Polymer Electrolyte Layer Research Articles

Numerical Model for Investigating Effects of Cracks and Perforation on Polymer Electrolyte Fuel Cell Performance

The presence of cracks in the microporous layer (MPL) of polymer electrolyte fuel cells (PEFCs), often occurring during the membrane electrode assembly manufacturing process, has a significant impact on cell performance. However, the exact influence of crack presence, density, and patterns within MPLs on cell performance and transport behaviors remains unclear. This study introduces a three-dimensional macroscale model of PEFCs aimed at investigating the effects of MPL cracks and gas diffusion layer (GDL) perforations on cell performance and transport behavior. This model offers several advantages, including the ability to potentially integrate the effects of flow channel design in future. Additionally, the model can seamlessly incorporate electrochemical reactions and explore phenomena within the catalyst layers (CLs), expanding simulation capabilities beyond water transport alone. The findings suggest that MPL cracks contribute positively to performance by facilitating water drainage. Furthermore, when combined with perforations in GDLs, MPL cracks can significantly enhance performance by providing pathways for water transport. Overall, this study provides valuable insights into developing models for optimizing PEFC performance and underscores the need for further research and development in this area.

Understanding the impact of Li2CO3 distribution within solid electrolyte interphases on lithium metal via thermal conditioning

The formation of a solid electrolyte interphase (SEI) is crucial for the performance and safety of Li metal batteries (LMBs). The SEI consists of various compounds that are assumed to prevent electrolyte decomposition and dendrite growth. Among these constituents, Li2CO3 has a contentious position; some studies stated that it is a beneficial component, whereas others viewed it as an impurity. This study investigated the influence of strategic heat treatments on the distribution of Li2CO3 formed in the SEI of Li metal. These treatments affect the cycling performance of Li/LiCoO2 cells, as evidenced by the differences in cycle life and capacity. In particular, the study showed that samples heat-treated at higher temperatures generally exhibited enhanced performances, illustrating the impact of heat treatment on SEI quality. The quality of the SEI, which depends on the Li2CO3 formation model (solid electrolyte interface layer or a solid polymer electrolyte layer), varies depending on the applied heat treatment. The samples heat-treated at 120 °C followed the solid polymer electrolyte layer model, resulting in the mosaic-style formation of Li2CO3. This intricate pattern provides superior mechanical stability compared with that of a plain layer-type structure and can be used to develop potential strategies for the enhancement of the cycling stability and overall longevity of LMBs.

Liquid Water Visualization in the Pt‐Loading Cathode Catalyst Layers of Polymer Electrolyte Fuel Cells Using Operando Synchrotron X‐ray Radiography

Water management is important for addressing the challenges posed by next‐generation fuel cell electric vehicles. Although X‐ray imaging techniques are useful for probing the mechanism of water transport in the gas diffusion layer of polymer electrolyte fuel cells, they cannot be easily applied to the Pt‐loading catalyst layer because of its low X‐ray transmittance due to the high absorption coefficient of Pt. Herein, a method to realize the high‐resolution X‐ray imaging of a 30 μm‐thick cathode catalyst layer in polymer electrolyte fuel cells using synchrotron X‐ray radiography is proposed, thus bridging the above gap. The results of operando synchrotron X‐ray radiography measurements reveal that water accumulation in the cathode catalyst layer depends on the cell temperature, feed gas humidity, and cell voltage, while time‐slice analysis shows that the water accumulation rate in the cathode catalyst layer immediately after the power generation is faster than that in the cathode gas diffusion layer. The proposed imaging method can be used to evaluate the water storage capacity of the catalyst layer and thus deepen the understanding of flooding phenomena and cold‐start behavior at subzero temperatures.

Solid Electrolytes for Low-Temperature Carbon Dioxide Valorization: A Review.

One of the most promising approaches to address the global challenge of climate change is electrochemical carbon capture and utilization. Solid electrolytes can play a crucial role in establishing a chemical-free pathway for the electrochemical capture of CO2. Furthermore, they can be applied in electrocatalytic CO2 reduction reactions (CO2RR) to increase carbon utilization, produce high-purity liquid chemicals, and advance hybrid electro-biosystems. This review article begins by covering the fundamentals and processes of electrochemical CO2 capture, emphasizing the advantages of utilizing solid electrolytes. Additionally, it highlights recent advancements in the use of the solid polymer electrolyte or solid electrolyte layer for the CO2RR with multiple functions. The review also explores avenues for future research to fully harness the potential of solid electrolytes, including the integration of CO2 capture and the CO2RR and performance assessment under realistic conditions. Finally, this review discusses future opportunities and challenges, aiming to contribute to the establishment of a green and sustainable society through electrochemical CO2 valorization.

Cathode|Electrolyte Interface Engineering by a Hydrogel Polymer Electrolyte for a 3D Porous High-Voltage Cathode Material in a Quasi-Solid-State Zinc Metal Battery by In Situ Polymerization.

This work highlights the development of a superior cathode|electrolyte interface for the quasi solid-state rechargeable zinc metal battery (QSS-RZMB) by a novel hydrogel polymer electrolyte using an ultraviolet (UV) light-assisted in situ polymerization strategy. By integrating the cathode with a thin layer of the hydrogel polymer electrolyte, this technique produces an integrated interface that ensures quick Zn2+ ion conduction. The coexistence of nanowires for direct electron routes and the enhanced electrolyte ion infiltration and diffusion by the 3D porous flower structure with a wide open surface of the Zn-MnO electrode complements the interface formation during the in situ polymerization process. The QSS-RZMB configured with an integrated cathode (i-Zn-MnO) and the hydrogel polymer electrolyte (PHPZ-30) as the separator yields a comparable specific energy density of 214.14Whkg-1 with that of its liquid counterpart (240.38Whkg-1, 0.5MZn(CF3SO3)2 aqueous electrolyte). Other noteworthy features of the presented QSS-RZMB system include its superior cycle life of over 1000 charge-discharge cycles and 85% capacity retention with 99% coulombic efficiency at the current density of 1.0Ag-1, compared to only 60% capacity retention over 500 charge-discharge cycles displayed by the liquid-state system under the same operating conditions.

A novel composite solid electrolyte with ultrahigh ion transference number and stability for solid-state sodium metal batteries

The combination of a Na-ion conducting filler and polymer matrix in composite solid electrolyte (CSE) presents a promising and attractive strategy for improving the energy density and safety of the sodium-metal batteries. The agglomeration and precipitation of inorganic ceramic fillers in the polymer matrix present a major challenge leading to the decreased Na ion conductivity property and transference number, increased interfacial resistance, and worsened mechanical properties of CSEs. Herein, we introduce a novel composite solid electrolyte (denoted as 3D-15PNZSPP), comprising a three-dimensional interconnected porous Na3Zr2Si2PO12 framework integrated with an asymmetric polymer electrolyte layer, which not only offers continuous conductive pathways and high mechanical strength for Na ions transfer, but also enhances the interfacial compatibility and expands the electrochemical stability window. The 3D-15PNZSPP CSE shows a high Na+ conductivity of 7.6 × 10−4 S cm−1 and an outstanding transference number of 0.82 at temperature of 30 °C. These characteristics enable the Na/3D-15PNZSPP/Na symmetric cell to cycle for over 700 h with a small overpotential. More importantly, the assembled all solid-state Na0.67Li0.24Mn0.76O2/3D-15PNZSPP/Na batteries demonstrate remarkable cycling stability and high rate capability, indicating a promising and facile strategy for designing ultra-safe and high-performance solid-state sodium metal batteries.

Exploring the sustainability of serpentine flow-field fuel cell, straight channel PEM fuel cells hight temperature through numerical analysis

This study focuses on investigating the performance dynamics of high-temperature Proton Exchange Membrane fuel cells, with an emphasis on critical design parameters. Utilizing a comprehensive mathematical model, the research explores concentration profiles, current density profiles, and polarization curves within a three-dimensional, isothermal, steady-state PEM fuel cell.The model incorporates the intricate processes of gas transport in anode and cathode channels, diffusion in catalyst layers, and the transport of water and hydronium ions in both the polymer electrolyte and catalyst layers. Additionally, it accounts for electrical current transport in the solid phase. Simulations conducted with Comsol Multiphysics 6.1 demonstrate a robust alignment between model results and experimental polarization data obtained at 180 °C. Optimal conditions for performance are outlined, specifying an inlet hydrogen gas velocity of 0.12 m/s and an inlet air velocity of 1.2 m/s, with consideration for a proton conductivity of 9.825 S/m.In a parallel investigation, numerical analysis assesses the sustainability of Serpentine Flow-Field PEM fuel cells, using critical parameters. The model applied in this research considers gas, water, and electrical current transport across various layers of the fuel cell, with a crucial focus on optimizing the membrane electrode assembly's design. The finite element method and ANSYS Fluent are employed for model solution.This study contributes significantly to the understanding of HT-PEM fuel cell dynamics, providing insights into the interdependencies of design parameters and their impact on system performance. The study emphasizes the pivotal roles of air and hydrogen inlet velocities in shaping fuel cell performance, elucidating the intricate dynamics dictating reactant distributions within diverse cell components.

Electrical and Structural Properties of Poly (Methyl Methacrylate) Doped Potassium Iodide (KI) Solid Polymer Electrolyte

AbstractA high‐conducting salt‐doped polymer electrolyte layer has been created here for use in photocell technologies. The solution casting method is used to produce ion conducting film where poly (methyl methacrylate) (PMMA) is used as the host polymer and potassium iodide (KI) as the dopant. The conductivity and amorphic increases of the polymer electrolytes with the addition of salt concentrations helps in the enhancement of the charge transfer properties. Using electrochemical impedance spectroscopy (EIS), ionic conductivity is evaluated where maximum conductivity is 3.99 × 10−6 S cm‐1 at 20 wt% KI concentration. Polarized optical microscopy (POM) shows the reduction in crystallinity by salt doping, while Fourier transforms infrared spectroscopy (FTIR) shows the complexation as well as composite nature of the film. Ionic transference number (tion) measurement shows the predominantly ionic nature of this polymer electrolyte.

Advances in Reinforced Polymer Electrolyte Membrane Designs for Improved Direct Coated Electrodes

In recent years, hydrogen fuel cells have become a key clean technology for the decarbonization of the transport sector. Significant investments are directed towards scaling the hydrogen infrastructure and the production of fuel cell vehicles to meet cost and climate targets set by governments across the globe. To achieve the required scale at cost, manufacturers of fuel cell components such as membrane electrode assembly (MEA) need to adopt high throughput processes while maintaining quality and performance of MEAs to meet heavy duty vehicle requirements.Roll to roll direct coating (DC) process using slot die coating technique is proposed to deliver the lowest cost/highest throughput method for production of MEAs. Electrode ink containing catalyst, ionomer and solvents are applied directly on the membrane before drying to remove the solvents from the coating. The direct contact of solvents with PEM ionomer can create challenges resulting from ionomer swelling and shrinking to produce poor electrode quality and MEA performance.This talk will discuss different design approaches to produce direct coated MEAs and present a novel approach in membrane design to address DC challenges to meet performance and quality targets that would enable the use of DC for scaling the fuel cell production.Applying Gore’s knowledge in expanded poly-tetra-flour-ethylene (ePTFE) reinforcement properties and fuel cells research we developed a membrane that would reinforce the polymer electrolyte and electrode layers simultaneously while minimizing the impact of solvents used in DC processes. This results in improved MEA quality and performance compared to a traditional reinforced membrane design and enables the use of DC for high throughput/low-cost MEA manufacturing. Figure 1

Solid-State Polymer Battery: Manufacturing Process and Characterization

Solid-state batteries are a promising technology that could provide higher energy density, better safety, longer cycle life and a wider operating temperature range than current commercial LiBs [1] .The solid electrolyte is the main component of all-solid-state batteries. It can be ceramic, glass, polymer, or a mixture. Solid Polymer Electrolyte (SPEs) have received distinctive attention, especially by industry, owing to their potential advantages such as safety, lightweight, high flexibility, and realistic processability. However, despite fast growing interest in solid-state technology, reports on the scalable production of all-solid-state lithium-ion batteries using electrodes with meaningful areal capacities are rather scarce [2] . Moreover, chemical, and mechanical challenges remain. The intimate contact between the electrode and the solid electrolyte is difficult due its non-infiltrative nature. This lack of intimate contact severely limits the cycling properties [3] . The development of effective strategies to alleviate the issue of physical contact is imperative in the engineering of solid-state batteries [4] .In the frame of SAFELiMOVE (Advanced all Solid stAte saFE Lithium Metal technology tOwards Vehicle Electrification) project, we assemble a solid-state pouch based on lithium metal anode, a solid polymer electrolyte layer and a compatible cathode. In work, we report on a reliable fabrication process of large-scale all-solid-state lithium-ion batteries using cathodes prepared by CIDETEC, lithium anode provided by Hydro-Quebec, polymers provided by CICe, inorganic filler provided by SCHOTT and a solid polymer electrolyte manufactured at SAFT.All-solid-state lithium-ion battery pouch cells have been successfully built with consistent electrochemical performance. Cycling that shows the good performance of those cells and the lesson learned regarding their cycling conditions will be presented. [1] J. Motalli, “A solid future Nature, 526, S96 (2015) [2] Ningxin Zhang et al “Scalable preparation of practical 1Ah all-solid-state lithium-ion batteries cells and their abuse tests”, Journal of Energy Storage 59 (2023) 106547 [3] Li et al.“Atomically Intimate Contact between Solid Electrolytes and Electrodes for Li Batteries” Mater 1, 1001-1016, October 2, 2019. [4] Theodosios Famprikis, Pieremanuele Canepa, James A. Dawson, M. Saiful Islam and Christian Masquelier“Fundamentals of inorganic solid-state electrolytes for batteries” Nature Materials-August 2019. Figure 1

A Versatile Strategy for Manufacturing Separator-Free Li-Ion Battery Cells: Combination of Dry Process for Electrodes and Solvent-Based Impregnation of Polymer Electrolytes

A Separator for conventional Lithium-Ion Batteries (LiBs) typically consists of functionalized Polypropylene or Polyethylene to avoid short circuiting and host the liquid electrolyte[1]. The successful removal of the separator would not only facilitate the cell assembly process, but would also reduce the process cost related to z-stacking machines, which corresponds to around 12 % of total process cost[2]. Therefore, a different strategy needs to be applied in this case to prevent short circuits while maintaining sufficient ionic conduction.An often-mentioned strategy to achieve the separator-free architecture is to impregnate and overcoat the electrodes with a polymer electrolyte dissolved in a solvent. However, a meticulous investigation of a compatible combination of binder-polymer electrolyte, conductive salt and solvent is usually necessary to avoid negative impacts of this strategy, with the delamination of the electrodes, the insufficient impregnation of the electrodes or the emergence of high interfacial resistances being only some examples of potential problems which can occur during this process.Here, we present a novel approach to overcome the above-mentioned barriers, by combining different manufacturing techniques. Firstly, in order to avoid the delamination of the electrodes, electrodes with adjustable porosity are prepared by a fully dry process using fibrillated polytetrafluorethylene (PTFE) as a binder. Due to the non-solubility of PTFE in a plethora of different solvents, the choice of solvent is much less limited and a wider range of solvents can be used to tune the viscosity during the impregnation process. Into the porous electrodes, a , dissolved in a solvent, is impregnated via a standard doctor blade-coating method. Furthermore, using dry process electrodes mitigates the impact of inhomogeneous vertical distribution, avoiding self-aggregation in electrodes and forming non-uniform pores[3]. The mentioned flexibility in the choice of solvent type and amount ensures a complete impregnation into the pores of the electrode for different mass loadings and various types of active material. A sufficient thickness of the polymer electrolyte layer during the coating step leads to an overcoating of both electrodes of around 8-10 µm, which is close to the range of commercial separators, enabling practically required high energy densities for battery applications.In our proof-of-concept study, we fabricated and tested LiB cells composed of polymer-impregnated LFP and Graphite electrodes without any separators based on the above mentioned concept. The resulting cells showed promising cyclability and high coulombic efficiencies for more than 100 cycles at intermediate C-rates. The flexibility of the concept is presented by varying the solvent, used during the impregnation step and tailoring the properties of the specialized fluoropolymer electrolyte via addition of ceramic fillers. In addition to the electrochemical performance, an efficient impregnation process of the polymer electrolyte into the porous cathodes, which can be confirmed by SEM, was successfully implemented.In summary, this study provides not only a strategy for the rational design of separator-free architecture, but also creates a novel possibility for solid-state battery applications.[1] Huang, Xiaosong “Separator technologies for lithium-ion batteries”, J Solid State Electrochem 15, 649–662 (2011).[2] Orangi, Stina, et al. “A Techno-Economic Model for Benchmarking the Production Cost of Lithium-Ion Battery Cells”, Batteries, 8, 83, (2022).[3] Kumberg, Jana, et al. "Drying of lithium‐ion battery anodes for use in high‐energy cells: influence of electrode thickness on drying time, adhesion, and crack formation." Energy Technology 7.11 (2019). Figure 1

Fully Printed Electrolyte‐Gated Transistor Formed in a 3D Polymer Reservoir with Laser Printed Drain/Source Electrodes

AbstractIn solution processed electronic devices it is crucial that the deposited inks are properly aligned and that all post‐processing steps are compliant with each other. Moreover, shorter channel lengths are highly beneficial to increase the device performance. Herein, laser printing of metals and polymer reservoirs allows to print sub‐micrometer sized channel lengths while confining functional inks into these small gaps. Therefore, a manufacturing concept and optimized material stack, suitable for combined inkjet and laser printing are proposed. A nanoparticulate indium oxide (In2O3) semiconductor is inkjet printed into and constrained by a 3D laser written polymer (pentaerythritol triacrylate, PETA) reservoir. Inside the 3D printed polymer reservoir, platinum (Pt) electrodes, that are further routed over the reservoir walls, are laser printed by a metal reduction process. The transistor fabrication is completed by a second inkjet printed layer of composite solid polymer electrolyte and an organic top‐gate layer (PEDOT:PSS). This concept does not exceed annealing temperatures higher than 100 °C, and is compatible with a range of substrates. The characterized electrolyte‐gated field‐effect transistor show a reasonable on/off‐ratio in the range of 104 with negligible leakage currents. This materials and hybrid device manufacturing scheme has believed great potential for bioelectronics, lab‐on‐a‐chip applications and others.

All‐Solid‐State Battery Fabricated by 3D Aerosol Jet Printing

All‐solid‐state battery (ASSB) technology has emerged as a promising solution for developing safe and high‐energy‐density power sources. However, the pronounced interfacial charge transfer resistance between the electrode and the solid electrolyte continues to be a central obstacle in contemporary ASSBs. This work demonstrates the first approach to printing ASSBs using aerosol jet printing technology. A composite cathode, composed of active materials, binder polymer, and conductive filler, is printed onto the current collector. Subsequently, a solventless superionic conducting solid polymer electrolyte is printed on the cathode to form a seamless interface between the electrode and the electrolyte, resulting in a 3D‐printed all‐solid‐state lithium‐ion battery. The active material in the cathode (lithium iron phosphate, LFP) achieves a loading of ≈10 mg cm−2, while the solid polymer electrolyte layer maintains a thickness of a mere 24 μm. Under ambient conditions (30 °C), the half‐cell ASSB exhibits a specific capacity of over 130 mAh g−1 at 0.05 C. Advanced aerosol printed cells with a porous membrane, which allows the batteries to be safely cycled at higher temperature (60 °C), exhibit fast charging/discharging rates. These batteries are capable of cycling at a 0.3 C rate, delivering a specific capacity surpassing 160 mAh g−1.

Red-Ox front propagation in polyaniline-polymer electrolyte system as a basis for spiking and rate-based neural networks and multibit ReRAM

We observed and studied the phenomenon of the redox front propagation in different polyaniline (PAni) deposited samples interfaced with liquid or solid polymeric electrolyte. The front of electrochemical conversion, in which the insulator and the conductor parts of PAni are interfaced, is studied observing the temporal evolution of the conductivity of PAni samples. The propagation of redox front was studied in electrochemically obtained thick (2 µm) and in thin (50 nm) polyaniline films, obtained using Langmuir-Blodgett (LB) method. In the configuration that we tested, the speed of the red-ox front propagation for the thin LB films was found to be 200 µm/sec opening the way for the manufacturing large neural networks, realized using PAni based memristive devices, in which the memristance can be quickly changed in the programmable manner. The prototypes of the spiking neuron connections were manufactured on the basis of lithographically developed gold contacts, bridged by electrochemically grown polyaniline and placed under polymer electrolyte layer with only one counter electrode (gate) for the whole manifold of pseudo-two-terminal memristor bridges. The spike propagation was studied in such gold-polyaniline systems. The research opens the possibility of miniature spike or rate-based neural network circuits manufacture, based on metal pads and polyaniline.

Defective Engineering Tuning the Analog Switching Linearity and Symmetry of Two‐Terminal Artificial Synapse for Neuromorphic Systems

AbstractNeuromorphic computing inspired by memristors has gained considerable attention due to its low power and easy integration. However, state‐of‐the‐art two‐terminal resistive switching memristors based on conductive filament formation suffer from high variability and poor controllability. As a three‐terminal device operated through electrochemistry and dynamic insertion/extraction of ions, the electrochemical ion synapse demonstrates deterministic control of electron conductivity based on ion doping. But, integrating the electrochemical ion synapse into crossbar arrays will pose higher challenges and lower integration density. Herein, inspired by first‐principles calculations, a two‐terminal bidirectional plasticity electrochemical artificial synapse with integrated lithium polymer electrolyte and polycrystalline tungsten oxide layer is reported. The linearity and stability of the device weight update are greatly improved by adjusting the defect concentration of the polycrystalline WO3 layer. Even after 16 000 write‐read events in the air, its performance remained almost unchanged. Moreover, it has an over‐limit protection mechanism under one‐way stimulation that exceeds the normal range. Based on this excellent stability, the authors designed and successfully simulated the “muscle memory” that the programmatical organization of the nervous system leads to proficiency in specific actions.

High-Voltage Solid-State Lithium Metal Batteries with Stable Anodic and Cathodic Interfaces by a Laminated Solid Polymer Electrolyte.

Solid polymer electrolyte (SPE) is quite an attractive candidate for constructing high-voltage Li metal batteries (LMBs) with high energy density and excellent safety. However, sim ultaneous achievement of high-voltage stability against the cathode and good compatibility with the Li anode remains challenging for the current SPE technology. Herein, a dual-layered solid electrolyte (DLSE) consisting of an oxidation-resistant poly(acrylonitrile) (PAN) layer facing a high-potential cathode and a reduction-compatible poly(vinylidene fluoride) (PVDF) layer incorporated by Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles and an ionic liquid plasticizer in contact with a Li anode was fabricated. The uniquely designed DLSE holds favorable overall properties in ionic conductivity, Li+ transference number, and mechanical strength. Moreover, the combined advantages of two polymer electrolyte layers greatly address the interface issues on both the cathode and anode. Consequently, the high-voltage LMBs employing the DLSE exhibit excellent room-temperature performances including high rate capacity and long cycle life.

One step hot-pressing method for hybrid Li metal anode of solid-state lithium metal batteries

Safety issues induced by infinite anode volume change and uncontrolled lithium (Li) dendrite growth have become the biggest obstacle to the practical application of Li metal batteries. In addition, the traditional rolling method makes it difficult to manufacture thin Li foil with high mechanical strength and low Li content. Herein, a three-dimensional (3D) lithophilic carbon paper/copper (Cu) current collector hybrid anode with ultra-low Li metal content is prepared by a hot-pressing method. The highly reversible and stable lithiophilic layer LiCx formed in situ by heating/pressing treatment provides abundant nucleation sites and reduces the Li nucleation overpotential, thereby effectively suppressing Li dendrite growth. Moreover, the volume change and pulverization problems of Li metal anode during deposition/stripping also can be accommodated by the 3D skeleton. The optimization effect has been directly confirmed by in-situ optical and ex-situ scanning electron microscope observation. Therefore, highly stable performance (158.4 mA h g−1 at 2 C after 200 cycles with a capacity retention of 95.24%) in Li@LCP-Cu||NCM811 coin cell can be achieved. Furthermore, the solid-state battery assembled with the hybrid anode, poly(vinylidene fluoride) (PVDF)-based polymer electrolyte and polyethylene oxide (PEO) interface functional layer also exhibits the best electrochemical and safety performance, which also proves that the Li@LCP-Cu anode has great potential for application in solid-state batteries.

Polymer Electrolyte/Sulfur Double-Shelled Anisotropic Reduced Graphene Oxide Lamellar Scaffold Enables Stable and High-Loading Cathode for Quasi-Solid-State Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) can replace lithium-ion batteries by delivering a higher specific capacity. However, the areal capacity of current LSBs is low because the intrinsic limitations of sulfur make achieving a high sulfur loading difficult. Herein, the authors report vertically aligned reduced graphene oxide (rGO) with sulfur and poly(ethylene oxide)-based polymer electrolyte double-shell layers (VRG@S@PPE) as a high-loading sulfur cathode. The addition of vapor-grown carbon fiber (VGCF) into rGOis the key to success, as it allows for gas evacuation from internal nano/micropores without structural collapse, enabling perfect double-shell layer contact. Owing to the anisotropic rGO lamellar structure that enables straightforward ion/electron transport and provides numerous active sites, sulfur-infiltrated rGO reinforced via VGCF (VRG@S)exhibits a high capacity of 998 mAh g-1 after 100 cycles at 0.1 C under high sulfur loading (6mg cm-2 ). Interestingly, an additional polymer electrolyte layer further increases the cycle retention (1005 and 718 mAh g-1 after 100 cycles at 0.1 and 1 C, respectively), because intimate contact between the solid polymer electrolyte and sulfur could suppress the loss of sulfur due to lithium polysulfide (LPS) shuttling or volume change during lithiation/delithiation. Therefore, it is possible to realize safe and stable quasi-solid-state LSBs with high sulfur loading.

Dependence of oxygen transport properties of catalyst layers for polymer electrolyte fuel cells on the fabrication process

Herein, we report the oxygen transport phenomenon in the cathode catalyst layer of polymer electrolyte fuel cells. The oxygen transport resistance in the catalyst layer depended on the hot-pressing temperature of the fabrication procedure, suggesting morphological changes in the perfluorosulfonic acid ionomer of the catalyst layers. This work aims to highlight the importance of the manufacturing process in the oxygen transport properties of the catalyst layer.

Solvent Evaporation Rate as a Tool for Tuning the Performance of a Solid Polymer Electrolyte Gas Sensor.

Solid polymer electrolytes show their potential to partially replace conventional electrolytes in electrochemical devices. The solvent evaporation rate represents one of many options for modifying the electrode-electrolyte interface by affecting the structural and electrical properties of polymer electrolytes used in batteries. This paper evaluates the effect of solvent evaporation during the preparation of solid polymer electrolytes on the overall performance of an amperometric gas sensor. A mixture of the polymer host, solvent and an ionic liquid was thermally treated under different evaporation rates to prepare four polymer electrolytes. A carbon nanotube-based working electrode deposited by spray-coating the polymer electrolyte layer allowed the preparation of the electrode-electrolyte interface with different morphologies, which were then investigated using scanning electron microscopy and Raman spectroscopy. All prepared sensors were exposed to nitrogen dioxide concentration of 0-10 ppm, and the current responses and their fluctuations were analyzed. Electrochemical impedance spectroscopy was used to describe the sensor with an equivalent electric circuit. Experimental results showed that a higher solvent evaporation rate leads to lower sensor sensitivity, affects associated parameters (such as the detection/quantification limit) and increases the limit of the maximum current flowing through the sensor, while the other properties (hysteresis, repeatability, response time, recovery time) change insignificantly.