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Metal-air battery integration for cargo compartment fire suppression

Periodic Reporting for period 2 - O2FREE (Metal-air battery integration for cargo compartment fire suppression)

Reporting period: 2021-12-01 to 2022-11-30

Today, most aircraft still use Halon-based fire suppression systems for cargo compartment inertisation following a fire event. Halon 1301 is a very effective fire extinguishing agent. However, it is also a harmful substance with high ozone depletion potential. The use of halon for critical applications including aviation is being phased out, and will be completely banned by 2040 as set out in the Montreal Protocol. There is a need for innovative, lightweight and more environmentally friendly fire suppression solutions for the aerospace sector.

O2FREE project aimed at developing and assembling an Al-air battery that can be used as a new fire suppression system. The oxygen is absorbed by the battery as it is involved in the discharge chemical reaction, allowing an efficient, low cost and safe way to replace the current fire suppression systems.

The objective of the project was to demonstrate the feasibility of the Al-air battery technology for this application by assembling and testing a battery prototype of 12 kAh in real environment at the Topic Manager’s facilities.

Although the final device could not be assembled, it was demonstrated that the devices tested prior to scaling up showed an acceptable efficiency to achieve the objectives established in the project. The critical points of the cathode component were identified, allowing significant learnings that enable the improvement of the yields obtained.
During this first year of the project, the 3 partners involved (Sonaca, Albufera and Leitat) have developed a scheme of the electrochemical characteristics that the developed battery must present at unit, cell and module level, and of the requirements of the external module of the battery. Starting materials for the anode and electrolyte have been selected for the development of the battery. These have been adapted and selected to meet the requirements defined in the case of having to work with commercial cathodes. Development of an improved air cathode made by electrospinning and testing of its electrochemical compatibility with the other components has been carried out. Design and stress analysis of the battery modules and structural casings have been done.
In the second and last year of the project, work has continued to develop an own cathode, but due to the results obtained, it has been decided to switch to the commercial component for device testing and real test conditions. When trying to scale the device, it was necessary to identify a new commercial cathode material due to the discontinuation of the previously planned commercial cathode. This material was analyzed in parallel to the construction of the test devices. The results showed that despite very similar characteristics, the new commercial cathode material did not meet the expected and necessary requirements. To try to identify the reasons for this difference, both components were characterized to determine the causes of the difference in results.
New aqueous gel electrolyte has been developed, enabling to discharge for more than 7 hours the Al-air battery cell from -20 to 85ºC, which is a wider Al-air battery temperature range (currently [-10; 60ºC]). The necessary requirements to achieve the established values at the laboratory level have been demonstrated by yielding performances capable of meeting the initial requirements. On the other hand, there is still room for improvement in process and material optimization, leading to future new opportunities to improve current values and have a wider range of applications.
Carbon nanofibers (HRSEM image)
Carbon nanofibers (photo)
Schematic setup for the electrospinning process (left) and equipment (right)
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