Impedance studies on plasticized PMMA-LiX [X: CF3SO3, N(CF3SO2)2−] polymer electrolytes

Plasticized polymer electrolytes composed of poly(methylmethacrylate) (PMMA) as the host, propylene carbonate (PC) or ethylene carbonate (EC) as a plasticizer and LiX (X: CF₃SO₃⁻ or N(CF₃SO₂)₂⁻) as a salt were prepared by the solution cast technique. Impedance spectroscopy was performed in the temperature range between 303 and 383 K. In this paper, we report the electrical properties of polymer electrolytes with different lithium salts and plasticizers. The polymer electrolytes investigated exhibited high ionic conductivity at room temperature in the range of 10^− 6 to 10^− 4 S cm^− 1. The temperature dependence studies showed that the samples were ionic conductors and seemed to obey the Vogel-Tamman-Fulcher (VTF) rule. FTIR spectroscopy studies confirmed the polymer-salt interaction.     

FTIR investigations on ion–ion interactions in liquid and gel polymeric electrolytes: LiCF3SO3-PC-PMMA

FTIR spectroscopy and ionic conductivity measurements have been employed to study the solvation and conduction mechanism of lithium ions in aprotic liquid electrolytes of LiCF₃SO₃-PC (lithium trifluromethanesulfonate-propylene carbonate) and gel electrolytes containing poly(methylmethacrylate) (PMMA) additionally. Cation solvation occurs via interactions between Li⁺ ions with the ring oxygens as well as the carbonyl oxygen of PC molecules over the entire salt concentration range under investigation (0.025–2 M) for both liquid and gel electrolytes. The ionic conductivity decline for concentrations 0.8 M LiCF₃SO₃-PC is attributed to the formation of ion pairs and/or triplets. Presence of (a) free CF₃SO₃ ^– ions in 0.025 and 0.05 molar LiCF₃SO₃-PC solutions, (b) the LiCF₃SO₃ structure with a monodentate coordinated lithium ion for concentrations 0.5 molar LiCF₃SO₃-PC systems and (c) ion triplets comprising two cations and an anion with a bidentate bridging structure in 2 M LiCF₃SO₃-PC electrolytes, has been established. Ionic conductivity performance concurs with our infrared results. Gel electrolytes containing upto 15 wt% of PMMA have been found to exhibit liquid like behavior but 2 M LiCF₃SO₃-PC systems that incorporate 25 wt% of polymer show a distinct Li⁺–O=C (of PMMA) interaction which is unambiguously determined from the remarkable changes observed for the _sC=O) and _s(SO₃)—the symmetric stretching vibrational modes.     

DSC and conductivity studies on PVA based proton conducting gel electrolytes

An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH₄SCN) solution and characterize them. DSC studies affirm the formation of gels along with the presence of partial complexes. The cole-cole plots exhibit maximum ionic conductivity (2.58 × 10⁻³ S cm⁻¹) for gel samples containing 6 wt% of PVA. The conductivity of gel electrolytes exhibit liquid like nature at low polymer concentrations while the behaviour is seen to be affected by the formation of PVA-NH₄SCN complexes upon increase in polymer content beyond 5 wt%. Temperature dependence of ionic conductivity exhibits VTF behaviour.     

Highly conductive non aqueous polymer gel electrolytes containing ammonium hexafluorophosphate (NH4PF6)

Non aqueous polymer gel electrolytes based on polyethylene oxide (PEO) and ammonium hexafluorophosphate (NH₄PF₆) show high conductivity above 10⁻² S/cm at 25°C. The addition of PEO to liquid electrolytes has been found to result in an increase in free ion concentration by dissociating ion aggregates present in these electrolytes at higher concentrations (≥0.4 M) of NH₄PF₆ alongwith an increase in viscosity. The free ion concentration and viscosity play a dominant role on the conductivity behaviour of these polymer gel electrolytes at low and high concentrations of PEO respectively. The presence of ion aggregates and their dissociation with the addition of PEO has also been checked by FTIR and the results are in agreement with the conductivity behaviour.     

Influence of 1-ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide plasticization on zinc-ion conducting PEO/PVdF blend gel polymer electrolyte

The influence in terms of plasticizer on zinc-ion conducting polymer blend electrolyte system, [PEO (90 wt%)/PVdF (10 wt%)]-15 wt% Zn (CF₃SO₃)₂] with various concentrations of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMIMTFSI) was investigated. The freshly-prepared thin films of [PEO (90 wt%)/PVdF (10 wt%)]-15 wt% Zn (CF₃SO₃)₂)?+?x wt% EMIMTFSI, where x?=?1, 3, 5, 7, and 10 wt%] were characterized by means of X-ray diffraction (XRD), Fourier transformed infrared (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and impedance analysis techniques. The room temperature XRD patterns tend to support the enhanced amorphous phase as a result of deducing the degree of crystallinity of the polymer blend–salt system by the addition of 7 wt% EMIMTFSI. The relevant SEM images of 7 wt% EMIMTFSI incorporated gel polymer electrolyte exhibit a minimised spheurilite structure when compared to that of the polymer blend–salt system. Unusually, the highest ionic conductivity realized in the case of the typical gel polymer electrolyte system, [PEO/PVdF-Zn (CF₃SO₃)₂ + 7 wt% EMIMTFSI] is found to be 1.63?×?10^?4 S cm^?1 at room temperature. The temperature dependence of conductivity has been examined based on the Vogel–Tammann–Fulcher (VTF) equation, thereby suggesting the segmental chain motion and free volume changes. The occurrence of ion dynamics and dielectric relaxation behaviour in the chosen system has been analysed in a detailed fashion at room temperature using frequency response impedance formalisms involving electric modulus and dielectric permittivity features.     

Morphology, thermal, electrical and electrochemical stability of nano aluminium-oxide-filled polyvinyl alcohol composite gel electrolyte

In the present work, an attempt has been made to develop nano aluminium oxide (Al₂O₃)-filled polyvinyl alcohol (PVA) composite gel electrolytes. Surface morphological studies, thermal behaviour, electrochemical stability and electrical characterization of these composite gel electrolytes have been performed. An increase in the concentration of Al₂O₃ in composite gel electrolytes increases the amorphous characteristics of pure PVA. Bulk conductivity of composite gel electrolytes increases by an order of magnitude on addition of a nano filler. Maximum conductivity of 5·81 × 10^?2 S/cm is observed for 6 wt% Al₂O₃-filled polymer gel composite electrolytes. Temperature dependence of electrical conductivity shows a combination of Arrhenius and Vogel-Tamman-Fulcher (VTF) nature. Maximum current stability during oxidation and reduction cycle is noticed for 6 wt% Al₂O₃-filled PVA composite electrolyte, viz. ±1·65 V.     

Impact of ethylene carbonate on ion transport characteristics of PVdF-AgCF3SO3 polymer electrolyte system

The ionic transport in thin film plasticized polymer electrolytes based on polyvinylidene fluoride (PVdF) as the polymer host, silver triflate (AgCF₃SO₃) as salt and ethylene carbonate (EC) as plasticizer prepared by solution casting technique has been reported. Addition of silver triflate has resulted in an increase in the room temperature (298 K) electrical conductivity of the polymer from 10⁻⁶ to 10⁻⁵ S cm⁻¹ whereas incorporation of EC as the plasticizer has further enhanced the conductivity value by an order of magnitude to 10⁻⁴ S cm⁻¹ owing to the possible decrease in crystallinity of the polymer matrix as revealed by the detailed temperature-dependent complex impedance, silver ionic transference number, Fourier transform infrared and X-ray diffraction measurements.     

A study incorporating nano-sized silica into PVC-blend-based polymer electrolytes for lithium batteries

Blends of poly(vinyl chloride)-poly(methyl methacrylate) (PVC/PMMA) and poly(vinyl chloride)-poly(ethylene oxide) (PVC/PEO) with lithium triflate (LiCF₃SO₃) as salt, ethylene carbonate (EC), and dibuthyl phthalate (DBP) as plasticizers and nano-sized silica (SiO₂) as filler, the first of its kind in such a study, were prepared using the solution-cast technique. This study affirmed that SiO₂ added PVC-PMMA and PVC-PEO-blend-based polymer electrolytes have the ability to retain their ionic conductivity and integrity even after 60 days of storage time at room temperature. The reduction of ionic conductivity values in PVC-PMMA-LiCF₃SO₃-DBP-EC:SiO₂-based and SiO₂-free membranes are 9 and 30%, respectively. When PVC-PEO-blend was used, the reduction of ionic conductivity values in PVC-PEO-LiCF₃SO₃-DBP-EC:SiO₂-based and SiO₂-free system was 16 and 40%, respectively, after 60 days of storage also at room temperature. The SiO₂-based complexes were also found to maintain their conductivity at higher temperatures of 60 °C and 90 °C with progressive storage times. This clearly shows that the SiO₂-induced stabilizing effect is maintained even at higher temperatures. Silica has brought the conductivity of polymer electrolytes into the useful realm for materials in lithium polymer battery applications.     

Study of enhanced dissociation of aliphatic dicarboxylic acids with PVdF addition in polymer gel electrolytes

The ionic conductivity of non-aqueous polymer gel electrolytes containing weak aliphatic dicarboxylic acids has been found to depend upon the dissociation constant of the acid used and conductivity of (1–2) × 10⁻³ S/cm has been obtained at 25^∘C. The addition of polyvinylidenefluoride (PVdF) to the solution electrolytes containing different dicarboxylic acids results in an increase in conductivity, which depends upon the concentration of polymer and acid present in these electrolytes. The enhancement of conductivity with PVdF addition has been explained to be due to the dissociation of undissociated acid present in the electrolytes which results in an increase in free H⁺ ion concentration and has been studied by pH measurements. The variation of viscosity with acid and polymer concentration and temperature has also been studied and viscosity increases exponentially at high PVdF concentrations and plays a dominant role at high PVdF concentrations.     

The effect of titanium dioxide nano-filler on the conductivity,morphology and thermal stability of poly(methyl methacrylate)—poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) based composite solid polymer electrolytes

The composite solid polymer electrolyte (CSPE) samples, comprising of poly(methylmethacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN)/ethylene carbonate (EC)/propylene carbonate (PC)/lithium trifluoromethanesulfonate (LiCF₃SO₃)/anatase-TiO₂ as nano-filler (0, 5, 6, 7, 8 and 9 wt% for samples T0, T1, T2, T3, T4 and T5 respectively) were prepared by solution casting technique. Fourier transform infrared (FT-IR) spectral studies indicate the interaction of PMMA and plasticizers (EC, PC) with Lithium ion and nano-filler TiO₂ in samples. From AC impedance studies ionic conductivity, dielectric constant increase with increase in the concentration of nano-filler TiO₂ up to 9 wt%. The sample T5 shows lowest activation energy (E_a) of 0.14 eV, very short relaxation time (τ) of 1.49?×?10^?7 s and exhibits maximum ionic conductivity of 1.05?×?10^?4 S cm^?1 at room temperature. The conductivity-temperature dependence studies showed that the conductivity of all samples depict Arrhenius behaviour suggesting ion-hopping mechanism. Dielectric studies reveal ion conducting nature of CSPE samples. Thermogravimetric analysis indicate the thermal stability of CSPE sample T5 up to 333 °C with maximum degradation at 388 °C. DSC studies reveal absence of glass transition temperature (T_g) of atactic component of PMMA in CSPE sample T5 indicating amorphous nature. X-ray diffraction patterns shows shift in the position of peaks confirming the complex formation of the PMMA-SAN-EC-PC-LiCF₃SO₃-TiO₂ system. SEM analysis indicates that the presence of lithium salt and filler TiO₂ on polymer host does not lead to heterogenous polymer blend thus retaining its amorphous nature.     

Li+‐Containing,Continuous Silica Nanofibers for High Li+ Conductivity in Composite Polymer Electrolyte

Solid‐state electrolytes have recently attracted significant attention toward safe and high‐energy lithium chemistries. In particular, polyethylene oxide (PEO)‐based composite polymer electrolytes (CPEs) have shown outstanding mechanical flexibility and manufacturing feasibility. However, their limited ionic conductivity, poor electrochemical stability, and insufficient mechanical strength are yet to be addressed. In this work, a novel CPE supported by Li⁺‐containing SiO₂ nanofibers is developed. The nanofibers are obtained via sol–gel electrospinning, during which lithium sulfate is in situ introduced into the nanofibers. The uniform doping of Li₂SO₄ in SiO₂ nanofibers increases the Li⁺ conductivity of SiO₂, generates mesopores on the surface of SiO₂ nanofibers, and improves the wettability between SiO₂ and PEO. As a result, the obtained SiO₂/Li₂SO₄/PEO CPE yields high Li⁺ conductivity (1.3 × 10^?4 S cm^?1 at 60 °C, ≈4.9 times the Li₂SO₄‐free CPE) and electrochemical stability. Furthermore, the all‐solid‐state LiFePO₄‐Li full cell demonstrates stable cycling with high capacities (over 80 mAh g^?1, 50 cycles at C/2 at 60 °C). The Li⁺‐containing mesoporous SiO₂ nanofibers show great potential as the filler for CPEs. Similar methods can be used to incorporate Li salts into other filler materials for CPEs.     

Preparation and characterization of plasticized polymer electrolytes based on the PVdF-HFP copolymer for lithium/sulfur battery

PVdF-TG-LiX polymer electrolytes comprised of polyvinylidene fluoride (PVdF)-hexafluoropropylene (HFP) copolymer, tetra(ethylene glycol) dimethyl ether as plasticizer, LiCF₃SO₃, LiBF₄ and LiPF₆ as lithium salt and acetone as solvent have been prepared by solvent casting of slurry that mixed PVdF-HFP copolymer with acetone and salt using a ball-milling technique, which was performed for 2 and 12 h with a ball-to-material ratio of 400:1, and their electrochemical and thermal properties were studied. The ball-milled PVdF-TG-LiX polymer electrolytes have higher ionic conductivity as well as lower glass transition temperature and melting points than the magnetically stirred one. The PVdF-TG-LiPF₆ polymer electrolytes prepared by ball-milling, for, 12 h, in particular, resulted in a maximum value in the ionic conductivity, which was 4.99×10^–4 S cm^–1 at room temperature. The ball-milled PVdF-TG-LiX polymer electrolytes were introduced into Li/S cells with sulfur as cathode and lithium as the anode. The first specific discharge capacities with discharge rate of 0.14 mA cm^–2 at room temperature were about 575 and 765 mA h g–cathode^–1 for magnetic stirring and 12 h ball milling.     

Plasticized alkaline solid polymer electrolyte system

Alkaline solid polymer electrolytes were prepared by utilizing poly(vinyl alcohol) (PVA), potassium hydroxide (KOH), α-Al₂O₃ and different amounts of propylene carbonate (PC). The addition of PC to the PVA:KOH:α-Al₂O₃:H₂O increased its conductivity by three orders of magnitude to the reading of ∼ 10^− 4 S cm^− 1. The plot for log σ − 1 / T showed a transformation from liquid-like conductivity to Arrhenius type. The dielectric constant (ε_r) of the samples increases with increasing PC concentrations and temperatures. Scanning electron microscopy also shows the effect of PC on the polymer electrolytes surface. Thermogravimetric studies show that the thermal stability of the polymer electrolytes decreases with the addition of PC.     

Effect of plasticizer and fumed silica on ionic conductivity behaviour of proton conducting polymer electrolytes containing HPF6

The effect of addition of propylene carbonate (PC) and nano-sized fumed silica on the ionic conductivity behaviour of proton conducting polymer electrolytes containing different concentrations of hexafluorophosphoric acid (HPF₆) in polyethylene oxide (PEO) has been studied. The addition of PC results in an increase in ionic conductivity, whereas the addition of nano-sized fumed silica improves mechanical strength of electrolytes along with a small increase in ionic conductivity. It was observed that the simultaneous addition of PC and fumed silica results in electrolytes with optimum value of ionic conductivity and other properties.     

]Electrical conductivity measurements on gel grown KDP crystals added with some ammonium compounds

Pure and impurity added [with NH₄CI, NH₄NO₃, NH4₄H₂PO₄, (NH₄)₂CO₃ and (NH₄)₂SO₄] KDP single crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 28 to 140°C by the conventional two-probe method. The present study shows that the conductivity in KDP crystals, for all the five dopants considered, increases with the increase in impurity concentration and temperature. Activation energies were also determined and reported.     

A Flexible Ionic Liquid Gelled PVA‐Li2SO4 Polymer Electrolyte for Semi‐Solid‐State Supercapacitors

A novel high‐performance flexible gel polymer electrolyte (FGPE) for supercapacitors is prepared by a freeze‐drying method. In the presence of 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid, Li₂SO₄ can easily be added into poly(vinyl alcohol) (PVA) aqueous solution over a large concentration range. The resultant FGPE demonstrates considerably high ionic conductivity (37 mS cm⁻¹) and a high fracture strain at 100% elongation at the optimal weight ratio of PVA:BMIMCl:Li₂SO₄ = 1:3:2.2. The supercapacitor fabricated with the resultant FGPE and activated carbon electrodes shows an electrode‐specific capacitance of 136 F g⁻¹ with a stable operating voltage of 1.5 V, a maximum energy density of 10.6 Wh kg⁻¹, and a power density of 3400 W kg⁻¹. Double supercapacitors in series can efficiently drive a light emitting diode (LED) bulb for over 5 min and the retention of the specific capacitance reaches 90% even after 3000 charge–discharge cycles. The ionic conductivity and charge–discharge behaviors of the resultant FGPE are not affected by bending up to 180°. The flexible supercapacitor device shows only a small capacitance loss of 18% after 1000 cycles of 135° bending.     

Synthesis and characterization of polyethylene oxide based nano composite electrolyte

Polyethylene oxide (PEO) – montmorillonite (MMT) composite electrolytes were synthesised by solution casting technique. The salt used for the study is Lithium perchlorate (LiClO₄). The morphology and percentage of crystallinity data were obtained through X-ray Diffraction and Differential Scanning Caloriemetry. The ionic conductivity of the polymer electrolytes was studied by impedance spectroscopy. The addition of MMT resulted in an increase in conductivity over the temperature range of 25–60^°C. The ionic conductivity of a composite polymer electrolyte containing 1.2 wt% MMT was 1 × 10^?5 S cm^?1 at 25^°C, which is at least one order of magnitude higher than that of the polymer electrolyte (4 × 10^?7S cm^?1). The increase in ionic conductivity is explained on the basis of crystallinity of the polymer electrolyte.     

Structure et conductivite electrique de verres appartenant au systeme Li2Si2O5 Li2SO4

The conductivity of vitreous electrolytes belonging to the Li₂Si₂O₅ Li₂SO₄ system has been measured over the temperature range 25–300 °C and for Li₂SO₄ concentrations varying from 0–28 mole percent. It has been found that the conductivity increases with the Li₂SO₄ fraction, attaining 10^?5 Ω^?1 cm^?1 at 130°C for the glass containing the highest proportion of sulphate. Raman spectroscopic studies indicate that the tetrahedral SO^2?₄ ions are in the glassy network, inserted or not into the silicate chains.     

Ionic conductivity of a gel polymer electrolyte based on Mg(ClO4)2 and polyacrylonitrile (PAN)

Magnesium ion containing gel polymer electrolytes based on polyacrylonitrile (PAN) have been synthesized and characterized using ac impedance measurements. The electrolyte composition having the highest room temperature conductivity was found by varying the ratios propylene carbonate/ethylene carbonate (PC/EC) and PAN/Mg(ClO₄)₂. The corresponding composition was 18 mol% PAN:64 mol% EC:14 mol% PC:4 mol% Mg(ClO₄)₂. The ac conductivity measurements were carried out from room temperature upto 70 °C with blocking (stainless steel) electrodes. The room temperature conductivity is 3.2×10⁻³ S cm⁻¹ and the activation energy is 0.24 eV over the temperature range used. The high conductivity and the low activation energy of the material could possibly be due to the liquid electrolyte, Mg(ClO₄)₂ in EC/PC trapped in a matrix of PAN, as suggested by previous workers. According to dc polarization measurements, the gel electrolyte appears to be predominantly an anionic conductor.     

Preparation of PVDF/PMMA blend microporous membranes for lithium ion batteries via thermally induced phase separation process

Thermally induced phase separation (TIPS) process was employed to prepare microporous poly (vinylidene fluoride)/poly (methyl methacrylate) (PVDF/PMMA) blend membranes using sulfolane as the diluent. Then they were immersed in liquid electrolyte to form polymer electrolytes. The effect of PMMA on the morphology and the crystallinity of blend membranes was studied. It was found that phase separation between PVDF and PMMA occurred when PMMA content was 40 wt.%. The addition of PMMA increased porosity and decreased the crystallinity, which in turn enhanced electrolyte uptake of blend membrane and the ionic conductivity of corresponding polymer electrolyte. The maximum ionic conductivity was 2.45 × 10^− 3Scm^− 1 at 20 °C.