Polymer Electrolyte Research Articles

Structural, electrical, and transport properties of a PVB: NH4Br complexed solid polymer electrolyte films for electrochemical cell applications

ABSTRACT Polymer electrolytes are a key development in advancing battery technology, enabling more efficient energy storage. This study focused on developing a solid-state polymer electrolyte film by doping NH4Br with Polyvinyl Butyral (PVB) using a solution-cast method. X-ray diffraction (XRD) was employed to evaluate the amorphousness and crystallinity of the films, while Fourier Transform Infrared Spectroscopy (FTIR) confirmed complex formation between the salt and polymer. The glass transition temperature (Tg) of the electrolyte film was estimated using Differential Scanning Calorimetry (DSC). Ionic conductivity was measured through AC impedance spectroscopy, revealing that the PVB-NH4Br electrolyte doped with 30 wt% NH4Br at 30 °C had an ionic conductivity of 1.47 × 10−7 S cm−1. This conductivity followed an Arrhenius relationship, where conductivity increased with temperature. Dielectric studies showed that at low frequencies, the dielectric constant and loss were higher, while both decreased at higher frequencies. DC Wagner’s polarization technique verified that ion transport was the dominant conduction mechanism. Discharge testing of the electrolyte film using a Swagelok cell showed an open-circuit voltage (OCV) of 1.2 V and a short-circuit current (SCC) of 0.42 mA, indicating promising performance for battery applications.

MXene Triggered Free Radical Polymerization in Minutes toward All-Printed Zn-Ion Hybrid Capacitors and Beyond.

Additive manufacturing of (quasi-) solid-state (QSS) electrochemical energy storage devices (EES) highlights the significance of gel polymer electrolytes (GPEs) design. Creating well-bonded electrode-GPEs interfaces in the electrode percolative network via printing leads to large-scale production of customized EES with boosted electrochemical performance but has proven to be quite challenging. Herein, we report on a versatile, universal and scalable approach to engineer a controllable, seamless electrode-GPEs interface via free radical polymerization (FRP) triggered by MXene at room temperature. Importantly, MXene reduces the dissociation enthalpy of persulfate initiators and significantly shortens the induction period accelerated by SO- 4·, enabling the completion of FRP within minutes. The as-formed well-bonded electrode-GPEs interface homogenizes the electrical and concentration fields (i.e., Zn2+), therefore suppressing the dendrites formation, which translates to long-term cycling (50,000 times), high energy density (105.5 Wh kg-1) and power density (9231 W kg-1) coupled with excellent stability upon deformation in the zinc-ion hybrid capacitors (ZHCs). Moreover, the critical switch of the rheological behaviours of the polymer electrolyte (as aqueous inks in still state and become solids once triggered by MXene) perfectly ensures the direct all-printing of electrodes and GPEs with well-bonded interface in between, opening vast possibilities for all-printed QSS EES beyond ZHCs.

Charge Scaling in Classical Force Fields for Lithium Ions in Polymers.

Polymer electrolytes are of interest for applications in energy storage. Molecular simulations of ion transport in polymer electrolytes have been widely used to study the conductivity in these materials. Such simulations have generally relied on classical force fields. A peculiar feature of such force fields has been that in the particular case of lithium ions (Li+), their charge must be scaled down by approximately 20% to achieve agreement with experimental measurements of ion diffusivity. In this work, we present first-principles calculations that serve to justify the charge-scaling factor and van der Waals interaction parameters for Li+ diffusion in poly(ethylene glycol) (PEO) with bistriflimide (TFSI-) counterions. Our results indicate that a scaling factor of 0.79 provides good agreement with DFT calculations over a relatively wide range of Li+ concentrations and temperatures, consistent with past reports where that factor was adjusted by trial and error. We also show that such a scaling factor leads to diffusivities that are in quantitative agreement with experimental measurements.

Breaking the Bottleneck of Activity and Stability of RuO2-Based Electrocatalysts for Acidic Oxygen Evolution.

Electrochemical acidic oxygen evolution reaction (OER) is an important part for water electrolysis utilizing a proton exchange membrane (PEM) apparatus for industrial H2 production. RuO2 has garnered considerable attention as a potential acidic OER electrocatalyst. However, the overoxidation of Ru active sites under high potential conditions is usually harmful for activity and stability, thereby posing a challenge for large-scale commercialization, which needs effective strategies to circumvent the leaching of Ru and further activate Ru sites. Herein, a Mini-Review is presented to summarize the recent developments regarding the activation and stabilization of the Ru active sites and lattice oxygen through the modulation of the d-band center, coordination environment, bridged heteroatoms, and vacancy engineering, as well as structural protection strategies and reaction pathway optimization to promote the acidic OER activity and stability of RuO2-based electrocatalysts. This Mini-Review offers a profound understanding of the design of RuO2-based electrocatalysts with greatly enhanced acidic OER performances.

Be aware of the effect of electrode activation and morphology on its performance in gas diffusion electrode setups

The superior performance enhancement in catalyst research for proton exchange membrane fuel cells (PEMFC) revealed in the model rotating disc electrode (RDE) environment is rarely demonstrated in membrane electrode assemblies (MEA). The discrepancy is typically attributed to the difference in the chemical structure and morphology of the catalyst layer (CL), affecting the transport of reactants of the oxygen reduction reaction (ORR). In this study, the gas diffusion electrode (GDE) half-cell setup is used to focus on crucial aspects of CL development, especially on the activation and morphology of CLs, to gain a fundamental understanding of the development of PEMFCs. Adjusting the CL porosity by using different solvent compositions of water and isopropyl alcohol and implementing an activation method for low platinum content catalysts, we focus on understanding the contributions of macro-porosity and hydrophobicity in a liquid electrolyte-based system. We show that macro-porosity significantly influences the O2 mass transport in the CL, demonstrating increased performance with higher porosities. Coupling inductively coupled plasma mass spectrometry (ICP-MS) with the GDE half-cell setup, we propose a method for qualitative estimation of water content in the CL. Lower macro-porosity shows higher platinum dissolution, attributed to improved mass transport of dissolved ions in aqueous media.

Isolated Octahedral Pt-Induced Electron Transfer to Ultralow-Content Ruthenium-Doped Spinel Co3O4 for Enhanced Acidic Overall Water Splitting.

The development of a highly active and stable oxygen evolution reaction (OER) electrocatalyst is desirable for sustainable and efficient hydrogen production via proton exchange membrane water electrolysis (PEMWE) powered by renewable electricity yet challenging. Herein, we report a robust Pt/Ru-codoped spinel cobalt oxide (PtRu-Co3O4) electrocatalyst with an ultralow precious metal loading for acidic overall water splitting. PtRu-Co3O4 exhibits excellent catalytic activity (1.63 V at 100 mA cm-2) and outstanding stability without significant performance degradation for 100 h operation. Experimental analysis and theoretical calculations indicate that Pt doping can induce electron transfer to Ru-doped Co3O4, optimize the absorption energy of oxygen intermediates, and stabilize metal-oxygen bonds, thus enhancing the catalytic performance through an adsorbate-evolving mechanism. As a consequence, the PEM electrolyzer featuring PtRu-Co3O4 catalyst with low precious metal mass loading of 0.23 mg cm-2 can drive a current density of 1.0 A cm-2 at 1.83 V, revealing great promise for the application of noniridium-based catalysts with low contents of precious metal for hydrogen production.

Functionalized Modified Ti4O7 Polyaniline Coating for 316SS Bipolar Plate in Proton-Exchange Membrane Fuel Cells

Functionalized Modified Ti4O7 Polyaniline Coating for 316SS Bipolar Plate in Proton-Exchange Membrane Fuel Cells

Synergistic Enhancement of Biaxial Stretching and Multilayer Composites in All-Solid-State Polymer Electrolytes.

As an important component of lithium-ion batteries, all-solid-state electrolytes should possess high ionic conductivity, excellent flexibility, and relatively high mechanical strength. All-solid-state polymer electrolytes (ASSPEs) based on polymers seem to be able to meet these requirements. However, pure ASSPEs have relatively low ionic conductivity, and the addition of inorganic fillers such as lithium salts will reduce their flexibility and mechanical strength. To address the above issues, in this paper, the solvent-free method was used to prepare a poly(vinylidenefluoride-co-hexafluoropropylene)/lithium bis(trifluoromethanesulfonyl) imide/poly(ethylene oxide) all-solid-state polymer electrolyte, which was then subjected to 4 × 4 magnification synchronous bidirectional stretching. Subsequently, it was multilayered with PEO-based composite polymer electrolytes to obtain multilayered composite polymer electrolytes (MCPEs). Bidirectional stretching provides superior in-plane and out-of-plane mechanical properties to MCPEs by inducing molecular chain orientation, which suppresses the growth of lithium dendrites. Concurrently, it facilitates the formation of the β-crystal form of PVDF-HFP, thereby weakening the ion solvation effect and reducing the lithium-ion migration energy barrier. Multilayered compounding improves the interfacial contact between MCPEs and electrodes, thereby reducing the interfacial impedance. Experiments have demonstrated that the MCPEs prepared in this paper exhibit high ionic conductivity at room temperature (1.83 × 10-4 S cm-1), low interfacial resistance (547 Ω cm-2), excellent mechanical properties (26 MPa), and excellent cycling rate performance (a capacity retention rate of 90% after 110 cycles at 0.1 C), which can meet the performance requirements of lithium-ion batteries for ASSPEs.

A novel radial air-breathing proton exchange membrane fuel cell for miniaturized applications with effective stacking potentials

Increasing volumetric power density in fuel cells can be accomplished by increasing its compactness or output power. This is very crucial for miniaturized applications due to constraints in available spaces. In this study, a three-dimensional, multiphase, and non-isothermal computational fluid dynamics (CFD) tool is used to develop a novel radial air-breathing (AB) PEM fuel cell for miniaturized applications, which has unique stack-ability feature. The noted cell can accommodate multiply higher active area in cathode electrode with respect to planar and tubular AB designs. Increasing the cathode side active area, the electrode with the highest sources of losses for the kinetics of reactions in proton exchange membrane (PEM) fuel cells, has shown to play a significant role in performance enhancement of radial AB cells. For instance, at 0.4 Acm−2 the radial AB PEM fuel cell, can deliver 27.9 % and 10 % more power than the earlier planar and tubular AB ones, respectively. The stack-ability of AB fuel cells usually face severe challenges due to non-uniform air supply to the cells, resulting in imbalance of the cells output power. As opposed to tubular and planar AB cells, one unique feature for the present radial AB stack design is its attack-ability that ensures adequate and uniform supply of air/oxygen to all cells.

Sulfonating and polyhedral oligomeric silsesquioxane crosslinking in one step to build multiple proton pathways for proton exchange membrane fuel cells over a wide temperature range

Developing proton exchange membrane fuel cells (PEMFCs) operating over a wide temperature range can avoid additional internal/external heating or cooling devices for the PEMFCs operating. Polybenzimidazole (PBI) doped with phosphoric acid (PA) exhibits significant potential in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Nevertheless, the traditional PA-PBI membranes are limited to operating within 140∼180 °C. In this work, a sulfonated polyhedral oligomeric silsesquioxane crosslinked polybenzimidazole membrane enriched pyridine and diazafluorene (CSPBI-X) is prepared where the sulfonation and crosslinking are accomplished by one-step heating. The theoretical calculations confirm that PA molecules have strong interactions with sulfonic acid groups and nitrogen-containing groups, enabling the membrane to achieve proton conductivity in a wide temperature range (80–180 °C). Moreover, the cross-linked sulfonated membranes have excellent PA retention ratio as high as 83.8% under 80 °C and 40% relative humidity for 120 h. Remarkably, with the acid doping level of 7.6, the proton conductivity of the CSPBI-20 membrane reaches 0.0491 S cm−1 and 0.145 S cm−1 at 80 °C and 180 °C in dry state, respectively. The highest power density of the CSPBI-20 at 80, 100, 120, 140, 160, and 180 °C is 257.3, 362.9, 485.3, 604.6, 755.3, and 956.1 mW cm−2, respectively.

A fuel cell performance simulation method based on pore-scale gas diffusion layer models obtained from X-ray computed tomography under different assembly pressures

The assembly pressure significantly influences the performance of proton exchange membrane fuel cells. In earlier studies, performance simulations based on volume-averaged formulae tended to smooth out the inherent non-uniformity of the gas diffusion layer (GDL) and this needs to be improved. In this study, an innovative simulation method is proposed for high-temperature proton exchange membrane fuel cells (HT-PEMFCs), which can directly couple pore-scale GDLs with fuel cells when examining fuel cell performance. We used X-ray CT to reconstruct a carbon fiber paper sample (TGP-H-060) under different pressures. These reconstructions were then directly coupled with volume-averaged components to form multiscale models of HT-PEMFCs. Governing equations of mass, momentum, species and charge were directly solved in the microstructure and fluid channels to obtain the polarization curve of the HT-PEMFC. The proposed model combines studies of fuel cell performance with evaluation of the properties of pore-scale GDLs. The results show that using the proposed method, not only can the influence of assembly pressure on the overall performance (i.e. polarization curves) of fuel cells be obtained, but also the influence of assembly pressure on the gas distribution in pore-scale channels of GDLs can be clearly revealed, which can guide the optimization of GDL structure.

A novel sensor preference method for proton exchange membrane fuel cell flooding fault diagnosis based on multi-algorithm

ABSTRACT During periods of high-power operation, proton exchange membrane fuel cell (PEMFC) produce water, which gradually accumulates at the cathode. It causes flooding faults and significantly impacts on PEMFC safety. The data collected by the sensors is a fundamental prerequisite for the flooding faults diagnosis in PEMFC. Consequently, it is critical to select sensors. However, the conventional methods for selecting sensors consider sensitivity and noise immunity, the number of sensors selected and the flood diagnostic performance are not optimized. To solve the above problems, this paper proposes a sensor preference method that combines the Mantel test and Spearman coefficient (MS method). This method first uses the Mantel test to analyze the correlation between two flooding evaluation indicators and the sensors, it identifies suitable sensors for diagnosing flooding faults. Subsequently, the Spearman coefficient eliminates redundant sensors. Additionally, a one-dimensional convolutional neural network is employed to construct a flooding diagnosis model. The MS method is contrasted with two traditional sensor selection methods. The results show that the MS method selected sensors yield superior model training and enhanced accuracy in diagnosing flooding, thereby ensuring PEMFC safety.

3D carbon corrosion kinetic mechanism modeling study for proton exchange membrane fuel cells under localized flooding

Localized anode flooding often occurs in proton exchange membrane fuel cells (PEMFCs) during operation, which leads to localized H2 deficiency and triggers the carbon support corrosion in the catalyst layer, thus seriously weakening the performance and service life of PEMFCs. In this work, a 3D carbon corrosion kinetic mechanism model under localized anode flooding is developed to analyze in detail the multi-physics field distributions during carbon corrosion. The developed model is also coupled with a PEMFC performance model to focus on the carbon corrosion rate spatial distribution and its effect on the PEMFC performance. In addition, the effect of the cathode catalyst layer (CCL) added with oxygen evolution reaction (OER) catalyst on the carbon corrosion rate is analyzed in detail. Considering the particularly expensive OER catalysts and the non-uniform carbon corrosion distribution, a scheme of multi-area ordered adding with OER catalysts is further proposed to reduce the OER catalyst loading, and it is found that such a scheme can more effectively reduce the non-uniform carbon corrosion within the CCL. The electrochemical surface area loss is reduced by 7.38 % and the performance is improved by 5.69 % with scheme 2 compared to without the addition of OER catalyst.

Direct-Coupled Improvement of a Solar-Powered Proton Exchange Membrane Electrolyzer by a Reconfigurable Source

Direct-Coupled Improvement of a Solar-Powered Proton Exchange Membrane Electrolyzer by a Reconfigurable Source

Unveiling the Composition-Dependent Catalytic Mechanism of Pt-Ni Alloys for Oxygen Reduction: A First-Principles Study.

Unveiling the composition-dependent catalytic mechanism of Pt-based alloy cathodes for the oxygen reduction reaction (ORR) helps improve the proton exchange membrane fuel cells. Using density functional theory calculations, this study investigates the ORR catalytic performance of the Pt-Ni system with various compositions (1.00, ∼0.99, 0.75, 0.50, 0.25, ∼0.01, and 0.00). The ordered solid solution PtNi3(111) system shows activity comparable to Pt(111) and is cost-effective. The Ni1/Pt(111) system, featuring a single Ni atom on the Pt(111) surface as a surface single-atom alloy (SSAA), demonstrates the highest activity with an overpotential of only 0.28, which could be further reduced to 0.21 V by decreasing the surface Ni concentration to 1/16 monolayer coverage. The predicted high activity of Ni1/Pt(111) is confirmed when considering factors such as the implicit solution environment, constant potential conditions, and protonation capability. Moreover, surface-adsorbed oxygen species driven by reaction conditions stabilize these single Ni atoms of Ni1/Pt(111) by preventing segregation and dissolution processes, thereby exhibiting a dual functionality. This study reveals the composition dependence of Pt-based alloys and highlights the stability mechanisms of SSAA catalysts during the ORR.

Acid-Doping Induced Phase Separation for Shaping Phase Morphology and Enhancing Performance of Polymer Electrolyte Membranes

Acid-Doping Induced Phase Separation for Shaping Phase Morphology and Enhancing Performance of Polymer Electrolyte Membranes

Supramolecular Association of a Block Copolymer via Strong Hydrogen Bonding to Form Self-Healable Ionogels.

The drive to enhance the operational durability and reliability of stretchable and wearable electronic and electrochemical devices has led to the exploration of self-healing materials that can recover from both physical and functional failures. In the present study, we fabricated a self-healable solid polymer electrolyte, referred to as an ionogel, using reversible hydrogen bonding between the ureidopyrimidone units of a block copolymer (BCP) network swollen in an ionic liquid (IL). The BCP consisted of poly(styrene-b-(methyl acrylate-r-ureidopyrimidone methacrylate)) [poly(S-b-(MA-r-UPyMA)], with the IL-phobic polystyrene forming micellar cores that were interconnected via intercorona hydrogen bonding between the ureidopyrimidone units. By precisely regulating the molecular weight and the composition of the hydrogen-bondable motifs, the mechanical, electrical, and self-healing characteristics of the ionogel were systematically evaluated. The resulting ionogel samples exhibited suitable stretchability, ionic conductivity, and room-temperature self-healability due to reversible hydrogen bonding. To highlight the applicability of the self-healing ionogel as a high-capacitance gate insulator, an electrolyte-gated transistor (EGT) was fabricated using a poly(3-hexylthiophene-2,5-diyl) semiconductor, and the performance of the EGT was fully recovered from a complete cut without any external stimuli.

Superior initiator reactivity and electrochemical properties of In(OTf)3 over Sn(OTf)2 for 1,3-dioxolane based solid polymer electrolyte

The in-situ polymerization of 1,3-dioxolane (PDOL) in battery cells has attracted extensive attention, however, the differences of Lewis acid initiators on the DOL monomer conversion (C%) and electrochemical properties has been ignored. Here, it is demonstrated that compare with Sn(OTf)2 Lewis acid initiator, the gelation of DOL is achieved at the lower addition of In(OTf)3. By optimizing their content in the gelation process, their C% are comparable which are 95.7 % and 93.5 % for In(OTf)3 and Sn(OTf)2, respectively. However, the higher ionic conductivity (7.1 × 10−4 S cm−1 at room temperature), electrochemical window (~4.5 V) and Li+ transference number (0.42) are obtained for DOL initiated with In(OTf)3, due to its lower molecular weight which is helpful to the intermolecular Li+ transport along PDOL main chain; In addition, the Li/Li symmetrical cell of In(OTf)3 can be stably cycled for >500 h at 3 mA cm−2, with an over-potential of 178mv. The storage and cycling impedances of half cells further proves the stable interface of In(OTf)3 initiated DOL toward to lithium metal in comparison with those of Sn(OTf)2. Scanning electron microscopy results show a denser and thinner interface in the DOL catalyzed by In(OTf)3. Finally, the assembled Li/LiFePO4 battery delivers specific discharge capacity and capacity retention rates of 115.5mAh g−1 and 85 %, respectively after 300 cycles at 1C. Through the initiator selection, the DOL synthesis and electrochemical properties can be tuned, which further broadens the design idea of PDOL based solid polymer electrolyte.

Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Gel Polymer Electrolyte Modified with Multi-Walled Carbon Nanotubes and SiO2 Nanospheres to Increase Rechargeability of Zn–Air Batteries

Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Gel Polymer Electrolyte Modified with Multi-Walled Carbon Nanotubes and SiO2 Nanospheres to Increase Rechargeability of Zn–Air Batteries

Thermal Analysis of the Gelation Process of Li-ion Battery Polymer Electrolyte by Electron Irradiation Using Multi-physics Simulation

Thermal Analysis of the Gelation Process of Li-ion Battery Polymer Electrolyte by Electron Irradiation Using Multi-physics Simulation