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Membrane‐based gas separation technologies are one solution towards mitigating global emissions of CO2. New membrane materials with improved separation performance are still highly sought after. Composite membranes based on organic ionic plastic crystals (OIPCs) have shown preferential interaction for CO2 over N2, leading in some cases to competitive CO2/N2 selectivities. However, these ionic materials have been scarcely studied in the field of gas separation. Here, OIPCs based on the bis(trifluoromethylsulfonyl)imide ([TFSI]−) anion were investigated for use as gas separation membranes for the first time. The effect of the polymer type was also investigated, through the comparison of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride)‐hexafluoropropylene (PVDF‐HFP) OIPC membranes. A strong temperature dependence of the gas separation performance was found, particularly in the N‐methyl‐N‐ethylpyrrolidinium‐based composites where the material undergoes a solid‐solid phase transition within the testing temperature range. The polymer type was noted to induce a strong effect on the structure of the composites, as well as affecting the gas and ionic transport. Thus, this research provides insights on the influence of the [TFSI]− anion on the structure and separation properties of OIPC‐based composites, and new information towards the development of novel OIPC‐based membranes with enhanced gas separation performance. [ABSTRACT FROM AUTHOR]

Sodium batteries are promising alternatives to state-of-the-art lithium batteries, owing to the cheaper resources and more sustainable materials. To realise this promise, the requirement for electrochemically and thermally stable electrolytes with low volatility and flammability to enable high-performance sodium batteries is crucial. In this work, we reported a unique family of salts through the synthesis of tris(amino)phosphonium cations [P1(DEA)3]+ and pairing with [FSI]− and [TFSI]− anions. The unique organic ionic plastic crystal (OIPC) [P1(DEA)3][FSI] displays high ionic conductivity which is several orders of magnitude greater than that of its counterpart [P1(DMA)3][FSI]. Electrolytes composed of 50 mol% NaFSI in [P1(DEA)3][FSI] showed a high conductivity value of 1.6 × 10−2 S cm−1 at 50 °C. The electrolyte supports stable Na plating/stripping with a small overpotential of 70 mV at 0.5 mA cm−2 with 2 h polarization. This electrolyte exhibits a satisfactory performance in sodium metal full cells (Na metal and NaFePO4 electrodes) with a stable cycling performance of 125 mA h g−1 at C/10, a high capacity retention of ∼80% after 112 cycles and a coulombic efficiency close to 99.5%. [ABSTRACT FROM AUTHOR]

There is an urgent need for more efficient technologies to mitigate climate change, such as the separation and capture of CO2 from flue gas. This work explores light gas separation based on a series of novel Organic Ionic Plastic Crystals (OIPCs) and polymer composites with the advantage of competitive and tuneable performance. Five OIPCs based on the bis(fluorosulfonyl)imide ([FSI]−) anion were selected and co-cast with poly(vinylidene fluoride) (PVDF) or poly(ethylene oxide) (PEO). Their gas transport properties were evaluated at temperatures where some of the OIPCs exist in different thermal phases. It was found that the nature of the polymer has a strong impact on separation performance, with PVDF demonstrating more advantageous properties than PEO. However, every OIPC has a different response to a given polymer type and ratio. A remarkable increase in permeability, from ∼100 to ∼360 Barrer, was achieved for triethyl(methyl)phosphonium bis(fluorosulfonyl)imide ([P1222][FSI])-based composites upon increasing the PVDF ratio, while preserving high selectivity (α ≈ 29). Additionally, large changes in separation performance were observed in OIPCs that undergo a solid–solid phase transition. A shift from phase II to phase I resulted in a dramatic increase in permeability (from ∼12 to ∼500 Barrer) for hexamethylguanidinium bis(fluorosulfonyl)imide ([HMG][FSI])-based composites. Analysis of the relationship between structure and transport properties of the different composites reveals insights into the effect of different OIPC and polymer chemistries and points to promising new directions in the development of highly permeable and selective gas separation membranes. [ABSTRACT FROM AUTHOR]

Solid electrolyte composites between organic ionic plastic crystals (OIPCs) and polymers can potentially show enhanced mechanical properties and ion conduction. These properties can be determined by the formation of interfacial regions which affect the structure, thermal properties, and ion transport of the composite material. Here we studied the properties of composites between the OIPC hexamethylguanidinium bis(fluorosulfonyl)imide (HMGFSI) and acrylate polymer nanoparticles functionalised with lithium, using various techniques including solid-state NMR spectroscopy. An enhancement in ionic conductivity of three orders of magnitude as well as increased lithium and OIPC cation and anion dynamics were observed in the composite as prepared with 40 v% of polymer nanoparticles with respect to the pure OIPC at 50 °C. This was attributed to the increased overall structural disorder as a result of the formation of disordered interfacial regions, which were evidenced by solid-state NMR spectroscopy. In addition, the importance of the thermal history of these composites is highlighted, with differences in the conductivity and ion dynamics observed after melting and recrystallizing the OIPC component, leading to less disordered interfacial regions. This study enriches our fundamental understanding of the formation of interfacial regions in OIPC composites and their effect on the bulk properties of the electrolyte., (© 2024 Wiley-VCH GmbH.)