Low-Temperature Structural Battery Electrolytes Produced by Polymerization-Induced Phase Separation

High Resolution Image Download MS PowerPoint Slide Structural battery electrolytes (SBEs) possess both high ionic conductivity and high mechanical strength and stiffness. These emerging materials are critical components in load-bearing structural batteries, which offer mass and volume savings beneficial to electrified transportation and aerospace applications. However, in extreme cold (< −40 °C), conventional liquid electrolytes freeze or become too viscous to conduct ions. Further, liquid electrolytes alone are unsuitable for structural batteries because liquids cannot bear structural loads. Here, we report a two-phase solid–liquid structural battery electrolyte capable of conducting ions in extreme cold. Specifically, the structural battery electrolyte consists of a bicontinuous solid, cross-linked bisphenol A-ethoxylated dimethacrylate resin and a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/fluoroethylene carbonate (FEC)-diglyme-based liquid electrolyte. The relative liquid/solid content was varied, and ionic conductivities of 1.62 × 10 –4 S/cm at −10 °C and 7.44 × 10 –6 S/cm at −40 °C were obtained for the case of 90 wt % liquid/10 wt % solid. When the liquid content of the structural battery electrolyte was increased from 50 to 90 wt %, the modulus decreased from 0.910 GPa to 8.13 × 10 –4 GPa at 25 °C, and ultimate tensile strength (UTS) decreased from 14.9 to 0.0582 MPa. These findings culminated in the application of the structural electrolyte to a graphite vs lithium metal half-cell battery operated at 0.1 C-rate where it exhibited a charging capacity of 353 mAh g –1 (∼95% of graphite’s theoretical capacity). Taken together, these results have immediate relevance to the electrification of automobiles, aircraft, and spacecraft.