Development of Epoxy-Resin Based Solid Electrolytes for Multifunctional Structural Batteries

A structural battery is defined as being multifunctional; it is a load bearing system with some electrochemical energy storing capability. The electrolyte system is the key enabler for a multifunctional structural battery as it must possess sufficient ionic conductivity (~10 -4 S/cm) and mechanical strength (Youngs’s modulus ~ 600-900 MPa) simultaneously. Polymeric systems offer the best possible scenario for practical realization of multifunctional structural batteries due to a set of favorable properties, such as reasonable ionic conductivity, easy processability etc. In the present work, we focus on the development of a dual-phase structural battery electrolyte to optimize ionic conductivity and mechanical performance simultaneously. An epoxy resin-based system is chosen due to its high mechanical strength and its ability for in-situ polymerization that leads to a unique microstructure promoting multi-functionality. Diglycidyl ether of Bisphenol A (DGEBA) accounts for the epoxy to provide hard segments in the matrix and is cured by an amine compound (Jeffamine T-403). A liquid electrolyte is added to the system for improving ionic conductivity without compromising its mechanical strength substantially. Multiple liquid components consisting of lithium salt and solvents are considered -lithium bis(trifluoromethanesulfonyl)imide (LITFSI) dissolved in a solution of ethylene carbonate (EC) and dimethyl methyl phosphonate (DMMP) and LiTFSI dissolved in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI). Ionic conductivity of the electrolyte systems as a function of temperature is measured utilizing electrochemical impedance spectroscopy. Uniaxial load tests are performed to evaluate the mechanical properties (e.g., Young’s modulus, Yield strength) of the epoxy-based electrolyte systems with and without the addition of the ion conducting liquids. Comparative data on the epoxy-based systems containing varying amounts of liquid components will be presented.