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Although, the use of hydrocarbon membranes is one of the ways to reduce the cost of polymer electrolyte membrane fuel cells, it cannot be practically adopted due to its low mechanical durability under a dynamic wet/dry operation. Here, we present an externally-reinforced hydrocarbon membrane achieved by a three dimensional interlocking interfacial layer which forms a strong interfacial bonding between the hydrocarbon membrane and the catalyst layers. Although a conventional hydrocarbon membrane is easily delaminated from gas diffusion electrodes, the use of the three dimensional interlocking interfacial layer, prepared with a polystyrene nanoparticle template method, enhances the interfacial adhesion by 207 times. The hydrocarbon membrane, tightly connected to the gas diffusion electrodes by the three dimensional interlocking interfacial layers, has a humidity cycling durability that is 1.9 times higher in the membrane electrode assembly level by restricting the dimensional change of the membrane. Furthermore, due to the proton conducting property of the three dimensional interlocking interfacial layer, the external reinforcement does not cause any power performance losses.

A poly (ethylene-co-vinyl acetate) (EVA)/polyimide (PI)/EVA (PIE) tri-layer separator with thermal stability and a shutdown function is fabricated for use in sodium-ion battery (SIB) applications. Porous EVA layers are coated on both sides of an electrospun-PI, acting as a supporting layer, through a dip-coating process accompanying a thermally induced phase separation in which polyethylene-block-poly (ethylene glycol) is used as a polymeric pore generator to obtain an open porous morphology. Excellent thermal stability of the PIE tri-layer separator is demonstrated, with two simultaneous incompatible thermal behaviors, i.e., a negligible thermal shrinkage of up to 200 °C, and a rapid thermal shutdown at approximately 100 °C. In addition, the PIE tri-layer separator shows a higher ionic conductivity and larger electrolyte uptake of the sodium liquid electrolyte than a commercial olefin separator, leading to better cycling performance when assembled into SIB coin cells. All these outstanding properties of PIE tri-layer separator demonstrate that its promise as a candidate separator for use in SIBs.