02Free Newsletter – Agost 2022

02Free Newsletter – Agost 2022

O2FREE Newsletter - August 2022

 O2FREE is now at the 20th month since it started, which is the home stretch of this 2-year project. After most of the material developments carried out and the battery casing, structure and cabling designed, the final assembly and testing will take place in the last 4 months.



This month, one of the main challenges of the project has been achieved: to assemble a full battery pack to run the shock and vibration tests. These tests enable to evaluate the resistance of the battery to the possible shocks during taxiing, landing, sudden gusts in a flight. Thanks to the close collaboration of the three partners and the hard and intense work done, especially during the last 3 months, Leitat could prepare the cathodes so that Albufera assembled the cells and built the modules. Finally, Sonaca integrated the modules into the structural casing and run the tests (see figure).

A total of 100 cells have been assembled to run the test. The rest of the casing was filled with dummy cells to obtain the equivalent weight of the real ones. The complete analysis of the battery is currently on going, but the preliminary results show no visual damage on the casing, neither suspect noise nor additional gap at each interface. The monitored voltage of the battery only suffered some small variations, which indicates the battery is still able to discharge, even after the endured shocks and vibrations. This would mean that the battery would be able to absorb the oxygen of the ambient air in an airplane, as initially expected.


Next steps

The next tasks of the project include environmental tests of small modules, which will consist of discharging the battery in different conditions of temperature, pressure, and gas atmosphere, while monitoring the oxygen concentration. These tests will give a first insight of the battery behavior before the final fire tests. In parallel, some carbon nanofiber cathodes, made by electrospinning, will be upscaled, so that some prototypes can be built as demonstration of an Al-air cell with innovative materials.


Upcoming Events

  •  Battery Innovation Days, 13-14 September 2022
  •  4th Graz Battery Days, 19-21 September 2022
  •  European Sustainable Energy Week, 26-30 September 2022
  •  Energy Storage Global Conference, 11-13 October 2022
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About the project

O2FREE project aims to develop and validate an Al-air primary battery with high O2 absorption rate for cargo compartment inertisation during ETOPS time. During discharge, metal-air batteries consume oxygen from the surrounding air and thus have the capability to extract oxygen and inert the ambient air. Oxygen absorption capability is directly coupled to the power capacity of a metal-air battery (Ah), and this is currently the limiting factor for realizing such application. A major focus of the O2FREE project is on increasing the power performance of Al-air technology through the development of advanced anode and cathode materials for Al-air cells and optimization of the module configuration.

Metal-air batteries are inherently a safe and reliable technology. Moreover, aluminium is the third most abundant element in the earth’s crust, highly recyclable and non-flammable. Thus, O2FREE delivers a safe, lightweight and environmentally friendly technology free of critical raw materials with high recycling potential. All these advantages are aligned with European Union policies for airborne sustainability.

O2FREE project will be carried out by three partners with extensive knowledge and experience in the energy storage and aerospace sectors covering the full value chain for this project. LEITAT and AES have been working for years in the development of post Li-ion battery technologies including metal-air systems and are specialized in electrochemical processes, technology optimization through the development of novel materials and components, as well as module design and integration. SON is expert in structural design and manufacturing for the aerospace sector and will leverage their expertise for turning this technology into a product that meets the stringent requirements for installation and operation of this type of battery in future aircrafts.

Al-air shows the overall best trade-off for performance, lightweight, safety and reliability versus Zn-air and Li-air while also being the most mature technology of the non-commercial metal-air technologies. O2FREE proposes the development of metal-air fire suppression battery based on Al-air technology. As shown in the Figure 1, Al-air battery is composed on porous air cathode where the ORR (oxygen absorption) takes place, aluminium anode (alloyed with other metals in order to supress the Al-corrosion) and electrolyte between them that acts as an ionic conductor. O2FREE propose to use a proved high performant and cheap commercial alloys, improving the Al utilization and its resistance to high current ranges thanks to the addition of different additives. Moreover, the project will develop a Carbon nanofiber-base cathode that will increase the fire gasses tolerance of the cell. Finally, O2FREE will develop an electrolyte able to work at high range of temperature and pressure with the addition of some additives that will help to supress the al corrosion.

Review Meeting 02Free (June ’22)

Review Meeting 02Free (June ’22)

On 28rd and 29th June, the O2Free project consortium meet face-to-face and discuss technical matters.

In addition, the consortium was able to visit the facilities of DFactory, a member of O2Free. A very interesting and rewarding visit.

Review Meeting (November ’21)

Review Meeting (November ’21)

On the 23rd and 24th November, the O2Free project consortium finally had the opportunity to meet face-to-face and discuss technical matters.

In addition, the consortium was able to visit the facilities of Sonaca, a member of O2Free. A very interesting and rewarding visit.


Current progress on the preparation of Al-air battery cathode

Current progress on the preparation of Al-air battery cathode

Current progress on the preparation of Al-air battery cathode

Carbon nanofibers (CNFs) free-standing film are being developed as cathode of the Al-air battery. These CNFs are obtained by electrospinning. Electrospinning is the procedure of adopting electrostatic forces to pull a polymer solution jet to produce nanofibers. Under the action of electrostatic field, the droplet of polymer solution at the tip of the tube deforms into a cone (Taylor cone). When the electrostatic force is higher than the surface tension, the charged jet is ejected and it moves to a ground plate regarded as a counter electrode, where the non-woven nanofibers are collected forming a mat. Different collectors can be used, but in our case, we normally use a rotatory collector. Schematic procedure and our electrospinnings are showed in Figure 1.

Figure 1. Schematic procedure of electrospinning process (left) and electrospinning equipment at LEITAT (right).

There are some parameters that can be modulated to change the properties of the final nanofibers, as the operating voltage, viscosity, the flowrate or the rotation speed.

The CNFs are obtained after the application of a specific thermal treatment to the PNFs, consisting in two steps:

  • First a stabilization step where the thermoplastic chain molecule is transformed into a non-meltable ladder polymer by cyclization, dehydrogenation, and oxidation.
  • During subsequent carbonization in a non-oxidizing atmosphere, oxygen and the heterocyclic nitrogen are split off and planar polyaromatics are formed, giving place to a more graphitised material with an increased electrical conductivity.

Figure 2 shows the final CNFs used as cathodes for this project our tubular furnace in which we obtain the final material.

Figure 2. CNF mat (left) and tubular furnace used at LEITAT for the synthesis of the CNF mats.