Reinforced ion-conducting membrane

A reinforced ion-conducting membrane comprising:

• an ion-conducting polymer;
• and
• a porous mat of nanofibres, which is impregnated with the ion-conducting polymer;
• wherein the nanofibres comprise a cross-linked polymer, wherein the cross-linked polymer is ionically non-conductive and comprises:
• heterocyclic-based polymer backbones comprising basic functional groups, and
• linking chains linking at least two of the heterocyclic-based polymer backbones via linking groups, wherein the linking chains have a different chemical structure to the heterocyclic-based polymer backbone;
• wherein the porous mat has a mean average thickness of 10 μm or less and the reinforced ion-conducting membrane has a secant modulus at 8% strain of at least 30 MPa when measured in a machine direction at 80° C. and 90% RH, and a secant modulus at 8% strain of at least 30 MPa when measured in a transverse direction at 80° C. and 90% RH, wherein the machine direction and the transverse direction are perpendicular.

The method of producing a reinforced ion-conducting membrane, the method comprising the steps of:

• providing a substrate;
• providing a formulation for electrospinning, the formulation comprising a solvent, a cross-linker and a heterocyclic-based polymer comprising basic functional groups,
• electrospinning the formulation onto the substrate to form a porous mat of nanofibres;
• treating the porous mat to cause the heterocyclic-based polymer and the cross-linker to react thereby forming a cross-linked polymer comprising a heterocyclic-based polymer backbone comprising basic functional groups, and linking chains linking at least two of the heterocyclic-based polymer backbones via linking groups, wherein the linking chains have a different chemical structure to the heterocyclic-based polymer backbone;
• and
• impregnating the porous mat with an ion-conducting polymer.