Disclosed are electrochemical devices, such as lithium ion battery electrodes, lithium ion conducting solid-state electrolytes, and solid-state lithium ion batteries including these electrodes and solid-state electrolytes. Also disclosed are composite electrodes for solid state electrochemical devices. The composite electrodes include one or more separate phases within the electrode that provide electronic and ionic conduction pathways in the electrode active material phase. A method for forming a composite electrode for an electrochemical device is also disclosed. One example method comprises (a) forming a mixture comprising (i) a lithium host material, and (ii) a solid-state conductive material comprising a ceramic material having a crystal structure and a dopant in the crystal structure; and (b) sintering the mixture, wherein the dopant is selected such that the solid-state conductive material retains the crystal structure during sintering with the lithium host material.