Ionic Liquid-based Polymer Electrolyte Research Articles

Solid polymer electrolytes with dual salts enhance lithium-metal interfacial stability for long cycle performance of lithium batteries

Solid-state lithium metal batteries (LMBs) are considered to be the ideal energy storage system for achieving higher energy density and high safety. However, poor physical contact at the interface between the solid-state electrolyte and lithium metal, as well as the growth of dendrites make the cycling stability of LMBs challenging. Therefore, we developed a multifunctional ionic liquid-based polymer electrolyte including montmorillonite (MMT) and double salts (NaFSI and LiTFSI). The self-concentration effect of MMT lithium ions, combined with the electrostatic shielding effect of the double salts, resulted in homogeneous ion deposition, reducing dendritic lithium generation and improving lithium battery performance, with lithium batteries achieving a stable cycling rate of 1000 cycles at 1 C. Moreover, Due to the integrated assembly of the battery assembly process using light curing, the physical interface between the positive electrode-electrolyte-negative electrode achieves good contact and wettability. NaFSI achieves the enhancement of solid electrolyte interface (SEI) by introducing NaF/LiF to SEI of lithium metal, and the optimization of ion deposition pattern at the interface can be achieved by electrostatic shielding effect. Ultimately, stable ion transport at the solid-solid interface for lithium metal solid-state batteries can be realized. Notably, the ionic liquid-based polymer electrolyte with high ionic conductivity (1.2 × 10−3 S cm−1) and high oxidative stability (5.2 V vs. Li/Li+) at room temperature. In addition, the good flame retardant properties of the electrolytes indicate that dual-salt polymer electrolytes are an effective strategy for achieving high safety and long cycle stability of LMBs.

High-performance flexible planner device featuring WS2 electrode and non-aqueous polymeric ionic electrolytes incorporated with ionic liquid and dual redox additives

Introducing redox-active species to enhance redox-activity at electrode–electrolyte interfaces, and designing the rational architecture of flexible supercapacitors comprising high-performance active materials and electrolytes with a wide potential window would be a key strategy to boost energy and power density. Herein, for the first time, we prepared an ionic liquid-based polymer electrolyte (IL/PE) by entrapping ionic liquid N-methyl-N-butyl pyrrolidinium bis (trifluoromethane sulfonyl) imide (P14TFSI)) in a polymer electrolyte Poly (diallyl dimethylammonium bis (trifluoromethane sulfonyl) imide (PDADMATFSI)) and blended with dual redox-additives (potassium iodide, KI and diphenylamine, DPA). The IL/PE with dual redox additives, demonstrates spectacular flexibility, high ionic conductivity (∼23.8 × 10−4 S cm−1), and stability in a wide potential window (∼5.9 V). A symmetrical interdigitated planner device is fabricated using dual redox-active IL/PE and flower-like WS2 electrode material. Benefiting from the synergistic effect of dual redox-active additive, the highest energy density of 47.86 µWh cm−2 at a power density of 3509 µW cm−2, and a high working potential (3 V) with excellent cycling stability upto 20,000 cycles has been achieved.

Study and Characterization of Solid State, Flexible, Wire-Shaped Supercapacitor for Textile Energy Storage Purpose

Flexible and lightweight energy storage devices have become increasingly important for the development of wearable and portable electronics. In this work, we present a novel wire-shape supercapacitor based on carbon nanotube (CNT) yarns and an ionic liquid based polymer electrolyte. The combination of these materials offers high surface area, high conductivity and excellent flexibility, making them a promising candidate for flexible energy storage.The CNT yarns were characterized in a three-electrode configuration by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) either in water-based electrolytes and polymer electrolytes. The polymer electrolytes were prepared by mixing polymers with ionic liquid, which was characterized by thermal analysis and electrochemical measurements.The wire-shape supercapacitor was assembled by coating two CNT yarns with the polymer electrolyte and twisting them together. The devices exhibited high specific capacitance for a waterless system, additionally, they maintained their performance even under extreme deformation: the flexibility of the devices were tested by bending at different angles .Overall, this work highlights the advantages of using CNT yarns and ionic liquid polymer electrolytes for the development of flexible and high-performance supercapacitors. The wire-shape design of the device offers additional advantages for integration into wearable or flexible electronics, providing a promising path towards the development of highly efficient and adaptable energy storage systems.

Insight into the use of ionic liquid-based polymer electrolyte for super capacitor application

In this study, we are presenting the recent progress toward PEO-based polymer electrolytes doped with low viscosity ionic liquids with a strong emphasis on ionic liquid doped-in polymer electrolytes for energy storage applications, particularly towards electric double layer capacitors. The reliable transmission mechanism suggested by previous researchers to address the increasing trend in transport properties is ascertained with a sharp sense of the presence of different concentrations of interaction, i.e. polymer ionic liquid was also presented in detail.

Solvent-free green synthesis of nonflammable and self-healing polymer film electrolytes for lithium metal batteries

Fire-resistant and self-healing flexible electrolytes are a promising alternative to address thermal runaway in lithium batteries. However, self-healing electrolytes for lithium batteries are not widely used due to their low ionic conductivity, limited self-healing ability, and potential combustion risk. Ionic liquid-based polymer electrolytes are a simple and effective approach to obtaining polymer solid electrolytes with high ionic conductivity, fast self-healing and flame retardant properties. In this work, methyl methacrylate (MMA) and 1-Allyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide (AMIMTFSI) are used as the membrane-forming backbone and also possess ion transport channels. 1-ethyl-3 methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (EMIMTFSI) is added to the membrane to further enhance the ionic conductivity. Due to the existence of ionic liquid units and free ionic liquids in the prepared electrolytes, the fast interaction of ionic bonds confers a faster self-healing ability to the films, and the flame retardancy of the ionic liquids is fully maintained after polymerization. The prepared electrolytes show good flame retardance properties, excellent mechanical properties (tensile rate is ∼ 400%), high thermal decomposition temperature (>260 °C), and can effectively enhance the reliability of lithium metal batteries. When ionic liquids filler mass fraction is 40%, the polymer electrolytes have an ionic conductivity of 1.9 × 10-4 S cm−1, a decomposition voltage of 4.6 V (vs. Li/Li+), and can achieve an initial discharge capacity of 134.9 mAh g−1 with a capacity retention of 96.4% after 90 cycles at 0.1C for LiFePO4/Li half-cell at 25 °C.

Design and Fabrication of a High Performance Dssc Using Quasi-Solid-State Ionic Liquid-Based Conducting Polymer Electrolytes

Design and Fabrication of a High Performance Dssc Using Quasi-Solid-State Ionic Liquid-Based Conducting Polymer Electrolytes

Momentous past and key advancements in ionic liquid mediated polymer electrolyte for application in energy storage

This review article discusses the recent advances of ionic liquid-based polymer electrolytes (ILPEs) to create innovative polymer electrolytes (PEs) and their applications in energy generation and storage. Ionic liquids (ILs) possess high ionic conductivity and are thermally, chemically, and electrochemically stable which enables their uses in electrochemical gadgets. Despite of these above-mentioned advantages, liquidus nature of ILs is the major curse for their practical application because of spillage and compactness issues. Thus, there is ever increasing need to immobilize ILs into some organic/inorganic frameworks that furnish great mechanical steadiness alongside saving the fundamental properties of ILs that can altogether give a huge scope of utilization to these materials. The ILPEs thus formed have been reported to have advantageous properties (such as high ionic conductivity, thermal, chemical, and electrochemical stability) as compared to conventionally used PEs. In this review, we have not only discussed the key advancement in the field of ILPEs but also exemplified how the adaptability of these technologically important materials especially in energy storage (rechargeable batteries) has shown momentous past and is riding toward a promising future.

Polybenzimidazole and ionic liquid composite membranes for high temperature polymer electrolyte fuel cells

Elevating the operating temperature of polymer electrolyte fuel cells (PEFCs) can facilitate the reaction kinetics and improve the CO tolerance of catalysts, and simplify the complex water-heat management system of fuel cells. In this study, we fabricated the ionic liquid-based polymer electrolyte that can operate up to 250 °C without external humidification. The membrane utilized polybenzimidazole (PBI) as the polymer matrix, and ionic liquids as the proton conductive fillers. Among all the investigated ionic liquids, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) shows favorable performance and stability. The PBI-[dema][TfO] composite membrane exhibits high proton conductivity of 108.9 mS cm−1 at 250 °C. The single cell with PBI-[dema][TfO] composite membrane and Pt/C as the electrode shows output performance of 144 and 62 mW/cm2 at 125 °C and 250 °C, respectively. This work demonstrates that it is very promising to fabricate high temperature PEFCs using the ionic liquid-based polymer electrolyte.

Ionic liquid-based novel polymer electrolytes: electrical and thermal properties

New polymer electrolytes have been prepared from room temperature ionic liquid (IL) and poly(vinylidene fluoride)-hexafluoropropylene copolymer [PVdF-HFP]. The variation of thermal and electrical properties with varying polymer to IL concentration was investigated. The electrolytes had high thermal stabilities. The IL-PVdF-HFP electrolytes were freestanding, flexible films with room temperature conductivities of the order of 10−3 S cm−1. Increase in conductivity was found with increasing IL and also with increasing temperature. Increase in conductivity can be attributed to the fact that with increasing IL amorphicity increases as evident from XRD result. Dielectric studies showed decrease in relaxation time with increasing IL concentration indicating increase in polymer segmental motion which result in increase in conductivity.

Alpha-MnO2 nanofibers/nitrogen and sulfur-co-doped reduced graphene oxide for 4.5 V quasi-solid state supercapacitors using ionic liquid-based polymer electrolyte

α-MnO2 nanofibers combined with nitrogen and sulfur co-doped reduced graphene oxide (α-MnO2/N&S-rGO) were prepared through simple hydrothermal and ball milling processes. Structural characterization results by X-ray diffraction, X-ray photoemission spectroscopy, electron microscopy and Raman spectroscopy demonstrated that α-MnO2 nanofibers with the average diameter of ~40 nm were well dispersed on N&S-rGO nanoflakes. The synthesized material was incorporated into supercapacitor (SC) electrodes and assembled with the quasi-solid-state electrolyte comprising N,N-Diethyl-N-methyl-N-(2-methoxy-ethyl)ammonium bis (trifluoromethyl-sulfonyl)amide [DEME][TFSA]/polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) to produce coin-cell SCs. Electrochemical performances of SCs were measured by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. From the electrochemical data, SC using α-MnO2/N&S-rGO exhibited a good specific capacitance of 165F g−1 at 0.25 A g−1 with a wide potential window of 0–4.5 V, corresponding to a high energy density of 110 Wh kg−1 and a power density of 550 W kg−1. In addition, it exhibited good electrochemical stability with a capacitance retention of 75% after 10,000 cycles at 1 A g−1 and a low self-discharge loss. The attained energy-storage performances indicated that the α-MnO2/N&S-rGO composite could be highly promising for high-performance ionic liquid-based quasi solid-state supercapacitors.

Broadband dielectric spectroscopy of BMPTFSI ionic liquid doped solid-state polymer electrolytes: Coupled ion transport and dielectric relaxation mechanism

Broadband dielectric spectroscopy has been used to explore the charge carrier transport and relaxation mechanisms in different compositions of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide doped poly(methylmethacrylate)-lithium bis(trifluoromethylsulfonyl)imide based solid polymer electrolytes. The free ion diffusivity and number density, which are directly linked with ion transport in ionic liquid based polymer electrolytes, are analyzed following the model of electrode polarization proposed by Macdonald–Trukhan. We have analyzed broadband dielectric spectra in terms of complex electric modulus formalism using two theoretical approaches such as Havrilliak–Negami and Kohlrausch–Williams–Watts functions. It has been observed that charge carrier diffusivity and dielectric relaxation time are strongly temperature dependent, following Vogel–Tammann–Fulcher behavior. It is also evident from the values of stretched exponent β that the relaxation behavior is highly non-exponential in these ionic liquid doped polymer electrolytes.

Structural, impedance and electrochemical double-layer capacitor characteristics of improved number density of charge carrier electrolytes employing potato starch blend polymers

Potato starch (PS)/graphene oxide (GO) blend–based solid polymer electrolyte has been doped with lithium trifluoromethanesulfonate (LiCF3SO3) via casting method. Lithium-based system is further infused with ionic liquid, 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) as a plasticizer to form a PS/GO/LiCF3SO3/[Bmim][Cl] electrolyte with improved conductivity characteristic. The ionic liquid–based polymer electrolyte PS/GO/LiCF3SO3/[Bmim][Cl] exhibits better physical properties based on structural characterisation and thermal analysis conducted. Values of linear sweep voltammetry (LSV) that evaluates the electrochemical potential window for salted and plasticized systems are 1.38 V and 1.92 V, respectively. Specific capacitance (Cs) values calculated from charge–discharge measurement and cyclic voltammetry (CV) for the plasticized system are higher compared with those for the salted system. From the galvanostatic charge–discharge analysis, the value of Cs obtained for PS/GO/LiCF3SO3/[Bmim][Cl] is 37.9 F g−1 at 0.6 mA cm−2 current density. The results from CV and galvanostatic charge–discharge analysis confirm the suitability of PS/GO/LiCF3SO3 and PS/GO/LiCF3SO3/[Bmim][Cl] for electrochemical double-layer capacitor (EDLC) application.

PEO + NaSCN and ionic liquid based polymer electrolyte for supercapacitor

In this study, initially ion conducting solid polymer electrolyte films (SPEs) based on polyethylene oxide (PEO) and sodium thiocyanate (NaSCN) have been prepared using the standard solution cast technique. For further enhancement in the ionic conductivity value of optimized film, an ionic liquid (IL; 1-ethyl-3-methyl-imidazolium tricyanomethanide) ([EMIM][TCM]) has been incorporated in different weight ratios into the optimized polymer-salt complex matrix. The prepared SPEs are free-standing, flexible and exhibit good thermal and mechanical stabilities. Polarized optical microscopy (POM) shows a change in the surface morphology of IL doped polymer electrolyte films. The composition nature of polymer electrolyte films was confirmed using fourier transform infrared spectroscopy (FT-IR) via studying ion-ion and ion-polymer interactions. The FTIR studies confirm that complexation occurs between polymer-salt and polymer-salt-ionic liquid interactions. Polymer electrolyte films have been also characterized using X-Ray Diffraction (XRD). The structural analysis confirms that the intensity of crystalline peaks existing in solid polymer electrolyte films decreases after doping IL which enhances its amorphous nature. The thermal stability of different prepared electrolyte films has been investigated using thermogravinometric analysis (TGA). Ionic liquid doped polymer electrolyte films show more stable behavior than polymer host PEO and polymer-salt complex at high temperatures. IL doped polymer electrolyte film shows reduction in the degradation process with a residue mass of 29% at 400 °C. Polymer electrolyte films were also characterized using impedance spectroscopy (IS) to check their electrical properties. The maximum ionic conductivity is found to be 8.44 × 10−5 S cm−1 for 4 wt% IL doped solid polymer electrolyte film and the calculated value of ionic transference number (tion) for optimized electrolyte film is 0.98. Using this maximum ion-conducting polymer electrolyte film, we have developed a electrical double layer capacitor (EDLC). The calculated value of the specific capacitance of prepared EDLC is 1.07 Fg−1.

WITHDRAWN: PVA + NaSCN and ionic liquid based polymer electrolyte for supercapacitor

WITHDRAWN: PVA + NaSCN and ionic liquid based polymer electrolyte for supercapacitor

Past, present and future of ionic liquid based polymer electrolytes

Polymer electrolyte(PE)s have been playing a major role in almost all modern electrochemical devices. Since their introduction, a great deal of research work has been done to uplift their performance and as a result, there are several milestones in the history of PEs. This review paper is mainly targeting the PEs based on ionic liquids (ILs). The main reason for the emergence of IL based PE is the ever increasing focus on safety issues as well as low ambient temperature of PEs. Desired electrochemical properties, less toxicity and the sound cooperativeness are some features of attraction towards these ILs. With the enormous amount of research work done on the area, it is an absolute necessity to summarize the outcomes and the trends to understand basics of the IL-PEs. In this paper, an introduction on setting up of background for PEs and IL based PEs is presented in section 1 and section 2 is dedicated to the history of PEs. Sections 3 and 4 will address the IL based PEs and their preparation techniques respectively. Properties and their characterization techniques are presented in section 5. Section 6 describes the optimization methods followed by applications and novel approaches in section 7.

Ion transport mechanism and dielectric relaxation behavior of PVA-imidazolium ionic liquid-based polymer electrolytes

Solid polymer electrolytes based on poly(vinyl alcohol) (PVA) with different wt% ionic liquid (IL), 1-Butyl-2, 3-dimethylimidazolium tetraflouroborate [BDMITFB] were prepared using the solution cast technique. Prepared samples were characterized using the AC impedance spectroscopic technique. AC conductivity spectra of a PVA-IL-based system at different concentrations/temperatures have been discussed. The fitted AC conductivity spectra using Jonscher’s power law (JPL) exhibits the correlated barrier hopping (CBH) type conduction mechanism. The scaled AC conductivity spectra of PVA-IL-based films with temperature/concentrations collapsed into a single master curve indicating the ion conduction mechanism have the same origin. For higher IL loaded samples (20 and 25 wt%) mobility, μ dc conductivity, σdc as well as total number density of charge carriers, N increases with increasing IL content in PVA. Dielectric permittivity (ε′ and ε″) and electric modulus (M′ and M″) study of prepared samples has been done. Temperature-dependent dc conductivity for prepared polymeric films follows the Arrhenius type thermally activated process.

Highly conductive and mechanically robust nanocomposite polymer electrolytes for solid-state electrochemical thin-film devices

Abstract Ionic liquid-based polymer electrolyte composites (PECs) with high mechanical strength and ionic conductivity were fabricated by using a semicrystalline homopolymer network. Morphological, mechanical, and electrical properties of semicrystalline homopolymer-based PECs were investigated over the composition range of 10–50 polymer wt%. The PECs consisted of poly(vinylidene fluoride) (PVDF) and a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]). The amorphous PVDF chains were solvated by the liquid electrolyte and interconnected the phase-separated PVDF crystalline-domains, acting as physical crosslinks. The ionic conductivity and specific capacitance of the homopolymer PECs were found to be very high, ranging from 0.4 to 4.9 mS/cm and from 2.6 to 9.1 μF/cm2, respectively. The elastic moduli of the PECs that range from 4 to 38 MPa were also greater than those of PECs prepared by using other polymeric networks. These PECs were successfully applied as electrolyte membranes in electrical double layer supercapacitors and as high-capacitance gate insulators in electrochemical thin-film transistors. These results provide detailed systematic data for fabricating high-performance solid polymer electrolytes for electrochemical thin-film devices.

Electrical, thermal, and dielectric studies of ionic liquid-based polymer electrolyte for photoelectrochemical device

In this work, solution cast method was adapted for the preparation of 1-ethyl-3-methylimidazolium dicyanamide (EMImDCN)-doped solid polymer electrolyte. Optimum composition of polymer electrolyte (polyethylene oxide + sodium iodide) was treated as the host polymer. The ionic conductivity was further enhanced by adding low-viscosity ionic liquid (IL) EMImDCN. Electrical, thermal, dielectric, and photoelectrochemical properties of polymer host and IL-doped solid polymer electrolyte (ILDPE) are presented in detail. An electrochemical device, that is, dye-sensitized solar cell was fabricated using maximum conducting ILDPE film, which shows short-circuit current density of 0.118 mA/cm2, open-circuit voltage of 0.71 V, and overall efficiency of 0.061% at 1 sun condition.

Electrochemical study of Ionic Liquid based polymer electrolyte with graphene oxide coated LiFePO4 cathode for Li battery

Ionic Liquid (IL) based polymer electrolytes using polymer poly ethylene oxide (PEO), salt lithium bis(fluoromethylsulfonyl)imide and IL N-propyl-N-methylpyrrolidinium-bisfluorosulfonylimide (PYR13FSI) are synthesized by solution cast method. Using different experimental techniques, good thermal stability and wide electrochemical window are observed for synthesized polymer electrolytes. Maximum Li+ conductivity is found for 10% IL containing polymer electrolyte so, it is used in Li cell preparation. LiFePO4 (LFP) cathode and graphene oxide wrapped LFP cathode (GO-LFP) are also prepared to observe the effect of graphene oxide coating in electrochemical performance of the Li cell. From charge –discharge process, high specific discharge capacity (~163 mAh g−1 at 0.1 C) is found for GO-LFP as compared to LFP cathode. GO-LFP cathode shows good cyclability and Coulombic efficiency up to 100 cycles. High charge-discharge capacity of GO-LFP is noticed even at higher current rate.

Energy storage in structural composites by introducing CNT fiber/polymer electrolyte interleaves

This work presents a method to produce structural composites capable of energy storage. They are produced by integrating thin sandwich structures of CNT fiber veils and an ionic liquid-based polymer electrolyte between carbon fiber plies, followed by infusion and curing of an epoxy resin. The resulting structure behaves simultaneously as an electric double-layer capacitor and a structural composite, with flexural modulus of 60 GPa and flexural strength of 153 MPa, combined with 88 mF/g of specific capacitance and the highest power (30 W/kg) and energy (37.5 mWh/kg) densities reported so far for structural supercapacitors. In-situ electrochemical measurements during 4-point bending show that electrochemical performance is retained up to fracture, with minor changes in equivalent series resistance for interleaves under compressive stress. En route to improving interlaminar properties we produce grid-shaped interleaves that enable mechanical interconnection of plies by the stiff epoxy. Synchrotron 3D X-ray tomography analysis of the resulting hierarchical structure confirms the formation of interlaminar epoxy joints. The manuscript discusses encapsulation role of epoxy, demonstrated by charge-discharge measurements of composites immersed in water, a deleterious agent for ionic liquids. Finally, we show different architectures free of current collector and electrical insulators, in which both CNT fiber and CF act as active electrodes.