NMR monitoring of electrode/electrolyte interphase in the case of air-exposed and carbon coated LiFePO4

M. Cuisinier, N. Dupré, P. Moreau, D. Guyomard

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11 Citations (Scopus)

Abstract

Degradation of the electrochemical performance of LiFePO4 upon air exposure, assigned to a corrosion-type aging mechanism, implies the incorporation of hydroxyl groups and the formation of an amorphous tavorite-like phase at the surface. Using a carbon coating provides an efficient protection from this detrimental process but also modifies the surface in contact with the electrolyte. The formation and evolution of electrode/electrolyte interphases forming on both air-aged and carbon coated LiFePO4 are discussed based on combined quantitative 7Li, 19F MAS NMR, EIS and EELS measurements. Concerning the air-aged LiFePO4, the electrode/electrolyte interactions are dominated by the dissolution of the active material and an exacerbated reaction of incorporated hydroxyl groups with the electrolyte salt, resulting in a LiF rich interphase. This dissolution of the outer part of active material particles is accompanied by the departure of the previously formed interphase and a new interphase is then formed on a newly exposed surface. The resistive LiF rich interphase passivates the active material particles during cycling, forming a resistive film, hindering both Li ion transfer and material corrosion. Cellulose acetate based carbon coating prevents air-aging but yields to an accumulation of organic lithiated species, allowing Li transfer and maintaining good electrochemical performance.

Original languageEnglish
Pages (from-to)682-690
Number of pages9
JournalJournal of Power Sources
Volume243
DOIs
Publication statusPublished - 15 Jul 2013

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Keywords

  • Interface
  • Lithium batteries
  • MAS NMR
  • Positive electrode

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering

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