Shear Thickening, Star-Shaped Polymer Electrolytes for Lithium-Ion Batteries

The safety concerns associated with current lithium-ion batteries are a significant drawback. A short-circuit within the battery's internal components, such as those caused by a car accident, can lead to ignition or even explosion. To address this issue, a polymer shear thickening electrolyte, free from flammable solvents, has been developed. It comprises a star-shaped oligomer derived from a trimethylolpropane (TMP) core and polyether chains, along with the inclusion of 20 wt.% nanosilica. Notably, the star-shaped oligomer serves a dual function as both the solvent for the lithium salt and the continuous phase of the shear thickening fluid. The obtained electrolytes exhibit an ionic conductivity of the order of 10^-6 S cm^-1 at 20 °C and 10^-4 S cm^-1 at 80 °C, with a high Li⁺ transference number (t₊ = 0.79). A nearly thirtyfold increase in viscosity to a value of 1187 Pa s at 25 °C and a critical shear rate of 2 s^-1 were achieved. During impact, this electrolyte could enhance cell safety by preventing electrode short-circuiting.