Bicontinuously crosslinked polymer electrolyte membranes with high ion conductivity and mechanical strength

Recently, safety has become an important issue for energy storage devices due to explosion and leakage of conventional liquid electrolytes. Traditional polymer electrolytes also have a strong dependence on the tradeoff relationship and do not exhibit sufficient ionic conductivity as a solid; thus, they are often used as a gel. We report the preparation of a highly ion-conducive, mechanically strong solid electrolyte membranes based on bicontinuously crosslinked polymer electrolytes for solid-state supercapacitors. The solid electrolyte membranes are synthesized in situ via facile ring-opening polymerization in the presence of a conducive ionic liquid without any solvents. The crosslinking structure is based on the reaction of the amines of the polyethylenimine oligomer with the epoxy groups of hydrophilic poly(ethylene glycol) diglycidyl ether and hydrophobic bisphenol A diglycidyl ether at 50 degrees C for 3 h. This unique structure endows the solid electrolyte membranes with high tensile strength as well as high ion conductivity (2.41 x 10(-3) S cm(-1) at 25 degrees C). All the membranes have good thermal stability and an amorphous phase in which the ionic species are uniformly distributed in the matrix. Upon application to solid-state supercapacitors based on carbon electrodes, a capacitance of 19.8 F g(-1) at 2 mV s(-1) is obtained, with an excellent capacitance retention and a coulombic efficiency close to 100% for 10,000 cycles. The solid electrolyte membrane has potential applications in structural supercapacitors and batteries, which require high mechanical strength.