Coordination polymer glass from a protic ionic liquid: proton conductivity and mechanical properties as an electrolyte

High proton conducting electrolytes with mechanical moldability are a key material for energy devices. We propose an approach for creating a coordination polymer (CP) glass from a protic ionic liquid for a solid-state anhydrous proton conductor. A protic ionic liquid (dema)(H(2)PO(4)), with components which also act as bridging ligands, was applied to construct a CP glass (dema)(0.35)[Zn(H(2)PO(4))(2.35)(H(3)PO(4))(0.65)]. The structural analysis revealed that large Zn–H(2)PO(4)(−)/H(3)PO(4) coordination networks formed in the CP glass. The network formation results in enhancement of the properties of proton conductivity and viscoelasticity. High anhydrous proton conductivity (σ = 13.3 mS cm(−1) at 120 °C) and a high transport number of the proton (0.94) were achieved by the coordination networks. A fuel cell with this CP glass membrane exhibits a high open-circuit voltage and power density (0.15 W cm(−2)) under dry conditions at 120 °C due to the conducting properties and mechanical properties of the CP glass.