High-Energy-Density High-Power-Density Micro Aluminum-Air Batteries for Small Scale Quadcopters

Small-scale quadcopters are increasingly used in various fields, including rescue, surveillance and precision agriculture. The predominant energy storage system for such quadcopters has been the micro lithium-ion battery (mLIB). Two of the most important design metrics for power sources used in quadcopters are specific power and specific energy. The specific energy determines the flight duration of the quadcopters, while specific power is necessary for maneuverability and takeoff. The mLIB can easily meet the power requirement of small scale quadcopters; however, the limited energy density of mLIBs (exacerbated by the packaging overhead of these batteries as scales shrink) constrains their flight duration. To increase the flight time, aluminum-air batteries (AABs), with a theoretical energy density twenty times greater than conventional lithium-ion batteries, are being explored. [1] Despite AAB’s high theoretical energy density, the conventional AAB lacks the high-power performance of LIBs. [2] To fulfill the demanding power requirements of small scale quadcopters, the AAB cell has been re-engineered to enhance power capability while maintaining high energy density. To maximize AAB energy and power density at the cell level, it is imperative to address the issue of battery packages that add weight without contributing to electrochemical performance. A light-weight battery packaging approach is developed for the micro-AAB (mAAB). In the context of AABs, the primary function of the battery package is to retain the aqueous electrolyte within the cell. Typically, the cathode of an AAB is constructed using a carbon cloth, doped with a layer of polytetrafluoroethylene (PTFE). This hydrophobic carbon cloth cathode effectively retains the aqueous electrolyte. In order to increase the mechanical integrity of mAAB pouch cells, 3D printed polypropylene is utilized as the body frame of mAABs, providing a robust and lightweight structure. The carbon cloth cathode is affixed to the 3D printed polypropylene using epoxy, as shown in Figure 1A. An image of an assembled 2-gram mAAB pouch cell is shown in Fig 1B. Remarkably, the electrochemically inactive packaging materials contribute to less than 13% of the total cell weight, achieving the goal of minimizing packaging material to enhance battery performance. As a comparison, the packaging material of gram-scale mLIBs can contribute to over 30% of total cell weight. Furthermore, in contrast to traditional aluminum-air batte