Ionic conductivity of bis(2-cyanoethyl) ether-lithium salt and poly(propylether imine)-lithium salt liquid electrolytes

Abstract

We report here a multiple-nitrile based lithium-salt liquid electrolyte. The ionic conductivity of poly (propyl ether imine) (abbreviated as PETIM) lithium salt dendrimer liquid electrolyte was observed to be a function of dendrimer generation number, n = 0 (monomer)−3. While the highest room temperature ionic conductivity value (∼ 10⁻¹ Sm⁻¹) was recorded for the bis-2cyanoethyl ether monomer (i.e. zeroth generation; G₀-CN), conductivity decreased progressively to lower values (∼ 10⁻³ Sm⁻¹) with increase in generation number (G₁-CN → G₃-CN). The G₀-CN and higher dendrimer generations showed high thermal stability (≈150 to 200 °C), low moisture sensitivity and tunable viscosity (∼10⁻² (G₀-CN) to 3 (G₃-CN) Pa s). The linker ether group was found to be crucial for ion transport and also eliminated a large number of detrimental features, chiefly moisture sensitivity, chemical instability associated typically with prevalent molecular liquid solvents. Based on the combination of several beneficial physicochemical properties, we presently envisage that the PETIM dendrimers especially the G₀-CN electrolytes hold promise as electrolytes in electrochemical devices such as lithium-ion batteries.