Printable Electrolytes: Tuning 3D‐Printing by Multiple Hydrogen Bonds and Added Inorganic Lithium‐Salts

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.

3D Printable Composite Polymer Electrolytes: Influence of SiO2 Nanoparticles on 3D-Printability

“…PEG 8000 B 2 /LiTFSI (5:1) ( 8 ) showed a more distinct glass transition temperature at 22 °C and the absence of a melting peak, which is a characteristic behavior of amorphous structures. The increasing concentration of LiTFSI salt is supposedly hindering the formation of lamellar structures, thus preventing crystallization as previously reported in the literature for similar PEG/salt compositions [ 28 , 40 ]. With the obtained information about thermal transitions 3D printability was investigated above T m /T g for all compositions.…”

“…This is defined by the geometry of the printing needle together with the geometry and the temperature of the storage tank and the transfer line between. These rheological borders are well established, and have repeatedly been proven by us [ 20 , 28 , 38 , 41 ].…”

“…Before the rheological measurements the thermal properties of polymers were investigated by using differential scanning calorimetry (DSC). PEG 1500 UPy 2 /LiTFSI was previously investigated showing no melting transition, indicating the absence of crystallinity [ 28 ]. For the PEG 8000 B 2 based compositions DSC curves were recorded form −15 °C to 170 °C and are presented in Figure 5 .…”

“…Previously we reported that PEG 1500 UPy 2 as such is not suitable for 3D printing in our 3D-printer without the use of additional fillers [ 28 ]. Figure 8 represents the rheological measurements of PEG 1500 UPy 2 /LiTFSI now containing either NP – IL ( 2 , 3 , 4 ) or the NP – OH ( 5 , 6 , 7 ), showing increased viscosity and also linear behavior of shear vs viscosity.…”

“…Recently, we presented a profound investigation on the factors influencing the printability of SPE electrolytes containing quadrupole (UPy)-hydrogen bonds and lithium salts [ 28 ]. We have shown that both, the self-healing property and the printability of the telechelic UPy-PEO/PPO-UPy polymer can be tuned not only by temperature, an already known tool for adjusting melt-rheology, but also by variation of the salt content, which consequently influences the crystallinity of the polymer.…”