Structural batteries for aeronautic applications: The promise of zero weight penalty energy storage

Electrification of aircraft propulsion is one key enabler to cut emissions from aviation and meeting the EU Green Deal target of carbon neutral air travel by 2050. While batteries enable highest energy efficiency, their rather low energy density will remain the bottle neck, even with maturing Li-ion technology. Multifunctional electrical energy storage, equivalently referred to as structural batteries capable of storing electrical energy while bearing mechanical loads, could overcome this energy density limit of conventional, monofunctional batteries, as they offer integration of energy storage at near-to-zero weight penalty. So far none of the many structural battery concepts investigated over the last decades has shown multi-functional efficiency adequate for aeronautic applications, and several gaps in research, technology development and in airworthiness certification have never been tackled.
This paper presents the progress in two EU-funded research projects, SOLIFLY and MATISSE, targeting structural battery technology for aerospace applications and its potential for aircraft electrification. Structural battery electrochemistry based on energy dense active material, and cell and structural integration concepts have been developed and demonstrated, allowing projections that improved technology could double the effective system-level energy density of monofunctional batteries, significantly reducing the battery weight penalty, the main barrier to the introduction of batteries for larger aircraft.