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As the energy storage markets demand increased capacity of rechargeable batteries, Li metal anodes have regained major attention due to their high theoretical specific capacity. However, Li anodes tend to have dendritic growth and constant electrolyte consumption upon cycling, which lead to safety concerns, low Coulombic efficiency, and short cycle life of the battery. In this work, both conductive and non-conductive 3D porous hosts were coupled with a viscous (melt) polymer electrolyte. The cross-section of the hosts showed good contact between porous hosts and the melt polymer electrolyte before and after extensive cycling, indicating that the viscous electrolyte successfully refilled the space upon Li stripping. Upon deep Li deposition/stripping cycling (5 mAh cm-2), the non-conductive host with the viscous electrolyte successfully cycled, while conductive host allowed rapid short circuiting. Post-mortem cross-sectional imaging showed that the Li deposition was confined to the top layers of the host. COMSOL simulations indicated that current density was higher and more restricted to the top of the conductive host with the polymer electrolyte than the liquid electrolyte. This resulted in quicker short circuiting of the polymer electrolyte cell during deep cycling. Thus, the non-conductive 3D host is preferred for coupling with the melt polymer electrolyte. 

Solid-state single-ion conducting polymer electrolytes have drawn considerable interest for secondary lithium batteries due to their potential for high electrochemical stability and safety, but applications are limited by their low ionic conductivities. Specifically, poly(ethylene oxide) (PEO) based electrolytes have the highest reported Li + conductivities for these materials; however, their potential is limited due to the ion transport mechanism being coupled to segmental relaxations of the cation solvating polymer chain. To investigate the potential of single-ion conducting polymer electrolytes lacking polar matrices, we synthesized three para -polyphenylene-based, side-chain polymer electrolytes with various pendent anion chemistries (–SO 3 − , –PSI − , and –TFSI − ) with differing binding affinities to Li + . Compared with the previously reported lithium poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide) (LiPSTFSI), the side-chain polymers showed at least 3 orders of magnitude higher conductivity with the same –TFSI − anion (6.7 × 10 −6 S cm −1 compared with 1.2 × 10 −10 S cm −1 at 150 °C). We found that the side-chain electrolyte showed a dielectric relaxation dominated transport mechanism through use of dielectric spectroscopy analysis. The conductivity is highly dependent on the charge delocalization and size of the pendent anion, which provides a pathway forward for the engineering of polymeric ion conductors for electrochemical applications. 

As wastewater reclamation and reuse technologies become more critical to meeting the growing demand for water, a need has emerged for separation platforms that can be tailored to accommodate the highly varied feed water compositions and treatment demands of these technologies. Nanofiltration (NF) membranes based on copolymer materials are a promising platform in this regard because they can be engineered at the molecular scale to address an array of separation process needs. Here, for example, a resilient NF membrane is developed through the design of a poly(trifluoroethyl methacrylate- co -oligo(ethylene glycol) methyl ether methacrylate- co -glycidyl methacrylate) [P(TFEMA-OEGMA-GMA)] copolymer that can be dip-coated onto hollow fiber supports. By exploiting the microphase separation of the oligomeric ethylene glycol side chains from the copolymer backbone and by elucidating the processing–structure–property relationships for the dip-coating process, membranes with pores 2 nm-in-diameter that exhibit a hydraulic permeability of 15.6 L m −2 h −1 bar −1 were generated. The GMA repeat units were functionalized post-coating with hexamethylene diamine to incorporate positively-charged moieties along the pore walls. This functionality resulted in membranes that rejected 98% of the MgCl 2 from a 1 mM feed solution. Moreover, the reaction with the diamine crosslinked the copolymer such that the membranes operated stably in ethanol, an organic solvent that damaged the unreacted parent membranes irreparably. Finally, the stability of the crosslinked P(TFEMA-OEGMA-GMA) copolymer resulted in membranes that could operate continuously for a 24 hour period in aqueous solutions containing 500 ppm chlorine without exhibiting signs of structural degradation as evidenced by consistent rejection of neutral probe solutes. These results demonstrate how resilient, charge-selective NF membranes can be fabricated from microphase separated copolymers by engineering each of the constituent repeat units for a directed purpose.