data and supporting ex situ 31P NMR spectra. On the first charge, two intermediate phases are observed and identified: Li1–$$_x$$(Fe3+)$$_x$$(Co2+)1–$$_x$$PO4 for $0 < x < 1$ (i.e., after oxidation of Fe2+ to Fe3+) and Li2/3Fe$$_x$$Co1–$$_x$$PO4 for $0 ≤ x ≤ 0.5$ ($i.e.$, the Co-majority materials). For the Fe-rich materials, we study how nonequilibrium, single-phase mechanisms that occur discretely in single particles, as observed for LiFePO4 at high rates, are affected by Co substitution. In the Co-majority materials, a two-phase mechanism with a coherent interface is observed, as was seen in LiCoPO4, and we discuss how it is manifested in the XRD patterns. We then compare the nonequilibrium, single-phase mechanism with the bulk single-phase and coherent interface two-phase mechanisms. Despite the apparent differences between these mechanisms, we discuss how they are related and interconverted as a function of Fe/Co substitution and the potential implications for the electrochemistry of this system.

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [2];  [3]
  1. Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, Cambridgeshire CB2 1EW, U.K.
  2. X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
  3. Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, Cambridgeshire CB2 1EW, U.K., Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, United States
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Northeastern Center for Chemical Energy Storage (NECCES)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1257503
Alternate Identifier(s):
OSTI ID: 1371400
Grant/Contract Number:  
SC0001294
Resource Type:
Published Article
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Name: Chemistry of Materials Journal Volume: 28 Journal Issue: 11; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; energy storage (including batteries and capacitors); defects; charge transport; materials and chemistry by design; synthesis (novel materials)

Citation Formats

Strobridge, Fiona C., Liu, Hao, Leskes, Michal, Borkiewicz, Olaf J., Wiaderek, Kamila M., Chupas, Peter J., Chapman, Karena W., and Grey, Clare P. Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4. United States: N. p., 2016. Web. doi:10.1021/acs.chemmater.6b00319.
Strobridge, Fiona C., Liu, Hao, Leskes, Michal, Borkiewicz, Olaf J., Wiaderek, Kamila M., Chupas, Peter J., Chapman, Karena W., & Grey, Clare P. Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4. United States. doi:10.1021/acs.chemmater.6b00319.
Strobridge, Fiona C., Liu, Hao, Leskes, Michal, Borkiewicz, Olaf J., Wiaderek, Kamila M., Chupas, Peter J., Chapman, Karena W., and Grey, Clare P. Thu . "Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4". United States. doi:10.1021/acs.chemmater.6b00319.
@article{osti_1257503,
title = {Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4},
author = {Strobridge, Fiona C. and Liu, Hao and Leskes, Michal and Borkiewicz, Olaf J. and Wiaderek, Kamila M. and Chupas, Peter J. and Chapman, Karena W. and Grey, Clare P.},
abstractNote = {The delithiation mechanisms occurring within the olivine-type class of cathode materials for Li-ion batteries have received considerable attention because of the good capacity retention at high rates for LiFePO4. A comprehensive mechanistic study of the (de)lithiation reactions that occur when the substituted olivine-type cathode materials LiFe$_x$Co1–$_x$PO4 ($x$ = 0, 0.05, 0.125, 0.25, 0.5, 0.75, 0.875, 0.95, 1) are electrochemically cycled is reported here using in situ X-ray diffraction (XRD) data and supporting ex situ 31P NMR spectra. On the first charge, two intermediate phases are observed and identified: Li1–$_x$(Fe3+)$_x$(Co2+)1–$_x$PO4 for $0 < x < 1$ (i.e., after oxidation of Fe2+ to Fe3+) and Li2/3Fe$_x$Co1–$_x$PO4 for $0 ≤ x ≤ 0.5$ ($i.e.$, the Co-majority materials). For the Fe-rich materials, we study how nonequilibrium, single-phase mechanisms that occur discretely in single particles, as observed for LiFePO4 at high rates, are affected by Co substitution. In the Co-majority materials, a two-phase mechanism with a coherent interface is observed, as was seen in LiCoPO4, and we discuss how it is manifested in the XRD patterns. We then compare the nonequilibrium, single-phase mechanism with the bulk single-phase and coherent interface two-phase mechanisms. Despite the apparent differences between these mechanisms, we discuss how they are related and interconverted as a function of Fe/Co substitution and the potential implications for the electrochemistry of this system.},
doi = {10.1021/acs.chemmater.6b00319},
journal = {Chemistry of Materials},
number = 11,
volume = 28,
place = {United States},
year = {2016},
month = {5}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acs.chemmater.6b00319

Citation Metrics:
Cited by: 9 works
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Works referencing / citing this record:

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