A composite electrolyte structure, comprising: a first side and a second side defining a thickness; a non-conducting organic phase portion extending from the first side to the second side; and a plurality of ion-conducting inorganic phase structures dispersed throughout the non-conducting organic phase portion, each of the plurality of ion-conducting inorganic phase structures spanning the thickness such that a first portion of each of the plurality of ion-conducting inorganic phase structures is exposed on the first side and a second portion of each of the plurality of ion-conducting inorganic phase structures is exposed on the second side, each of the plurality of ion-conducting inorganic phase structures defining a respective interface with the non-conducting organic phase portion, wherein each of the respective interfaces includes an unbroken chain of at least one of ionic bonds and covalent bonds so as to firmly adhere the non-conducting organic phase portion to each of the plurality of ion-conducting inorganic phase structures, wherein each of the plurality of ion-conducting inorganic phase structures is formed from a monocrystalline material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second layer of a second adhesion promoter disposed on the first layer, or wherein each of the plurality of ion-conducting inorganic phase structures is formed from an amorphous material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second adhesion promoter reacted with the first layer, or wherein each of the plurality of ion-conducting inorganic phase structures is formed from a glass ceramic material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second adhesion promoter grafted on the first layer. a first side and a second side defining a thickness; a non-conducting organic phase portion extending from the first side to the second side; and a plurality of ion-conducting inorganic phase structures dispersed throughout the non-conducting organic phase portion, each of the plurality of ion-conducting inorganic phase structures spanning the thickness such that a first portion of each of the plurality of ion-conducting inorganic phase structures is exposed on the first side and a second portion of each of the plurality of ion-conducting inorganic phase structures is exposed on the second side, each of the plurality of ion-conducting inorganic phase structures defining a respective interface with the non-conducting organic phase portion, wherein each of the respective interfaces includes an unbroken chain of at least one of ionic bonds and covalent bonds so as to firmly adhere the non-conducting organic phase portion to each of the plurality of ion-conducting inorganic phase structures, wherein each of the plurality of ion-conducting inorganic phase structures is formed from a monocrystalline material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second layer of a second adhesion promoter disposed on the first layer, or wherein each of the plurality of ion-conducting inorganic phase structures is formed from an amorphous material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second adhesion promoter reacted with the first layer, or wherein each of the plurality of ion-conducting inorganic phase structures is formed from a glass ceramic material, the structures each including a first layer of a first adhesion promoter disposed on a surface of the structure and a second adhesion promoter grafted on the first layer. <EOS>