Periodic Reporting for period 1 - SOLIFLY (Semi-SOlid-state LI-ion batteries FunctionalLY integrated in composite structures for next generation hybrid electric airliner)
Reporting period: 2021-01-01 to 2022-06-30
On the way to zero-emission aviation<\b>
Against the backdrop of climate change, air travel is coming under increasing criticism for its energy intensity and CO2 emissions. As aviation is likely to remain the fastest-growing transport sector, there is an urgent need for action, if aviation is to do its part in meeting the goal of climate neutrality by 2050 as enshrined in the European Green Deal.
Multifunctional components with integrated semi-solid-state battery<\b>
Shifting from fossil-fuel powered to increasingly electrical aircraft propulsion, electric energy storage systems that meet aeronautic requirements play a central role. Batteries with high energy density are needed that also meet the highest safety standards and cycle life under demanding charge and discharge and environmental conditions. The development of aviation-grade battery technologies and systems for passenger aircraft is currently still in its very early stages and is being driven forward in several European research projects with AIT’s participation (such as IMOTHEP, ORCHESTRA, HELENA).
The goal of the SOLIFLY project is to develop multifunctional structural components with integrated semi-solid-state batteries for aeronautical applications, thus making structural batteries a viable technology for the next generation of (hybrid) electric aircraft.
Two different scalable battery cell concepts are to be developed and combined: on the one hand, so-called Coated Carbon Fibres (CCF/carbon fibres coated with active material), which intrinsically store energy, and, on the other hand, thin battery cells that are installed into the carbon composite structure (Reinforced Multilayer Stack/RMS). Subsequently, both cell concepts will be scaled up to a representative aerospace-grade component (a stiffened panel) to demonstrate the electrochemical and mechanical properties of the developed structural battery technology.
Involvement of the aviation industry<\b>
An aspect that SOLIFLY focuses on is to closely link technological development to the actual needs of the aviation industry. To ensure this, the expectations and specifications of the aircraft manufacturers are incorporated into the design process from the very beginning, taking into account airworthiness and production requirements. A technology roadmap and a technology readiness level scale-up strategy are project outcomes which ensure that the inherently scalable processes can actually be industrialized.
Against the backdrop of climate change, air travel is coming under increasing criticism for its energy intensity and CO2 emissions. As aviation is likely to remain the fastest-growing transport sector, there is an urgent need for action, if aviation is to do its part in meeting the goal of climate neutrality by 2050 as enshrined in the European Green Deal.
Multifunctional components with integrated semi-solid-state battery<\b>
Shifting from fossil-fuel powered to increasingly electrical aircraft propulsion, electric energy storage systems that meet aeronautic requirements play a central role. Batteries with high energy density are needed that also meet the highest safety standards and cycle life under demanding charge and discharge and environmental conditions. The development of aviation-grade battery technologies and systems for passenger aircraft is currently still in its very early stages and is being driven forward in several European research projects with AIT’s participation (such as IMOTHEP, ORCHESTRA, HELENA).
The goal of the SOLIFLY project is to develop multifunctional structural components with integrated semi-solid-state batteries for aeronautical applications, thus making structural batteries a viable technology for the next generation of (hybrid) electric aircraft.
Two different scalable battery cell concepts are to be developed and combined: on the one hand, so-called Coated Carbon Fibres (CCF/carbon fibres coated with active material), which intrinsically store energy, and, on the other hand, thin battery cells that are installed into the carbon composite structure (Reinforced Multilayer Stack/RMS). Subsequently, both cell concepts will be scaled up to a representative aerospace-grade component (a stiffened panel) to demonstrate the electrochemical and mechanical properties of the developed structural battery technology.
Involvement of the aviation industry<\b>
An aspect that SOLIFLY focuses on is to closely link technological development to the actual needs of the aviation industry. To ensure this, the expectations and specifications of the aircraft manufacturers are incorporated into the design process from the very beginning, taking into account airworthiness and production requirements. A technology roadmap and a technology readiness level scale-up strategy are project outcomes which ensure that the inherently scalable processes can actually be industrialized.
In the first 18 months of the Project, the following progress has been made in the technical Work Packages (WPs):
WP1 – End-user requirements and specifications:
A state-of-the-art review on structural batteries and their application potential for aeronautics was delivered and published. The requirements for structural batteries for aeronautic applications were assessed with the active support of the industrial advisory board (Piaggio Aerospace, Pipistrel Vertical Solutions, FACC and Dassault Aviation). Structural batteries were analysed according to various perspectives, from electrochemical and mechanical/structural ones, considering the manufacturing processes, and airworthiness, certification and safety aspects. Performance evaluation criteria of structural batteries have been identified that will feed the decision-making process planned for the stage-gate. The results of this work package were presented and discussed with the AB in the WP1 Workshop.
WP2 – Battery: cell concepts, processing, performance, and prototype of the demo cells
Two different structural battery concepts are currently under development: Coated Carbon Fibers (CCF) by UNIVIE and Reinforced Multilayer Stack (RMS) by AIT. The electrochemical materials and components have been selected and initial tests on the compatibility and performance have been conducted, encountering some compatibility issues. AIT and UNIVIE investigated the feasibility of structural electrolytes with ionic liquid electrolytes together with epoxy or thermoplastic systems as reinforcing matrix, selecting the thermoplastic polymer approach as similar mechanical performance and even higher ionic conductivities can be expected. This approach is now further optimized to improve its mechanical and electrochemical stability. For both cell concepts, first electrode and full cell samples have been prepared and characterized electrochemically and mechanically.
WP3 – Structure: integration concept, scale-up, delivery of the structural battery demo and final performance assessment
The objective of the Work Package 3 is to develop concepts for the integration of battery cells into laminated composite structures in order to limit/control the decrease of the mechanical properties of Carbon/Epoxy composite structures compared to the reference one without any battery cell. ONERA has selected the structural element for demonstration, a stiffened panel constituted with a laminated composite material and performed its first structural design.
A numerical strategy to evaluate the integration of thin battery cells in solid laminate composites was implemented and a parametric study performed to evaluate the impact of the battery insert with respect to its size, shape and position on the mechanical performance of the structural part. Additionally to the macroscopic rigidity also the onset of damage within the laminate has been considered and first recommendations have been established.
To characterize the mechanical behaviour and the failure properties of the two battery cell concepts, first multi-instrumented measurements (with acoustic emission, digital image correlation, and SEM analysis after loading) have been performed on preliminary cell specimens. These result help tuning the numerical simulation.
WP1 – End-user requirements and specifications:
A state-of-the-art review on structural batteries and their application potential for aeronautics was delivered and published. The requirements for structural batteries for aeronautic applications were assessed with the active support of the industrial advisory board (Piaggio Aerospace, Pipistrel Vertical Solutions, FACC and Dassault Aviation). Structural batteries were analysed according to various perspectives, from electrochemical and mechanical/structural ones, considering the manufacturing processes, and airworthiness, certification and safety aspects. Performance evaluation criteria of structural batteries have been identified that will feed the decision-making process planned for the stage-gate. The results of this work package were presented and discussed with the AB in the WP1 Workshop.
WP2 – Battery: cell concepts, processing, performance, and prototype of the demo cells
Two different structural battery concepts are currently under development: Coated Carbon Fibers (CCF) by UNIVIE and Reinforced Multilayer Stack (RMS) by AIT. The electrochemical materials and components have been selected and initial tests on the compatibility and performance have been conducted, encountering some compatibility issues. AIT and UNIVIE investigated the feasibility of structural electrolytes with ionic liquid electrolytes together with epoxy or thermoplastic systems as reinforcing matrix, selecting the thermoplastic polymer approach as similar mechanical performance and even higher ionic conductivities can be expected. This approach is now further optimized to improve its mechanical and electrochemical stability. For both cell concepts, first electrode and full cell samples have been prepared and characterized electrochemically and mechanically.
WP3 – Structure: integration concept, scale-up, delivery of the structural battery demo and final performance assessment
The objective of the Work Package 3 is to develop concepts for the integration of battery cells into laminated composite structures in order to limit/control the decrease of the mechanical properties of Carbon/Epoxy composite structures compared to the reference one without any battery cell. ONERA has selected the structural element for demonstration, a stiffened panel constituted with a laminated composite material and performed its first structural design.
A numerical strategy to evaluate the integration of thin battery cells in solid laminate composites was implemented and a parametric study performed to evaluate the impact of the battery insert with respect to its size, shape and position on the mechanical performance of the structural part. Additionally to the macroscopic rigidity also the onset of damage within the laminate has been considered and first recommendations have been established.
To characterize the mechanical behaviour and the failure properties of the two battery cell concepts, first multi-instrumented measurements (with acoustic emission, digital image correlation, and SEM analysis after loading) have been performed on preliminary cell specimens. These result help tuning the numerical simulation.
In the first reporting period, and two structural battery cell concepts with energy dense active materials, i.e. CCF and RMS, are developed further by adopting a novel structural electrolyte based on thermoset polymers and ionic liquid electrolytes. A novel concept to integrate structural batteries into solid quasi-isotropic CF/epoxy UD laminates that are widely used in aeronautical industries is established and the structural element for demonstration, a large representative stiffened panel, has been devised.
In the second reporting period, the structural battery cell concepts wil be further optimized for their electrical/mechanical performance and scaled up for larger cell formats. Testing will be performed, first on coupons level and finally on the stiffened panel demonstrator.
The results of SOLIFLY will enable to evaluate better the potential of structural batteries for aeronautic applications and to identify the implications for further exploitation. The developed prototype will be evaluated against airworthiness, safety, and integration criteria for existing aircraft systems. Pathways for industrial scale-up will be identified and a plan for TRL step-up derived towards the adoption of the technology in the hybrid-electric aircraft.
In the second reporting period, the structural battery cell concepts wil be further optimized for their electrical/mechanical performance and scaled up for larger cell formats. Testing will be performed, first on coupons level and finally on the stiffened panel demonstrator.
The results of SOLIFLY will enable to evaluate better the potential of structural batteries for aeronautic applications and to identify the implications for further exploitation. The developed prototype will be evaluated against airworthiness, safety, and integration criteria for existing aircraft systems. Pathways for industrial scale-up will be identified and a plan for TRL step-up derived towards the adoption of the technology in the hybrid-electric aircraft.