Air electrode design for sustained high power operation of Li/air batteries

The rapid development of portable electronic devices increasingly requires much more energy to support advanced functions. However, currently available batteries do not meet the high energy requirement of these devices. Metal/air batteries, especially Li/air batteries, have a much higher specific energy than most other available batteries, but their power rate is limited by the accumulation of reaction products in the air electrode. Several approaches to improve the power rate of Li/air batteries have been analyzed in this work, including adjustment of air electrode porosity and catalyst reactivity distributions to minimize diffusion limitations and maximize air electrode material utilization. An interconnected dual pore system (one catalyzed and one non-catalyzed) is proposed to improve oxygen transport into the inner regions of the air electrode. but this approach alone cannot supply high power for long term applications. A time-release multiple catalyst approach is analyzed to provide temporal release of reactivity in the air electrode. When coupled with the dual pore configuration and catalysts with high reactivities, the time-release catalyst concept can extend the duration of higher powers to longer times, and result in maximum utilization of air electrode materials. (C) 2009 Elsevier B.V. All rights reserved.