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  1. Sulfide solid-state electrolyte (SE) possesses high room-temperature ionic conductivity. However, fabrication of the free-standing, sheet-type thin sulfide SE film electrolyte to enable all-solid-state batteries to deliver high energy and power density remains challenging. Herein we show that argyrodite sulfide (Li6PS5Cl) SE can be slurry cast to form free-standing films with low (≤5 wt%) loadings of poly(isobutylene) (PIB) binder. Two factors contribute to a lower areal specific resistance (ASR) of the thin film SEs benchmarked to the pristine powder pellet SSE counterparts: i) 1–2 orders reduced thickness and ii) reasonably comparable ionic conductivity at room temperature after the isostatic pressing process. Nevertheless, an increasing polymer binder loading inevitably introduced voids in the thin film SEs, compromising anode/electrolyte interfacial ion transport. Our findings highlight that electrolyte/electrode interfacial stability, as well as the selection of slurry components, including sulfide SE, binder, and solvent, play essential roles in thin film sulfide electrolyte development.

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  2. Commodity PS is synthesized via free radical polymerization, whereas PS in block copolymers (BCPs) is typically synthesized via living anionic polymerization. The purpose of this work is to investigate how the synthesis method impacts important properties such as water sorption and glass transition temperature (Tg). Water sorption is important because the performance of nanostructured polymer membranes in various applications is known to be affected by environmental conditions such as humidity. Tg is important because it dictates processing conditions, both for commodity PS as well as BCPs such as thermoplastic elastomers. Water sorption in commercial PS was found to be 0.5 mgwater/gpolymer at the highest humidities investigated (about 80%), in agreement with literature. On the other hand, syndiotactic PS synthesized anionically at low temperature absorbed more water, up to 1.5 mgwater/gpolymer, due to higher free volume. The greatest impact on water sorption was due to addition of hydrophilic hydroxyl chain ends to atactic PS, which resulted in water sorption of up to 2.3 mgwater/gpolymer. In addition to measuring water sorption and dry Tg separately, the impact of relative humidity on PS Tg was examined. Combined differential scanning calorimetry and dynamic mechanical analysis show that on going from the dry state to high humidity, the Tg of PS decreases by 5 °C. Moreover, the tensile storage modulus of PS decreases from 1.58 GPa at 0% RH to 0.53 GPa at 40% RH. In addition to the practical relevance of this study, this report fills a gap in experimental literature by using a poor solvent system, PS/water, to examine plasticization in the pure polymer limit. 
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  3. A novel precision single-ion conductor with phenylsulfonyl(trifluoromethylsulfonyl)imide lithium salt covalently bound to every fifth carbon of a polyethylene backbone, p5PhTFSI-Li, was synthesized via ring opening metathesis polymerization (ROMP) followed by post polymerization modification. The conversion of poly(4-phenylcyclopentene), bearing 94% sulfonate anions, to trifluoromethanesulfonimide (TFSI) anions was highly efficient (∼90%) as determined by 19 F NMR analysis and corroborated through other spectroscopic methods. The flexible hydrocarbon backbone combined with a bulky TFSI anion led to an observable glass transition temperature of 199 °C even at these high levels of ionization. A high thermal stability up to 375 °C was also observed. Blending of p5PhTFSI-Li with poly(ethylene oxide) at various compositions was performed to investigate electrochemical performance and transference numbers with respect to the lithium electrode using a combination of impedance and polarization methods. At 90 °C and a 50 : 50 wt% blend composition, this system displayed the highest reported conductivity (2.00 × 10 −4 S cm −1 ) of a system with a demonstrated lithium-ion transference number near unity. Such performance is also atypical of single ion conductors produced through post-polymerization modification, which we attribute to the high yield of TFSI conversion. Investigations into the complex miscibility and phase behavior of these blends at various compositions was also probed by a combination of microscopy and differential scanning calorimetry, which is discussed with reference to computational predictions of how charge correlations affect polymer blend phase behavior. 
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  4. Hydrolytic degradation of commercially available 3D printing filament, i.e. poly (lactic acid) with broad molecular weight distribution was induced by incubating 3D-printed parts in deionized water at 3 temperatures. Small changes in orthogonal dimensions occurred due to relaxation of printing stresses, but no mass or volume loss were detected over the time-frame of the experiments. Molecular weight decreased while polydispersity remained constant. The most sensitive measure of degradation was found to be nondestructive, small-amplitude oscillatory tensile measurements. A rapid decay of tensile storage modulus was found with an exponential decay time constant of about an hour. This work demonstrates that practical monitoring of commercially available PLA degradation can be achieve with linear viscoelastic measurements of modulus. 
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    The Soret effect results in a concentration gradient when a mixture is exposed to a temperature gradient. It is a balance between diffusion of mass driven by the temperature gradient (thermal diffusion) and mass diffusion acting to remove the concentration gradient. Thus, the Soret effect is measured at steady state. In this work, the Soret effect was studied in a thermogalvanic cell with lithium metal electrodes and a dry polymer electrolyte composed of poly(ethylene oxide) and lithium bis-trifluoromethanesulfonylimide (LiTFSI). The concentration gradient was determined by measuring the voltage of the thermogalvanic cell. This was examined at several different temperature gradients and with four different salt concentrations. The Soret coefficient was found to be similar to that observed in small-molecule mixtures and electrolytes and significantly less than polymeric systems. An explanation for this unexpected result is proffered. The Soret coefficient was found to be concentration dependent, which requires further investigation. Finally, it was demonstrated that the thermogalvanic cells used to measure the Soret coefficient can also be used to generate power. Thus, polymer electrolytes are potentially of interest for waste heat recovery, and thermal diffusion might be used to improve battery efficiency. 
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