3D printing of solid polymer electrolytes by fused filament fabrication: challenges towards in-space manufacturing

A new chapter of space exploration is opening with future long-duration space missions toward the Moon and Mars. In this context, the European Space Agency is developing out-of-the-earth manufacturing abilities, to overcome the absence of regular supplies for astronauts' vital needs (food, health, housing, energy). Additive manufacturing is at the heart of this evolution because it allows the fabrication of tailorable and complex shapes, with a considerable ease of process. Fused filament fabrication (FFF), the most generalized 3D printing technique, has been integrated into the International Space Station to produce polymer parts in microgravity. Filament deposition printing has also a key role to play in Li-ion battery (LIB) manufacturing. Indeed, it could reduce manufacturing cost & time, through one-shot printing of LIB, and improve battery performances with suitable 3D architectures. Thus, additive manufacturing via FFF of LIB in microgravity would open the way to in-space manufacturing of energy storage devices. However, as liquid and volatile species are not compatible with a space station-confined environment, solvent-free 3D printing of polymer electrolytes (PEs) is a necessary step to make battery printing in microgravity feasible. This is a challenging stage because of a strong opposition between the mechanical requirements of the feeding filament and electrochemical properties. Nowadays, PE manufacturing remains a hot topic and lots of strategies are currently being studied to overcome their poor ionic conductivity at room temperature. This work firstly gives a state of the art on the 3D printing of LIBs by FFF. Then, a summary of ionic conduction mechanisms in PEs permits to understand the several strategies studied to enhance PEs performances. Thanks to the confrontation with the specifications of FFF printing and the microgravity environment, polymer blends and composite electrolytes turn out to be the most suitable strategies to 3D print a lithium-ion polymer battery in microgravity.