Polymer electrolyte membrane fuel cell (PEMFC) electrodes with a 0.07 mg Pt cm −2 Pt/Vulcan electrocatalyst loading, containing only a sulfonated poly(ionic liquid) block copolymer (SPILBCP) ionomer, were fabricated and achieved a ca. 2× enhancement of kinetic performance through the suppression of Pt surface oxidation. However, SPILBCP electrodes lost over 70% of their electrochemical active area at 30% RH because of poor ionomer network connectivity. To combat these effects, electrodes made with a mix of Nafion/ SPILBCP ionomers were developed. Mixed Nafion/SPILBCP electrodes resulted in a substantial improvement in MEA performance across the kinetic and mass transport-limited regions. Notably, this is the first time that specific activity values determined from an MEA were observed to be on par with prior half-cell results for Nafion-free Pt/Vulcan systems. These findings present a prospective strategy to improve the overall performance of MEAs fabricated with surface accessible electrocatalysts, providing a pathway to tailor the local electrocatalyst/ionomer interface.
This review presents the mechanisms, challenges, strategies, and perspectives in the interface engineering of inorganic-based solid-state Li metal batteries.
Styrene-based poly(ionic liquid) (PIL) diblock copolymers and their analogous PIL homopolymers were synthesized in this study with various covalently attached cations (methylimidazolium (MIm + ) and methylpyrrolidinium (MPyr + )) and counteranions (bis(trifluoromethanesulfonyl)imide (TFSI − ) and bis(fluorosulfonyl)imide (FSI − )). Solid polymer electrolytes (SPEs) were prepared by mixing the polymer with the corresponding salts (Li + TFSI − and Li + FSI − ) under various salt concentrations r = [Li + ]/[PIL] (mol/mol) = 0.1−0.8. The impacts of lithium salt concentration and cation/anion chemistry were explored in regards to electrochemical, morphological, transport, and physical properties. The results show that the SPE with the MIm + /FSI − ion pair has the lowest PIL T g (−7 °C), ca. 1−3 orders of magnitude higher conductivity compared to other SPEs as well as high electrochemical stability (lithium−metal stripping-plating). SPEs with the FSI − anion exhibit an ion-hopping-dominated transport mechanism and similar ion conductivities compared to their analogous PIL homopolymer SPEs at the same salt concentrations. The negative transference number of the SPE with the MIm + /TFSI − ion pair at a high salt concentration indicates the formation of larger anion-rich clusters and results in lower conductivity. This work reveals the impact of cation/anion chemistries on salt-doped PIL block polymers, which may enable new highly stable SPEs for lithium batteries.
Inorganic solid‐state electrolyte (SSE) based Na‐metal batteries have received extensive attention in next‐generation lithium‐free energy storage systems with both high‐security and superior electrochemical performance. Herein, in contrast to the conventionally used polymer/ceramic/polymer sandwich electrolyte, an efficient green and scalable powder‐polishing synthetic method is developed to fabricate a pyrolyzed‐polyacrylonitrile modified Na super ionic conductor (NASICON) electrolyte to relieve polarization of integrated composite SSE and ameliorate interfacial contact between the electrolyte and the Na anode. Furthermore, introducing S in the preferable isotropous sulfurized polyacrylonitrile (SPAN) interlayer can trigger dehydrogenation and cyclization of polyacrylonitrile with chemically‐bonded short‐chain SS segments, which can bond with Na+ to redistribute the interfacial electric field and homogenize transported Na+ flux, leading to transition of Na deposition behavior from dendrite growth mode to lateral flat‐shape growth tendency. The conjugated polymer backbones possess delocalized radicals that can activate formed short‐chain sulfides to reconnect to the backbones, thus maintaining superior structural stability. Benefiting from the rational interfacial design, a record‐high value of 1.4 mA cm−2 for critical current density of Na/SPAN‐NASICON/Na cells is obtained. Moreover, SPAN is used as a cathode to assemble solid‐state Na/SPAN‐NASICON/SPAN Na‐organosulfur batteries, demonstrating superior capacity and cycling‐stability. The rational SPAN‐based structural design strategy may provide an avenue for potential application of solid‐state alkali metal batteries.
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