POLYMERISIED MEDIUM INTERNAL PHASE EMULSIONS AS STRUCTURAL SEPARATORS

摘要

To achieve true multifunctionality of the energy storage device, all elements of it have to be able to perform two roles simultaneously. Currently most related research is focused on the development and/or improvement of electrodes and electrolyte while research into the separator is rather limited. Here, the feasibility of using polymerised non-aqueous medium internal phase emulsions (polyMIPEs), based on Bisphenol A diglycidyl ether (DGEBA), as separators for structural supercapacitors is presented. To ensure ion conduction in the separator a deep eutectic solvent (DES), based on choline chloride (ChCl) and ethylene glycol (EG), was used as an internal phase in the studied systems. The effect of surfactant concentration and rate of internal phase addition on the properties, such as ionic conductivity and compressive properties, and microstructure of the resulting polyMIPEs were investigated. Increasing the surfactant concentration led to the formation of a less defined microstructure with a wider pore size distribution, increased ionic conductivity and reduced mechanical performance, as well as an improved tolerance towards variations in drop rate of internal phase (DES) addition. It was found that the minimum drop rate for MIPE preparation was 0.39 ml/min and further reduction led to the formation of large air bubbles/defects. The change in morphology meant that polyMIPEs stabilised by 20 wt% surfactant exhibited lower ionic conductivity and mechanical properties across the systems investigated. PolyMIPEs with an ionic conductivity of 1.9 mS/cm, which is only 4 times lower than the ionic conductivity of the neat DES (7.58 mS/cm), and a compressive modulus of 0.21 GPa were achieved.