Study on preparation and properties of gel polymer electrolytes based on comb-like copolymer matrix of poly(ethylene glycol) monomethylether grafted carboxylated butadiene-acrylonitrile rubber

A novel kind of gel polymer electrolytes (GPE) based on comb-like copolymers of poly(ethylene glycol) monomethylether (mPEG) grafted carboxylated butadiene-acrylonitrile rubber (XNBR) were prepared by introducing ionic liquids and LiClO₄ into polymer framework. FTIR spectra confirmed the grafting of mPEG to XNBR as side chains, and the content of grafted mPEG were calculated from the integral area of related peaks in ¹ H NMR spectra. Such grafted copolymer based GPE with ionic liquids as solvent showed higher ionic conductivity and reached a maximum ionic conductivity of 1.64?×?10^?3?S/cm (30?°C) in the experimental range, because the copolymers performed better polymer chain flexibility, which could be concluded from the decrease of T _g and crystallinity through DSC analysis. The generated GPE exhibited high electrochemical stability and the unit cell of LiFePO₄/GPE/Li could be cycled at room temperature.     

LiFePO4 batteries with enhanced lithium-ion-diffusion ability due to graphene addition

In this study, graphene was added to LiFePO₄ via a hydrothermal method to improve the lithium-ion-diffusion ability of LiFePO₄. The influence of graphene addition on LiFePO₄ was studied by X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, cycling test, and AC impedance analysis. The addition of graphene to LiFePO₄ resulted in the formation of a LiFePO₄–graphene composite; XRD observations revealed the composite to have a single phase with an olivine-type structure. Furthermore, LiFePO₄ particles in the composite were stacked on the graphene sheet surface, thereby enabling the composite to form an effective conducting network and facilitate the penetration of the surface of active materials by an electrolyte. The lithium-ion-diffusion ability of the LiFePO₄–graphene composite was greater than that of pure LiFePO₄. Of a number of materials studied [namely, pure LiFePO₄, LiFePO₄–graphene (1 %), LiFePO₄–graphene (5 %), and LiFePO₄–graphene (8 %)], LiFePO₄–graphene (5 %) delivered the best electrochemical performance with a lithium-ion-diffusion coefficient of 8.18 × 10^?12 cm² s^?1 and the highest specific discharge capacity of 149 mAh g^?1 at 0.17 C; in contrast, the corresponding values for pure LiFePO₄ were 3.01 × 10^?12 cm² s^?1 and 109 mAh g^?1, respectively. Further, LiFePO₄–graphene (5 %) showed a very high specific discharge capacity of 170 mAh g^?1 at 0.1 C, which is equal to the theoretical capacity of LiFePO₄.     

Rechargeable Li/LiFePO4 cells using N-methyl-N-butyl pyrrolidinium bis(trifluoromethane sulfonyl)imide-LiTFSI electrolyte incorporating polymer additives

We have incorporated polymer additives such as poly(ethylene glycol) dimethyl ether (PEGDME) and tetra(ethylene glycol) dimethyl ether (TEGDME) into N-methyl-N-butylpyrrolidinium bis(trifluoromethane sulfonyl)imide (PYR₁₄TFSI)-LiTFSI mixtures. The resulting PYR₁₄TFSI + LiTFSI + polymer additive ternary electrolyte exhibited relatively high ionic conductivity as well as remarkably low viscosity over a wide temperature range compared to the PYR₁₄TFSI + LiTFSI binary electrolytes. The charge/discharge cyclability of Li/LiFePO₄ cells containing the ternary electrolytes was investigated. We found that Li/PYR₁₄TFSI + LiTFSI + PEGDME (or TEGDME)/LiFePO₄ cells containing the two different polymer additives showed very similar discharge capacity behavior, with very stable cyclability at room temperature (RT). Li/PYR₁₄TFSI + LiTFSI + TEGDME/LiFePO₄ cells can deliver about 127 mAh/g of LiFePO₄ (74.7% of theoretical capacity) at 0.054 mA/cm² (0.2C rate) at RT and about 108 mAh/g of LiFePO₄ (63.4% of theoretical capacity) at 0.023 mA/cm² (0.1C rate) at −1 °C for the first discharge. The cell exhibited a capacity fading rate of approximately 0.09-0.15% per cycle over 50 cycles at RT. Consequently, the PYR₁₄TFSI + LiTFSI + polymer additive ternary mixture is a promising electrolyte for cells using lithium metal electrodes such as the Li/LiFePO₄ cell reported here. These cells showed the capability of operating over a significant temperature range (∼0-∼30 °C).     

Effective influences of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) ionic liquid on the ion transport properties of micro-porous zinc-ion conducting poly (vinyl chloride) /poly (ethyl methacrylate) blend-based polymer electrolytes

A series of new gel polymer electrolytes (GPEs) based on different concentrations of a hydrophobic ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) entrapped in an optimized typical 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] has been prepared using facile solution casting technique. The AC impedance analysis has revealed the occurrence of the maximum ionic conductivity of 1.10 × 10^?4 Scm^?1 at room temperature (301 K) exhibited by the PVC/PEMA- Zn(OTf)₂ system containing 80 wt% ionic liquid. The addition of EMIMTFSI into the optimized PVC/PEMA- Zn(OTf)₂ system in different weight percentages enhances the number of free zinc ions thereby leading to enrichment of ionic conductivity. The structural and complexation behaviour of the as prepared polymer gel electrolytes was substantiated by subjecting these electrolyte films to X-ray diffraction (XRD) and Attenuated total reflectance - Fourier transformed infrared (ATR-FTIR) investigations. The wider electrochemical stability window ~ 3.23 V and a reasonable cationic transference number (t_Zn ²⁺) of 0.63 have been attained for the polymer gel electrolyte film containing higher loading of (80 wt%) ionic liquid. The development of the amorphous phase of these gel polymer electrolyte membranes with increasing ionic liquid content was observed from scanning electron microscopic (SEM) analysis. The results of the current work divulge the assurance of developing GPEs based on ionic liquids for prospective application in zinc battery systems.     

A study on polymer blend electrolyte based on PVA/PVP with proton salt

Proton-conducting polymer blend electrolytes based on PVA–PVP–NH₄NO₃ were prepared for different compositions by solution cast technique. The prepared films are investigated by different techniques. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR and laser Raman studies confirm the complex formation between the polymer and salt. DSC measurements show decrease in T _g with increasing salt concentration. The ionic conductivity of the prepared polymer electrolyte was found by ac impedance spectroscopy analysis. The maximum ionic conductivity was found to be 1.41 × 10^?3 S cm^?1 at ambient temperature for the composition of 50PVA:50PVP:30 wt% NH₄NO₃ with low-activation energy 0.29 eV. The conductivity temperature plots are found to follow an Arrhenius nature. The dielectric behavior was analyzed using dielectric permittivity (ε*) and the relaxation frequency (τ) was calculated from the loss tangent spectra (tan δ). Using this maximum ionic conducting polymer blend electrolyte, the primary proton battery with configuration Zn + ZnSO₄·7H₂O/50PVA:50PVP:30 wt% NH₄NO₃/PbO₂ + V₂O₅ was fabricated and their discharge characteristics studied.     

Synthesis and Characterization of Novel Proton Conducting Polymer Blend Electrolytes

The proton conducting polymer blend electrolytes based on poly(vinyledine fluoride):poly(vinyl alcohol) (PVdF:PVA) polymer blend, doped with ammonium acetate (CH₃COONH₄) in different concentrations, have been prepared by a solution casting technique using dimethyl formamide (DMF) as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by X-ray diffraction analysis (XRD). The Fourier transform infrared spectroscopy (FTIR) analysis confirms the complex formation between the polymers and the salt. From the ac impedance spectroscopic analysis, the ionic conductivity of 5 MWt% CH₃COONH₄-doped PVdF:PVA polymer blend electrolyte has been found to be maximum of 1.30 × 10^?6 S/cm at room temperature.     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect on properties of PVDF-HFP based composite polymer electrolyte doped with nano-SiO2

Various kinds of nano-SiO₂ using different catalysts were obtained and characterized by scanning electron microscope (SEM) technique. The results showed that the nano-SiO₂ using NH₃·H₂O as catalyst presented the best morphology. Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based composite polymer electrolyte (CPE) membranes doped with different contents of nano-SiO₂ were prepared by phase inversion method. The as-prepared CPE membranes were immersed into 1.0 M LiPF₆-EC/DMC/EMC electrolytes for 0.5 h to be activated. The physicochemical and electrochemical properties of the CPEs were characterized by SEM, X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) techniques. The results indicate that the CPEs doped with 10 % nano-SiO₂ exhibit the best performance. SEM micrographs showed that the CPE membranes have uniform surface with abundant interconnected micro-pores, and the uptake ratio was up to 104.4 wt%. EIS and LSV analysis also showed that the ionic conductivity at room temperature and electrochemical stability window of the modified membrane can reach 3.372 mS cm^?1 and 4.7 V, respectively. The interfacial resistance R _i was 670 Ω cm^?2 in the first day, then increased to a stable value of about 850 Ω cm^?2 in 10 days storage at room temperature. The Li/As-fabricated CPEs/LiCoO₂ cell also showed good charge–discharge performance, which suggested that the prepared CPE membranes can be used as potential electrolytes for lithium ion batteries.     

A novel synthesis of Fe2P–LiFePO4 composites for Li-ion batteries

Fe₂P–LiFePO₄ composites were synthesized by a novel method consisting of co-precipitation modified with in situ polyacrylamide (PAM) formation. Simultaneous thermogravimetric-differential scanning calorimetric analysis indicated that the in situ PAM precursor exhibited a moderate continuous weight loss rather than a sharp mass loss process. The best Fe₂P–LiFePO₄ composite was obtained from 14 wt% in situ PAM precursor under a sintering temperature of 750 °C for 20 h, which delivered a discharge capacity of 131 mAh g^?1 at a rate of C/5 and 110 mAh g^?1 at 1 C and sustained 30 cycles with almost no capacity fading. The relatively good electrochemical performance originates mainly from the well-mixed gelation precursor and conductive Fe₂P phase with better electronic conductivity. This novel method verified that the electrochemical performance was improved compared to the conventional LiFePO₄ without in situ PAM. It can be anticipated that the same process should be readily extendable to other olivines, such as LiMnPO₄ and LiCoPO₄, and also to other phosphates.     

Characteristics of lithium iron phosphate mixed with nano-sized acetylene black for rechargeable lithium-ion batteries

Lithium iron phosphate mixed with nano-sized acetylene black (LiFePO₄-AB) was synthesized by a hydrothermal method and subsequent high-energy ball-milling process. Different contents of AB were added to improve the electronic conductivity of LiFePO₄. The structural and morphological performance of LiFePO₄-AB was investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope, and high-resolution transmission electron microscope. LiFePO₄-AB/Li batteries were fabricated in an argon-filled glove box, and their electrochemical performance was analyzed by cyclic voltammetry and charge/discharge tests. The XRD results demonstrate that LiFePO₄-AB has an olivine-type structure indexed to the orthorhombic Pnma space group. LiFePO₄-AB/Li battery with 10 wt% AB shows the best high-rate discharge properties with the discharge capacities of 116 mAh g⁻¹ at 1 C and 85 mAh g⁻¹ at 10 C at room temperature.     

Ionic interactions and transport characteristics of a new polymer electrolyte system containing poly(propylene glycol) 4000 complexed with AgCF3SO3

The effect of concentration of AgCF₃SO₃ salt on the behavior of ionic transport within the polymer electrolyte system containing the polymer host poly(propylene glycol) of molecular weight 4000 (PPG4000) has been investigated in terms of spectroscopic and electrochemical properties. It is evident that the presence of well-defined interactions between the ether oxygens and silver cations arising due to the complexation of the silver salt with the polymer matrix has enabled the chosen polymer electrolyte system to possess the maximum room temperature (298 K) electrical conductivity of 9.4 × 10^?5 S cm^?1 in the case of the typical composition having the ether oxygen-to-metal ratio (O:M) of 4:1 and the lowest activation energy E _a of 0.46 eV for Ag⁺ ionic conduction.     

Polymerized ionic liquids with guanidinium cations as host for gel polymer electrolytes in lithium metal batteries

Polymerized ionic liquids (PILs) having guanidinium cations with different counter‐anions, such as PF₆^? and N(CF₃SO₂)₂^? (TFSI^?), were synthesized by copolymerization of a guanidinium ionic liquid monomer with methyl acrylate followed by an anion exchange reaction. Furthermore, incorporating a guanidinium ionic liquid, LiTFSI salt and nano‐size SiO₂, a quaternary gel polymer electrolyte based on one of the PILs as the polymer host was prepared. The quaternary gel polymer electrolyte was chemically stable even at a higher temperature of 80 °C in contact with the lithium anode. In particular, the electrolyte exhibited high lithium ion conductivity, wide electrochemical stability window and good lithium stripping/plating performance. Li/LiFePO₄ batteries with the quaternary gel polymer electrolyte at 80 °C had capacities of 140 and 130 mA h g^?1 respectively at 0.1 and 0.2 C current rates. Copyright © 2011 Society of Chemical Industry     

Poly(methyl methacrylate) based nanocomposite gel polymer electrolytes with enhanced safety and performance

The study presents preparation of poly methyl methacrylate (PMMA) based nanocomposite gel polymer electrolytes consisting of, salt lithium perchlorate (LiClO₄), plasticizer PC/DEC and different proportions of SiO₂ nanofiber by solution casting process. The effect of the composition of the electrolytes on their ionic, mechanical and thermal characteristics was investigated. Morphology of the nanocomposite electrolyte films has been observed by scanning and transmission electron microscopes. Interactions among the constituents of the composite and structural changes of the base polymer were investigated by Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The maximum conductivity i.e. 10^?3 Scm^?1 at room temperature is obtained with the electrolyte composition of 0.6(PMMA)-0.15(PC + DEC)-0.1LiClO₄ (wt%) containing 10 wt% SiO₂ nanofiber and the temperature dependent conductivity data of the electrolyte follows Vogel-Tamman-Fulcher (VTF) behavior.     

Synthesis and characterization of Pt-doped LiFePO4/C composites using the sol–gel method as the cathode material in lithium-ion batteries

LiFePO₄/C and LiFe_0.96Pt_0.04PO₄/C nanocomposite cathode materials were synthesized using the sol–gel method in a nitrogen atmosphere. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Their electrochemical properties were investigated using galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The XRD results indicate that substituting iron with platinum does not destroy the structure of LiFePO₄, but expands the lattice parameters and enlarges the cell volume. The electrochemical results show that platinum doping improves the electrochemical performance of LiFePO₄/C particles owing to the expansion of the lattice structure, which provides more space for Li ion diffusion. The, larger lattice structure parameters of the LiFe_0.96Pt_0.04PO₄/C material result in a high discharge capacity of 166, 156, 142 and 140 mAh g^?1 at rates of 0.2, 1, 5, and 10 C, respectively, as compared to 164, 150, 120, and 105 mAh g^?1 for undoped LiFePO₄/C.     

Chemical lithiation route to size-controllable LiFePO4/C nanocomposite

Chemical lithiation of amorphous FePO₄ with LiI in acetonitrile is performed to form amorphous LiFePO₄. The amorphous FePO₄·2H₂O precursor is synthesized by co-precipitation method from equimolar aqueous solutions of FeSO₄·7H₂O and NH₄H₂PO₄, using H₂O₂ (hydrogen peroxide) as the oxidizing agent. The nanocrystalline LiFePO₄/C is obtained by annealing the amorphous LiFePO₄ and in situ carbon coating with sucrose in a reducing atmosphere. The particle size of FePO₄·2H₂O precursor decreases with increasing reaction temperature. The final LiFePO₄/C products completely maintain the shape and size of the precursor even after annealing at 700 °C for 2 h. The excellent electrochemical properties of these nanocrystalline LiFePO₄/C composites suggest that to decrease the particle size of LiFePO₄ is very effective in enhancing the rate capability and cycle performance. The specific discharge capacities of LiFePO₄/C obtained from the FePO₄·2H₂O precursor synthesized at 75 °C are 151.8 and 133.5 mAh g^?1 at 0.1 and 1 C rates, with a low capacity fading of about 0.075 % per cycle over 50 cycles at 0.5 C rate.     

Room-Temperature Solid-State Lithium Metal Batteries Using Metal Organic Framework Composited Comb-Like Methoxy Poly(ethylene glycol) Acrylate Solid Polymer Electrolytes

Solid polymer electrolyte with good thermal stability and flexibility is an excellent candidate for solid-state lithium metal batteries, while its low ionic conductivity caused by high crystallinity limits its application at ambient temperature. Here a metal organic framework (zeolitic imidazolate framework-8, ZIF-8) composited comb-like methoxy poly(ethylene glycol) acrylate polymer electrolyte (MCPE) with high ionic conductivity (9.96 × 10⁻⁵ S cm⁻¹ at 30 °C) is prepared by an in situ UV polymerization method. The as-prepared MCPE exhibits improved mechanical property due to the introduction of porous ZIF-8 nanofillers, which is beneficial to suppress the growth of lithium dendrites. Consequently, the LiFePO₄||MCPE||Li cells show a high capacity of 116 mAh g⁻¹ at 30 °C and 0.5 C, and maintain 89.4% of initial capacity after 150 cycles with the average Coulombic efficiency of 99.9%. These results demonstrate that the MCPE shows great potential in solid-state lithium metal batteries near room temperature.     

Structural,electrical and electrochemical properties of polyacrylonitrile-ammonium hexaflurophosphate polymer electrolyte system

Polyacrylonitrile (PAN) based polymer electrolyte membranes complexed with Ammonium hexafluorophosphate (NH₄PF₆) with different molar concentration are prepared by solution casting method. Increase in the amorphous nature by the addition of Ammonium salt and the formation of polymer-salt complex are confirmed by X ray diffraction studies and infrared spectroscopy respectively. The glass transition temperature is measured for all membranes and it showed a lowest value for the PAN complexed with 20 mol% of NH₄PF₆. Electrical properties are studied by AC impedance spectroscopy. An ionic conductivity of the order of 10^?3 Scm^?1 is obtained for the 80 PAN / 20 NH₄PF₆ polymer electrolyte. Conductivity, dielectric and modulus spectra from the impedance data are analysed to understand the ionic transport mechanism. Transference number measurement is done to study the ionic contribution to the charge transport. A proton battery with the configuration, Zn+ ZnSO₄. 7H₂O /80 PAN / 20 NH₄PF₆ / PbO₂ +V₂O₅ has been constructed and its discharge characteristics are studied.     

Dielectric and electrical characterization of (PEO–PMMA)–LiBF<Subscript>4</Subscript>–EC plasticized solid polymer electrolyte films

Plasticized solid polymer electrolytes (PSPEs) consisting of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50/50 wt%) based matrix with lithium tetrafluoroborate (LiBF₄) as dopant ionic salt (10 wt%) and varied concentrations (x = 0, 5, 10 and 15 wt%) of ethylene carbonate (EC) as plasticizer have been prepared. Classical solution-cast (SC) and the ultrasonic assisted followed by microwave irradiated (US–MW) solution-cast methods have been used for the preparation of (PEO–PMMA)–LiBF₄–x wt% EC films, and the same have been hot–pressed to get their smooth surfaces. Dielectric relaxation spectroscopy (DRS) and X–ray diffraction (XRD) techniques have been employed to characterize the dielectric and electrical dispersions and the structural properties of the PSPE films, respectively. It has been observed that the ionic conductivity of these semicrystalline ion-dipolar complexes is governed by their dielectric permittivity and polymers chain segmental dynamics. The increase in ionic conductivity values with the increase of plasticizer concentration in the PSPEs also varies with the films’ preparation methods. The US–MW method prepared PSPE film containing 15 wt% EC has a maximum ionic conductivity (1.86 × 10^?5 S cm^?1) at room temperature, whereas, the films having low concentrations of EC exhibit the conductivity of the order of 10^?6 S cm^?1.     

Investigations on Structural and Electrical Properties of KClO4 Complexed PVP Polymer Electrolyte Films

Potassium ion-conducting polymer electrolytes based on poly (vinyl pyrrolidone) (PVP) complexed with KClO₄ were prepared using a solution cast technique. These samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Differential Scanning Calorimetry (DSC), and impedance spectroscopy. The complexation of the salt with polymer was confirmed by FT-IR and XRD studies. The ionic conductivity was found to increase with increasing temperature and salt concentration. The highest ionic conductivity (0.91 × 10^?5 S/cm) and low activation energy (0.29 eV) was obtained for the polymer complexed with 15 wt% KClO₄ among all the compositions.     

Enhanced mechanical strength and conductivity of PVFM based membrane and its supporting polymer electrolytes

Polyvinyl formal based polymer electrolyte membranes are prepared via the optimized phase inversion method with poly(ethylene oxide) (PEO) blending. The physical properties of blend membranes and the electrochemical properties of corresponding gel polymer electrolytes (GPEs) are characterized by field emission scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, mechanical strength test, electrolyte uptake test, AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge test. The comparative study shows that the appearance of PEO obviously enhances the tensile strength of membranes and the ionic conductivity of corresponding GPEs. When the weight ratio of PEO is 30%, the tensile strength of membrane achieves 12.81 MPa, and its GPE shows high ionic conductivity of 2.20 × 10⁻³ S cm⁻¹, wide electrochemical stable window of 1.9–5.7 V (vs. Li/Li⁺), and good compatibility with LiFePO₄ electrode. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41839.