Abstract: A hybrid solid-state electrolyte layer for use in an electrochemical cell is provided. The hybrid solid-state electrolyte layer includes a polymeric material, a ceramic material, and an interfacial material adhering the polymeric material and the ceramic material. The interfacial material includes a branched copolymer that includes dopamine and a second monomer. The second monomer forms a polymeric moiety in the copolymer that is the same or similar to the polymeric material. In certain variations, the polymeric material defines a polymeric layer, the ceramic material defines a ceramic layer, and the interfacial material defines an interfacial layer that is disposed between the polymeric layer and the ceramic layer. In other variations, the polymeric material defines a polymeric matrix, the ceramic material defines a plurality of ceramic particles dispersed in the polymeric matrix, and the plurality of ceramic particles are coated with the interfacial material.