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Single-ion lithium conducting polymer electrolytes based on delocalized borate groups have been designed and synthesized by rapid UV-photopolymerisation. For this purpose, three different functional lithium boron sp3 anionic monomers, containing fluorinated, ethoxy, or a blend of both functionalities have been synthesized. These monomers were photopolymerized in the presence of a PEG-di-acrylate crosslinker and tetraglyme as plasticizer. By this method, gel polymer electrolytes (SIPEs) endowed with lithium single-ion conduction were prepared. The impact generated by the different functionalities of the borate groups and the addition of plasticizer on the electrochemical and ion conducting properties of the synthesized polymer electrolytes are analyzed in detail. These polymer electrolytes showed high ionic conductivity (1.71·10 -4 S·cm-1 at 25 °C) and high lithium transference number values (up to 0.85). Finally, they were investigated as solid electrolytes in lithium metal symmetrical cells showing good performance (<0.85 V at ±0.2 mA·cm-2 for 175 h).

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.

Current electrolytes for lithium batteries are usually composed of at least two chemical compounds, an organic solvent such as a cyclic carbonate and a lithium salt such as LiPF6. Here, the concept of using a single-component electrolyte is demonstrated in lithium batteries based on new lithium borate ionic liquids at room temperature. The design concept of this class of lithium ionic liquids (LiILs) is based on an asymmetrically substituted central tetracoordinate boron atom with oligoethylene glycol groups, fluorinated electron-attracting groups, and one alkane group. The optimized borateLi+ LiILs show a high ionic conductivity value of >10−4 S cm−1 at 25 °C, high lithium transference numbers ( = 0.4 – 0.5) and electrochemical stability (>4 V). Some of the LiILs present high compatibility with lithium-metal electrodes showing stable polarization profiles in platting/stripping tests. The selected LiIL is investigated as single-component electrolytes in lithium-metal battery cells showing discharge capacity values in Li0/LiIL/lithium–iron phosphate and Li0/LiIL/lithium titanate cells of 124 and 75 mAh g−1, respectively, at a C-rate of 0.2 C and 65 °C with low-capacity loss.

[EN] Natural deep eutectics solvents (NADES), owing to their high solvation capacity and nontoxicity, are actively being sought for many technological applications. Herein, we report a series of novel NADES based on choline chloride and plant-derived polyphenols. Most of the obtained phenolic NADES have a wide liquid range and high thermal stability above 150 degrees C. Among them, small-sized polyphenols, like pyrogallol, vanillyl alcohol, or gentisic acid, lead to low-viscosity liquids with ionic conductivities in the order of 10(-3) S cm(-1) at room temperature. Interestingly, polyphenols possess valuable properties as therapeutic agents, antioxidants, adhesives, or redox-active compounds, among others. Thus, we evaluated the potential of these novel NADES for two applications: bioadhesives and corrosion protection. The mixture of choline chloridevanillyl alcohol (2:3 mol ratio) and gelatin resulted in a highly adhesive viscoelastic liquid (adhesive stress approximate to 135 kPa), affording shear thinning behavior. Furthermore, choline chloride-tannic acid (20:1) showed an extraordinary ability to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies in mild steel protection.

Single-ion lithium conducting polymer electrolytes based on delocalized borate groups have been designed and synthesized by rapid UV-photopolymerisation. For this purpose, three different functional lithium boron sp3 anionic monomers, containing fluorinated, ethoxy, or a blend of both functionalities have been synthesized. These monomers were photopolymerized in the presence of a PEG-di-acrylate crosslinker and tetraglyme as plasticizer. By this method, gel polymer electrolytes (SIPEs) endowed with lithium single-ion conduction were prepared. The impact generated by the different functionalities of the borate groups and the addition of plasticizer on the electrochemical and ion conducting properties of the synthesized polymer electrolytes are analyzed in detail. These polymer electrolytes showed high ionic conductivity (1.71·10 -4 S·cm-1 at 25 °C) and high lithium transference number values (up to 0.85). Finally, they were investigated as solid electrolytes in lithium metal symmetrical cells showing good performance (<0.85 V at ±0.2 mA·cm-2 for 175 h).

Unformatted postprint, Iongels are soft ionic conducting materials, usually comprised of polymer networks swollen with ionic liquids (ILs), which are being investigated for applications ranging from energy to bioelectronics. The employment of iongels in bioelectronic devices such as bioelectrodes or body sensors has been limited by the lack of biocompatibility of the ILs and/or polymer matrices. In this work, we present iongels prepared from solely biocompatible materials: i) a biobased polymer network containing tannic acid as a crosslinker in a gelatin matrix, and ii) three different biocompatible cholinium carboxylate ionic liquids. The resulting iongels are flexible and elastic with Young’s modulus between 11.3 and 28.9 kPa. The morphology of the iongels is based on a dual polymer network system formed by both chemical bonding due to the reaction of the gelatin’s amines with the polyphenol units and physical interactions between the tannic acid and the gelatin. These biocompatible iongels presented high ionic conductivity values, from 0.003 and up to 0.015 S*cm-1 at room temperature. Furthermore, they showed excellent performance as conducting gel in electrodes for electromyography recording as well as muscle stimulation.

Lithium-O2 batteries represent one of the most appealing candidates for battery electric vehicles (BEV) due to its remarkable theoretical high energy density, similar to fossil fuels. Solid polymer electrolytes represent a plausible solution to tackle some of the challenges associated to conventional liquid-based Li-O2 batteries, including safety concerns. Herein, cross-linked robust gel polymer electrolytes (GPE) based on poly(ethylene glycol) dimethacrylate (PEGDM) and tetraethylene glycol dimethyl ether (TEGDME) as plasticizer are prepared by rapid UV-photopolymerization. Both types of robust GPEs presented high ionic conductivity at room temperature (1.6·10−4 S·cm−1 and 1.4·10−3 S·cm−1 for single ion or dual ion, respectively). Both types of GPEs, single ion and dual ion lithium conductors, have been compared for the first time on Li-O2 cells. First, their performance was investigated in symmetrical Li|Li cells. In this case, the dual-ion GPE showed an outstanding behavior where the overpotential was <0.2 V vs Li0/Li+ for more than 40 hours at a current density as highs as ±1 mA·cm−2. On the other hand, in full Li-O2 configuration, the single ion GPE cell showed superior discharge capacity, up to 2.38 mAh·cm−2. A dynamic discharge characterization technique is proposed here as a method for evaluating the polarization effect in electrolytes during discharge in an easy, quantifiable and reproducible manner.

This communication reports a family of single-ion lithium conducting polymer electrolytes based on highly delocalized borate groups is reported. The effect of the nature of the substituents on the boron atom on the ionic conductivity of the resultant methacrylic polymers was analyzed. To the best of our knowledge the lithium borate polymers endowed with flexible and electron-withdrawing substituents presents the highest ionic conductivity reported for a lithium single-ion conducting homopolymer (1.65×10−4 S cm−1 at 60 °C). This together with its high lithium transference number tLi+= =0.93 and electrochemical stability window of 4.2 V vs Li0/Li+ show promise for application in lithium batteries. To illustrate this, a lithium borate monomer was integrated into a single-ion gel polymer electrolyte which showed good performance on lithium symmetrical cells (<0.85 V at ±0.2 mA cm−2 for 175 h).

Unformatted postprint, Solid-state lithium batteries are considered one of the most promising battery systems due to their high volumetric energy density and safety. Poly(ethylene oxide) (PEO) is the most commonly used solid polymer electrolyte in solid-state batteries. In this article, we introduce new polyphosphoester polymer electrolytes, which show improved flame retardant properties in comparison with PEO. For this purpose, new polyphosphoester copolymers were synthesized, including phosphoester, poly(ethylene glycol) (PEG) and UV cross-linkable vinyl units. Solid polymer electrolytes films based on polyphosphoesters copolymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared by curing under UV-light. The crystallinity present in the copolymers due to the PEG segmentdecreases with the amount of salt in the electrolyte, as seen by DSC. Solid polymer electrolytes based on polyphosphoester copolymers show ionic conductivity values as high as 2·10-4 S cm-1 at 70 °C. FTIR analysis showed that lithium cations complexed with phosphoester groups provoked an increase in the lithium transference number to 0.26 as compared to that of PEO 0.17. Pyrolysis flow combustion calorimetry (PCFC) or microcalorimetry results demonstrated the improved flame retardancy of the polyphosphoesters in comparison to a reference PEO based polymer electrolyte. The selected polyphosphoester solid electrolyte was investigated in a solid-state lithium cell Li0/Polymer electrolyte/LFP battery showing a specific capacity retention close to 80% and coulombic efficiency greater than 98% among 100 cycles at 70 °C.