TY - JOUR A1 - Baller, Johannes A1 - Hilger, André A1 - Qi, Naiyu A1 - Morini, Chiara A1 - Cornelio, Andrea A1 - Remhof, Arndt A1 - Osenberg, Markus A1 - Manke, Ingo A1 - Moosmann, Julian A1 - Beckmann, Felix A1 - Graeber, Gustav T1 - Wetting Interactions Between Porous Carbon Hosts and Liquid Sodium‐Potassium Alloys Toward Their Use in Negative Electrodes of Alkali‐Metal Batteries N2 - Batteries with liquid alkali‐metal negative electrodes offer a route to compact, high‐performance energy storage. Innovation in alkali‐metal management, i.e., controlled storage, release and transport of liquid alkali metal, can enable simpler and cheaper cell designs. Porous carbons have emerged as potential host materials for liquid alkali metals. Here, X‐ray computed tomography is used to study the wetting interactions between porous carbon hosts and liquid sodium‐potassium alloy (NaK) as a function of carbon host morphology and surface functionalization. While as‐received carbon samples show no affinity toward NaK, heat‐treated carbon is spontaneously infiltrated with NaK filling almost the entire pore volume. It is explored how forced wetting partially fills pores of NaK‐repellant hosts, showing large differences in pore filling based on the average pore size of the host material. In electrochemical discharge experiments, it is shown that both as‐received and heat‐treated carbon felt enable high areal capacities beyond 40 mAh cm−2. However, the heat‐treated carbon shows ten times lower overpotential. Finally, it is demonstrated how heat‐treated carbon felt can enable capillary transport of NaK. In summary, this study elucidates important aspects of the interactions between liquid alkali metals and porous carbon hosts, generating insights into possible applications in liquid alkali‐metal batteries. KW - Battery KW - Solid electrolyte KW - Sodium KW - Wetting PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-644663 DO - https://doi.org/10.1002/adfm.202523169 SN - 1616-301X SP - 1 EP - 10 PB - Wiley VHC-Verlag AN - OPUS4-64466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoogendoorn, Levi A1 - Huertas, Mauricio A1 - Nitz, Phillip A1 - Qi, Naiyu A1 - Baller, Johannes A1 - Prinz, Carsten A1 - Graeber, Gustav T1 - Sustainable, Low‐Cost Sorbents Based on Calcium Chloride‐Loaded Polyacrylamide Hydrogels N2 - AbstractSorbents are promising materials for applications in atmospheric water harvesting, thermal energy storage, and passive cooling, thereby addressing central challenges related to water scarcity and the global energy transition. Recently, hygroscopic hydrogel composites have emerged as high‐performance sorbents. However, many of these systems are fabricated with unsustainable and costly sorbent materials, which hinders their wide deployment. Here, the synthesis of high‐performance, cost‐efficient polyacrylamide hydrogels loaded with unprecedented amounts of calcium chloride is demonstrated. To this end, the swelling procedure of polyacrylamide hydrogels in aqueous calcium chloride solutions is optimized. The achievable salt loading in the hydrogel is characterized as a function of temperature, calcium chloride concentration in the swelling solution, and the hydrogel preparation conditions. The obtained hydrogel‐salt composites are shown to be stable under repeated sorption‐desorption cycling and enable water uptakes of 0.92 and 2.38 grams of water per gram of dry materials at 30% and 70% relative humidity, respectively. The resulting cost‐performance ratio substantially exceeds lithium chloride‐based systems. Further, the mechanistic insights on hydrogel salt interactions can guide the design of sustainable and low‐cost sorbent materials for future applications in water and energy. KW - Electrochemistry KW - Condensed Matter Physics KW - Biomaterials KW - Electronic, Optical and Magnetic Materials PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598366 DO - https://doi.org/10.1002/adfm.202314680 SN - 1616-301X SP - 1 EP - 10 PB - Wiley VHC-Verlag AN - OPUS4-59836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nitz, Phillip D. H. A1 - Rosaz, Paul A1 - Kreysina, Daniela A1 - Kasprzak, Dawid A1 - Qi, Naiyu A1 - Baller, Johannes A1 - Graeber, Gustav T1 - Water-in-Salt Electrolytes Embedded in Polyacrylamide Hydrogels: A First Step toward Deformable Sodium-Ion Batteries N2 - The development of flexible, safe, and sustainable Energy storage systems is critical for next-generation technologies, including wearable electronics, biomedical devices, and soft robotics. In this work, we provide a systematic investigation of sodium perchlorate-based water-in-salt (WIS) electrolytes embedded in polyacrylamide (PAM) hydrogels as a potential platform for deformable sodium-ion batteries or aqueous supercapacitors. Using Raman spectroscopy, we track the transition from free to intermediate water states with increasing salt concentration, identifying the onset of the WIS regime around 10 mol kg−1. Electrochemical measurements reveal that both the aqueous and hydrogel-based electrolytes exhibit a broadened electrochemical stability window (ESW) at higher salt concentrations, reaching up to 2.75 V. Impedance spectroscopy shows that while aqueous electrolytes achieve higher peak conductivity (156 mS cm−1), hydrogel-based electrolytes offer greater stability across a range of concentrations. This observation was supported by cyclic voltammetry, as it showed enhanced electrochemical stability of the PAM hydrogel compared to the aqueous electrolyte. This comprehensive and systematic study demonstrates that highly concentrated WIS electrolytes can be successfullyembedded into PAM hydrogels, while preserving good electrochemical stability and ionic conductivity. This could make them a promising foundation for all-hydrogel, sodium-based energy storage devices that are safe, sustainable, and mechanically compliant. KW - Battery PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-653156 DO - https://doi.org/10.1021/acsapm.5c03031 SN - 2637-6105 SP - 1 EP - 8 PB - American Chemical Society (ACS) AN - OPUS4-65315 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -