Anodic Layer Research Articles

Effects of Composition and Texture of Ti Alloys on the Anodic Growth of Nanotubular Oxide Layers

Anodization has been used to fabricate nanoporous and nanotubular oxide layers on many metals and alloys. Solution chemistry is one of the important factors that affect the growth of the layers. On the other hand, metallurgical aspects have been also examined. In the present work, effects of composition and texture on the growth of anodic nanotubular oxide layers are examined, in particular Ti alloys are focused.

Performance and Durability Evaluation of Anion Exchange Membrane Water Electrolysis Cells Using Non-Precious Metal Catalysts and a Hydrocarbon-Based Electrolyte

Anion exchange membrane water electrolysis (AEMWE) is operated in an alkaline environment and has a similar membrane-electrode assembly (MEA) structure to that of proton exchange membrane water electrolysis (PEMWE). The use of nonprecious metals as the electrocatalysts and operation at high current densities are inherently possible, so they are expected to be low-cost, high-performance candidates for next-generation water electrolysis systems.1 However, for practical use, high durability versus large load fluctuations, as well as even higher current densities, are required. In this study, with the aim of achieving high durability and high current density for AEMWE, we used Ni0.8Co0.2Ox 2 and Ni0.8Fe0.2Ox,3 which were developed at the University of Yamanashi (UY), as anode catalysts, and QPAF-44, a hydrocarbon-based electrolyte, which was also developed at UY, as the electrolyte membrane and binder.The catalyst inks for the anodes were prepared by mixing the Ni0.8Co0.2Ox catalyst (UY) or Ni0.8Fe0.2Ox catalyst (UY) with solvent (water/methanol) and QPAF-4 (IEC = 1.5 meq. g-1, UY) binder solution. The anode inks were coated by using pulse-swirl-spray (PSS, Nordson) on the QPAF-4 membranes (thickness 50 μm, IEC = 1.5 meq. g-1) to make the catalyst-coated membranes (CCMs) with the anode. The catalyst ink for the cathodes was prepared by mixing Pt/CB catalyst (TEC10E50E, Tanaka Kikinzoku) with solvent (water/methanol) and QPAF-4 (IEC = 1.5 meq. g-1) binder solution. The cathode ink was coated by using PSS on the opposite side of the CCM. Ni mesh (Bekaert.co.jp) and carbon paper (TGP-H-120, Toray) were used for the anode and cathode porous transport layers (PTLs) respectively. The single cell (Figure 1, cell structure developed by Yokohama National University) performances were measured while supplying 1 M KOH at 80 °C to both electrodes. The durability of these cells was tested by cycling between high electrolysis load (4 A cm-2, 10 s) and no electrolysis (0.1 V, 10 s) for 2000 cycles. Here, the no electrolysis mode is designed to simulate a situation where the anode potential drops to near 0 V due to hydrogen leakage from the cathode when the water electrolysis is stopped for a long time.Figure 2a shows the cell voltage at 4 A cm-2 of the cells using the Ni0.8Co0.2Ox catalyst or Ni0.8Fe0.2Ox catalyst for the anode and Pt/CB for the cathode. During 2000 cycles, the cell with Ni0.8Co0.2Ox catalyst showed a gradual increase in cell voltage. On the other hand, the cell with Ni0.8Fe0.2Ox catalyst showed no significant increase in cell voltage and maintained a cell voltage of less than 2 V during 2000 cycles. Figure 2b shows the I-V performance of these cells after 2000 cycles. The cell with Ni0.8Fe0.2Ox catalyst showed higher I-V performance than that of the Ni0.8Co0.2Ox catalyzed cell even after 2000 cycles, achieving a cell voltage of 1.96 V at a current density of 4 A cm-2. These results indicate the usefulness of Ni0.8Fe0.2Ox catalyst using Fe as a substitute material for the low-abundance metal Co and the possibility of further gains in high current density for AEMWE. Acknowledgement This work was partially based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO) and on GteX Program Japan Grant Number JPMJGX23H2. References 1) H. A. Miller et al., Sustain. Energy Fuels, 4, 2114 (2020).2) G. Shi et al., ACS Catal., 12, 14209 (2022).3) G. Shi et al. ACS Omega, 8, 13068 (2023).4) H. Ono et al., J. Mater. Chem. A, 5, 24804 (2017). Figure 1

Fabrication of Dense Electrolyte for Metal-Supported Solid Oxide Fuel Cells By Plasma Spray Method

Metal-supported SOFCs (MS-SOFCs) have attracted attention because of their potential for low cost and high mechanical robustness. However, the conventional cell fabrication process is not easily applied to MS-SOFCs. The difficulty of MS-SOFC fabrication is especially to form a dense electrolyte without oxidation and diffusion of the metal support. We’ve tried to use a plasma spray method to prepare the metal supported cells. Then, apparently dense electrolyte layer could be fabricated using doped lanthanum gallate instead of yttria stabilized zirconia. In this paper, electrochemical performance and gas tightness of the cells were evaluated to consider the applicability of plasma spray for MS-SOFC fabrication.A prepared MS-SOFC consists of porous metal substrate (SUS430), NiO-YSZ anode, Sr-, Mg-doped lanthanum gallate (LSGM9182), and conventional cathode (LSCF6428). The cell components, except for the porous substrate, were deposited by atmospheric pressure plasma spray (APS). Gas tightness of the cell was confirmed by open circuit voltage (OCV) measurement. Cell performance was evaluated by current-voltage measurement and impedance measurement. Post-analysis of the cell was conducted by SEM/EDS.The measured OCV was confirmed to be equivalent to theoretical value in humidified hydrogen at 973 K. It means the fully dense electrolyte layer could be prepared by plasma spray. Current density of I-V measurement was 0.6 Acm-2 at 0.5 V at 973 K. The impedance results showed larger over potential of anode reaction. This might be caused by anode electrochemical reaction and gas diffusion through anode and substrate layer. Further development of plasma spray anode is necessary for practical application; however, this study confirmed the possibility of the plasma spray method to fabricate the dense electrolyte for MS-SOFCs.This research was financially supported by NEDO.

Lithium–Sulfur Solid-State Electrolyte (Polymers, Oxides and Sulfides) Batteries with a High-Loading Polysulfide Cathode

Introduction Since the introduction of lithium-ion batteries in 1990, the steady growth in volume and performance of lithium-ion cell components and batteries has demonstrated their strong demand in the high-energy-density energy-storage market. The commercial lithium-ion cells adopt the stable intercalation reaction to enable the reversible insertion of lithium ions between layered oxide cathodes and graphite anodes, resulting in the high energy density (100–350 Wh kg–1) and long-term cycling capability (1,000 cycles) that outperform other rechargeable batteries. However, after three decades of research, the charge-storage capacities of the electrode active materials are approaching their theoretical values (200–300 mAh g–1), while the cost of the electrode continues to increase. This limits the improvement of the energy density of lithium-ion cells, which has reduced the annual growth rate from 7% to 2%, making it difficult to supply the energy-storage market of more than 1,500 GWh in 2030. In response to these challenges, next-generation batteries are being developed, focusing on electrochemical cells to achieve high reversible energy storage and competitive prices and solid-state electrolytes for enhanced stability and improved energy density. Both developments aim at achieving new energy density records (300–500 Wh kg–1 and 700–800 Wh L–1) that would enable electric vehicles to surpass conventional vehicles in range, while reducing cell costs. Results and Discussion In this presentation, we will present the designs of the next-generation rechargeable cells aimed at overcoming the bottleneck faced by current commercial lithium-ion cells. From the materials science point of view, the lithium–sulfur battery is the most promising candidate because of its high energy density, low cost, and low toxicity. On the other hand, from the materials engineering point of view, the solid-state electrolytes with high ionic conductivity are proposed to increase the energy density, cyclability, and safety of the batteries through configuration modification. To adopt the advantages of these two novel battery technologies, we report an integrated design of the lithium–sulfur electrochemical cell with the solid-state electrolyte as a lithium–sulfur solid-state electrolyte cell. The lithium–sulfur electrochemical cell employs a high-sulfur-loading polysulfide cathode to achieve high energy density and to form a smooth ion-transfer interface between the catholyte and the solid-state electrolyte. On the other hand, the solid-state electrolyte provides excellent stability and safety to the cells by stabilizing the polysulfide cathode and protecting the lithium anode. The resulting cell design demonstrates the new battery materials and configurations, which include the development of a high-performance polysulfide cathode, the design and synthesis of solid-state electrolytes (i.e., polymer, oxide, and sulfide-based electrolytes), and the cell integration and interface analytical method. Our battery technologies enable the design of lithium–sulfur solid-state electrolyte batteries to achieve high sulfur loadings (4–16 mg cm–2) and high sulfur contents (50–80 wt%), which are better than those of current lithium–sulfur batteries that aim to be 5–10 mg cm–2 and 70 wt%. With the high sulfur loading, the lithium–sulfur solid-state electrolyte batteries exhibit high areal capacity (5–7 mA·h cm–2) and energy density (11–15 mW·h cm–2). Both values are higher than those of commercial lithium-ion cells for electric vehicles. Moreover, the cell has a long cyclability (100–200 cycles) and high rate capability (C/20 to 1C rate). Conclusion In summary, we report in the presentation a summary of our lithium–sulfur solid-state electrolyte batteries with a high-loading polysulfide cathode. The solid-state electrolytes stabilize the polysulfide cathode and the electrochemical reaction of lithium–sulfur batteries, while the stabilized polysulfide cathode forming a stable ionic conductive interface between the cathode and the solid-state electrolytes. Our lithium–sulfur solid-state electrolyte cells demonstrate outstanding battery-design parameters, excellent cell-performance values, and advanced interface analytical method. Both are essential for the commercial development of advanced next-generation rechargeable batteries. References L.-L. Chiu, S.-H. Chung, J. Mater. Chem. A 2022, 10, 13719.Y.-J. Yen, S.-H. Chung, J. Mater. Chem. A 2023, 11, 4519.Y.-C. Huang, B.-X. Ye, S.-H. Chung, RSC Adv. 2024, 14, 4025.

Design of Spherical Hard Carbon Secondary Particles for Na-Ion Battery Anode Application

Recently, Na-ion rechargeable batteries have been successfully developed and launched as the main power sources of a few novel electric vehicles in China. An energy density of the mass-produced Farasis Energy Na-ion batteries have been announced as between 140 Wh/kg and 160 Wh/kg with the layered oxide cathode and hard carbon anode combination. Though the commercialization of the Na-ion batteries is highly remarkable owing to the cost-effectiveness and long lifespan, the energy density of the Na-ion batteries needs to be improved even further considering the current state-of-art advanced practical Li-ion batteries of ca. 300 Wh/kg.Development of a novel anode material can contribute to the energy density improvement. Hard carbons with random shapes, which have been employed as the main anode materials in the commercial Na-ion batteries, have demonstrated the specific capacity of 200 to 300 mAh/g based on the carbonized biomasses. To improve energy density, shape and microstructure of the hard carbons need to be carefully designed. On the one hand, random shapes are not highly desired to achieve high tap density. Instead, spherical shapes with uniform particle sizes are beneficial to increase tap density as well as the energy density [1]. On the other hand, the carbonaceous microstructure needs to be optimized because the Na is stored through various mechanisms with combinations of i) adsorption at the surface of open pores, ii) adsorption at defect sites of graphene sheets, iii) insertion between graphene layers, and iv) pore filling [2]. As such, design of spherical hard carbon with well-established microstructure can provide high energy density. In this work, spherical hard carbon in Figure 1 was prepared using carbon precursor material (polyacrylonitrile) and sacrificial polymer (poly(styrene-co-acrylonitrile)) dissolved in the cosolvent (N,N-dimethylformamide). Carbonaceous microstructures were modified using the chemical and physical approaches. The morphological, structural, and electrochemical characterizations will be presented at the conference.[1] Oh, H. J. et al., Chem. Eng. J. 454, 140252 (2023)[2] Chen, C. et al., Carbon Energy 4, 1133-1150 (2022)Figure 1. SEM image of spherical hard carbon Figure 1

(Invited) Early-Onset Degradation of (La,Sr)(Co,Fe)O3 in Solid Oxide Electrolysis Cells

The increasing need for global hydrogen ideally depends on low-cost 1$/kg green hydrogen. The DOE’s Energy Earthshot initiative aims to reduce the cost of green hydrogen to achieve this goal in a decade. There are a number of pathways of which solid oxide electrolysis cells (SOECs) are one of the most attractive1. SOECs have high demonstrated efficiency for hydrogen production without precious metal catalysts but at present with limited lifetimes2–4. SOEC’s have a layered structure consisting of an LSCF-GDC composite cathode (La0.6Sr0.4Co0.2Fe0.8O3-δ / gadolinium doped ceria), a GDC barrier layer, YSZ (yttrium stabilized zirconia) electrolyte, and Ni-YSZ anode support layer. This structure exhibits various degradation mechanisms initiating at both the air and fuel electrode at high operating temperatures predominately at the interfaces5,6.Understanding the mechanisms behind cell degradation and their potential effects on cell performance is critical to reach hydrogen Earthshot goals. There has been significant focus on the coarsening of Ni in the fuel electrode and advancement made in reducing its negative effects on cell performance over time 7. Another significant mechanism is due to the degradation of LSCF at temperatures above 550 °C 8. As LSCF degrades, Sr migrates from the structure and becomes mobile throughout the cell. This poses problems as it reaches the electrolyte and forms SrZrO3 which causes both ohmic losses and potential mechanical failure9. This study focuses on the initiation of this mechanism and its progression in the break in period of the cell. Extensive characterization of early-onset degradation is achieved through SEM (Scanning Electron Microscopy), STEM EDS (Scanning Transmission Electron Microscopy), XANES (X-ray Absorption Near Edge Structure) and Synchrotron XRD (X-ray Diffraction). These techniques are then paired with first principles calculations of the 6428-LSCF phase stability in modeling the stoichiometric changes to rhombohedral LSCF in the cell. Together this allows us to achieve spatial mapping, phase progression over time, and predict stoichiometry changes in early onset degradation. These methods identify several unique phases that result from the degradation of LSCF some of which are known to impact cell lifetimes. Identifying the pathways of early onset degradation allows for mitigation strategies to be developed for cell sintering and fabrication.(1) Hydrogen Shot. Energy.gov. https://www.energy.gov/eere/fuelcells/hydrogen-shot (accessed 2024-04-18).(2) Laguna-Bercero, M. A. Recent Advances in High Temperature Electrolysis Using Solid Oxide Fuel Cells: A Review. J. Power Sources 2012, 203, 4–16. https://doi.org/10.1016/j.jpowsour.2011.12.019.(3) Elder, R.; Cumming, D.; Mogensen, M. B. Chapter 11 - High Temperature Electrolysis. In Carbon Dioxide Utilisation; Styring, P., Quadrelli, E. A., Armstrong, K., Eds.; Elsevier: Amsterdam, 2015; pp 183–209. https://doi.org/10.1016/B978-0-444-62746-9.00011-6.(4) Ferrero, D.; Lanzini, A.; Santarelli, M.; Leone, P. A Comparative Assessment on Hydrogen Production from Low- and High-Temperature Electrolysis. Int. J. Hydrog. Energy 2013, 38 (9), 3523–3536. https://doi.org/10.1016/j.ijhydene.2013.01.065.(5) Hauch, A.; Jensen, S. H.; Ramousse, S.; Mogensen, M. Performance and Durability of Solid Oxide Electrolysis Cells. J. Electrochem. Soc. 2006, 153 (9), A1741. https://doi.org/10.1149/1.2216562.(6) Kanae, S.; Toyofuku, Y.; Kawabata, T.; Inoue, Y.; Daio, T.; Matsuda, J.; Chou, J.-T.; Shiratori, Y.; Taniguchi, S.; Sasaki, K. Microstructural Characterization of SrZrO3 Formation and the Influence to SOFC Performance. ECS Trans. 2015, 68 (1), 2463. https://doi.org/10.1149/06801.2463ecst.(7) Mogensen, M. B.; Chen, M.; Frandsen, H. L.; Graves, C.; Hauch, A.; Hendriksen, P. V.; Jacobsen, T.; Jensen, S. H.; Skafte, T. L.; Sun, X. Ni Migration in Solid Oxide Cell Electrodes: Review and Revised Hypothesis. Fuel Cells 2021, 21 (5), 415–429. https://doi.org/10.1002/fuce.202100072.(8) Tai, L.-W.; Nasrallah, M. M.; Anderson, H. U.; Sparlin, D. M.; Sehlin, S. R. Structure and Electrical Properties of La1 − xSrxCo1 − yFeyO3. Part 2. The System La1 − xSrxCo0.2Fe0.8O3. Solid State Ion. 1995, 76 (3), 273–283. https://doi.org/10.1016/0167-2738(94)00245-N.(9) Lu, Z.; Darvish, S.; Hardy, J.; Templeton, J.; Stevenson, J.; Zhong, Y. SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering. J. Electrochem. Soc. 2017, 164 (10), F3097. https://doi.org/10.1149/2.0141710jes.

Preventing Lithium Dendrites on Fast Charging Batteries Using Interface Control

Lithium (Li) dendrites often grow on the surface of graphite anode of lithium-ion batteries during charging process, particularly under harsh conditions such as high currents, high voltages (i.e., high state of charge), and low temperatures. Dendrites cause capacity fade, short-circuit, and eventually fire hazard.Addressing the dendrites-related problems, various strategies have been developed, including the formation of a stable solid electrolyte interphase (SEI) layer, modification of separator and/or electrode, etc. Herein, we will present the interfacial control technique using designed electrolyte formulation that stabilizes the SEI layer of anode and thus prevents Li dendrites. Stabilized SEI layer induces to improve the cycle life of high-nickel based Li-ion batteries and enables faster charging than conventional 0.3 C (charged in 3.3 h) under harsh conditions. In the meeting, the correlation between performance and interface stability will be discussed.

Li Concentration Change Around Cu/Lipon Interface Measured By Time of Flight Elastic Recoil Detection Analysis

All-solid-state rechargeable lithium (Li) batteries (ASSBs) utilizing inorganic lithium-ion (Li+) conductive solid electrolytes (SEs) are gathering significant interest as a next-generation battery. To enhance the energy density of ASSBs, employing a Li metal anode is crucial due to its substantially higher capacity (3860 mAh g-1) compared to conventional graphite anodes (372 mAh g-1). Among various SEs compatible with Li metal anodes, lithium phosphorus oxynitride glass electrolyte (LiPON) stands out as an especially promising material for stabilizing the Li/SE interface [1]. This is evidenced by the fact that thin-film-type ASSBs employing LiPON and Li metal anodes demonstrate stable charge-discharge cycles over ten thousand cycles without capacity degradation [2].Regarding the Li/LiPON interface in thin-film ASSBs, it is observed that Li plating-stripping reactions occur stably. Yet, advanced analyses indicate the formation of a reaction layer at this interface. Cheng et al. utilized Cryo-STEM analysis to investigate the Li/LiPON interface, revealing the generation of by-products like Li2O, Li3N, and Li3P within an 80 nm thickness range from the interface [3]. Similarly, Sicolo et al. conducted XPS measurements on the LiPON surface before and after Li deposition, confirming the formation of a reaction layer immediately following Li layer deposition [4]. Theoretical calculations have suggested that LiPON reacts with Li metal and the thermodynamical stability of LiPON is estimated to be 0.68 V vs. Li/Li+ [5]. On the other hand, Schwietert et al. have reported that LiPON does not undergo reductive decomposition less than 0.68 V by taking a metastable state because an activation barrier for the decomposition can retard reductive decomposition [6]. Clarifying this interphase phenomenon is essential for the development of ASSBs with Li metal anodes.In this study, focusing on the increase in Li content with the reductive decomposition of LiPON, we investigate Li concentration changes around the Cu/LiPON interface by time-of-flight elastic recoil detection analysis (TOF-ERDA) [7]. TOF-ERDA needs no sample pretreatment for the detection of Li and then it can effectively observe Li concentration changes induced by electrochemical reactions around the interface. We confirmed that Li concentration increased around the interface within 30 nm thickness when maintained at 0.006 V vs. Li/Li+ before the Li plating voltage at 0 V vs. Li/Li+. This means that a decomposed region of LiPON forms around the interface within 30 nm thickness in this situation. Electrochemical analysis suggests one of the decomposed materials to be Li3P [4]. These findings basically align with TEM-EELS data, underscoring the utility of TOF-ERDA in analyzing Li concentration changes around interfaces.Reference Chung K, Kim WS, Choi YK (2004) Lithium phosphorous oxynitride as a passive layer for anodes in lithium secondary batteries. J Electroanal Chem 566:263-267 Wang B, Bates JB, Hart FX, Sales BC, Zuhr RA, Robertson JD (1996) Characterization of thin‐film rechargeable lithium batteries with lithium cobalt oxide cathodes. J Electrochem Soc 143:3203-3213 Cheng D, Wynn TA, Wang X, Wang S, Zhang M, Shimizu R, Bai S, Nguyen H, Fang C, Kim M, Li W, Lu B, Kim SJ, Meng YS (2020) Unveiling the stable nature of the solid electrolyte interphase between lithium metal and LiPON via cryogenic electron microscopy. Joule 4:2484-2500 Sicolo S, Fingerle M, Hausbrand R, Albe K (2017) Interfacial instability of amorphous LiPON against lithium: A combined Density Functional Theory and spectroscopic study. J Power Sources 354:124-133 Zhu Y, He X, Mo Y (2015) Origin of outstanding stability in the lithium solid electrolyte materials: insights from thermodynamic analyses based on first-principles calculations. ACS Appl Mater Interfaces 7:23685-23693 Schwietert TK, Vasileiadis A, Wagemaker M (2021) First-Principles prediction of the electrochemical stability and reaction mechanisms of solid-state electrolytes. JACS Au 1:1488-1496 Yasuda K (2020) Time-Of-Flight ERDA for depth profiling of light elements. Quantum Beam Sci 4:40 AcknowledgementThis work was supported by JSPS KAKENHI “Interface IONICS” (JP19H05813, 20H05293, and 22H04617) and by JST GteX, JPMJGX23S2.

Preventing Metal-Ion Cross-Talk via Gel Polymer Electrolyte for Li-Ion Batteries at High-Voltage

The pursuit of high energy density batteries drove the utilization of a high voltage operational range using nickel-rich layered oxides, represented as LiNixCoyMnzO2 (NCM; x + y + z = 1, x ≥ 0.6). It is a straightforward method in that it can increase energy density by simultaneously increasing capacity and average discharge voltage without changing electrodes and electrolytes. However, during high-voltage operation (> 4.5 V versus Li/Li+), Ni-rich NCM undergoes extensive delithiation, leading to the formation of high-valence Ni4+ ions.These high-valence nickel ions are susceptible to decomposing the electrolyte and reducing into low-valence Ni cation (Ni3+ and Ni2+). As a result of the aforementioned side reaction, the cross-talk of dissolved Ni2+ toward the anode can be accelerated. The deposition of Ni2+ at the anode surface suppresses the intercalation of Li+ into the anode layer structure. Additionally, the migration of Ni2+ to adjacent lithium vacancy sites in cathode, leads to the formation of an electrochemically inactive rock-salt phase. Due to these reasons, significant capacity degradation occurred as the cycles progressed, posing challenges despite the high initial capacity. Additionally, in the charged state, the release of oxygen due to structural collapse increases the risk of fire.In this study, we aimed to enhance the charging performance of NCM811 up to 4.6 V, specifically within the full cell range of 4.55 V. To mitigate the problem of high voltage operation, we introduced a gel polymer electrolyte (GPE) made by PVA-CN which is a cross-linked polymer. Only 2 wt. % of PVA-CN is needed in carbonate-based electrolytes for gelation. We attached N, N-Disuccinimidyl carbonate moiety (SC) to the hydroxyl groups of PVA-CN for (1) anchoring and (2) chelating transition metal ions to inhibit the side reactions of high-valence metal ions or dissolved metal ions from the cathode. FT-IR and NMR analysis confirmed the 6% of SC attached to PVA-CN (SC-PVA-CN). Even with this small addition, it showed superior performance compared to the general carbonate-based liquid electrolytes.Highly oxidized nickel ions tend to take electrons away from the electrolyte, undergoing reduction to form Ni2+ ions. Inclusion of anchoring polymers in the electrolytes maintained the transition metals in a stable state during charging processes, inhibiting side reactions with the electrolyte. In the case of liquid electrolytes, the ratio of Ni2+ and Ni3+ was dominant at the charged state after formation cycles. However, the ratio of Ni4+ was increased when the SC-PVA-CN GPE was present in the electrolyte. This is because bidentate coordination to Ni4+ created an environment similar to Ni2+ at the charged state. High ratio of Ni4+ at the charged state is beneficial in maintaining the structure under high voltage operating conditions by reducing the leakage of nickel from the cathode. Transition metal ions better maintain their place and act as a pillar within the cathode structure during the process of repeated charge and discharge.Maintaining the cathode structure also suppresses the formation of particle cracks. By reducing the amount of electrolyte penetrating between particle cracks, interface side reactions were also suppressed, decreasing phase changes inside the material, and maintaining lithium-ion transmission path.It is known that one transition metal ion takes up two lithium ions for intercalation to the anode. Some Ni2+ ions generated from the cathode because the surface is not completely covered with GPE can also be prevented from moving to the anode. After Ni2+ dissolution, they were chelated by functional groups of SC-PVA-CN in the bulk electrolyte region and reduced the amount of transition metal ions deposited on the anode. Therefore, more lithium ions can reversibly de/intercalate to the anode, mitigating irreversible capacity loss, which greatly contributes to maintaining capacity at high voltage operation.Additionally, the non-flammability was enhanced by utilizing SC-PVA-CN GPE. When igniting the liquid electrolyte and the SC-PVA-CN GPE using a torch, the liquid electrolyte ignited for 41 s g-1, while the SC-PVA-CN GPE did not ignite. This GPE formed nitrile-nitrile conjugation bonding which contained high bonding energy. In addition, interaction between solvent mitigated the volatility of liquid parts.In short, by utilizing SC-PVA-CN GPE, it showed better performance in the high voltage operation due to anchoring and chelating. Additionally, it showed non-flammability, enabling both high energy density and better safety. Figure 1

Comparison of Galvanostatic and Potentiostatic Accelerated Stress Tests of Bifunctional Pt-Ir Alloy Anode Catalysts for H2 Starvation Using Rde Technique

One of the main challenges to overcome for the wide implementation of PEMFCs is the improvement of their long-term durability. For instance, the blockage of the diffusion pathway by liquid water or rapid changes of load can lead to hydrogen starvation.[1] Due to the hydrogen starvation, the anode potential increases and accelerates the carbon oxidation reaction (COR) to further supply electrons and protons for the cathode ORR half-cell reaction, also referred to as cell reversal event.[2] Aggregation and particle detachment associated with the carbon corrosion occur, resulting in a drastic loss of the PEMFC performance.[3] Therefore, material innovation solutions are needed to overcome the cell reversal events. In this context, fast and simple accelerated stress tests and set-ups are needed. Currently, galvanostatic accelerated stress tests (G-AST) at single cell level are often used to evaluate the cell reversal tolerance (CRT) of catalyst materials, which is extremely time-consuming, costly and slow.[4] On the other hand, the rotating disc electrode (RDE) technique is widely used, simple, less expensive and fast for catalyst screening. However, the electrochemical measurements of activity and durability are usually carried out in the potentiostatic mode. The research question arises whether the RDE technique is capable of evaluating the CRT behaviour of novel catalyst materials using galvanostatic AST.This systematic work compared both galvanostatic and potentiostatic accelerated stress tests (G-AST and P-AST) protocols to evaluate the degradation behaviour of novel bifunctional Pt-Ir alloy catalyst materials for hydrogen starvation. The Pt-Ir alloy catalysts with 1:1 and 3:1 ratios were prepared by wet-impregnation route. Here, the PtIr and Pt3Ir catalysts supported on Vulcan XC72 show a mean particle size of 3-5 nm and total metal loading of 35-50 wt.%Pt+Ir obtained from TEM, TGA and EDX data. In a RDE set-up equipped with three-electrode configuration, all electrochemical measurements were performed in 0.1 M HClO4 and room temperature. At begin-of-life (BoL), the performance of the Pt-Ir catalysts was evaluated by measuring the ECSA via Hupd and CO stripping methods, HOR and OER polarization curves. It is noted that the HOR polarization curves were only fitted with the diffusion limiting current due to the fast kinetics of the HOR on platinum and iridium surfaces in acidic media. For the G-AST protocol, a current density of 0.5 mA/cm2 geo was held for 10h with a cut off at 2 VRHE. The time it takes to reach 2 VRHE is referred to as the fail time (FT) and signifies the loss of the protection mechanism of catalyst materials, namely the OER activity. Based on the results from the G-AST protocol, the same FT was used to perform the chronoamperometric measurements by holding the potential at 1.6 VRHE during the P-AST protocol.At the BoL, the Pt-Ir catalysts with 3-4 nm size show sufficient ECSA values (45-50 m2/gPt+Ir via Hupd) and improved OER activity (PtIr: 23±6 A/gPt+Ir and Pt3Ir: 8±1 A/gPt+Ir @1.5 VRHE) compared to the commercial Pt/V catalyst (79±4 m2/gPt via Hupd, 6±1 A/gPt @1.5 VRHE) and IrOx (47±6 A/gIr). During the G-AST, we observed that the FT increases with higher Ir content. In addition, the Pt3Ir/V catalyst shows a significant improvement of FT compared to the Pt/V. More precisely, during the G-AST protocol, the potential of 2 VRHE by applying a constant current density of 0.5 mA/cmgeo was already reached after 15min, while for the Pt3Ir/V catalyst this took at least 1 hour. Furthermore, our data shows that the G-AST protocol is more aggressive compared to the P-AST to evaluate the catalyst aging processes.Altogether, we showed the influence of galvanostatic and potentiostatic ASTs for rapid benchmarking of novel bifunctional cell reversal tolerant Pt-Ir alloy catalysts using the three-electrode RDE technique. This study can be helped to improve the electrochemical results obtained from the RDE to the catalyst coated membranes.[1] Marić, R. et al.Towards a Harmonized Accelerated Stress Test Protocol for Fuel Starvation Induced Cell Reversal Events in PEM Fuel Cells: The Effect of Pulse Duration. J. Electrochem. Soc., 2020, 167, 124520.DOI: https://doi.org/10.1149/1945-7111/abad68[2] Chen W. et al.: Thickness effects of anode catalyst layer on reversal tolerant performance in proton exchange membrane fuel cell. Int. J. Hydrog. Energy, 2021, 46, 8749.DOI: https://doi.org/10.1016/j.ijhydene.2020.12.041[3] Zhou X. et al.: High-Repetitive Reversal Tolerant Performance of Proton-Exchange Membrane Fuel Cell by Designing a Suitable Anode. ACS OMEGA, 2020, 5, 10099.DOI: https://dx.doi.org/10.1021/acsomega.0c00638[4] Peng Y. et al.: Pitfalls of a commonly used accelerated stress test for reversal tolerance testing of proton exchange membrane fuel cell anode layers. J. Power Sources, 2021, 500, 229986.DOI: https://doi.org/10.1016/j.jpowsour.2024.234087

Constructing 3D Crosslinked Macromolecular Networks as a Highly Efficient Interface Layer for Ultra-Stable Zn Metal Anodes.

Aqueous zinc ion batteries (AZIBs) are experiencing rapid development due to their high theoretical capacity, abundant zinc resources, and intrinsic safety. However, the progress of AZIBs is hindered by uncontrollable parasitic reactions and excessive dendrite growth, which compromise the durability and effective utilization of zinc metal anodes. To address these challenges, the study has constructed a 3D crosslinked macromolecular network composed of zinc ion-bonded potato starch (StZ) as an interface layer on Zn foil (StZ-Zn) to inhibit hydrogen evolution, regulate Zn2+ flux, and ensure uniform Zn deposition. Density functional theory calculations, molecular dynamics simulations, COMSOL Multiphysics simulations, and in situ Raman spectra demonstrate that the 3D StZ interface layer facilitates Zn2+ desolvation by restructuring the solvation shells. This process reduces the concentration of H2O at the anode, thereby inhibiting the hydrogen evolution reaction. Consequently, Zn2+ transport is more efficient, promoting a homogeneous Zn2+ flux and enabling dendrite-free Zn deposition. As a result, StZ-Zn||StZ-Zn symmetric cell delivers a superb lifespan of 4800 h at the current density of 5 mA cm-2, and the corresponding cumulative capacity is as high as 12000 mAh cm-2. Notably, StZ-Zn||NaV3O8·1.5H2O full cell can stably operate for 2500 cycles at 5 A g-1 with an outstanding capacity retention of 92%.

Gravure-Printed Anodes Based on Hard Carbon for Sodium-Ion Batteries

Printed batteries are increasingly being investigated for feeding small, wearable devices more and more involved in our daily lives, promoting the study of printing technologies. Among these, gravure is very attractive as a low-cost and low-waste production method for functional layers in different fields, such as energy, sensors, and biomedical, because it is easy to scale up industrially. Thanks to our research, the feasibility of gravure printing was recently proved for rechargeable lithium-ion batteries (LiBs) manufacturing. Such studies allowed the production of high-quality electrodes involving different active materials with high stability, reproducibility, and good performance. Going beyond lithium-based storage devices, our attention was devoted on the possibility of employing highly sustainable gravure printing for sodium-ion batteries (NaBs) manufacturing, following the trendy interest in sodium, which is more abundant, economical, and ecofriendly than lithium. Here a study on gravure printed anodes for sodium-ion batteries based on hard carbon as an active material is presented and discussed. Thanks to our methodology centered on the capillary number, a high printing quality anodic layer was produced providing typical electrochemical behavior and good performance. Such results are very innovative and relevant in the field of sodium-ion batteries and further demonstrate the high potential of gravure in printed battery manufacturing.

Three-Dimensional Covalent Organic Framework with Dense Lithiophilic Sites as Protective Layer to Enable High-Performance Lithium Metal Battery.

Lithium (Li) metal batteries with remarkable energy densities are restrained by short lifetime and low Coulombic efficiency (CE), resulting from the accumulative Li dendrites and dead Li during cycling. Here, we prepared a new three-dimensional (3D) covalent organic framework (COF) with dense lithiophilic sites (heteoatom weight contents of 32.32 wt %) as an anodic protective layer of Li metal batteries. The 3D COF was synthesized using a [6+4] synthesis strategy by inducing flexible 6-connected cyclotriphosphazene derivative aldehyde and 4-connected porphyrin-based tetraphenylamines. Both phosphazene and porphyrin rings in the COF served as electron-rich and lithiophilic sites, enhancing a homogeneous Li+ flux via 3D direction towards highly smooth and compact Li deposition. The Li/Por-PN-COF-Cu cells achieved a record average CE of 99.1 % for 320 cycles with smooth Li deposition. Meanwhile, the abundant lithiophilic sites can promote fast Li+ transport with Li+ transference number of 0.87, enabling LiFePO4 full cell with stable stripping/plating processes even at a harsh rate of 5 C. Theoretical calculations revealed that the strong interaction force between Li+ and the COF facilitated the dissolution of Li+ from the electrolyte, and the low migration barrier of 1.08 eV indicated a favorable interaction between the Li+ ions and the π-electron system.

Three‐Dimensional Covalent Organic Framework with Dense Lithiophilic Sites as Protective Layer to Enable High‐Performance Lithium Metal Battery

AbstractLithium (Li) metal batteries with remarkable energy densities are restrained by short lifetime and low Coulombic efficiency (CE), resulting from the accumulative Li dendrites and dead Li during cycling. Here, we prepared a new three‐dimensional (3D) covalent organic framework (COF) with dense lithiophilic sites (heteoatom weight contents of 32.32 wt %) as an anodic protective layer of Li metal batteries. The 3D COF was synthesized using a [6+4] synthesis strategy by inducing flexible 6‐connected cyclotriphosphazene derivative aldehyde and 4‐connected porphyrin‐based tetraphenylamines. Both phosphazene and porphyrin rings in the COF served as electron‐rich and lithiophilic sites, enhancing a homogeneous Li+ flux via 3D direction towards highly smooth and compact Li deposition. The Li/Por‐PN‐COF‐Cu cells achieved a record average CE of 99.1 % for 320 cycles with smooth Li deposition. Meanwhile, the abundant lithiophilic sites can promote fast Li+ transport with Li+ transference number of 0.87, enabling LiFePO4 full cell with stable stripping/plating processes even at a harsh rate of 5 C. Theoretical calculations revealed that the strong interaction force between Li+ and the COF facilitated the dissolution of Li+ from the electrolyte, and the low migration barrier of 1.08 eV indicated a favorable interaction between the Li+ ions and the π‐electron system.

Reactivity and Stability of Reduced Ir-Weight TiO2-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes.

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO2-supported Ir@IrO(OH)x core-shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO2-supported Ir@IrO(OH)x core-shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A gIr-1 at 1.53 VRHE while reducing the iridium packing density from 1.6 to below 0.77 gIr cm-3. These advancements allow for viable anode layer thicknesses with lower Ir loading, reducing iridium utilization at 70% LHV from 0.42 to 0.075 gIr kW-1 compared to commercial IrO2/TiO2. The identification of the Ir@IrO(OH)x/TiO2 OER catalyst resulted from extensive HAADF-EDX microscopic analysis, operando XAS, and online ICP-MS analysis of 30-80 wt % Ir/TiO2 materials. These analyses established correlations among Ir weight loading, electrode electrical conductivity, electrochemical stability, and Ir mass-based OER activity. The activated Ir@IrO(OH)x/TiO2 catalyst-support system demonstrated an exceptionally stable morphology of supported core-shell particles, suggesting strong catalyst-support interactions (CSIs) between nanoparticles and crystalline oxide facets. Operando XAS analysis revealed the reversible evolution of significantly contracted Ir-O bond motifs with enhanced covalent character, conducive to the formation of catalytically active electrophilic OI- ligand species. These findings indicate that atomic Ir surface dissolution generates Ir lattice vacancies, facilitating the emergence of electrophilic OI- species under OER conditions, while CSIs promote the reversible contraction of Ir-O distances, reforming electrophilic OI- and enhancing both catalytic activity and stability.

Honeycomb‐Structured IrOx Foam Platelets as the Building Block of Anode Catalyst Layer in PEM Water Electrolyzer

AbstractAchieving robust long‐term durability with high catalytic activity at low iridium loading remains one of great challenges for proton exchange membrane water electrolyzer (PEMWE). Herein, we report the low‐temperature synthesis of iridium oxide foam platelets comprising edge‐sharing IrO6 octahedral honeycomb framework, and demonstrate the structural advantages of this material for multilevel tuning of anodic catalyst layer across atomic‐to‐microscopic scales for PEMWE. The integration of IrO6 octahedral honeycomb framework, foam‐like texture and platelet morphology into a single material system assures the generation and exposure of highly active and stable iridium catalytic sites for the oxygen evolution reaction (OER), while facilitating the reduction of both mass transport loss and electronic resistance of catalyst layer. As a proof of concept, the membrane electrode assembly in single‐cell PEMWE based on honeycomb‐structured IrOx foam platelets, with a low iridium loading (~0.3 mgIr/cm2), is demonstrated to exhibit high catalytic activity at ampere‐level current densities and to remain stable for more than 2000 hours.

Honeycomb-Structured IrOx Foam Platelets as the Building Block of Anode Catalyst Layer in PEM Water Electrolyzer.

Achieving robust long-term durability with high catalytic activity at low iridium loading remains one of great challenges for proton exchange membrane water electrolyzer (PEMWE). Herein, we report the low-temperature synthesis of iridium oxide foam platelets comprising edge-sharing IrO6 octahedral honeycomb framework, and demonstrate the structural advantages of this material for multilevel tuning of anodic catalyst layer across atomic-to-microscopic scales for PEMWE. The integration of IrO6 octahedral honeycomb framework, foam-like texture and platelet morphology into a single material system assures the generation and exposure of highly active and stable iridium catalytic sites for the oxygen evolution reaction (OER), while facilitating the reduction of both mass transport loss and electronic resistance of catalyst layer. As a proof of concept, the membrane electrode assembly in single-cell PEMWE based on honeycomb-structured IrOx foam platelets, with a low iridium loading (~0.3 mgIr/cm2), is demonstrated to exhibit high catalytic activity at ampere-level current densities and to remain stable for more than 2000 hours.

Improving Bioactivity of Anodic Titanium Oxide (ATO) Layers with Chlorine Ion Addition in Electrolytes

Appending diverse quantities of additional elements to the anodizing solution leads to the formation of a highly corrosion-resistant and biocompatible anodic Ti oxide (ATO) on the titanium surface. This study aims to investigate the synergistic effect of chlorine and sulfate ions in the anodizing solution on the formation mechanism and biocompatibility of anodized layers formed on pure Ti. For this purpose, sulfuric acid-based anodizing solutions with different molar ratios () of 0.25, 0.5, and 0.75, and total molars () of 1, 1.5, and 2 M, were utilized for galvanostatic anodizing conditions at different current densities. The response surface methodology was employed on these three anodizing parameters to optimize the quality of anodic Ti oxide layers. Voltage vs. time behavior, SEM surface morphology, and FE-SEM fractured cross-sectional observations were used to thoroughly discuss the formation mechanism. X-ray diffraction method, micro-Raman spectroscopy, and water contact angle measurements were performed to characterize the coatings. Corrosion properties of ATO layers were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in simulated body fluid (Hanks’ solution). The total molar () is recognized as the most influential factor on the anodic oxide layer properties, and a three-step formation mechanism, based on the competition between the formation and dissolution of anodic Ti oxide, was proposed in detail. The sample anodized with a molar ratio () of 0.5 at a constant current density of 70 mA.cm-2 and a total molar of 1.5 M achieved maximum corrosion resistance with a corrosion current density of 2.138e-11 A.cm-2 compares to 1.39e-8 A.cm-2 for the substrate. Furthermore, the addition of chloride ions to the anodizing bath resulted in more hydrophilic surfaces, promoting the formation of granular hydroxyapatite (HAp) on the TAO coating with maximum corrosion resistance in the Hank solution.

Development and Analysis of Inorganic Perovskite material for Solar Cells

In this work, for the first time, a blend of a prepared nano barium titanate (BaTiO3) using the hydrothermal method and Cs3Bi2I9 was used as a perovskite material for photo anode layer fabrication to be used in photovoltaic pv solar cell. This prepared layer was characterized through XRD, SEM and UV-Vis spectroscopy and the findings state that the band gap of the prepared layer was reduced further compared to the original material of barium titanate (insulating material) suggesting that the prepared material is promising in the PV cell. This fact was further confirmed through performance testing, which showed that the short circuit current (Isc) measured 5 mA and the photoconversion efficiency (PCE) was 2.4%. It was found the morphology of the prepared layer was also improved.

The Influence of Surface Segregation on the Anodizing of AlSi11Cu2(Fe) Diecastings

A positive segregation is usually formed on the casting surfaces produced by high-pressure die casting (HPDC). In diecast Al-Si-Cu alloy components, this segregation shows a higher content of Si compared to the nominal composition of the alloy and it drastically affects the anodizing response of the casting surface. In the present work, HPDC components were produced by AlSi11Cu2(Fe) alloy, grit-blasted, and then anodized in a sulfuric acid electrolyte at the temperature of -4.5°C. Before the anodizing process, some regions of the casting were also milled, in order to completely remove the surface segregation. Microstructural investigations were carried out on grit-blasted and milled surfaces to characterize the initial substrates before anodizing, and to study their effect on the growth of the anodic layer. Scratch and wear tests were also performed to investigate the surface mechanical properties after anodizing. The results show that the surface segregation and the rough surface present on grit-blasted substrate leads to the formation of a thin and homogeneous anodic layer. On the contrary, a thicker and scalloped oxide film is formed on the milled surfaces. After anodizing, grit-blasted surfaces show lower wear and scratch resistance than milled substrates. The presence of surface segregation prevents the thickening of the anodic layer, negatively affecting the surface wear resistance due to the reduced oxide thickness.