Gel-type Polymer Electrolytes Research Articles

Functional Sulfate Additive-Derived Interfacial Layer for Enhanced Electrochemical Stability of PEO-Based Polymer Electrolytes.

Solid-state electrolyte batteries have attracted significant interest as promising next-generation batteries due to their achievable high energy densities and nonflammability. In particular, curable polymer network gel electrolytes exhibit superior ion conductivity and interfacial adhesion with electrodes compared to oxide or sulfide solid electrolytes, bringing them closer to commercialization. However, the limited electrochemical stability of matrix polymers, particularly those based on poly (ethylene oxide) (PEO), presents challenges in achieving stable electrochemical performance in high-voltage lithium metal batteries. Here, these studies report a sulfate additive-incorporated thermally crosslinked gel-type polymer electrolyte (SA-TGPE) composed of a PEO-based polymer matrix and a functional sulfate additive, 1,3-propanediolcyclic sulfate (PCS), which forms stable interfacial layers on electrodes. The electrode-electrolyte interface modified by the PCS enhances the electrochemical stability of the polymer electrolyte, effectively alleviating decomposition of the PEO-based polymer matrix on the cathode. Moreover, it also mitigates side reactions of the Ni-rich NCM cathode and dendrites of lithium metal anode. These studies provide a novel perspective by utilizing interfacial modification through electrolyte additives to resolve the electrochemical instability of PEO-based polymer electrolytes in high-voltage lithium metal batteries.

PVP/PEG polymer blend based electrolytes for quasi-solid-state dye-sensitized solar cells operating at low temperature

We investigated the performance of quasi-solid-state dye-sensitized solar cells (qs-DSSCs) employing Polyvinylpyrrolidone/Polyethylene glycol (PVP/PEG) blends over a wide temperature range. The photovoltaic performance of qs-DSSCs with conventional polymer electrolytes is very poor at low temperatures, mostly because of the significantly reduced ionic conductivity of the electrolyte. The PVP/PEG blend with a composition ratio of 20/80 exhibited low glass-transition temperature and high ionic conductivity, resulting in a power conversion efficiency (PCE) of 2.91% at a low temperature (−133 °C). This is 2.67 times higher than that of the device PCE (1.09%), with the most efficient and conventional gel-type polymer electrolyte. At ambient temperature, the qs-DSSC with PVP/PEG realized a device PCE of 6.13%, which is comparable to that of cells with conventional liquid electrolyte employing 3-methoxypropionitrile (6.36%) or a polymer electrolyte based on poly (vinylidene fluoride-co-hexafluoropropylene) (6.05%). In addition, the qs-DSSC with PVP/PEG exhibited excellent long-term stability during aging test, retaining approximately 88% of its initial PCE after 1000 h of light irradiation. The electrolyte developed in this study is not constrained by temperature factors and can be applied to solar cells that are viable for practical outdoor use (polar regions and space) with increased power output.

Preparation and Characterization of Polymer based Electrolytes for Dye-sensitized Solar Cell Application

A gel-type polymer electrolyte (GPE) composite based on polyacrylonitrile (PAN) conducting polymer plasticized with ethylene carbonate (EC) and propylene carbonate (PC) doped by different compositions of tetrapentylammonium iodide (TPeAI) salt has been prepared and investigated. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) techniques have been used to characterize the prepared GPEs. From the EIS study, it has been observed that 30 wt % TPeAIcontaining GPE has the lowest bulk impedance, Rb (32 ohm) and highest room-temperature ionic conductivity (2.4910-3 S cm-1). The conductivity vs temperature diagram in the range of studied temperature studied follows the Arrhenius rule. The values of activation energies, (Ea) are observed to decrease with the increase of the percentage of TPeAI percentage with the lowest values (8.50105 J/mol) for 30% TPeAI containing GPE. From LSV graphs for the GPE systems, various parameters such as the limiting current density (Jlim), the apparent diffusion coefficient of triiodide ion () and exchange current density (J0) have been estimated. The most conducting GPE material shows the highest values of Jlim (3.95 mA.cm-2), (7.86×10-8cm2 s-1) and J0 (0.46 mA.cm-2). The GPEs will be suitable for application in Dye-sensitized Solar Cell (DSSC).

A non-nucleophilic gel polymer magnesium electrolyte compatible with sulfur cathode

Magnesium/sulfur battery (Mg/S) has recently received wide attention due to its high theoretical energy density (3,260 Wh/L) and low cost. To further improve its safety and flexibility, developing a polymer electrolyte that can be compatible with both electrophilic S and Mg is critical. Here, we report a magnesium chloride-(fluorinated tetraethylene glycolic)borate (MgCl-FTGB) based non-nucleophilic, gel-type polymer electrolyte for Mg/S battery via a facile synthetic method through commercially available reagents. This electrolyte coupled with glass fiber allows reversible Mg deposition/dissolution (100% coulombic efficiency) with low polarization (500 µA/cm2, 300/300 mV), and shows a wide electrochemical window of 4.8 V (vs. Mg/Mg2+). Mg/S battery assembled with this electrolyte can cycle over 50 times with a high specific discharge capacity retention of over 1,100 mAh/g.

Highly dispersible graphene oxide nanoflakes in pseudo-gel-polymer porous separators for boosting ion transportation

Gel-type polymer electrolytes have received considerable attention due to the battery explosion issue associated with volatile liquid-electrolyte-based lithium ion batteries (LIBs). However, the high ionic conductivity of gel-type polymer electrolytes originates from polymer swelling by the liquid electrolyte, and these materials inevitably have poor mechanical strength during device deformation. Here, we report structural gel-type polymer separators with highly porous and uniform morphology arising from the phase inversion of PVdF-HFP polymers with highly dispersible nanoscale graphene oxide nanoflake (GON). Via simple γ-ray irradiation of conventional graphene oxide solution, large 2D particles were cut into small 2D particles with a narrow size distribution, which in turn resulted in a dramatic change in solution transparency and particle dispersity. γ-ray-irradiated graphene oxide nanoflakes (γ-GON) with high dispersity are located inside the porous PVdF-HFP skeleton, inducing additional micron-sized pores of ∼8 μm in the composite membranes. The modified porous film showed both gel-polymer electrolyte-like (uptake of 1.7 times more liquid electrolyte than conventional polyethylene separator) and polymer separator-like behavior (maintenance of original porous structure after soaked with liquid electrolyte). As a result, this pseudo-gel-polymer separator with a tailored pore structure has uniform ion flux and enhanced interfacial properties with electrodes, contributing superior battery performance.

Quasi-Solid-State Electrolyte Synthesized Using a Thiol-Ene Click Chemistry for Rechargeable Lithium Metal Batteries with Enhanced Safety.

Liquid electrolytes currently used in lithium-ion batteries have critical drawbacks such as high flammability, high reactivity toward electrode materials, and solvent leakage. To overcome these issues, most recent research has focused on synthesis and characterization of highly conductive gel-type polymer electrolytes containing large numbers of organic solvents in the polymer matrix. There are still many hurdles to overcome, however, before they can be applied to commercial-level lithium-ion batteries. Since a large amount of organic solvent is required to achieve high ionic conductivity, battery safety is not significantly enhanced. In our study, we synthesized highly conductive quasi-solid-state electrolytes (QSEs) containing an ionically conductive oligomer (polycaprolactone triacrylate) and a small amount of organic solvent by employing click chemistry. In the QSE, polycaprolactone participates in dissociation of lithium salt and migration of lithium ions, resulting in high ionic conductivity. The Li/LiNi0.6Co0.2Mn0.2O2 cell that used this QSE exhibited good cycling performance and enhanced thermal stability, and durability; no organic solvent leakage was observed even under high pressure.

High-Voltage Operation of a V2O5 Cathode in a Concentrated Gel Polymer Electrolyte for High-Energy Aqueous Zinc Batteries.

Gel-type polymer electrolytes are very promising to replace liquid electrolytes, addressing the leakage concerns in batteries. In this work, we report a concentrated gel polymer electrolyte for aqueous zinc-metal batteries, which manifests superior Zn stripping/plating reversibility and electrolyte stability, combined with a promising electrochemical stability window and robust water-retention ability. Quasi-solid-state Zn/V2O5 batteries employing such an electrolyte reach a specific energy of 326 W h kg-1 at 20 mA g-1 based on the cathode mass and a capacity retention of 93% over 600 cycles at 500 mA g-1. Moreover, the cell performs well in the 0-40 °C temperature range without significant capacity loss. These results represent important steps toward the development of high-energy aqueous zinc batteries.

Preparation and characterization studies of PMMA–PEO-blend solid polymer electrolytes with SiO2 filler and plasticizer for lithium ion battery

Solid polymer electrolyte systems comprising of polyethylene oxide (PEO) and polymethyl methacrylate (PMMA) as blended polymer host, lithium trifluoromethanesulfonate (LiCF3SO3) as dopant salt, ethylene carbonate (EC) as plasticizer, and silicon dioxide (SiO2) as inorganic filler were prepared by solution casting method. PMMA–PEO–EC–LiCF3SO3–SiO2-blend solid polymer electrolytes were prepared to study the blending effect of PMMA into PEO solid polymer electrolytes. All the resulted solid polymer electrolytes were characterized using electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) methods. In the present study, the XRD, FTIR, SEM, and DSC results show clear evidence of the miscibility of PMMA and PEO. The incorporation of PMMA into the PMMA–PEO-blend solid polymer electrolytes shows significant improvement on ionic conductivity when small amount of PMMA is used. The highest ionic conductivity of 2.6301 × 10−4 S/cm is achieved for 5 wt% PMMA and 95 wt% PEO-blend solid polymer electrolytes at room temperature. The ionic conductivity values are found to be decreased when a higher wt% of PMMA is added. Upon incorporation of 20 wt% of PMMA, the ionic conductivity values are found in range of 10−6 to 10−7 S/cm. This finding is comparable with the reported results for gel-type polymer electrolytes. Hence, the amount of PMMA used in the PMMA–PEO-blend systems is crucial in the preparation of PMMA–PEO-blend solid polymer electrolyte.

Fluorinated polysulfonamide based single ion conducting room temperature applicable gel-type polymer electrolytes for lithium ion batteries

Single ion conducting polymer electrolytes (SIPEs) comprised of homopolymers containing a polysulfonylamide segment in the polymer backbone are presented.

A sandwich structure polymer/polymer-ceramics/polymer gel electrolytes for the safe, stable cycling of lithium metal batteries

The highest specific capacity (3860 mAh g−1) and minimum negative electrochemical potential make lithium metal as a perfect candidate for next-generation high energy battery. However, the safety issue caused by the lithium dendrite growth hinders the practical use of lithium metal battery. Herein, a polymer/polymer-ceramic/polymer sandwich structure electrolytes (SWEs) are proposed to address this problem by combing the advantage of inorganic and gel-type polymer electrolytes. The flexible SWEs show a high ionic conductivity (~3.01 ×10−3 S/cm) at room temperature, high lithium transference number (tLi+ = 0.74), and stable electrochemical widows up to 5.0 V. Furthermore, the SWEs can effectively prevent lithium dendrites in a symmetric Li/SWEs/Li test during charge and discharge with a current density of 1 mA/cm2 for 240 h at room temperature. Meanwhile, the lithium metal battery assembled using LiCoO2/SWEs/Li exhibits the high cycling capacity of ~ 110 mAh g−1 at 2 C over 100 cycles and fascinating rate performance (144 mAh g−1@ 1 C and 98 mAh g−1@ 5 C) at room temperature. Our work provides a new design paradigm to exploit the advanced electrolyte for lithium metal battery and flexible devices.

Recent Advances in Innovative Polymer Electrolytes based on Poly(ionic liquid)s

This article reviews the general strategies for the design of innovative polymer electrolytes using poly(ionic liquid)s. First, we review the properties of poly(ionic liquid)s as solid polymer electrolytes (SPEs). The different factors that affect the bulk ionic conductivity of poly(ionic liquid)s are discussed such as chemical nature of the cation, anion, the spacer, the polymer backbone and its glass transition temperature, the purity and water content. Special attention is given to the optimization of both the ionic monomer chemical structure and macromolecular architecture to achieve the highest possible polymer ionic conductivity (≈10−5S/cm at 25°C). Secondly, the preparation of gel type polymer electrolytes, named “ion gels”, based on ionic liquids and poly(ionic liquid)s is discussed in terms of preparation methods and composition. Due to the presence of free ions, such ion gels provide higher ionic conductivity (10−2−10−3S/cm at 25ºC) than SPEs. Finally, the actual applications of innovative polymer electrolytes based on poly(ionic liquid)s are summarized and their advantages are discussed.

An optimized poly(vinylidene fluoride-hexafluoropropylene)–NaI gel polymer electrolyte and its application in natural dye sensitized solar cells

Gel type polymer electrolytes with PVDF-HFP as polymer host, NaI salt and EC/PC as plasticizers have been prepared and optimized for use in a dye sensitized solar cell (DSSC). The polymer electrolyte containing 48wt. % (PVDF-HFP)–32wt. % NaI–20wt. % (EC/PC) exhibits the highest room temperature conductivity of 1.53×10−4 S cm−1. This electrolyte has been used in the fabrication of a DSSC with the configuration FTO/TiO2/natural dye/electrolyte/Pt/FTO. The natural dyes used anthocyanin and chlorophyll were solvent extracted from black-rice and pandanus amaryllifolius leaves respectively. UV-vis absorption spectra of anthocyanin, chlorophyll and the mixture of anthocyanin and chlorophyll in the volume ratio 1:1 were recorded. The anthocyanin shows an absorption peak at 532nm. In the same region chlorophyll absorption shows a peak at 536nm and also has a prominant peak at 665nm. On mixing anthocyanin and chlorophyll two prominant peaks are observed at 536 and 665nm. The DSSC containing the dye mixture exhibits the best performance with a short-circuit current density of 2.63mAcm−2, open-circuit voltage of 0.47V, fill factor of 0.58 and the highest photo-conversion efficiency of 0.72% under the illumination of 100mW cm−2 white light. Under illumination of lower light intensity of 60mW cm−2 and 30mW cm−2, the fill factor enhanced from 0.58 to 0.59 and 0.60 and the photo-conversion efficiency increased from 0.72% to 1.11% and 1.85% respectively.

Gel polymer electrolyte based on polyvinylidenefluoride-co-hexafluoropropylene and ionic liquid for lithium ion battery

Gel-type polymer electrolytes with 1-butyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide (B4MePyTFSI) ionic liquid are formed by the solution casting method. The conductivity and transference number measurements are carried out to investigate conductivity and charge transport in the gel polymer electrolytes. The conductivity of the samples increases when the amount of B4MePyTFSI ionic liquid is increased. The lithium ion ionic conductivity reaches the maximum value (2.01×10−4 S cm−1) when GPE contains 33.3 wt% B4MePyTFSI. The electrochemical stability window of ILGPE is about 5.5V versus Li+/Li at 20°C, meeting the basic requirement of rechargeable lithium batteries. Discharge performance of lithium battery using this ILGPE membrane shows a capacity of about 160 mAh g−1. The excellent performance with higher capacity, good cycle stability and compatibility are observed for the Li/ILGPE/LiFePO4 cells. The interfacial resistances between ILGPE and electrodes have the less change after 10 cycles.

Ionic Liquid‐Based Membranes as Electrolytes for Advanced Lithium Polymer Batteries

Gel-type polymer electrolytes are formed by immobilizing a solution of lithium N,N-bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-n-butyl-N-ethylpyrrolidinium N,N-bis(trifluoromethanesulfonyl)imide (Py₂₄TFSI) ionic liquid (IL) with added mixtures of organic solvents, such as ethylene, propylene and dimethyl carbonates (EC, PC, and DMC, respectively), into a poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) matrix, and their properties investigated. The addition of the organic solvent mixtures results in an improvement of the ionic conductivity and in the stabilization of the interface with the lithium electrode. Conductivity values in the range of 10⁻³-10⁻² S cm⁻¹ are obtained in a wide temperature range. These unique properties allow the effective use of these membranes as electrolytes for the development of advanced polymer batteries based on a lithium metal anode and an olivine-type lithium iron phosphate cathode.

The role of gel electrolyte composition in the kinetics and performance of dye-sensitized solar cells

Gel-type polymer electrolytes based on the copolymer poly(ethylene oxide-co-epichlorohydrin) and the plasticizer γ-butyrolactone (GBL) were optimized and applied in dye-sensitized solar cells. The plasticizer added to the electrolyte allowed the dissolution of a higher concentration of salt, reaching conductivity values close to 1 mS cm −1 for the sample prepared with 30 wt% of LiI. Raman spectroscopy confirmed polyiodide formation in the electrolyte when the salt concentration exceeds 7.5 wt%, introducing a significant contribution of electronic conductivity in the electrolyte. The devices were characterized under AM 1.5 conditions and the I– V curves were fitted using a two diode equation. Increasing the concentration of LiI-I 2 accelerates dye cation regeneration as measured by transient absorption spectroscopy; however, it also contributes to an increase in the dark current of the cell by one order of magnitude. The best performance was achieved for the solar cell prepared with the electrolyte containing 20 wt% of LiI, with efficiencies of 3.26% and 3.49% at 100 and 10 mW cm −2 of irradiation, respectively.

Composite gel-type polymer electrolytes for advanced, rechargeable lithium batteries

The main goal of this work was to determine whether the dispersion of ceramic fillers have any promotion effect on the properties of solid-like, gel-type lithium conducting polymer electrolytes. Using a series of different but complementary techniques, which included SEM analysis, voltammetry and impedance spectroscopy, we demonstrate that the dispersion of surface functionalized fumed silica and alumina, respectively, to PVdF–carbonate solvent–lithium salt systems, while not greatly influencing the transport properties, does stabilize the lithium metal interface and the mechanical properties of the resulting composite GPE electrolytes. The relevance of these features in view of practical application is here demonstrated by the response of lithium batteries based on selected GPEs.

The conductivity and characterization of the plasticized polymer electrolyte based on the P(AN-co-GMA-IDA) copolymer with chelating group (II): The effect of free ion in the plasticized polymer electrolyte

A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF 3SO 3, LiBr and LiClO 4. FT-IR spectra show that the lithium ion in the LiClO 4 system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF 3SO 3 − prefers producing anion–cation association. Moreover, the 13C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO 4 system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10 −3 S cm −1 exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer) −1 LiClO 4. Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.

Characteristics of Lithium-Gel Battery Based on a Li-Al Alloy Anode

LiAl alloy with trace Al doping was originally introduced as the anode of a lithium-gel battery. The characteristics of the lithium-gel polymer battery which comprised such a LiAl alloy anode, cathode, and poly(vinylidene fluoride)-based gel-type polymer electrolyte were investigated. It was indicated that such a LiAl alloy anode had similar charge/discharge behavior to a pure lithium anode. Although only Al was doped, the LiAl alloy showed obvious better surface stability than pure lithium in a gel battery, which resulted in lower interfacial resistance and interior impedance of cell. Consequently, the cycling efficiency and cycleability of the LiAl alloy cell was effectively improved in comparison with the cell using pure lithium anode.

Gel-type polymer electrolytes with different types of ceramic fillers and lithium salts for lithium-ion polymer batteries

Gel-type polymer electrolytes are prepared using PVdF/PEGDA/PMMA, LiPF 6/LiCF 3SO 3 mixed lithium salts and ceramic fillers such as Al 2O 3, BaTiO 3 and TiO 2. The electrochemical properties of these electrolytes, such as electrochemical stability, ionic conductivity and compatibility with electrodes are investigated in addition to the physical properties. The charge–discharge performances of lithium-ion polymer batteries using these get-type polymer electrolytes are investigated. The gel-type polymer electrolytes containing a mixed lithium salt of LiPF 6/LiCF 3SO 3 (10/1, wt.%) exhibit more stable ionic conductivity and lower interfacial resistance than those containing only LiPF 6. In addition, an Al 2O 3 filler improves interfacial stability between the electrode and the polymer electrolyte. Stacking cells (MCMB 1028/LiCoO 2, 8 cm × 13 cm × 7 ea) composed of gel-type polymer electrolytes based on PVdF/PEGDA/PMMA, LiPF 6/LiCF 3SO 3 (10/1, wt.%) and Al 2O 3 filler maintain 95% of initial capacity after 100 cycles at a C/2 rate.

Novel polymeric systems for lithium ion batteries gel electrolytes: II. Hybrid cross-linked poly(fluorosilicone-ethyleneoxide)

Cross-linked, self-supporting, membranes for lithium ion battery gel electrolytes were obtained by cross-linking a mixture of polyfluorosilicone (PFSi) and polysilicone containing ethylene oxide (EO) units [P(Si-EO)]. The membranes were also reinforced with nanosized silica. The two polymer precursors were synthesized with functional groups capable to form inter-molecular cross-linking, thus obtaining three-dimensional, polymer matrices. The precursors were dissolved in a common solvent and cross-linked to obtain free-standing PFSi/P(Si-EO):SiO 2 composite films. The latter were undergone to swelling processes in (non-aqueous, aprotic, lithium salt containing) electrolytic solutions to obtain gel-type polymer electrolytes. The properties of the swelled PFSi/P(Si-EO):SiO 2 samples were evaluated as a function of the electrolytic solutions and the dipping time. The PFSi/P(Si-EO):SiO 2 membranes exhibited large swelling properties, high ionic conductivity and good electrochemical stability.