Ionic Liquid Polymer Electrolyte Research Articles

Novel approach: Simultaneous application of ionic liquid doped polymer electrolyte in supercapacitor and dye-sensitized solar cells

The present study reports the synthesis, characterization, and application as energy devices of an ionic liquid blended polymer electrolyte film in which the host polymer polyvinyl alcohol (PVA) is mixed with low viscosity ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate. Various characterization tools have been used further to elaborate electrical, structural, and photoelectrochemical properties. X-ray diffraction (XRD) and polarized optical microscope (POM) affirm the reduction of crystallinity of polymer, while Fourier transform infrared spectroscopy (FTIR) shows complexation and composite nature. Electrochemical impedance spectroscopy shows an enhancement in ionic conductivity by IL doping, where the highest conductivity is achieved at 60 wt% of IL concentration with a conductivity value of 6.21 × 10⁻⁴ S/cm. The ionic transference number (tion) and electrochemical stability measurement show the film's predominantly ionic nature and a reasonable stability window. Using maximum conducting film sandwiched between electrodes, we have successfully fabricated two devices, i.e., an electrical double-layer capacitor (EDLC) and a dye-sensitized solar cell (DSSC). The fabricated EDLC capacitor shows a specific capacitance of 125 F/g, while DSSC shows an efficiency of 1.1 % at one sun condition.

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.

Influencing ionic conductivity and mechanical properties of ionic liquid polymer electrolytes by designing the chemical monomer structure

ABSTRACTPolymeric single chloride-ion conductor networks based on acrylic imidazolium chloride ionic liquid monomers AACXImCYCl as reported previously are prepared. The chemical structure of the polymers is varied with respect to the acrylic substituents (alkyl spacer and alkyl substituent in the imidazolium ring). The networks are examined in detail with respect to the influence of the chemical structure on the resulting properties including thermal behavior, rheological behavior, swelling behavior, and ionic conductivity. The ionic conductivities increase (by two orders of magnitude from 10−6 to 10−4 S·cm−1 with increasing temperature), while the complex viscosities of the polymer networks decrease simultaneously. After swelling in water for 1 week the ionic conductivity reaches values of 10−2 S·cm−1. A clear influence of the spacer and the crosslinker content on the glass transition temperature was shown for the first time in these investigations. With increasing crosslinker content, the Tg values and the viscosities of the networks increase. With increasing spacer length, the Tg values decrease, but the viscosities increase with increasing temperature. The results reveal that the materials represent promising electrolytes for batteries, as proven by successful charging/discharging of a p(TEMPO-MA)/zinc battery over 350 cycles.

A Flexible Solid Polymer Electrolyte based Polymerized Ionic Liquid for High Performance Solid‐State Batteries

AbstractSolid polymer electrolytes (SPEs) combine the benefits of ceramic electrolyte and polymer electrolyte, and have broad application prospects in high‐energy lithium metal batteries. However, low Li+ conductivity and tensile strength are crucial elements that hinder the application of solid polymer electrolytes. In this paper, an effective solid polymer electrolyte was proposed to solve these problems. A polymerized ionic liquid (PIL) was chosen as the ionic transport material to synthesize three‐dimensional cross‐linked ion channels through thermal polymerization, which can effectively improve the ionic conductivity. This work is different from some other reports that add ionic liquid without C=C double bond. We used the vinyl ionic liquid (IL) as matrix via polymerization with azobis initiator (AIBN) and the obtained co‐polymer has excellent flexibility and non‐flowing character. Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic filler was added to enhance the thermal stability and tensile strength of the electrolyte. Meanwhile, solid‐state batteries (SSBs) assembled with LiFePO4 cathode and high‐voltage LiNi0.8Co0.1Mn0.1O2 cathode can deliver remarkable cell performance. This work presents an appropriate device for the structure of modern polymerized ionic liquid solid polymer electrolytes, and shows significant implication for the progress of high‐property polymer electrolytes.

Highly conducting ionic liquid doped polymer electrolyte for energy storage applications

The main aim of the present work is to optimize highly conducting solid polymer electrolyte by doping of ionic liquid in Poly-ethylene oxide (PEO) polymer complexed Sodium Iodide (NaI) matrix. Solution casting method has been used to synthesis solid polymer electrolyte. Electrical, thermal, structural, and optical studies confirm the homogenous complexation of polymer electrolyte with ionic liquid. Furthermore, the electric double-layer capacitors (EDLCs) device and Dye Sensitized Solar Cell (DSSC) has been developed using high conducting ionic liquid (IL) polymer electrolyte with maximum conductivity, demonstrating that ionic liquids have a potential possibility to choose as electrolyte in developed energy devices.

Highly conducting corn starch doped ionic liquid solid polymer electrolyte for energy storage devices

In this study, a new biopolymer electrolyte (BPE) is successfully developed using corn starch complexed with ammonium iodide (NH4I) as host, and low viscosity ionic liquid 1-Ethyl, 3-Methyl Imidazolium Thiocyanate (EMImSCN), as a plasticizer. This ionic liquid doped BPE shows high ionic conductivity of the order 10−4 S/cm and electrochemical stability window more than 3 V, which is suitable for electrochemical application. The ionic transference number (tion) of 0.98 confirms the system to be predominantly ionic in nature. Fourier transform infrared spectroscopy (FTIR) shows complex nature, while polarized optical microscopy (POM) gives us an idea about the semi-crystalline nature of BPE. Maximum conducting ionic liquid doped BPE sandwiched electric double layer capacitor (EDLC) and dye sensitize solar cell (DSSC) shows efficient performance.

Highly efficient ionic‐liquid based solid polymer electrolyte for energy device (RAFM 2022)

We have successfully synthesized highly conducting polymer electrolyte incorporated ionic liquid films. There was a rise in conductivity by ionic liquid doping which is clarified by impedance spectroscopy. Fourier transform infra red spectroscopy confirms complexation as well as composite nature. Polarized optical microscopy shows decrease in crysatllinity (more amorphous) by ionic liquid doping. Maximum conducting ionic liquid incorporated polymer electrolyte sandwitched between electrodes, used for fabricating electrical double layer capacitor (EDLC) and dye sensitized solar cell (DSSC) further affirm that these ionic liquid doped polymer electrolyte could be a novel alternative in electrochemical devices.

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.

Ionic liquid doped solid polymer electrolyte: Synthesis, characterization and applications ICSEM-2021

In this paper, we have used polymer polyethylene oxide as a host matrix and novel electrolyte ionic liquid 1-ethyl-3-methylimidazolium tricyanomethanide as an dopant to increase ionic mobility. Different characterization techniques like Electrochemical impedance spectroscopy, dielectric measurement, Fourier transform, X-ray diffraction, polarized optical microscopy, thermogravinometric analysis were used to identify the electrical, optical, structural and thermal properties. A laboratory scale supercapacitor has been fabricated using optimized solid polymer electrolyte film as an electrolyte and porous carbon derived from corn starch which shows a specific capacitance 13.6 F/g at 50 mV/s scan rate.

Ultrastable Zinc Anodes Enabled by Anti-Dehydration Ionic Liquid Polymer Electrolyte for Aqueous Zn Batteries.

The side reaction and dendrite of a zinc anode in an aqueous electrolyte represent a huge obstacle for the development of rechargeable aqueous Zn batteries. An electrolyte with confined water is recognized to fundamentally stabilize the zinc anode. This work proposes acetamide/zinc perchlorate hexahydrate (AA/ZPH) ionic liquid (IL)-polyacrylamide (PAM) polymer electrolytes, here defined as IL-PAM. The novel Zn2+-conducting IL is able to accommodate trace water and can achieve both high conductivity (15.02 mS cm-1) and alleviation of side reactions (>90% reduction). Cross-linked PAM acts as the three-dimensional framework to suppress dendrites and obtain flexibility. As a result, the Zn anode with IL-PAM can cycle stably over 2000 h with a record highest cumulative capacity of 3000 mAh cm-2 and well-preserved morphology. Based on IL-PAM, the flexible LFP|Zn hybrid batteries can be successfully assembled and operate normally in series and parallel conditions. Moreover, the low volatility of IL and binding forces exerted by the PAM network endues IL-PAM with an anti-dehydration property. In a 50 °C unsealed environment, the weight loss of IL-PAM is about two-fifths of PAM hydrogel and an aqueous electrolyte, and the corresponding hybrid battery with IL-PAM can also prolong a 4 times longer lifespan.

A high energy flexible symmetric supercapacitor fabricated using N-doped activated carbon derived from palm flowers.

Nitrogen doped activated carbons of high surface area are synthesized using palm flower biomaterial by KOH activation followed by pyrolysis. The concentration of the activating agent KOH and carbonization temperature are found to be crucial to obtain high surface area activated carbon. The optimal concentration of KOH and carbonization temperature for the synthesis of activated carbon, respectively, are 2 M and 800 °C in the flow of nitrogen gas. The optimized conditions have been employed to further prepare nitrogen doped activated carbon (NAC) by varying the weight ratio of palm flowers to melamine. All activated carbons are characterized by powder XRD, BET analysis, RAMAN spectroscopy, HR-SEM analysis, HR-TEM analysis and FT-IR analysis. With 2 wt% nitrogen doping, the BET surface area and pore diameter of the NAC-2 sample are 1054 m2 g−1 and 1.9 nm, respectively. The electrochemical charge storage performance of the nitrogen doped activated carbons has been evaluated in an aqueous acidic electrolyte medium. The results indicate that among the nitrogen doped activated carbons, the NAC-2 sample exhibits the highest electrochemical capacitance of 296 F g−1 at 0.5 A g−1. The performance of the NAC-2 electrode is further tested in aqueous, ionic liquid and solid polymer electrolytes by assembling a symmetric capacitor for real time application. By employing an ionic liquid as the electrolyte, the device delivers an energy density of 8.6 Wh kg−1 and a power density of 38.9 W kg−1 in the voltage window of 1.5 V and at an operating current density of 0.1 A g−1. Interestingly, the NAC-2 electrode shows good cycling performance in the ionic liquid electrolyte (up to 50k cycles). Furthermore, the symmetric device in 0.1 M H2SO4/PVA solid state electrolyte shows excellent electrochemical stability under various bending angles, demonstrating its potential in flexible electronic devices.

Current Progress in Solid-State Electrolytes for Dye-Sensitized Solar Cells: A Mini-Review

Low-cost and high-performance dye-sensitized solar cells (DSSCs) are considered promising candidates for commercial application. As one of the crucial components, electrolytes are considered the limiting factor for long-term DSSC stability. As alternative materials, solid-state electrolytes have been used in DSSCs, which may solve the problem of liquid electrolytes, such as leakage and volatilization. In this review, we define solid-state electrolytes as inorganic hole transport materials (HTMs), organic HTMs, ionic conductive polymer electrolytes, and ionic liquid polymer electrolytes according to the different types of carriers and summarize the latest development trends of these electrolytes. We discuss in detail the mechanism of solid-state dye-sensitized solar cells (ssDSSCs), including the hole transfer process at the dye/hole-conductor interface and factors that reduce the efficiency of ssDSSCs, and summarize several methods to improve the efficiency and long-term stability of ssDSSCs. These may facilitate the research and development of electrolytes for ssDSSCs.

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.

A graphene oxide and ionic liquid assisted anion-immobilized polymer electrolyte with high ionic conductivity for dendrite-free lithium metal batteries

Development of solid polymer electrolytes (SPEs) with superior performance is crucial for high-energy density lithium metal batteries (LMBs). Herein, a graphene oxide (GO) and ionic liquid (IL) assisted anion-immobilized polymer electrolyte (PGI) is developed, which can effectively prevent the formation of Li dendrite of LMBs. Various characterizations show that the synergetic interactions among the poly (ethylene oxide) (PEO), GO and IL in PGI, greatly reduce the crystallinity of PEO. All of the amorphous PEO, GO, and IL can effectively tether anions and enhance the ionization of lithium salts, which lead to a uniform assignment of charges and lithium ions in the electrolyte, as well as increase the transfer number of lithium ions. The PGI is utilized in all-solid-state batteries with a negligible polarization. The galvanostatic cycling tests (LiFePO4/Li cells using PGI electrolytes) at 60 °C show the initial capacities of 156.2 and 120 mAh g−1 at 0.1C and 0.5C, respectively. Moreover, the electrochemical tests also indicate that the LMBs using PGI electrolytes possess superior cycle stability at room temperature. The study provides a competitive solution for developing high-performance LMBs which can work well at both high temperature and room temperature.

Corn-starch based porous carbon and IL based electrolyte for high efficient supercapacitor

The corn-starch based porous carbon was synthesized using two step process and characterized. Also, a highly conducting ionic liquid doped polymer electrolyte was sandwiched between electrodes. The conductivity and specific capacitance of electrolyte and electrode of a capacitor was calculated using different characterization techniques.

A Novel Polymer Electrolyte Matrix Incorporating Ionic Liquid into Waterborne Polyurethane for Lithium-Ion Battery.

Ionic liquid has relatively high conductivity at room temperature and good electrochemical stability. Ionic liquid polymer electrolytes have some advantages of both ionic liquid and polymer. In this work, 1-alkyl-3-(2′,3′-dihydroxypropyl)imidazolium chloride (IL-Cl) was incorporated into waterborne polyurethane chain to composite all-solid-state polymer electrolyte matrices. The structure, thermal stability, mechanical property and ionic conductivity of the matrices were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric Analysis (TGA), tensile measurement and electrochemical impedance spectroscopy (EIS). The results demonstrated that when the content of IL-Cl was 14 wt%, the mechanical property of film was optimized, with a maximum tensile strength of 36 MPa and elongation at break of 1030%. In addition, as for the film with IL-Cl content of 16 wt%, its oxygen index value increased to 25.2% and ionic conductivity reached a maximum of 1.2 × 10−5 S·cm−1 at room temperature, showing high flame retardancy and ionic conductivity.

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.

Ionic Liquid–Organic Solvent Mixture-Based Polymer Gel Electrolyte with High Lithium Concentration for Li-Ion Batteries

In this paper, we have investigated the performance and solid electrolyte interphase formation (SEI) of a hybrid polymer gel electrolyte based on poly(vinylidene fluoride)-co-hexafluoropropylene, 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide ([Py1,4]FSI), and lithium bis(fluorosulfonyl)imide (LiFSI) for all solid-state lithium-ion batteries. The effect of the addition of acetonitrile (AN) and different concentrations of LiFSI to such a polymer gel electrolyte was also examined. Compared to 1 M LiFSI in the ionic liquid–polymer electrolyte, the addition of 4 M LiFSI along with acetonitrile led to higher lithium storage capacity. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy were performed to analyze the SEI formation on a Ge electrode. The difference in the mechanical properties and SEI composition was observed upon changing the components of the polymer electrolyte. XPS analysis revealed a difference in the composition/thickness of the SEI layer, which varies upon increasing the Li-salt concentration and upon adding AN to [Py1,4]FSI. Such differences might have led to better Li storage capacity on using the concentrated IL–organic polymer electrolyte. Our study clearly shows that the addition of an organic solvent and high concentration of Li salt to the polymer gel electrolyte improves the performance of LIBs.

Ionic polymer actuators using poly(ionic liquid) electrolytes

In this work, poly(ionic liquid) (polyIL) polymer electrolytes were prepared by the free radical copolymerization of IL monomers with a plasticizing monomer having poly(ethylene glycol) (PEG) side chain. The IL monomers, i.e., the polycation and polyanion precursors, were 1-[(3-methacryloyloxy)propyl]-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C3mim-MA][TFSA]) and 1-methyl-3-propylimidazolium N-[3-(methacryloyloxy)propylsulfonyl]-N-(trifluoromethanesulfonyl)amide ([C3mim][TFSA-MA]), respectively. The ionic conductivities of the polyIL polymer electrolytes increased with a decrease in the weight fraction of the ionic monomer owing to the plasticizing effect of the PEG side chain, whereas the mechanical strength simultaneously decreased due to a lowering in the glass transition temperature of the electrolytes. The ionic conductivities of the electrolytes were 10−6–10−7 S cm−1 at room temperature. Ionic polymer actuators were fabricated using the polyILs as an electrolyte layer by sandwiching the electrolyte membrane with two carbon electrodes. The displacement behavior depended entirely on the fixed charge on the polymer chain.

Ionic Liquid Enhanced Polymer Elcetrolytes for Environmental Friendly Electric Double Layer Capacitors

In this study we perform the preparation and characterization of poly (vinyl alcohol) (PVA)–added ionic liquid based ion conductors. The polymer electrolyte is incorporated with magnesium triflate [Mg(CF3SO3)2 or MgTf] as salt and 1–butyl–3–methylimidazolium bromide (BmImBr) as an environmental friendly ionic liquid. Differential scanning calorimetry (DSC) is carried out to investigate the glass transition temperature (Tg ), which is used to study the plasticizing effect of the ionic liquid. The polymer electrolyte with the lowest Tg gives the highest ionic conductivity value of (1.64±0.01) x 10-3 S cm-1 at 60 wt.% of BmImBr. This is attributed to the plasticizing effect of the ionic liquid, which increases the flexibility of the polymer backbone, hence increasing the ionic mobility and segmental motion of the ions. The highest conducting ionic liquid based polymer electrolyte is used to fabricate electrical double layer capacitors (EDLC). The electrochemical potential window is evaluated using linear sweep voltammetry (LSV). Electrochemical capacitance of the EDLC is evaluated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The electrochemical potential window of ionic liquid–added polymer electrolyte is extended from 1.35 V to 2.6 V. Cyclic voltammetry (CV) proves the improvement in specific capacitance of the electrical double layer capacitors (EDLCs) containing ionic liquid–added polymer electrolyte by increasing the specific capacitance from 1.41 Fg-1 in the ionic liquid free polymer electrolyte to 45.95Fg-1 for the 60 wt% ionic liquid added polymer electrolyte. Keywords: Poly(vinyl alcohol); Ionic liquid; Mg(CF3SO3)2 , EDLC; Capacitance