bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Tuning of the MPL’s Cracked Area for Optimizing the Performance of Polymer Electrolyte Fuel Cells
Authors: Galante Bruno , Herranz Juan , Buechi Felix N. , Gilardi Raffaele , Guglielmi Angelo , Buades Begona , Eller Jens
Published: December 2024

The cracks in Micro Porous Layers (MPL) can have a significant impact on the performance of Polymer Electrolyte Fuel Cells (PEFCs) [1–4]. For such a reason, the interest in researching and understanding the crack formation processes, as well as studying their final morphology, is rapidly increasing [2-4]. In this contribution, we propose a method for tuning the MPL’s cracked area and an analysis of the superficial and intersected cracks through a combination of optical microscopy, XTM (X-ray Tomographic Microscopy), and image processing. An example of optical images of MPLs with different cracked areas and the results of the segmentation process applied to them is reported in the Figure. After segmentation, the calculation of the cracked area yields values of about 4.5%, 1%, and < 0.1%, respectively, for the images in the Figure. By having good control and thorough characterization of the cracked area, we target a conclusive correlation between the cracked area and fuel cell performance. This is made possible by testing the cells in dry and wet conditions and by analyzing how the polarization curve and the oxygen transport resistance vary for MPLs with different amounts of cracked areas. In such a way, we aim to answer two questions: “Are the cracks beneficial for fuel cell performance?”; and most importantly: “What is the amount and type of cracks that optimize the fuel cell performance?”.

References:

Z. Chen et al. “Crack evolution during the film drying process of fuel cell microporous layer ink.” In: Colloids and Surfaces A - Physicochemical and Engineering Aspects 650.129283 (2022).

J. Dai et al. “Analysis on the influence of crack structure on MPL transmission properties.” In: Journal of Power Sources 562.232790 (2023).

S. Wang et al. “Enhancing the properties of water and gas management for proton exchange membrane fuel cells via tailored intersected cracks in a microporous layer.” In: Journal of Power Sources 533.231402 (2022)

Z. Chen et al. “Interrelation between ink viscoelasticity and crack structure of fuel cell microporous layer.” In: Fuel 360.130629 (2024).

Figure 1
Method for Precise Oxygen Resistance Analysis in Polymer Electrolyte Membrane Fuel Cells Under Various Operating Conditions
Authors: Chun Hyunsoo , Lee Youngseop , Kim Jiwoong , Chang Jung Hyo , Kim Jin Young , Min Kyoungdoug
Published: December 2024

The simultaneous changes occurring in the internal materials of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) under dynamic operating conditions make characterizing the inherent resistance of each material under different operating conditions highly complex. Therefore, the isolation of the internal resistance of components and the identification of the resistance elements that significantly affect PEMFC performance are essential, but comprehensive studies analyzing the internal resistance under different operating conditions have been scarce.

This study proposes a complex resistance analysis methodology capable of isolating the oxygen resistance of a PEMFC single cell under different operating conditions (relative humidity, temperature, supply gas). The Knudsen diffusion within the catalyst layer is calculated according to the operating conditions using a catalyst agglomerate model. This calculation is combined with the dissection of the oxygen transport resistance to distinguish between molecular diffusion, Knudsen diffusion and ionomer film resistance under limiting current density conditions. In addition, an equation has been developed that accurately predicts the ionomer film resistance as a function of changes in temperature and RH, proposing a new approach to mapping ionomer film resistance. Then, by inputting three forms of resistance from the dissection of the oxygen transport resistance analysis as percentages into the distribution of relaxation time analysis, the newly developed methodology gives insight into the contributions of seven different resistance elements at different current densities. This provides an indicator for determining ionomer resistance without the need for temperature and RH experiments. In addition, this research identifies the design of the ionomer within the catalyst layer as a key determinant of PEMFC cell performance, highlighting the significant impact that molecular or Knudsen diffusion can have depending on operating conditions. Consequently, through an in-depth analysis of oxygen stability under different operating conditions, this study will provide essential insights for future PEMFC cell design.
(Invited) In-Situ Liquid Water Visualization in PEFC and Its Application to Advanced Materials
Authors: Hirai Shuichiro , Satoh Keisuke , Sakai Katsunori , Naito Hiroshi , Sasabe Takashi
Published: December 2024

Although water, not carbon dioxide, is the only substance that is exhausted from PEFC, water management inside PEFC is also important to improve its performance. To develop in-situ measurement techniques of water are needed to understand and control water, including water vapor. Authors first made an in-situ measurement by magnetic resonance imaging (MRI) to measure the spatial distribution of the water content within a polymer electrolyte membrane under operation1. This technique is valid for membrane only. It is extended to develop to measure water in gas diffusion layer using soft X-ray2. In-situ observation of liquid water transport in the microporous layer (MPL) and substrate layer of an operating PEFC was performed using high-resolution soft X-ray radiography.

Recently, in order to achieve high current density in PEFCs, we developed thin GDLs to allow sufficient oxygen transport with suppression of concentration overvoltage caused by the liquid water accumulation inside. A thin self-standing GDL that consists of nano-fiber as a substrate layer and MPL is developed. The cell performance was improved in the case of the new GDL at high current density as shown in figure 1 compared to the case of the SGL25BC. Moreover, results of X-ray visualization showed that liquid water accumulation of new GDL was reduced.

Tsushima, Kazuhiro Teranishi, S. Hirai, Electrochemical and Solid-State Letters, 7 , A269-A272 (2004)

Deevanhxay, T. Sasabe, S. Tsushima, S. Hirai, J. Power Sources, 230, 38 (2013).

Ishikawa, R. Aihara, H. Naito, K. Sakai, T. Sasabe, A. Tanioka, and S. Hirai, ECS Transactions, 109, 275 (2022)

Figure 1
Spatially Resolved Analysis of the Influence of Three-Dimensional Flow Field Structures on Loss Processes in PEMFCs
Authors: Oppek Philipp , Raab Sebastian , Weber Andre
Published: December 2024

During operation of large-area polymer electrolyte membrane fuel cells (PEMFCs) under high loads, strong gradients occur along the gas channel and mass transport becomes the performance limiting factor. Towards the gas outlet the concentration of the reactants decreases, while the relative humidity increases and liquid water is formed. Despite these high gradients, the aim is to achieve a high performance over the entire channel length.

The flow field geometry, which controls the distribution of the reactant, the removal of excess liquid water and the electrical contact, has a significant influence on the overall performance and the power density distribution along the channel. Conventionally, channel-rib structures are used, but these are limited in terms of the distribution and transportation of the reactants, especially under high loads.

Due to their specific structure and open geometry, three-dimensional flow structures have an optimized transport of reactants to the active layer as well as removal of water and thus a strongly improved mass transport. At the same time, such structures have a highly reduced contact area, which leads to increased ohmic losses. In order to fully understand the impact on the performance of the cell under different operating conditions, a quantification of the local performance as well as resistances distribution and their dependencies is essential.

For this purpose, we are examining both channel-rib and three-dimensional flow structures using a segmented cell. The performance distribution is determined by the local measurement of current and voltage. The measurement of electrochemical impedance spectra of each segment and impedance data analysis by the distribution of relaxation times (DRT) [1,2,3] enables the local deconvolution of the loss processes.

In this contribution, an experimental analysis of the influence of three-dimensional meshes compared to a channel-rib flow field design on cell performance is presented. In particular, the effects of high loads, high humidities and low oxygen concentrations on the performance and resistances and their distribution along the gas channels are discussed. Based on the physical interpretation of the results, consequences and conclusions for the further development of three-dimensional flow field geometries are drawn.

References:

H. Schichlein et al., J. Appl. Electrochem. 32, pp. 875-882 (2002).

E. Ivers-Tiffée et al., J. Ceram. Soc. Japan 125, pp. 193-201 (2017).

M. Heinzmann et al., J. Power Sources 558, 232540 (2023).
Novel Design of Corrugated Columns for Water Management in a Proton Exchange Membrane Fuel Cell
Authors: Shahzad Hasan , Garcia-Salaberri Pablo A. , Duque Luis , Diaz-Álvarez Ester , Folgado M. Antonia , Chaparro Antonio M
Published: December 2024

Fuel cells have become increasingly acknowledged as an important and sustainable source of energy in recent years. Proton exchange membrane (PEM) fuel cells, which use hydrogen to generate power, are closer to a wide use in stationary, transport, and portable devices. However, water management significantly influences the efficiency and long-term reliability of PEM fuel cells in both convective and passive configurations. This study focuses on investigating a novel cathodic plate design with helicoidally corrugated columns to optimize the water removal from a PEM fuel cell. The plate is equipped with a series of helicoidally corrugated columns to enhance the movement and removal of water droplets from the cathode surface. The analysis is carried out using computational modeling and experimental research for both convective as well as passive PEM fuel cells. The preliminary outcomes of our research demonstrate substantial enhancements in the efficacy of water management, which contributes to the prolonged operational lifespan and improved overall performance of air-breathing PEM fuel cells. The results provide a valuable contribution to enhance the expandability and practicality of air-breathing fuel cell technologies, which has diverse applications for portable electronics.

This work was supported by projects PORHYDRO1 TED2021-131620B-C21/AEI and PORHYDRO2 TED2021-131620B-C22/AEI European Union NextGenerationEU/PRTR, of the Ministry of Science and Innovation of Spain, Spanish Research Council.
Water Transport, Diffusion and Drag in Intermediate Temperature Proton Exchange Fuel Cells
Authors: Nikolic Nikola , Lindbergh Goran , Eriksson Björn , Lindström Rakel Wreland , Lagergren Carina
Published: December 2024

Low-temperature proton exchange membrane fuel cell (PEMFC) systems operating at <80 °C show limitations such as requirements for large cooling systems, employment of expensive catalysts and challenging water management. Operating the PEMFC at intermediate temperatures (80 - 120 °C) would reduce these limitations. As water is a product in the oxygen reduction reaction on the cathode it is important to understand its management at elevated temperatures to avoid flooding or drying out, especially due to exceeding water boiling temperature.

In this work the water transport in PEMFC at 80 – 120 °C is examined by measuring the water content at anode and cathode during operation with sensors at inlets and outlets. This is examined under ambient and pressurized conditions and at relative humidities (RHs) of 40 % and 70 %. The results show that water content at the cathode always increases with rising current due to water production (Figure 1 a). However, the water content at the anode is dependent on the operating condition and is always lower compared to the cathode. Due to water diffusion from the cathode water is also slightly increased on anode at 80 °C, but at 100 and 120 °C negative values at the anode are noted. This means that the water dragged from the anode to the cathode by the migration of protons is larger than the water diffused from cathode to the anode at higher temperatures. This was further evaluated by performing hydrogen pump measurements and elucidated through a physics-based model using COMSOL Multiphysics software. The divergence due to temperature is smaller when the cell is pressurized (Figure 1 b), and negative values at the anode are observed only at 120 °C. Even though the water content is decreasing, the decrease of RH or drying out is never observed at either ambient or pressurized conditions. Water distribution was shown to be unaffected by changing RH of inlet gases, however, the divergence of RH between cathode and anode was not observed at 70 % RH as it is observed at 40 % RH. Overall, it is possible to run the cell at elevated temperatures without danger of drying out at tested pressures and RHs.

Figure 1
Quantitative Chemical State Analysis of Silicon-Based Anodes for Lithium Ion Battery Using X-Ray Emission Spectroscopy
Authors: Takahara Hikari , Shoji Takashi , Kawahara Naoki , Doui Makoto , Kobayashi Hironori
Published: December 2024

The advancement of lithium-ion batteries for electric vehicles has prompted the utilization of diverse materials, including substances like amorphous and sulphated materials, which may lack inherent stability. Consequently, employing various analytical techniques, spectral analysis, and in-operando cell testing becomes imperative for their characterization. We assess the potential of X-ray Emission Spectroscopy (XES) to integrate chemical state and quantitative analysis, capitalizing on its bulk analysis capabilities with large analytical area and deep analytical depth.

Silicon-based anodes offer high theoretical capacities and hold promise for lithium-ion batteries in electric vehicles. However, their practical application is hindered by poor cycling performance and mechanical failure attributed to significant volume changes during lithiation. Understanding the formation of amorphous and crystalline lithium silicon alloy phases, crucial for capacity degradation analysis, underscores the importance of quantifying the x value in the Li
x
Si phase. SiO emerges as a compelling anode material with potential to enhance energy capacity and mitigate degradation. Demonstrating this property involves the complex conversion of SiO to amorphous Si and lithium silicates during charging.

While electrochemical reaction mechanisms and structural changes in silicon-based anodes have been explored using various techniques such as 7Li and 29Si solid-state NMR, Si K XAS, and Si-L2,3 soft X-ray emission spectroscopy, accurately quantifying reacted components remains challenging.

In this study, Si Kβ X-ray emission spectroscopy (XES) is employed to quantify the composition of lithium-silicon alloys and lithium silicates during charging and discharging processes. The Si Kβ spectrum evolves with the reaction progression, and linear combination fitting (LCF) proves instrumental in estimating material quantities based on the reaction formula. The quantitative results of the XES analysis are shown and the accuracy, validity and findings are discussed.
Degradation and Safety Analysis of Large Format LiFePO4/Graphite Battery
Authors: Matsuda Keisuke , Shono Kumi , Kobayashi Yo , Nakamura Tomoyuki
Published: December 2024

Large format LiFePO4/Graphite (LFP/Gr) Lithium-ion battery (LIB) have been developed for electric vehicles (EV) and stationary use. In case of large surface electrodes, intrinsic two-phase reaction of LFP has a risk to induce inhomogeneous reaction in planar electrode surface. We applied >200 Ah class LFP/Gr LIBs and cycled them around 80-65 % SOH levels. Among them, we applied non-destructive differential voltage analysis (dV/dQ) to three cells (Cell1:SOH 80.9 %, Cell2:SOH 73.5 %, Cell3:SOH 68.4 %), and determined the degree of inhomogeneity of the electrodes by disassembly of the cell in the Ar-filled glove box.

We could obtain dV/dQ peak corresponds to Gr 2nd stage single phase by charge curve analysis between SOC 0 and 100 % at C/20. Based on the assumption that Gr capacity is twice of the Gr 2nd stage peak capacity, Gr capacity was sufficiently larger than cell capacity. Therefore, cell capacity fade was not related to the capacity fade of Gr but caused by the shift of the cathode / anode operation window (SOW) due to loss of lithium inventory (LLI) and/or capacity fade of LFP.

After dV/dQ analysis with capacity check, cells were disassembled at 2.5 V, and confirmed LFP and Gr capacity by reassembling coin cells with Li counter electrode. Reassembled LFP/Li cells was discharged to 2 V, and Gr/Li cells were deintercalated to 2.5 V. The subtracted value of these residual capacities, we could estimate SOW capacity. The obtained estimated cell capacity by LFP-SOW showed strong correlation with SOH of cells before disassembly (R=0.98). Therefore, we confirmed that capacity fade of the cell was due to increase in SOW and/or capacity fade of LFP.

To determine the degree of inhomogeneity in electrode planar, we applied XRD to LFP. As LFP reaction proceeds typical two-phase reaction, we can indirectly estimate Li content by estimating ratio of LFP and FePO4(FP). The LFP/FP ratio was optimized by Rietveld refinement of the diffraction peaks in various sampling points of the electrode sheet. We confirmed several macroscale inhomogeneous Li distributions in planar LFP electrode. Li poor area was observed at the beginning and the final edge of the roll electrode. The correlation details between cell SOH and degree of inhomogeneity will be discussed in the presentation.

In addition, we applied two kinds of abuse test, overcharge and forced internal short circuit test by laser spot heating to three cells with different SOH. In case of overcharge, cell was charged at 0.78 C from SOC 100 %. In case of laser heating, pulse laser with 0.5 sec supply / 0.1 sec rest at 2000 W applied to the cell. The difference of the obtained parameters, and correlation with SOH will be discussed in the presentation.
Forecast Li Plating in LiFePO4/Graphite Cells: Proposal and Issues
Authors: Shono Kumi , Kobayashi Yo , Matsuda Keisuke , Nakamura Tomoyuki
Published: December 2024

Lithium-ion battery (LIB) for stationary use is required non-destructive degradation and SOH estimation in operation with sufficient safety and long-term use. We have developed non-destructive and post-mortem analysis for large format batteries. In case of non-destructive analysis, differential voltage analysis (dV/dQ) have been applied for the detection of lithium (Li) plating in operation. In addition, we have introduced Ar-filled glove box specially designed for large format battery disassembly to confirm the capacity fade of cathode / anode materials including Li plating on the anode.

We selected 20 conditions as acceleration tests using cylindrical 26650 type LiFePO4/Graphite (LFP/Gr) cells with nominal capacity of 3.4 Ah. We applied the following four non-destructive approaches to the cells with under 90% SOH to forecast Li plating; i) slope of open circuit voltage (OCV) during galvanostatic interruption of titration technique (GITT), ii) gap of charge end voltage and OCV, iii) Gr capacity estimation using dV/dQ peak to peak (Gr 4th and/or 3rd to 2nd stage) capacity or Gr 2nd stage dV/dQ peak position, and iv) peak height and/or width of dV/dQ at Gr 2nd stage.

In case of OCV monitoring, we focused on OCV trend at Gr 2nd and 1st stage coexisting region (0.5<
x
<1 in Li

x

C6). In the normal reaction, OCV at the region is almost flat due to the two-phase reaction of Gr and also LFP. However, we found the cell with OCV slope at the corresponding region was an indicator to forecast Li plating.

In addition, the gap of charge end voltage and OCV during GITT was also an indicator to forecast Li plating. In such case, we could forecast Li plating by using two charge end voltage and subsequent OCV values at D10% SOC at the region of 0.5<
x
<1 in Li

x

C

On the other hand, Li plating forecast using dV/dQ peak positions (used as an indicator of Gr capacity) could be applied in some cycle conditions but could not be applied other conditions including inhomogeneous capacity fade in operation.

Then we focused on peak height and width of dV/dQ at Gr 2nd stage and found that the trend of its peak shape will be an indicator to forecast Li plating. Furthermore, such forecast can grasp at limited SOC range operation including Gr 2nd stage region. Therefore, it will be a possibility to forecast Li plating in a short time using single dV/dQ profile.

We will report merits and issues of the procedure to forecast Li plating including the evidence of Li plating by post mortem analysis.
In Situ Insights into Cathode Calcination for Predictive Synthesis: Kinetic Crystallization of LiNiO2 from Hydroxides
Authors: Tayal Akhil
Published: December 2024

Calcination is a solid-state synthesis process extensively employed in the industrial manufacturing of cathode materials for batteries. However, achieving predictive control of the process to synthesize high-performance cathodes faces complexities associated with the formation of kinetic intermediates that are often elusive and tend to structurally and chemically evolve towards equilibrium phases.

Herein, we use a combination of correlated in situ synchrotron X-ray diffraction (XRD), X-ray absorption spectroscopy (XAFS) and multiscale modeling to investigate the synthesis of the archetypical nickel-based cathode LiNiO2
via calcination from hydroxides. A multistage non-equilibrium crystallization of intermediates is uncovered, with the process dynamically driven by lithiation. Specifically, Li-intercalation occurs concomitantly with dehydration, resulting in the early emergence of Li-containing layered and rocksalt motifs upon the decomposition of Ni(OH)2 precursor. During the subsequent phase progression, crystal growth of the layered LiNiO2 goes slowly due to lithiation-limited sluggish mass transport, then abruptly accelerates upon full lithiation, while experiencing Li/O loss and structural degradation. These findings have immediate implications for the synthetic optimization of Ni-based cathodes, offering opportunities to tune their structural properties through lithiation control intentionally[1]. Figure 1. shows XRD and XAFS data of nickel hydroxide calcined at different temperature with and without Li source (LiOH.H2O).

Reference:

[1] A. Tayal et al. Adv. Mater. 2024, 2312027

Figure 1
Chemo-Mechanics of Silicon Anodes Via Operando Acoustic Transmission in Solid State Batteries
Authors: Sun Kerry , Thorsteinsson Gunnar , Steingart Daniel A.
Published: December 2024

Silicon (Si) anodes paired with solid electrolytes have recently risen as a promising energy storage solution for energy-dense Li batteries. However, Si lithiation and delithiation can exacerbate electrochemical degradation due to its high mechanical dynamics, especially against a solid electrolyte. In this work, we utilize operando acoustic transmission to probe the chemo-mechanical dynamics of Si. Acoustic transmission utilizes ultrasound propagation to nondestructively monitor the electrode’s chemo-mechanics. The speed of sound through a material is proportional to its Young’s modulus (E) and inversely proportional to density. We show that in an all-solid-state system with a sulfide solid electrolyte, acoustic time of flight is highly sensitive to the mechanical dynamics of Li-Si alloying. We combine operando acoustics with ex-situ techniques such as FIB-SEM and XPS to gain physical insight into the fundamental electrode mechanics. We demonstrate that acoustics time of flight transmission is a useful tool in probing electrode dynamics that give further insight into the degradation modes of next-generation anode materials.

Figure 1
Dynamic Lithium Transport Pathway via Crack Formation in Phase-Separating Materials
Authors: Nam Chihyun , Koo Bonho , Kim Juwon , Chung Jinkyu , Lee Danwon , Song Jaejung , Seo Sungjae , Heo Yumin , Wang Jian , Weigand Markus , Kim Namdong , Lim Jongwoo
Published: December 2024

Degradation of electrode particles during cycling is chemo-mechanically coupled and needs to be systematically investigated for the Li-ion battery development. The effect of Li transport pathway on internal stress and crack formation during cycling remains elusive. The opposite effect of cracked, newly exposed active surface on Li transport pathway alteration, accelerating the chemo-mechanical degradation, also remains poorly known. Using operando scanning transmission X-ray microscopy on [100]-oriented LiFePO4 single particles, we demonstrated that lithium insertion from the edge of the non-cracked particle dynamically generate tensile stress within the particle, thereby initiating crack formation during lithiation. The exposed crack surface acts as a Li (de)insertion hotspot, redirecting Li transport pathway and internal stress-fields. Delithiation process induces the Li-poor phase around the crack, creating tensile stress, propagating the crack, and subsequently exposing fresh surface which serves as active hot-spot. On the other hands, lithiation process induces the Li-rich phases around the crack, creating compressive stress and suppressing crack propagation. Phase-field simulations demonstrate chemo-mechanically interactive loop that lithium (de)insertion pathway determines dynamic tensile/compressive stress distribution, which recursively determines (de)insertion pathway. This study offers insights that can help develop high-performance and long-lasting batteries, as well as cycling protocols that suppress crack formation.

Figure 1
Operando Raman Microscopy Studies on Next Generation Positive Electrode and Electrolyte Materials
Authors: del Campo Eva Maria , Marcinek Marek , Hardwick Laurence J. , Neale Alex R. , Żukowska Grażyna Zofia
Published: December 2024

The growing demand for high-performance Li-ion cells nowadays has encouraged researchers to deeply understand the evolution of the various battery’s components over time. Ageing mechanisms have a great impact on the battery life performance; therefore, a better understanding of these complex processes may allow the prolongation of their useful cycle life. Monitoring the cathode material during battery operation is crucial since it represents the performance-limiting component in most of the LIBs [1]. Particularly, cobalt free lithium transition metal oxides are currently gaining interest as active materials for enabling higher energy density cells. Among them, LiNiO2 presents relatively high capacity and long durability. However, this material suffers from capacity loss and thermal instability at highly de-intercalated states due to its non-stoichiometric composition [2]. The mechanisms involved in the capacity fade remain still unclear making it crucial to understand these processes throughout cycling.

Among the methods available to perform operando measurements for Li-ion electrodes, Raman spectroscopy is well stablished to track structural evolution and chemical composition during charge and discharge [3,4]. With this work, an optimised electrode configuration [5] is presented which enables the monitoring of the different electrode phase transitions over several cycles. The developed methodology is applied for the investigation of LiNiO2 active material as a benchmark to understand the evolution of lithium metal oxides among time. The spectra collection obtained was rapidly analysed via the analysis tool PRISMA [6]. Overall, the ability of operando Raman as a pertinent diagnostic tool to follow electrodes behaviour during commercially relevant cycling conditions is demonstrated.

[1] Matteo Bianchini et al. Angew. Chem. Int. Ed. (2019), 10434-10458, 58 (31).

[2] Edgar Bautista Quisbert et al. Small. (2023) 2300616 19 (30).

[3] Hui et al. J. Am. Chem. Soc.(2022) 9434-9442, 144 (21).

[4] Sole et al. Faraday discussions (2016) 223-231, 72.

[5] Timothy E. Rosser et al, J. Electrochem.
Soc. (2021), 070541 (168).

[6] Flores E et al. Chemistry-methods (2022) 2 (10).
Understanding Local Structure-Activity Relation in Lithium-Ion Cathodes with Solid State NMR: Effect of Dopants, Synthesis and Electrochemical Cycling
Authors: Mallick Subhadip , Park Sohyun , Badami Pavan , Gim Jihyeon , Garcia Juan , Iddir Hakim , Abraham Daniel P. , Croy Jason R. , Dogan Fulya
Published: December 2024

As the need for research and development efforts to enable alternative, sustainable lithium-ion cathode material is increasing, fine-tuning of the cathode composition and local structure has been focused on the use of dopants/ coatings and varying synthesis conditions such as annealing temperature and time. While changing these parameters has been shown to have significant effect on materials performance, the relation of synthesis parameters with local structure and composition and electrochemical activity is an ongoing focus area1. Solid state NMR is an important characterization technique for LIB systems as 6Li and 7Li solid state NMR can directly “see and follow” the Li cations within the structure, providing crucial information on domain structures, lithium local order changes and metal segregation. A multinuclear NMR approach is also crucial to track the dopants and study how/ if the dopants are diffusing into the bulk or remain on the surface as unintended coatings. This work covers an overview of how multinuclear solid-state NMR can be utilized to understand cathode local structure changes with synthesis, and electrochemical cycling, how dopants play a role in transition metal segregation and cathode interphase, and they affect materials performance. The NMR characterization studies focus on lithium-ion cathodes systems including lithium and manganese rich transitional metal oxide cathodes, lithium nickel oxide and nickel manganese cobalt oxides and are assisted by density functional theory calculations in providing a better understanding of the experimental characterization data and therefore local environments, domain structures and dopant effects.

References:

Brandon R., Long, Jason R. Croy, Fulya Dogan, Matthew R. Suchomel, Baris Key, Jianguo Wen, Dean J. Miller, Michael M. Thackeray, Mahalingam Balasubramanian, Chem.Mater.2014, 26, 3565−3572

Dogan F., Long B. R., Croy J. R., Gallagher K. G., Iddir H., Russell J. T., Balasubramanian M., Key B., Journal of the American Chemical Society (2015), 137(6), 2328-2335

Figure 1
Visualizing Solid Electrolyte Interphase Formation in Carbon Nanotube-Based Lithium-Ion Batteries: A Comparative in-Operando Electrochemical Atomic Force Microscopy Study
Authors: Frost Brandon Henry , Miller Thomas Samuel
Published: December 2024

Reducing the impact of the climate crisis is this centuries greatest challenge and requires a global effort. Renewable energy sources are the key to decarbonising our energy systems. Lithium-ion batteries (LIBs) have played a key part in tackling the climate crisis and their continued development is imperative to further reducing the impact. More than ever, researchers are incorporating additives and components into battery electrode materials to enhance their electrochemical behaviour, such as their cyclability, conductivity and capacity retention. Carbon nanostructures as additives have been envisioned to offer solutions to problems associated with volumetric fluctuations as well as low conductivities in some next-generation LIBs.

Carbon nanotubes (CNTs) have been researched since 1991 and are essentially rolled up single or multiple sheets of graphene to produce single-walled CNTs or multi-walled CNTs respectively. The incorporation of CNTs into LIBs enhances conductivity and improves mechanical properties, enabling better tolerance to volume expansion. Despite these benefits, CNTs contribute to an initial irreversible capacity charge loss in the first cycle. Unlike the capacity loss seen in graphitic anodes, the high surface area of CNTs leads to increased electrolyte decomposition, forming the solid electrolyte interphase (SEI). This is essential for stable, long-term cycling. Given the limited understanding of SEI formation and growth in conventional LIBs, the introduction of CNTs further complicates this process.

In this work, in-operando electrochemical atomic force microscopy (EC-AFM) is employed to investigate the evolution of the electrode surface morphology. It can provide real-time information about the changing topography of the electrode surface as the electrochemical environment changes. Thus, processes leading to SEI formation on CNT and CNT:graphite electrodes will be visualised. A comparison is made with graphite:CNT electrodes, revealing a rapid SEI formation on the CNT electrode and a slower one on the graphite:CNT electrode. This demonstrates that the graphite:CNT ratio significantly influences SEI formation and, consequently, electrochemical performance. EC-AFM proves powerful in real-time probing of the effects of changing potential on an electrode surface, highlighting where SEI first nucleates and subsequently grows. This technique facilitates a direct correlation of electrochemical analysis with topographical images, offering invaluable insights into how initial electrochemical processes impact the electrode surface at micro- and nano-scales, applicable across various battery chemistries.
Elucidating 3D Water Distributions in PEM Water Electrolyzers Via Neutron Imaging
Authors: Seip Tess , Lee Jongmin , Zhu Lijun , Ranieri Salvatore , Chadwick Eric Alexander , Krause Kevin , Helfen Lukas , Auvity Bruno , Chevalier Stéphane , Bazylak Aimy
Published: December 2024

A key challenge in polymer electrolyte membrane (PEM) water electrolysis stems from product oxygen bubble accumulation in the titanium (Ti) porous transport layer (PTL), which limits hydrogen production at high current densities. To design the next generation of PTLs with efficient porous structures that enhance bubble removal, obtaining three-dimensional (3D) water and gas distributions in an operating electrolyzer is critical. Previous works have demonstrated that neutron [1,2] and X-ray [3] imaging techniques can be used to quantify gas and water content, but capturing these phenomena with 3D imaging remains a challenge due to low transmission through metallic cell hardware, limitations in spatial and temporal resolutions, and low contrast between reactant water and product gas bubbles.

In this work, we used the high flux neutron beam at the NeXT instrument of the Institut Laue-Langevin to perform operando radiography during electrolysis and to acquire tomography scans of the steady-state water and gas distributions. We designed a custom PEM electrolysis cell with a Ti PTL and serpentine flow field design for neutron radiography and tomography to reveal the water distribution and its evolution in the PTL. To correlate electrochemical losses to reactant distributions, polarization curves and EIS measurements were acquired. Operando radiography was employed to reveal changes in water distributions over time with increasing current density. Additionally, to elucidate the steady-state water and gas distributions at a variety of current densities, neutron tomography was utilized. Within our analysis, we reveal the impact of water and bubble distributions through the PTL on activation, ohmic, and mass transport overpotentials, particularly at the PTL and catalyst layer interface. The insights provided will aid in identifying performance degradation mechanisms and desirable reactant distributions for the next generation of PTL design.

References

J. K. Lee et al., Energy Convers Manag, 226, 113545 (2020)

CH. Lee et al., J Power Sources, 446, 227312 (2020)

S. De Angelis et al., J Mater Chem A Mater, 9, 22102–22113 (2021)
Advanced Durability Evaluation of Proton Exchange Membrane Water Electrolyzer Integrating Solar Variability for Green Hydrogen Production
Authors: SEO Bora , Voronova Anastasiia
Published: December 2024

As the focus on green hydrogen production using renewable energy sources (RES) intensifies, selecting the most suitable RES becomes increasingly important. Solar energy has the advantage of being universally available and minimally dependent on natural topography. However, fluctuations in solar output due to factors such as season and weather lead to repetitive increases and decreases in power, posing a challenge to the components of hydrogen production devices, specifically proton exchange membrane water electrolyzers (PEMWE). Therefore, a precise durability evaluation of PEMWE under fluctuating loads is crucial for assessing the remaining lifespan and determining optimal timing for component replacement. However, existing durability evaluation methods, which often rely on periodic cycling or constant maintenance of current and voltage, fail to accurately capture the complex and intermittent nature of RES power. This presentation introduces a high-resolution “realistic” solar profile as an advanced durability evaluation technique for green hydrogen production. Developed by converting actual solar irradiance data from solar panels into current densities in combination with water electrolysis stack data, this profile facilitates a more nuanced understanding of durability under realistic conditions. Additionally, after applying a long-term durability test using this solar profile, the degradation features of core components (catalyst, membrane, porous transport layer) were systematically analyzed through electrochemical, spectroscopic, and microscopic characterizations, providing valuable insights into degradation and recovery dynamics. Notably, the tests featuring the simulated solar profile showed overpotential recovery during “night” periods, potentially due to the formation of active species and the release of residual gases, underscoring the importance of intermittent zero-load steps. Overall, this durability evaluation technique not only diagnoses the precise condition of solar-powered PEMWE but also offers a rational guideline for the development of core components. Moreover, this technique is expected to be applicable to PEMWEs powered by other RES, such as offshore and tidal power, broadening its utility in the field of green hydrogen production technologies.
Advanced Hydrogen Crossover Characterization: Closing the Mole Balance through Coupled Anode and Cathode Exhaust Analysis
Authors: Wrubel Jacob A , Duarte Ricardo Filipe Paz Moldes , Pomeroy Elias D , Kowal Andrea , Bender Guido
Published: December 2024

Hydrogen crossover in proton exchange membrane water electrolysis (PEMWE) is an unwanted phenomenon that leads to both efficiency losses and safety hazards. This issue is expected to worsen as PEMWE systems move towards thinner membranes and high-pressure operation (two straightforward avenues to reduce operating expenses), as well as high turn-down ratios [1]. To address the safety aspect, next-generation PEM architectures are being developed that include a recombination catalyst (e.g., Pt) to consume the H2, i.e. H2 + O2 → H2O, before it makes its way to the anode exhaust. An accurate method for assessing this recombination rate is necessary to evaluate the performance and optimize the recombination catalyst.

In a previous work, we and others demonstrated that the H2 crossover flux can be calculated by analyzing the H2:O2 ratio of the anode exhaust [2 – 4]. However, some assumptions involved in this analysis are not valid in systems with significant H2 + O2 recombination. To get a full picture of the reactions that take place in such systems, it is necessary to analyze the cathode exhaust. By measuring the rates of hydrogen leaving both anode and cathode and comparing them to Faraday’s law, the amount of H2 being consumed in various recombination reactions inside the cell can be quantified.

Figure 1 shows a schematic of the additions required to our previously reported H2 crossover quantification technique. The top exhaust path (grayed out) shows our earlier method for analyzing the anode exhaust. The bottom exhaust path shows the added method that enables analyzing the cathode exhaust. Both techniques use a GC to analyze and quantify the gas composition. In this presentation we will discuss results that verify the technique using H2NEW’s reference FuGeMEA system. We will further demonstrate how the technique can be applied to membranes with recombination catalysts to assess their crossover mitigation capabilities.

References:

[1] A. Badgett, M. Ruth, and B. Pivovar, Electrochemical Power Sources: Fundamentals, Systems, and Applications Hydrogen Production by Water Electrolysis, Elsevier, 2021, pp. 327–364.

[2] J. A. Wrubel, C. Milleville, E. Klein, J. Zack, A. M. Park, and G. Bender, “Estimating the energy requirement for hydrogen production in proton exchange membrane electrolysis cells using rapid operando hydrogen crossover analysis,” Int J Hydrogen Energy, vol. 47, no. 66, pp. 28244–28253, Aug. 2022.

[3] P. Trinke, B. Bensmann, and R. Hanke-Rauschenbach, “Current density effect on hydrogen permeation in PEM water electrolyzers,” Int J Hydrogen Energy, vol. 42, no. 21, pp. 14355–14366, May 2017.

[4] C. Klose et al., “Membrane Interlayer with Pt Recombination Particles for Reduction of the Anodic Hydrogen Content in PEM Water Electrolysis,” J Electrochem Soc, vol. 165, no. 16, pp. F1271–F1277, 2018.

Figure 1
Atomic Layer Deposition of SnO2 Thin Films As Anticorrosion Layers in Proton Exchange Membrane Water Electrolysers (PEMWE)
Authors: Assaud Loïc , Maslouh Haitham , Bechelany Mikhael
Published: December 2024

The deployment of water electrolysers to generate green hydrogen is a major challenge to decarbonize industry and promote sustainable mobilities. Proton Exchange Membrane Water Electrolysis (PEMWE) is a very attractive technology allowing the production of decarbonized dihydrogen from water molecules at close to ambient temperature (< 100°C), in electrolysers operating at high current densities (>1 A/cm2), compatible with variability of electricity source.

The current limitations of PEM cells concern the porous transport layers (PTL) and the bipolar plates (BPP), particularly in the anodic compartment, which are usually made of titanium because of its resistance against corrosion under the operating conditions of electrolysis [1,2]. However, the highly oxidizing environment of the anode generates a thick oxide layer that passivates the surface of the titanium, resulting in a significant increase of the contact resistance between the elements of the anodic compartment and affecting the overall efficiency of the electrolysis process, while accounting for more than 50% of the total electrolyzer costs. Our multidisciplinary and innovative approach aimed at replacing expensive titanium with stainless steel (316L) - more cost-effective - for BPPs and PTLs which will be coated with protective thin films (SnO2, TiN, TaN) elaborated by atomic layer deposition (ALD) [3]. ALD is a powerful technique allowing to generate highly conformal coatings even on complex substrates such as PTLs, with an accurate control of thickness, chemical composition and structure. In this communication, we will present our first results for optimizing SnO2 thin films grown by ALD on stainless steel 316L and titanium substrates, along with their systematic micro/nano-structural characterization performed by ellipsometry, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, etc. The assessment of the anti-corrosion protection of the coatings was carried out ex-situ through stability and corrosion measurements in an acidic environment similar to that of the PEM's operating conditions. Conductivity measurements of the SnO2 thin films were performed to complete the study.

References:

[1] S. Lædre et al., Int. J. Hydrogen Energy. 42 (2017) 2713–2723.

[2] S. Stiber et al., Energy Environ. Sci. 15 (2022) 109.

[3] M. Bechelany et al., Chem. Mater. 30 (2018) 7368–7390.
Ionomer-Free Near-Zero Gap Anion Exchange Membrane Water Electrolyzer Fabricated By in-Situ Modified Catalyst Coated Membrane Method
Authors: Kong Tae-Hoon , Kwon Youngkook
Published: December 2024

Developing a state-of-the-art anion exchange membrane water electrolyzer (AEMWE) for commercial H2 production remains a great challenge. To enhance the performance and durability of AEMWEs, addressing key limiting factors such as ionomer and internal resistance is essential. The inappropriate use of ionomers in membrane electrode assembly (MEA) fabrication limits the exposure of catalyst-active sites and the transport of gaseous products. Moreover, an unstable phenylic backbone of ionomers oxidizes at high voltages (>2.1 V), causing a localized pH drop at the electrode/electrolyte interface and degrading overall cell performance.[1]

To address these challenges, we developed a novel fabrication method for in-situ deposition of catalyst layers (CLs) directly between anion exchange membrane (AEM) and porous transport layer (PTL) using wet chemical reduction in the AEMWE.[2] This innovative approach enables ionomer-free CL synthesis simultaneously with the fabrication of AEM/CL/PTL-integrated MEAs. This near-zero gap AEMWE exhibited significantly lower cell resistance, compared to AEMWEs assembled by the conventional MEA fabrication methods (catalyst-coated substrate and catalyst-coated membrane), achieving an industrially relevant current density of 1 A cm-2 at a cell voltage of 1.79 Vcell and superior durability over 200 h at 1 A cm-2 in 50 ℃. In addition, it demonstrated the current density of 500 mA cm-2 at a cell voltage of 1.913 Vcell and a low degradation rate of 0.58 mV h-1 for 260 h in continuous electrolysis at a current density of 250 mA cm-2 at 50 °C in feeding ultrapure water.

Furthermore, understanding the degradation mechanisms of each MEA component under operating conditions is crucial for improving stack performance and durability. By integrating the reference electrode in AEMWEs, the degradation of the cathode, anode, and membrane under different electrolyte feeding systems will be discussed.

Reference

[1] D. Li, I. Matanovic, A. S. Lee, E. J. Park, C. Fujimoto, H. T. Chung, Y. S. Kim, ACS Appl. Mater. Interfaces, 11, 10, 9696 (2019).

[2] T. H. Kong, P. Thangavel, S. Shin, S. Kwon, H. Choi, H. Lee, N. Park, J. J. Woo, and Y. Kwon, ACS Energy Lett., 8, 11, 4666 (2023).