"Bucky gels" for tailoring electroactive materials and devices: the composites of carbon materials with ionic liquids

Correlation between Physical Properties of 12-Hydroxystearic Acid Organogels and Hansen Solubility Parameters

The Hansen solubility parameter (HSP) is a useful index for reasoning the gelation behavior of low-molecular-weight gelators (LMWGs). However, the conventional HSP-based methods only "classify" solvents that can and cannot form gels and require many trials to achieve this. For engineering purposes, quantitative estimation of gel properties using the HSP is highly desired. In this study, we measured critical gelation concentrations based on three distinct definitions, mechanical strength, and light transmittance of organogels prepared with 12-hydroxystearic acid (12HSA) and correlated them with the HSP of solvents. The results demonstrated that the mechanical strength, in particular, strongly correlated with the distance of 12HSA and solvent in the HSP space. Additionally, the results indicated that the constant volume-based concentration should be used when comparing the properties of organogels to a different solvent. These findings are helpful in efficiently determining the gelation sphere of new LMWGs in HSP space and contribute to designing organogels with tunable physical properties.

Electroconductive, Adhesive, Non-Swelling, and Viscoelastic Hydrogels for Bioelectronics

As a new class of materials, implantable flexible electrical conductors have recently been developed and applied to bioelectronics. An ideal electrical conductor requires high conductivity, tissue-like mechanical properties, low toxicity, reliable adhesion to biological tissues, and the ability to maintain its shape in wet physiological environments. Despite significant advances, electrical conductors that satisfy all these requirements are insufficient. Herein, a facile method for manufacturing a new conductive hydrogels through the simultaneous exfoliation of graphite and polymerization of zwitterionic monomers triggered by microwave irradiation is introduced. The mechanical properties of the obtained conductive hydrogel are similar to those of living tissue, which is ideal as a bionic adhesive for minimizing contact damage due to mechanical mismatches between hard electronics and soft tissues. Furthermore, it exhibits excellent adhesion performance, electrical conductivity, non-swelling, and high conformability in water. Excellent biocompatibility of the hydrogel is confirmed through a cytotoxicity test using C2C12 cells, a biocompatibility test on rat tissues, and their histological analysis. The hydrogel is then implanted into the sciatic nerve of a rat and neuromodulation is demonstrated through low-current electrical stimulation. This hydrogel demonstrates a tissue-like extraneuronal electrode, which possesses high conformability to improve the tissue-electronics interfaces, promising next-generation bioelectronics applications.

Physical and electrochemical properties of new structurally flexible imidazolium phosphate ionic liquids

New structurally flexible 1-methyl- and 1,2-dimethyl-imidazolium phosphate ionic liquids (ILs) bearing oligoethers have been synthesized and thoroughly characterized. These novel ILs revealed high thermal stabilities, low glass transitions, high conductivity and wide electrochemical stability windows up to 6 V. Both the cations and anions of 1-methyl-imidazolium ILs diffuse faster than the ions of 1,2-dimethyl-imidazolium ILs, as determined by pulsed field gradient nuclear magnetic resonance (PFG-NMR). The 1-methyl-imidazolium phosphate ILs showed relatively higher ionic conductivities and ion diffusivity as compared with the 1,2-dimethyl-imidazolium phosphate ILs. As expected, the diffusivity of all the ions increases with an increase in the temperature. The 1-methyl-imidazolium phosphate ILs formed hydrogen bonds with the phosphate anions, the strength of which is decreased with increasing temperature, as confirmed by variable temperature ¹H and ³¹P NMR spectroscopy. One of the representative IL, [EmDMIm][DEEP], presented promising elevated temperature performance as an electrolyte in a supercapacitor composed of multiwall carbon nanotubes and activated charcoal (MWCNT/AC) composite electrodes.

Carbon Nanotube-Hydrogel Composites Facilitate Neuronal Differentiation While Maintaining Homeostasis of Network Activity

It is often assumed that carbon nanotubes (CNTs) stimulate neuronal differentiation by transferring electrical signals and enhancing neuronal excitability. Given this, CNT-hydrogel composites are regarded as potential materials able to combine high electrical conductivity with biocompatibility, and therefore promote nerve regeneration. However, whether CNT-hydrogel composites actually influence neuronal differentiation and maturation, and how they do so remain elusive. In this study, CNT-hydrogel composites are prepared by in situ polymerization of poly(ethylene glycol) around a preformed CNT meshwork. It is demonstrated that the composites facilitate long-term survival and differentiation of pheochromocytoma 12 cells. Adult neural stem cells cultured on the composites show an increased neuron-to-astrocyte ratio and higher synaptic connectivity. Moreover, primary hippocampal neurons cultured on composites maintain morphological synaptic features as well as their neuronal network activity evaluated by spontaneous calcium oscillations, which are comparable to neurons cultured under control conditions. These results indicate that the composites are promising materials that could indeed facilitate neuronal differentiation while maintaining neuronal homeostasis.

Flexo-Ionic Effect of Ionic Liquid Crystal Elastomers

The first study of the flexo-ionic effect, i.e., mechanical deformation-induced electric signal, of the recently discovered ionic liquid crystal elastomers (iLCEs) is reported. The measured flexo-ionic coefficients were found to strongly depend on the director alignment of the iLCE films and can be over 200 µC/m. This value is orders of magnitude higher than the flexo-electric coefficient found in insulating liquid crystals and is comparable to the well-developed ionic polymers (iEAPs). The shortest response times, i.e., the largest bandwidth of the flexo-ionic responses, is achieved in planar alignment, when the director is uniformly parallel to the substrates. These results render high potential for iLCE-based devices for applications in sensors and wearable micropower generators.

Recent progress in self-healable ion gels

Ion gels, soft materials that contain ionic liquids (ILs), are promising gel electrolytes for use in electrochemical devices. Due to the recent surge in demand for flexible and wearable devices, highly durable ion gels have attracted significant amounts of attention. In this review, we address recent advances in the development of ion gels that can heal themselves when mechanically damaged. Light- and thermally induced healing of ion gels are discussed as stimuli-responsive healing strategies, after which self-healable ion gels based on supramolecular and dynamic covalent chemistry are addressed. Tough, highly stretchable, and self-healable ion gels have recently been fabricated through the judicious design of polymer nanostructures in ILs in which polymer chains and IL cations and anions interact. The applications of self-healable ion gels to electrochemical devices are also briefly discussed.

Poly(ethylene glycol) Diacrylate Based Electro-Active Ionic Elastomer

Preparation and low voltage induced bending (converse flexoelectricity) of crosslinked poly(ethylene glycol) diacrylate (PEGDA), modified with thiosiloxane (TS) and ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) (IL) are reported. In between 2µm PEDOT:PSS electrodes at 1 V, it provides durable (95% retention under 5000 cycles) and relatively fast (2 s switching time) actuation with the second largest strain observed so far in ionic electro-active polymers (iEAPs). In between 40 nm gold electrodes under 8 V DC voltage, the film can be completely curled up (270° bending angle) with 6% strain that, to the best of the knowledge, is unpreceded among iEAPs. These results render great potential for the TS/PEGDA/IL based electro-active actuators for soft robotic applications.

Gelating Abilities of Two-Component System of Catecholic Derivatives and a Boronic Acid

In the last two decades, various kinds of the low-molecular-weight organogelators (LMOGs) have been investigated in terms of technological applications in various fields as well as their fundamental scientific properties. The process of gelation is generally considered to arise from immobilization of the solvents in the three-dimensional networks formed by the assembly of gelator molecules through weak intermolecular noncovalent interactions. From these points of view a huge number of organogelators have been developed so far. In the course of our research on LMOGs we have noticed a mixture of two gelators could show a different trend in gelation compared to the single gelator. It is well known that the catecholic moiety easily forms cyclic boronate esters with the boronic acid. Thus, we have investigated the two-component system based on cyclic boronate esters formed by the catechols and a boronic acid in terms of the control of gelation capability. Basic gelation properties of the constituent catecholic gelators have also been clarified. The catecholic gelators with the amide unit form no gel by addition of the boronic acid. In contrast, the catecholic gelators with the glutamic acid moiety improve their gelation abilities by mixing with the boronic acid. Furthermore, the gelation ability of the catecholic gelators having the urea unit is maintained after addition of the boronic acid. It has been found that gelation abilities of the catecholic gelators are highly affected by addition of the boronic acid. In terms of practical applications some gels can be obtained by on-site mixture of two kinds of solutions.

PVDF based ionogels: applications towards electrochemical devices and membrane separation processes

Ionogels have emerged as one of the most interesting and captivating form of composites which credits to the outstanding characteristics. One of the most important constituent of ionogels is ionic liquid, which show many attractive properties notably non-volatility, in-flammability, negligible vapor pressure, tunability, thermal stability and solvating ability. A large variety of matrix materials have been under consideration for ionogels, presently, polymer/ionic liquid based ionogels have attracted much attention. Numerous polymeric materials such as have been utilized for these polymer/ionic liquids based ionogels. Polyvinylidene fluoride (PVDF) has been on top of the line as a matrix material for polymer based ionogels owing to its stability, aging and chemical resistance and mechanical strength. This review is primarily concerned with the properties of polyvinylidene fluoride based ionogels with an emphasis on their applications in various domains electrochemical devices, gas separation and liquid/liquid separations.

Low-voltage-driven soft actuators

Soft actuators based on electroactive polymers (EAPs) are the core constituents of future soft robots owing to their fascinating properties such as lightweight, compactness, easy fabrication into various forms, and low cost. Ionic EAP actuators are particularly attractive owing to the low driving voltages (<3 V) as compared to those of electronic EAP actuators (usually kilovolts). This paper presents a brief overview of the recent progress in a range of EAP actuators by focusing on low voltage operation, in addition to the challenges and future strategies for their wide applicability in artificial muscles and various innovative soft robot technologies.

Beyond Covalent Crosslinks: Applications of Supramolecular Gels

Traditionally, gels have been defined by their covalently cross-linked polymer networks. Supramolecular gels challenge this framework by relying on non-covalent interactions for self-organization into hierarchical structures. This class of materials offers a variety of novel and exciting potential applications. This review draws together recent advances in supramolecular gels with an emphasis on their proposed uses as optoelectronic, energy, biomedical, and biological materials. Additional special topics reviewed include environmental remediation, participation in synthesis procedures, and other industrial uses. The examples presented here demonstrate unique benefits of supramolecular gels, including tunability, processability, and self-healing capability, enabling a new approach to solve engineering challenges.

Organogel-assisted topochemical synthesis of multivalent glyco-polymer for high-affinity lectin binding

An organogelator, 2,4-undeca-diynyl-4',6'-O-benzylidene-β-d-galactopyranoside, which aligns its diacetylene upon gelation, has been synthesized. UV irradiation of its gel resulted in topochemical polymerization of the gelator forming polydiacetylene (PDA). We have used this gel-state reaction for the synthesis of surface-immobilized multi-valent glycoclusters, which showed 1000-fold enhanced binding, compared to monomers, with various galactose-binding lectins.

Surface Charge-Induced Efficient Recovery of Ionic Liquids from Aqueous Phase

Ionic liquids (ILs), which consist of pure cations and anions, are widely used in diverse applications and regarded as one of the best choices of "green solvents." However, the lack of effective green methods for recovering ILs and the safety issues caused by entering environment severely hinder the application of ILs in the green chemistry. Here, we show that rationally tuning the surface charge of a poly(tert-butyl acrylate) (PtBA)-coated porous mesh can selectively let ILs pass through, thus providing an efficient and convenient strategy to recover ILs. The surface charge of the porous mesh can be precisely controlled by regulating the hydrolysis degree of the chemically grafted PtBA coating. PtBA-coated porous mesh with a proper surface charge can be tuned to be IL-philic for a specific IL but hydrophobic, and thus can be applied to recover various kinds of ILs from the aqueous phase. This study offers a new platform for the development of functional membranes for efficient recovery of ILs.

Green Processing of Carbon Nanomaterials

Carbon nanomaterials (CNMs) from fullerenes, carbon nanotubes, and graphene are promising carbon allotropes for various applications such as energy-conversion devices and biosensors. Because pristine CNMs show substantial van der Waals interactions and a hydrophobic nature, precipitation is observed immediately in most organic solvents and water. This inevitable aggregation leads to poor processability and diminishes the intrinsic properties of the CNMs. Highly toxic and hazardous chemicals are used for chemical and physical modification of CNMs, even though efficient dispersed solutions are obtained. The development of an environmentally friendly dispersion method for both safe and practical processing is a great challenge. Recent green processing approaches for the manipulation of CNMs using chemical and physical modification are highlighted. A summary of the current research progress on: i) energy-efficient and less-toxic chemical modification of CNMs using covalent-bonding functionality and ii) non-covalent-bonding methodologies through physical modification using green solvents and dispersants, and chemical-free mechanical stimuli is provided. Based on these experimental studies, recent advances and challenges for the potential application of green-processable energy-conversion and biological devices are provided. Finally, a conclusion section is provided summarizing the insights from the present studies as well as some future perspectives.

Ultrastretchable Iono-Elastomers with Mechanoelectrical Response

The emerging technologies involving wearable electronics require new materials with high stretchability, resistance to high loads, and high conductivities. We report a facile synthetic strategy based on self-assembly of concentrated solutions of end-functionalized PEO₁₀₆-PPO₇₀-PEO₁₀₆ triblock copolymer in ethylammonium nitrate into face-centered cubic micellar crystals, followed by micelle corona cross-linking to generate elastomeric ion gels (iono-elastomers). These materials exhibit an unprecedented combination of high stretchability, high ionic conductivity, and mechanoelectrical response. The latter consists of a remarkable and counterintuitive increase in ion conductivity with strain during uniaxial extension, which is reversible upon load release. Based on in situ SAXS measurements of reversible crystal structure transformations during deformation, we postulate that the origin of the conductivity increase is a reversible formation of ion nanochannels due to a novel microstructural rearrangement specific to this material.

Ionic Liquid Crystals: Versatile Materials

This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

Surface Modification of Multiwalled Carbon Nanotubes with Cationic Conjugated Polyelectrolytes: Fundamental Interactions and Intercalation into Conductive Poly(methyl methacrylate) Composites

This research investigates the modification and dispersion and of pristine multiwalled carbon nanotubes (MWCNTs) through a simple solution mixing technique based on noncovalent interactions between poly(phenylene ethynylene)-based conjugated polyelectrolytes functionalized with cationic imidazolium solubilizing groups (PIM-2 and PIM-4) and MWCNTs. Spectroscopic studies demonstrated the ability of PIMs to strongly interact with and efficiently disperse MWCNTs in different solvents, mainly due to π interactions between the PIMs and the MWCNTs. Transmission electron microscopy and atomic force microscopy revealed the coating of the polyelectrolytes on the walls of the nanotubes. Scanning electron microscopy (SEM) studies confirm the homogeneous dispersion of PIM-modified MWCNTs in the poly(methyl methacrylate) (PMMA) matrix. The addition of 1 wt % PIM-modified MWCNTs to the matrix has led to a significant decrease in DC resistivity of the composite (13 orders of magnitude). The increase in electrical conductivity and the improvement in the thermal and mechanical properties of the membranes containing the PIM-modified MWCNTs is ascribed to the formation of MWCNT networks and cross-linking sites that provided channels for the electrons to move in throughout the matrix and reinforced the interface between MWCNTs and PMMA.

Ionic liquid-assisted exfoliation and dispersion: stripping graphene and its two-dimensional layered inorganic counterparts of their inhibitions

Research on graphene-monolayers of carbon atoms arranged in a honeycomb lattice-is proceeding at a relentless pace as scientists of both experimental and theoretical bents seek to explore and exploit its superlative attributes, including giant intrinsic charge mobility, record-setting thermal conductivity, and high fracture strength and Young's modulus. Of course, fully exploiting the remarkable properties of graphene requires reliable, large-scale production methods which are non-oxidative and introduce minimal defects, criteria not fully satisfied by current approaches. A major advance in this direction is ionic liquid-assisted exfoliation and dispersion of graphite, leading to the isolation of few- and single-layered graphene sheets with yields two orders of magnitude higher than the earlier liquid-assisted exfoliation approaches using surface energy-matched solvents such as N-methyl-2-pyrrolidone (NMP). In this Minireview, we discuss the emerging use of ionic liquids for the practical exfoliation, dispersion, and modification of graphene nanosheets. These developments lay the foundation for strategies seeking to overcome the many challenges faced by current liquid-phase exfoliation approaches. Early computational and experimental results clearly indicate that these same approaches can readily be extended to inorganic graphene analogues (e.g., BN, MoX2 (X = S, Se, Te), WS2, TaSe2, NbSe2, NiTe2, and Bi2Te3) as well.

Fullerene-ionic-liquid conjugates: a new class of hybrid materials with unprecedented properties

A modular approach has been followed for the synthesis of a series of fullerene-ionic-liquid (IL) hybrids in which the number of IL moieties (two or twelve), anion, and cation have been varied. The combination of C60 and IL give rise to new unique properties in the conjugates such as solubility in water, which was higher than 800 mg mL(-1) in several cases. In addition, one of the C60 -IL hybrids has been employed for the immobilization of palladium nanoparticles through ion exchange followed by reduction with sodium borohydride. Surprisingly, during the reduction several carbon nanostructures were formed that comprised nano-onions and nanocages with few-layer graphene sidewalls, which have been characterized by means of thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM-EDAX), and high-resolution transmission electron microscopy (HRTEM). Finally, the material thus obtained was successfully applied as catalyst in Suzuki and Mizoroki-Heck reactions in a concentration of just 0.2 mol %. In the former process it was recyclable for five runs with no loss in activity.

Chemical doping enhances electronic transport in networks of hexabenzocoronenes assembled in non-aqueous electrolyte

The electronic transport properties of HBC networks in non-aqueous electrolyte are tailored using synthetic chemistry and supramolecular design principles.

Entrapping an ionic liquid with nanocarbon: the formation of a tailorable and functional surface

An interface microenvironment between nanocarbon and ionic liquids (ILs) is presented. By an entrapping effect, a few layers of ILs can be finely deposited on the surface of nanocarbon, endowing amazingly tailorable surface properties. The entrapped IL layer, which was believed to be unable to be charred under pyrolysis conditions alone, can be further carbonized to a functional carbon layer. C, B, and N were confirmed to share the same hexagonal ring in the resultant layer, which provides more designable electronic properties.

Tough nanocomposite ionogel-based actuator exhibits robust performance

Ionogel electrolytes can be fabricated for electrochemical actuators with many desirable advantages, including direct low-voltage control in air, high electrochemical and thermal stability, and complete silence during actuation. However, the demands for active actuators with above features and load-driving ability remain a challenge; much work is necessary to enhance the mechanical strength of electrolyte materials. Herein, we describe a cross-linked supramolecular approach to prepare tough nanocomposite gel electrolytes from HEMA, BMIMBF₄, and TiO₂ via self-initiated UV polymerization. The tough and stable ionogels are emerging to fabricate electric double-layer capacitor-like soft actuators, which can be driven by electrically induced ion migration. The ionogel-based actuator shows a displacement response of 5.6 mm to the driving voltage of 3.5 V. After adding the additional mass weight of the same as the actuator, it still shows a large displacement response of 3.9 mm. Furthermore, the actuator can not only work in harsh temperature environments (100°C and −10°C) but also realize the goal of grabbing an object by adjusting the applied voltage.

Multistimuli-responsive supramolecular gels: design rationale, recent advances, and perspectives

This manuscript presents a brief overview of recent advances in multistimuli-responsive supramolecular gels (MRSGs). The synthesis of MRSGs with faster and smarter responsive abilities to a variety of external stimuli, such as redox reagents, pH changes, ligands, and coupling reagents, is one key issue for the upgrade of current molecular motors, signal sensors, shape memory devices, drug delivery systems, display devices, and other devices. However, the design rules of MRSGs are still not well understood. The lack of information about the relationship between the spatial structure and gelation behavior of existing gelators means that the knowledge required to design new gelators by the addition of functional moieties to well-known gelators is lacking. Insights into the gelation pathway of known gelators may bring inspiration to researchers who want to exploit elegant designs and specific building blocks to obtain their own MRSGs with predictable stimuli-responsive abilities.

Host-guest nanocomposites of multiwalled carbon nanotubes and ionic liquids with controllable composition

It is widely believed that low-volatility is a defining characteristic of ionic liquids (ILs). Here we synthesize a series of host-guest nanocomposites containing multiwalled carbon nanotubes (MWCNTs) and ILs using the volatility of ILs under vacuum conditions. The nanocomposites with different IL contents can be easily obtained through simple physical methods. The interactions between IL and MWCNTs are thoroughly investigated. This new nanocomposite can be used both in carbon catalysis and IL catalysis.

Simultaneous electrochemical synthesis of few-layer graphene flakes on both electrodes in protic ionic liquids

Here we illustrate a simple and moderate electrochemical strategy to simultaneously harvest high-quality few-layer graphene flakes (<5 layers) from both a graphite anode and a graphite cathode in the protic ionic liquids. Specifically, the graphene flakes detached from cathodic graphite receive a defect healing.

'Bucky gel' of multiwalled carbon nanotubes as electrodes for high performance, flexible electric double layer capacitors

We report the preparation of a gelled form of multiwalled carbon nanotubes (MWCNTs) with an ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethane sulfonyl)imide (BMPTFSI)), referred to as 'bucky gel', to be used as binderless electrodes in electrical double layer capacitors (EDLCs). The characteristics of gelled MWCNTs are compared with pristine MWCNTs using transmission electron microscopy, x-ray diffraction and Raman studies. A gel polymer electrolyte film consisting of a blend of poly(vinylidene fluoride-co-hexafluoropropylene) and BMPTFSI, exhibiting a room temperature ionic conductivity of 1.5 × 10(-3) S cm(-1), shows its suitability as an electrolyte/separator in flexible EDLCs. The performance of EDLCs, assembled with bucky gel electrodes, using impedance spectroscopy, cyclic voltammetry and charge-discharge analyses, are compared with those fabricated with pristine MWCNT-electrodes. An improvement in specific capacitance (from 19.6 to 51.3 F g(-1)) is noted when pristine MWCNTs are replaced by gelled MWCNT-binderless electrodes. Although the rate performance of the EDLCs with gelled MWCNT-electrodes is reduced, the pulse power of the device is sufficiently high (~10.5 kW kg(-1)). The gelled electrodes offer improvements in energy and power densities from 2.8 to 8.0 Wh kg(-1) and 2.0 to 4.7 kW kg(-1), respectively. Studies indicate that the gel formation of MWCNTs with ionic liquid is an excellent route to obtain high-performance EDLCs.

Polyetherimide/bucky gels nanocomposites with superior conductivity and thermal stability

Polyetherimide (PEI) nanocomposites comprising bucky gels of industrial-grade multiwalled carbon nanotubes (MWCNTs) and ionic liquid (IL, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6])) were prepared. The processing framework for this nanocomposite is simple, reproducible, and easily scalable. The strong interaction between IL and MWCNTs caused the latter to uniformly disperse in the PEI matrix while IL flowed into the gaps between the nanotubes' walls. The nanocomposite exhibited an enhanced conductivity of 2.01 × 10(4) Ω·cm volume resistivity at room temperature; the value decreased dramatically by 12 orders of magnitude, compared to pristine PEI. The IL free ions and MWCNTs networks provided excellent channels for electron transfer. PEI/bucky gels nanocomposites also showed improved thermal stability and high tensile strength. Other than having antiwear properties, this material can have numerous applications in the aerospace and electronics industries. Moreover, our work presents a "green" method toward modified nanocomposites industrial production as IL is environmentally safe and is easily recyclable.

Functionalization of reduced graphene oxides by redox-active ionic liquids for energy storage

The reduced graphene oxides (RGOs) functionalized by pyridinium-based ionic liquids (ILs) with SCN anions revealed 6-fold higher capacitance compared to that of RGOs due to the redox behavior of ILs as well as good rate capability and cycle stability despite the appearance of pseudo-capacitance.