A high transference number, thin-film electrolyte structure suitable for a battery includes a non-conducting organic phase portion and plurality of ion-conducting inorganic phase structures. The inorganic phase structures are dispersed throughout the organic phase portion and arranged generally in a layer. The inorganic phase structures are configured to span a thickness of the organic phase portion such that a respective portion of each structure is exposed on opposite sides of the organic phase portion. Respective interfaces between the organic phase portion and the inorganic phase structures possess strong adhesion characteristics via an unbroken chain of ionic bonds and/or covalent bonds. The interfaces in some embodiments include at least one adhesion promoter configured to promote adhesion between the organic phase portion and the inorganic phase structures. The inorganic phase structures in some embodiments have surfaces that are modified using a surface modification agent to promote adhesion to the organic phase portion.