Ionic Liquid Gel Research Articles

Boosting ion dynamics by developing graphitic carbon Nitride/Carbon hybrid electrode materials for ionogel supercapacitor

g-C3N3 (GCN) have been used as supercapacitor electrode due to its tunable structure and high carbon–nitrogen ratio, However, the poor conductivity and very low surface area remain a challenge for practical applications. The formation of a hybrid structure of GCN with carbon-based materials such as activated carbon (AC), graphene (G), and carbon nanotube (CNT) help to improve its electrochemical properties. In this work, we synthesized GCN-AC, GCN-G and GCN-CNT hybrid structures and studies the electrochemical properties in symmetric two electrode configuration. The obtained specific capacitance of GCN, GCN-G, GCN-CNT and GCN-AC 11F/g, 244F/g, 237F/g and 266F/g, respectively. The energy density and voltage window of the GCN-AC device were enhanced by replacing the conventional electrolyte with ionic liquid gel electrolyte. The ionogel mediated device could achieve an enhanced specific capacitance of 303F/g with an energy density of 46.45 Wh/Kg and power density of 750 W/Kg.

Switchable ionic conductivity and viscoelasticity of ionogels containing photo- and thermo-responsive organometallic ionic liquids

Ionic liquid gels (ionogels) are useful as flexible solid electrolytes owing to their high ionic conductivity and non-volatility. Ionogels possessing photoswitchable ionic conductivity have versatile electronic applications, although the fabrication of such materials remains a challenge. Herein, we synthesized photoresponsive ionogels by adding a low-molecular-weight gelator, 12-hydroxystearic acid, to photoreactive organometallic ionic liquids. UV photoirradiation of an ionogel containing an ionic liquid [Ru(C5H5)(C6H5OC3H6CN)][N(SO2F)2] (Gel-1) decreased its ionic conductivity while increasing its viscoelastic modulus. This is owing to the photochemical formation of coordination bonds between the ionic liquid cations in the gel. The reaction was reversed upon heating, hence the physical properties were reversibly controlled by the application of light and heat. An ionogel containing an ionic liquid [Ru(C5H5){C6H3(OC6H12CN)3}][N(SO2F)2] with three substituents (Gel-2) was also prepared, which was transformed into a rubber-like solid having a coordination polymer structure upon photoirradiation. The photoproduct exhibited much lower ionic conductivity and higher viscoelastic modulus compared with the photoproduct of Gel-1.

Mechanism of charge accumulation of poly(heptazine imide) gel

Photo-stimuli response in materials is a fascinating feature with many potential applications. A photoresponsive gel of poly(heptazine imide), PHI, termed PHIG, exhibits photochromism, photoconductivity, and photo-induced charge accumulation, and is generated using ionic liquids and PHI. Although there are several examples of ionic liquid gels that exhibit photochromism and photoconductivity, this is the first report of an ionic liquid gel that exhibits both these properties as well as charge accumulation. We conducted experimental and theoretical investigations to understand the mechanism of the photostimulus response of PHIG, especially charge accumulation. The proposed model explains both the mechanism of charge accumulation and dark photocatalysis by PHI and provides new concepts in the field of photofunctional materials.

Supported Ionic Liquid Gel Membranes Enhanced by Ionization Modification for Sodium Metal Batteries

Supported Ionic Liquid Gel Membranes Enhanced by Ionization Modification for Sodium Metal Batteries

Low‐Molecular‐Weight Supramolecular‐Polymer Double‐Network Eutectogels for Self‐Adhesive and Bidirectional Sensors

AbstractIonic conducting eutectogels have attracted enormous attention as an alternative to the conventional temperature‐intolerant hydrogels and costly ionic liquid gels in constructing flexible electronic devices. However, current eutectogels prepared via cross‐linked polymer or low‐molecular‐weight gelators suffer from limited stretchability and insufficient surface‐adaptive adhesion. Herein, a low‐molecular‐weight supramolecular network is introduced into a covalent polymer network in a eutectogel architecture, and a novel supramolecular‐polymer double‐network (SP‐DN) strategy is demonstrated to fabricate conductive SP‐DN eutectogels with high stretchability (>4000% elongation) and toughness (≈800 J m−2), as well as self‐healing, self‐adhesive and anti‐freezing/anti‐drying characteristics. These unique features lead to the successful realization of SP‐DN eutectogels in wearable self‐adhesive strain sensors, which can conformally deform with the skin and dynamically monitor body movements with high sensitivity and long‐term stability over a wide temperature range (−40 to 60 °C). Furthermore, the strain sensors can accurately detect body movements along two opposite directions (bend up or bend down), which are rarely reported in the literature. Distinct from the widely explored polymer double‐network (P‐DN) hydrogels, the developed SP‐DN eutectogel platform is capable of well‐regulating molecular‐scale noncovalent and covalent interactions, providing a paradigm for the creation of smart soft materials with versatile performance and high environmental adaptability.

Space-charge limited ionic conductivity enhancement in gel polymer electrolyte capacitors by embedding nanoparticles

In this work, a novel mixture of ionic liquid gel polymer electrolyte (ILGPE), containing 1-butyl-3-methylimidazolium bromide, ammonium acetate and poly(vinyl alcohol), with Si@C and SiO2 embedded nanoparticles is fabricated. The resulting CILGPE is deposited onto interdigitated electrodes. The fabricated electrolytes have been characterised by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the resulting capacitors have been characterised by impedance spectroscopy (IS) and linear sweep voltammetry (LSV) and modelled. The specific capacitance for capacitor with ILGPE is 0.042Fcm−3, while for the capacitor with SiO2 and Si@C embedded in ILGPE are 0.072 Fcm−3 and 0.06 Fcm−3, respectively. Therefore, the addition of SiO2 and Si@C nanoparticles improves the capacitance by 71% and 42%, respectively. The results of fitting I-V curves exhibit reductions in both the activation voltage (Vtr) and in the voltage that indicates the traps are filled (VTFL) with the addition of nanoparticles, revealing an increase in charge contribution. We propose that the capacitance enhancement is due to the contribution of nanoparticles to: (i) the creation new effective ion transport pathways, (ii) ion dissociation in the electrolyte and (iii) the crystallinity reduction of ILGPE. This work contributes with new findings about the effect of nanoparticles on the Space-charge-limited-conduction (SCLC) mechanism and how these changes in transport mechanism are related to the series and leakage resistances, capacitance, and physicochemical properties.

3D Printable and Biocompatible Iongels for Body Sensor Applications

AbstractSoft‐ionic materials with biocompatibility and 3D printability are needed to develop next‐generation devices to interface between electronic and biological signals. Herein, thermoreversible and biocompatible ionic liquid gels or iongels, which can be processed by direct ink writing are reported. The iongels are designed by taking advantage of polyvinyl alcohol/phenol interactions to gelify biocompatible cholinium carboxylate ionic liquids. The obtained iongels are stable, soft, and flexible materials (Young modulus between 14 and 70 kPa) with high ionic conductivity (1.8 × 10–2 S cm–1). Interestingly, they presented thermoreversible properties with gel–sol transitions ranging from 85 and 110 °C, which allows the iongel processing via direct ink writing 3D printing by material extrusion at temperatures over its transition. These 3D printable iongels are integrated into a variety of body sensors applications, namely pressure sensors, motion sensors and electrodes for electrophysiological recordings. The iongels are used as pressure sensors with a sensitivity of 0.1 kPa–1, ten times higher than that of others similar materials reported so far; showing its ability to detect human motion. Furthermore, the iongels showed excellent performance in electrodes for electrocardiography (ECG) recording, presenting good stability over time with electrocardiographic waves maintained their typical shape even after weeks.

High-performance TEMPO-oxidised cellulose nanofibre/PEDOT:PSS/ionic liquid gel actuators

In a previous study that the authors have conducted, actuators based on cellulose nanofibre/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/ionic liquid (CNF/PEDOT:PSS/IL) gel electrodes and CNF/IL gel electrolytes could not be fabricated due to poor adhesion between the electrode and electrolyte layers. However, in this study, a series of novel actuators were developed using a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidised cellulose nanofibre (TOCN)/PEDOT:PSS/IL gel electrode with a TOCN/IL or poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)/IL) gel electrolyte due to good adhesion between the electrode and electrolyte layers. The TOCN/PEDOT:PSS/IL gel electrode actuators exhibited high strain performance. These actuators mainly operated via an electrostatic double-layer capacitor mechanism, with a redox capacitor mechanism making a relatively small contribution. The TOCN/PEDOT:PSS/IL gel electrode actuators showed frequency-dependent displacement responses, and a model of double-layer charging kinetics considering the combined resistance of the gel electrode/electrolyte successfully simulated the experimental results. The development of electrodes with excellent electrical conductivity (PVdF(HFP)/IL electrolytes) and electrodes/electrolytes with excellent electrical and ionic conductivities (TOCN/IL gel electrolytes) will facilitate the optimisation of the performance of TOCN/PEDOT:PSS/IL-based polymer actuators. These flexible films will be applicable for the development of actuator materials for use in wearable and transparent electronic and energy conversion devices.

Recent advances in solid electrolytes for synaptic transistors

Traditional computer development based on the Von Neumann system has encountered a bottleneck. The development of a brain-like computer that simulates the operation mode of the human brain is an important way to break the bottleneck. The high-performance multi-terminal synaptic transistor is the basic unit to realize a brain-like computer. In the multi-terminal synaptic transistor, electrolyte with electric double layer is the pivotal structure to realize the function of simulated synapse. Compared with ionic liquid and ionic gels，solid electrolytes have more stable chemical properties, and lower production costs. This article reviews the applications of these types of solid electrolytes in synaptic transistors. The content is mainly divided into four parts: organic solid electrolyte, inorganic solid electrolyte, organic-inorganic hybrid solid electrolyte, synaptic transistor application and future prospect. In this paper, the advantages and disadvantages of each material are summarized and compared, and various synaptic characteristics are analyzed in detail. This review has a good reference value for the study of solid electrolyte synaptic transistors.

Mechanoactivation of Color and Autonomous Shape Change in 3D-Printed Ionic Polymer Networks.

Stimuli-responsive materials can enhance the field of three-dimensional (3D) printing by generating objects that change shape in response to external cues. While temperature and pH are common inputs for initiating a response in a 3D-printed object, there are few examples of using a mechanical input to afford a response. Herein, we report a suite of mechanochromic ionic liquid gel inks that can be used to fabricate 3D-printed objects that use a single mechanoactivation event to elicit both a mechanochromic response and an autonomous shape change. Direct-ink write 3D printing was used to deposit ionic liquid gel inks to create multimaterial objects that underwent a predetermined mechanoactivated shape change (mechanomorphic) when the sample was pulled and then released. When spiropyran was incorporated into the inks, the onset of spiropyran isomerization into its purple merocyanine form occurred at strains dependent upon the particular ion gel ink formulation. We suggest that the color onset could be used as a simple indicator for when the strain required to achieve a predetermined change in shape has been reached, potentially serving as real-time visual cue for the user. Such morphing 3D-printed structures with integrated instructions have potential application to areas including stowable structures as well as multiresponsive autonomous components and sensors.

The Influences of 1-Butyl-3-Methylimidazolium Tetrafluoroborate on Electrochemical, Thermal and Structural Studies as Ionic Liquid Gel Polymer Electrolyte

After decades of development, ionic liquid gel polymer electrolytes (ILGPEs) are currently experiencing a renaissance as a promising electrolyte to be used in electrochemical devices. Their inherent tendency towards poor electrochemical properties have limited their applications and commercialization activities. Henceforth, gel polymer electrolyte (GPE) is being introduced to alleviate the abovementioned issues. In this work, the assessment of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] in poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) to form ILGPE was done. The relationship of [BMIM][BF4] towards the dielectric properties at different wt. % ratios and temperature was ascertained. The results indicated that [BMIM]BF4 is able to facilitate fast conduction. Moreover, it was found that [BMIM][BF4] could serve as an effective agent in reducing crystallinity and glass transition temperature of the polymer and thus enhanced the ionic conductivity of the samples. Notwithstanding, the ILGPE sample possessed a high thermal stability up to 300 °C and good electrochemical stability of 4.2 V which are beneficial for operation in electrochemical devices. All in all, the correlation between the ionic liquid chemistry and electrochemical performances could provide a valuable insight to rational selection and design for ILGPE electrolytes.

Application of ionic liquid-polymer gel membrane in toluene/n-heptane separation

The separation of aromatic and alkane is one of the most important and challenge chemical separation process. This study reports the high-efficiency separation of aromatics/alkanes in the pervaporation process based on a series of novel ionic liquid gel membranes. The ionic liquid gel membrane was characterized by FT-IR, SEM, AFM, TGA, and XRD techniques. The results revealed that the IL was maintained in the three-dimensional structure of polymer support and the membrane kept its stability when the temperature was over 300 °C. The relevant parameters i.e. polymer concentration, IL concentration, IL type, film-forming temperature, membrane thickness, feed concentration, operating temperature and feed flow rate on membrane process were investigated. The optimal membrane was prepared when the P(VDF-HFP) and [Amim][Tf2N] concentrations were 15 wt% and 45 wt%, the film-forming temperature was 15 °C and the membrane thickness was 120 μm. When the initial toluene concentration was 50 wt% and the flow rate was 200 mL/min, the best flux (120 g·m−2·h−1) and separation factor (11.3) were observed at 25 °C. Moreover, the separation factor was over 10 and the flux maintained at the same level after working continuously for 30 h, which indicates that the membrane has good stability.

Carbon-based ionic liquid gels: alternative adsorbents for pharmaceutically active compounds in wastewater

Hybrid ionic liquid gels, efficient adsorbents for cleaning wastewater from pharmaceutically active compounds.

Controllable Synthesis of Zinc Oxide with Ionic Liquid and Supramolecular Gel as Co-Template for the Degradation of Organic Dyes

Controllable Synthesis of Zinc Oxide with Ionic Liquid and Supramolecular Gel as Co-Template for the Degradation of Organic Dyes

NHighly N/O co-doped carbon nanospheres for symmetric supercapacitors application with high specific energy

Carbon nanospheres (CSs) with high synthetic yield, large specific surface area (SBET), high heteroatom dopant and hierarchical porosity exhibits unique advantages in supercapacitor applications, yet integrating all these merits into one material is still challengeable. Herein, we developed a template-free CuCl2-activation strategy to high-yield preparation of highly N/O co-doped porous CSs derived from a quinone-amine polymer precursor. It is found that the mild activating effect of CuCl2 not only can retain the initial nanosphere structure of the precursor, but also can enable the target CSs to achieve high-level N/O dopants (14.9/10.6 at.%), large SBET (2957.8 m2 g−1), and ultrahigh carbon yield (~60%). Benefiting from these merits, the optimal CS-CuCl2-800 sample exhibits a delightful capacitance of 273.9 F g–1 at 0.5 A g–1, excellent cyclic performance (capacitance retention, ~96.5%) during 10,000 charging/discharging cycles at 2 A g–1, and a moderate energy output of 8.0 Wh kg–1 in 6 M KOH electrolyte. When used ion-liquid electrolyte, the energy density of the device is further boosted to 80.3 Wh kg–1, and the corresponding solid-state supercapacitors based on the ionic liquid gel electrolyte still maintain an high energy output of 71.3 Wh kg–1, which is superior to many reported solid-state supercapacitors. Therefore, the facile activation strategy together with tunable properties, high carbon yield, and excellent electrochemical performance indicate promising application prospects in the large-scale fabrication of commercial porous carbons.

Ionic liquid gel gate tunable p-Si/MoS2 heterojunction p-n diode

Monolayer MoS2 crystals investigated in this work were grown via chemical vapor deposition on Si/SiO2 substrates. Using a wet KOH etch, these crystals were transferred onto the edge of a freshly cleaved p-Si/SiO2 wafer where they formed mechanically robust heterojunctions at the p-Si/MoS2 interface. Electrical characterization of the device across the junction yielded an asymmetric I–V response similar to that of a p-n diode. The I–V response was electrostatically tunable via an ionic liquid gel gate. This is the first report demonstrating reversible gate control of the p-Si/MoS2 diode current by several orders of magnitude while lowering its turn-on voltage. Fermi energy level shifts within the MoS2 bandgap by the gate was believed to be responsible for the observed effects. The ease of fabrication, low operating voltages (<±2 V), and moderately high throughput currents (∼1 µA) are attractive features of this diode, especially for use in sensors and power saving electronics.

All-Solid-State Asymmetric Supercapacitors with Novel Ionic Liquid Gel Electrolytes

In the past years, all-solid-state supercapacitors, as energy storage devices, have drawn greatest attention in both academic and industrial sectors because of their potential applications, in particular in the wearable and portable electronics. However, poor energy densities of all-solid-state supercapacitors restrict their practical applications. In this study, we first report novel ionic liquid gels composed of poly(vinyl alcohol) (PVA), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), and tetrabutylammonium tetrafluoroborate (TBABF4) (PVA:BMIMBF4:TBABF4) as the solid-state electrolytes. It is found that the PVA:BMIMBF4:TBABF4 solid-state electrolytes exhibit dramatically enhanced ionic conductivity. Afterward, we report all-solid-state asymmetric supercapacitors (ASCs) by using MnO2 coated on a carbon cloth (CC) as the positive electrode, reduced graphene oxide coated on a CC as the negative electrode, and novel PVA:BMIMBF4:TBABF4 as the solid-state electrolyte. All-solid-state ASCs exhibit an operational window of 3 V, an energy density of 61.2 W h/kg at the power density of 1049 W/kg, and more than 80% capacitance retention after 3000 charge/discharge cycles. All these results demonstrate that we provide a facile way to develop high-energy-density all-solid-state ASCs with good cycling stability.

High‐Rate Lithium‐Ion Cycling in Electrodeposited Binder‐Free Thin‐Film Vanadium Oxide Cathodes with Lithium Metal Anodes in Ionic Liquid and Polymer Gel Analogue Electrolytes

AbstractHigh rate and long cycle life performance for electrodeposited, binder‐free V2O5 thin film cathodes and lithium metal anodes is described using liquid and polymer gel electrolytes of the pyrrolidinium based (C4mpyrTFSI) ionic liquid (IL). Sharp well‐defined voltammetric peaks typically seen with nanostructured V2O5 materials in organic electrolytes, support the fast kinetics observed. The addition of vinylene carbonate (VC) stabilises the electrolyte interface leading to higher electrode capacities than for the additive‐free electrolyte, ∼120 versus ∼90 mAh g−1 at 0.75 C. Polymer gel electrolytes based on the IL yield similar electrode capacities, coulombic efficiencies and high rate performances without the VC‐additive. The polymer gel option delivers the better long‐term stability up to 400 cycles with lithium metal anodes with minimal capacity fade at elevated charge and discharge rates up to 5 C.

Comparison of the effects of different ionic liquid-gels on the efficiencies of the PbSe, PbS and PbTe quantum dot sensitized solar cells

Abstract The semiconductor nanocrystal quantum dots (QD) are used in the third generation solar cells due to their high photon conversion efficiency. In this study, we investigated the effects of ionic liquid on the efficiency of lead chalcogenide (PbSe, PbTe and PbS) QD solar cells. To achieve this, we looked at the interaction between the alkyl groups (R = CH3) and the thiol bonds (SH) of the selected organic electrolytes. Two different classes of liquids were prepared based on organic (960 and SB) and inorganic (AY1-3) ionic liquid (IL) where AY1-3 liquid include LiI, NaI, I2 materials; 960 and SB type liquids include BMII, tBP and GuNCS materials. These liquids provide redox reactions. 5 different ILs were applied to each of the 3 types of QDs and 15 solar cells were produced. Particle sizes and solar cell parameters like fill factor and efficiencies were determined through optical absorption, photoluminescence, TEM, SEM, EDS and J-V measurements. It was observed that the interaction of these groups affected the fill factor (FF), open circuit voltage (Voc) and efficiency of PbX (X = Se, S, Te) QD solar cells. The AY1 was found to be compatible with the PbX QDSSCs when used alone while the AY2 was not. LiI was an effective IL when used alone which resulted in with an efficiency of 7.853 for PbS QDSSC. NaI and GuSCN introduced different pairs of redox to the system, increasing the efficiency of PbSe solar cells to 8.257.

Designing Materials for Aqueous Catalysis: Ionic Liquid Gel and Silica Sphere Entrapped Iron-TAML Catalysts for Oxidative Degradation of Dyes.

Materials have been developed that encapsulate a homogeneous catalyst and enable it to operate as a heterogeneous catalyst in water. A hydrophobic ionic liquid within the material was used to dissolve Fe-TAML and keep it from leaching into the aqueous phase. One-pot processes were used to entrap Fe-TAML in basic ionic liquid gels, and ionic liquid gel spheres structured via a modified Stöber synthesis forming SiO2 particles of uniform size. Catalytic activity was demonstrated via the oxidative degradation of dyes. Fe-TAML entrapped in a basic ionic liquid gel exhibited consistent activity in five recycles. This discovery of heterogenized H2O2 activators prepared by sol-gel and Stöber processes opens new possibilities for the creation of engineered catalytic materials for water purification.