Conductivity Of Gel Polymer Electrolyte Research Articles

Effect of introducing different molecular liquid solvents on electrochemical and physical properties of sodium ion conducting polymer gel electrolytes

The current investigation presents comparative studies on the effect of introducing three different molecular liquid solvents, namely ethylene carbonate: diethyl carbonate (EC:DEC), tetra ethylene glycol dimethyl ether (TEGDME), and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) on the electrochemical and physical properties of sodium ion conducting polymer gel electrolytes (PGEs) containing sodium tetrafluoroborate (NaBF4) salt, and polyvinyllidene fluoride-co-hexafluoropropylene (PVdF-HFP) polymer. The PGE, which is optimized and contains the EC: DEC solvent, has an ionic conductivity of 8.9 × 10−4 S cm−1, electrochemical stability of 4.5 V and total ion transport number of 0.99 at 30 °C. Along with conductivity studies, the X-ray diffraction studies, show that the EC: DEC raises the entropy of the PGE to its maximum value. The thermogravimetric (TGA) and differential scanning calorimetry (DSC) investigations demonstrate that electrolyte with EC: DEC exhibits a weight loss of 13 % up to 200 °C and retain the gel phase up to 140 °C. The optimized electrolyte holds promise for forthcoming sodium based electrochemical devices.

Charge carrier dynamics and relaxation in highly conducting gel polymer electrolytes added with adiponitrile and dual redox

The fundamental understanding of the relationship between ion transport and segmental dynamics of polymer chains in polymer electrolytes is crucial for achieving high ionic conductivity at room temperature for technological applications in supercapacitors, batteries, etc. In this work, the ion dynamics and relaxation have been studied for gel polymer electrolytes (GPEs) containing P(VdF-HFP) as host polymer, adiponitrile as a plasticizer, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as ionic liquid, and diphenylamine and copper iodide redox additives as fillers. The crystallization temperature of the ionic liquid and the melting temperature of the plasticizer play important roles in ion dynamics. The highest room-temperature ionic conductivity (3.3 × 10−3 S/cm) was obtained for the GPE filled with dual redox additives. The broadband ac conductivity spectra have been analyzed by using the Universal Power law model coupled with the Poisson–Nernst–Planck (PNP) model. The solid–solid phase transition of the ionic liquid affects the grain and grain boundary regions of the GPEs due to the presence of redox fillers. The temperature dependence of the dielectric spectra of the GPEs containing redox fillers confirms the phase transition at the crystallization temperature. The electric modulus and dielectric spectra have been analyzed by using the Havrilliak–Nigami, Kohlrausch–Williams–Watts, and derivative dielectric constant functions. The scaling of ac conductivity and modulus spectra confirms a common ion conduction and relaxation mechanism for the GPEs. The influence of dual redox additives is clearly observed in the values of ionic conductivity, ion diffusivity, and relaxation time.

Perfluorinated Single-Ion Li+ Conducting Polymer Electrolyte for Lithium-Metal Batteries

Single-ion (Li+) conducting electrolytes with a high Li+ conductivity and transference number (LTN) are promising electrolyte candidates for eliminating the concentration polarization and inhibiting the growth of lithium dendrites in lithium-metal batteries at high power and energy densities. This study presents the synthesis and electrochemical characterization of an AB-type single-ion Li+ conducting polymer consisting of a perfluorinated lithium-salt monomer (A) covalently bonded to a polyethylene glycol monomer (B). An investigation into several plasticizers reveals that ether-based solvents with moderate dielectric constants significantly enhance the Li+ conductivity of single-ion (Li+) conducting gel polymer electrolytes (SIC-GPE) while also maintaining the mechanical integrity of SIC-GPE. The perfluorinated lithium-salt units with weakly coordinating anions provide the advantage of high Li+ conductivity (1.1 × 10–4 S cm–2) and transference number (0.92), while polyethylene glycol units contribute to high flexibility and enhance plasticizer wettability in the SIC-GPE. The interfacial stability and electrochemical performance of SIC-GPE are demonstrated in lithium-metal symmetric cells (maintaining stability for >1300 h at 1 mAh cm–2) and lithium-metal batteries (retaining 98% capacity after 200 cycles).

Studies on potassium-ion conducting gel polymer electrolytes containing poly(vinylidene fluoride-hexafluoropropylene) polymer, potassium permanganate salt added with different plasticizers

Studies on potassium-ion conducting gel polymer electrolytes containing poly(vinylidene fluoride-hexafluoropropylene) polymer, potassium permanganate salt added with different plasticizers

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

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

Impact of Ammonium Perchlorate Content on Electrically Controlled Gel Polymer Electrolyte Monopropellants

A group of five electrically controlled monopropellants were developed, and their fundamental rheological, electrochemical, thermal, and combustion properties were characterized. A baseline monopropellant was composed of lithium perchlorate complexed with polyethylene glycol to form an ionically conductive gel polymer electrolyte. Subsequent candidates were supplemented with varying amounts of ammonium perchlorate at a fixed polymer-to-oxidizer ratio to determine the effects of shifting oxidizer content on the fundamental properties. The ignition of the gel monopropellants using an applied DC voltage potential at atmospheric conditions was observed and determined to be primarily the result of an electrolytic reaction. Time-resolved infrared thermography confirmed initial heating and initiation of the gels at the cathode once temperatures had reached the decomposition temperature of the polymer. Fourier transform infrared analysis of collected residue from experiments halted before ignition revealed lithium deposition on the cathode, supporting electrochemical activity. It was found that the electrolytic ignition delay time was affected by the oxidizer content, the magnitude of the applied voltage, and the distance between the electrodes supplying the voltage.

A salt-free poly(acrylic acid) hydrogel electrolyte with self-released ions for quasi-solid-state electrochromic devices

The ionic conductivity of gel polymer electrolytes (GPEs) is usually provided by the added inorganic salt ions. Here, we report a salt-free poly(acrylic acid) (PAA) hydrogel electrolyte with an ionic conductivity of 3.7 × 10−3 S cm−1. The carboxylic groups of PAA can release free H+ ions to provide ionic conductivity, which not only simplifies the preparation of GPEs, but also benefits the fabrication of GPEs with high transparency (>95.6 % from 400 to 1000 nm). The as-prepared hydrogel electrolyte is assembled into an electrochromic (EC) device (ECD) by using Prussian blue/PAA GPE/hydrated tungsten trioxide. The fabricated ECD achieves a high optical modulation (72.7 %), fast responses (2.6 s for coloration and 2.2 s for bleaching), a high coloration efficiency (172.9 cm2 C−1) and good cycling stability (retaining 96.3 % of the original optical modulation after 1200 cycles). Moreover, the ECD has good energy storage properties, demonstrating a potential application for energy-storage smart windows.

Rapid self-healing, highly conductive and near-single-ion conducting gel polymer electrolytes based on dynamic boronic ester bonds for high-safety lithium metal batteries

Polymer electrolytes with high ionic conductivity and good self-healing capability are crucial for the development of lithium metal batteries with enhanced rate capability and safety. However, the application of self-healable polymer electrolytes is hindered by low ionic conductivity and slow self-healing speed. Herein, boronic ester based self-healing gel polymer electrolyte (PBAD-PEG) with high ionic conductivity and fast self-healing speed is developed. PBAD-PEG is fabricated by thiol-ene click reaction of a multifunctional monomer 2,2′-(1,4-phenylene)-bis (4-allyloxy-1,3,2-dioxaborolane) (PBAD) consisting of two dynamic boronic ester bonds, pentaerythritol tetra(3-mercaptopropionate) and polyethylene glycol diacrylate. Abundant reversible boronic ester bonds endow PBAD-PEG with good flexibility and excellent self-healing ability. PBAD-PEG can self-heal within 1 h at room temperature after damaged, which effectively restores the ionic conductivities and mechanical properties. PBAD-PEG possesses high ionic conductivity of 8.67 × 10−4 S cm−1 at 25 °C. Lewis acid-base interactions between anions and boron atoms of PBAD-PEG contributes to ultrahigh lithium-ion transference number of 0.71. PBAD-PEG exhibits significant resistance to the growth of Li dendrites. The fabricated LiFePO4/Li batteries with PBAD-PEG achieve significantly boosted cycle stability (capacity retention of 92.6 % after 150 cycles). More importantly, LiFePO4/Li cells with the healed PBAD-PEG also show excellent cycle performance.

Polymer gel electrolytes containing sodium salts with BF4−, ClO4− and CF3SO3− anions immobilized in TEGDME molecular liquid for sodium battery and electric double layer capacitor

The present study reports synthesis and analysis of different characteristics of sodium ion conducting polymer gel electrolytes (PGEs) containing sodium salts with BF4−, ClO4− and CF3SO3− anions dissolved in tetraethylene glycol dimethyl ether and immobilized in a copolymer matrix consisting of polymethyl methacrylate and poly(vinylidene fluoride-co-hexafluoropropylene). The PGE containing the NaBF4 salt could deliver an ionic conductivity of 1.4 × 10−3 S cm−1 at room temperature along with superior dielectric properties as compared to the electrolytes with NaClO4 and NaCF3SO3 salts. The feasibility of designing sodium-based batteries and EDLCs has been demonstrated using the optimized PGE containing NaBF4 salt. The prototype sodium‑sulfur (NaS) battery designed by utilizing the optimized PGE, sodium amalgam anode and sulfur cathode provides open circuit voltage of ∼2.4 V and initial discharge capacity of ∼163 mA h g−1 and 126 mA h g−1 at discharge currents of 33 mA g−1 and 66 mA g−1, respectively. This optimized PGE also demonstrate good compatibility with AC electrodes in electric double layer capacitor (EDLC) application and delivered a significant specific capacity ∼64 F g−1 at 0.5 mA cm−2 current.

In-Situ Crosslinked Single-Ion Conducting Gel Polymer Electrolyte for Lithium Metal Batteries

Lithium metal batteries (LMBs) have been considered as promising candidates for energy storage device due to their high energy density. However, high reactivity of lithium metal with liquid electrolyte and continuous growth of dendrite lead to degradation of cycle performance and cell failure. To overcome these problems, the strategy of employing gel polymer electrolytes (GPE) was investigated. GPE can effectively encapsulate organic solvents and facilitate uniform contact with electrodes. Both cations and anions migrate in conventional GPE, which gives rise to low Li+ ion transference number (tLi+). Low tLi+ causes inhomogeneous Li+ ion flux and continuous dendrite growth. Compared to conventional GPE, single-ion conducting gel polymer electrolytes (SIC-GPE) have superior tLi+ value close to unity, since the movement of anions is suppressed. In this work, we synthesized a novel sulfonamide based single-ion conductor and prepared the chemically crosslinked SIC-GPE. The electrolyte was obtained by a facile in-situ crosslinking that further improves interfacial contact with electrodes. The resulting SIC-GPE exhibited high tLi+, which led to homogeneous deposition of Li+ ion and enhanced electrochemical stability. The LMB cell employing SIC-GPE exhibited stable cycle performance, proving ability to suppress the growth of lithium dendrite.

Fourier transform infrared studies of gel polymer electrolyte based on poly(acrylamide-co-acrylic acid) – Ethylene carbonate incorporated with water-soluble sodium sulfide

The incorporation of plasticizer to a solid polymer electrolyte have shown high conductivity, good thermal and chemical stabilities, long life and reduced costs. The improved conductivity is mainly contributed by higher ion diffusion coefficient and better ion mobility. However, little is known about the possible molecular interactions between plasticizer, polymer host and salt, particularly in explaining the mechanism pertaining to ion transport in the gel polymer electrolytes (GPEs). A flexible GPE based on poly(acrylamide-co-acrylic acid) (PAAm-PAA), ethylene carbonate (EC) and water-soluble sodium sulfide (Na2S) was developed. PAAm-PAA and Na2S are incorporated as the polymer backbone and the source of charge carriers, respectively, and EC acts as the plasticizer of the system. When 0.4 wt% of EC was added to PAAm-PAA-Na2S GPE, the ionic conductivity of polymer electrolytes increased from 5.11 × 10−2 S cm−1 to 6.92 × 10−2 S cm−1. The possible molecular interactions between PAAm-PAA, Na2S and EC and their correlation with ionic conductivity were investigated by Fourier transform infrared (FTIR) spectroscopy. Infrared spectroscopy showed that the intensities of the amide (CO, C–N), carboxylate (COO−) and sulfate (SO42−) bands increased with the addition of EC, and the position of the asymmetric bending (v4) of SO42− band down shifted from 677 cm−1 to 667 cm−1. These findings, the changes in shape, intensity, and position of the PAAm-PAA-Na2S-EC GPE, suggest a dipole-dipole interaction between (i) PAAm-PAA and distilled water, (ii) PAAm-PAA and EC and (iii) EC and distilled water. On the other hand, ion-dipoles interactions may occur between (i) Na+ cation and distilled water, (ii) Na+ cation and PAAm-PAA and (iii) Na+ cation and EC. It can be concluded that EC interacts with both PAAm-PAA and Na2S, and EC-Na+ complexes also appear in PAAm-PAA-Na2S-EC GPE. The increase in the conductivity of GPE is attributed to the high ion diffusion coefficient and mobility, which is attributed to the presence of EC.

Dynamic Networks of Cellulose Nanofibrils Enable Highly Conductive and Strong Polymer Gel Electrolytes for Lithium‐Ion Batteries

AbstractTunable dynamic networks of cellulose nanofibrils (CNFs) are utilized to prepare high‐performance polymer gel electrolytes. By swelling an anisotropically dewatered, but never dried, CNF gel in acidic salt solutions, a highly sparse network is constructed with a fraction of CNFs as low as 0.9%, taking advantage of the very high aspect ratio and the ultra‐thin thickness of the CNFs (micrometers long and 2–4 nm thick). These CNF networks expose high interfacial areas and can accommodate massive amounts of the ionic conductive liquid polyethylene glycol‐based electrolyte into strong homogeneous gel electrolytes. In addition to the reinforced mechanical properties, the presence of the CNFs simultaneously enhances the ionic conductivity due to their excellent strong water‐binding capacity according to computational simulations. This strategy renders the electrolyte a room‐temperature ionic conductivity of 0.61 ± 0.12 mS cm−1 which is one of the highest among polymer gel electrolytes. The electrolyte shows superior performances as a separator for lithium iron phosphate half‐cells in high specific capacity (161 mAh g−1 at 0.1C), excellent rate capability (5C), and cycling stability (94% capacity retention after 300 cycles at 1C) at 60 °C, as well as stable room temperature cycling performance and considerably improved safety compared with commercial liquid electrolyte systems.

Novel Single-Ion Conducting Gel Polymer Electrolyte with Honeycomb-Like Morphology Prepared Using Brush Copolymer for Lithium-Ion Battery Application

In this work, a facile and accurate method is reported for the delocalization of negative charge on fluorinated polymers to obtain high-performance single-ion conducting polymer electrolytes (SICPs) based on brush copolymers with simultaneous high ionic conductivity and tLi+. The poly(styrene sulfonate) (PSSA) single ion-conducting moieties were grafted-from C–F linkages to the fluorinated polymer’s backbone via the atom transfer radical polymerization method. The chemical structure characterization of the synthesized brush copolymers via 1H-NMR and thermal gravimetric analyses (TGA) confirmed 25% grafting of PSSA to the poly(vinylidene fluoride) backbone. In continue, the pristine and single-ion fluorinated polymer membranes with bi-continuous honeycomb-like morphology structures were prepared via the vapor-induced phase inversion (VIPS) method. After immersing in a liquid electrolyte, the prepared SICP demonstrated promising ionic conductivity (σ), t Li+ , and electrochemical stability of 1.9 × 10−3 Scm−1, 0.82, and 5.2 V (vs Li+/Li), respectively. The assembled Li/SICP/LiMn2O4 half-cells revealed an improved discharge capacity of 168 mA hg−1 at 0.1C. The charge-discharge studies revealed that the ohmic-resistance and polarization resistance of fluorinated polymer electrolytes could be decreased by the effect of PSSA-grafted moieties. The results of this work confirmed the promising capability of these new SICPs for high-safety LIBs.

Polystyrene-Based Single-Ion Conducting Polymer Electrolyte for Lithium Metal Batteries

Lithium metal batteries are one of the more promising replacements for lithium-ion batteries owing to their ability to reach high energy densities. The main problem limiting their commercial application is the formation of dendrites, which significantly reduces their durability and renders the batteries unsafe. In the present work, we used a single-ion conducting gel polymer electrolyte based on a poly(ethylene-ran-butylene)-block-polystyrene (SEBS) block copolymer, which was functionalized with benzenesulfonylimide anions and plasticized by a mixture of ethylene carbonate and dimethylacetamide (SSEBS-Ph-EC-DMA), with a solvent uptake of 160% (~12 solvent molecules per one functional group of the membrane). The SSEBS-Ph-EC-DMA electrolyte exhibits an ionic conductivity of 0.6 mSm∙cm−1 at 25 °C and appears to be a cationic conductor (TLi+ = 0.72). SSEBS-Ph-EC-DMA is electrochemically stable up to 4.1 V. Symmetrical Li|Li cells; further, with regard to SSEBS-Ph-EC-DMA membrane electrolytes, it showed a good performance (~0.10 V at first cycles and <0.23 V after 700 h of cycling at ±0.1 mA∙cm−2 and ±0.05 mAh∙cm−2). The LiFePO4|SSEBS-Ph-EC-DMA|Li battery showed discharge capacity values of 100 mAh∙g−1 and a 100% Coulomb efficiency, at a cycling rate of 0.1C.

Failure Mechanisms at the Interfaces between Lithium Metal Electrodes and a Single-Ion Conducting Polymer Gel Electrolyte.

Polymer electrolytes have the potential to enable rechargeable lithium (Li) metal batteries. However, growth of nonuniform high surface area Li still occurs frequently and eventually leads to a short-circuit. In this study, a single-ion conducting polymer gel electrolyte is operated at room temperature in symmetric Li||Li cells. We use X-ray microtomography and electrochemical impedance spectroscopy (EIS) to study the cells. In separate experiments, cells were cycled at current densities of 0.1 and 0.3 mA cm-2 and short-circuits were obtained eventually after an average of approximately 240 cycles and 30 cycles, respectively. EIS reveals an initially decreasing interfacial resistance associated with electrodeposition of nonuniform Li protrusions and the concomitant increase in electrode surface area. X-ray microtomography images show that many of the nonuniform Li deposits at 0.1 mA cm-2 are related to the presence of impurities in both electrolyte and electrode phases. Protrusions are globular when they are close to electrolyte impurities but are moss-like when they appear near the impurities in the lithium metal. At long times, the interfacial resistance increases, perhaps due to additional impedance due to the formation of additional solid electrolyte interface (SEI) at the growing protrusions until the cells short. At 0.3 mA cm-2, large regions of the electrode-electrolyte interface are covered with mossy deposits. EIS reveals a decreasing interfacial resistance due to the increase in interfacial area up to short-circuit; the increase in interfacial impedance observed at the low current density is not observed. The results emphasize the importance of pure surfaces and materials on the microscopic scale and suggest that modification of interfaces and electrolyte may be necessary to enable uniform Li electrodeposition at high current densities.

Muscovite as an inert filler for highly conductive and durable gel polymer electrolyte in sodium-ion batteries

Sodium-ion batteries emerge as complementary to commercially established lithium-ion batteries. The keynote of the presented study is sodium gel polymer electrolyte for efficient and safer post-lithium batteries. The study aims at better mechanical strength, higher ionic conductivity, and improved thermal properties of the gel polymer electrolyte. These properties strongly depend on the composition of the electrolyte. Ionic liquid and sulfolane as plasticizers improved the ionic conductivity of the electrolyte up to 5.5 mS cm−1. Polyacrylonitrile matrix established flexibility and mechanical strength up to 5.9 MPa. However, the most significant change is the partial substitution of polymer with an inert filler. For the first time, the inert filler in sodium gel polymer electrolyte is muscovite, which affects most of the properties of the polymer electrolytes. It broadens the anodic region of the electrochemical window even by 200 mV and reduces the dimensional shrinkage of the electrolyte by 1–4% compared to the reference sample. Furthermore, muscovite enhances the tensile strength of the electrolyte, delays thermal degradation, and improves the long-term stability of the GPE/Na interface. It also assures that the gel electrolyte is compatible with a hard carbon anode in a cell that delivers a capacity of 200 mAh g−1 at C/20.

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

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

Effect of Glycerin on Electrical and Thermal Properties of PVA/Copper Sulphate Gel Polymer Electrolytes

Copper-ion conducting gel polymer electrolyte (GPE) systems based on polymer poly(vinyl alcohol) (PVA) and copper sulphate salt doped with glycerin as plasticizer have been synthesized by using solution casting technique. Differential scanning calorimetry (DSC) is used to examine the thermal effect of glycerin on a polymer electrolyte. With the addition of various quantities of glycerin, as a plasticizer in pure PVA and PVA + 20 wt% CuSO4 polymer electrolyte shows a decrease in the values of melting temperature, glass transition temperature and percentage of crystallinity. From TGA curves, it is observed that thermal degradation of the glycerin doped polymer electrolyte is shifted towards lower temperature when compared to pristine PVA and the weight loss of the polymer electrolyte increases with increase of glycerin concentration. From DTG analysis, the temperature of maximum decomposition for PVA is 283.4 °C and it is decreased by the addition of 20 wt% CuSO4 and upon increased concentration of the plasticizer from 1 to 3 mL of glycerin. For pure PVA and PVA + 20 wt% CuSO4, ε′ decreases with increasing glycerin concentration and is lowest at 3 mL glycerin concentration. The maximum ionic conductivity obtained was 9.39 × 10− 4 S/cm for PVA + 20 wt% CuSO4 + 3 mL glycerin gel polymer electrolyte. The above results suggested that, the optimum conducting sample is suitable as separator in rechargeable batteries.

The effects of solvents on the physical and electrochemical properties of potassium-ion conducting polymer gel electrolytes

The aim of present work is to investigate the effect of different solvent mixed within poly (vinylidiene fluoride-hexafluoropropylene) (PVDF-HFP) based Potassium ion conducting polymer gel electrolytes. The samples are prepared using solution casting method and the comparative behavior of adding carbonate and glyme in PVDF-HFP/KClO4 matrix is investigated. Subsequently, polymer gel electrolytes are characterized using X-ray diffractometer to analyze the structural features of the electrolyte films. The XRD results reveal that the prepared electrolyte films using both solvents demonstrate semi-crystalline nature. The surface morphology is studied using scanning electron microscopy and significant changes in surface morphology of the polymer gel electrolyte films is observed on introducing carbonate and glyme solvents. Thermal properties and effects of temperature on the prepared electrolytes is examined using differential scanning calorimetry and investigations reveal significant effect of temperature on the heat flow into the polymer gel electrolytes samples. The weight loss of the electrolyte samples with temperature is studied using Thermogravimetric analysis and it is observed that carbonate and glyme based electrolyte offer weight loss of about 7–8 %. The ionic conductivity of 2.53×10−7 Scm−1 and 3.67×10−4 Scm−1 while electrochemical stability window of ∼2.5 V is obtained for both polymer gel electrolytes with carbonate and glyme based solvents. The reversibility of K-ion has been established using cyclic voltammetry measurements.

Lithium dendrite suppression by single-ion conducting gel polymer electrolyte cross-linked with graphene oxide

This study presents a preparation of single-ion conducting gel polymer electrolytes (SPGEs) and their application for lithium metal battery systems. SGPEs are prepared by an in-situ cross-linking reaction of methacrylate-graphene oxide (MGO) and lithium cation conducting monomer (LiMTFSI) using poly(vinylidene fluoride-co-hexafluoropropylene) (PVH) as a matrix polymer. The SGPEs prepared by the in-situ cross-linking reaction with MGO are found to have highly porous structure leading to the high liquid electrolyte uptake and high ionic conductivity. The cross-linked SGPEs show improved mechanical strength, thermal and electrochemical stability compared with the SGPE without any MGO cross-linker. In addition, lithium dendrite growth is successfully suppressed by the cross-linked SGPE because it contains single ion conducting LiMTFSI moiety and MGO cross-linker having 2D structure with many lithiophilic moieties. As a result, lithium metal batteries assembled with SGPE show much improved cycle performance compared to the conventional Celgard-liquid electrolyte system.