TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The polyprotic acid is present in an amount of 180-300 wt.%. The polyprotic acid comprises phosphoric acid.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The aromatic polyether copolymer is selected from 5 copolymers as given in the specification e.g. Copolymers (I)-(III) or (V). The aromatic polyether copolymer is Copolymer (I) or Copolymer (II) and has main chain pyridine groups and side chain carboxylic acid groups. When the aromatic polyether copolymer is Copolymer (II), the copolymer has main chain pyridine groups and side chain hydroxyl phenyl. When the aromatic polyether copolymer is Copolymer (III), the copolymer has main chain and side chain pyridine groups and side chain propenyl groups. When the aromatic polyether copolymer is Copolymer (II) or Copolymer (IV) or Copolymer (V), the copolymer has main and side chain pyridine groups and side styrene groups. When the aromatic polyether copolymer is Copolymer (I), the copolymer is doped with a polyprotic acid at an amount of about 160-350 wt.%. When the aromatic polyether copolymer is Copolymer (II), the copolymer is doped with a polyprotic acid at an amount of about 180-400 wt.%. When the aromatic polyether copolymer is Copolymer (III), the copolymer is doped with a polyprotic acid at an amount of about 100-350 wt.%. When the aromatic polyether copolymer is Copolymer (IV), the copolymer is doped with a polyprotic acid at an amount of about 100-400 wt.%. When the aromatic polyether copolymer is Copolymer (V), the copolymer is doped with a polyprotic acid at an amount of about 100-400 wt.%. The crosslinked polymer electrolyte produced from the method (M1) is doped with a polyprotic acid at an amount of 100-400 wt.%. The crosslinked polymer electrolyte produced from the method (M2) is doped with a polyprotic acid at an amount of about 100-400 wt.%. The crosslinked polymer electrolyte produced from the method (M3) is doped with a polyprotic acid at an amount of 100-400 wt.%. The crosslinked polymer electrolyte produced from the method (M4) is doped with a polyprotic acid at an amount of 100-400 wt.%. The crosslinked polymer electrolyte produced from the method (M5) is doped with a polyprotic acid at an amount of 100-400 wt.%. EXAMPLE - A Copolymer (I) (with x of 55, y of 0, z of 45) (0.4 g) were dissolved in 8 ml N-methyl pyrrolidone. Then 0.07 g terephthalic dihydrazide were mixed with 0.04 g calcium chloride in 0.14 g dry pyridine and 0.4 g diphenyl phosphite in 2 ml N-methylpyrrolidone. The two solutions were mixed and stirred at 100 degrees C for 5 hours. The final solution was purred to a Petri dish. Then the dish was covered and left at reflux conditions in the oven at 140 degrees C for 24 hours. Finally, the dish was uncovered and the solvent was left to evaporate at 140 degrees C for 24 hours. The prepared membrane was washed with 200 ml methanol for 5 hours and dried under high vacuum at 280 degrees C for 24 hours.