Electrolyte Thickness Research Articles

Comparative Performance Analysis of Different Cathode materials of Solid State Lithium ion Battery

In this paper , a single dimensional solid state lithium(Li)-ion batteries are simulated at different C-rates to analyze the characteristics like discharge curves, electrolyte potential along the thickness of electrolyte and variation of concentration along the electrolyte and positive electrode by using multi-physics simulation software tool, COMSOL. Li-ion batteries can be designed with different cathode materials but every material has its own advantages and disadvantages along with their applications. So, the main focus of this paper is to compare the characteristics of different cathode materials of Li-ion battery at different C-rates with similar design operating parameters.

High areal capacitance nickel-cobalt transition metal hydroxide/reduced graphene for structural supercapacitors

Structural supercapacitors (SSCs) as a kind of multifunctional energy storage device, show great potential in zero building energy consumption. Herein, SSCs with cement-based material as electrolytes and layered double hydroxides (LDH) as electrodes were prepared. The electrochemical performance of redox electrodes prepared by different methods was studied. The results show that T-3-rGO/NiCo-LDH prepared by the two-step hydrothermal method exhibits the best performance. Then different asymmetric SSCs with T-3-rGO/NiCo-LDH as positive electrode and rGO as negative electrode were fabricated successfully. Just as we expected, the thinner the thickness of the structural electrolyte is, the higher the areal capacitance. Therefore, the SSCs-1 cm2–0.2 cm prototype device exhibits the best performance, with a high areal capacitance of 255.94 mF/cm2, a high energy density of 79.98 μWh/cm2 at 2 mA/cm2 together with power density of 1500 μW/cm2. On this basis, the SSCs-20.25 cm2–0.2 cm was prepared, which exhibits a high energy density (40.32 μWh/cm2 at 5 mA/cm2) at a power density of 3750 μW/cm2. More importantly, the large-size electrode can carry more active substances, thus storing more electrical energy. Hence, the SSCs show great practical application potential in reducing carbon emissions in the field of large-volume buildings.

Synergistically enhanced roles based on 1D ceramic nanowire and 3D nanostructured polymer frameworks for composite electrolytes

Combining high ionic conductivity of inorganic solid electrolyte and favourable interface compatibility of polymer solid electrolyte, organic-inorganic composite electrolyte is more suitable for high-performance solid lithium battery. Herein, the polyacrylonitrile/polyvinylidene difluoride (PAN/PVDF) nanofiber membranes are prepared by electrospinning way, which can provide a strong skeleton support to improve the mechanical strength of composite electrolyte. The complexation between lithium ion and nitrile base of PAN can promote the transport of lithium ions and excellent oxidation resistance matching high-voltage cathode electrode. There are enough intermolecular hydrogen bonds between PVDF and PEO, and the presence of f in PVDF can enhance the interfacial interaction between the fiber membrane, polyethylene oxide (PEO) and lithium metal. Therefore, it can improve the conductivity of lithium ions and effectively inhibit the growth of severe lithium dendrites. Finally, the ionic conductivity of the composite electrolyte formed by introducing the Gd-doped SnO2 nanofibers (GDS NFs) into the PAN/PVDF nanofiber membranes and PEO matrix can reach 2.45 × 10−4 S cm−1 at 30 °C. In addition, the thickness of the composite electrolyte is only 65 μm, which can significantly improve the energy density of the battery. The specific capacity of the battery assembled with the electrolyte can still maintain 134.3 mA h g−1 after 300 cycles at 50 °C and 1C, and the specific capacity retention rate is up to 91.2 %. The NMC batteries also has a high reversible capacity even after 300 cycles. In conclusion, the Gd-doped SnO2 nanofibers and PAN/PVDF nanofiber membranes with excellent properties provide a novel idea for lithium metal batteries (LMBs).

New insights into single-step fabrication of finger-like anode/electrolyte for high-performance direct carbon solid oxide fuel cells: Experimental and simulation studies

Cell preparation techniques and design parameters have significant impacts on the electrochemical performance of direct carbon solid oxide fuel cells (DC-SOFCs). In this work, a finger-like nickel-based anode/electrolyte has been successfully fabricated in a single step via the tape-casting combined phase-inversion and co-sintering technique, which simplified the preparation process and reduced the fabrication cost. The finger-like anode/electrolyte exhibited identical microstructure and exceptional adhesion, ensuring the absence of any cracks during the co-sintering process. As a result, the corresponding single cell delivered a very competitive output of 436 mW cm−2 at 850 °C using activated carbon as fuel. Moreover, it operated stably for 20.1 h under 100 mA with a high fuel utilization of 22.5% at 850 °C. Model verification was also performed by comparative analysis of the effects of the finger-like pore length, anode thickness, cathode thickness, and electrolyte thickness on the cell performance using numerical simulation, which generated the resultant two-dimensional distributions of CO molar concentration, current density, O2 molar concentration, and temperature as well as the power output of the cell. Simulation results verified the experimental findings that DC-SOFC performance was enhanced with increases in the finger-like pore length and cathode thickness, and with decreases in the anode and electrolyte thicknesses. This work provides valuable insights into further optimizing the cell design and manufacturing process, paving the way for the development of high-performance DC-SOFCs.

Grain boundary-abundant copper nanoribbons on balanced gas-liquid diffusion electrodes for efficient CO2 electroreduction to C2H4

The electrocatalytic CO2 reduction reaction (CO2RR) is a promising technology to produce value-added hydrocarbon chemicals, however, achieving a high selectivity to C2+ products at the industrial current density remains a great challenge. Herein, we demonstrate grain boundary-abundant copper (Cu) nanoribbons on balanced gas-liquid diffusion electrodes for efficient CO2RR to ethylene (C2H4). The Cu(II) carbonate basic (Cu2CO3(OH)2) nanoribbon is used as a precursor to convert into metal Cu under in situ electrochemical reduction. Unexpectedly, the generated Cu nanoribbon is formed by stacking tiny nanoparticles with exposure of Cu(111), Cu(200) and Cu(220) facets, which creates abundant grain boundaries (GBs). During CO2RR test, the thickness of the catalyst layer is identified as a crucial factor for the mass transfer of CO2 and electrolyte. By tailoring the thickness of catalytic layer, CO2 and electrolyte can simultaneously reach the surface of catalyst and participate in CO2RR. Under the synergetic effects of GBs and balanced gas-liquid diffusion, the optimized electrode delivers the Faradaic efficiencies toward C2H4 and C2+ products as high as 67.2% and 82.1% at the current density of 700 mA cm−2, respectively. Moreover, the partial current density of C2H4 can reach up to 505 mA cm−2, which is significantly higher than most reported results. The in situ Raman and attenuated total reflection surface-enhanced infrared absorption spectra show that abundant GBs enhance the activation of CO2 and significantly promote the formation and adsorption of *CO intermediates, which accelerate C-C coupling to form *OCCO and *OCCOH intermediates and improve the production of C2H4 and other C2+ products.

Flexible and thin sulfide-based solid electrolyte sheet with Li+-ion conductive polymer network for all-solid-state lithium-ion batteries

All-solid-state lithium batteries (ASSLBs) with solid electrolytes are promising battery systems capable of improving the safety and energy density of current lithium-ion batteries. Reducing the thickness of the solid electrolyte while preventing the short circuit between the anode and cathode is imperative to increase the energy density of ASSLBs. Sulfide-based solid electrolytes have high ionic conductivities; however, they are brittle, difficult to be processed into a thin film, and challenging to form stable interfaces with electrodes of large volume change. In this study, flexible thin-solid electrolyte sheets with Li+-ion conductive polymer network were prepared and characterized for ASSLB applications. They exhibited higher ionic conductance and superior mechanical properties than those of pristine Li6PS5X (argyrodite) pellets. The all-solid-state lithium-ion cell (graphite/LiNi0.7Co0.15Mn0.15O2) with a solid electrolyte sheet delivered a high discharge capacity of 182.5 mAh g−1 and showed good cycling stability at 0.33 C and 25 ℃, demonstrating that flexible and thin sheets are promising solid electrolytes for ASSLBs operating at room temperature.

Modeling and simulation in rate performance of solid-state lithium-ion batteries at low temperatures

Solid-state lithium-ion batteries (SSBs) not only improve the energy density of batteries, but also solve the unavoidable battery safety problems of liquid electrolytes. However, the rate capability of SSBs cannot meet the needs of practical applications due to the defects of low ionic conductivity and slow reaction rate of solid-solid interface, which becomes one of the bottlenecks restricting its development. Moreover, SSBs usually suffer from capacity reduction and security problems under low temperatures. This paper established a two-dimensional model of SSBs based on a multi-physical field simulation software, and studied the rate performance of SSBs under low temperatures. The distribution of lithium ion concentration in both electrolyte and cathode, diffusion coefficient of lithium ion and high rate discharge behavior of SSBs at low temperature were discussed in details. The simulation results exhibit that the rate capability of SSBs at low temperature can be improved by appropriately reducing the thickness of solid-state electrolyte. When the electrolyte thickness is fixed as 0.6 μm, the discharge capacities decrease from 0.345 Ah m−2 to 0.343 Ah m−2 as the discharge rates increase from 3C to 8C, together with a high capacity retention ratio of 99.5 %. Besides, SSBs can still maintain a high and flat discharge platform even at the high rate of 8C. This study proposes a method to improve the rate performance of solid state battery at low working temperatures, which has a theoretical guiding significance and engineering value for the structure design of SSBs.

Galvanic Interactions on a Coupled Microelectrode Array of AA7050-T7451 and 316 Stainless Steel in Chromate-Containing NaCl Solutions Under Thick Electrolyte Film and Cyclic Wet-Dry Conditions

The electrochemical behavior of an AA7050-316SS galvanic couple in chromate-containing NaCl environments under relatively constant thick electrolyte films and wet-dry cycling was investigated utilizing the coupled microelectrode array (CMEA) approach. The CMEA approach provided a means to analyze the in situ electrochemical kinetics as a function of spatial location and time. In inhibitor-free environments, the total net anodic charge associated with galvanic current increased with increasing conductivity and aggressiveness of the environment. The AA7050 electrodes supplied more than half of the total net cathodic charge in relation to the 316SS (316 stainless steel) electrodes in the more aggressive environments. Under thick electrolyte films, chromate became less effective at suppressing cathodic kinetics on the 316SS and AA7050 net cathodes as the chloride concentration increased. Under wet-dry cycling conditions, the effectiveness of chromate was diminished when compared to thick electrolyte film conditions, due to the cycling of the equilibrium chloride concentration as electrolyte thickness changed upon onset of drying and wetting while the loading density of the salt remained constant. Furthermore, chromate exhibited a diminished ability to suppress cathodic currents on the AA7050 net cathodes in comparison to the 316SS electrodes. This study highlighted the importance of Cu-rich intermetallic particles and replated Cu on precipitation-strengthened Al alloys when considering the driving force of cathodes in sustaining anodic dissolution in typical Al alloy macro-galvanic systems exposed to atmospheric conditions.

Ultra-elevated power density and high energy efficiency of protonic ceramic fuel cells: Numerical and experimental results

The fabrication of high-performance protonic ceramic fuel cells (PCFCs) and the accurate evaluation of their energy efficiency remain challenging because of electron–hole leakage. By combining an established numerical method with experiments, we developed high-performance chemically stable Ce-free PCFCs with a BaZr0.8Yb0.2O3−δ electrolyte that perform comparably to first-tier PCFCs, which typically employ Ce-containing electrolytes. To the best of our knowledge, this study is the first to numerically reproduce experimental performance over a wide range of temperatures, electrolyte thicknesses, and current densities. Importantly, our study can accurately predict the ultra-elevated performance of cells under different conditions without the need for conducting additional experiments (e.g., > 3.0 W·cm−2 power density or > 70% lower heating value energy efficiency)

Tuned Reactivity at the Lithium Metal–Argyrodite Solid State Electrolyte Interphase

AbstractThin intermetallic Li2Te–LiTe3 bilayer (0.75 µm) derived from 2D tellurene stabilizes the solid electrolyte interphase (SEI) of lithium metal and argyrodite (LPSCl, Li6PS5Cl) solid‐state electrolyte (SSE). Tellurene is loaded onto a standard battery separator and reacted with lithium through single‐pass mechanical rolling, or transferred directly to SSE surface by pressing. State‐of‐the‐art electrochemical performance is achieved, e.g., symmetric cell stable for 300 cycles (1800 h) at 1 mA cm−2 and 3 mAh cm−2 (25% DOD, 60 µm foil). Cryo‐stage focused ion beam (Cryo‐FIB) sectioning and Raman mapping demonstrate that the Li2Te–LiTe3 bilayer impedes SSE decomposition. The unmodified Li–LPSCl interphase is electrochemically unstable with a geometrically heterogeneous reduction decomposition reaction front that extends deep into the SSE. Decomposition drives voiding in Li metal due to its high flux to the reaction front, as well as voiding in the SSE due to the associated volume changes. Analysis of cycled SSE found no evidence for pristine (unreacted) lithium metal filaments/dendrites, implying failure driven by decomposition phases with sufficient electrical conductivity that span electrolyte thickness. DFT calculations clarify thermodynamic stability, interfacial adhesion, and electronic transport properties of interphases, while mesoscale modeling examines interrelations between reaction front heterogeneity (SEI heterogeneity), current distribution, and localized chemo‐mechanical stresses.

Modeling and microstructural study of anode-supported solid oxide fuel cells: Experimental and thermodynamic analyses

Developing novel solid oxide fuel cells (SOFCs) with high stability running at low temperatures is an important objective in SOFC science. In the current paper, a comprehensive physics-based microstructure modeling using scanning electron microscope (SEM) image analysis was performed on several anode-support SOFCs operating at low temperatures with high stability. To bridge the gap in the literature regarding an accurate and realistic modeling, a new model was developed based on the variable fuel and air utilization factors and updated microstructure values (e.g., tortuosity, porosity, pore size, grain size). The model accuracy was verified by a thorough point-to-point validation for eight different cells with the configuration of Ni-YSZ (anode), YSZ (electrolyte), and GDC/PNO (cathode). Different temperatures, hydrogen, and air mass flow rates were used, for which an average error of less than 3% in the I-V curves was achieved. The microstructure of the cells, including cathode thickness (15–26 μm), anode-support thickness (350–460 μm), porosity (39 and 43%), grain size (1.1–1.4 μm), and pore radius (0.9–1.1 μm) were varied. Moreover, the effects of the critical operational and design parameters on the overpotential losses and cell performance were studied. The results show that a hydrogen flow rate of 43 sccm was ideal when the cell operated at 0.9 A/cm2 and 700 °C. Moreover, an average anode-support pore radius of 1.75 μm resulted in the best cell performance. It was also concluded that the electrolyte thickness has a higher effect on the cell performance compared to the cathode thickness.

Investigation of the Influence of Silicon Oxide Content on Electrolyte Degradation, Gas Evolution, and Thickness Change in Silicon Oxide/Graphite Composite Anodes for Li-Ion Cells Using Operando Techniques

This research paper investigates the influence of varying silicon oxide (SiOx) content on the performance and aging of lithium-ion cells. In-depth investigations encompass charge and discharge curves, thickness changes, electrolyte degradation, gas evolution, and chemical analysis of cells with different silicon oxide proportions in the anode and their associated cathodes. The results show that a higher silicon oxide content in the anode increases the voltage hysteresis between charge and discharge. Moreover, the first-cycle efficiencies decrease with a higher silicon oxide content, attributed to irreversible LixSiy formation and the subsequent loss of active lithium from the cathode during formation. The anodes experience higher thickness changes with increased silicon oxide content, and peaks in differential voltage curves can be correlated with specific anode active materials and their thickness change. A gas analysis reveals conductive salt and electrolyte intermediates as well as silicon-containing gaseous fragments, indicating continuous electrolyte decomposition and silicon oxide aging, respectively. Additionally, a chemical analysis confirms increased silicon-derived products and electrolyte degradation on electrode surfaces. These findings underscore the importance of a holistic aging investigation and help understand the complex chemical changes in electrode materials for designing efficient and durable lithium-ion cells.

Maximizing Electrostatic Polarity of Non‐Sacrificial Electrolyte Additives Enables Stable Zinc‐Metal Anodes for Aqueous Batteries

AbstractAlthough additives are widely used in aqueous electrolytes to inhibit the formation of dendrites and hydrogen evolution reactions on Zn anodes, there is a lack of rational design principles and systematic mechanistic studies on how to select a suitable additive to regulate reversible Zn plating/stripping chemistry. Here, using saccharides as the representatives, we reveal that the electrostatic polarity of non‐sacrificial additives is a critical descriptor for their ability to stabilize Zn anodes. Non‐sacrificial additives are found to continuously modulate the solvation structure of Zn ions and form a molecular adsorption layer (MAL) for uniform Zn deposition, avoiding the thick solid electrolyte interphase layer due to the decomposition of sacrificial additives. A high electrostatic polarity renders sucrose the best hydrated Zn2+ desolvation ability and facilitates the MAL formation, resulting in the best cycling stability with a long‐term reversible plating/stripping cycle life of thousands of hours. This study provides theoretical guidance for the screening of optimal additives for high‐performance ZIBs.

Maximizing Electrostatic Polarity of Non-Sacrificial Electrolyte Additives Enables Stable Zinc-Metal Anodes for Aqueous Batteries.

Although additives are widely used in aqueous electrolytes to inhibit the formation of dendrites and hydrogen evolution reactions on Zn anodes, there is a lack of rational design principles and systematic mechanistic studies on how to select a suitable additive to regulate reversible Zn plating/stripping chemistry. Here, using saccharides as the representatives, we reveal that the electrostatic polarity of non-sacrificial additives is a critical descriptor for their ability to stabilize Zn anodes. Non-sacrificial additives are found to continuously modulate the solvation structure of Zn ions and form a molecular adsorption layer (MAL) for uniform Zn deposition, avoiding the thick solid electrolyte interphase layer due to the decomposition of sacrificial additives. A high electrostatic polarity renders sucrose the best hydrated Zn2+ desolvation ability and facilitates the MAL formation, resulting in the best cycling stability with a long-term reversible plating/stripping cycle life of thousands of hours. This study provides theoretical guidance for the screening of optimal additives for high-performance ZIBs.

Lightweight Solid Oxide Cell Design for Ammonia-Fed SOFC Systems

OxEon Energy team has been advancing solid oxide fuel cell (SOFC) technology for over three decades and solid oxide electrolysis cell (SOEC) technology using identical stacks for 15 years.OxEon’s SOEC/SOFC technology builds on the success of the SOEC stack installed on NASA’s Mars Perseverance Rover that produces high-purity O2 by electrolyzing Mars atmosphere CO2. The OxEon team worked with Jet Propulsion Laboratory (JPL) and Massachusetts Institute of Technology (MIT) to validate the MOXIE (Mars Oxygen In-situ resource utilization Experiment) stack.MOXIE stack demonstrated that the operational performance on Mars matched results from pre-launch earth testing. MOXIE stack design forms the basis for developing lightweight fuel cell design suitable for an electric Vertical Take-off and Landing (eVTOL). Demonstration of SOFC performance using carbon-free fuels such as ammonia is another critical objective.A lightweight cell design was developed to increase specific power (kW/kg) of the fuel cell stack. The electrolyte thickness, the most resistive element of the SOFC, was reduced from ~250 microns to 70 microns (72% decrease). The fabrication process results in a dense scandia stabilized zirconia ScSZ electrolyte and a porous yttria stabilized zirconia (YSZ) matrix for cathode (air electrode) infiltration. For the fuel electrode, both an infiltrated and screen printed options are evaluated.Producing an infiltrated electrode with a well-adhered and homogeneous distribution of active material is a challenge that requires multiple infiltration-calcination cycles to deposit sufficient material. Key variables are precursor chemistry to reduce the number of infiltrations and to prevent interaction between electrode layers; intermediate calcination temperatures, and process development using an infiltration equipment that enables volume production. OxEon partnered with National Energy Technology Laboratory (NETL) for electrode infiltration process development and PNNL for validation testing of cells. Full size cells are in production for stack testing.Fuel flexibility was demonstrated in button cells and stacks previously. Button cell and stack performance was nearly identical among hydrogen, ammonia, and reformed natural gas. Durability testing shows similarly stable performance in each fuel.A button cell test in ammonia at 800 °C using the thin electrolyte cell structure measured a button cell area specific resistance (ASR) of 0.25 Ω-cm2 in H2/N2 and NH3 fuel feeds and showed a peak power density of 0.98 W/ cm2 in NH3 fuel feed. Short term hold at 0.7 V showed stable performance.Analysis of additional button cell tests and stack tests using thin electrolyte cell structure will inform test stand design modifications that address balance of plant size requirements.This material is based on research sponsored by Air Force Research Laboratory under agreement number FA8649-22-P-0792. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Department of the Air Force, the Department of Defense, or the U.S. government. Approved for public release; distribution is unlimited. Public Affairs release approval #_______________. Figure 1

Silicon-Containing Anodes for High-Energy Density Lithium-Ion Batteries

Next- Generation Lithium(Li)-based rechargeable battery technologies utilising silicon (Si) and Si-containing (Si/Gr, SiOx/Gr, SiNx etc.) anodes coupled with high-capacity/high-voltage insertion-type cathodes (IC) have gained significant attention from both academic and industrial sectors.1 This originates from their practically achievable high energy density, offering a new possibility towards the large-scale espousal of electric vehicles and effective integration of renewable energy sources. In pursuit of designing such high-energy-density electrical energy storage devices, the anode compartment plays huge role and has accordingly reaped increasing interest. In this regards, Si and Si-containing materials are considered to be the most promising choices to replace state-of-the-art graphite in the construction of Lithium-ion batteries (LIBs). This is attributed to their unparalleled high theoretical capacity, suitable operating voltage, natural abundance, environmental benignity, nontoxicity, high safety, and so forth.However, Si and Si-containing materials are endowed with their own advantages and inherent shortcomings. Colossal volume change, much lower diffusivity (σe-+ and DLi+), unstable and fragile solid electrolyte interphase (SEI) formation, electrode swelling, and electrolyte drying are among the most impending intrinsic challenges that hider the large-scale commercialization of such innovative materials. Moreover, the detailed storage mechanism, electrochemistry, failure mechanism and impact of each component in case of blended/composite anode materials (e.g., Si/Gr and SiOX/Gr) etc. remain to be key loopholes to fully understand and thus enable the systems.In this paper, accounts on the various Si-containing active materials (Si, SiOx, Si/Gr blend/composite, SiOx/Gr blend/composite, SiNx etc) including their pros and cons, recent progresses, detailed storage chemistries and mechanisms, characteristics, possible tailored remedies to evade their challenges and thus improving performances - in hope of facilitating their large-scale deployment in the market, and future prospects and research directions will be presented. Impact of atomic level peculiar properties on the material and battery cells level key performance matrices are thoroughly examined. Moreover, the specific energy (Eg) and energy (Ev) density of various insertion-type cathode materials as a function of a) the weight fraction of Si at a fixed areal capacity, b) areal capacity at various Si contents, c) various kinds of electrolytes (liquid, polymer, glass and ceramic) at a fixed areal capacity, and d) electrolyte thickness are evaluated and analyzed.The approach presented in this paper will spur new concepts and perspectives into the best use of Silicon (Si) and Si-containing anode materials for the development Next-Generation high-energy density LIBs. 1Eshetu, G. G.; Zhang, H.; Judez, X.; Adenusi, H.; Armand, M.; Passerini, S.; Figgemeier, E, “Gebrekidan Gebresilassie Eshetu, Heng Zhang, Xabier Judez, Henry Adenusi, Michel Armand, Stefano Passerini, & Egbert Figgemeier, “Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes.” Nat. Commun. 2021, 12 (1), 1–14.

Interface Resistance Analysis in Solid Oxide Fuel Cells

A sophisticated design of the interface structure between the cathode and the electrolyte is essential to improve the performance of solid oxide fuel cells (SOFCs). It is because the interface is the place where it directly affects both the ohmic resistance and the polarization resistance as interface contact and interface reaction, respectively. To improve interface properties, electrolyte surface treatment or inserting interface functional layer between the cathode and the electrolyte have been applied. They improved cell performance by effectively enhancing the interfacial characteristics such as interface bonding and interface reaction area. However, although both ohmic and polarization resistance greatly contributed to the improved cell performance, a detailed analysis related to ohmic resistance compared to polarization resistance is insufficient. Unlike polarization resistance which can quantify interface reaction related resistance using distribution of relaxation time (DRT) model, there is no proper methodology to quantify interface resistance in the case of ohmic resistance. The interface resistance has been analyzed to the extent that it belongs to the remaining resistance except for the electrolyte resistance from total ohmic resistance in consideration of the ionic conductivity and thickness of the electrolyte, which still not completely separate the interface resistance from the total ohmic resistance. Furthermore, in recent years, the electrolyte thickness has gradually decreased to less than 5 μm for high-performance and the electrolyte resistance has been significantly reduced, increasing proportion of interface resistance in total ohmic resistance. Therefore, we need to reduce the interface resistance for further cell improvement. Also, quantifying the interface resistance and having a deeper understanding of the correlation between interface resistance and interface structure should be supported.Here, to realize the interface resistance from the ohmic resistance, we designed several types of interface structure using electrostatic spray deposition (ESD) which can precisely control the particle size and be used to fabricate a thin functional layer. Using the different interface properties and equivalent circuit models, we separate the interface resistance from the ohmic resistance quantitatively. Our results can suggest a simple and effective interface analysis method for achieving high performance SOFCs. Figure 1

Assessing the Impact of BaZr0.7Y0.3-YPryO3- d Composition on Water Splitting Kinetics in Composite Pr2NiO4+Δ-BaZr0.7Y0.3-YPryO3- d Electrodes in Proton-Conducting Electrolysis Cells

Protonic-ceramic electrolysis cells (PCECs), with proton-conducting oxide electrolytes, provide high current densities between 500-700°C because electrolytes such as BaCe0.8-xZrxY0.1Yb0.1O3-δ (BCZYYb) have protonic conductivities in this temperature range. The protonic conductivities of BCZYYb are almost an order of magnitude higher than oxide-ion conductivities in conventional solid-oxide electrolytes. To convert such high ionic fluxes in PCECs into efficient hydrogen production, robust positive electrodes (positrodes) must be developed with reduced overpotentials associated with water-splitting kinetics and proton incorporation [1]. The positrodes with Ruddlesden-Popper oxides like Pr2NiO4+δ(PNO) have demonstrated effective water-splitting kinetics as well as mechanical and chemical compatibility with barium zirconate electrolytes [2]. As a mixed conductor, PNO conducts polarons, oxide ions, and protonic defects (OH●) into the crystal structure [3]. However, its relatively low proton and oxide-ion conductivities limit charge transfer reaction near three-phase boundaries with the electrolyte, which increases positrode overpotentials. To improve the surface conductivity in PNO-based positrodes, our team, in collaboration with West Virginia University [4], has explored the impact of very thin overlayers of mixed ion-conducting BaZr0.7Y0.15Pr0.15O3- d (BZYP) on PNO positrode layers. Electrochemical characterization showed that the BZYP overlayers reduce the area-specific resistance of the PNO positrodes by ≈50% at 550-700°C: this suggests the extension of the electrochemically active surface area required for the water-splitting reaction beyond three-phase boundaries. The present study focuses on optimizing composite PNO-BZYP porous positrodes in conventional negatrode-supported PCECs to understand the water-splitting reaction mechanism for efficient electrolysis.Composite PNO-BaZr0.7Y0.3-yPryO3- d (BZYP) positrodes were fabricated for a range of Y/P cation ratios. The 22 mm diameter negatrode-supported button cells included 1 mm thick porous negatrodes of BaCe0.4Zr0.4Y0.1Yb0.1O3-δ(BCZYYb4411)-NiO and a spray-coated 5-10 μm thick BCZYYb4411 electrolytes as shown in figure 1. These negatrode-electrolytes were sintered at 1550°C for 6 h. The PNO and BZYP positrode powders were synthesized by solid-state reaction at 1350°C and 1500°C, respectively. PNO was identified as an orthorhombic crystal structure, and BZYP as a tetragonal crystal structure. Reactivity tests PNO and BZYP (1:1 wt ratio) at 1050°C, 1150°C, and 1250°C for 5 h showed no phase change. After negatrode-electrolyte sintering, both single-phase PNO (reference), and composite PNO-BZYP slurries were painted on the exposed electrolyte layers and sintered at 1150°C for 5 h to provide porous positrodes.Electrochemical impedance spectroscopy (EIS) and current-voltage measurements on BZYP-PNO positrode were compared with PNO positrode in the temperature range of 550-700°C. During these measurements, steam, and oxygen partial pressures were varied by 3-50%. EIS measurements informed the resistances associated with the different processes in the water-splitting reaction mechanism. The impact of both proton/oxygen ion and electron conductivity on the water-splitting kinetics could be identified based on different BZYP compositions by investigating the effects of temperatures, steam, and oxygen partial pressures. Different Y/P cation ratios in BZYP supported the investigation of how different (proton/oxygen ion and electron) conductivities in the BZYP impact the electrochemical water-splitting reaction. Figure 1

Enhancing Cycling Stability and Capacity Retention of High-Capacity-High-Voltage Cathodes by Reengineering Interfaces Via Electrochemical Fluorination

High-capacity high voltage cathodes (NMC811, LNMO) are promising cathodes for electromobility due to high energy densities. However, several factors (extensive oxidation of electrolytes, growth of thick cathode electrolyte interphase (CEI), irreversible capacity loss, low coulombic efficiency) related to high energy density materials inhibit their practical application. Herein, we report the formation of the conformal LiF interfaces on NMC811/LNMO cathodes via novel electrochemical fluorination. An electrochemically induced LiF layer stabilized the interfaces and reduces the leakage of the electrons allowing lithium-ion conduction. Because of such robust CEI composed of LiF, electrochemically fluorinated cathodes demonstrated significantly improved cycling stability and enhanced capacity.

Structure and Dynamics of the Electrical Double Layer during the Rapid Alternating Polarity Electro-Synthesis

Conventional electrochemical organic synthesis uses direct current (DC) condition, where the electrode polarity is not changed during the operation. Unlike DC, alternating current (AC) introduces two more tunable parameters into the potential or current profile: frequency and waveform, allowing new possibilities for modulating reaction efficiency and selectivity. Several very recent AC electrosynthesis examples have shown that the AC can lead to enhanced chemoselectivity that cannot be reproduced by their DC counterparts1–3. For instance, Hayashi et al. presented a highly selective and easily scalable Birch-type reduction of heteroarenes by rapid alternating polarity (rAP) waveform3. AC voltage transforms the reaction kinetics presumably by affecting the mass transfer of reactive species both in the bulk solution and the electrical double layers (EDL). However, the mechanistic origin of the unique reactivity in AC electrosynthesis is underexplored. Molecular-level details are still in lack to possibly guide the rational design of AC reaction parameters.In this study, we have chosen the rAP heteroarene reduction as the example system and employed classical molecular dynamics (MD) simulations to reveal the liquid structure and dynamics in bulk and interfacial electrolyte. To capture the electrode-electrolyte interfaces, a slab-geometry simulation cell was used, where a 10 nm thick liquid electrolyte is sandwiched between two oppositely charged graphene surfaces. The multicomponent electrolyte was composed of ethanol and tetrahydrofuran (THF) as the co-solvent, [(CH3)4N]+[(BF4)]- as the salt, and a heteroarene substrate. Based on the charge distribution function statistics, the EDL layer was about 1 nm thick, so if any of the oxygen atom in the ethanol or THF is within 6 Å to the electrode surface, they are considered to be within the EDL. Under both AC and DC, the ethanol to THF ratio was higher than that in the bulk electrolyte due to stronger ion-ethanol attraction. The EDL structure responded to electric field polarity change at different time scales. First, the molecule orientation would flip also within the picosecond time scale after the polarity switch. By tracking the number of molecules in the EDL, we have found that the compositional fluctuation in the EDL converges in about 40 ps. Although it is the ion migration that gets directly affected by the alternating electric field, diffusion of charge-neutral molecules was also found to be accelerated under AC, according to the higher mean squared displacement calculated from the movement of all molecules of each species in the simulation box. This accelerated diffusion spans a larger length and longer time scales. A multi-scale model is proposed to describe both reaction kinetics and liquid structure dynamics simultaneously.