Ionic Network Research Articles

The Stable 3D Zn Electrode for High-Power Density Zn Metal Batteries

A stable Zn metal electrode can develop rechargeable zinc metal batteries (RZMBs) which have the high theoretical capacity (820 mAh g−1), low redox potential, and intrinsic safety. However, the corrosion of Zn metal in aqueous electrolytes and Zn dendrite formation during the plating process lead to poor cycling and thus hinder the development of RZMBs. Here, we employed ionic liquid-based gel polymer (poly(vinylidene fluoride)-co-hexafluoropropylene, PVDF-HFP) and acetylene black (AB) to achieve a stable and flexible three-dimensional (3D) Zn/AB/PVDF-HFP film electrode with ionic and electronic conductive networks and high surface area, showing 26 times higher plating/stripping current than planar Zn plate. By developing a continuous structure between the ionic liquid-based gel polymer membrane and the flexible 3D Zn/AB/PVDF-HFP electrode, the low resistance, high rate capability and long cycle life (> 800 h) was obtained. Our work shows a flexible Zn film electrode and ionic liquid-based gel polymer electrolyte, could pave the path for rechargeable and high-cycle life thin-film RZMBs.

Endeavour to balance mechanical properties and self-healing of nature rubber by increasing covalent crosslinks via a controlled vulcanization

Introducing covalent crosslinks into reversible supramolecular networks would effectively improve their mechanical strengths, but sacrificed the desired self-healing effect. So, it is a practical significance to explore the influence of irreversible covalent crosslinks on self-healing behavior to prepare self-healing rubbers with enhanced mechanical properties for further application. In this study, the trade-off of covalent crosslinks between the balanced mechanical properties and self-healing effect of a natural rubber/methacrylic acid/zinc oxide (NR/MAA/ZnO) supramolecular network system was studied. Zinc dimethacrylate (ZDMA) is in situ formed from MAA and ZnO during the mastication of NR, which introduce mass of ionic crosslinks to generate a reversible ionic supramolecular network at the initial stage of peroxide-induced vulcanization at 140℃. Then, free radicals continue to initiate covalent crosslinks to strengthen the NR matrix. The tensile strength of NR with slight covalent crosslinks could achieve 1.63 ∼ 3.86 MPa when vulcanization time keeps in 240 ∼ 360 s. At this time, primary continuous covalent crosslink network has little binding effect on rubber chains, and ionic interactions can be smoothly reorganized to ensure excellent self-healing behavior. The considerable self-healing efficiency of 67%∼95% indicates that the vulcanization time at 240 ∼ 360 s is an appropriate choice to achieve a win–win situation for the mechanical properties and self-healing efficiency of NR/MAA/ZnO composites.

Highly Adhesive, Conductive, and Self-Healing Hydrogel with Triple Cross-Linking Inspired by Mussel and DNA for Wound Adhesion and Human Motion Sensing

Hydrogel has a similar structure and function as the extracellular matrix and is expected to be used for wound adhesion and hemostasis. However, traditional hydrogels have poor adhesion and no self-healing function, and mechanical properties are also limited. Inspired by mussel and adherent DNA, the triple-cross-linking conductive self-healing hydrogel (CaSA-GAD hydrogel) containing calcium ions (Ca2+), sodium alginate, acrylated guanine, acrylamide, and acrylated dopamine was constructed through UV irradiation, including a G–C pairing hydrogen bond dynamic network, a chemical cross-linking network, and an ionic cross-linking dynamic network. The hydrogel exhibits strong adhesion to various surfaces and peeling properties in the bonding of tissues. With high toughness, the hydrogel can be stretched and compressed without damage. The self-healing property further ensures the mechanical properties of the hydrogel. By loading calcium ions to reduce the impedance of the hydrogel greatly, the wound can be monitored at the same time when the wound is bonded. Both fresh and freeze-dried hydrogel can be used to bond the wound on pork stomach and the scope of application of as wound adhesive increases. In addition, the hydrogel can be used as a sensitive sensor to monitor human movement.

3D printing of dual cross-linked hydrogel for fingerprint-like iontronic pressure sensor

Hydrogels with intrinsic high stretchability and flexibility are extremely attractive for soft electronics. However, the existing complicated and laborious methods (such as mold curing) to fabricate microstructured hydrogel (MH) still limit the development of hydrogel-based sensors for flexible devices. Herein, we use digital light processing 3D printing technology to rapidly construct double-network (DN) ionic conductive hydrogel, and then design and print fingerprint-like MH film to manufacture an iontronic pressure sensor. In particular, the DN hydrogel consists of acrylamide/acrylic acid to form a covalently cross-linked network, and magnesium chloride is introduced to form an ionic cross-linked physical network in the hydrogel. The printability (with resolution 150 μm) and mechanical property tunability of DN hydrogel enable the convenient fabrication of sensors. With the biomimetic fingerprint MH film, the iontronic pressure sensor not only has a high sensitivity (0.06 kPa−1), but also has a large detection range (26 Pa–70 kPa) and good stability (200 cycles of pressure loading). We demonstrated that our sensor can be applied to realize tactile sensing in a prosthetic application and detect human motion. With the easy strategy of constructing DN hydrogel with microstructures by 3D printing technology, hydrogel-based sensors are anticipated to be employed in more smart electronics.

Ionic Porous Aromatic Framework as a Self-Degraded Template for the Synthesis of a Magnetic γ-Fe2O3/WO3·0.5H2O Hybrid Nanostructure with Enhanced Photocatalytic Property.

An ionic porous aromatic framework is developed as a self-degraded template to synthesize the magnetic heterostructure of γ-Fe2O3/WO3·0.5H2O. The Fe3O4 polyhedron was obtained with the two-phase method first and then reacted with sodium tungstate to form the γ-Fe2O3/WO3·0.5H2O hybrid nanostructure. Under the induction effect of the ionic porous network, the Fe3O4 phase transformed to the γ-Fe2O3 state and complexed with WO3·0.5H2O to form the n-n heterostructure with the n-type WO3·0.5H2O on the surface of n-type γ-Fe2O3. Based on a UV-Visible analysis, the magnetic photocatalyst was shown to have a suitable band gap for the catalytic degradation of organic pollutants. Under irradiation, the resulting γ-Fe2O3/WO3·0.5H2O sample exhibited a removal efficiency of 95% for RhB in 100 min. The charge transfer mechanism was also studied. After the degradation process, the dispersed powder can be easily separated from the suspension by applying an external magnetic field. The catalytic activity displayed no significant decrease after five recycles. The results present new insights for preparing a hybrid nanostructure photocatalyst and its potential application in harmful pollutant degradation.

An Ionic Liquid Electrolyte with Enhanced Li+ Transport Ability Enables Stable Li Deposition for High-Performance Li-O2 Batteries.

Bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte could endow Li-O2 batteries with low charging overpotential. However, their weak Li+ transport ability (LTA) leads to non-uniform Li deposition. Herein, guided by Sand formula, the LTA of TFSI-IL electrolyte is greatly enhanced to realize robust Li deposition through introducing hydrofluoroether (HFE) and optimizing electrolyte component ratios to regulate solvation environment. The solvation environment changes from Li(TFSI)2 - ion pair into ionic aggregate clusters in the optimal electrolyte thanks to the slicing function of HFE toward ionic aggregate network. The transport parameters of Sand formula are synchronously enhanced, resulting in highly robust Li deposition behavior with greatly improved Coulombic efficiency (ca. 97.5 %) and cycling rate (1 mA cm-2 ). Cycling stability of Li-O2 batteries was greatly improved (a tiny overpotential rise of 64 mV after 75 cycles).

An Ionic Liquid Electrolyte with Enhanced Li+ Transport Ability Enables Stable Li Deposition for High‐Performance Li‐O2 Batteries

AbstractBis(trifluoromethanesulfonyl)imide‐based ionic liquid (TFSI‐IL) electrolyte could endow Li‐O2 batteries with low charging overpotential. However, their weak Li+ transport ability (LTA) leads to non‐uniform Li deposition. Herein, guided by Sand formula, the LTA of TFSI‐IL electrolyte is greatly enhanced to realize robust Li deposition through introducing hydrofluoroether (HFE) and optimizing electrolyte component ratios to regulate solvation environment. The solvation environment changes from Li(TFSI)2− ion pair into ionic aggregate clusters in the optimal electrolyte thanks to the slicing function of HFE toward ionic aggregate network. The transport parameters of Sand formula are synchronously enhanced, resulting in highly robust Li deposition behavior with greatly improved Coulombic efficiency (ca. 97.5 %) and cycling rate (1 mA cm−2). Cycling stability of Li‐O2 batteries was greatly improved (a tiny overpotential rise of 64 mV after 75 cycles).

Bifunctional Ionic Covalent Organic Networks for Enhanced Simultaneous Removal of Chromium(VI) and Arsenic(V) Oxoanions via Synergetic Ion Exchange and Redox Process (Small 46/2021)

Bifunctional Ionic Covalent Organic Networks Incorporation of guanidinium units as anion receptors and redox-active phenol functionalities in covalent organic network (iCON, illustrated as a layered material) promotes a synergistic ion-exchange and redox process that leads to efficient sequestration of toxic chromium(VI) and arsenic(V)-based oxoanions in water and their subsequent conversion into chromium(III)-arsenic(V)-based clusters with lower toxicity and solubility. More details can be found in article number 2104703 by Ping Li, Santa Jansone-Popova, and-co-workers.

A DLPNO-CCSD(T) benchmarking study of intermolecular interactions of ionic liquids.

The accuracy of correlation energy recovered by coupled cluster single-, double-, and perturbative triple-excitations, CCSD(T), has led to the method being considered the gold standard of computational chemistry. The application of CCSD(T) has been limited to medium-sized molecular systems due to its steep scaling with molecular size. The recent development of alternative domain-based local pair natural orbital coupled-cluster method, DLPNO-CCSD(T), has significantly broadened the range of chemical systems to which CCSD(T) level calculations can be applied. Condensed systems such as ionic liquids (ILs) have a large contribution from London dispersion forces of up to 150 kJ mol-1 in large-scale clusters. Ionic liquids show appreciable charge transfer effects that result in the increased valence orbital delocalization over the entire ionic network, raising the question whether the application of methods based on localized orbitals is reliable for these semi-Coulombic materials. Here the performance of DLPNO-CCSD(T) is validated for the prediction of correlation interaction energies of two data sets incorporating single-ion pairs of protic and aprotic ILs. DLPNO-CCSD(T) produced results within chemical accuracy with tight parameter settings and a non-iterative treatment of triple excitations. To achieve spectroscopic accuracy of 1 kJ mol-1 , especially for hydrogen-bonded ILs and those containing halides, the DLPNO settings had to be increased by two orders of magnitude and include the iterative treatment of triple excitations, resulting in a 2.5-fold increase in computational cost. Two new sets of parameters are put forward to produce the performance of DLPNO-CCSD(T) within chemical and spectroscopic accuracy.

Bifunctional Ionic Covalent Organic Networks for Enhanced Simultaneous Removal of Chromium(VI) and Arsenic(V) Oxoanions via Synergetic Ion Exchange and Redox Process.

Chromium (VI) and arsenic (V) oxoanions are major toxic heavy metal pollutants in water threatening both human health and environmental safety. Herein, the development is reported of a bifunctional ionic covalent organic network (iCON) with integrated guanidinium and phenol units to simultaneously sequester chromate and arsenate in water via a synergistic ion-exchange-redox process. The guanidinium groups facilitate the ion-exchange-based adsorption of chromate and arsenate at neutral pH with fast kinetics and high uptake capacity, whereas the integrated phenol motifs mediate the Cr(VI)/Cr(III) redox process that immobilizes chromate and promotes the adsorption of arsenate via the formation of Cr(III)-As(V) cluster/complex. The synergistic ion-exchange-redox approach not only pushes high adsorption efficiency for both chromate and arsenate but also upholds a balanced Cr/As uptake ratio regardless of the change in concentration and the presence of interfering oxoanions.

Fast ion transport for synthesis and stabilization of \u03b2-Zn4Sb3

Mobile ion-enabled phenomena make β-Zn4Sb3 a promising material in terms of the re-entry phase instability behavior, mixed electronic ionic conduction, and thermoelectric performance. Here, we utilize the fast Zn2+ migration under a sawtooth waveform electric field and a dynamical growth of 3-dimensional ionic conduction network to achieve ultra-fast synthesis of β-Zn4Sb3. Moreover, the interplay between the mobile ions, electric field, and temperature field gives rise to exquisite core-shell crystalline-amorphous microstructures that self-adaptively stabilize β-Zn4Sb3. Doping Cd or Ge on the Zn site as steric hindrance further stabilizes β-Zn4Sb3 by restricting long-range Zn2+ migration and extends the operation temperature range of high thermoelectric performance. These results provide insight into the development of mixed-conduction thermoelectric materials, batteries, and other functional materials.

Self-healing epoxy coatings with microencapsulated ionic PDMS oligomers for corrosion protection based on supramolecular acid-base interactions

To obtain a self-healing coating and improve the corrosion resistance of coated low-carbon steel surfaces, a commercial epoxy coating was modified by adding microcapsules composed of a poly(methyl methacrylate) shell and a core of ionic polydimethylsiloxane (PDMS) oligomers. The encapsulation of amino- and carboxylic acid-terminated PDMS was achieved by a solvent evaporation process after the emulsification of core and shell materials, dissolved in CH2Cl2, in a suitable colloidal solution. A high core loading of nearly 50% wt. was successfully obtained by carefully increasing the interfacial tension of oil-in-water emulsion before the solvent evaporation. The microcapsule morphology was evaluated by SEM and optical microscopy analyses, which showed a particle diameter range of 20–70 μm. The presence of ionic PDMS oligomers as core materials was demonstrated by FTIR spectroscopy and thermogravimetric analysis (TGA), which was also employed to determine the core loading. The newly prepared microcapsules were then incorporated into the matrix of a commercial two-component epoxy coating. Corrosion protection abilities were assessed by comparing samples coated with a standard epoxy coating modified with a 20% wt. of microcapsules and the pristine epoxy coating. The corrosion protection performance of the modified coating was evaluated through electrochemical impedance spectroscopy (EIS) tests and potential vs time measurements, which showed that the microcapsules in the coating matrix caused a beneficial increase in barrier properties of a scratched coating. The surface damage triggered the release of functional PDMS oligomers, leading to the formation of a supramolecular ionic network and providing self-healing abilities to the modified coating.

Isostructural rubidium and caesium 4-(3,5-di-nitro-pyrazol-4-yl)-3,5-di-nitro-pyrazolates: crystal engineering with polynitro energetic species.

In the structures of the title salts, poly[[μ4-4-(3,5-di-nitro-pyrazol-4-yl)-3,5-di-nitro-pyrazol-1-ido]rubidium], [Rb(C6HN8O8)] n , (1), and its isostructural caesium analogue [Cs(C6HN8O8) n , (2), two independent cations M1 and M2 (M = Rb, Cs) are situated on a crystallographic twofold axis and on a center of inversion, respectively. Mutual inter-molecular hydrogen bonding between the conjugate 3,5-dinito-pyrazole NH-donor and 3,5-di-nitro-pyrazole N-acceptor sites of the anions [N⋯N = 2.785 (2) Å for (1) and 2.832 (3) Å for (2)] governs the self-assembly of the translation-related anions in a predictable fashion. Such one-component modular construction of the organic subtopology supports the utility of the crystal-engineering approach towards designing the structures of polynitro energetic materials. The anionic chains are further linked by multiple ion-dipole inter-actions involving the 12-coordinate cations bonded to two pyrazole N-atoms [Rb-N = 3.1285 (16), 3.2261 (16) Å; Cs-N = 3.369 (2), 3.401 (2) Å] and all of the eight nitro O-atoms [Rb-O = 2.8543 (15)-3.6985 (16) Å; Cs-O = 3.071 (2)-3.811 (2) Å]. The resulting ionic networks follow the CsCl topological archetype, with either metal or organic ions residing in an environment of eight counter-ions. Weak lone pair-π-hole inter-actions [pyrazole-N atoms to NO2 groups; N⋯N = 2.990 (3)-3.198 (3) Å] are also relevant to the packing. The Hirshfeld surfaces and percentage two-dimensional fingerprint plots for (1) and (2) are described.

Facile Fabrication of Eucommia Rubber Composites with High Shape Memory Performance.

We processed a series of shape memory Eucommia rubber (ER) composites with both carbon–carbon and ionic cross-linking networks via a chemical cross-linking method. The influence of the carbon–carbon cross-linking and ion cross-linking degree of ER composites on curing, mechanical, thermal, and shape memory properties were studied by DSC, DMA, and other analytical techniques. Dicumyl peroxide (DCP) and zinc dimethacrylate (ZDMA) played a key role in preparing ER composites with a double cross-linking structure, where DCP initiated polymerization of ZDMA, and grafted ZDMA onto polymer molecular chains and cross-linked rubber molecular chains. Meanwhile, ZDMA combined with rubber macromolecules to build ionic cross-linking bonds in composites under the action of DCP and reinforced the ER composites. The result showed that the coexistence of these two cross-linking networks provide a sufficient restoring force for deformation of shape memory composites. The addition of ZDMA not only improved the mechanical properties of materials, but also significantly enhanced shape memory performance of composites. In particular, Eucommia rubber composites exhibited outstanding mechanical properties and shape memory performance when DCP content was 0.2 phr.

Lithium battery enhanced by the combination of in-situ generated poly(ionic liquid) systems and TiO2 nanoparticles

An instant challenge in the development of polymer electrolytes (PEs) for lithium batteries is the trade-off between sacrificing ion transport for improved mechanical properties. Poly(ionic liquid)s (PILs), which have advantages such as good chemical compatibility and electrochemical stability, is expected to lead the progress of next-generation energy technology. Herein, a series of thermally cured PEs featuring cross-linked ionic networks are fabricated via solvent-less, in-situ polymerization and introduced for rechargeable lithium batteries. To further enhance the battery performance, titanium dioxide nanoparticles (TiO2 NPs) are dispersed into the component to prepare composite polymer electrolytes (CPEs). Room-temperature ionic conductivity of around 1.97 × 10−4 S cm−1 is achieved from the sample with 0.5 wt % of TiO2 addition (CPE-8), which is significantly higher than that of the sample (PE-8) without TiO2 (1.51 × 10−4 S cm−1). The qualified thermal property and mechanical strength, enhanced stability against lithium metal, and dendrite suppression guarantee the satisfactory prospects of CPE-8 for development in lithium batteries. The specific discharge capacity of the LiFePO4/Li cell with the CPE-8 is 149 mAh g−1, and 90% of the value is maintained after 140 cycles at 0.2 C under 25 °C. These advancements are attributed to the synergistic effects of in-situ cross-linked PIL networks and TiO2 NPs, representing a simple and effective approach towards realizing new CPE for high-performance lithium batteries.

Understanding the Molecular Dynamics of Dual Crosslinked Networks by Dielectric Spectroscopy.

The combination of vulcanizing agents is an adequate strategy to develop multiple networks that consolidate the best of different systems. In this research, sulfur (S), and zinc oxide ( ZnO) were combined as vulcanizing agents in a matrix of carboxylated nitrile rubber (XNBR). The resulting dual network improved the abrasion resistance of up to ~15% compared to a pure ionically crosslinked network, and up to ~115% compared to a pure sulfur-based covalent network. Additionally, the already good chemical resistance of XNBR in non-polar fluids, such as toluene and gasoline, was further improved with a reduction of up to ~26% of the solvent uptake. A comprehensive study of the molecular dynamics was performed by means of broadband dielectric spectroscopy (BDS) to complete the existing knowledge on dual networks in XNBR. Such analysis showed that the synergistic behavior that prevails over purely ionic vulcanization networks is related to the restricted motions of rubber chain segments, as well as of the trapped chains within the ionic clusters that converts the vulcanizate into a stiffer and less solvent-penetrable material, improving abrasion resistance and chemical resistance, respectively. This combined network strategy will enable the production of elastomeric materials with improved performance and properties on demand.

Strong, tough, anti-freezing, non-drying and sensitive ionic sensor based on fully physical cross-linked double network hydrogel

Ionic conductive double network (DN) sensors have attracted increasing attention in wearable electronic devices. However, their low mechanical and sensing properties as well as poor moisture retention and freezing resistance restrict severely their applications. Herein, we synthesized a fully physical cross-linked poly (N-hydroxymethyl acrylamide)/agar/ethylene glycol (PHA/Agar/EG) ionic conductive DN hydrogel exhibiting high strength and toughness, fast self-recovery, good fatigue resistance and good self-healing. Agar could form a physical network via reversible sol-gel transition, and interact with physical cross-linked poly (N-hydroxymethyl acrylamide) and sodium chloride (NaCl) via hydrogen bonds and salting-out effect, respectively. Meanwhile, ethylene glycol and NaCl improved the mechanical properties, long-lasting moisture retention and anti-freezing ability. The PHA/Agar/EG gel-based flexible sensor possessed excellent long-lasting and fatigue resistant sensing properties, and could monitor various human activities stably and sensitively. Therefore, this work would provide a simple and promising strategy to fabricate flexible sensors with integrated high performances for smart wearable devices.

Enhancement of EPDM Crosslinked Elastic Properties by Association of Both Covalent and Ionic Networks.

The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak elasticity recovery of such a physical network after a long period of compression, the combination of both physical and chemical networks was studied. In that frame, an ethylene-propylene-diene terpolymer grafted with maleic anhydride (EPDM-g-MA) was crosslinked with metal salts and/or dicumyl peroxide (DCP). Thus, the influence of these two types of crosslinking networks and their combination were studied in detail in terms of compression set. The second part of this work was focused on the influence of different metallic salts (KOH, ZnAc2) and the sensitivity to the water of the physical crosslinking network. Finally, the combination of ionic and covalent network allowed combining the processability and better mechanical properties in terms of recovery elasticity. KAc proved to be the best ionic candidate to avoid water degradation of the ionic network and then to preserve the elasticity recovery properties under aging.

Polyelectrolyte Complex that Minimizes Bacterial Adhesion to Polyester

AbstractBacterial adhesion is a major concern in the medical field, where bacterial fouling can lead to diminished device efficacy and failure. To combat this, polyelectrolyte complexes (PECs) can be used to modify surfaces to reduce bacterial attachment. In the present study, a water‐based PEC of poly(diallyldimethylammonium chloride) [PDDA] and poly(acrylic acid) are deposited in a simple two‐step process to the surface of polyester fabric. This process includes the deposition of a dissolved mixture of the two polyelectrolytes, followed by the formation of the ionic network through exposure to citric acid buffer. These coatings facilitate the removal of >95% of deposited Staphylococcus aureus after simple rinsing with deionized water. The high degree of surface ionization monitored by FTIR suggests that electrostatic repulsion is responsible for the observed antifouling activity. The morphology of these coatings which is monitored by scanning electron microscope (SEM) and atomic force microscope (AFM) is shown to depend on curing the curing conditions, which suggests that this simple process can be tailored to many applications.

How to Choose a Secondary Interaction to Improve Stretchability of Associative Polymers?

This study focuses on the stretchability of brittle ionomers after introducing three types of hydrogen bonds, i.e., dual, triple, and quadruple hydrogen bonds. The introduction of dual or triple hydrogen bonds that are weaker than the ionic association improves the stretchability, and better improvement has been achieved for the triple hydrogen bonds. In comparison, the introduction of quadruple hydrogen bonds that are equally strong as the ionic association does not show this type of improvement. This result strongly indicates that there is an optimized strength ratio between the first (the stronger ionic) network and the secondary (the weaker hydrogen-bonding) network, i.e., the secondary network should be considerably weaker but still not too weaker than the first network. When this condition is satisfied, continuous dissociation and association of the secondary network weaken the chain retraction after the strain-induced breakup of the first network, thereby suppressing the formation of defects or microscopic cracks that potentially grow into the macroscopic fracture.