ELECTROCHEMICAL CELL, ELECTROCHEMICAL CELL DEVICE, MODULE, AND MODULE HOUSING DEVICE

An electrochemical cell includes a solid electrolyte layer and a first electrode. The solid electrolyte layer includes a first material having ion conductivity and in which a rare earth element is contained as a solid solution. The first electrode contains a rare earth element and has a first surface contacting the solid electrolyte layer and a second surface on a side opposite to the first surface. A content proportion of the rare earth element in the first electrode is higher on a side of the second surface than on a side of the first surface.