Polymer Electrolyte Research Articles

Nafion-Based Proton Exchange Membranes for Vanadium Redox Flow Batteries.

The sustainable development of future societies depends on advanced energy storage technologies. Vanadium redox flow batteries (VRFBs) are a preferred solution for large-scale, long-duration energy storage due to their high capacity, long lifespan, rapid response, and safety. The proton exchange membrane (PEM) is a pivotal component of VRFBs, playing a crucial role for conducting protons and preventing vanadium ion crossover. Currently, perfluorinated sulfonic acid membranes, represented by Nafion, are the most commonly used PEMs in VRFBs. However, the size discrepancy between vanadium ions (~0.6 nm) and the ionic domains in Nafion membranes (3-5 nm) leads to significant vanadium permeability, resulting in reduced battery performance. Therefore, rationally regulating the structure of Nafion membranes to enhance their conductive selectivity is an urgent issue. This review focuses on recent advancements in Nafion modification, offering valuable insights for inspiring the fundamental innovation of high-selective Nafion membranes for VRFB technology.

Bi-doped NiCo2O4 catalyst for electrocatalysis glucose oxidation accompanied hydrogen generation.

The slow dynamics of oxygen evolution reaction and the use of the proton exchange membrane have been troubling the hydrogen production from electrolytic water splitting. Reducing the electrolytic voltage and avoiding the utilization of proton exchange membranes are crucial targets for electrolytic hydrogen evolution. Bi-doped NiCo2O4 catalyst is prepared and applied in electrocatalysis glucose oxidation coupled hydrogen generation. Structural characterizations confirm the successful preparation of NiCo2O4 and the existence of Bi. Bi leads to the electrons transfer from Co to Ni, increasing the content of Co3+, and lowers the oxidation potential of Co and Ni. Electrochemical experiments indicate that NiCo2O4-Bi has good electrocatalytic activity and stability toward electrochemical glucose oxidation, with a potential of 1.13 V vs. RHE at 10 mA cm-2 current density. The asymmetric electrolysis of two electrodes requires just 1.26 V to achieve a 10 mA cm-2 current density. The design of NiCo2O4-Bi is an exploration for electrocatalytic glucose oxidation coupled hydrogen production with low voltage and no proton exchange membrane.

Ce-Metal Organic Frameworks for Enhanced Chemical Stability and Durability of Sulfonated Polyether Ether Ketone for Proton Exchange Membranes

Ce-Metal Organic Frameworks for Enhanced Chemical Stability and Durability of Sulfonated Polyether Ether Ketone for Proton Exchange Membranes

Enhancing Mass Transport Efficiency in High-Current Density PEMECs by Constructing Ti-Fiber Oriented Porous Transport Layers.

The efficiency of proton exchange membrane electrolysis cells (PEMECs) is much influenced by the dynamics of gas/liquid two-phase flow at the anode side, especially at high current densities. Among different components of PEMECs, the anode porous transport layers (PTLs) are essential for mass transfer optimization. In this work, novel titanium fiber PTLs are designed and fabricated by an angle-selective stacking method. Three oriented PTLs with 30°, 60°, and 90° stacking angles are fabricated and compared with commercial titanium felt. X-ray micro-computed tomography results indicate that the oriented PTLs can avoid dead zones. Electrochemical tests and computational fluid dynamicssimulations demonstrate that the oriented PTLs can enhance oxygen expulsion, and decrease mass transport resistances at high current densities. The PEMEC with the 30° PTL exhibits the best performance, with polarization voltage and mass transport resistance decreased by ≈67mV and 16mΩcm2, respectively, compared to that of the commercial titanium felt at the current density of 3Acm-2. The current work provides a new perspective on enhancing the mass transport efficiency of PTLs by orderly arranging fibers.

High-Elastic Flame-Retardant Polyacrylate-Based Gel Polymer Electrolyte by Dual-Phase Fluorination for Highly Stable Lithium-Metal Batteries.

Lithium-metal batteries (LMBs) are emerging as promising energy storage devices due to their exceptional energy densities. However, uncontrolled lithium dendrite growth and the flammability of liquid electrolytes heavily hinder their widespread applications. To circumvent such issues, we develop a dual-phase fluorinated gel polymer electrolyte (TF-GPE), composed of a fluorinated framework polymerized by 2,2,2-trifluoroethyl acrylate and a fluorinated solvent with fluoroethylene carbonate. The resulting TF-GPE exhibits an impressive tensile elasticity and volumetric accommodations of repeated lithium deposition and stripping up to 4000 h. Additionally, TF-GPE demonstrates excellent flame retardancy by forming a dense fluorine-containing carbon layer. By analyzing the surface of cycled lithium metal, we reveal the formation of elastic solid electrolyte interphase structures with outer organic and inner LiF-rich inorganic layers, enabling stable cycling of 500 cycles with 80.5% capacity retention for solid-state LMBs at 1 C. Our work presents a promising approach to enhancing the stability of LMBs.

Iridium-free High-Entropy Alloy for Acidic Water Oxidation at High Current Densities.

Designing active and cost-effective catalysts for acidic oxygen evolution reaction (OER) is critically important for optimizing proton exchange membrane water electrolyzers used in hydrogen production. In this study, we introduce a straightforward and rapid method to synthesize a quinary high-entropy ruthenium-based alloy (RuMnFeMoCo) for acidic OER. This iridium-free catalyst demonstrates a low overpotential of 170 mV and exceptional stability, enduring a 1000-hour durability test at 10 mA cm-2 in 0.5 M H2SO4. Microstructural analyses and density functional theory (DFT) calculations reveal that the incorporation of corrosion-resistant elements such as Ru, Mo, and Co enhances the overall stability of the catalyst under acidic conditions. Concurrently, the presence of Mn, Fe, and Co significantly reduces the energy barrier of the rate-determining step in the OER process, thus accelerating the OER kinetics and lowering the overpotential. The PEMWE employing the RuMnFeMoCo catalyst operates stably at high current densities of 500 mA cm-2 and 1000 mA cm-2 for over 300 hours with negligible performance degradation. This work illustrates a strategy for designing high-performance OER electrocatalysts by synergistically integrating the benefits of multiple elements, potentially overcoming the activity-stability trade-off typically encountered in the catalyst development.

Efficient and stable acidic oxygen evolution based on W18O49 nanowires supported IrOX.

Proton exchange membrane water electrolyzer (PEMWE) is considered to be a promising green hydrogen production technology but places high demand on the anodic oxygen-evolving electrocatalysts to withstand the strong oxidizing and acidic reaction condition. Here we report a robust W18O49 nanowire supported IrOX (IrOX-W18O49) catalyst for acidic oxygen evolution reaction (OER) prepared by chemical vapor deposition followed with polyol reduction. The catalyst exhibits excellent electrocatalytic OER performance with an overpotential of 223 mV for a current density of 10 mA cm-2 and a small Tafel slope of 66.4 mV dec-1 in acidic media, superior to most electrocatalysts. More impressively, the assembled three-electrode cell with IrOX-W18O49 as the working electrode exhibits excellent electrocatalytic OER performance and can operate stably at 10 mA cm-2 for 140 h. In-situ spectroscopy characterizations reveal that the IrOX-W18O49 works in a route of lattice oxygen mechanism during OER. The favorable interaction between W18O49 nanowires and the IrOX active species together with the strong Ir-O interaction stabilizes the high-valence Ir and prolongs the service life of the catalyst for OER.

Multi‐Objective Optimization of Ionic Polymer Electrolytes for High‐Voltage Fast‐Charging and Versatile Lithium Batteries

AbstractDesigning ionic polymer electrolytes (IPEs) for high‐voltage and fast‐charging lithium batteries involves searching in a highly complex and discrete chemical space. Traditional material discovery processes struggle with this complexity due to high costs and long evaluation time. A kernel‐based Bayesian optimization is described to complete the multi‐objective optimization by considering ionic conductivity, electrochemical stability, and discharge capacity simultaneously. According to a recommender based on a union set of acquisition functions, promising IPEs through three iterations with only 2.8% of the chemical space is targeted. The achieved lithium metal batteries exhibit promising performance with ultrahigh cutoff voltage with NCM811 (LiNi0.8Co0.1Mn0.1O2, 4.8 V) and LNMO (LiNi0.5Mn1.5O4, 4.92 V). To further extend the versatility of IPEs and diminish the high cost associated with the glove‐box environment, an aqueous and high‐voltage lithium‐ion battery is developed by introducing water molecules in IPEs coupled with Li4Ti5O12||LiMn2O4, a strong hydrogen bonding network formed between the rigid‐rod polyelectrolyte and the embedded water molecules, which effectively suppresses the water reactivity, meanwhile boosting the ionic conductivity. This work reveals an innovative multi‐objective optimization that effectively handles multi‐targets and discontinuous parameter space, offering critical insights to address complex challenges in material discovery and property optimization for advanced and versatile lithium batteries.

In Situ Fabricated Non‐Flammable Gel Polymer Electrolyte with Stable Interfacial Compatibility for Safer Lithium‐ion Batteries

AbstractGel polymer electrolytes are viewed as one of the highly ideal substitutes for commercial liquid electrolytes due to their excellent properties of non‐flowing, non‐volatile, high burning point, and compatibility with industrial systems, which collectively contribute to enhanced safety characteristics of batteries. However, the interfacial compatibility issues arising from the unreacted monomers pose significant challenges, leading to poor interfacial compatibility, parasitic reactions, and a subsequent deterioration in battery safety. Herein, a non‐flammable gel polymer electrolyte has been designed by in situ polymerization of Poly (ethylene glycol) diacrylate (PEDGA) with the interfacial reinforcement of Ethoxy (pentafluoro) cyclotriphosphazene (PFPN), to improve the interfacial compatibility and further enhance the safety properties. The gel polymer electrolyte not only forms a stable interface uniformly to resist against the unreactive monomers but also delays the contact reactions and mitigates the chemical crosstalk. The thermal performances with various electrolytes are evaluated comprehensively, and the mechanism for high safety has also been revealed. The incubation time of thermal runaway has been effectively put off from 10.78 to 36.34 h, and the maximum temperature rise (dT/dt) max been reduced in half from 612.0 to 388.2 °C s−1. This work provides an effective strategy for designing efficient polymer electrolytes for high‐safety batteries.

Skeleton Regulation of Covalent–Organic Frameworks From 2D to 3D Networks for High Anhydrous Proton Conduction

AbstractDeveloping new materials for anhydrous proton conduction under high‐temperature conditions is very challenging but significant for proton exchange membrane fuel cells. Herein, a series of highly crystalline and robust covalent–organic frameworks (COFs) with different skeletons (2D and 3D) is designed and synthesized using steric hindrance engineering of the monomer. Moreover, a [4 + 2] construction approach is used to construct 3D COFs with entangled networks, which can be further post‐modified with phosphite acid groups to improve intrinsic proton conduction. After loading with imidazole, COFs can realize a proton conductivity of 1.06 × 10−2 S cm−1 under anhydrous conditions, among the best proton‐conducting COF materials loading imidazole. These materials show high stability at loading and testing conditions and maintain high proton conductivity over a wide temperature range (100–160 °C). This work provides a skeleton regulation approach to design materials for anhydrous proton conduction, showing great potential as high‐temperature proton exchange membranes.

In Situ Cross‐Linking and Interfacial Engineering via Multifunctional Diamine Additive for High‐Temperature Magnesium Metal Batteries

AbstractThe electrolyte and its interfacial chemistry are crucial for the development of high‐temperature magnesium metal batteries. Here, a robust in situ cross‐linked gel polymer electrolyte (MgB@CGPE) and its derived Mg3N2‐rich (Mg3N2 and related Mg─N─H complexes) interphase are obtained by a multifunctional diamine additive. The Mg3N2‐rich interphase exhibits low magnesium ion migration activation energy and can effectively inhibit the continuous decomposition of electrolyte at the interface under elevated temperatures. Moreover, the MgB@CGPE can enable reversible magnesium deposition and dissolution over a wide temperature range of 30–180 °C. The assembled Mo6S8//MgB@CGPE//Mg cells demonstrate stable cycling over 200 cycles at 150 °C with 80% capacity retention. Additionally, these cells also address crucial mechanical and thermal safety concerns, indicating their potential for use under extreme conditions. This work presents a universal and practical strategy for designing polymer electrolytes that operate at elevated temperatures.

Electric‐Dipole Coupling Ion‐Dipole Engineering Induced Rational Solvation‐Desolvation Behavior for Constructing Stable Solid‐State Lithium Metal Batteries

Solid‐state polymer electrolytes (SPEs) with high ionic conductivity, a wide voltage window, and an ultra‐stability electrolyte/electrode interface are essential for practical applications of solid lithium‐metal batteries but particularly challenging. The key to overcoming these long‐term obstacles lies in the rational design of the Li+ solvation‐desolvation behavior in SPEs. Herein, we propose an electric‐dipole coupling ion‐dipole strategy to modulate the Li+ solvation structure and enhance Li+ desolvation kinetics. The experimental characterizations and theoretical calculations indicate that the free solvents and FSI− are anchored by ion‐dipole interactions, which facilitate the transfer of Li+ and obtain a wide electrochemical stability window. Coupling the electric‐dipole interactions that promote lithium salt dissociation and rapid ion desolvation contributes to obtaining more mobile Li+ and realizing an inorganic‐rich electrolyte/electrode interface. Benefiting from the above benefits, the assembled lithium symmetric cells and the full cells demonstrate ultra‐long cycling life. More importantly, full cells with high‐loading cathodes (LiFePO4 with 11.25 mg cm−2, NCM811 with 7.84 mg cm−2) and pouch cell still display stable cycling.This research gives valuable insights into regulating the solvation‐desolvation behavior in SPEs and facilitates the development of state‐of‐the‐art Li metal batteries.

Understanding Anti-Polyelectrolyte Effect in Polyzwitterions Using Coarse-Grained Molecular Dynamics Simulations.

Polyzwitterions (PZs)─polymers bearing both positive and negative charges within each repeating unit─exhibit an unusual antipolyelectrolyte effect where their solubility and viscosity increase upon the addition of salt, contrary to typical polyelectrolytes. As model synthetic analogues of intrinsically disordered proteins, PZs in dilute aqueous solutions are expected to adopt either globular or random coil conformations, with salt addition influencing these structures. We employed coarse-grained Langevin dynamics simulations to investigate how structural parameters─specifically, the spacing between dipolar side chains (d), and the overall polymer chain length (N)─affect the conformational properties of polyzwitterions in salt solutions. Our simulations reveal that added salt leads to nonmonotonic changes in the polymer's radius of gyration, exhibiting both antipolyelectrolyte and polyelectrolyte effects depending on the salt concentration. This behavior is attributed to charge regulation and screening of dipole-dipole interactions by ions. Understanding and controlling the conformations of PZs in aqueous solutions by adjusting salt concentration is of paramount interest for applications in antimicrobial materials, antifouling coatings, drug delivery, membranes, and polymer electrolytes.

Investigation of Charge Transfer Kinetics in Multilayer PEO/LLZO Solid-State Batteries.

Lithium-metal batteries employing solid electrolytes (ceramics or polymers) could surpass the energy and power densities of current state-of-the-art lithium-ion batteries. Unfortunately, ceramic electrolyte/electrode interfaces suffer from poor interfacial contact, and polymer electrolytes show insufficient ionic conductivities for practical uses. Composite solid electrolytes, comprised of mixtures of ceramic and polymer electrolytes, could mitigate these challenges by combining high ionic conductivity with good interfacial contact. However, it is imperative to understand the kinetics of charge transfer at interfaces in composite solid electrolytes, as these can drastically affect the overall ion transport properties of such electrolytes. Here, we design a systematic study of charge transfer kinetics using multilayer LLZO/PEO (tantalum-doped lithium lanthanum zirconium oxide and poly(ethylene oxide)) solid electrolyte architectures as model systems for composite electrolytes. Electrochemical impedance spectroscopy and DC polarization measurements highlight the nonlinear charge transfer kinetics at Li/PEO as well as PEO/LLZO interfaces and show that charge transfer kinetics at each of these interfaces is limited by ion transfer in accordance with a Butler-Volmer model that incorporates a film resistance term. In addition, slow ion transport through the solid electrolyte interphase at Li/PEO interfaces and through contamination layers at LLZO/PEO interfaces are dominant sources of impedance, the latter of which can be significantly mitigated by decreasing interfacial contaminants through a high-temperature (700 °C) heat treatment of LLZO prior to battery assembly. These results provide new insights into the charge transfer kinetics at interfaces in multilayer and composite solid-state batteries and support the future design thereof.

Manipulating Oxygen Reduction Mechanisms of Platinum with Nonmetallic Phosphorus and Metallic Copper Synergistic Alloying

AbstractAlloying of platinum (Pt) nanostructures with heteroelements, commonly including transition‐metals and nonmetals, is an effective strategy to improve the electrocatalytic performance for oxygen reduction reaction (ORR). However, the distinct mechanisms by which metal/nonmetal alloying improves ORR activity remain unclear. Herein, based on the successful alloying of porous network Pt nanospheres (NSs) with metallic copper (Cu) and non‐metallic phosphorus (P) and systematically integrating the electrochemical tests, density functional theory calculations, and in situ electrochemical Raman spectroscopy, this study reveals that the internal Cu‐alloying is responsible for modulating the binding strength of oxygenated intermediates to lower the free energy barrier of the potential‐determining step (PDS) along the ORR associative mechanism, while the further surface P‐alloying can transform the ORR pathway to dissociative mechanism, in which the PDS has a quite low barrier. As a result, the carbon‐supported P/Cu co‐alloyed porous network Pt nanospheres (P‐PtCuNSs/C) catalyst synthesized by confinement growth and post‐phosphorization demonstrates excellent electrocatalytic ORR activity and stability compared to the commercial Pt/C catalyst both in half‐cells and proton exchange membrane fuel cells. In particular, the hydrogen (H2)‐oxygen (O2) single cell with P‐PtCuNSs/C as the cathode catalyst achieves a high mass activity of 0.52 A mgPt−1 at the voltage of 0.90 V, surpassing the U.S. Department of Energy's current activity target.

Core/Shell-Structured Carbon Support Boosting Fuel Cell Durability.

To enhance the lifetime of proton exchange membrane fuel cells, developing highly durable platinum-based cathode catalysts is essential. While two degradation pathways for the cathode catalyst-carbon corrosion and electrocatalyst (platinum nanoparticles) coarsening-have been identified, current approaches to enhance its durability are limited to addressing individual degradation pathways. Herein, the study develops a core/shell-structured carbon support that is designed to afford cathode catalysts capable of simultaneously inhibiting carbon corrosion and electrocatalyst coarsening. The core/shell structure is distinguished by its bifunctional nature: the core is made of highly graphitized carbon tailored to build a robust carbon skeleton, and the shell comprises heteroatom-doped amorphous carbon engineered to prevent electrocatalyst coarsening by chemical/physical anchoring of platinum nanoparticles. Thanks to this elaborate design, the catalyst surpasses the durability targets for carbon supports and electrocatalysts set by the U.S. Department of Energy, as supported by the achieved durability metrics after the square-wave/triangle-wave accelerated stress tests: electrochemical surface area loss at 13%/3%, mass activity loss at 27%/17%, and voltage loss of 29mV (at 0.8 Acm- 2)/4mV (at 1.5 Acm- 2).

Robust p-d Orbital Coupling in PtCoIn@Pt Core-Shell Catalysts for Durable Proton Exchange Membrane Fuel Cells.

Pt-based catalysts are playing increasingly important roles in fuel cells owing to their high catalytic activity. However, harsh electrocatalytic conditions often trigger atomic migration and dissolution in these catalysts, causing rapid performance deterioration. Here, a novel L10-PtCoIn@Pt core-shell catalyst is introduced, where indium (In) is incorporated into a PtCo matrix. This integration promotes p-d orbital coupling, optimizing the electronic structure of Pt and causing additional lattice strain within PtCo. Impressively, L10-PtCoIn@Pt exhibits remarkable activity and durability, with only a 5.1% reduction in mass activity (MA) after 120 000 potential cycles. In H2-O2 fuel cells, this cathode achieves a peak power density of 1.99W cm-2 and maintains a high MA of 0.73 A mgPt -1 at 0.9V. After enduring 60 000 square wave potential cycles, the catalyst maintains its initial MA and sustains the cell voltage at 0.8 A cm-2, exceeding the U.S. Department of Energy (DOE) 2025 targets. Theoretical studies highlight the enhancements originating from the modulated electronic structures and shifted d-band center of Pt induced by In doping and increased vacancy formation energies in Pt and Co atoms, affirming the catalyst's superior durability.

Preparation Technology of Large-sized and Ultra-thin Powder Rolled Porous Titanium Plates for Hydrogen Production from Proton Exchange Membrane Electrolysis Water

Preparation Technology of Large-sized and Ultra-thin Powder Rolled Porous Titanium Plates for Hydrogen Production from Proton Exchange Membrane Electrolysis Water

Solvation Structures in Solid Polymer Electrolytes for Lithium‐Based Batteries

Solvation Structures in Solid Polymer Electrolytes for Lithium‐Based Batteries

Parrot optimizer with multiple search strategies for parameters estimation of proton exchange membrane fuel cells model

Proton exchange membrane fuel cells (PEMFCs) have emerged as a promising renewable energy source, generating significant interest in recent years due to their high efficiency, low operating temperature, and durability. Accurately estimating seven unknown parameters in the PEMFC electrochemical model is crucial for developing a more precise model, thereby improving the efficiency and performance of PEMFC systems. For this reason, a new optimization method inspired by parrots’ (pyrrhura molinaes’) behavior, named Parrot Optimizer (PO), is introduced here to address the problem of optimal parameter identification () in PEMFC models. The estimate of these unknown characteristics is treated as a challenging, nonlinear optimization issue that has to be addressed with a strong optimization technique. The paper outlines two improvements to the basic PO algorithm: the first involves employing Opposition-based Learning to boost the search efficiency and refine candidate solution generation. The second integrates a Local Escaping Operator with PO to boost the exploration capabilities mitigate the risk of getting trapped in local optima, and enhance overall convergence behavior. The IPO was rigorously validated through the application of benchmark functions to assess its performance. Three distinct PEMFC stacks, the NedStackPS6, BCS Stack, and Ballard Mark V, have been used to empirically demonstrate the efficacy of this improved PO in optimizing the PEMFC model. Several recognized modeling approaches from the literature are used in a comprehensive examination to show the method’s efficacy and dependability. For the NedStackPS6, BCS Stack, and Ballard Mark V units, the corresponding SQE values are 2.065816 V, 0.012457 V, and 0.814325 V. The IPO demonstrates a 12.87% improvement in the best measure and an 88.37% reduction in standard deviation compared to PO. The results show that the designed approach, including sensitivity analysis, correctly characterizes the PEMFC model. The improved PO effectively achieves the lowest SQE values and consistent convergence trajectories.