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Title: Changes in Electronic Structure upon Li Deintercalation from LiCoPO 4 Derivatives

Abstract

On the path toward the design of Li-ion batteries with increased energy densities, efforts are focused on the development of positive electrodes that can maximize the voltage of the full cell. However, the development of novel materials that operate at high voltage, while also showing high efficiency and meeting strict safety standards, is an ongoing challenge. LiCoPO 4 is being explored as a possible candidate, as the Co 2+/3+ redox couple operates at 4.8 V versus Li +/Li 0. The presence of phosphate groups is typically expected to stabilize the compound against oxygen loss, yet the changes in Co-O bonding upon Li extraction have not been ascertained. In addition, LiCoPO 4 is riddled with problems relating to poor transport and strain in the crystal structure of the delithiated phase, which handicap its use as a high-voltage electrode. In this work, substituting ions to generate Li 1.025Co 0.84Fe 0.10Cr 0.05Si 0.01(PO 4) 1.025 is found to stabilize both the electronic structure and crystal structure and, therefore, substantially improve the ability to fully utilize the redox capacity of the material. A thorough study by spectroscopic tools, combined with computations of the electronic structure, was used to probe changes in chemical bonding. Themore » measurements revealed the existence of redox gradients between surface and bulk that are common in other materials that react at high potential. Lastly, the study offers a comprehensive understanding of the fundamental reactions in LiCoPO 4-type frameworks, while further demonstrating that ion substitution is an effective tool for improving their performance.« less

Authors:
 [1];  [2];  [2];  [2];  [3];  [4];  [1];  [2];  [2]; ORCiD logo [1]
  1. Univ. of Illinois at Chicago, Chicago, IL (United States)
  2. U.S. Army Research Lab., Adelphi, MD (United States)
  3. Argonne National Lab. (ANL), Lemont, IL (United States)
  4. Naval Research Lab., Washington, D.C. (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
U.S. Army Research Laboratory; US Department of the Navy, Office of Naval Research (ONR); USDOE
OSTI Identifier:
1464630
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 30; Journal Issue: 6; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Lapping, Jacob G., Delp, Samuel A., Allen, Joshua L., Allen, Jan L., Freeland, John W., Johannes, Michelle D., Hu, Linhua, Tran, Dat T., Jow, T. Richard, and Cabana, Jordi. Changes in Electronic Structure upon Li Deintercalation from LiCoPO4 Derivatives. United States: N. p., 2018. Web. doi:10.1021/acs.chemmater.7b04739.
Lapping, Jacob G., Delp, Samuel A., Allen, Joshua L., Allen, Jan L., Freeland, John W., Johannes, Michelle D., Hu, Linhua, Tran, Dat T., Jow, T. Richard, & Cabana, Jordi. Changes in Electronic Structure upon Li Deintercalation from LiCoPO4 Derivatives. United States. doi:10.1021/acs.chemmater.7b04739.
Lapping, Jacob G., Delp, Samuel A., Allen, Joshua L., Allen, Jan L., Freeland, John W., Johannes, Michelle D., Hu, Linhua, Tran, Dat T., Jow, T. Richard, and Cabana, Jordi. Fri . "Changes in Electronic Structure upon Li Deintercalation from LiCoPO4 Derivatives". United States. doi:10.1021/acs.chemmater.7b04739. https://www.osti.gov/servlets/purl/1464630.
@article{osti_1464630,
title = {Changes in Electronic Structure upon Li Deintercalation from LiCoPO4 Derivatives},
author = {Lapping, Jacob G. and Delp, Samuel A. and Allen, Joshua L. and Allen, Jan L. and Freeland, John W. and Johannes, Michelle D. and Hu, Linhua and Tran, Dat T. and Jow, T. Richard and Cabana, Jordi},
abstractNote = {On the path toward the design of Li-ion batteries with increased energy densities, efforts are focused on the development of positive electrodes that can maximize the voltage of the full cell. However, the development of novel materials that operate at high voltage, while also showing high efficiency and meeting strict safety standards, is an ongoing challenge. LiCoPO4 is being explored as a possible candidate, as the Co2+/3+ redox couple operates at 4.8 V versus Li+/Li0. The presence of phosphate groups is typically expected to stabilize the compound against oxygen loss, yet the changes in Co-O bonding upon Li extraction have not been ascertained. In addition, LiCoPO4 is riddled with problems relating to poor transport and strain in the crystal structure of the delithiated phase, which handicap its use as a high-voltage electrode. In this work, substituting ions to generate Li1.025Co0.84Fe0.10Cr0.05Si0.01(PO4)1.025 is found to stabilize both the electronic structure and crystal structure and, therefore, substantially improve the ability to fully utilize the redox capacity of the material. A thorough study by spectroscopic tools, combined with computations of the electronic structure, was used to probe changes in chemical bonding. The measurements revealed the existence of redox gradients between surface and bulk that are common in other materials that react at high potential. Lastly, the study offers a comprehensive understanding of the fundamental reactions in LiCoPO4-type frameworks, while further demonstrating that ion substitution is an effective tool for improving their performance.},
doi = {10.1021/acs.chemmater.7b04739},
journal = {Chemistry of Materials},
number = 6,
volume = 30,
place = {United States},
year = {2018},
month = {2}
}

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