Liquid and Polymer Gel Electrolytes for Lithium Batteries Composed of Room-Temperature Molten Salt Doped by Lithium Salt

Abstract

The lithium ion binary room-temperature molten salt ͑i.e., ionic liquid͒, LiEMIBF 4 was prepared by mixing 1-ethyl-3methylimidazolium tetrafluoroborate (EMIBF 4 ) with LiBF 4 . The ionic conductivity of LiEMIBF 4 was 7.4 mS cm Ϫ1 at 20°C and lower than that of EMIBF 4 . A solidified LiEMIBF 4 , named GLiEMIBF 4 , was prepared by in situ polymerization of poly͑ethyl-eneglycol͒ diacrylate with LiEMIBF 4 . The ionic conductivity of the homogeneous transparent membrane obtained was smaller than that of LiEMIBF 4 . The thermal decomposition temperatures of these ''ionic media'' measured by thermogravimetrydifferential thermal analysis showed that LiEMIBF 4 and GLiEMIBF 4 have high thermal stability around 300°C. The cathodic limit of EMIBF 4 was ca. 1.1 V vs. Li/Li ϩ measured by linear sweep voltammetry. To test the possibility of use of these ionic media for lithium-ion batteries, demonstration cells of Li͓Li 1/3 Ti 5/3 ͔O 4 /LiEMIBF 4 or GLiEMIBF 4 /LiCoO 2 were assembled. The capacity retention after 50 cycles was 93.8% of the initial capacity in the LiEMIBF 4 cell. Discharge potential profile of the GLiEMIBF 4 cell showed decline probably due to the concentration polarization in the gelled electrolyte. Liquid and gelled electrolytes composed of ''lithium ion coexisting room-temperature molten salt'' are shown to function as nonflammable electrolytes in the lithium-ion batteries.

Precipitated silica as filler for polymer electrolyte based on poly(acrylonitrile)/sulfolane

“…In the case of studies on ionic liquid electrolytes, usually 10-100 cycles are reported. Also, the capacity loss may be higher when ionic liquids are used as electrolytes [55].…”

Electrolytes for high-energy lithium batteries

“…Still, the Bellcore electrolyte suffers from the other problems associated with aprotic liquid electrolytes: low thermal stability, low cathodic stability, volatility, flammability and insufficient moduli to prevent dendritic lithium growth. Ionic liquid-based gel polymer electrolytes are now widely studied as a possible solution to some of these issues (Rupp et al 2008;Fuller et al 1998;Nakagawa et al 2003;Cheng et al 2007;Liao et al 2010); PEO-based gel polymer electrolytes have also been explored, by swelling a high molecular weight PEO matrix with PEG oligomers (Borghini et al 1996). Ceramic-liquid electrolytes ''Soggy sand'' electrolytes are created by doping a liquid electrolyte with ceramic nanoparticles (Bhattacharyya et al 2004;Bhattacharyya 2009, 2010;Walls et al 2003).…”

About the Purification Route of Ionic Liquid Precursors

“…These unique chemical properties, responsible of strongly growing interest towards ionic liquids in the last fifteen years, have addressed RTILs to a very wide variety of applications, in particular as "green" solvents for chemical reactions, bi-phasic catalysis, chemical synthesis, separation and extraction processes, advanced high-temperature lubricants, transfer fluids in solar thermal energy systems [4][5][6][7][8][9][10][11][12][13][14][15][16], and as electrolytes (or electrolyte components) for electrochemical devices including batteries, fuel cells, double-layer capacitors, hybrid super-capacitors, photo-electrochemical cells, and electroplating of electropositive metals [3,[17][18][19][20][21][22][23][24][25][26][27].…”