In this study, we synthesized zirconium (IV)-hydroxy ethylidene diphosphonates (ZrHEDPs) to investigate whether the reliance of proton conductivity on RH can be overcome by making the close distance between phosphonic acid groups. ZrHEDP has hydrocarbon-based phosphonic acid groups, -C(OH)CH3-PO3H2, and the average distance between the acid moiety was controlled by synthesis conditions. ZrHEDP is one of the best electrolytes to demonstrate the objective due to its rigid structure and property of having acidic groups at a close distance.