Here, we will report on the electrodynamics of a shear-thickening electrolyte that may serve a multifunctional purpose in Li-ion batteries: a high conductive and impact resistance ion conductor. Perhaps more important than the continual improvement in charge and power density of batteries for consumer electronics and vehicles is the need to improve safety and reliability. The incorporation of safety features typically comes with added weight and handicapped performance. Multifunctional materials may aid in alleviating these particular drawbacks by providing both mechanical strength and contribution to charge storage or ion conduction. A common strategy in making batteries safer is the replacement of the liquid electrolytes with solid state ones, as this removes the need for volatile and flammable organics and may allow for the use of lithium metal. However solid state electrolytes currently are expensive and difficult to process and incorporate into large scale batteries.

We have developed shear-thickening lithium ion battery electrolytes for improved safety in high impact events. They are able to reversibly transition into a solid-like phase under high shear and then relax back into a liquid when free of stress. While we will demonstrate that this aids in the prevention of shorting and subsequent combustion of volatile electrolyte under such conditions, this presentation is focused on our investigation of the electrodynamics of shear-thickening electrolytes using conductivity under shear measurements. We incorporate finite element modeling to aid in interpreting the observation of an order of magnitude drop in ionic conductivity under shear-thickening conditions. We explain the substantial drop in conductivity under shear in terms of a change in effective viscosity, as suggested by Figure 1, though we acknowledge that a change in tortuosity is possible. The results here can be generally applied to any electrolyte that exhibits non-Newtonian hydrodynamic properties.

This material is based upon work supported by theU.S.Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program (BHS). The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. This work was supported by the U.S.Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering (RLS, GMV).