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Molecular ionic composites (MICs) are a new class of solid electrolytes that combine ionic liquids (ILs) and a rigid-rod double helical polyelectrolyte, poly(2,2′-disulfonyl-4,4′benzidine terephthalamide) (PBDT). In this study, we focus on the mechanical, dielectric, and ion diffusive dynamics of MICs with a fixed PBDT weight percent (10 wt%) and varying IL chemistry and molecular volume ( V m ). All six MICs produce tensile moduli in the range of 50–500 MPa at 30 °C, up to 60× higher than the shear moduli of the same MICs. The high range of moduli and tensile to shear modulus ratio emphasizes that the distribution of PBDT chains and the strong ionic interactions between IL ions and PBDT chains dictate the modulus and the mechanical strength in MICs. Additionally, these MICs exhibit high ionic conductivities ranging from 1–6 mS cm −1 at 30 °C, consistent with the measured diffusion coefficients of the IL ions. The tunability of the extraordinary mechanical properties and high ionic conductivities of MIC electrolytes greatly inspire their use in advanced electrochemical devices. 

A critical challenge for next-generation lithium-based batteries lies in development of electrolytes that enable thermal safety along with use of high-energy-density electrodes. We describe molecular ionic composite (MIC) electrolytes based on an aligned liquid crystalline polymer combined with ionic liquids and concentrated Li salt. This high strength (200 MPa) and non-flammable solid electrolyte possesses outstanding Li+ conductivity (1 mS·cm-1 at 25 °C) and electrochemical stability (5.6 V vs Li|Li+) while suppressing dendrite growth and exhibiting low interfacial resistance (32 Ω·cm2) and overpotentials (≤ 120 mV @ 1 mA·cm-2) during Li symmetric cell cycling. A heterogeneous salt doping process modifies a locally ordered polymer-ion assembly to incorporate an inter-grain network filled with defective LiFSI & LiBF4 nanocrystals, strongly enhancing Li+ conduction. This modular material fabrication platform shows promise for safe and high-energy-density energy storage and conversion applications, incorporating the fast transport of ceramic-like conductors with the superior flexibility of polymer electrolytes.