New covalent salts of the 4+ V class for Li batteries

Leszek Niedzicki , Sylvie Grugeon , Stéphane Laruelle , Patrick Judeinstein , Maria Bukowska , J. Prejzner , Przemysław Szczeciński , Władysław Wieczorek , Michel Armand


There is urgent action required for replacing LiPF6 as a solute for Li-ion batteries electrolytes. This salt, prone to highly Lewis acidic PF5 release and hydrolysis to HF is responsible for deleterious reaction on carbonate solvents, corrosion of electrode materials leading to safety problems then release to toxic chemicals. A major advantage of LiPF6 is that it passivates aluminium. Most attempts to replace LiPF6 with hydrolytically-stable salts have been unsuccessful because of Al corrosion. We present here two “Hückel” type salts, namely lithium (2-fluoroalkyl-4,5-dicyano-imidazolate); fluoroalkyle = CF3 (TDI), C2F5 (PDI) with high charge delocalization. These thermally stable salts give both appreciably conductive solutions in EC/DMC (\>6 mS cm−1 at 20 °C) with a lower decrease with temperature than LiPF6. Non fluorinated lithium (4,5-dicyano-1,2,3-triazolate) is comparatively less than half as conductive. The lithium transference number T+ measured by PFG-NMR is also higher. Voltammetry scans with either platinum or aluminium electrodes show an oxidation wall at 4.6 V versus Li+:Li°. These two salts are thus the first examples of strictly covalent, non-corroding salts allowing 4+ V electrode material operation. This is demonstrated with experimental Li/LiMn2O4 cells as beyond the third cycles, the fade of the three electrolytes were quasi-identical, though LiPF6 had a sharper initial decrease.
Author Leszek Niedzicki KChNTCS
Leszek Niedzicki,,
- Chair Of Inorganic Chemistry And Solid State Technology
, Sylvie Grugeon
Sylvie Grugeon,,
, Stéphane Laruelle
Stéphane Laruelle,,
, Patrick Judeinstein
Patrick Judeinstein,,
, Maria Bukowska IB
Maria Bukowska,,
- Insitute of Civil Engineering
, J. Prejzner
J. Prejzner,,
, Przemysław Szczeciński ZChO
Przemysław Szczeciński,,
- Department Of Organic Chemistry
, Władysław Wieczorek KChNTCS
Władysław Wieczorek,,
- Chair Of Inorganic Chemistry And Solid State Technology
, Michel Armand
Michel Armand,,
Journal seriesJournal of Power Sources, ISSN 0378-7753
Issue year2011
Keywords in EnglishHückel anion, Li-ion battery, Lithium salt, Nonaqueous electrolyte
Languageen angielski
Journal of Power Sources.pdf 824.96 KB
Score (nominal)40
Publication indicators WoS Impact Factor [Impact Factor WoS]: 2011 = 4.951 (2) - 2011=5.006 (5)
Citation count*18 (2015-03-10)
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* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.