While electrodes have been 3D printed the researchers were able to print a stable, yet flexible, solid-state electrolyte using an elevated-temperature extrusion printing technique. This allows for the production and customisation of batteries much more quickly and cheaply because all parts are printed together at once. This differs from lithium-ion batteries where the electrodes have been 3D-printed, the conventionally produced electrolyte has always been added afterward in a separate step.
In conventional solid-state electrolyte production, battery casings need to be prepared with various coatings and solvents used in the production of the electrolyte which then must be evaporated away in a post-production step. If an electrolyte is printed directly into a forming 3D-printed battery, evaporation would cause the electrolyte to shrink and pull away from the electrodes. This could cause the battery to short out. Coatings used to ensure the electrolyte makes good contact with the casings and electrodes are also extremely difficult to incorporate into a 3D-printed battery.
To get around these problems, Reza Shahbazian-Yassar, associate professor, and Yayue Pan, assistant professor of mechanical and industrial engineering in the College of Engineering designed a 3D printer that works at an elevated temperature. It extrudes materials at around 120ºC compared with traditional extrusion 3D printing, which takes place at room temperature. Their solid-state electrolyte ink is made up of a polymer base containing titanium oxide particles that allow it to be flexible and directly deposited into the battery as it is being printed.
“The high temperature prevents post-production shrinkage,” said Meng Cheng, a graduate student in the UIC College of Engineering and lead author of the study. “Our technique dramatically improves the efficiency of the preparation of the electrolyte and its incorporation into the battery."
"The elevated-temperature direct writing and our specialized inks is the proof-of-concept that 3D-printed lithium-ion batteries are possible,” said Reza.