Organophosphates as Solvents for Electrolytes in Electrochemical Devices

Abstract

A homologous series of fire-retardant oligoalkyleneoxy-phosphates was synthesized for evaluation as liquid or gel-type electrolyte media for dye-sensitized solar cells (DSSCs) and secondary lithium batteries. Unoptimized DSSC electrolyte formulations for DSSCs achieved ionic conductivities as high as 5.71 × 10(-3) S · cm(-1) and DSSC test-cell efficiencies up to 3.6% as well as Voc, Jsc, and ff up to 0.81 V, 8.03 mA · cm(-2), and 0.69, respectively. Poly(bis-(2-(2-methoxyethoxy)ethoxy)phosphazene)-based Li(+)-conducting gel electrolytes plasticized with the best performing phosphate had conductivities as high as 9.9 × 10(-4) S · cm(-1) at 30 °C. All the liquids have boiling points higher than 197 °C. The results show that the viscosity, glass transition temperatures, and conductivity of the phosphates are dependent mainly on the length of the longest alkyleneoxy chain.