As the aircraft industry becomes more committed to sustainable aviation, hybrid-electric propulsion systems containing batteries with higher specific energy have attracted attention as a means to reduce fuel consumption. Future aircraft could benefit from next-generation chemistries like oxide-based solid-state Li battery (SSB) technologies. However, producing and evaluating a wide range of design parameters for maximizing the specific energy of SSB experimentally is both time- and resource-intensive. Physics-based modeling promises to identify optimal designs for battery cells with respect to high specific energy in a more time and cost-efficient manner. Here, we applied a pseudo-two-dimensional model for the model-based evaluation of Li-SSB with various (hybrid) electrolytes to elucidate which solid electrolyte performs well with present electrode technology and which one has the potential to become an attractive alternative with more development. After identifying design variables to improve SSB with the help of sensitivity analysis, a genetic algorithm is used to predict the optimal design parameters to achieve higher specific energy. The study reveals that SSB based on 12.7 vol% of LLZTO is the best option under present manufacturing constraints. Hybrid electrolytes based on 10 wt% of LATP could be promising for future aircraft with further improvements in SSB manufacturing process.

The use of novel battery technologies in short-haul electric aircraft can support the aviation sector in achieving its goals for a sustainable development. However, the production of the batteries is often associated with adverse environmental and socio-economic impacts, potentially leading to burden shifting. Therefore, this paper investigates alternative technologies for lithium-sulfur all-solid-state batteries (LiS-ASSBs) in terms of their contribution to the sustainable development goals (SDGs). We propose a new approach that builds on life cycle sustainability assessment and links the relevant impact categories to the related SDGs. The approach is applied to analyze four LiS-ASSB configurations with different solid electrolytes, designed for maximum specific energy using an electrochemical model. They are compared to a lithium-sulfur battery with a liquid electrolyte as a benchmark. The results of our cradle-to-gate analysis reveal that the new LiS-ASSB technologies generally have a positive contribution to SDG achievement. However, the battery configuration with the best technical characteristics is not the most promising in terms of SDG achievement. Especially variations from the technically optimal cathode thickness can improve the SDG contribution.A sensitivity analysis shows that the results are rather robust against the weighting factors within the SDG quantification method.

All-solid state lithium polymer batteries are promising next-generation batteries with high safety and energy density. Their success depends on an improved design with a tailored cathode manufacturing process. To facilitate a knowledge-driven optimal design of the cathode, a model-based analysis on the impact of the cathode particle structure on the electrochemical cell performance wais conducted. During production of solid-state cathodes, small active material particles such as lithium-iron phosphate tend to form large agglomerates with inner electrolyte-filled pores which have significant effect on transport properties within a secondary particle. Therefore, a battery cell model with secondary particles and optionally with a core-shell structure was developed and evaluated. Discharge performance was shown to be more strongly impacted by changing the electrolyte fraction inside the particle than by changing the size of the electrolyte core within the secondary particle. A core-shell structure has a positive impact on the discharge performance and should be preferred for high power application. In contrast, cells with homogeneous agglomerate particles show better performance at low discharge rates. Thus, they are recommended for high energy and low power applications. The results of this study highlight the potentials of tailored production process for next-generation batteries.

There is a growing interest in the sustainability of the aviation industry sector over the past years due to the environmental issues associated with traditional aviation engines. Electric and hybrid aircrafts are considered promising technologies for reducing fuel consumption and enhancing system efficiency [1]. However, electrical energy storage systems require a higher capacity-to-weight ratio than today’s Li-ion batteries to fulfil the high demands in this area. Safety restrictions imposed by liquid electrolytes motivate the development of next-generation chemistries, such as oxide-based all-solid-state batteries (ASSB) for aviation, which have non-flammable electrolytes [2]. This option is investigated in the context of the IMOTHEP European project that aims at identifying promising hybrid aircraft configurations and studying the associated technology. However, the major drawbacks of oxide-based solid electrolytes are weak contact between electrode and electrolyte interface, low mechanical flexibility, and high density, which limit their use for high gravimetric energy density applications. To mitigate the aforementioned concerns, the solid polymer composite electrolytes approach could be applied, where oxides are mixed with polymer electrolytes [3]. Designing an optimum cell without ion transport limitations using experimental investigations is time- as well as resource-intensive due to the large number of iterations in production and evaluation required to achieve a well-performing design. Physics-based modelling is able to create a platform that can directly assess the impact of cell structure on battery performance and provide knowledge concerning limiting processes within the cell. Therefore, we here present the first study that combines a pseudo-two-dimensional model for the model-assisted evaluation of Li-ASSB with various hybrid electrolytes and single-ion conductor electrolytes with an evolutionary algorithm to identify optimum cell designs to reach a higher gravimetric energy density (see Fig. 1-a). To this end, we first compared the performance of several hybrid electrolytes with their experimental properties, to identify which electrolyte performs well with present technology and which has the potential to become an attractive alternative in the future. Our findings reveal that based on available ASSB technology, single ion-conducting electrolytes cannot achieve a higher gravimetric energy density than hybrid electrolytes at low current rates due to their high density, as shown in Fig. 1-b. ASSB based on 12.7 vol% of garnet Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is the best option based on present manufacturing constraints. Furthermore, our study revealed that hybrid electrolytes based on 10 wt% of Li1.3Al0.3Ti1.7(PO4)3 (LATP) could be promising for future aircraft if researchers succeed to decrease its electrolyte thickness and chemical stability in contact with lithium metal anode. Further, sensitivity analyses enabled us to identify that the cathode thickness and volume fraction of cathode materials are critical parameters for the cell design of ASSB. Therefore, we applied a global optimisation to enhance gravimetric energy density by changing these two electrode design parameters. After optimisation, gravimetric and volumetric energy densities of 618 Wh kg-1 and 1251 Wh L-1 for 0.1C discharge are achieved, respectively, indicating that the cell with the optimal electrode design could meet the mission demand in the aviation industry with a gravimetric energy density of 500 Wh kg-1 and volumetric energy density of 1000 Wh L-1. In conclusion, the findings of this study show that our physics-based modelling in conjunction with an optimisation algorithm predicts the optimal composition of ASSB for a given constraint and thus supports the time- and cost-effective development of batteries that fulfil mission requirements, e.g. in the aviation sector. This work is conducted in the frame of the project IMOTHEP (Investigation and Maturation of Technologies for Hybrid Electric Propulsion), which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 875006 IMOTHEP. References: M. Tariq, A. I. Maswood, C. J. Gajanayake, and A. K. Gupta, IECON Proc. (Industrial Electron. Conf. 4429 (2016). J. Hoelzen, Y. Liu, B. Bensmann, C. Winnefeld, A. Elham, J. Friedrichs, and R. Hanke-Rauschenbach, Energies 11, 1 (2018). G. Piana, F. Bella, F. Geobaldo, G. Meligrana, and C. Gerbaldi, J. Energy Storage 26, 100947 (2019). S.Toghyani, , F. Baakes, N. Zhang, H. Kühnelt, W. Cistjakov, U. Krewer, J. Electrochem. Soc (2022). Figure 1