Symmetric lithium-ion cell based on lithium vanadium fluorophosphate with ionic liquid electrolyte

Larisa S. Plashnitsa, Eiji Kobayashi, Shigeto Okada, Jun Ichi Yamaki

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Abstract

Lithium vanadium fluorophosphate, LiVPO4F, was utilized as both cathode and anode for fabrication of a symmetric lithium-ion LiVPO 4F//LiVPO4F cell. The electrochemical evolution of the LiVPO4F//LiVPO4F cell with the commonly used organic electrolyte LiPF6/EC-DMC has shown that this cell works as a secondary battery, but exhibits poor durability at room temperature and absolutely does not work at increased operating temperatures. To improve the performance and safety of this symmetric battery, we substituted a non-flammable ionic liquid (IL) LiBF4/EMIBF4 electrolyte for the organic electrolyte. The symmetric battery using the IL electrolyte was examined galvanostatically at different rates and operating temperatures within the voltage range of 0.01-2.8 V. It was demonstrated that the IL-based symmetric cell worked as a secondary battery with a Coulombic efficiency of 77% at 0.1 mA cm-2 and 25 °C. It was also found that the use of the IL electrolyte instead of the organic one resulted in the general reduction of the first discharge capacity by about 20-25% but provided much more stable behavior and a longer cycle life. Moreover, an increase of the discharge capacity of the IL-based symmetric battery up to 120 mA h g-1 was observed when the operating temperature was increased up to 80 °C at 0.1 mA cm-2. The obtained electrochemical behavior of both symmetric batteries was confirmed by complex-impedance measurements at different temperatures and cycling states. The thermal stability of LiVPO4F with both the IL and organic electrolytes was also examined.

Original languageEnglish
Pages (from-to)1344-1351
Number of pages8
JournalElectrochimica Acta
Volume56
Issue number3
DOIs
Publication statusPublished - Jan 1 2011

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All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Electrochemistry

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