Preparation and characterization of poly(vinylidene fluoride) based composite electrolytes for electrochemical devices

PVdF-based separators are very promising materials in electrochemical energy storage systems but theysuffer from fairly poor mechanical properties. To overcome this drawback, composite PVdF separatorswere fabricated and characterized in electrolytes of Li-ion batteries and supercapacitors. MacroporousPVdF composite separators were prepared by phase inversion method using PA and PET, and non-woven cellulose as support layers. Ionic conductivity and thermomechanical analyses were performedusing electrolytes of Li-ion batteries and supercapacitors. The composite approach allowed a tremen-dous increase of the mechanical performances of the separator (between 340 and 750 MPa) comparedto the unreinforced PVdF separator (56 MPa), without compromising the ionic conductivities (up to15.6 mS cm-1)

The Interest of Diazonium Chemistry for Aqueous Lithium-Ion Battery

International audienceAqueous Li-Ion rechargeable batteries (ARLB) could be a promising candidate for a low cost and potentially green battery technology with medium energy level. Nevertheless, their practical interest is mainly linked to the increase of their nominal voltage beyond the water electrochemical stability window. This paper deals with the use of the diazonium chemistry for increasing water reduction overvoltage through the films formed on the electrode surface though their reduction. According to the chemistry chosen, we have put in evidence that the use of difunctional diazonium doesn't limit the performances of the positive LFP electrode on aqueous electrolyte and allows increasing from 200 mV to 400 mV the water reduction overpotential

Chemically controlled protective film based on biphenyl derivatives for high potential lithium battery

International audienceHigh potential cathodes are of strong interest to improve lithium-ion battery performances, nevertheless, no compatible electrolyte above 4.5–4.8 V vs Li+/Li was found yet. The main strategies involved the use of protective film inhibiting and/or delaying electrolyte degradation. In this context, we focused on the use of adapted modified biphenyls to form a protective film at the positive electrode. Particularly phosphate biphenyl derivatives oxidation permits to produce a protective film which significantly decreases the self-discharge without compromising the lithium intercalation kinetic

Investigation of methoxypropionitrile as co-solvent for ethylene carbonate based electrolyte in supercapacitors. A safe and wide temperature range electrolyte

International audienceThe performances obtained with methoxypropionitrile/ethylene carbonate mixture based electrolytes were investigated in supercapacitor application. The incorporation of methoxypropionitrile allows a good compromise between electrochemical performances and safety issue to be exhibited in a wide temperature range. This improvement is associated with the decrease of electrolyte viscosity without compromising the salt solubility and dissociation. The highest conductivity values, 20 mS cm−1 at 30 °C compared to 14 mS cm−1 in PC (propylene carbonate), were obtained with both 1 M tetraethylammonium tetrafluoroborate (TEABF4) and spiro-(1,1′)-bipyrrolidium tetrafluoroborate (SBPBF4) salts. Bulk liquid state was conserved for these electrolytes in a wide temperature range. Then, interesting electrolyte conductivities were obtained at low temperature (5.2 mS cm−1 at −25 °C) which is twice that of PC + TEABF4 1 M electrolyte at the same conditions. Moreover, the capacitor performance of EC/MP based electrolyte is better than PC one at room temperature

Syntheses of a wide family of new aryl based perfluorosulfonimide lithium salts. Electrochemical performances of the related polymer electrolytes

International audienceThis paper reports both on a general multistep synthesis of a wide family of aryl substituted perfluorosulfonimides and on a preliminary electrochemical investigation of two lithium salts hosted by a poly(oxyethylene) homopolymer. Both salts have a cationic transference number more than twice that of LiTFSI. Additionally, one of these salts exhibits markedly higher cationic conductivities than POE/LiTFSI electrolytes. These preliminary data are very encouraging as, thanks to the aryl moiety, a wide variety of salts can be considered in order to still improve the performances of polymer electrolytes