Imagine a non-flammable solid with the bulk modulus of a pure polymer (e.g., polyethylene), but where ions inside move as if they were in a liquid. I will describe a new class of solid electrolyte materials that we term “molecular ionic composites” (MICs), formed from a solution of a rigid-rod polyanion and an ionic liquid. This electrolyte provides an unprecedented combination of tunable properties: ionic conductivity up to 8 mS/cm, widely tunable modulus (E’ = 0.003−3 GPa), transport anisotropy up to 3.5X, and stability to 300 deg. C. This material relieves the usual strict tradeoff between ionic conductivity and modulus in organic electrolytes, demonstrating its potential to resolve limitations in Li metal batteries and enable tailoring to multiple battery chemistries. What if you could safely charge and discharge a battery at 120 deg. C? I will discuss our fundamental understanding of the correlated electrostatic network that gives rise to simultaneous mechanical stiffness and fast ion transport in this material. We can incorporate up to ~ 3 M Li<sup>+</sup> or Na<sup>+</sup> into this material and we will discuss pilot Li-Li symmetric cell cycling up to 2000 hrs at 0.2 mA/cm^2. In addition to battery applications, this new class of materials promises to facilitate optimization of properties for, e.g., “artificial muscle” electromechanical actuators, fuel cells, and other molecular separations applications.

Molecular ionic composite electrolytes to enable safer and higher energy density batteries

255th National Meeting (2018)

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