Three Ways Electrified Aerospace and eVTOL are Redefining Battery Design
As electrified aircraft move from fantasy to reality, they will demand ever more rigorous performance from batteries. These battery demands differ from the requirements of a car or a cell phone.
For instance, an electric airplane on takeoff requires an enormous burst of power that is sustained only briefly—until the aircraft reaches the desired cruising altitude. Those same batteries must also meet the very different demands of gradually and predictably discharging over the course of a long flight. On top of that, every gram of added battery weight becomes a critical factor in aircraft performance.
These different, and sometimes opposing, requirements pose a challenge for battery designers. Designing a battery to deliver energy as quickly as possible means aiming for high power density. But developing a battery to sustain energy for as long as possible to meet the demands of maintaining a flight at altitude means aiming for high energy density. And all of these design choices must be implemented in the lightest possible way.
1 - Lightweighting Batteries is Critical
Weight is so critical a factor in flight that it underlies all aspects of electrified aircraft battery design. The days of heavy lead batteries are long gone, which is just as good for weight as it is for power. Battery researchers are exploring innovative materials that may serve dual purposes: providing structural support and storing energy.
These innovative batteries can fit into very tight spaces and are densely packed throughout an aircraft.
Along with aiming for lightweight batteries, designers are also planning for both high energy density and high power density.
2 - Designing for High Energy Density
Designing batteries for high energy density seeks to pack as much energy as possible per unit volume, which means densely packed cells that maximize space utilization. These densely packed cells use high-capacity materials and thicker electrodes, which hold more active material and, therefore, more energy.
But thicker electrodes also introduce more resistance to heat transfer. In high-energy-density batteries, thermal management can take place over a comparably longer time frame than in high-power-density batteries, but heat buildup must still be handled effectively.
Adhesives and coatings are primary tools battery designers use to mitigate thermal buildup. High-energy-density battery design requires tight cell spacing, especially for 21700-series cylindrical lithium-ion cells. This tight spacing generates a lot of heat. Thermally conductive adhesives channel heat from cells to heatsink. Thermally conductive adhesives also provide structural integrity, enabling batteries to withstand vibration.
Thermally conductive adhesives and thermal interface materials transfer heat away from densely packed cells
Thermal interface materials (TIMs) also combat thermal buildup.
Battery designers seeking custom adhesives, coatings, and TIMs will often start a conversation with a team of H.B. Fuller scientists and engineers. Design engineers typically have a specific thermal conductivity and thermal resistance number they need to accommodate. H.B. Fuller scientists take those numbers into account, along with cell density and even the adhesive application process, to develop a solution that enables the battery designer to meet the aircraft’s needs.
3 - Designing for High Power Density
Designing a battery for high power density means delivering high current without overheating. Vertical takeoff (eVTOL) is especially demanding on the power sources of electrified aircraft.
Designing for high power density means optimizing materials for low resistance and faster electrochemical reactions, while paying special attention to heat removal. Design tactics include small cell spacing, thinner electrodes, and a robust busbar for high-current power distribution. Another design choice might be to provide more space for a robust cooling infrastructure.
Thermally conductive adhesives may be used alongside extensive TIM use to help regulate thermal gradients and maintain consistent performance. Adhesives, coatings, and sealants must accommodate both high energy density and high power density by providing thermal conductivity to remove heat. But they also help insulate between large, efficient busbars.
“It is very important to have a high level of electrical insulation when it comes to adhesives, potting materials, and coatings in battery packs,” said Schloegl. “To make sure that there are no arcs or unwanted conductive paths between tabs of cells or tabs of submodules.” Arcs or conductive paths can lead to corrosion later and are dangerous at high voltages.
Other Design Considerations
Electrified aircraft batteries must perform well in extreme temperatures, requiring coatings that provide insulation.
“The materials around the battery pack in an electric vehicle, for example, typically have a temperature range between minus 40degrees C to 80 degrees C, whereas the operating temperatures for an airplane can go much lower, typically -55 or -60 degrees C.
Battery design must also accommodate the need to protect from splash contamination.
Battery design is a complex set of practices that include science, art, and a team of diverse experts. Lessons learned from designing electrified aircraft and eVTOL will inevitably make their way back to all battery designers.
Link:https://www.hbfuller.com/en/blog/thegluetalkblog/2025/december/three-ways-electrified-aerospace-and-evtol-are-redefining-battery-design
