Mass transport in materials incorporated in electrochemical energy conversion systems

Abstract

The microscopic parameters influencing fast ion conduction in materials incorporated in electrochemical energy conversion systems are briefly surveyed. The problems encountered in designing materials to satisfy the specifications for fast ion conduction are illustrated with specific reference to framework structures exhibiting fast sodium ion conduction, to oxygen ion conductivity in oxide fluorite solid solutions, and to lithium ion conducting glasses. The additional constraints that are introduced when these materials are incorporated into practical electrochemical energy conversion systems are discussed with special reference to high-energy sodium secondary batteries and to the development of completely solid-state batteries. A survey of the principal types of fuel cells concludes with the need for improved oxygen ion conductors to be incorporated into moderate-temperature systems (500–600°C). The final section on the performance of oxygen monitors is included to emphasise the role of electrode kinetics as well as the need for improved fast ion conducting materials.