The effects of carbon microstructure and loading on the performance of Li/air batteries were investigated. We found that the capacities of Li/air batteries were related to both the specific capacity per unit weight of the carbon source (mAhnormalg−1) and the carbon locating per unit area (gcm−2) . Therefore, the product of these two parameters [i.e., the area-specific capacity (mAhcm−2) ] was introduced to optimize the performance of the air electrode. At the fixed electrolyte amount (100μL/cell) , the best area-specific capacity of 13.1mAhcm−2 was obtained at a carbon loading of 15.1mgcm−2 . Further increase or decrease in the carbon loading led to a reduced area-specific capacity. The capacities of air electrodes increased with increasing mesopore volumes of the carbon sources. The uniformity of the pore sizes also played an important role in determining the electrochemical performances of the Li/air batteries. At fixed carbon loading and discharge rates, the capacity increased significantly with increasing electrolyte amounts. This phenomenon was explained by the formation of extra triphase regions in the air electrodes. After optimizing the electrode and electrolyte parameters, a high capacity of 1756mAhnormalg−1 carbon was obtained for Li/air batteries operated in ambient oxygen pressure (0.21 atm).

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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 timerelease catalyst concept can extend the duration of higher powers to longer times, and result in maximum utilization of air electrode materials.