Liquid-based Gel Polymer Electrolyte Research Articles

Solid-state electrical double layer capacitor using Li-salt incorporated ionic liquid based gel polymer electrolyte and gelled multi-walled carbon nanotubes electrodes

The present investigation is focused on the solid-state supercapacitors which are fabricated with ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMPTFSI) modified multiwalled carbon nanotube (MWCNT) electrodes and ionic liquid incorporated gel polymer electrolyte (ILGPE). Furthermore, the incorporation of the Li-salt lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) in ILGPE has been done and the effect of the Li-salt on the performance of supercapacitorsis investigated. On the addition of Li-salt, a wider electrochemical window of ∼ 3 V is found at room temperature. The impact of the Li-salt in the gel polymer electrolyte and comparative performance with the EDLCshave been studied byusing electrochemical impedance spectroscopy, cyclic voltammetric, and galvanostatic charge–discharge studies. It is found that bucky gelled MWCNT electrodes provide specific capacitance of ∼ 57 F/g with Li-salt incorporated ILGPE, which is higher as compared to ILGPE without Li-salt, showing the value of 51 F/g which as also reflect in CV profiles.

Performance of ionic liquid–based quasi‐solid‐state hybrid battery supercapacitor fabricated with porous carbon capacitive cathode and proton battery anode

AbstractThe present paper reports preparation, characterization, and application of proton‐conducting ionic liquid–based gel polymer electrolyte (ILGPE) obtained by immobilizing liquid electrolyte solution (0.3M NH4Tf in EMIMTf) to the polymer PVdF‐HFP. These ILGPE offer excellent ionic conductivity ~1.30 × 10−2 S/cm at room temperature and used as separator membrane in the hybrid BatCap. DSC study confirms glass transitions and melting temperatures (Tg's and Tm's) of PVdF‐HFP/EMIMTF/NH4Tf decrease with increasing content of liquid electrolyte to the host polymer matrix PVdF‐HFP which, in turn, is responsible for increasing flexibility of membranes. Ionic transport number measurements (tion ~0.99, ~0.27) reveal that ions are the principal charge carriers in the present electrolyte system. The linear sweep voltammetry analysis shows the electrochemical stability window (ESW) of ILGPE film “PVdF‐HFP/EMIMTf/NH4Tf” is ~3.35 V. Two different hybrid BatCap cells are prepared with activated carbon and MWCNTs as a capacitive electrode (cathode) and ZnSO4·7H2O battery anode. The performance of the BatCaps is estimated using cyclic voltammetry and galvanostatic charge‐discharge techniques. The discharge capacity was observed ~2.4 and 17.2 mAh/g for Cell#1 and Cell#2, respectively, at the current load of 0.5 mA/cm2. After the initial fading (~20%), BatCap cells show stable performance up to 100 cycles.

Performance of an ionic liquid based gel polymer electrolyte and its application in a redox capacitor

In the modern technology based society, attraction towards the redox capacitors is increasing rapidly as one of the best energy storage devices. Capacitors fabricated by using the Ionic liquid (IL) based Gel polymer electrolytes (GPEs) have been attracted tremendously as eco-friendly energy sources based on their unique features such as satisfactory specific capacitance, good cycle ability, and good stability. The present study reports about a redox capacitor fabricated with the IL, 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl) imide (1E3Mbis(TF)I) and sodium trifluoromethanesulfonate (CF 3 NaO 3 S - NaTF). Reported highest room temperature conductivity was 7.7 × 10 −4 S cm −1 with the composition of 1 Polyvinyl chloride (PVC):1 1E3MIbis(TF)I:2 NaTF. The conductivity mechanism of GPEs follows free volume theory. The redox capacitor with the configuration, polypyrrole (PPy):NaTF/1 PVC:1 1E3MIbis(TF)I:2 NaTF/PPy:NaTF showed a single electrode specific capacitance (C SC ) of 31.5 F g −1 based on Nyquist plot. Its relaxation time was 13.6 s and this confirms fairly fast charge storage process. Initial C SC of the redox capacitor was about 126.3 F g −1 for the potential window from −1.2 V to 1.2 V. Initial single electrode discharge capacitance (C sd ) observed by Galvanostatic charge discharge (GCD) test under a constant current of 240 μA was 24.1 F g −1 . It was gradually decreased to 9.57 F g −1 with cycling due to the formation of a passivation layer on the electrode and the degradation of electrolyte/electrode interface.

Development and optimization of ionic liquid based gel polymer electrolyte for all solid-state supercapacitor

Supercapacitors are promising candidates due to its high power density, long-life cycle and stability. However, supercapacitors which use liquid electrolyte face several problems such as safety and low specific energy. In this study, we optimized the electrochemical behavior of all-solid-state supercapacitor when we use various types of ionic liquids based gel polymer electrolyte. The electrochemical performances of the symmetric supercapacitor are evaluated by using cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), and galvanostatic charge/discharge tests(GCD). The highest specific capacitance is 160.6 F g−1 at scan rate of 5 mV s−1 with PVA/KI/EC/EMIBF4 based quasi-solid-state electrolyte and the supercapacitor exhibited high energy density of 180.67 Wh kg−1 at a power density of 375 W kg−1.

Performance of a Na Based Ionic Liquid Based Gel Polymer Electrolyte in a Redox Capacitor

In the modern technology based society, attraction towards the redox capacitors is increasing rapidly as one of the best energy storage devices. Capacitors fabricated by using the ionic liquid (IL) based gel polymer electrolytes (GPEs) have been attracted tremendously as eco-friendly energy sources based on their unique features such as satisfactory specific capacitance, good cycle ability, and good stability. The present study reports about a redox capacitor fabricated with the IL, 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl) imide (1E3Mbis(TF)I) and sodium trifluoromethanesulfonate (CF 3 NaO 3 S - NaTF). Reported highest room temperature conductivity was 7.7 x 10 -4 S cm -1 with the composition of 1 polyvinyl chloride (PVC): 1 1E3MIbis(TF)I: 2 NaTF. The conductivity mechanism of GPEs follows free volume theory. The redox capacitor with the configuration, polypyrrole (PPy): NaTF / 1 PVC: 1 1E3MIbis(TF)I: 2 NaTF / PPy: NaTF showed a single electrode specific capacitance (C SC ) of 31.5 F g -1 based on Nyquist plot. Its relaxation time was 13.6 s and this confirms fairly fast charge storage process. Initial C SC of the redox capacitor was about 126.3 F g -1 for the potential window from -1.2 V to 1.2 V. Initial single electrode discharge capacitance (C sd ) observed by Full words Galvanostatic charge discharge (GCD) test under a constant current of 240 μA was 24.1 F g -1 . It was gradually decreased to 9.57 F g -1 with cycling due to the formation of a passivation layer on the electrode and the degradation of electrolyte/electrode interface.

Physical and electrochemical chattels of phosphonium ionic liquid-based solid and gel-polymer electrolyte for lithium secondary batteries

In this work, a methodical study on the influence of ionic conductivity on polymer electrolyte with different weight percentages of ionic liquid and plasticizers had been investigated in detail. Solution casting method has been employed for preparing polymer electrolyte (PE) blend having poly(vinylidenefluoride-co-hexafluoropropylene) P(VdF-co-HFP) as polymer, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) amide [P14,6,6,6][Tf2N] as ionic liquid and ethylene carbonate (EC) as well as propylene carbonate (PC) in 1: 1 ratio as plasticizers. The polymer electrolyte has been found out stable up to 450 °C, as measured from Thermal gravimetric analysis (TGA). Impedance spectral analysis reveals that the ionic conductivity of SPEs is 3.209 × 10–6 S/cm at 303 K with 25 wt% of ionic liquid. The addition of plasticizers (EC + PC (60 wt%)) results in two orders of magnitude of higher ionic conductivity (3.40 × 10–4 S/cm at 303 K), than that of SPEs. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are performed to study the physico-chemical characteristics of polymer electrolytes. Electrochemical stability, potential window and discharge characteristics of the coin cell containing the electrolytes and LiFePO4 electrode were investigated using linear and cyclic voltammetry.

Zn/Natural graphite rechargeable cell with an ionic liquid based gel polymer electrolyte

There is an urgent need to fulfill the hunger for energy in an efficient and a safer way. In this context, non-Lithium based energy storage devices have received a noticeable interest. A prime attention has been given on electrolytes as many of the devices are composed with liquid electrolytes which have been later identified as having various problems. Gel polymer electrolytes (GPEs) are considered as viable substituents for liquid electrolytes because they exhibit liquid like conductivities while retaining good mechanical stabilities. To further improve the safety aspects of GPEs, nowadays many studies have been performed with ionic liquids (ILs) in place of solvents on GPEs. The present study was carried out to fabricate a Zn rechargeable cell with natural graphite (NG) cathode and an IL based GPE. The IL, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF) with the polymer poly(vinyl chloride) (PVC) and the salt zinc trifluoromethanesulfonate (Zn(CF3SO3)2 – ZnTF) were used in preparing the GPE. The electrochemical properties of the GPE were evaluated using electrochemical impedance spectroscopy (EIS) and DC polarization test. The maximum room temperature conductivity of the electrolyte was 3.06 × 10-4 S cm-1. Conductivity of the electrolyte was highly contributed by ions. The cell of the configuration, Zn / GPE / NG was characterized using cyclic voltammetry (CV) test. Initial specific charge was about 2.25 mA h g-1 and during 50 cycles, it had reduced down to 2.15 mA h g-1. Moreover, satisfactory stability was observed during CV test. Further studies are in progress to improve the cell performance.

Photo-Initiated Cross-Linking of a Methacrylate/Ionic Liquid Based Gel Polymer Electrolyte: Effect of the Curing Sequence on the Electrochemical Properties

In the present work, emphasis is given to the effect of the photocuring sequence on the electrochemical properties of a methacrylate/ionic liquid based gel polymer electrolyte (GPE). The reaction m...

An ionic liquid based gel polymer electrolyte to be employed in power generating applications

Ionic liquid (IL) based gel polymer electrolytes (GPEs) are being investigated extensively at present as substitutes for conventional GPEs based on a polymer, a salt and solvents. The main reason behind this is the drawbacks in usage of solvents. IL based GPEs have been employed for energy storage devices such as batteries and super capacitors due to their interesting mechanical, physical and electrochemical properties. This study focused on synthesis preparation and characterization of an IL based GPE consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP), zinc trifluoro metha -nesulfonate (Zn(CF3SO3)2 - ZnTF) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF). Thin film samples were prepared using solvent casting method. The optimized composition was found to be 1 PVdF-co-HFP: 1 1E3MITF: 3 ZnTF (by weight basis). This mechanically stable, thin film has the maximum room temperature conductivity of 7.42×10-3 S cm-1. Conductivity variation with temperature follows Vogel - Tamman - Fulcher (VTF) behavior confirming the relation of conductivity mechanism with the free volume theory. The IL based GPE is a purely an ionic conductor having a considerable anionic contribution. It shows stability up to 2.5 V which is very much convenient from a practical point of view. Oxidation and reduction of Zn takes place at the potentials of 0.5 V and –0.5 V, respectively. In addition, Zn platting and stripping occurs only on the Zn electrodes but not on the stainless steel (SS) electrodes. Impedance measurements taken for the GPE continuously for a long period of time exhibited a satisfactory stability with Zn electrodes.

Performance of EMIMFSI ionic liquid based gel polymer electrolyte in rechargeable lithium metal batteries

Flexible gel polymer electrolytes based on polymer polyethylene oxide, salt lithium bis(fluorosulfonyl)imide and ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide are synthesized. Prepared samples show high thermal stability, high ionic conductivity at room temperature and an electrochemical stability window of ∼3.51V vs. Li/Li+. Lithium deposition-striping voltage profiles show the formation of a stable solid electrolyte interface. A Li/GPE/LiFePO4 cell was assembled by low cost thermal lamination technique. This cell can deliver 143mAhg−1 capacity at room temperature at C/20 rate with good discharge efficiency. Use of micro grid mesh type Al current collector in cathode exhibits significant improvement in capacity retention.

Electrochemical characterization of ionic liquid based gel polymer electrolyte for lithium battery application

High molecular weight polymer poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI), and salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based free-standing and conducting ionic liquid-based gel polymer electrolytes (ILGPE) have been prepared by solution cast method. Thermal, electrical, and electrochemical properties of 80 wt% IL containing gel polymer electrolyte (GPE) are investigated by thermogravimetric (TGA), impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). The 80 wt% IL containing GPE shows good thermal stability (~ 200 °C), ionic conductivity (6.42 × 10−4 S cm−1), lithium ion conductivity (1.40 × 10−4 S cm−1 at 30 °C), and wide electrochemical stability window (~ 4.10 V versus Li/Li+ at 30 °C). Furthermore, the surface of LiFePO4 cathode material was modified by graphene oxide, with smooth and uniform coating layer, as confirmed by scanning electron microscopy (SEM), and with element content, as confirmed by energy dispersive X-ray (EDX) spectrum. The graphene oxide-coated LiFePO4 cathode shows improved electrochemical performance with a good charge-discharge capacity and cyclic stability up to 50 cycles at 1C rate, as compared with the without coated LiFePO4. At 30 °C, the discharge capacity reaches a maximum value of 104.50 and 95.0 mAh g−1 for graphene oxide-coated LiFePO4 and without coated LiFePO4 at 1C rate respectively. These results indicated improved electrochemical performance of pristine LiFePO4 cathode after coating with graphene oxide.

Improved electrochemical performance of EMIMFSI ionic liquid based gel polymer electrolyte with temperature for rechargeable lithium battery

Free-standing, flexible ionic liquid based gel polymer electrolyte (ILGPE) membranes containing polymer PVdF-HFP, imidazolium-based ionic liquid EMIMFSI with lithium salt LiTFSI are synthesized and characterized by various techniques. Thermal, electrochemical and electrical properties of prepared ILGPE membranes are investigated by thermogravimetric analysis, linear sweep voltammetry, cyclic voltammetry and impedance spectroscopy techniques. Prepared membranes are found to be thermally stable upto 200 °C. The ionic conductivity is found to be ∼3.8 × 10−4 S cm−1 at 25 °C and ∼6.0 × 10−4 S cm−1 at 50 °C for 40 wt% IL containing GPE. Lithium transference number and lithium ion conductivity of 40 wt% IL containing GPE shows the maximum value ∼0.4 and ∼1.5 × 10−4 S cm−1 respectively with electrochemical window ∼4.7 V versus Li/Li+ at 25 °C. The 40 wt% IL containing GPE is used for battery application because of its better compatibility with lithium electrode compared to other prepared ILGPEs. The discharge capacity attains a maximum value ∼141.2 mAh g−1 and ∼160.3 mAh g−1 at 25 °C and 50 °C respectively at 0.1C. About ∼99% Coulombic efficiency is obtained upto 100th cycles at 50 °C. These results indicate that the Li/40 wt% IL containing GPE/LiFePO4 cell shows high Coulombic efficiency, good charge-discharge capacity and cyclic stability upto 100th cycles.

Effect of Dispersoid on Sulfonium Ionic Liquid Based Gel Polymer Electrolyte for Lithium Secondary Battery.

The present study emphases on the effect of toting of TiO2 filler on the electrochemical enactment of polymer electrolyte containing PVdF-co-HFP(30) + SEt3TFSI(10) + EC/PC(60) + TiO2(x) wt% (Poly (vinylidene fluoride-co-hexafluoropropylene + Triethylsulfoniumbis(trifluoromethylsulfonyl)imide + Ethylene carbonate/Propylene carbonate (1:1 ratio) + Titanium dioxide) for lithium battery applications. Composite electrolytes with different weight percentages of TiO2 were prepared and characterized by different surface analytical, thermal and electrochemical techniques. With gradual increase of the amount of TiO2 upto 6 wt%, broadening of the prominent peak has been noted, suggesting a decrease in the degree of crystallinity upon the addition of TiO2, as revealed by X-ray diffraction (XRD). Raman and FT-IR studies confirm the presence of various functional groups, present in the matrix. The electrolyte with TiO2 (6 wt%) has maximum stability of 460 °C, as confirmed by thermal analysis. Conductivity of the composite polymer electrolytes increases upto 6 wt% of TiO2 (3.42 × 10-3 S/cm at 303 K) and further addition, causes a dip down in conductivity, indicating an improvement in the ionic conductivity and thermal stability with the incorporation of TiO2 filler. Surface morphologic images show the presence of surface and cavity in the polymer matrix, filled with the filler uniformly. Voltammetric studies confirm the electrochemical stability of films upto 4.62 V. Coin cell containing Li anode and LiFePO4 cathode along with polymer electrolyte/6 wt% TiO2 filler, delivers a first discharge capacity of 145 mAh/g with the working voltage of 3.4 V.

Role of Filler Additives in Ionic Liquid Based Gel Polymer Electrolyte for Room Temperature Lithium Battery Application

Lithium ion batteries (LIBs) have been extensively studied as energy sources for devices ranging from portable electronics to electric vehicles (EVs). LIBs safety remains one of their biggest concerns due to use of flammable organic liquid as electrolytes1. In recent years, the emergence of gel polymer electrolytes (GPE) based on ionic liquid solvent opened up an avenue for safer solid-state battery technology due to the nonflammability nature of the liquid. These type of GPEs consist of a liquid electrolyte solvent with lithium salt and a polymer2. Addition of fillers in GPEs have been shown to improve both ionic conductivity and mechanical properties of the composite electrolyte3. In this work, we are reporting a gel polymer electrolyte (GPE) which was synthesized by blending of a polymerized ionic liquid (PIL) based on pyrrolidinium cation, an imidazolium cation based ionic liquid and lithium salt. Later on, the effect of addition of certain percentages of inorganic silica fillers in GPE were observed by performing both electrochemical and thermal analysis of the polymer electrolyte and their applicability in Li batteries. The prepared GPEs and the composite GPEs (CGPE) were free standing and mechanically stable. Electrochemical Impedance Spectroscopy (EIS) was performed to measure and compare the room temperature ionic conductivity of the GPEs and CGPEs. Chronoamperometry tests were also performed to observe the lithium ion transference number of both type of electrolytes. Almost a two-fold increase in ionic conductivity and ~10% increase in lithium ion transference number was observed for CGPE compared to GPE. This may be the cause of improved ion conduction pathways for lithium ions due to the addition of inorganic silica fillers. Thermogravimetric analysis was performed to observe the thermal stability of the electrolytes and it has been observed that both the electrolytes were thermally stable upto 390oC. The electrolytes also possess high electrochemical stability window (~ 5V vs Li/Li+) which indicates their good affinity of the PIL, Ionic Liquid, Lithium salt and the fillers. The chemical stability of the electrolytes against lithium anode were evaluated and compared with the ionic liquid electrolyte (ILE) by performing EIS of Li/GPE or CGPE or ILE/Li symmetric cells at different storage time under open circuit condition at room temperature. The growth rate of interfacial resistances in terms of storage time is significantly lower for both the GPE and CGPE compared to ILE system. To observe the electrochemical stability of the electrolytes, galvanostatic cycling tests were performed on Li/Li symmetric cells at high current densities. It has been observed that both the electrolytes have lower and stable overpotential compared to ILE which is indicative of uniform lithium deposition on both GPE and CGPE. The electrochemical results obtained in this study, indicate that the CGPE are expected to perform as solid-state composite electrolyte in new generation lithium batteries.

Impedance spectroscopy, DC polarization, XRD and SEM studies on an ionic liquid based gel polymer electrolyte to be used for dye sensitized solar cells

Dye sensitized solar cells (DSSCs) receive lots of attention as a suitable device in converting sunlight to electricity. A great deal of work has been carried out to develop gel polymer electrolytes (GPEs) and one strategy is introducing ionic liquids (ILs) to eliminate some adverse effects and also to improve ionic conductivity. The composition 15% polyvinylidene fluoride (PVdF): 37% ethylene carbonate (EC): 37% propylene carbonate (PC): 11% 1 butyl 3 methyl immidazolium iodide (IB 3M II) showed the highest conductivity. It was a good anionic conductor. IL has caused reduction of crystallinity which assists to enhance conductivity.

Characterization and application of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ionic liquid–based gel polymer electrolyte prepared in situ by photopolymerization method in lithium ion batteries

Ionic liquid gel polymer electrolyte (IL-GPE) was prepared in situ by photocuring of a mixture containing N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (IL), lithium bis(trifluoromethane-sulphonyl)imide and ethoxylated bisphenol A diacrylate. The obtained IL-GPE was characterized by differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), cyclic and linear sweep voltammetry (CV and LSV) and galvanostatic charging/discharging. Ionic conductivity of the IL-GPE reached 0.64·10−4 S cm−1 at 25°C and increased with a rise in temperature to 4.8 10−3 S cm−1 at 95°C. Electrochemical stability of the IL-GPE is ca. 4.8V vs. Li/Li+. The assembled cell consisting of the Li/IL-GPE/LiFePO4 exhibited stable cycle properties and high capacity above 162 mAh g−1 after 50 cycles (96% of theoretical capacity, which for LiFePO4 is 170 mAh g−1) at the C/20 rate and 25°C. The results obtained indicate that the new IL-GPE is a promising candidate as an electrolyte for flexible lithium ion batteries.

Ionic Liquid Based Gel Polymer Electrolyte for Lithium-Oxygen Battery

not Available.

All-solid-state supercapacitors with poly(3,4-ethylenedioxythiophene)-coated carbon fiber paper electrodes and ionic liquid gel polymer electrolyte

All-solid-state thin supercapacitors have been fabricated using current pulse polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) over carbon fiber paper and ionic liquid based gel polymer electrolyte. The PEDOT-coated carbon paper electrodes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) which confirm the porous morphology of PEDOT at the nanoscale and a high degree of ClO4− dopant ion conjugation. The performance characteristics of the supercapacitor cells have been evaluated by ac impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge techniques. The PEDOT electrode shows specific capacitance of ∼154.5 F g−1, which correspond to the cell area-normalized capacitance of 85 mF cm−2. The maximum specific energy and specific power of the solid-state supercapacitor cell, calculated from charge-discharge characteristics, are 6.5 Wh kg−1 and 11.3 kW kg−1, respectively. The solid-state supercapacitor shows good cycle durability and time stability. The thin, lightweight, gel electrolyte based supercapacitor shows considerable potential for low-cost, high-performance energy storage applications.

Solid-state supercapacitors with ionic liquid based gel polymer electrolyte: Effect of lithium salt addition

Performance characteristics of the solid-state supercapacitors fabricated with ionic liquid (IL) incorporated gel polymer electrolyte and acid treated multiwalled carbon nanotube (MWCNT) electrodes have been studied. The effect of Li-salt (LiPF6) addition in the IL (1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate, EMImFAP) based gel electrolyte on the performance of supercapacitors has been specifically investigated. The LiPF6/IL/poly(vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP) gel electrolyte film possesses excellent electrochemical window of 4 V (from −2.0 to 2.0 V), high ionic conductivity ∼2.6 × 10−3 S cm−1 at 20 °C and high enough thermal stability. The comparative performance of supercapacitors employing electrolytes with and without lithium salt has been evaluated by impedance spectroscopy and cyclic voltammetric studies. The acid-treated MWCNT electrodes show specific capacitance of ∼127 F g−1 with IL/LiPF6 containing gel polymer electrolyte as compared to that with the gel polymer electrolyte without Li-salt, showing the value of ∼76 F g−1. The long cycling stability of the solid state supercapacitor based on the Li-salt containing gel polymer electrolyte confirms the electrochemical stability of the electrolyte.

Anti-thermal shrinkage nanoparticles/polymer and ionic liquid based gel polymer electrolyte for lithium ion battery

A new gel polymer electrolyte (GPE) system for lithium ion battery was developed by using anti-thermal shrinkagable nanoparticles/polymer incorporating with ionic liquid. Polyethylene-supported SiO2/poly(methyl methacrylate–acrylonitrile–vinyl acetate) (P(MMA–AN–VAc)) and Al2O3/P(MMA–AN–VAc) separators were prepared and the corresponding GPEs, SiO2/P(MMA–AN–VAc)+LiTFSI+PYR14TFSI/VC and Al2O3/P(MMA–AN–VAc)+LiTFSI+PYR14TFSI/VC, were obtained by immersing the separators in an ionic liquid electrolyte of 0.5molkg−1 LiTFSI in PYR14TFSI/VC. The structure and performance of the separators and corresponding GPEs were characterized by thermogravimetric analysis (TGA), air permeability, scanning electron spectroscopy (SEM), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), cyclic voltammetry (CV) and charge–discharge test. It is found that the nanoparticles/polymer separators have good dimensional stability and the corresponding GPEs have good ionic conductivity and excellent compatibility with the electrodes of lithium ion battery. SiO2/P(MMA–AN–VAc) and Al2O3/P(MMA–AN–VAc) separators are stable up to 310°C and have a Gurley value of 8s. SiO2/P(MMA–AN–VAc) based GPE has an ionic conductivity of 1.2×10−3Scm−1 at room temperature and an oxidative decomposition potential of 5.3V (vs. Li/Li+). The interfacial resistance between anode lithium and GPE is changed from 47Ωcm2 on the first day to 118Ωcm2 after the 25 days. The battery Li/GPE/LiFePO4 shows good rate and cyclic performance.