Solid Polymer Electrolyte Membrane Research Articles

3D printing zwitter Molecule‐Enhanced Solid Polymer Electrolytes for High‐Energy Lithium Metal Batteries

AbstractUnsatisfying preparation controllability, mechanical properties, ionic conductivities, and working voltage windows limit the practical applications of solid polymer electrolytes (SPEs) in lithium‐metal batteries. Herein, a 3D printing strategy combined with zwitter molecule modification is proposed to efficiently solve the problems of SPEs with a polyvinylidene fluoride‐hexafluoropropylene (PH) matrix. The electron‐donating property resulting from the carboxyl groups of aspartate acid (Asp) induces the cis‐conformation change of polyvinylidene fluoride, which enhances the Li+ transport and anion immobilization on polymer chains. In addition, the amphoteric functional groups of Asp simultaneously promote the lithium salt dissociation and Li+ desolvation with N,N‐dimethylformamide, thus leading to the formation of stable Li3N/LiF‐enriched interphases between electrodes and electrolyte. Moreover, the 3D printing technology increases the continuity and uniformity of the SPE membrane, further increasing the ionic conductivity and mechanical properties. As a result, the SPE exhibits high ionic conductivity (1.20 × 10−4 S cm−1), large transfer number (0.68), wide electrochemical window (4.6 V), and good tensile strength (≈110 MPa), endowing the half cells with good cycling performance over 2000 h with a low overpotential of 40 mV. Furthermore, high‐energy densities (492 Wh kg−1 and 1303 Wh L−1) are delivered by a pouch cell with the SPE, indicating good application prospects.

Electrochemical Performance of Guanidinium Salt-Added PVP/PEO Solid Polymer Electrolyte with Superior Power Density.

Solid polymer electrolytes (SPEs) for symmetrical supercapacitors are proposed herein with activated carbon as electrodes and optimized solid polymer electrolyte membranes, which serve as the separators and electrolytes. We propose the design of a low-cost solid polymer electrolyte consisting of guanidinium nitrate (GuN) and poly(ethylene oxide) (PEO) with poly(vinylpyrrolidone) (PVP). Using the solution casting approach, blended polymer electrolytes with varying GuN weight percentage ratios of PVP and PEO are prepared. On the blended polymer electrolytes, structural, morphological, vibrational, and ionic conductivity are investigated. The solid polymer electrolytes' morphology and level of roughness are examined using an FESEM. The interlinking bond formation between the blended polymers and the GuN salt is verified by FTIR measurements, indicating that the ligands are chemically complex. We found that, up to 20 wt.% GuN, the conductivity value increased (1.84 × 10-6 S/cm) with an increase in mobile charge carriers. Notably, the optimized PVP/PEO/20 wt.% solid polymer electrolyte was fabricated into a solid-state symmetrical supercapacitor device, which delivered a potential window of 0 to 2 V, a superior energy density of 3.88 Wh kg-1, and a power density of 1132 W kg-1.

Polyethylene Functionalized with Imidazolium and Pyridinium Moieties through Radiation‐Induced Grafting for Alkaline Solid Polymer Electrolyte Membranes

AbstractHydrocarbon‐based polymer electrolytes hold great promise for practical electrochemical device deployment but suffer from limitations such as ionic conductivity, alkaline stability, and hydrophobicity. This work reports a new membrane, LLDPE‐g‐1VIm/4VP, prepared by radiation grafting a binary mixture of 1‐vinyl imidazole and 4‐vinylpyridine onto linear low‐density polyethylene. Short branches in LLDPE are hypothesized to regulate water uptake, thus improving dimensional stability. Under optimized conditions, the membrane exhibits a relatively high ionic conductivity of 39.86 mS cm−1 at 70 °C, good mechanical strength, improved dimensional stability, and moderate alkaline stability even after 240 h at 60 °C under harsh conditions. Preliminary evaluations demonstrate their potential as solid polymer electrolytes for electrochemical energy applications, including alkaline anion exchange membrane fuel cells.

Electro-Epoxidation of Propylene in the Gas Phase with Solid-Polymer-Electrolyte Water Electrolysis.

The development of a reaction system for direct epoxidation of propylene is an essential topic. Gas-phase electro-epoxidation of propylene to propylene oxide (PO) with water as the oxidant was successfully accomplished by using solid-polymer-electrolyte (SPE) electrolysis without solvents. The oxidized surface of the PtOx anode was essential for propylene epoxidation and oxidation. It was revealed that PO was sequentially oxidized and accumulated on the anode by the interval electrolysis experiment. The formation rate and Faraday efficiency (FE) to PO were improved by applying mild hot-press conditions for the SPE unit because the active phase of the oxide surface of PtOx was maintained and diffusibility of water in the SPE (Nafion) membrane was improved. The FEs to PO are low in this work, but this system is halogen-free.

Molecular Vibration and Physicochemical Performance of Proton-Conducting Solid Polymer Electrolyte Membrane based on CMC/PVA/CH3COONH4

This work studied examined the influence of ammonium acetate (CH3COONH4) on CMC/PVA-based solid polymer electrolyte (SPE) membranes, focusing on molecular vibration, proton conductivity, and physicochemical properties. SPE membranes were prepared via the casting solution method with varying CH3COONH4 concentrations to determine the optimal proton conductivity. Various characterizations, including FTIR, EIS, XRD, and TGA, were performed. The optimal membrane condition was achieved with 10 wt-% CH3COONH4 in the CMC/PVA (80/20) blend, yielding proton conductivity of 3.93×10⁻⁴ S/cm and favorable mechanical, thermal, and crystallinity properties, making it suitable for proton-conducting polymer applications. Keywords: ammonium acetate, carboxymethyl cellulose, ionic conductivity, poly(vinyl alcohol), proton battery, solid electrolyte membrane

Protective Double-Layer Composed of Solid Polymer Electrolyte and Lithiophilic Membrane for Electrodepositing Li Metal

Lithium metal batteries using lithium metal as an anode are considered promising energy storage systems due to their high energy density. In this respect, it is essential to manufacture ultra-thin and scalable lithium metal electrodes. Electrodeposition is an efficient method for fabricating thin Li metal electrodes by controlling the current density. However, the dendritic growth and side reactions during the electrodeposition process at high current density remain as obstacles. In this study, we designed a protective double-layer on a current collector composed of solid polymer electrolyte and lithiophilic membrane. The ion-conductive solid polymer electrolyte attached to the current collector suppressed the side reactions on lithium metal and stabilized the surface. The lithiophilic membrane induced uniform Li-ion flux and exhibited high mechanical strength sufficient to substitute a separator. The lithium metal anode was prepared by electrodeposition using a protective double-layer on a current at high current density of 12 mA cm-2, and the deposited lithium electrode was used as an anode when assembling a coin-type lithium metal battery. The lithium metal battery employing deposited lithium metal anode with a protective layer and LiFePO4 cathode was assembled, and its cycling performance was evaluated.

Analysis of Two-Phase Flow within Porous Structures of Water Electrolysis Cells and Structural Correlation Evaluation

In recent years, issues such as environmental pollution and global warming caused using fossil fuels have become increasingly serious, prompting attention to hydrogen derived from renewable energy sources as an energy source. Among the various hydrogen production technologies, attention has recently been drawn to Proton Exchange Membrane Water Electrolyzers (PEMWEs) utilizing solid polymer electrolyte membranes. The advantages of these PEMWEs include rapid response to irregular power supply from renewable energy sources, low environmental impact with no byproducts such as greenhouse gases, and the ability to select from various usage scenarios and operating environments due to their compact and lightweight design. In PEMWEs, a porous transport layer (PTL) is inserted on the catalyst layer to facilitate the removal of generated bubbles. With the improvement in the performance of solid polymer membranes, an increase in concentration overpotential attributed to gas-liquid transport in the PTL has been reported[1]. Accurately analyzing gas-liquid behavior within the porous structure poses challenges. In this study, we investigated the causal relationship between the three-dimensional structure of the porous material and gas-liquid transport properties using computational methods.To simulate gas-liquid transport within the porous media, a Pore Network Model (PNM) is employed. This model defines the three-dimensional spaces within the porous structure as 'pores' and the connections between pores as 'throats,' solving for the transient mass balance between pores. Flow velocity within the porous media follows principles like Darcy's law, where flux is driven by pressure differences, but also must consider the driving force due to capillary pressure owing to the small-scale nature. In the case of water electrolysis in PEM, the flow rates vary with the current density applied to the device. Generated bubbles progress towards liquid channels within the porous media. It's expected that structures impeding bubble progression would degrade electrolysis performance.Gas-liquid transport is strongly influenced by the pore size within the porous material. Within the porous structure, as the pore size increases, the capillary pressure required for progression decreases, making transport easier. However, larger pores also tend to trap bubbles within the porous structure, leading to an increase in concentration overpotential. In PEMWEs, various porous medias are being utilized; however, only quantitative evaluations have been conducted[2][3]. This study aims to elucidate the relationship between pore size and pore size distribution and their impact on gas-liquid transport performance, with a focus on non-woven fabric and particle types as the main research subjects.We confirmed that the three-dimensional structure inherent in each design affects gas-liquid transport properties. In the future, in order to validate the computational accuracy, it is necessary to conduct validation through experimental measurements in addition to calculations.AcknowledgmentThis study was supported by Center of Advanced Instrumental Analysis, Kyushu University.Reference[1] B. Han et al., Int. J. Hydrog. Energy, 42, 4478 (2017).[2] P. Lettenmeier et al., J. Power Sources, 311, 153 (2016).[3] H.Ito et al., Int. J. Hydrog. Energy, 37, 7418(2012).

Performance Characteristics of a Free-Breathing Polymer Electrolyte Fuel Cell with Various Channel Shapes

Free-breathing fuel cells of channel-type cathodes have straight vertical channels with open ends to supply oxygen to their cathode by natural convection. The channel structure should efficiently feed air to the cathode and ensure uniform contact between the electrode and the electrolyte. Several studies have reported the performance characteristics of free-breathing fuel cells with channel-type cathodes, including the effects of the width and the depth of the channels, the thickness of the gas diffusion layers, and the air blowing into the channels. However, we have seen no full reports investigating the performance characteristics of free-breathing fuel cells as a function of their channel shapes. This study utilized a small free-breathing fuel cell, with an active area of 4 cm2 (2 cm × 2 cm), and channel cathodes with various channel shapes, to experimentally investigate the effect of channel structure on cell performance, to numerically analyze the natural convection air flow in channels, and to compare with the results of performance characteristics.Our free-breathing fuel cell used a solid polymer electrolyte membrane of Nafion 112, with a thickness of 50 μm. The electrodes with gas diffusion layers were carbon paper (TGP-H-120) with a thickness of 0.37 mm, loaded with 1.0 mg/cm2 platinum. A separator on the anode had a meander channel with a width of 2 mm and a depth of 1 mm. The various channel-type separators on the cathode were based on a separator with four straight channels with a width of 3 mm, a depth of 3 mm, and a rib width of 2 mm, then some of the ribs were eliminated or their shapes were modified to promote natural convection through the channels.Experiments were carried out with the cell center plane perpendicular to the ground, and the channels of the cathode separator oriented vertically. The cell voltage and resistance (at a frequency of 10 kHz) were measured, by increasing current density in increments of 5 mA/cm2, until the cell voltage dropped to 0.3 V, at a non-humidified hydrogen supply rate of 7.0 cm3/min (normal). Experiments were conducted at ambient temperatures of 16 - 22 ºC and relative humidities of 35 - 40%.The experimental results indicated that, compared with a conventional cathode separator with four straight channels, cell performance was improved by eliminating some of the channel ribs and increasing the opening ratio, up to a point. A separator with 2 mm square ribs rotated by 45° further improved cell performance. However, when the opening ratio became too large, cell performance leveled off.CFD ULTIMATE (Autodesk Inc.) software was used to analyze the natural convection air flow. The analytical model consisted of the cathode separator, the electrode, the gasket, and their separating spaces, as well as spaces above and below the cathode separator (3 mm thick x 31 mm wide x 100 mm long). Natural convection of air was analyzed in these spaces. The temperature was set at 25 ºC on the electrode surface and 20 ºC on the other surfaces. The gauge pressure at the inlet of the space below the separator and at the outlet of the space above was set to 0 Pa. No air flow was allowed in the vertical direction on the sides of the spaces above and below the separator. The turbulence model was a low Reynolds number k-ε model and the analysis method was incompressible steady flow.The analysis results showed that, compared with a conventional cathode separator with four straight channels, eliminating some of the ribs and increasing the opening ratio resulted in higher flow velocities in the channels. In addition, a separator with 2 mm square ribs rotated by 45° showed even higher velocities next to the ribs. These analysis results revealed that separators with modified channels improved cell performance by promoting natural convection.

(Invited) Structure and Reactivity of Cobalt-Containing Nanocomposites for Electrocatalytic Oxygen Evolution in Acid Medium

Electrochemical water splitting involves two heterogeneous multi-step half-reactions, which are referred to as the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). It should be noted that the OER under acidic conditions has the following two advantages compared to the process in neutral and alkaline solutions. The kinetics of the OER in acidic media could be much faster due to the higher proton transfer rate between anode and cathode. The proton exchange membrane (PEM) is an acidic solid polymer electrolyte membrane characterized by good proton conductivity, excellent electrochemical durability, and high mechanical strength.Polynuclear iron(III) hexacyanoferrate(II), or Prussian blue, and its analogues possess unique open framework structures with the general chemical formula of AxMy[Fe-(CN)6]z·nH2O (where A = alkali metal cation, M = transition metal cation). The possibility to accommodate different transition metal cations within the coordination framework renders them with appealing electrochemical, ion-exchange, sensing, or photomagnetic properties, which have been the subject of intense research for decades. Despite their rigid structure, these mixed-metal coordination polymers are usually nonstoichiometric. This chemical variety makes them a versatile type of molecule-based materials. Prussian Blue type cobalt hexacyanoferrates seem to activate water molecules during photoelectrochemical oxidations. Here we report the water oxidation catalytic activity found in Prussian blue-type cobalt hexacyanoferrate modified electrodes both under conventional electrochermcal and photoelectrochemical conditions (using WO3 n-type semiconductor) in acid medium. It is noteworthy that some of the hybrid cobalt-ruthenium hexacyanoferrate compositions showed remarkable catalytic ability towards the oxygen evolution reaction in acid electrolyte. The enhanced catalytic activities of the as-synthesized electrodes should also be attributed to such features as high population of hydroxyl groups and high Broensted acidity (due to presence of Ru or W oxo sites) and related fast electron transfers coupled to unimpeded proton displacements. The possibility of metal-metal interactions between nanosized metals (Co and Ru or Co and W) cannot be excludedFor comparison, we also show that mixed-metal oxide nanocomposites combining the favorable catalytic properties of Co3O4 and CeO2, nanocomposites (with different phase distribution and Co3O4 loading) can modify the cobalt-oxo-species and enhance its intrinsic oxygen evolution reaction activity. Synthesis of Co3O4-modified CeO2, which was addressed through three different sol-gel based routes, each with 10.4 wt% Co3O4 loading, yielded three different nanocomposite morphologies: CeO2-supported Co3O4 layers, intermixed oxides, and homogeneously dispersed Co. It is reasonable to expect that the local bonding environment of Co3O4 can be modified after the introduction of nanocrystalline CeO2, which allows the CoIII species to be easily oxidized into catalytically active CoIV species, thus avoiding the undesirable surface reconstruction process. Here, ceria is likely to regulate the surface oxygen concentration, due to its oxygen buffer (storage/release) capacity, associated with the fast CeIV/CeIII redox transition. Our research addresses the problems related to the fabrication of efficient earth-abundant catalysts for oxygen evolution reaction, and it provides strategies for designing more active and stable catalytic systems.

High-performance, high energy density symmetric supercapacitors based on δ-MnO2 nanoflower electrodes incorporated with an ion-conducting polymer.

The present work investigates liquid-based and liquid-free supercapacitors assembled using δ-MnO2-nanoflower-based electrodes. An optimized electrode composition was prepared using acetylene black (AB), a polymer (PEO), a salt (LiClO4), and δ-MnO2 and used for device fabrication. The composite electrode was tested against a liquid electrolyte and a 'liquid-free' composite solid polymer electrolyte (CSPE) membrane. In a three electrode geometry, with 1 M solution of LiClO4 as an electrolyte, the specific capacitance of the electrode was found to be ∼385 F g-1, with a specific energy of ∼23 W h kg-1 and specific power of ∼341 W kg-1 (at 1 mA, 1 V). Dunn's method confirmed that the charge storage process was predominantly pseudocapacitive. When the device was assembled in a two-electrode Swagelok cell, a stable specific capacitance of ∼216 F g-1 was observed with a specific energy of 30 W h kg-1 and a specific power of 417 W kg-1. The supercapacitors exhibited stable performance up to ∼7000 cycles with ∼90% capacitance retention and ∼97% coulombic efficiency. A combination of these cells could light two white light-emitting diodes (LEDs, 3 V) for at least ∼10 minutes. Further, all-solid-state supercapacitors (ASSCs) were fabricated using a Li+ ion (CSPE) membrane. The ASSCs exhibited a specific capacitance of ∼496 F g-1 after ∼500 cycles, with a specific energy and power of ∼19 W h kg-1 and ∼367 W kg-1, respectively. The investigation reveals that the electrodes are versatile and show compatibility with liquid and solid electrolytes. The polymer in the electrode matrix plays an important role in enhancing device performance.

Boosting the rate performance of all-solid-state batteries with a novel double layer solid electrolyte

When compared to traditional liquid electrolytes, solid electrolytes face significant challenges due to insufficient ionic conductivity and poor interfacial contact. To overcome these challenges, a cathode-supported double layer gradient structured solid polymer electrolyte membrane is developed. This innovative design enhances the wetting ability of the solid electrolyte on the cathode, leading to improved rate performance. Furthermore, the double layer solid electrolyte enhances mechanical strength, ensuring excellent cycling performance. As a result, the LiFePO4/Li solid state battery demonstrates superior battery performances, for instance, it can achieve a discharge capacity of 121 mAh g−1 at a current rate of 5C, with a capacity retention of 99 % after 380 cycles. This work offers a promising strategy for further enhancing the performance of all solid-state batteries.

A Super-Ionic Solid-State Block Copolymer Electrolyte.

Polymer solid-state electrolytes offer great promise for battery materials with high energy density, mechanical stability, and improved safety. However, their low ion conductivities have so far limited their potential applications. Here, it is shown for poly(ethylene oxide) block copolymers that the super-stoichiometric addition of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) as lithium salt leads to the formation of a crystalline PEO block copolymer phase with exceptionally high ion conductivities and low activation energies. The addition of LiTFSI further induces block copolymer phase transitions into bi-continuous Fddd and gyroid network morphologies, providing continuous 3D conduction pathways. Both effects lead to solid-state block copolymer electrolyte membranes with ion conductivities of up to 1·10-1Scm-1 at 90°C, decreasing only moderately to 4·10-2Scm-1 at room temperature, and to >1·10-3Scm-1 at -20°C, corresponding to activation energies as low as 0.19eV. The co-crystallization of PEO and LiTFSI with ether and carbonate solvents is observed to play a key role to realize a super-ionic conduction mechanism. The discovery of PEO super-ionic conductivity at high lithium concentrations opens a new pathway for fabrication of solid polymer electrolyte membranes with sufficiently high ion conductivities over a broad temperature range with widespread applications in electrical devices.

Flexible magnesium-ion-conducting solid poly-blend electrolyte films for magnesium-ion batteries

Solid biodegradable polymer electrolyte systems are considered the optimal choice for energy storage devices because they are both cost-effective and energy-efficient. A solid blend polymer electrolyte (SBPE) membrane capable of transporting magnesium ions was prepared using a mixture of 70 wt% methylcellulose, 30 wt% chitosan, and varying wt% magnesium perchlorate salt. X-ray diffraction analysis revealed an increase in the amorphous nature caused by the inclusion of Mg(ClO4)2 salt in the polymer blend matrix. A Fourier transform infrared spectroscopy study of samples containing varying salt concentrations revealed secondary interactions between polymer segments and salt, which provides the basis for energy density. Moreover, through impedance analysis, it was determined that the bulk resistance decreased with increasing salt concentration. The SBPE containing 30 wt% magnesium perchlorate exhibited the highest ionic conductivity, with a value of 2.49 × 10–6 S cm−1. A comprehensive evaluation of the ion transport parameters, including mobility, carrier density, and diffusion, was conducted for the prepared electrolyte samples. Notably, an ionic transference number (tion) of approximately 0.83 was observed for the SBPE sample with 30 wt% magnesium salt, indicating ions’ prevalence as the system’s primary charge carriers. Electrochemical analyses demonstrated that the SBPE with the highest ion conductivity possessed an electrochemical stability window (ESW) of 1.92 V. Additionally, the thermal characteristics of the samples were evaluated using thermogravimetric analysis (TGA) to assess the thermal stability of the electrolyte. Finally, the highest conducting polymer electrolyte was employed to construct a primary magnesium battery, and its discharge profile with different cathode materials was studied. Based on these findings, the current study suggests an environmentally friendly, biodegradable, and economically viable electrolyte option suitable for separator cum electrolytes in magnesium-ion batteries.

Vertical channel‐structured cyanoethylated bacterial cellulose/polyethylene oxide composite solid electrolyte for all‐solid‐state lithium batteries

AbstractSolid polymer electrolytes (SPEs) have gained remarkable development within the realm of new energy resources. With its improved electrochemical stability and environmental‐friendly sustainability, bacterial cellulose (BC) has emerged as a promising candidate for applications in SPEs. Herein, bacterial cellulose was chemically cyanoethylated and integrated with lithium bis(trifluoromethanesulphonyl)imide/polyethylene oxide (PEO) based SPE. Some vertical channels are formed when trace amounts (0.5 wt%) of cyanoethylated bacterial cellulose (BC‐CN) are added to PEO‐based SPE, as revealed by SEM. This formula's corresponding PEO‐based SPE presents the highest ion conductivity of 5.7 × 10−4 S cm−1 at 60°C. The ion migration activation (Ea) deduced from the Arrhenius equation is 0.48 eV, lower than the value of 0.82 eV for the pristine PEO SPE. Besides, the Li+ migration number of this modified PEO‐based solid electrolyte is calculated to be a relatively high value of 0.33, while that of its counterpart, the pristine PEO SPE, is as low as 0.06. The all‐solid‐state lithium battery with PEO/0.5%BC‐CN SPE can operate stably for 115 cycles, which is longer than the 80 cycles achieved with the pristine PEO SPE. This study introduces a novel strategy for creating modified BC composites PEO‐based SPE.Highlights Bacterial cellulose was chemically cyanoethylated. Cyanoethylated bacterial cellulose composite polyethylene oxide (PEO)‐based solid polymer electrolytes (SPEs) are prepared in DMF. Opening pores penetrate the surface of the PEO/0.5% cyanoethylated bacterial cellulose (BC‐CN) SPE membrane. PEO/0.5% BC‐CN shows ionic conductivity of 5.7 × 10−4 S cm−1 at 60°C. Full cell with PEO/0.5% BC‐CN performs stably for 115 cycles.

Rational design of solid polymer electrolyte membranes based on poly(vinyl alcohol)/lithium salt‐plasticized with deep eutectic solvent

AbstractAs a key component for the future high‐safety lithium batteries, solid polymer electrolyte (SPE) is gaining an attractive momentum toward large‐scale production due to their remarkable compatibility and processability with electrodes. Further, their excellent performance can be improved using the potential use of plasticizers. A deep eutectic solvent (DES) synthesized from choline chloride (ChCl) and citric acid monohydrate (CAM) demonstrates a promising plasticizer to design good SPE membranes along with poly (vinyl alcohol) (PVA). The changes in surface chemistry of PVA‐based membranes, as determined by FTIR spectroscopy, confirms the success of DES‐plasticizing effect, where detected by wavenumber shifting around main functional groups such as OH, CO, and COC. Following this, EIS characterization on electrical properties reveals the role of 30 wt‐% DES in improving the ionic conductivity with the highest ionic conductivity equivalent to 4.66 × 10−4 S cm−1 and the crystallinity index as high as 41.09%. The presence of LiClO4 and DES and significantly reduces mechanical performance, and glass transition of PVA‐based membranes, as characterized by tensile testing and differential thermal analysis/thermogravimetric analysis. Thus, the presence of DES in PVA and LiClO4 matrices could open another window for designing SPE with novel physicochemical properties.

Development of Pseudo-Homogeneous Three-Dimensional Reaction Anode Structure for Proton Exchange Membrane Water Electrolysis

Solid Polymer Electrolyte (SPE) diaphragm such as Nafion🄬 has been applied to proton exchange membrane water electrolysis (PEMWE) due to the high efficiency and response. The structure of PEMWE consists of a catalyst layer, diffusion layer, current collector, flow-field, etc. In addition to the membrane, these elements and structural parameters were adapted from the proton exchange membrane fuel cell (PEMFC) technology due to the time series factors in the development process and are still strongly influenced by that technology today. Although PEMFC technology is applied to these elements in PEMWE, the material composition, structure, and various parameters are not fully optimized, and the basic structure and technology are diverted from various PEMFC conditions, although the main object of fluid has greatly changed from the gas phase to the liquid phase. As the above background, PEMWE technology needs to go back to the basic level of structural design, mainly from the viewpoint of mass transfer, and reconstruct the component structure.In this study, we focused on the mass transfer characteristics that most affect the performance of PEMWE and investigated a new structure for gas-liquid two-phase fluids for the electrode structure, which is the most important element of PEMWE.Figure 1 shows the two and three-dimensional reaction electrode structures in PEMWE. Figure 1(a) is the electrode structure of a conventional general PEMWE, which is the catalyst reaction in the catalyst layer on the rate-limiting electrode side proceeds in a heterogeneous two-dimensional reaction area. In this current method, sufficient diffusion cannot be maintained from the viewpoint of mass transfer, which leads to performance decrease due to the inability to remove obstacles such as bubbles to mass transport to the catalyst layer. Figure 1 (b) shows the pseudo-homogeneous three-dimensional reaction electrode structure developed in this study. The catalyst is supported on the porous current collector itself. This structure dramatically increases the reaction area from two-dimensional to three-dimensional, and it is expected to greatly improve electrolytic performance by optimizing various parameter conditions.The experimental was performed as following. The anode catalyst IrOx was synthesized from H2IrCl6-nH2O and NaNO3 by the Adams method1). Catalyst Ink, which mixed with the synthesized catalyst and Nafion🄬 dispersion solution, was dropped onto a Ti-web current collector and dried. The anode catalyst loading current collector was evaluated in a 1 cm2 component evaluation electrolyzer2).In this development, the essential issue is the establishment of the conditions to support the catalyst in the three-dimensional reaction area and to maintain the supply path of the proton from the SPE membrane efficiently.References T. Saida, S. Hirano, E. Niwa, F. Sato, and M. Maruyama, ECS Trans., 85, 865 (2018). K. Nagasawa, T. Ishida, H. Kashiwagi, Y. Sano, S. Mitsushima, Int. J. Hydrog. Energy, 46, 36619 (2021). Figure 1

Novel Electrocatalytic Hydrogenation Using a Solid Polymer Electrolyte (SPE) Reactor

Organic electrosynthetic reactions, which are driven by electricity, can generally be carried out under mild conditions (room temperature and ambient pressure). In addition, they do not require any hazardous reagents and produce less waste than other conventional chemical syntheses. Therefore, electrosynthesis is known to be a mild and clean method for organic synthesis and there has recently been renewed interest in its development. However, electrosynthesis also has some disadvantages. Ordinary chemical reactions are homogeneous, while the reaction field of electrolysis is a heterogeneous interface, therefore electrosynthesis has a productive drawback. In addition, a large amount of supporting electrolyte is usually required. Therefore, the availability of solvents is limited by the necessity for dissolution of a supporting electrolyte. The presence of the supporting electrolyte might also cause separation problems in the reaction workup. Moreover, in an ordinary electrolysis system, solution resistance is generated between the working and counter electrodes, resulting in a decrease in energy efficiency. To overcome these problems, we focused on a solid polymer electrolyte (SPE) reactor which was originally developed for fuel cell technologies and demonstrated various electrocatalytic hydrogenations in a SPE reactor (Figure 1) [1-5].As shown in Figure 1, a SPE membrane such as a proton exchange membrane (PEM) is integrated into the central part of the reactor, and is sandwiched between a pair of catalyst layers on the anode and cathode sides. For this reason, the substrate solution does not require a supporting electrolyte and the cell resistance can be minimized. The anode and cathode have highly porous 3D structures in order to conduct an efficient electrochemical reaction. Moreover, the reaction can be carried out in a flow operation. Thus, the SPE reactor system possesses many characteristics designed to overcome the disadvantages of conventional electrosynthetic processes.In a series of studies we have conducted, in this presentation, we will discuss two topics such as diastereoselective reduction of cyclic ketones and electrocatalytic hydrogenation of pyridines.The authors gratefully acknowledged support by JST CREST Grant No. 18070940, Japan.[1] A. Fukazawa, M. Atobe, et al. ACS Susutain. Chem. Eng. 2019, 7, 11050.[2] S. Nogami, M. Atobe, et al. J. Electrochem. Soc. 2020, 167, 155506.[3] A. Fukazawa, M. Atobe, et al. Org. Biomol. Chem. 2021, 19,7363.[4] S. Nogami, M. Atobe, et al. ACS Catalysis, 2022, 12, 5430.[5] Y. Shimizu, M. Atobe, et al. ACS Energy Lett., 2023, 8, 1010. Figure 1

Synthesis of carboxymethyl cellulose from coconut fibers and its application as solid polymer electrolyte membranes

AbstractCarboxymethyl cellulose (CMC) is one of the important cellulose derivatives, and it can be developed as a host polymer for solid polymer electrolyte (SPE) membrane. This study aimed to synthesis of CMC from coconut fiber cellulose and it was applied to prepare the SPE membranes. Cellulose isolation was conducted through the delignification and bleaching process, while the CMC synthesis was conducted through alkalization and carboxymethylation treatments. SPE membranes were prepared by blending CMC with carboxymethyl chitosan (CMCh) (80/20) and mixed with various weight percentages of LiOAc at room temperature. SPE membranes characterizations were conducted using FTIR, EIS, XRD, SEM, and tensile testing. Cellulose and CMC yields were 23.1% and 65.44%, respectively. Incorporating 20 wt% LiOAc into the CMC/CMCh (80/20) SPE membrane yielded the highest ionic conductivity of 1.37 × 10−3 S/cm. Based on the results, CMC obtained from coconut fibers has the potential to produce solid polymer electrolyte membranes with some modification.

Building Bulk and Interface Dual Fast Li+ Conducting Pathway in Composite Solid Polymer Electrolyte Membrane for All–Solid–State Lithium–Metal Batteries

AbstractSolid polymer electrolytes (SPEs) are considered a promising solution to the safety problems of lithium‐ion batteries (LIBs) using liquid electrolytes. However, the high crystallinity and low ionic conductivity hinder the practical application of SPEs. Herein, we design a composite solid polymer electrolyte with a dual fast Li+ conducting pathway in bulk and interface by incorporating highly Li+ conductive ceramic Li6.4Ga0.2La3Zr2O12 (LGLZO) in polyethylene oxide (PEO)/Li–bis (trifluoromethanesulfonyl) imide (LiTFSI) system. Compared to Li6.5La3Zr1.5Ta0.5O12 (LLZTO), LGLZO provides better Li+ conductivity; therefore, a fast Li+ conducting pathway will form in the bulk of LGLZO nanofillers. Besides, LGLZO nanofiller accelerates the dissociation of LiTFSI and benefits the transfer of free Li+ through the SPEs near the LGLZO surface, forming another interface fast Li+ conducting pathway in the SPEs. Benefits from the dual fast Li+ pathway design, the composite electrolyte membrane with 15 wt % LGLZO nanoparticles presents a high ionic conductivity of 8.0×10−4 S cm−1 at 60 °C. The Li−Li symmetric cells with optimized content LGLZO show good cycling stability (no short circuit even after 1000 h), and the all–solid Li/LiFePO4 batteries exhibit excellent cycling performance (remained 154 mAh g−1 after 500 cycles at 0.2 C under 60 °C).

Synthesis of nanoporous solid polymer electrolyte AuNiCe/NC hydrogenation membrane electrode

In this study, using graphite fiber cloth as the support, gold-based solid polymer electrolyte (SPE) membrane electrodes were synthesized by high-vacuum ion beam sputtering, nitrogen doping of the support, combined electrochemical dealloying, and hot-pressing technology. The application of the SPE membrane electrode to couple hydrogen evolution and liquid organic hydrogen storage is of significant importance for sustainable hydrogen energy and efficient carbon dioxide conversion. Using various characterization techniques, we systematically analyzed the phase structure, surface morphology, porous structure, and electrocatalytic performance of the membrane electrode for the hydrogenation of cyclohexene. The results indicated that doping the carbonaceous support with nitrogen (NC), doping with cerium as catalyst promoter, and combined electrochemical dealloying can all enhance the activity of the catalyst. Cerium doping provides the catalyst with oxygen vacancies for accelerated electron transfer. After combined electrochemical dealloying, AuNiCe/NC formed a three-dimensional bicontinuous porous structure. The electrochemically active surface area increased by 23.94 times, the energy consumption of catalytic cyclohexene hydrogenation decreased by 35.7%, and current efficiency and the formation rate of cyclohexane increased by 54.9% and 29.4%, respectively.