This book combines the proceedings of Symposium EE, Solid-State Ionics, and Symposium FF, Materials for Fuel Cells and Fuel Processors, both from the 2002 MRS Fall Meeting in Boston. Current developments in solid-state ionics, and advances in the domains of energy storage and conversion and environmental monitoring, are featured. The largest clusters of papers are devoted to lithium batteries and fuel cell technology. It reflects the dominating relevance of these applications for fostering the modern telecommunications and information society and the development of environmentally friendly electric transportation and energy transformation systems, replacing traditional combustion technology. Topics include: theory/inorganic ion conductors; oxide electroceramics for separation membranes and gas sensors; cathode materials for lithium batteries; anode materials for lithium batteries and polymer electrolytes; proton exchange membrane fuel cells; and solid oxide fuel cells.