To achieve a significant reduction of greenhouse gas emissions until 2050, the development of full electric and hybrid electric propulsion technologies is crucial. Given the high energy demands of long-range flights, fully electric propulsion may not be feasible for long-haul air travel. However, for regional and short-range flights, as well as for transport drones, electric solutions present promising opportunities. Addressing the energy storage limitations in these applications requires reducing parasitic mass and volume through the multifunctional design of energy storage components: So-called structural battery composites can store electrical energy while bearing mechanical loads.
In this study, the electrical energy storage is enabled in fiber reinforced composites commonly used for load-bearing parts in aircraft design by substituting the epoxy resin with the materials of an all-solid-state battery. The research focuses on the production and characterization of carbon fiber-based structural electrodes and glass fiber-based structural separators. To prepare structural cathodes, a slurry composed of lithium iron phosphate (LFP), polyethylene oxide (PEO), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and carbon black was coated on carbon fiber textiles. The impact of the fibre reinforcement on the ionic conductivity of structural separators prepared by melt infiltration of glass fiber textiles with a PEO- and LiTFSI-based electrolyte was investigated by EIS measurements. Specific capacities over 110 mAh g^{-1}_{LFP} demonstrate good utilisation of the active material in cells with structural cathode and separator. At low areal loadings of 1.2 mAh cm^{-2}, an excellent capacity retention of 94 % was achieved after 100 cycles at 0.1C. The areal loading could be increased up to 2.6 mAh cm^{-2} without a significant decrease of the active material utilisation, however, the capacity fading increased. Based on these results, a structural battery composite demonstrator was produced at pouch cell level by embedding of the cell stack in epoxy resin. With respect to electrode and separator a mass power density of 64 Wh kg^{-1} was achieved.