Ion Conducting Gel Polymer Electrolyte Research Articles

A sodium ion conducting gel polymer electrolyte with counterbalance between 1-ethyl-3-methylimidazolium tetrafluoroborate and tetra ethylene glycol dimethyl ether for electrochemical applications.

For sodium batteries, the development of gel polymer electrolytes (GPEs) with remarkable electrochemical properties is in its early stage and persists to be a challenge. In this report we have synthesized a series of GPEs containing a poly(vinyllidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and poly (methyl methacrylate) (PMMA) as blend polymer, sodium perchlorate (NaClO4) as ion-conducting salt and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) and tetra ethylene glycol dimethyl ether (TEGDME) as molecular solvents. The counter balance between EMIM-BF4 and TEGDME is maintained by the electrolyte, which is formed through the optimal weight ratio of 2 : 1. GPEs have an advantageous set of properties, including stability window of 5 V, Na+ transference number of 0.20, and a room-temperature ionic conductivity of 5.8 × 10-3 S cm-1. According to enthalpy and entropy calculations, optimized GPE yields the highest amount of disorder or amorphicity and contributes to greatest conductivity. XRD analysis supports this argument. Thermal investigations show that optimized GPE may preserve gel phase up to 125 °C. The prototype sodium cell fabricated with optimize GPE has a specific capacity of 281 mA h g-1 and open circuit voltage of 2.5 V. The optimized GPE exhibits potential for future electrochemical applications.

High‐performance sodium ion conducting gel polymer electrolyte based on a biodegradable polymer polycaprolactone

AbstractGel polymer electrolytes (GPEs) are gaining recent focus for high‐performance quasi‐solid‐state energy storage devices owing to their high ionic conductivity, good interfacial properties, flexibility with high safety in comparison to liquid electrolytes. Among various polymer hosts, developed so far, polycaprolactone (PCL) is attractive for its biodegradable and biocompatible nature. In this report, we demonstrate a novel GPE composition incorporating a liquid electrolyte 1 M sodium triflurosulfonate (NaTf) in ethylene carbonate (EC):propylene carbonate (PC) mixture, immobilized in PCL as the host polymer in the form of mechanically stable, free‐standing and flexible thick films. The GPE films are characterized using various physicochemical and electrochemical techniques. The GPE comprising an approximately 80 wt.% concentration of liquid electrolyte offers an optimum ionic conductivity of ~1.3 × 10−3 S cm−1, wide electrochemical stability window up to approximately 4.3 V and high sodium ion transport number (tNa+ ~ 0.67) at room temperature. Besides, the GPE film is thermally stable up to approximately 100°C. The sodium stripping/plating tests reveal highly stable cycling under ±46 mV for over 100 hours followed by ±30 mV at a current density of 0.05 mA cm−2 indicating reversible Na‐plating/stripping behavior. The high Na+‐conductivity and suitable Na‐storage properties make a favorable biodegradable electrolyte for practical sodium‐ion battery applications.

Structural and impedance analysis of PAN-based Na+ ion conducting gel polymer electrolytes for energy storage device application

The polymer electrolytes are used in energy storage devices. Sodium ion-conducting gel polymer electrolytes based on Polyacrylonitrile (PAN) complexed with an alkali salt (NaI) and Ethylene carbonate (EC) and Dimethylformamide (DMF) as plasticizing solvents were prepared from solution cast method. The developed membrane were dimensionally stable. Structural, Impedance and conductivity studies were carried on to the prepared samples. The electrical studies were performed using lab-made conductivity setup. The complex formation between NaI salt and PAN had been confirmed by XRD studies and revealed the amorphous behaviour of the prepared membranes. The conductivity and bulk resistance of gel polymer electrolytes were measured by impedance analysis by changing the composition concentration of PAN-NaI. The maximum conductivity (1x10-3 S/cm) was observed for PAN: NaI (70:30) at temperature 373 K. The conductivity dependence temperature of these mebranes obeys the principle of Arrhenius.

Robust and Highly Ion-Conducting Gel Polymer Electrolytes with Semi-Interpenetrating Polymer Network Structure

Here we report gel polymer electrolytes (GPEs) formed by the film casting of the solution containing poly(ethylene glycol) methyl ether methacrylate (PEGMA) and trimethylolpropane ethoxylate triacrylate (ETPTA) with poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), followed by the thermal radical polymerization and liquid electrolyte absorption. The resulting GPEs show a semi-interpenetrating polymer network (SIPN) structure that provides film robustness which is investigated by morphological, structural, and electrochemical studies. Particularly, the GPE prepared by the composition of 98 mol% PEGMA and 2 mol% ETPTA in the presence of 40 wt% of PVDF-HFP (relative to total amount of PEGMA and ETPTA) manifests large ionic conductivity (1.46 × 10−3 S cm−1) and tensile strength (6.28 MPa at elongation at break of 156%) at a room temperature due to large uptake of the liquid electrolyte (up to 267%) and SIPN structure. We also verify that the GPE is electrochemically stable up to 4.7 V (vs. Li/L+), suggesting it holds the great promise of a polymer electrolyte membrane for energy storages such as rechargeable batteries or supercapacitors.

Sulfonylimide-Based Cation Exchange Membranes As Electrolyte for Lithium-Ion Batteries. Synthesis and Characterization

The use of cation-exchange membranes as electrolytes in lithium-ion batteries is considered to be one of their highly promising applications. Polystyrene-based membranes containing sulfonylimide functional groups are the promising materials for these application due to the low crystallinity of polymer, high dissociation degree of functional groups, as well as thermal and electrochemical stability of obtained electrolytes. There are two different approaches for the synthesis of sulfonylimide based polymers: polymerization of functional monomer [1], and functionalization of the polymer [2]. The aim of this work was to synthesize membranes based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) containing functional sulfo R–SO3Li and sulfonylimide groups [R–SO2NSO2–X]Li, where X= –CF3, –CCl3, –CH3, –C6H5, –p-NO2C6H4 and –p-CF3C6H4, and investigation of Li+ conductivity of polyelectrolytes solvated by mixtures of ethylene carbonate/dimethylacetamide (EC-DMA) and ethylene carbonate/propylene carbonate (EC-PC). Membranes were synthesized according to the Scheme.To prepare plasticized polymer electrolytes, the synthesized dry SSEBS and SSEBS-X membranes in the Li+ form were transferred to a dry argon box (humidity level <10 ppm) and placed in the solutions containing equal volumes of EC-DMA or EC-PC for 24 h. Solvation degrees (n) of the membranes with EC-DMA and EC-PC mixtures were calculated as a ratio of the number of solvent molecules to the total number of membrane functional groups.The acid-base titration was used to determine full ion-exchange capacity (IEC) of the SSEBS membrane containing functional sulfo groups, as well as the residual amount of R–SO3 - functional groups in the SSEBS-NH2 membrane after the amination.The structure of SEBS, SSEBS and SSEBS-X were proven by ATR IR spectroscopy, using Nicolet iS5 IR in the frequency range 4000-500cm-1, and CHNS analysis, using EuroVector ЕА3000 equipment.Ionic conductivity of the obtained polymer electrolytes in the Li+ form plasticized by EC-PC and EC-DMA mixtures was investigated by impedance spectroscopy in the temperature range 0...+50 °С under the argon atmosphere, using the alternating current bridge Elins Z-1500J (frequency range from 2 MHz to 10 kHz) on symmetrical cells carbon/membrane/carbon. Resistance was determined from the intercept with the axis of active resistances in Nyquist plot.Optimal concentrations and equivalent excesses required for complete transformation of R–SO2NH2 groups into sulfonylimide functional groups [R–SO2NSO2–X]M by the Hinsberg reaction were found using phenylsulfonyl chloride. In particular, 1.5М is the minimal concentration of sulfonyl chloride in the mixture, and minimal excesses of sulfonyl chloride and triethylamine with respect to the amount of R–SO2NH2 groups are 10 and 3, respectively.IEC of the obtained membranes SSEBS-X are 1.54-1.68 mmol∙g-1. Solvation of the membranes with the EC-PC solvent mixture, which is the most common solvent in lithium-ion batteries, is not efficient for this purpose due to low solvation capability of organic carbonates and a high viscosity of the mixture. The solvation number of the membranes with this mixture does not exceed 1.7 solvent molecules per functional group, and Li+ conductivity is equal to or below 2∙10-3 mS∙cm-1 at 25°С. The use of amide-containing solvents leads to an increase of ionic conductivity of the sulfonylimide-based membranes due to specific interactions that determine their high solvation capability. In particular, when the EC-DMA mixture is used the solvation degree and ionic conductivity of the SSEBS-CF3 membranes at 25°С increase to 14.1 and 1 mS∙cm-1, respectively.The lowest solvation degree (1.9 solvent molecules per sulfonic group) and conductivity (0.1 mS∙cm-1 at 25°С) was found for the SSEBS membrane and the largest values were found for the SSEBS-CF3 polymer that contains trifluoromethanesulfonylimide functional groups (14.1 solvent molecules per 1 sulfonic group and 1.1 mS∙cm-1 at 25°С)According to acidity of [R–SO2NHSO2X] groups negative charge delocalization degree decreases along the following sequence X=CF3>CCl3>p-CF3Ph>Ph, whereas the sulfonic group should be placed at the end of the sequence having the lowest acidity. Such consistency of measured ionic conductivity and calculated acidity.This work was financially supported by the Russian Science Foundation (project No 17-79-30054) Bouchet, S. Maria, R. Meziane, A. Aboulaich, L. Lienafa, J.-P. Bonnet, T.N.T. Phan, D. Bertin, D. Gigmes, D. Devaux, R. Denoyel, M. Armand. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries // Nat. Mater. 2013. V. 12. P. 452-457. Rohan, Y. Sun, W. Cai, Y. Zhang, K. Pareek, G. Xu, H. Cheng. Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries // Solid State Ionics 2014. V. 268. P. 294-299. Figure 1

Performance enhancement of Na+ ion conducting porous gel polymer electrolyte using NaAlO2 active filler

In this paper, we report the enhanced electrochemical characteristic performance of porous gel polymer electrolyte, due to dispersion of sodium aluminate (NaAlO2) active fillers in it. The salt solution consisting of, sodium perchlorate (NaClO4) dissolved in binary mixture of ethylene carbonate and propylene carbonate (EC:PC) was entrapped in poly(vinylidinefluoride-co-hexafluoropropylene) (PVdF-HFP) polymer matrix to obtain the micro-porous sodium ion conducting gel polymer electrolyte films by using the phase inversion technique. Small loading of the active NaAlO2 fillers in gel polymer electrolyte results in significantly improved ionic conductivity (σmax=0.68 mS cm−1 at room temperature), Na+ ion transference number (tNa+∼ 0.45) and electrochemical stability window (ESW ∼ 4.1 V). Dielectric studies have been performed to explore the ion dynamics in the electrolyte system. The Na-S prototype battery delivers maximum discharge capacities of ∼ 210, 139 and 51 mA h g−1 at drain currents of 0.10, 0.25 and 0.50 mA cm-2, respectively. The optimized electrolyte composition with high liquid retention, conductivity and transport properties can be utilized for upcoming sodium batteries operating at room temperature.

Ion Transport in Solvated Sodium-Ion Conducting Gel Polymer Electrolytes

Single ion conducting gel polymer electrolytes (GPEs) are characterized as having a certain amount of ionic liquid or solvent incorporated into a single ion-conducting polymer matrix and may afford the advantages of high conductivity and low electrolyte polarization under battery operation. Single ion conducting polymers often suffer from low conductivity due to their reliance on polymer segmental motion to achieve sufficient ion mobility. However, by incorporating specific solvents into a single ion conducting matrix, mobility of the polymer can be enhanced while still maintaining the advantages of single ion conduction. Although many of the solvents used to swell GPEs are mixtures of flammable organic solvents (such as dimethyl carbonate), there are many potential non-reactive, low vapor pressure solvents that could effectively solvate alkali-ion based GPEs and plasticize the polymer matrix to enhance ion conductivity. Adipate-based solvents are a group of non-volatile plasticizers with low viscosities and low vapor pressures at room temperature derived from adipic acid. The ester and carbonate groups in these solvents may effectively solvate alkali ions such as Na+, leading to higher conductivity, while circumventing issues of flammability found in current alkali-ion conducting electrolytes. This study investigates the properties of sodium-ion conducting GPEs that have been swollen with varying adipate-based solvents and the subsequent dielectric response from the solvent addition. Dielectric relaxation spectroscopy was used to characterize the Na+ conductivity, static dielectric constant, ion-conducting content, and mobility of the membranes before and after the non-volatile solvent uptake. Understanding this relationship will pave the path towards safer, more efficient solid-state polymer electrolytes for battery applications.

Synthesis and molecular dynamic simulation of a novel single ion conducting gel polymer electrolyte for lithium-ion batteries

Single ion conductor has been realized as a new path to reduce polarization and improve electrochemical performance of the lithium ion batteries (LIBs). In this work, a novel single ion conductor gel polymer electrolyte (SIGPE) was designed via free radical polymerization, co-electrospinning and plasticizing process. The molecular structure information of the single ion polyanionic salt P(MPEGA-AMPSLi) of the SIGPE is carefully verified. The SIGPE shows high ionic conductivity of around 2.8 × 10−5 S/cm at 25 °C, high lithium ion transference number of 0.75, wide electrochemical window of 4.7 V as well as a stable cycle performance at 25 °C and 60 °C. The plasticizing mechanism of the gel polymer electrolyte has also been modeled and studied theoretically by molecular dynamics simulation. The results display a positive effect of the plasticizing in promoting the ionization of Li ions, increasing the diffusion coefficient of Li ions from 8.05 × 10−11 cm2/s to 1.37 × 10−9 cm2/s.

Infilling of highly ion-conducting gel polymer electrolytes into electrodes with high mass loading for high-performance energy storage

Full utilization of electrodes toward high-performance energy storage is challenging in cases where electrode/electrolyte interface is significant. From a practical perspective, this is particularly important in cases where a thick electrode or one with a high mass loading is needed. Here, we report an approach to increase the electrode performance by the infilling of a highly ion-conductive organic gel polymer electrolyte (EI-GPE, ionic conductivity ∼9.2mScm−1) into a multi-walled carbon nanotube (MWCNT) electrode with high mass loadings of up to 26mgcm−2 (or significant thicknesses of up to 443μm). Typical GPE (t-GPE) with a film-forming property but moderate ionic conductivity (1.2mScm−1) is then placed over the EI-GPE-filled electrode surface, resulted in flexible supercapacitor. Infilling of EI-GPE into MWCNT electrode provides a large-ion accessible interface that affords the increase in volumetric capacitance and energy density, about sixfold greater than that of the typical supercapacitors configured by sandwiching t-GPE as both electrolyte and the separator between a pair of electrodes. Importantly, this method enables scaling of the areal capacitance with electrode thickness (or mass loading of active material). A pouch type EI-SC provides stable performance after bending, suggesting it holds the promise of flexible energy storage.

Ion transport studies in PVA:NH4CH3COO gel polymer electrolytes

Ion conducting gel polymer electrolytes (GPEs) are being intensively studied for their potential applications in various electrochemical devices. The poly(vinyl alcohol)-based GPE films containing ammonium acetate (NH4CH3COO) salt have been studied for various concentrations of salt. The gel electrolyte films (GPEs) have been prepared using solution casting technique. Structural characterization carried out using X-ray diffraction reveals an increase in the amorphous nature of the samples on increasing salt concentration up to 70 wt%. The complexation of polymer and salt has been studied by Fourier-transform infrared analysis. Ionic conductivity of the GPEs has been found to increase with salt concentration and reaches an optimum for an intermediate concentration. The room temperature conductivity isotherm exhibits a maximum in conductivity of 2.64 × 10−4 Scm−1 for 65 wt% salt concentration. The temperature dependence of ionic conductivity exhibits a combination of Arrhenius and Vogel–Tamman–Fulcher behavior. Ion transport in the electrolyte system has been explored using dielectric response of the material and the observed variation in conductivity is suitably correlated to the change in charge carrier concentration and mobility of charge carriers.

Plastic crystal-incorporated magnesium ion conducting gel polymer electrolyte for battery application

Studies on a novel composition of magnesium ion conducting gel polymer electrolyte (GPE), comprising a solution of Mg-salt, magnesium trifluoromethanesulfonate (Mg-triflate or \(\hbox {Mg(Tf)}_{2})\) in a plastic crystal succinonitrile (SN), entrapped in a host polymer poly(vinylidenefluoride–hexafluoropropylene) (PVdF–HFP) was reported. Small amount of an ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf) was added to stabilize the GPE composition. The electrolyte possesses excellent dimensional integrity in the form of free-standing thick film, which offers the ionic conductivity of \(4 \times 10^{-3} \hbox { S } \hbox {cm}^{-1}\) at room temperature \({\sim }26{^{\circ }}\hbox {C}\). The electrochemical potential window of the electrolyte, observed from the linear sweep voltammetry, is determined to be \({\sim }4.1 \hbox { V}\). The magnesium ion conduction in the GPE film is confirmed from cyclic voltammetry, electrochemical impedance spectroscopy and dc polarization techniques. Different structural, thermal and electrochemical studies demonstrate the promising characteristics of the polymer film, suitable as electrolyte in rechargeable magnesium batteries. The potential of the GPE as electrolyte/separator was ascertained by fabricating a prototype magnesium battery of the configuration Mg:graphite composite \(\hbox {anode}/\hbox {GPE}/\hbox {MnO}_{2}\)-cathode. The specific discharge capacity of \(40 \hbox { mAh g}^{-1}\) (with respect to the \(\hbox {MnO}_{2}\) cathode material) was obtained at the first discharge. The cell shows charge–discharge performance for eight cycles with a substantial fading in capacity.

Enhanced Cycle Performance of Polyimide Cathode Using a Quasi-Solid-State Electrolyte

Benefiting from flexible molecular structures, low limitation of cationic radius, and environmental friendliness, organic materials are regarded as promising candidates for rechargeable batteries. However, the high-solubility in organic electrolytes is the most challenging issue. Most efforts have been focused on modification of the electrode materials. Herein, we employ a sodium ion conducting gel polymer electrolyte with interconnected pores to improve the cycle performance of a polyimide (PI) cathode. Compared to a commercial glass fiber separator, the gel polymer electrolyte only lets through Na ions but prevents the dissolved PI, and thereby avoids further dissolution. After utilization of the membrane, organic sodium ion batteries based on a PI cathode shows a highly enhanced cyclability (80% after 1000 cycles). Such a strategy can be potentially extended to many organic materials used in rechargeable batteries to ensure stability and safety.

Magnesium ion-conducting gel polymer electrolytes based on poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN): a comparative study between magnesium trifluoromethanesulfonate (MgTf2) and magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2)

In this paper, we report the effects of two different type of salts which are magnesium trifluoromethanesulfonate (MgTf2) and magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2) on ionic conductivity studies, transference number measurements, and electrochemical properties of gel polymer electrolyte (GPE) systems. Both systems used poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN) as the host polymer with the incorporation of plastic crystal succinonitrile (SN) and plasticizer ethylene carbonate (EC) in the ratio of (1:1). The system containing Mg(TFSI)2 exhibits higher in ionic conductivity of ~ (10−7–10−6) S cm−1 compared to the system containing MgTf2 of ~ (10−8–10−7) S cm−1. The conductivity temperature dependence studies of both GPE systems seem to obey the VTF relation. The ionic transference numbers were found to be > 0.9 for all GPEs while the highest cationic transference numbers obtained were 0.56 and 0.59 for MgTf2 system and Mg(TFSI)2 system, respectively. In linear sweep voltammetry (LSV) studies, wider electrochemical stability window was observed for the GPE containing Mg(TFSI)2 than that containing MgTf2 while cyclic voltammetry (CV) confirmed the conduction of Mg2+ ions in the GPEs. The structural and complex formations of the GPEs were confirmed by X-ray diffraction (XRD) analysis and both systems are shown to be amorphous in nature. The Mg/GPE/MgMn2O4 cells were assembled by using the most optimum GPE film from both systems and their charge-discharge performance was studied.

Dielectric and thermal features of zinc ion conducting gel polymer electrolytes (GPEs) containing PVC / PEMA blend and EMIMTFSI ionic liquid

A new series of gel polymer electrolytes (GPEs) based on an optimized composition of polymer blend-salt matrix [poly(vinyl chloride) (PVC) (30 wt%) / poly(ethyl methacrylate) (PEMA) (70 wt%): 30 wt% zinc triflate Zn(CF3SO3)2] containing different concentrations of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) ionic liquid has been prepared by simple solution casting technique. The prepared films of gel polymer membranes have been characterized utilizing complex impedance spectroscopy, differential scanning calorimetry (DSC), thermogravimetric (TG), and cyclic voltammetry (CV) analyses. The dielectric constant and ionic conductivity pursue similar trend with increasing EMIMTFSI concentration. The addition of ionic liquid in varied amounts into the optimized polymer blend-salt system effectively reduces the glass transition temperature (Tg) of the film as revealed from differential scanning calorimetry results. The origin of an improved thermal stability and feasible cyclic performance in respect of the best conducting sample of the resultant gel polymer electrolytes was also examined by utilizing thermogravimetric and cyclic voltammetry measurements.

Effect of organic solvent addition on electrochemical properties of ionic liquid based Na+ conducting gel electrolytes

A novel sodium ion conducting gel polymer electrolyte comprising room temperature ionic liquid, 1-ethyl 3-methyl imidazolium trifluoro-methane sulfonate (EMITf) incorporated with ethylene carbonate and propylene carbonate and its solution with sodium trifluoromethane sulfonate (NaTf) entrapped in poly(vinylidinefluoride-co-hexfluoropropylene) (PVdF-HFP) is prepared using solution cast technique. The gel electrolyte is obtained in the form of free-standing transparent film. The gel electrolyte offers electrical conductivity of ∼10−3Scm−1 at ∼30°C with good mechanical, thermal and electrochemical stability window. The electrical conductivity is measured as a function of temperature and found to be consistent with Vogel-Tamman-Fulcher (VTF) relationship in the temperature range from 30°C to 75°C.Sodium ion conduction in the gel electrolyte film is confirmed from cyclic voltammetry and transport number measurements. The value of the sodium ion transport number of the ionic liquid based gel electrolyte is ∼0.19. The sodium sulfur battery with the gel electrolytes delivers the first discharge capacity of 267mAhg−1 sulfur and then it decreases with repeated charge–discharge cycles.

Construction of interconnected micropores in poly(arylene ether) based single ion conducting blend polymer membranes via vapor-induced phase separation

We report the construction of interconnected micropores in a poly(arylene ether) based single ion conducting blend polymer electrolyte by tuning phase separation. Bis(4-fluorine benzene sulfonyl)imide is copolymerized with bis(4-hydroxy benzene sulfonyl)imide and bisphenol A separately to form two types of AB alternating block copolymers, i.e., lithiated poly(bis(benzene sulfonyl)imide)ether (LiPBIE) and lithiated poly(bisphenol A-alt-bis(4-fluorine benzene sulfonyl)imide)ether (LiPAFE). The former is immiscible with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and the latter is well entangled with the binder upon introducing the bisphenol group. The results reveal that the LiPBIE blend film exhibits an interconnected microporous structure while the LiPAFE blend film does not. Even if the ion exchange capacity (IEC) of the LiPAFE blend film is raised to the level of the LiPBIE blend film by reducing the proportion of PVDF-HFP, the film is porous only on the surface but remains dense in its bulk. The comparative experiments confirm that the disparity of polarity and solubility between the ionomers and the binder is largely responsible for the phase separation. The microporous single ion conducting gel polymer electrolyte offers an ionic conductivity of 0.52 mS cm−1 at 25°C and its membrane displays the capability of dendrite suppression. A battery incorporating the electrolyte film exhibits excellent rate performance and electrochemical stability.

Combined effect of alkaline cations and organic additives for iodide ion conducting gel polymer electrolytes to enhance efficiency in dye sensitized solar cells

Iodide ion conducting electrolytes are intensively studied as effectual electrolytes for dye-sensitized solar cells (DSSCs). However, the nature and concentration of the counter-ion (cation) in the electrolyte exert a profound influence on the performance of the thin film meso-porous TiO2 based DSSCs. A series of gel electrolytes containing the alkaline iodides LiI, NaI, KI, RbI and CsI and polyacrylonitrile (PAN) were fabricated together with the non-volatile plasticizers ethylene carbonate (EC) and propylene carbonate (PC). A similar series was fabricated with the inclusions of performance enhancers (additives) tetrapropylammonium iodide (Pr4NI), the ionic liquid 1-methyl-3-propyl imidazolium iodide (MPII) and 4-tert-butylpyridine (4TBP). The ionic conductivity of the electrolytes was studied in order to investigate its dependence on the nature of the alkaline cation in presence or absence of additives. The conductivities were higher for the electrolytes with the larger cations, namely K+, Rb+ and Cs+. A significant conductivity enhancement was observed in presence of the additives, and this effect was especially noticeable for samples with the smaller cations. The highest conductivity for electrolytes with additives, 3.96mScm−1 at 25°C, is exhibited by KI containing samples.

Poly-acrylonitrile-based gel-polymer electrolytes for sodium-ion batteries

Research and development activities on sodium-ion batteries are becoming prominent in the past few years. Compared to lithium-based batteries, the sodium-based batteries will be cheaper because of the abundancy of sodium raw materials in the earth’s crust and also in seawater. In the current study, we synthesized and characterized poly-acrylonitrile (PAN)-based gel-polymer electrolytes formed with NaClO4 and dissolved in ethylene carbonate (EC) and propylene carbonate (PC). By systematically varying the weight ratios of polymer, salt, and the solvents, we obtained an optimum room temperature ionic conductivity of 4.5 mS cm−1 for the composition 11PAN-12NaClO4-40EC-37PC (wt.%), which is reasonably good for practical applications. This value of conductivity is comparable to a few other Na+ ion conducting gel-polymer electrolyte systems studied in the recent past. Variation of ionic conductivity with inverse temperature showed Arrhenius behavior. Activation energies estimated for all the samples showed only a slight variation suggesting that a single activation process which depends on the EC/PC co-solvent governs the ionic mobility in these gel-polymer electrolytes. Thermo-gravimetric analysis (TGA) revealed that there is no noticeable weight loss of these electrolytes up to 100 °C and hence the electrolytes are thermally stable for operating temperatures up to 100 °C.

Ionic conductivity and battery characteristic studies of a new PAN-based Na+ ion conducting gel polymer electrolyte system

Sodium ion conducting gel polymer electrolytes based on polyacrylonitrile (PAN) with ethylene carbonate and dimethyl formamide as plasticizing solvents are prepared by the solution cast technique. These electrolyte films are free standing, transparent and dimensionally stable. Na+ ions are derived from NaI. The structural properties of pure and complex formations have been examined by X-ray diffraction, Fourier transform infrared spectroscopic studies and differential scanning calorimetric studies. The variation of the conductivity with salt concentration ranging from 10 to 40 wt% is studied. The sample containing 30 wt% of NaI exhibits the highest conductivity of 2.35 × 10−4 S cm−1 at room temperature (303 K) and 1 × 10−3 S cm−1 at 373 K. The conductivity–temperature dependence of polymer electrolyte films obeys Arrhenius behavior with activation energy in the range of 0.25–0.46 eV. The transport numbers both electronic (te) and ionic (ti) are evaluated using Wagner’s polarization technique. It is revealed that the conducting species are predominantly due to ions. The ionic transport number of highest conducting film is found to be 0.991. Solid-state battery with configuration Na/(PAN + NaI)/(I2 + C + electrolyte) is developed using the highest conducting gel polymer electrolyte system and the discharge characteristics of the cell are evaluated over the load of 100 KΩ.

A sodium ion conducting gel polymer electrolyte

A sodium ion conducting gel polymer electrolyte based on poly(vinylidene difluoride-co-hexafluoropropylene) porous membrane is reported, which is prepared through a simple phase separation process. It exhibits high safety, good mechanical properties and good electrochemical stability. The gel polymer electrolyte provides the sodium ionic conductivity of 0.60mScm−1 at ambient temperature, while the commercial separator (Celgard 2730) offers only 0.16mScm−1. The temperature dependence of the ionic conductivity from 25 to 75°C is consistent with an Arrhenius-behavior. The ionic transference number of sodium ion (tNa+) in the gel polymer electrolyte is 0.30, higher than that (0.17) in the commercial separator. This provides a new direction to improve the safety of sodium ion batteries.