Materials for rechargeable batteries and clean hydrogen energy sources

Materials for energy sources, such as rechargeable batteries and fuel cells, are functional materials. Their development presents special challenges since they are designed for more than one function and must satisfy multiple and mostly interlocking requirements. A unique combination of properties is achievable in complex structures such as functional composites, multi-element and multiphase intermetallics, cermets, layered insertion compounds, and new nanostructured and disordered phases. This review deals with a variety of such materials being developed for use in clean energy storage, which is mostly, but not entirely, hydrogen energy storage. The scope of the work encompasses hydrogen gas storage alloys and intermetallics used for electrochemical hydrogen storage, insertion compounds for Li batteries, and ceramics and metal catalysts for fuel cells. It also includes materials used in lead-acid, nickel metal hydride, and lithium rechargeable batteries as well as in solid oxide, proton exchange membrane, and direct methanol fuel cells. Special topics highlight new nanostructured materials obtained by rapid quenching, mechanical alloying, and other processes. The review is complemented by a brief discussion of present trends in assessment of materials requirements for batteries and fuel cells for electric vehicles and portable telecommunication. Also addressed are aspects of recycling and life-cycle analysis.