Printable Electrolytes: tuning 3D printing by multiple hydrogen bonds and added inorganic lithium-salts (LiTFSI)

Abstract

Here, the 3D-printing of supramolecular polymer electrolytes is reported, able to be manufactured via 3D-printing processes, additionally dynamically compensating for volume changes. A careful mechanical design, in addition to rheological effects observed for different additives to the electrolyte, is investigated and adjusted, in order to achieve printability via an extrusion process to generate a conductive electrode material. Qudruple-hydrogen bonds (UPy) act as supramolecular entities for the desired dynamic properties to adjust printability, in addition to added LiTFSi-salts to achieve ionic conductivities of ≈10^–4 S cm^–1 at T = 80 °C. Three different telechelic UPy-PEO/PPO-UPy-polymers with molecular weights ranging from Mn = 600–1500 g mol⁻¹ were investigated in view of their 3D-printability by FDM-processes. It is found that there are three effects counterbalancing the rheological properties of the polymers: besides temperatures, which can be used as a known tool to adjust melt-rheology, also the addition of lithium-salts in junction with the polymers crystallinity exerts a major toolbox to 3D-print these electrolytes. Using specific compositions with Li/EO-ratios from 20:1, 10:1, and 5:1, the rheological profile can be adjusted to reach the required printability window. AT-IR-investigations clearly indicate a weakening of the UPy-bonds by the added Li⁺ ions, in addition to a reduction of the crystallinity of the PEO-units, further changing the rheological profile. The so generated electrolytes are printable systems for novel electrolytes.