Effect of Fluoride Doping on Lithium Diffusivity in Layered Molybdenum Oxide

Allison Wustrow, Justin C. Hancock, Jared T. Incorvati, John T. Vaughey, Kenneth R. Poeppelmeier

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The effects of cation doping on cathode performance has been extensively studied; however, the field of anion doping has historically received much less attention. Fluoride doping can greatly increase the initial diffusivity of the layered MoO3 system. The first discharge cycle of the layered α-MoO3 and MoO2.8F0.2 phases were investigated and compared using the galvanostatic intermittent titration technique (GITT) in a lithium ion cell. The analysis revealed that a slight reduction of the oxide by fluoride doping to form a fluorobronze (MoO2.8F0.2) eliminated a slow electrochemical process observed in α-MoO3. Galvanostatic cycling studies show that while α-MoO3 has a higher initial capacity, it exhibits a first cycle Coulombic efficiency of only 86% with rapid capacity fade which has been associated with lithium trapping within the MoO3 layer. In contrast, the Li+ intercalation process in the fluorobronze was found to have a 94% Coulombic efficiency on the first cycle. By the third cycle Coulombic efficiencies greater than 99% were observed for five cycles. A thorough investigation of the synthesis of MoO2.8F0.2 is also presented. Under mild hydrothermal conditions, the fluorination of α-MoO3 to form MoO2.8F0.2 is topotactic, while a competing reaction in solution forms MoO2.4F0.6 (ReO3 structure). Methods to prevent the solution phase reaction from occurring are discussed.

Original languageEnglish
Pages (from-to)2080-2086
Number of pages7
JournalACS Applied Energy Materials
Volume2
Issue number3
DOIs
Publication statusPublished - Mar 25 2019

Keywords

  • batteries
  • fluoride doping
  • galvanostatic intermittent titration technique
  • lithium intercalation
  • molybdenum oxide

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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