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.
Within the era of battery technology, the urgent demand for improved and safer electrolytes is immanent. In this work, novel electrolytes, based on pyrrolidinium-bistrifluoromethanesulfonyl-imide polymeric ionic liquids (POILs), equipped with quadrupolar hydrogen-bonding moieties of ureido-pyrimidinone (UPy) to mediate self-healing properties were synthesized. Reversible addition–fragmentation chain-transfer (RAFT) polymerization was employed using S,S-dibenzyl trithiocarbonate as the chain transfer agent to produce precise POILs with a defined amount of UPy and POIL-moieties. Kinetic studies revealed an excellent control over molecular weight and polydispersity in all polymerizations, with a preferable incorporation of UPy monomers in the copolymerizations together with the ionic monomers. Thermogravimetric analysis proved an excellent thermal stability of the polymeric ionic liquids up to 360 °C. By combining the results from differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), and rheology, a decoupled conductivity of the POILs from glass transition was revealed. While the molecular weight was found to exert the main influence on ionic conductivity, the ultimate strength and the self-healing efficiency (of up to 88 %) were also affected, as quantified by tensile tests for both pristine and self-healed samples, evidencing a rational design of self-healing electrolytes bearing both hydrogen bonding moieties and low-molecular-weight polymeric ionic liquids.
We here demonstrate the preparation of composite polymer electrolytes (CPEs) for Li-ion batteries, applicable for 3D printing process via fused deposition modeling. The prepared composites consist of modified poly(ethylene glycol) (PEG), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and SiO2-based nanofillers. PEG was successfully end group modified yielding telechelic PEG containing either ureidopyrimidone (UPy) or barbiturate moieties, capable to form supramolecular networks via hydrogen bonds, thus introducing self-healing to the electrolyte system. Silica nanoparticles (NPs) were used as a filler for further adjustment of mechanical properties of the electrolyte to enable 3D-printability. The surface functionalization of the NPs with either ionic liquid (IL) or hydrophobic alkyl chains is expected to lead to an improved dispersion of the NPs within the polymer matrix. Composites with different content of NPs (5%, 10%, 15%) and LiTFSI salt (EO/Li+ = 5, 10, 20) were analyzed via rheology for a better understanding of 3D printability, and via Broadband Dielectric Spectroscopy (BDS) for checking their ionic conductivity. The composite electrolyte PEG 1500 UPy2/LiTFSI (EO:Li 5:1) mixed with 15% NP-IL was successfully 3D printed, revealing its suitability for application as printable composite electrolytes.
Vitrimers have been widely employed in self-healing, recyclable, and shape-shifting materials. However, the application of catalyst-free vitrimers to create self-healable and mechanically robust gel polymer electrolytes (GPEs) remains a challenge, often limiting the potential of vitrimer-based materials. Herein, we utilized a catalyst-free dynamic covalent bond (silyl ether) as a linkage to prepare self-healable and mechanically robust GPEs, which are fully reprocessable. By incorporating polymeric ionic liquids into the dynamically cross-linked networks, both ion conductivity and mechanical properties can be flexibly tuned. The dynamic property of the network was demonstrated through frequency sweep rheology, which revealed a rubbery-like behavior at high frequencies and a liquidlike behavior at low frequencies. This dynamic feature enables self-healing and allows for reprocessing via embedding of such dynamic covalent networks into the GPEs. The GPEs containing 80 wt % of a bis(trifluoromethansulfonamide) lithium/ionic liquid (LiTFSI/IL) mixture exhibited good ion conductivites of 0.13 mS/cm at 20 °C and 1.88 mS/cm at 80 °C. Furthermore, the elastic modulus of the GPEs could reach a value of 0.24 MPa and was able to persist through electrode-volume expansions during charging/discharging.The tunable dynamic properties, coupled with high ion conductivity and a high modulus, indicate promising applications for this type of dynamic bond in sustainable solid electrolytes.
Vitrimeric PILs: conductive, reprocessable, self-healable, 3D-printable material as promising electrolyte for Li-ion batteries.
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