Crystalline solid electrolytes II Material design

Center for Materials Science Engineering, University of Texas at Austin 

A solid electrolyte is an ionic conductor and an electronic insulator. Ideally, it conducts only one ionic species. Aside from a few specialty applications in the electronics industry, solid electrolytes are used almost exclusively in electrochemical cells. They are particularly useful where the reactants of the electrochemical cell are either gaseous or liquid however, they may be used as separators where one or both of the reactants are solids. Used as a separator, a solid electrolyte permits selection of two liquid or elastomer electrolytes each of which is matched to only the solid reactant with which it makes contact. 

Electrochemical cells are of two types power cells and sensors. In an ideal power cell, the ionic current through the electrolyte inside the cell matches an electronic current through an external load. The solid electrolyte is in the form of a membrane of thickness L and area A that separates electronically the two electrodes of the cell. Any internal electronic current across the electrolyte reduces the power output. The internal resistance to the ionic current is 

These simple considerations lead to the following general criteria for the quality of a solid-electrolyte material to be used in an electrochemical cell. 

---