An energy device has an electrode including lithium cobaltite (LCO) grains, where the LCO grains are sintered to one another forming a self-supporting sheet with porous passages. The porous passages wind and branch through the sheet. The energy device further includes a solid electrolyte comprising lithium phosphosulfide (LPS) overlaying a major surface of the sheet and extending into the porous passages. The sheet serves as mechanical support for the solid electrolyte, allowing for high temperature joining of the LPS to the LCO without binder in the LPS.