Innovative Strategy for Developing PEDOT Composite Scaffold for Reversible Oxygen Reduction Reaction.

Metal-air batteries are an emerging technology with great potential to satisfy the demand for energy in high-consumption applications. However, this technology is still in an early stage, facing significant challenges such as a low cycle life that currently limits its practical use. Poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer has already demonstrated its efficiency as catalyst for oxygen reduction reaction (ORR) discharge as an alternative to traditional expensive and nonsustainable metal catalysts. Apart from that, in most electrochemical processes, three phenomena are needed: redox activity and electronic and ionic conduction. Material morphology is important to maximize the contact area and optimize the 3 mechanisms to obtain high-performance devices. In this work, porous scaffolds of PEDOT-organic ionic plastic crystal (OIPC) are prepared through vapor phase polymerization to be used as porous self-standing cathodes. The scaffolds, based on abundant elements, showed good thermal stability (200 °C), with potential ORR reversible electrocatalytic activity: 60% of Coulombic efficiency in aqueous medium after 200 cycles.

All-Polymer Nanocomposite as Salt-Free Solid Electrolyte for Lithium Metal Batteries.

Solid polymer electrolytes that combine both a high lithium-ion transference number and mechanical properties at high temperatures are searched for improving the performance of batteries. Here, we show a salt-free all-polymer nanocomposite solid electrolyte for lithium metal batteries that improves the mechanical properties and shows a high lithium-ion transference number. For this purpose, lithium sulfonamide-functionalized poly(methyl methacrylate) nanoparticles (LiNPs) of very small size (20-30 nm) were mixed with poly(ethylene oxide) (PEO). The morphology of all-polymer nanocomposites was first investigated by transmission electron microscopy (TEM), showing a good distribution of nanoparticles (NPs) even at high contents (50 LiNP wt %). The crystallinity of PEO was investigated in detail and decreased with the increasing concentration of LiNPs. The highest ionic conductivity value for the PEO 50 wt % LiNP nanocomposite at 80 °C is 1.1 × 10-5 S cm-1, showing a lithium-ion transference number of 0.68. Using dynamic mechanic thermal analysis (DMTA), it was shown that LiNPs strengthen PEO, and a modulus of ≈108 Pa was obtained at 80 °C for the polymer nanocomposite. The nanocomposite solid electrolyte was stable with respect to lithium in a Li||Li symmetrical cell for 1000 h. In addition, in a full solid-state battery using LiFePO4 as the cathode and lithium metal as the anode, a specific capacity of 150 mAhg-1 with a current density of 0.05 mA cm-2 was achieved.

Mixed Conductive, Injectable, and Fluorescent Supramolecular Eutectogel Composites.

Eutectogels are an emerging family of soft ionic materials alternative to ionic liquid gels and organogels, offering fresh perspectives for designing functional dynamic platforms in water-free environments. Herein, the first example of mixed ionic and electronic conducting supramolecular eutectogel composites is reported. A fluorescent glutamic acid-derived low-molecular-weight gelator (LMWG) was found to self-assemble into nanofibrillar networks in deep eutectic solvents (DES)/poly(3,4-ethylenedioxythiophene) (PEDOT): chondroitin sulfate dispersions. These dynamic materials displayed excellent injectability and self-healing properties, high ionic conductivity (up to 10-2  S cm-1 ), good biocompatibility, and fluorescence imaging ability. This set of features turns the mixed conducting supramolecular eutectogels into promising adaptive materials for bioimaging and electrostimulation applications.

Facile Access to CO2 -Sourced Polythiocarbonate Dynamic Networks And Their Potential As Solid-State Electrolytes For Lithium Metal Batteries.

Poly(monothiocarbonate)s are an interesting class of sulfur-containing materials whose application as solid polymer electrolytes was barely studied, certainly due to the elusive production of diversified polymer architectures. Herein, a new liquid CO2 -sourced bis(α-alkylidene cyclic carbonate) monomer was designed at high yield to allow its one-step and solvent-free copolymerization with thiols to produce linear and cross-linked polymers in mild conditions. The influence of the monomer structure on the thermal properties and the ionic conductivity of linear polymers was assessed. The polymer network showed to be thermally re-processable owing to the dynamic nature of the monothiocarbonate bonds. A solid polymer electrolyte was easily obtained from the cross-linked material when combined with LiTFSI salt. The solid polymer electrolyte was characterized by an ionic conductivity reaching 6×10-6  S cm-1 at room temperature with a lithium transference number of 0.37 and a wide electrochemical stability window (4.0 V vs Li0 /Li+ ) valid for lithium cycling. This work thus reports an attractive valorizing approach for carbon dioxide to deliver under mild operating conditions poly(monothiocarbonate)-containing novel covalent adaptable network materials of high potential for energy applications, especially as solid electrolytes for batteries.

Mixed Ionic-Electronic Conductors Based on PEDOT:PolyDADMA and Organic Ionic Plastic Crystals.

Mixed ionic-electronic conductors, such as poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) are postulated to be the next generation materials in energy storage and electronic devices. Although many studies have aimed to enhance the electronic conductivity and mechanical properties of these materials, there has been little focus on ionic conductivity. In this work, blends based on PEDOT stabilized by the polyelectrolyte poly(diallyldimethylammonium) (PolyDADMA X) are reported, where the X anion is either chloride (Cl), bis(fluorosulfonyl)imide (FSI), bis(trifluoromethylsulfonyl)imide (TFSI), triflate (CF3SO3) or tosylate (Tos). Electronic conductivity values of 0.6 S cm-1 were achieved in films of PEDOT:PolyDADMA FSI (without any post-treatment), with an ionic conductivity of 5 × 10-6 S cm-1 at 70 °C. Organic ionic plastic crystals (OIPCs) based on the cation N-ethyl-N-methylpyrrolidinium (C2mpyr+) with similar anions were added to synergistically enhance both electronic and ionic conductivities. PEDOT:PolyDADMA X / [C2mpyr][X] composites (80/20 wt%) resulted in higher ionic conductivity values (e.g., 2 × 10-5 S cm-1 at 70 °C for PEDOT:PolyDADMA FSI/[C2mpyr][FSI]) and improved electrochemical performance versus the neat PEDOT:PolyDADMA X with no OIPC. Herein, new materials are presented and discussed including new PEDOT:PolyDADMA and organic ionic plastic crystal blends highlighting their promising properties for energy storage applications.