Gel electrolyte comprised of a solvate ionic liquid and methyl cellulose

Mechanically strong, self-standing, high conductivity solid iongel electrolytes with good thermal stability (Td ~ 200 0C) and an anodic stability up to 5 V, were prepared using the solvate ionic liquid [G4Li]+[TFSI]- in methyl cellulose (MC) with 90 weight percent liquid. The excellent combination of high room temperature conductivity (σ > 10-4) and mechanical strength (E′ ~ 60 MPa) is due to the semi-crystalline fibrillar network formed by the MC. The high anodic stability of 5V for the iongel is attributed to the known 4.5 V stability of the [G4Li]+[TFSI]- and the -OH groups on MC, which hydrogen bond with any free G4 not in the [G4Li]+[TFSI]- complex, so that they are unavailable for oxidation. Li0/iongel/Li0 plating/stripping at low current densities are stable with low polarization but at high current densities the polarization and cell impedance increase, which is due to mosaic lithium plating. Coin cells of Li0/iongel/LiFePO4 could be cycled at C/2 (1C = 170 mAh/g) for at least 100 cycles with 98-9...