Researchers improve load-bearing aircraft structures with integrated batteries

Until now, batteries in electric aircraft have generally been installed as a box-shaped battery pack in the fuselage. A European consortium has spent three years researching multifunctional aircraft structures in which batteries are already integrated to reduce weight and increase efficiency.

The European research project SOLIFLY (Semi-SOlid-state LI-ion Batteries FunctionalLY Integrated in Composite Structures for Next Generation Hybrid Electric Airliners), led by the Austrian Institute of Technology (AIT), has successfully reached its final phase. The research institute reports that “significant progress has been made in the field of aviation electrification”, during the three years of development research.

SOLIFLY focused on the development of special aircraft parts that perform two functions at once. Load-bearing structures in the aircraft are simultaneously capable of energy storage. The researchers explain, “the simultaneous storage of electrical energy and the preservation of mechanical strength contribute to a reduction in system weight.”

The project can celebrate the development of an approach to integrate structural battery cells into aviation-grade, high-strength carbon composite components. The researchers say this is now possible without compromising their mechanical properties. The potential of this approach was demonstrated in the multifunctional project demonstrator, a high-strength, stiffened panel that the researchers chose as a representative standard component. According to the AIT, its findings proved that the integration of energy storage systems is compatible with the high mechanical requirements in aviation.

The research teams involved have identified “load-bearing semi-solid-state electrochemistry” as a key element in the implementation of such multifunctional energy storage systems. The non-flammable, structural electrolyte plays a key role here. At the same time, the rest of the cell formulation must also be compatible with the structural materials and manufacturing processes recognised in aviation. Two concepts were developed as part of SOLIFLY. After the first development phase, the first concept has been created with a specific energy of 50 Wh/kg and a modulus of elasticity of 10 GPa. A series of larger, multi-layer structural battery cells were produced for the multifunctional project demonstrator. The second concept uses carbon fibres both as a structural element and as a current collector. The researchers say this variant is currently less mature, particularly in terms of electrical performance and scalability.

“With SOLIFLY, we have demonstrated that integrating battery technology into structural components is possible without significantly compromising their mechanical properties,” says AIT researcher and SOLIFLY coordinator Helmut Kühnelt. “This is a crucial step for multifunctional energy storage as a key technology for future climate-neutral aviation. Through close collaboration between applied research and industry, we ensured that our developments are both pioneering and practical,” he summarised.

The conclusion of SOLIFLY has informed the next focal points for continuing research work at AIT. In January this year, the follow-up project MATISSE started with a focus on developing multifunctional, structural components with an integrated semi-solid-state battery. To integrate the battery cells into the aircraft structure, the researchers want to investigate the suitability of solid laminate and sandwich structures, for example. In addition, sensors are to be built directly into the battery and the structure to measure safety and performance.

ait.ac.at