Porous Polymer Electrolyte Research Articles

Preparation of porous polyacrylonitrile membrane-based gel polymer electrolyte for solid-state supercapacitor

Recently, solid polymer electrolytes (SPEs) are of great current interest as substitutes to conventional liquid type electrolytes. Although the SPEs significantly alleviate the safety issues of the lithium-ion batteries based on conventional liquid electrolytes, they intrinsically exhibit low ion conductivity. In this study, a bicontinuous solid polymer electrolyte containing polyacrylonitrile (PAN) membrane and a mixture of succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide was prepared with different molarities of the lithium salt. Porous PAN membrane was fabricated via a thermally induced phase separation method (TIPS). The PAN-based SPE exhibited the maximum ionic conductivity of ∼5.0 10−3 S/cm at the salt molarity of 1.0 M.

Porous Polymer Gel Electrolytes Influence Lithium Transference Number and Cycling in Lithium-Ion Batteries

To improve the energy density of lithium-ion batteries, the development of advanced electrolytes with enhanced transport properties is highly important. Here, we show that by confining the conventional electrolyte (1 M LiPF6 in EC-DEC) in a microporous polymer network, the cation transference number increases to 0.79 while maintaining an ionic conductivity on the order of 10−3 S cm−1. By comparison, a non-porous, condensed polymer electrolyte of the same chemistry has a lower transference number and conductivity, of 0.65 and 7.6 × 10−4 S cm−1, respectively. Within Li-metal/LiFePO4 cells, the improved transport properties of the porous polymer electrolyte enable substantial performance enhancements compared to a commercial separator in terms of rate capability, capacity retention, active material utilization, and efficiency. These results highlight the importance of polymer electrolyte structure–performance property relationships and help guide the future engineering of better materials.

Porous Composite Gel Polymer Electrolyte with Interfacial Transport Pathways for Flexible Quasi Solid Lithium-Ion Batteries.

The growing demand for safer energy storage devices leads to wide research on solid-state lithium-ion batteries. However, as an important component in the solid-state battery, the solid-state electrolyte often encounters problems, especially the low conductivity at room temperature, inhibiting the development of solid-state batteries. Here, improved electrochemical performances of lithium-ion batteries are obtained by designing a composite gel polymer electrolyte with a sponge-like structure. The porous composite gel polymer electrolyte (PCGPE) is developed by a facile phase inversion process of poly(vinylidiene fluoride-hexafluoropropylene) (PVdF-HFP) and Li6.4La3Zr1.4Ta0.6O12 (LLZTO). The solid-state nuclear magnetic resonance test proves the continuous porous structure constructs fast Li-ion transport pathways on internal interfaces. As a result, the ionic conductivity of PCGPE is up to 5.45 × 10-4 S cm-1 at room temperature. Moreover, an initial capacity of 142.2 mAh g-1 and 82.6% capacity retention at 1 C after 350 cycles are successfully achieved in flexible LiFPO4//PCGPE//Li batteries.

Graphite/copper nanoparticle-based high-performance micro supercapacitor with porous wet paper-based PVA-PVP blend polymer electrolyte

A 2D supercapacitor with graphite/copper nanoparticle electrodes and a PVA-PVP polymer electrolyte was screen printed. A novel method to deposit the electrolyte on the current collectors using a porous wet paper has been described to overcome several disadvantages of conventional solid-state gel electrolytes. SEM imaging showed the ideal size of deep pores in the paper-based medium which assisted the electrolyte in storing charge and facilitated high conductivity and capacitance. Electrochemical analysis via Cyclic Voltammetry at various scan rates showed a specific capacitance of 24.12 F g−1. Cyclic stability and charge-discharge times were studied via galvanostatic charge-discharge cycles. The excellent flexibility of the device has been demonstrated by plotting the absolute and relative resistance change across the Cu electrodes at different bending angles with the maximum relative resistance change shown to be less than 5%.

Studies on ionic liquid based nanocomposite gel polymer electrolyte and its application in sodium battery

A nanocomposite gel polymer electrolyte system comprising porous membrane of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/TiO2 immobilizing a liquid electrolyte of sodium trifluoromethanesulfonate (NaCF3SO3) in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMImCF3SO3) ionic liquid is reported in the paper. The porous gel polymer electrolyte membranes are prepared by phase-inversion technique. The electrolyte membranes are characterized by various physical and electrochemical techniques. The TiO2 nanoparticles display interaction with the anion (CF3SO3−) of the liquid electrolyte and enhance amorphicity in the polymer network. The optimized membrane displays maximum room temperature ionic conductivity as ~0.4 mS cm−1 with improved electrochemical stability window of ~4.3 V and Na+ ion transport number as ~0.27. A proto-type sodium battery using the optimized membrane is fabricated and characterized. The battery delivers a stable open circuit potential of ~2.2 V and shows a discharge capacity ~200 mA h g−1 at 25 mA g−1 drain current.

Porous gel polymer electrolyte for the solid state metal oxide supercapacitor with a wide potential window

The potential window plays an important role in the performance of a supercapacitor and the gel polymer electrolyte (GPE) is the widespread interest in this context. GP electrolytes have high ionic conductivity, excellent electrochemical stability, and suitable ion transfer. So, in this work, the porous poly(acrylonitrile-polyhedral oligomeric silsesquioxane) (P(A-POS)) membrane electrolyte has been proposed for the metal oxide-based supercapacitors. The porous membrane was synthesized via the phase inversion process and after the liquid organic electrolyte uptake, it was used as GPE in Co3O4 nanoribbon/activated carbon asymmetric supercapacitor. The positive electrode based on Co3O4 nanoribbon (NR-Co3O4) offered a high specific capacitance of 2380.4 mF cm−2 at a current density of 2 mA cm−2 and the organic liquid electrolyte uptake of (P(A-POS)) membrane was 405%. The results indicated that the supercapacitor with NR-Co3O4 positive electrode and (P(A-POS)) porous membrane shows wide potential window of 4 V and low charge transfer resistance of 1.1 Ω in a solid-state asymmetric supercapacitor.

Porous polymer electrolytes for long-cycle stable quasi-solid-state magnesium batteries

A flexible porous polymer electrolyte (PPE) was creatively designed for quasi-solid magnesium battery. The MoS 2 /C//PPE//Mg battery exhibited high reversible capacity and unprecedentedly long cycling life. The development of applicable electrolytes is the key point for high-performance rechargeable magnesium batteries (RMBs). The use of liquid electrolyte is prone to safety problems caused by liquid electrolyte leakage. Polymer-based gel electrolytes with high ionic conductivity, great flexibility, easy processing, and high safety have been studied by many scholars in recent years. In this work, a novel porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane is prepared by a phase inversion method. By immersing porous PVDF-HFP membranes in MgCl 2 -AlCl 3 / TEGDME (Tetraethylene glycol dimethyl ether) electrolytes, porous PVDF-HFP based electrolytes (PPEs) are formed. The PPE exhibits a high ionic conductivity (4.72 × 10 −4 S cm −1 , 25 °C), a high liquid electrolyte uptake of 162%, as well as a wide voltage window (3.1 V). The galvanostatic cycling test of Mg//Mg symmetric cell with PPE reveals that the reversible magnesium ion (Mg 2+ ) plating/stripping occurs at low overpotentials (~0.13 V). Excellent long cycle stability (65.5 mAh g −1 over 1700 cycles) is achieved for the quasi-solid-state RMB assembled with MoS 2 /C cathode and Mg anode. Compared with the liquid electrolyte, the PPE could effectively reduce the side reactions and make Mg 2+ plating/stripping more uniformly on the Mg electrode side. This strategy herein provides a new route to fabricate high-performance RMB through suitable cathode material and polymer electrolyte with excellent performance.

Performance enhancement of Na+ ion conducting porous gel polymer electrolyte using NaAlO2 active filler

In this paper, we report the enhanced electrochemical characteristic performance of porous gel polymer electrolyte, due to dispersion of sodium aluminate (NaAlO2) active fillers in it. The salt solution consisting of, sodium perchlorate (NaClO4) dissolved in binary mixture of ethylene carbonate and propylene carbonate (EC:PC) was entrapped in poly(vinylidinefluoride-co-hexafluoropropylene) (PVdF-HFP) polymer matrix to obtain the micro-porous sodium ion conducting gel polymer electrolyte films by using the phase inversion technique. Small loading of the active NaAlO2 fillers in gel polymer electrolyte results in significantly improved ionic conductivity (σmax=0.68 mS cm−1 at room temperature), Na+ ion transference number (tNa+∼ 0.45) and electrochemical stability window (ESW ∼ 4.1 V). Dielectric studies have been performed to explore the ion dynamics in the electrolyte system. The Na-S prototype battery delivers maximum discharge capacities of ∼ 210, 139 and 51 mA h g−1 at drain currents of 0.10, 0.25 and 0.50 mA cm-2, respectively. The optimized electrolyte composition with high liquid retention, conductivity and transport properties can be utilized for upcoming sodium batteries operating at room temperature.

Stabilizing Liquid Electrolytes in a Porous PVDF Matrix Incorporated with Star Polymers with Linear PEG Arms and CycloPEG Cores.

Porous membranes fabricated from poly(vinylidene fluoride) (PVDF) and a star polymer with linear poly(ethylene glycol) (PEG) arms and cycloPEG cores were fabricated via the phase-separation method. The porous gel polymer electrolytes (PGPEs) were obtained by immersing the porous membranes in the electrolyte solution. When the additive amount of star polymer was up to 20 wt %, the prepared membrane had the largest porosity and the pores were uniformly distributed in the membrane. The star polymer can not only decrease the crystallization of PVDF and enhance the absorption of liquid electrolyte but also offer ion conduction channels (cycloPEG cores). Therefore, the PGPE with 20 wt % star polymers exhibited competitive ionic conductivities of 1.27 mS cm-1 at 30 °C and 2.89 mS cm-1 at 80 °C. To stabilize the liquid electrolyte in the holes of porous membranes, a gelator was introduced in the liquid electrolyte to form gelled porous gel polymer electrolytes (GPGPEs), and the leakage of liquid electrolytes was thus remarkably reduced. The ionic conductivity of GPGPEs with 20 wt % star polymer and 1.5 wt % gelator was importantly improved at high temperatures (6.02 mS cm-1 at 80 °C). We systematically investigated the electrochemical performances of PGPEs without star polymer, PGPEs with star polymer, and GPGPEs with star polymer. The incorporation of star polymers with linear PEG arms and cycloPEG cores into the PGPEs and GPGPEs significantly improved the electrochemical performances of the lithium metal/LiFePO4 cell assembled with the PGPEs or GPGPEs.

Polyacrylonitrile-based gel polymer electrolyte filled with Prussian blue forhigh-performance lithium polymer batteries

Lithium polymer batteries (LPBs) rely on a high ion transport to gain improved cell performance. Thermostable and porous gel polymer electrolytes (GPEs) have attracted much attention due to their excellent properties in electrolyte wettability and ionic conductivity. In this work, iron-nickel-cobalt trimetal Prussian blue analogue (PBA) nanocubes are filled into the electrospun polyacrylonitrile (PAN)-based membranes to generate GPE composites with morphological superiority consisting of fine fibers and interconnected pores. The thus obtained PBA@PAN fibrous membrane showcases good thermal stability, high porosity and electrolyte uptake, as well as a peak ionic conductivity of 2.7 mS/cm with the addition of 10% PBA. Consequently, the assembled lithium iron phosphate (LiFePO4) battery using PBA@PAN-10 as the GPE delivers a high capacity of 152.2 mAh/g at 0.2 C and an ultralow capacity decay of 0.09% per cycle in a long-term cycle life of 350 cycles at 1 C, endorsing its promising applications in LPBs.

Superior Ionic Transferring Polymer with Silicon Dioxide Composite Membrane via Phase Inversion Method Designed for High Performance Sodium-Ion Battery

Superior sodium-ion-conducting polymer poly(vinyledene fluoride)–silicon dioxide (PVdF-SiO2) composite separator membrane was prepared via simple phase inversion method, which is a suitable alternative conventional polypropylene membrane. Basically, PVdF is the promising for use as high porous polymer electrolyte membrane due to its high dielectric constant (ε = 8.4). In this work, we prepared a composite membrane using PVdF-SiO2 via phase inversion method. This work was systematically studied towards the morphology, porosity, and electrochemical properties of as prepared membrane. The electrolyte uptake capability of separator membrane tested with 1 M NaPF6 electrolyte solution and temperature-dependent ionic conduction test were performed at various temperatures. This membrane exhibits higher ionic conductivity of 4.7 × 10−2 S cm−1 at room temperature. The physical properties were analyzed by X-ray diffraction, FT-IR, and FE-SEM micrographs analyses. The electrochemical performances with impedance analysis carried for prepared membrane with the as-prepared sodium P2-type cathode material. The material showed an initial discharge capacity of 178 mAh g−1 at 0.1 C between 2 and 4 V with 98% columbic efficiency and 81% capacity retention after 50 cycles upon using the as-prepared PVdF-SiO2 composite separator membrane.

Porous film host-derived 3D composite polymer electrolyte for high-voltage solid state lithium batteries

Conventional lithium-ion batteries with liquid organic electrolytes generally suffer potential security risks concerning volatilization, flammability and explosion. Nonflammable and thin solid-state electrolytes particularly composite solid electrolytes (CSEs) that integrate the merits of different electrolyte systems have attracted increasing attention for advanced lithium batteries with improved energy density and high safety. In this work, a three-dimensional (3D) fiber-network-reinforced CSE, which consists of a mechanically robust, porous polyimide (PI) film as a host, Li6.75La3Zr1.75Ta0.25O12 (LLZTO) nanoparticles and poly (vinylidene fluoride) (PVDF) polymer matrix with bis-trifluoromethanesulfonimide lithium salt as electrolyte filler, is designed and fabricated. Such unique 3D CSE films with PI fiber network holding for uniform dispersion of LLZTO in PVDF show continuous lithium ion transfer pathways and effective prevention for lithium dendrite growth, consequently exhibiting improved mechanical property (high tensile strength of 11.5 ​MPa) and high cyclic stability (more than 1000 ​h of cycling for Li symmetric batteries). Furthermore, solid-state LiNi0.5Co0.2Mn0.3O2/Li pouch cells with the PI-PVDF/LLZTO CSE exhibit excellent cyclic stability (152.6 ​mA ​h ​g−1 with capacity retention of 94.9% at 0.1C after 80 cycles) at room temperature, and high functionality and safety (withstand harsh environments such as folding, cutting and nail penetration) in practical applications.

TiO2 nanoparticle dispersed porous gel polymer electrolyte membrane for room temperature Na-S battery

Room temperature sodium-sulfur (Na-S) batteries are promising energy storage devices for meeting increasing energy demands. An electrolyte with reasonably high ionic conductivity (≥10−4 S cm−1) is one of the key requirements for room temperature Na-S batteries. In this work, a sodium ion conducting flexible porous gel polymer electrolyte membrane of TiO2 (Titanium dioxide) dispersed Poly(vinylidene fluoride-hexafluoropropylene) soaked in a liquid electrolyte of NaPF6 (sodium hexafluorophosphate) in EC (ethylene carbonate): PC (Propylene carbonate) has been prepared. The electrolyte is obtained through phase inversion method and shows an ionic conductivity of 1.3 × 10−3 S cm−1. A proto-type Na-S battery has been fabricated and characterized using the prepared electrolyte membrane. The battery shows an open circuit voltage of ∼2.1 V and discharge capacity of 231 mA h g−1. However, battery shows capacity fading during charge-discharge cycle.

A novel porous gel polymer electrolyte based on poly(acrylonitrile–maleic anhydride) composite by polyhedral oligomeric silsesquioxane for lithium-ion batteries

A novel porous polymer membrane based on polyhedral oligomeric silsesquioxane (POSS) composite poly(acrylonitrile–maleic anhydride) (P(AN–MAH)) is prepared by phase inversion method, and corresponding P(AN–MAH) composite gel polymer electrolyte (GPE) is prepared by further absorbing the liquid electrolyte. The structure of the prepared POSS and P(AN–MAH), and the properties of the composite P(AN–MAH) membranes and GPEs are investigated. The results indicate that the introduction of POSS significantly reduces the crystallinity of P(AN–MAH), which gives the composite membrane and GPE excellent performance. Compared with pure P(AN–MAH)-based membrane and GPE, the composite membrane containing 5 wt% POSS exhibits the best porosity (69.9%) and electrolyte uptake (311.9 wt%), and the most excellent electrochemical performance is also presented by the corresponding GPE: enhanced ionic conductivity of 2.51 × 10−3 S cm−1 at room temperature; better compatibility with electrode; significantly increased lithium-ion transference number of 0.53; a remarkably widened electrochemical stability window of 5.6 V (vs. Li/Li+); a higher discharge specific capacity of 147 mAh g−1 with a Li/GPE-5%/LiFePO4 cell at 0.2 C.

Porous sulfide scaffolded solvent-free PEG-Ti hybrid polymer: All-solution-processed thin film composite polymer electrolytes directly on electrodes for lithium-ion batteries

In this work, thin solid-state electrolyte films composed of porous sulfide film scaffolding solvent-free polyethylene glycol-titanium (PEG-Ti) hybrid polymer electrolyte are directly constructed on the electrodes using a pressing-free all-solution-processed route. Porous Li7P3S11 (LPS) thin films are deposited on the electrodes using doctor blade method with the LPS slurry in which LPS powders are prepared by solution process as well. The porous LPS thin films are further employed as the scaffolds for the infiltration of PEG-Ti hybrid polymer electrolytes to construct the Li-ion composite electrolytes on electrodes. A Li ion conductivity of 1.6 × 10−4 Scm−1 at 25 °C is achieved in the optimized porous LPS-scaffolded solvent-free PEG-Ti composite polymer electrolyte, which is 3-fold enhanced in comparison with the solvent-free PEG-Ti hybrid polymer electrolyte.

A green and facile way to prepare methylcellulose-based porous polymer electrolytes with high lithium-ion conductivity

A novel and green method to prepare porous membrane is reported by simply blending methylcellulose (MC) and lithium polymethacrylic acid (LiPMA) in water. Thanks to the coordination between oxygen atom in MC and Li+ in LiPMA and subsequent micro-phase separation between them, a porous membrane can be obtained after water evaporated. A series of membranes with different pore size and morphology are prepared by controlling the mass ratio of MC/LiPMA. All the membranes exhibit good thermal and electrochemical stability. With the increasing proportion of LiPMA, the obtained membrane has higher electrolyte uptake, resulting in higher ionic conductivity of corresponding gel polymer electrolyte (GPE). When the mass ratio is 5:20, the membrane has the highest the lithium ion transference (0.57), and the GPE reveals the higher ionic conductivity of 0.65 mS cm−1 at room temperature. What's more, the aforementioned GPE exhibits excellent discharge capacity and good cycling performance. Without use of any organic solvents and tedious preparation process, this novel method is environmentally friendly and low-cost, and the obtained GPE exhibits excellent performance, which has a greatly commercial potential.

High-Temperature and All-Solid-State Flexible Supercapacitors with Excellent Long-Term Stability Based on Porous Polybenzimidazole/Functional Ionic Liquid Electrolyte

A high-performance solid-state electrolyte was obtained using porous polybenzimidazole (pPBI) and ionic liquid (IL) (i.e., (1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride). IL is hydrolyzed to form Si-O-Si networks under acidic conditions, which guarantee the enhanced mechanical properties. The porous structure and Si-O-Si networks improve the acid retention capacity and conductivity simultaneously. The prepared porous composite film exhibits a proton conductivity as high as 0.103 S cm-1 at 170 °C. Then, an all-solid-state supercapacitor (ASSC) was assembled using the obtained film electrolyte and activated carbon electrodes. The electrochemical performance was evaluated at different temperatures (30, 60, 90, 120, and 150 °C). The prepared ASSC displayed a specific capacitance of 85.5 F g-1 at 120 °C, which is 3 times higher than that at 30 °C. Meanwhile, the ASSC displayed excellent long-term cycle stability after 10 000 constant current charge and discharge tests, 91.0% capacitance retention, and 95.8% coulomb efficiency. All the results indicate that the porous polymer electrolyte is promising for application in high-temperature energy-storage devices.

Wetting properties of porous high temperature polymer electrolyte fuel cells materials with phosphoric acid.

Wetting properties of phosphoric acid in porous materials of high temperature fuel cells (HT-PEFC), operating at around 160 °C, are important for cell performance and durability, but the underlying wetting parameters have been unknown so far. Therefore, the influence of phosphoric acid temperature and concentration on the wetting behavior of porous HT-PEFC materials is investigated. The acid filling of gas diffusion and catalyst layers as function of capillary pressure is monitored with X-ray tomographic microscopy under the well defined conditions of an ex situ set-up at temperatures up to 160 °C. For the wetting of gas diffusion layers, with pore sizes in the order of few 10 μm, two opposing trends are shown. With increasing phosphoric acid concentration, less capillary pressure is required, while with increasing temperatures, higher capillary pressures are needed for filling up to a given saturation. The same trends are also found for the contact angle of phosphoric acid on PTFE. A higher contact angle is observed with increasing temperature while increasing the phosphoric acid concentration decreases the contact angle. As both trends are of a similar order of magnitude, the wetting behavior of concentrated (113 wt%) phosphoric acid at 160 °C is astonishingly similar to the wetting behavior of water at room temperature. Another important property for HT-PEFC operation is the filling of cracks in the catalyst layer, which have widths up to 100 μm. For large cracks (>60 μm), a capillary pressure of only 15 mbar was deduced from the measurement, increasing to 30 mbar for cracks between 20 and 60 μm. This, for the first time, allows for assessing the membrane phosphoric acid pressure during fuel cell operation. This can guide the development of improved porous materials for HT-PEFC.

Porous nanocomposite gel polymer electrolyte with high ionic conductivity and superior electrolyte retention capability for long-cycle-life flexible zinc–air batteries

Zinc–air batteries (ZABs) with high energy density and low cost have ignited tremendous interest in meeting the ever-growing demands for flexible and portable electronics. As the “blood” of a flexible ZAB, the semi-solid/solid-state electrolyte plays a critical role in the battery performance such as cycling performance, rate characteristics and power output. Herein, a novel porous-structured poly (vinyl alcohol) (PVA)-based nanocomposite gel polymer electrolyte (GPE) with the optimum addition of silica (SiO2) was synthesized and utilized in a bendable sandwich-type ZAB. The fabricated porous PVA-based nanocomposite GPE exhibited a high ionic conductivity (57.3 mS cm–1), excellent water retention capability as well as improved thermal and mechanical properties under ambient condition, with which the assembled flexible ZAB presented excellent cycle stability, discharge performance and power density. Furthermore, the flexible porous PVA–SiO2 based ZAB sets could power a light-emitting diode screen, a handheld electric fan, or even a mobile phone, demonstrating its promising potential for high-performance ZABs with high safety, cost-effectiveness, and excellent flexibility.

A porous cross-linked gel polymer electrolyte separator for lithium-ion batteries prepared by using zinc oxide nanoparticle as a foaming agent and filler

In this work, a new porous cross-linked membrane is prepared and used as the separator for rechargeable lithium-ion batteries. The inorganic zinc oxide nanoparticle (nano-ZnO) was added as a pore-forming agent and filler to the preparation process of membranes composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and a cross-linked polymer by the copolymerization from poly(ethylene glycol methyl ether methacrylate) (PEGMEMA), methyl methacrylate (MMA) and octavinyl-T8-silsesquioxane (OVPOSS). The prepared membrane was firstly swollen by propylene carbonate (PC) and nano-ZnO was then eluted by hydrochloric acid to form the microporous structure. The effects of particle size and additive amount of nano-ZnO on the mechanical and electrochemical properties of microporous membranes were studied. SEM analysis showed that 30 nm nano-ZnO was the most suitable diameter for forming microporous structure. It is generally considered that the ionic conductivity is inversely correlated with the mechanical strength of separator. In our research, we have found that 18% addition of nano-ZnO was the most appropriate amount for the preparation of a microporous membrane (CRZ18) with an ionic conductivity of 1.4 mS cm−1 and a tensile strength of 10.7 MPa. Meanwhile, the LiFePO4/Li half-cell assembled with the CRZ18 membrane as a separator exhibited the best C-rate capacity and cycle charge-discharge performance, indicating that the CRZ18 membrane would be a kind of promising separator for the high-performance lithium-ion batteries.