Electrode Stack Research Articles

Automated Robotic Cell Fabrication Technology for Stacked‐Type Lithium‐Oxygen Batteries

AbstractRechargeable lithium‐oxygen batteries (LOBs) are gaining interest as next‐generation energy storage devices due to their superior theoretical energy density. While recent years have seen successful operation of LOBs with high cell‐level energy density, the technology for cell fabrication is still in its infancy. This is because the cell fabrication procedure for LOBs is quite different from that of conventional lithium‐ion batteries. The study presents a fully automated sequential robotic experimental setup for the fabrication of stacked‐type LOB cells. This approach allows for high accuracy and high throughput fabrication of the cells. The developed system enables the fabrication of over 80 cells per day, which is 10 times higher than conventional human‐based experiments. In addition, the high alignment accuracy during the electrode stacking and electrolyte injection process results in improved battery performance and reproducibility. The effectiveness of the developed system was also confirmed by investigating a multi‐component electrolyte to maximize battery performance. We believe the methodology demonstrated in the present study is beneficial for accelerating the research and development of LOBs.

Formation Mechanism and Prevention of Cu Undercut Defects in the Photoresist Stripping Process of MoNb/Cu Stacked Electrodes

The Cu undercut is a recently discovered new defect generated in the wet stripping process of MoNb/Cu gate stacked electrodes for thin-film transistors (TFTs). The formation mechanism and preventive strategy of this defect were identified and investigated in this paper. The impact of stripper concentration and stripping times on the morphology and the corrosion potential (Ecorr) of Cu and MoNb were studied. It is observed that the undercut is Cu tip-deficient, not the theoretical MoNb indentation, and the undercut becomes severer with the increase in stripping times. The in-depth mechanism analysis revealed that the abnormal Cu undercut was not ascribed to the galvanic corrosion between MoNb and Cu but to the local crevice corrosion caused by the corrosive medium intruding along the MoNb/Cu interface. Based on this newly found knowledge, three possible prevention schemes (MoNiTi (abbreviated as Mo technology development (MTD) layer/Cu), MoNb/Cu/MTD, and MoNb/Cu/MoNb) were proposed. The experimental validation shows that the Cu undercut can only be completely eliminated in the MoNb/Cu/MTD triple-stacked structure with the top MTD layer as a sacrificial anode. This work provides an effective and economical method to avoid the Cu undercut defect. The obtained results can help ensure TFT yield and improve the performance of TFT devices.

Increasing of efficiency of hydrogen energy storage system by the use of high-pressure electrolyser with metal hydride electrode

The article describes the electrochemical process of hydrogen and oxygen generation by a membrane-less electrolyser having a passive electrode made of Ni and a gas absorption electrode made of metal hydride (LaNi5Hx). Such composition of the electrode stack materials (Ni - LaNi5Hx) makes it possible to generate hydrogen and oxygen during the half-cycles separately in time while maintaining the time intervals of the corresponding half-cycles. The last one indicates the stable capacitive characteristics of the LaNi5Hx metal hydride electrode. During the oxygen half-cycle, hydrogen is absorbed in the metal hydride electrode while oxygen is released at the nickel electrode and then removed into the oxygen storage system. During the subsequent half-cycle, the hydrogen absorbed by the metal hydride electrode is removed into the hydrogen storage system. We have studied the above electrolysis process with help of the laboratory experimental membrane-less electrolyser giving the possibility for generating, storing and compressing hydrogen in it. The use of a chemically active LaNi5Hx electrode will make it possible to implement a hydrogen energy storage system (electrolyser-storage system-consumer) and accordingly to increase the efficiency of the power plant by ≈ 8–10 %. It would be effective to use such high-pressure membrane-less electrolyser as an energy storage system element of an energy complex that receives electricity from the renewable energy sources (sun, wind).

(Invited) Structured Electrode Manufacturing for Next-Generation Lithium-Ion Batteries

Achieving high-energy and high-power density Lithium-ion batteries (LIBs) with fast charging capabilities is critical to advancing electric vehicle (EV) and portable electronic technologies. Long-range, fast charge EVs and more compact portable electronics require significant advances in battery performance, lifetime, and cost. Conventional LIBs are composed of flat anode and cathode electrode stacks that can be optimized for energy or power, but not both concurrently. This is due to ion transport limitations that persist with increases in electrode thickness. Several research efforts have focused on optimizing LIB performance through material innovations with lithium metal and silicon anodes or new cathode materials, to name a few. Structured Electrode (SE) designs1 have been investigated over the last couple of decades as an alternate solution to address these challenges. SEs engineer electrode materials into different three-dimensional (3D) architectures on a scale ranging from tens to hundreds of microns to facilitate rapid ion-transport in thicker electrodes. While a promising concept, reliable and scalable manufacturing methods for fabricating SEs over the large and complex areas needed for EV and portable electronic applications remains limited.This talk covers manufacturing approaches investigated by our research group to fabricate SEs rapidly and efficiently. Both computational design and experimental approaches are employed to facilitate the development of new hardware, software, and processing techniques for SEs. Specifically, we highlight Additive Manufacturing (AM) tools for portable electronic applications and the use of acoustophoresis for manufacturing EV SEs. First, we have developed new computational fabrication tools2 and material formulations to push the bounds of AM for SE fabrication. Through this work, we investigate the impact of electrode design and fabrication on the rate capability and charge performance of Li4Ti5O12 and LiFePO4 cells. Next, taking AM towards larger area fabrication, we have combined acoustophoresis with AM principles to facilitate large-area printing and patterning of SEs for LIBs.3 Acoustophoresis utilizes acoustic standing wavesto drive particles into predefined patterns, with micron-scale control at time scales < 1 second. Our initial results with LiNi0.6Mn0.2Co0.2O2 and graphite have defined process conditions that enable acoustophoretic fabrication of SEs with improved rate capability over conventional, flat LIB electrodes. Our work highlights the material and processing considerations that must be given when developing new manufacturing processes for SEs. References C.-H. Hung, P. Huynh, K. Teo, and C.L. Cobb, “Are Three-dimensional Batteries Beneficial? Analyzing Historical Data to Elucidate Performance Advantages,” ACS Energy Letters, 8 (1), pp. 296–305, 2023.F. Fossdal, V. Nguyen, R. Heldal, C.L. Cobb, and N. Peek, “Vespidae: A Programming Framework for Developing Digital Fabrication Workflows,” In Proc. of 2023 Designing Interactive Systems Conference, ACM, New York, NY, USA.K.E. Johnson, D.S. Melchert, E.N. Armstrong, Daniel S. Gianola, C.L. Cobb, M.R. Begley, “A Simple, Validated Approach for Design of Two-dimensional Periodic Particle Patterns via Acoustophoresis,” Materials & Design, Vol. 232, 112165, 2023. Acknowledgements This material is based upon work supported in part by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Materials and Manufacturing Technologies Office (AMMTO) Award Numbers DE-EE0009112 and DE-EE0010226. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.This work was funded in part by a Defense Advanced Research Projects Agency (DARPA) Young Faculty Award and Director's Fellowship under grant number D19AP00038. The views, opinions, and findings expressed in this work are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government, and no official endorsement should be inferred. This is approved for public release and distribution is unlimited.

Dielectric Bragg Reflector as Back Electrode for Semi‐Transparent Organic Solar Cells with an Average Visible Transparency of 52%

A crucial challenge in the development of semi‐transparent solar cells is to maintain a reasonable power conversion efficiency (PCE) while reaching a high average visible transparency (AVT). Typically, organic semiconductors are favorable for this application since they can selectively absorb infrared light while transmitting visible light. This ability stems from limited electronic states at high(er) energies in contrast to inorganic semiconductors with their typical rise of the absorption coefficient toward higher photon energies. To increase PCE at high AVTs, a series of infrared dielectric Bragg reflectors is developed for semi‐transparent organic solar cells. Using the multi‐layered back electrode (TiO2|SiN|TiO2|AZO|Ag|AZO) with PV‐X Plus as photoactive layer and a metal‐free PEDOT:PSS top electrode, a light utilization efficiency (LUE = AVT × PCE) of up to 4.32% is achieved, together with an AVT of 47.9%. Although the short circuit current and AVT agree well with optical simulations, a low fill factor (FF) and partial shunting limit the overall device performance. Using ZnO and PFN‐Br as additional electron transport layers and modifying the back electrode stack (TiO2|SiO2|TiO2|AZO|Ag|AZO) accordingly leads to an LUE of up to 4.6% with a remarkable AVT of 51.9% and a maximum PCE of 8.79%.

Commercialization Efforts of Capacitive Deionization Technology in Water Treatment Processes

AbstractAlthough capacitive deionization (CDI) technology has been studied intensively for more than 20 years, its commercialization remains in the initial stage, which is partly caused by the insufficient knowledge exchange between academia and industry. This concept reviews multiple scaling‐up efforts in the CDI technology for treating real water streams, following a case‐by‐case fashion. While the cell architecture in pilot scales is limited to the membrane CDI, highlighting the necessary role of ion‐exchange components during scaling‐ups, different ways of electrode stacking, i. e., monopolar and bipolar, are available. The performance indicators of these CDI systems when treating real water streams are summarized to gain insights into industrial practices. Importantly, key discrepancies in cell components and performances between pilot‐scale and lab‐scale studies are emphasized. The main challenges in large‐scale CDI systems for industrial purposes are discussed, providing hints for a better integration of research and applications.

A structural battery with carbon fibre electrodes balancing multifunctional performance

Structural multifunctional materials have the potential to transform current technologies by implementing several functions to one material. In a multifunctional structural battery, mass saving and energy efficiency are created by the synergy between the mechanical and electrochemical properties of the material's constituents. Consequently, structural batteries could e.g. mitigate electric vehicle overweight or enable thinner portable electronics. This requires combining the best composite and battery manufacturing practices. In the present work this is achieved through the infusion of a stack of carbon fibre-based electrodes with a hybrid polymer-liquid electrolyte. The realised full cell structural battery is based on carbon fibre electrodes with a lithium iron phosphate (LiFePO4) coating on the positive side. This battery laminate shows a very good balance between energy density, stiffness and strength of 33.4 Wh/kg, 38 GPa and 234 MPa, respectively. To push these performances further, different improvement strategies are discussed, and the results are compared with previously published target performances. Ultimately, we demonstrate the feasibility of designing and manufacturing all-fibre solid-state structural batteries as a material solution for future lightweight electric commodities.

Contact‐Engineering of Self‐Aligned‐Gate Metal Oxide Transistors Processed via Electrode Self‐Delamination and Rapid Photonic Curing

AbstractMetal oxide thin‐film transistors (TFTs) offer remarkable opportunities for applications in emerging transparent and flexible microelectronics. Unfortunately, their performance is hindered by limitations associated with parasitic effects, such as parasitic electrode overlap capacitances and high contact resistance, which can severely limit their dynamic behavior. Here, an innovative method is reported to fabricate coplanar self‐aligned‐gate (SAG) indium‐gallium‐zinc‐oxide (IGZO) transistors with engineered source/drain contacts. The manufacturing process starts with the deposition and patterning of a gate electrode/dielectric stack and its functionalization with an organic self‐assembled monolayer (SAM) as the surface energy modifier. A second gold (Au) electrode is subsequently deposited over the gate electrode stack. The overlapping region between the two electrodes is removed via self‐delamination under mild sonication, forming perfectly aligned coplanar Au‐Gate‐Au electrodes. Device fabrication is completed with the spin coating of the IGZO precursor, followed by rapid photonic curing. Replacing the gold source/drain contact with bimetallic electrodes such as Au/In and Au/ITO enables a reduction in contact resistance and improves the transistor performance remarkably without increasing manufacturing complexity. The method is highly scalable, robust, and applicable to other semiconductor materials.

Enhanced boron removal without pre-pH adjustment via redox-mediated electrodialysis assisted by ion-exchange resins

Boron presents challenges in desalination owing to its small size and lack of charge. While various methods, such as reverse osmosis, capacitive deionization, and electrodeionization, have been utilized to control boron, they often suffer from high levels of energy consumption and complex processes requiring pH adjustment to generate the charged form of boron. Herein, we introduce a novel approach, i.e., redox-mediated electrodialysis (redox-ED) assisted by ion-exchange resins, aimed at energy-efficient boron control without requiring pH adjustment. Our system displays a remarkable boron removal efficiency of 99% with a low energy consumption of 0.009 kWh/g (0.09 kWh/m3). These results are likely due to the dissociation of water on the surface of the ion-exchange resins, which led to a local pH gradient and reduced systemic resistance through additional ion flux. Furthermore, via techno-economic analysis, the total cost of the redox-ED for boron removal revealed a 50% reduction with the scale-up strategy of electrode stacking, compared to those of traditional EDI systems. Overall, this study demonstrates the new potential of a sustainable boron removal technology without pH adjustment through the redox-ED system assisted by ion-exchange resins, providing an attractive option applicable to the boron removal industry.

Unlocking Maximum Synergy: Screen-Printing Fabrication of Heterostructured Microsupercapacitor Stacks.

A cost-effective and scalable approach for the fabrication of heterostructured microsupercapacitors (MSCs) employing screen-printing followed by sequential electrochemical and microspray deposition techniques has been demonstrated. The microsupercapacitor electrode (MSC) that composed of stacked layers of mesoporous carbon, polyaniline (PANI), and MXene hold significant promise for wearable electronics. By adjusting the deposition and spray cycles, the MSC can be readily coated with PANI and MXene. The sequentially stacked two layers of MXene and PANI on the mesoporous carbon spheres (PMPM-MSC) yielded a specific capacitance of 1003 mF cm-2 at 0.5mA cm-2, surpassing the performance of PANI/mesoporous carbon electrode by 1.6 times (771 mF cm-2). After 10,000 cycles of charge and discharge, PMPM-MSCs retained more than 86% of their initial capacitance. In-situ Raman spectroscopy confirmedthe synergistic effects between MXene and PANI within the heterostructured stacked PMPM-MSC electrodes, including enhanced electronic conductivity and improved electrolyte ion dissociation, which aligned with the electrochemical measurement results, such as fast charge/discharge rates and reduced internal and mass transport resistance. This study demonstrates the potential of screen-printed heterostructured MSC stacks with maximum electrochemical synergy for portable and wearable energy storage devices.

Scaling Supercapacitive Swing Adsorption of CO2 Using Bipolar Electrode Stacks.

Supercapacitive swing adsorption (SSA) modules with bipolar stacks having 2, 4, 8, and 12 electrode pairs made from BPL 4 × 6 activated carbon are constructed and tested for carbon dioxide capture applications. Tests are performed with simulated flue gas (15%CO2 /85%N2) at 2, 4, 8, and 12V, respectively. Reversible adsorption with sorption capacities (≈58 mmol kg-1) and adsorption rates (≈38 µmol kg-1 s-1) are measured for all stacks. The productivity scales with the number of cells in the module, and increases from 70 to 390 mmol h-1 m-2. The energy efficiency and energy consumption improve with increasing number of bipolar electrodes from 67% to 84%, and 142 to 60 kJ mol-1, respectively. Overall, the results show that SSA modules with bipolar electrodes can be scaled without reducing the adsorptive performance, and with improvement of energetic performance.

Lithium loss, resistance growth, electrode expansion, gas evolution, and Li plating: Analyzing performance and failure of commercial large-format NMC-Gr lithium-ion pouch cells

Analysis of the performance evolution and failure mechanisms of commercial Li-ion batteries is crucial for improving testing methods, accurately modeling battery performance, and ensuring safe battery operation. Here, we present the results of a 2-year aging study conducted on commercial large-format LiNiMnCoO2-graphite pouch cells. Loss of lithium inventory (LLI) and loss of positive electrode active material (LAMPE) are shown to dominate capacity fade, as quantified by differential voltage-capacity analysis; only a small amount of LAMPE was measured in extracted electrode material, indicating that LAMPE in full cells was due to electrode dry-out. Resistance evolution, observed by direct current pulses and electrochemical impedance spectroscopy analyzed using the distribution of relaxation times, shows complex trends. Particle cracking and electrode expansion is theorized to cause most changes to resistance. Post-mortem measurements reveal a 10% increase in electrode stack thickness and substantial gas generation, with lithium plating observed in extreme cycling conditions, causing large resistance increases. Circumstantial evidence for self-discharge via redox shuttle, which decomposes the electrolyte, is shown. Overall, electrolyte stability was determined to be the limiting factor for cell lifetime. The impacts of many degradation mechanisms on diagnostic signals substantially overlap, making it challenging to monitor cell health and safety.

Cryo-Electron Microscopy Reveals Na Infiltration into Separator Pore Free-Volume as a Degradation Mechanism in Na Anode:Liquid Electrolyte Electrochemical Cells.

Batteries utilizing a sodium (Na) metal anode with a liquid electrolyte are promising for affordable large-scale energy storage. However, a deep understanding of the intrinsic degradation mechanisms is limited by challenges in accessing the buried interfaces. Here, cryogenic electron microscopyof intact electrode:separator:electrode stacks is performed and degradation and failure of symmetric Na||Na coin cells occurs through the infiltration of Na metal through thepores of the separator rather than by mechanical puncturing by dendrites is revealed. It is shown the interior structure of the cell (electrode:separator:electrode) must be preserved anddeconstructing the cell into different layers for characterization results in artifacts. In intact cell stacks, minimal liquid is found between the electrodes and separator, leading to intimate electrode:separator interfaces. After electrochemical cycling, Na infiltrates into the pore free-volume, growing through the separator to create electrical shorts and degradation. The Na infiltration occurs at interfacial regions devoid of solid-electrolyte interphase (SEI), revealing SEI plays an important role in preventing Na from growing into the separator by being a physical barrier that the plated Na cannot penetrate. These results shed new light on the fundamental failure mechanisms in Na batteries and demonstrate the importance of preserving the cell structure and buried interfaces.

High‐rate metal‐free MXene microsupercapacitors on paper substrates

AbstractMXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors (MSCs). Despite its superior electrochemical performance, only a few studies have reported MXene‐based ultrahigh‐rate (&gt;1000 mV s−1) on‐paper MSCs, mainly due to the reduced electrical conductance of MXene films deposited on paper. Herein, ultrahigh‐rate metal‐free on‐paper MSCs based on heterogeneous MXene/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS)‐stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing. With a footprint area of only 20 mm2, the on‐paper MSCs exhibit excellent high‐rate capacitive behavior with an areal capacitance of 5.7 mF cm−2 and long cycle life (&gt;95% capacitance retention after 10,000 cycles) at a high scan rate of 1000 mV s−1, outperforming most of the present on‐paper MSCs. Furthermore, the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal‐free on‐paper MSC arrays, which can also be simultaneously charged/discharged at 1000 mV s−1, showing scalable capacitive performance. The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on‐paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics.

Direct-spun carbon nanotube sheet: A flexible, ultralight, stackable three-dimensional current collector for high-performance lithium-ion batteries

Among the key components of a battery electrode, current collectors hold significant importance for the energy density of lithium ion batteries (LIBs) as metal foils account for a significant proportion of the total mass. Carbon nanotube sheet (CNTS) has garnered considerable attention because of its fascinating material features such as high electrical conductivity, low density, and excellent flexibility. In this study, we demonstrate the utilization of a direct-spun CNTS as a current collector in order to enhance the electrochemical performance and replace the conventional current collector, that is, aluminum (Al) foil, in LIBs. When the CNTS coated with NCM811 (NCM811/CNTS) is evaluated in LIBs, it delivers superior rate capability and cycle stability compared with Al foil-based and buckypaper-based NCM811 electrodes. It is because the CNTS with a large surface area and high electrical conductivity establishes a number of electronic pathways to the cathode electrode. In addition, the porous structure of the CNTS efficiently enhances the adhesive properties of the electrodes. Due to the synergistic benefits of CNTS, cells with stacked NCM811/CNTS electrodes are successfully fabricated. Electrode stacking with multiple NCM811/CNTS electrodes exhibits improved areal capacity and stable cycle stability, suggesting a new strategy to replace the concept of conventional thick electrodes. Moreover, pouch cells with LTO/CNTS as an anode and NCM811/CNTS as a cathode display stable electrochemical performance even under mechanical deformation (e.g., folding/unfolding)

Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition

Developing new electrode materials or electrolytes for lithium-ion batteries requires reliable electrochemical testing thereof. In academic research, coin-type cells and small pouch-type cells are commonly being assembled for this purpose. In our study [1], using commercial highly homogeneous and robust LiNi0.33Mn0.33Co0.33O2 (NMC111) cathodes, graphite anodes and 1M LiPF6 in EC/DMC with 3% VC as the electrolyte, four experienced researchers from the Institute for Applied Materials at Karlsruhe Institute of Technology assembled a variety of coin cells within a round robin test. For different cell building parameters, the battery lifetimes systematically varied from a few hundred to well over 2000 cycles before a capacity retention of 80 % was reached. As a benchmark, the same electrodes and electrolyte were incorporated as single- and multi-layer electrode stacks into pouch-type cells and reach almost 4000 cycles with a rate of 1 C.Missplacing of electrodes and varying amount of electrolyte within a coin-cell were already addressed as performance influencing factors in the literature. In this study, one clear outcome with high impact on previously collected electrochemical data on coin cells, is that the steel grade of cell parts, as well as the in-housed total height of the electrode stack have dramatic influence on cell lifetime and the quality of the acquired electrochemical data. We present our best practice for coin cell manufacturing resulting from the round robin test. Further, it is shown that inappropriate testing conditions like poor cell contacting and cycler settings have additional impact on data collection. In this regard, we emphasize essential parameters for obtaining high quality data.Additionally, using the same electrodes, we show direct rate performance differences of calendered vs. uncalendered electrodes, as well as half vs. full-cell test results by means of rate capability and long-term cycling stability. While compression of anodes is less crucial for rate capability, substantial differences are measured in case of the cathodes, highlighting the importance of sufficient cathode densification. Moreover, for long-term capacity retention studies, it is demonstrated that electrode densification of both, cathode and anode is crucial for high long-term capacity retention.Our results are bridging the gap between lab research and industry-type battery cells. It is shown how key performance parameters can be projected from corresponding lab scale battery cell data, if certain important criteria are met vs. where the projections have their limits.[1] A. Smith, P. Stüble, L. Leuthner, A. Hofmann, F. Jeschull and L. Mereacre, Batteries & Supercaps 2023, e202300080. Figure 1

Improving Lithium-Ion Batteries By Replacing Polyethylene Terephthalate Jellyroll Tape

Every lithium-ion battery cell produced today that is either wound or stacked contains tape. This tape serves the mechanical purpose of holding together the wound jellyroll or stacked electrodes before inserting it into the cell casing, after which the tape serves no purpose. Battery manufacturers often test inactive cell parts for their physical parameters, i.e., elongation, water absorption, and temperature resistance.1 However, their chemical stability is often overlooked. Recently, it was demonstrated that polyethylene terephthalate (PET) tape can partially dissolve in the harsh lithium-ion battery cell chemistry into its monomer dimethyl terephthalate (DMT). This molecule can act as an unwanted redox shuttle in LFP/graphite or NMC811/graphite cells, inducing self-discharge of the battery.2 Figure 1 shows Fourier-transform infrared (FTIR) spectra of tapes obtained from discarded cellphone batteries. Many well-known lithium-ion battery producers use PET tape in their products. In addition, the FTIR spectra show that after the cells have been cycled, the surface layer of these tapes is severely corroded. This study will show open circuit storage, Ultra-High Precision Coulometry, and long-term cycling results from LFP/graphite cells with PET tape. The study will also show how swapping PET tape for a more stable alternative can significantly improve the performance and reduce the self-discharge of LFP/graphite pouch cells.Figure caption: Figure 1 . FTIR spectra of jellyroll closing tapes (a) extracted from discarded cellphone batteries (b).

Online Electrochemical Mass Spectrometry on Large-Format Li-Ion Cells

Significant progress has been made in real-time analysis methodologies for batteries, particularly with regards to the development of Operando Electrochemical Mass Spectrometry (OEMS) [1]. OEMS provides unprecedented selectivity and sensitivity in analysing the release of volatile species, enabling the detection of side reactions during battery cycling which can provide crucial information about the Solid Electrolyte Interface (SEI) and processes that limit battery life. However, most research thus far has been conducted on model battery systems (~1 mAh) that do not accurately reflect conditions within large-format commercial cells (~10,000 mAh) particularly in terms of electrode areas, electrolyte volumes, and stack pressures. Additionally, the atmosphere within the cell is altered through either continuous flow [2] [3] (in the open approach) or purging [4] (in the semi-closed approach [5]). In both cases, gas is being withdrawn from the cell (10% of cell volume/measurement point) during operation and replaced with a carrier gas (usually Ar). This dilutes the existing environment and prevents further reactions, making it difficult to compare the results to real-life situations.In this work, the development and validation of an entirely closed OEMS system that can be interfaced with large-format commercially available batteries is showcased. Instead of replacing the removed gas, a small amount (0.2 % of cell volume/measurement point) is periodically removed, causing a gradual pressure drop in the cell. Experiments are limited by a minimum internal cell pressure of 700 mbar due to the sensitivity of the pressure sensor and vapour pressures of the electrolyte. Apart from this pressure drop, the internal cell environment is therefore relatively constant allowing us to observe side reaction products that have occurred within a realistic cell environment.We additionally provide a detailed description of an adapter design for interfacing large format prismatic cells with our intermittently closed OEMS (ICEMS) setup. The adapter is placed over a hole in the cell (produced with a drill) and can be easily scaled for different cell geometries. Using this ICEMS setup, we provide operando pressure and gassing data from a calendared BAK PHEV2 cell. The pressure within the cell changes depending on the level of lithiation in the cathode (NMC) and anode (graphite), revealing the multiple phase transitions that occur in both materials during cycling. These transitions can be divided into four regions of interest, where graphite dominates regions I and III (with large pressure increases during charge) and NMC dominates regions II and IV (with pressure decreases during charge). By analysing the gas produced during these transitions, it is clear that structural changes within both electrodes result in side reactions. When graphite undergoes large volume changes (from 1L to 2L and 2 to 1, regions I and III), H2 and C2H4 are released as SEI reformation products, while the c lattice collapse in NMC (during the H2 to H3 transition, region IV) results in CO2 evolution (through O2 release that subsequently reacts with the electrolyte). In addition, we suggest that Lewis bases formed on the graphite through the reduction of electrolyte species ring open EC, forming CO2 [6]. The results of this study suggest that the internal chemistry of commercially available prismatic rechargeable batteries can be studied effectively using ICEMS without significantly altering the battery's chemistry.[1] A. M. Tripathi, W. N. Su, and B. J. Hwang, “In situ analytical techniques for battery interface analysis,” Chem. Soc. Rev., vol. 47, no. 3, pp. 736–751, 2018, doi: 10.1039/c7cs00180k.[2] P. Novák et al., “Advanced in situ characterization methods applied to carbonaceous materials,” J. Power Sources, vol. 146, no. 1–2, pp. 15–20, 2005, doi: 10.1016/j.jpowsour.2005.03.129.[3] N. Tsiouvaras, S. Meini, I. Buchberger, and H. A. Gasteiger, “ A Novel On-Line Mass Spectrometer Design for the Study of Multiple Charging Cycles of a Li-O 2 Battery ,” J. Electrochem. Soc., vol. 160, no. 3, pp. A471–A477, 2013, doi: 10.1149/2.042303jes.[4] R. Lundström and E. J. Berg, “Design and validation of an online partial and total pressure measurement system for Li-ion cells,” J. Power Sources, vol. 485, no. December 2020, 2021, doi: 10.1016/j.jpowsour.2020.229347.[5] L. A. Kaufman and B. D. McCloskey, “Surface Lithium Carbonate Influences Electrolyte Degradation via Reactive Oxygen Attack in Lithium-Excess Cathode Materials,” Chem. Mater., pp. 1–7, 2021, doi: 10.1021/acs.chemmater.1c00935.[6] N. Gogoi et al., “Silyl-Functionalized Electrolyte Additives and Their Reactivity toward Lewis Bases in Li-Ion Cells,” Chem. Mater., vol. 34, no. 8, pp. 3831–3838, 2022, doi: 10.1021/acs.chemmater.2c00345.

Present and Future Perspectives on Fuel Cell Membrane Chemical Stability

Durability is key to the value proposition of proton exchange membrane (PEM) fuel cells for transportation applications. Ultimately, fuel cell vehicles need to match the lifetimes of diesel powered trucks, and last longer than lithium batteries, for widespread adoption[1]. The burden of reaching these aggressive targets falls on all components of the system, stack, and membrane electrode assembly. Of these, membrane durability remains an important area of research, in particular the chemical stability of the ionomer. The recognition of the ‘simple unzipping’ of the perfluorosulfonic acid (PFSA) backbone by hydroxyl radicals (HO·)[2],[3] and the subsequent introduction of cerium radical scavengers[4],[5] mark significant advancements in fuel cell lifetimes. Yet, even with this technology, it is unclear if this class of membranes can meet the 25,000+ hours required for heavy duty applications without additional improvements. Furthermore, recent proposals to restrict usage of fluorochemicals in many applications[6] presents a risk to the rapidly growing PEM fuel cell and water electrolysis markets. This talk will outline recent work that looks beyond simple peroxide degradation of PFSA ionomers and highlight the role of other reaction mechanisms suspected in accelerated fuel cell durability testing. Analysis of effluent water for ionomer fragments during these tests provides a greater understanding of the degradation mechanisms and suggests additional pathways beyond back-bone unzipping. Not only are these fragments useful in inferring reaction mechanisms, but there is also evidence they adsorb to the platinum surface, ultimately adding to performance decay. In other words, increased membrane durability may also result in increased catalyst stability. Finally, chemical stability of hydrocarbon membranes will be considered in light of the advances over the last two decades in understanding PFSA stability. Similarities and differences will be discussed between these two classes of PEM membrane with suggestions on how the techniques used to understand PFSA stability could be applied to hydrocarbon ionomers and advance the understanding of chemical stability in these systems.[1] Cullen, D. A.; Neyerlin, K. C.; Ahluwalia, R. K.; Mukundan, R.; More, K. L.; Borup, R. L.; Weber, A. Z.; Myers, D. J.; Kusoglu, A. New Roads and Challenges for Fuel Cells in Heavy-Duty Transportation. Nat Energy 2021, 6 (5), 462–474. .[2] Curtin, D. E.; Lousenberg, R. D.; Henry, T. J.; Tangeman, P. C.; Tisack, M. E. Advanced Materials for Improved PEMFC Performance and Life. Journal of Power Sources 2004, 131 (1), 41–48.[3] Coms, F. D. The Chemistry of Fuel Cell Membrane Chemical Degradation. ECS Trans. 2008, 16 (2), 235.[4] Frey, M. H., Pierpont, D. M., Hamrock, S. J., US 8,367,267 and US 9,431,670[5] Coms, F. D.; Liu, H.; Owejan, J. E. Mitigation of Perfluorosulfonic Acid Membrane Chemical Degradation Using Cerium and Manganese Ions. ECS Trans. 2008, 16 (2), 1735.[6] European Chemicals Agency (ECHA) proposal submitted 7th February 2023

Non-Equilibrium Nitrate Detection in Ionophore-Based Solid-Contact Ion-Selective Electrodes

Ion-selective electrodes (ISE’s) have benefits for solution-phase detection and quantification of ions, such as ease of operation, low cost, and high throughput compared to, e.g., ion chromatography or mass spectrometry methods. ISE devices are traditionally operated under zero-current conditions, where analyte ions passively exchange across a selective membrane barrier, yielding a Nernstian response after equilibration of Coulombic and chemical driving forces across the membrane. However, this passive mode of operation can require long equilibration times and lead to drift, for example due to electrolyte leakage and pH impacting the membrane and reference electrode. In recent years, non-equilibrium detection techniques have been of growing interest, where the ISE signal is obtained under applied electrical signal. However, the majority of this work has been devoted to cation sensing, with relatively few studies examining anion ISEs under active electrical actuation. Agricultural expansion and the corresponding uptick in application of supplemental nitrogen to soil has led to an increased demand for technologies to measure anions like nitrate – both from a production and regulation standpoint. In this work, we employ galvanostatic polarization of solid-contact ISEs as a non-equilibrium nitrate detection method. Our investigation involves coating electrodes with a redox-active charged polymer to act as a transduction layer to convert ionic to electronic signal, followed by solvent casting of a polymeric ion-selective membrane. We examine the impact of repeated rapid charging and discharging ISE electrode stacks on measurement time and stability. We compare the metrics derived from this technique to conventional open-circuit measurements using the same device. We identify benefits for this mode of operation using established nitrate membrane materials (e.g. nitrate ionophore VI membrane cocktail) that address some of the typical limitations of these conventional materials and we discuss opportunities for further refinement.