Formation Of Passive Layer Research Articles

Characterization of passive layer formation kinetics of Zn5Al hot-dip galvanized coatings using gel electrolytes

Purpose The formation of a natural passive layer on hot-dip galvanized coatings increases their corrosion resistance. Although the basic mechanisms of passive layer formation are known, the quantitative determination of the evolution of its passive character, in particular its surface resistivity, and its development under atmospheric weathering remains largely unexplored for zinc-5% aluminum (Zn5Al) coatings. Design/methodology/approach Zn5Al-galvanized test sheets were exposed to atmospheric weathering for four weeks during summer and winter, and the development of polarization resistance measured using a gel-type electrolyte over these periods. Further investigation included stripping away the formed passive layer midway through the exposure period and electrochemical characterization of the passive layer that re-formed after under continue weathering. Findings The results showed a steadily increasing resistivity of the corrosion product (passive) layer over the course of the weathering period; this was confirmed by supplementary macroscopic and microscopic analyses. Exposure conditions affected the speed of development. Polarization resistance values were higher by approximately 50 kΩcm2 during the winter compared to summer. Upon interruption of exposure and removal of the passive layer, it rebuilt up much more rapidly after exposure resumed in comparison with the initial layer. Originality/value The use of gel electrolyte for determining the polarization resistance of a metal surface is a novel and useful method. To the best of the authors’ knowledge, this study has, for the first time, established the suitability of this electrochemical test method for quantifying the coating resistance of Zn5Al galvanized steel after calibrating the measurement parameters.

Electrochemical corrosion behavior of α-titanium alloys in simulated biological environments (comparative study).

Titanium (Ti) and its alloys are widely utilized in orthopedic and dental applications due to their favorable mechanical properties and biocompatibility. Notably, titanium exhibits excellent corrosion resistance and can form a stable oxide layer, ensuring the longevity and functionality of implants in challenging physiological environments. This study investigates the corrosion behavior of α-Ti alloy in physiological saline solutions, emphasizing the role of key biomolecules found in the human body, including albumin, glycine, and glucose, as well as additional substances such as hydrogen peroxide (H2O2) and hydroxyapatite (Hap). A comprehensive suite of techniques-namely, open-circuit potential measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM)-was employed to assess the effects of these biomolecules on corrosion behavior. The findings indicate that, unlike H2O2 and Hap, the biomolecules studied significantly enhance the corrosion resistance of the α-Ti alloy in simulated physiological environments. H2O2, due to its strong oxidative properties, accelerates corrosion, while Hap induces ion release that adversely affects the alloy's stability. The observed improvement in corrosion resistance is attributed to the formation of a stable passive layer on the alloy's surface. Notably, this study presents the first long-term electrochemical and immersion tests conducted at 310 K, elucidating the effects of bovine serum albumin (BSA), H2O2, glycine, glucose, and Hap on the corrosion performance of the α-Ti alloy.

Bivalent Metal-Organic Batteries: Optimisation of Electrolytes By Next-Generation Additives

Li-Ion batteries, despite their commonness, suffer in Europe form poor raw material availability and the ever-raising price, observed most often in consumer electronics prices. Now more than ever novel battery technologies are on a rise. Bivalent metal-organic batteries are of cutting-edge nature, not yet researched thoroughly. They have emerged as promising candidates for next-generation energy storage systems due to their high energy density, cost-effectiveness, and environmental sustainability. However, several challenges hinder their commercialization, including poor cycling stability and limited electrode kinetics. The main issue for RMBs (Rechargeable Magnesium Batteries) and RCBs (Rechargeable Calcium Batteries) is electrolyte speciation, which leads to ion pair formation and poor multivalent ion desolvation. On the other hand, anodes suffer with poor metal plating/stripping efficiency and formation of passive layer with poor conducting properties. Electrolyte additives can act as ion pair scavengers and nets or catchers for cations or anions. This will prevent ion pair formation and promote multivalent ion desolvation. We built our research not only on interactions between bivalent metal cation and chelating additives, but also on linkage between salt anions and anion receptor – additives of choice. Proper design of additives’ molecules can enable partial anions’ immobilization and promote salt dissociation. We present a roadmap on current electrolyte additives: their selection, concept of molecule design and possible future improvements. We present a comprehensive roadmap for the development of electrolyte additives, which play a crucial role in enhancing the performance of multivalent metal-organic batteries. We combined a systematic approach for designing and optimizing electrolyte additives, considering factors such as solubility, redox potential, stability, and compatibility with RMB components. Key strategies for enhancing cycling stability, suppressing side reactions, and improving ion transport kinetics are discussed, along with recent advancements in additive synthesis and characterization techniques. Moreover, we outline strategies for evaluating the performance of electrolyte additives through comprehensive electrochemical analysis and highlights the importance of analytical methods for practical implementation. The role of computational modeling in accelerating the discovery and optimization of electrolyte additives is also discussed.

Regulating the Solvation Shell Structure of Eutectic Electrolytes for Stable and High Performance Anode-Free Zn-Li Hybrid Batteries

With the development of technology, various related policies have emerged wherein the application of batteries plays a crucial role. Presently, lithium-ion batteries widely used in the market suffer from poor safety, high cost, and temperature usage limitations. To solve these challenges, this study employs Zinc ion batteries (ZIBs) as the electrolyte. Zinc-based electrolytes exhibit high energy density, low cost, high safety, and abundant resources. However, the application of Zinc ion batteries (ZIBs) is accompanied by specific electrochemical issues, such as hydrogen evolution reaction (HER), dendritic growth, and the formation of passivation layers, which subsequently affect battery lifespan, Coulombic efficiency (CE), and energy efficiency (EE). Therefore, addressing these side reactions can lead to superior performance and benefits across various aspects of the electrolyte.Deep Eutectic Solvent (DES), formed through intricate hydrogen bond networks, divides salt compositions into hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD), thereby altering the total melting point. DES electrolytes can form unique structures, thus improving electrochemical side reactions. Leveraging these characteristics, this experiment designs a novel deep electronic solution (DES) electrolyte and assembles a pouch cell to measure its electrochemical performance.This electrolyte is prepared by initially heating and stirring a mixture of 1 mol of zinc chloride and 4 mol of acetamide until fully dissolved, followed by adding 1 mol of lithium acetate. Due to the high viscosity of the resulting electrolyte, 5 mol of acetonitrile is added after cooling to reduce viscosity. Additionally, the impact of adding water to the electrolyte on battery lifespan, overpotential, Coulombic efficiency, and energy efficiency is investigated. Therefore, another electrolyte is prepared for comparison, maintaining the same primary salt concentration but including 1 mol of water and 4 mol of acetonitrile.Using the positive electrode material lithium manganese oxide (LiMn2O4, LMO), a Zn//LMO anode-free cell is constructed for electrochemical testing. Initially, the electrolyte is tested for the electrochemical performance of Zn//Zn symmetric cells, Zn//Cu asymmetric cells, and Zn//LMO anode-free cells (with or without co-solvent). Various electrochemical tests are then conducted, including Electrochemical Impedance Spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV), Tafel plots, and C-Rate cycling. Furthermore, Raman spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy techniques are utilized to investigate the solvation structure of the electrolyte. Lastly, viscosity and conductivity measurements are performed.The results indicate that in Zn//Zn symmetric cells, electrolytes with added co-solvent exhibit a 0.36V reduction in overpotential during Zn plating/stripping compared to those without co-solvent. Additionally, in Zn//Cu asymmetric cells, electrolytes with added co-solvent demonstrate relatively stable Coulombic efficiency, maintaining an average of over 99.7% efficiency at a current density of 0.5 mA/cm2. In Zn//LMO anode-free cell testing, it is observed that electrolytes with added 1 mol of water and 4 mol of acetonitrile initially exhibit the highest specific capacity (75mAh/g), maintaining good specific capacity even after cycling at a current of 100mA/g. In C-Rate testing, the Zn//Cu asymmetric cell with added co-solvent shows better stability, with Coulombic efficiency maintaining above 99.9% when cycling back to low current density. the electrolyte with added 1 mol of water and 4 mol of acetonitrile in the Zn//LMO half-cell maintains a Coulombic efficiency of 99.4% and a specific capacity of 50 mAh/g when cycling back to low current density.Electrolyte analysis reveals the presence of [ZnCl(C2H5NO)2(CH3COO-)]+ at the peak of 282 cm-1 in the Raman spectrum. Upon adding acetonitrile, a characteristic peak of C-C≡N at 381 cm-1 appears, which decreases with adding water. Additionally, at the peak of 944 cm-1, a characteristic peak of lithium acetate C-C is observed, which shifts upon adding acetonitrile. This suggests a change in the coordination of zinc ions in the solvation shell, from one chloride ion and three acetamide molecules to one chloride ion, one acetate ion, and two acetamide molecules upon adding acetonitrile. In the FTIR spectrum, a blue shift is observed in the C=O characteristic peaks between 1640 cm-1~1670 cm-1 upon adding acetonitrile, indicating the penetration of acetonitrile into the solvation shell. Additionally, a blue shift is observed between 1360 cm-1~1420 cm-1, attributed to the C=O characteristic peaks of acetonitrile and acetate ions, confirming the penetration of acetate ions into the solvation shell, forming a unique Deep Eutectic Solvent (DES) structure. Figure 1

Notched Gate and Graded Gate Oxide Processing for Reduced Capacitance Application in RF MOSFETs

As the demands of RF applications are rising, optimization of internal MOSFETs capacitances is a key issue to improve the cut-off frequency. In this abstract we report the development of a novel N-MOS architecture processed on 8-inch SOI wafers. This architecture has a gate oxide with variable thickness along the channel and a reduced bottom gate length aiming at minimizing Gate to Drain/Source capacitance (1) (2). This improvement on Gate to Drain/Source capacitance mainly comes from a decrease in overlap capacitances as described in (3).The new process flow is composed as usual until Poly-Si gate etching. By controlling the species flow and process time during plasma etching steps, over etch at the bottom of the gate is performed (fig.1(a,b)). Poly-Si gate notching engineering is possible due to reduction of the passivation layer thickness at the bottom of the gate during plasma etch. As described in (4) the gate is first etched using a HBr/CL2/O2 chemistry until reaching close to the bottom of the gate, allowing the formation of a passivation layer made of SiOxCly and the anisotropy of the etch. To etch the remaining thickness HBr flow is augmented while CL2 and O2 flow are reduced, preventing formation of passivation layer. This leads to isotropic etch of the bottom gate and reduction of the gate length as regard to the top Poly-Si dimension. This over-etch reduces the physical gate length without changing the effective and the on-mask gate lengths, leading to overlap capacitance reduction.To produce gate oxide with variable thickness under gate sidewalls a two-steps process is performed. First, full plate oxide is grown before poly-Si deposition to act as middle gate thickness. Then undercut is performed, consisting of lateral etching of the gate oxide under gate sidewall after gate etch (fig.2.a). To achieve this undercut, hydrofluoric acid (HF) wet etch has been chosen. First trials with very low HF concentration become quickly saturated leading to small lengths under gate sidewalls (fig.2.b). Then more acidic solutions were used allowing satisfying undercut lengths (fig.2.c).Finally rapid thermal oxidation (RTO) is performed to obtain an oxide bird beak at both gate side as both Poly-Si gate and Si from the active region react with ambient O2 in the chamber. This leads to a gate oxide with variable thickness along the channel (fig.3(a.b)) which has both effects: to get smoother poly-Si foot and a down step in the active between channel and Source/Drain regions. During this process step, a built-in spacer on the gate sides for LDD implantation is formed. RTO process step has grown a thicker oxide over Source/Drain areas which has to be reduced to allow an accurate LDD implantation, this is done by anisotropic etching. After these new steps, the process goes back to a standard N-MOS process flow.Some early versions of the notched gate have been investigated (5), and these experiments and details on processing recipe seem promising for electrical results. As poly-Si foot has been smoothed and graded gate oxide (GGO) on top of overlaps region is formed. It would allow a reduction in parasitic capacitances improving cut-off frequency of RF applications.References RF LDMOSFET with Graded Gate Structure. Xu Shuming, Foo Pan Dow. Toronto : s.n., 2001. 1th International Symposium on Power Semiconductor Devices and ICs. ISPSD'99 Proceedings. pp. 221-224. DOI:10.1109. Notched-Gate pMOSFET with ALD TiN/High-κ Gate Stack Formed by Selective Wet Etching. Zhang, D. Wu and J. Lu and P.-E. Hellström and M. Östling and S.-L. s.l. : The Electrochemical Society, Inc., 2004, Electrochemical and Solid-State Letters, Vol. 7, p. 228. 10.1149/1.1795612. A simple efficient model of parasitic capacitances of deep-submicron LDD MOSFETs. Fabien Pregaldiny, Christophe Lallement,Daniel Mathiot. s.l. : Solid State Electronics, 2002, Vol. 46, pp. 2191–2198. https://doi.org/10.1016/S0038-1101(02)00248-4. Design of notched gate processes in high density plasmas. J. Foucher, G. Cunge, L. Vallier, and O. Joubert. s.l. : AVS: Science & Technology of Materials, Interfaces, and Processing, 2002, Vols. Journal of Vacuum Science & Technology B 20,. http://dx.doi.org/10.1116/1.1505959. Notched gate MOSFET for capacitance reduction in RF SOI technology. al, L. Antunes et. s.l. : 2023 IEEE International Conference on Design, Test and Technology of Integrated Systems (DTTIS), 2023. doi: 10.1109/DTTIS59576.2023.10348288. Figure 1

Electrochemical Properties of Indium CMP for Quantum Applications

Indium is emerging as a promising material in the semiconductor and quantum device integration technology, particularly as an interconnect material. Its application is extensively studied for fabricating microbumps and for filling into Through-Silicon Vias, thereby facilitating hybrid bonding connections crucial for quantum computing advancements. Achieving such connections, especially hybrid bonding, demands precision at the submicron level. Chemical Mechanical Planarization is a critical process in this context, which plays an important role in achieving the desired flatness and required surface quality. It achieves this through a combination of mechanical abrasion and electrochemical dissolution of the metal. Despite its importance, research on Indium CMP is relatively nascent, indicating a significant opportunity for exploration in this area. This study aims to delve into the specifics of Indium CMP, particularly focusing on understanding the electrochemical characteristics during the polishing process. By examining the impact of slurry composition and various influencing factors on the polishing efficacy, we aim to offer a comprehensive insight into the Indium CMP process.We investigate Indium films electroplated onto Cu substrates with a thickness of approximately 1 µm. The films' electrochemical behaviors were evaluated in both acidic (pH 3) and alkaline (pH 10) slurry, utilizing dynamic electrochemical evaluation equipment. The abrasive type for both slurries is a Silica base with less than 50 nm diameter. To explore the effects of oxidants, varying concentrations of Hydrogen Peroxide were introduced. The experimental parameters included an applied force of 1 psi and a testing area of 1.3 cm².Figures 1a and 1b show in situ open-circuit potential (OCP) measurements of Indium over time with and without polishing. In both acidic and alkaline slurries, OCP values for Indium experienced a sharp decrease during polishing, followed by a rapid increase upon stopping polishing, indicating the quick formation and subsequent removal of a passivation layer. With the addition of H2O2, the passivation layer's removal, growth, and subsequent removal continue under dynamic and static conditions in the pH 3 slurry. However, in the pH 10 slurry, the potential jump was minimal, and the passivation layer was only partially removed upon restarting polishing. The rate of passivation layer removal roughly corresponded to its formation rate, suggesting the presence of a thin oxide film throughout polishing. This phenomenon may be due to the excessive thickness of the passivation layer at a 0.4% H2O2 concentration, forming too thick layer to remove by CMP.Figures 1c and 1d illustrate the corrosion current and potential of Indium at various concentrations of H2O2. With increasing H2O2 concentration, the corrosion potential increases in both slurries. In acidic slurry without H2O2, the corrosion potential of Indium was -0.54 V corresponding to its presence as Indium metal in the Pourbaix diagram. When H2O2 was added, the corrosion potential increased, indicating the formation of Indium (III) ions in an acidic environment and the strong oxidizing agent H2O2. In the pH 3 slurry, despite the addition of an oxidant, the passivation layer exits, attributed to the presence of a corrosion inhibitor within the slurry. This phenomenon contributes to the reduction in the corrosion current of the Indium film with increasing H2O2 concentration, as corrosion inhibitor mitigates active corrosion by blocking it. Inhibitors enhance the resistance area between the metal surface and the electrolyte, thus impeding or stopping galvanic reactions and the loss of electrons from the metal surface.In alkaline solutions, Indium metal remains stable in the absence of oxidants. However, upon the addition of H2O2, the corrosion potential value shifted from -0.714 V without H2O2 to -0.38 V for 0.2% H2O2. This alteration aligns with the emergence of the In2O3 passive layer, as indicated by the Pourbaix diagram. The rise in corrosion potential with H2O2 stemmed from the restricted anodic reaction due to the concurrent growth of the cathodic reaction, leading to the formation of a thick passivation layer. This layer impedes ion transport, so necessitating energy (potential) for the polishing process to proceed. Simultaneously, the corrosion current of Indium increased in the alkaline slurry, signifying active dissolution. According to Haedo Jeong et al., the active zone corresponds to the oxidation reaction's dissolution area, indicating the ongoing oxidation of the metal.The investigation into Indium CMP revealed a notable dependence on the composition of the abrasive slurry. Indium metal demonstrates stability in both acidic and alkaline slurry in the absence of oxidants. Notably, the introduction of H2O2 to the slurry distinctly induces a phase transition from Indium ions in acidic slurry to In2O3 in alkaline environments, suggesting a potential study to elucidate the mechanism of Indium CMP. Figure 1

Multilayer Porous Transport Layers for Polymer Electrolyte Water Electrolysis to Replace Thin Protective Pt Coating at Low IrO2 Loading

The use of expensive PGM catalysts for the OER and HER leads to high production costs of Polymer electrolyte water electrolysis (PEWE). Moving towards lower iridium oxide (IrOx) catalyst loadings for the anode side can severely affect performance and stability [1]. Recent studies revealed that the structure of the interface between the anodic porous transport layer (PTL) and the catalyst layer (CL) is a crucial factor limiting cell efficiency and contributes significantly to the performance and use of the CL. The coarse structure PTL can develop inactive zones of the catalyst layer, which happens when the catalyst layer is not “close” to the connecting titanium structure [2]. The situation becomes worse when the IrO2 catalyst loading is reduced, and the catalyst layers become thinner. Recent evidence has shown that having additional Microporous layers (MPL) can overcome some of these issues by maximizing catalyst utilization and increasing cell efficiency. However, at low Ir loadings, a thin protective Pt coating on MPL is needed to avoid formation of TiOx passivation layer on the MPL surface and increase surface conductivity [3].In this work, we attempt to replace the thin protective Pt coating by adding an additional layer of Ti or TiN on the existing MPL aiming when using low loadings of IrO2 (0.5 – 0.1 mgIr cm-2). Vacuum plasma spraying (VPS) technology was used to apply TiN on the surface of MPL, while Ti was spray-coated, and vacuum sintered to create a hierarchically structured 3-layer PTL. Electrochemical performances of both Ti and TiN coated MPLs were evaluated by polarization curves and Electrochemical Impedance Spectroscopy measurements. The results are compared with a Pt coated MPL reference.

Oxide-Metal Transition Processes of CuxO Foams during CO2RR Probed by Operando Quick-XAS

Electrochemical CO2 reduction reaction (CO2RR) is a promising alternative for large-scale production of hydrocarbons. However, there are still some challenges including poor product selectivity and highly complex multiple-step reaction mechanisms.[1,2] To enhance the electrochemically active surface area and create more active surface sites, one of the promising approaches is the use of partial or complete (surface) oxidation of nanostructured copper materials. These Cu oxide precursor catalyst materials are not stable during the cathodic potentials applied for CO2RR, but still show an enhanced selectivity for the formation of C2+ products.[3,4] Interestingly, few studies proposed that oxygen can be present under CO2RR conditions in a few nm thick amorphous copper layer, while DFT calculations indicate that no subsurface oxygen remains thermodynamically stable at these highly cathodic potentials.[5-7] So far, only Valesco-Vélez et al. studied the Cu oxidation state changes (Cu2+ and Cu+ to metallic Cu) during CO2RR in CO2-saturated 0.1 M KHCO3 probed by operando X-ray absorption spectroscopy (XAS).[8] However, for pure CuO no reduction to metallic copper or Cu2O even at highly cathodic conditions is found, due to the formation of a copper carbonate passivation layer.[8] Thus, it is still poorly understood how the structure of the Cu/CuxO precursor materials and their simultaneous reduction processes to metallic copper influence the CO2RR product distribution and the overpotential required for hydrocarbon formation. Recently, we have shown the critical potential of oxide-metal transition processes for a Cu oxide foam annealed at 300 °C in air probed by operando XAS, X-ray diffraction (XRD), and Raman spectroscopy techniques.[9,10]Using Cu K-edge Quick-XAS technique, we aim to understand the potential-dependent reduction of different Cu2+:Cu+ ratios to Cu0 for nanoporous CuxO foam precursor catalysts under CO2RR conditions. The CuxO foams were prepared by electrodeposition and subsequent thermal annealing between 100 and 450 °C in air to generate the different Cu2+:Cu+:Cu0 ratios. Initially, from ex-situ XANES, XRD, and XPS analyses, we found that a rise in annealing temperature leads to an increase in the proportion of Cu2+ species and their degree of crystallinity within the CuxO foams. After annealing at 100 °C and 200 °C, the CuO phase/species are amorphous and mainly found at the surface of the foam. Once the annealing temperature reaches 300 °C or higher, the CuO phase is entirely crystalline.With these different chemical states of the precursor catalyst, the Cu oxide-metal transition kinetics during cathodic potential increment (ΔE = 100 mV), step (ΔE > 100 mV), and jump (ΔE > 500 mV) experiments in CO2-saturated 0.5 M KHCO3 were comprehensively investigated using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and Linear Combination Fit (LCF) analyses of the operando Cu K-edge Quick-XANES data. Our results demonstrate that different oxide-metal transition kinetics were found strongly dependent on the initial abundance of Cu2+ species and precursor structure (ordered vs. amorphous) as well as on the applied potential protocol to the CuxO foam precursor catalysts. More precisely, a high initial population of crystalline CuO, which is found for the CuxO foams annealed at 300 °C and 450 °C, leads to a significant shift of the oxide-metal transition potential towards lower cathodic overpotentials. For example, for the CuxO foam annealed at 450 °C (rich in crystalline CuO phases) the oxide-metal transition potential is shifted to 0 VRHE, while for the foam annealed at 100 °C this transition occurs at – 0.6 VRHE. Furthermore, smaller potential increments increase the formation and accumulation of Cu+ species, thereby slowing down the reduction kinetics. For the CuxO foam annealed at 200 °C, we could observe a full reduction to metallic Cu if jumping from OCP directly to – 0.5 VRHE, whereas no full reduction took place if using incremental potentials before applying – 0.5 VRHE.Overall, we show the substantial influence of crystalline CuOand the applied potential protocol on the reduction of CuxO foam precursor materials to metallic Cu during CO2RR.

Influence of Relaxation Time on Jelly Roll Deformation and Lithium Plating during Cycling of Cylindrical Lithium-Ion Cells

The conventional approaches of estimating the lifecycle of lithium-ion batteries utilize battery ageing models combined with data from accelerated ageing tests. Despite the prevalent use of these accelerated techniques in battery research over the years, there still exists a lack of consistency in the testing parameters and methodology. Particularly in cycle ageing tests, the rest period between cycles is typically selected without a standard criterion and is generally minimised to facilitate higher cycle throughput. Although this parameter has been considered to have minimal influence on the test results1, a recent study2 has demonstrated that cycle-to-cycle relaxation may have a significant impact on the cell cycle life, even though the investigated cells were cycled in otherwise identical conditions. This work aims to expand on the findings presented in2, by investigating the underlying mechanism of this behaviour, using X-ray CT imaging, forensic and post-mortem analysis.In this study, commercially available cylindrical lithium-ion cells were subjected to prolonged cycling with different rest periods between cycles. For the relaxation time after discharge, three time constants were selected, namely 1min, 10min and 60min, while the relaxation period after charge was kept constant at 1min. The cells were cycled at 10°C between the charge/discharge voltage cut-off limits specified by the manufacturer, with 0.3C/1C current rate for charge/discharge respectively. A clear correlation between relaxation time and cell degradation was observed in the cycling results, as the cells cycled with longer rest periods exhibited higher capacity fade (Fig.1(a)). Non-invasive diagnostic analysis conducted with differential voltage (DVA) and incremental capacity (ICA) revealed increased losses of lithium inventory and active material in the longer relaxation test cases. As the main relaxation time was after discharge, when the cells were at a low SOC and in sub-ambient temperature (10°C), calendar ageing effects are expected to be negligible, which indicates the presence of a different underlying mechanism responsible for the observed degradation pattern.At the end of the cycle ageing test, X-ray computed tomography (XCT) scans were obtained for all the tested cells, and one cell per test case was selected to be dismantled for autopsy and visual inspection. The XCT images revealed severe deformations in the jelly roll of all tested cells, in the form of kinks located in the innermost layers, between the cell's hollow core and the positive current collector tab (Fig.1(b)). Furthermore, the cell structural integrity appears to deteriorate as the relaxation period increases, since more jelly roll layers appear to be affected in the 10min and 60min test cases (Fig.1(b)). Upon dismantling, significant electrode delamination was observed in the innermost electrode areas for all test cases (Fig.1(c)-(e)), which was inherently linked to the jelly roll deformation. For the cells cycled with 60min relaxation, a bright coloured passivation layer was detected in the mid to outer layers of the negative electrode (Fig.1(e)-(f)), implying the potential occurrence of lithium plating3. Furthermore, the opposing parts of the cathode electrode corresponding to the location of the passivation layer in the anode exhibited a unique wave-like deformation pattern (Fig.1(f)), which indicates that these jelly roll regions where subjected to high mechanical stresses during cycling. The autopsy results support the preliminary diagnostic conclusions, as the presence of the covering layer and the morphological changes in the electrodes can lead to loss of active lithium and active material, due to local passivation and particle cracking.Overall, this study demonstrates that longer cycle-to-cycle relaxation periods cause higher mechanical and electrochemical stresses within the tested lithium-ion cells, which can even lead to the formation of local passivation layers, affecting their electrochemical performance and structural integrity. This effect, which has not been previously reported, does not appear to be present in all cells, as a preliminary investigation conducted with three different commercial cells of similar format did not exhibit the same trend. Although the underlying mechanisms responsible for the results presented in this study needs to be investigated further, the potential influence of relaxation on the cycling behaviour of lithium-ion cells needs to be considered in the design and interpretation of accelerated ageing tests. Reichert, D. Andre, A. Rösmann, P. Janssen, H. G. Bremes, D. U. Sauer, S. Passerini, and M. Winter, Journal of Power Sources, 239 45-53 (2013). G. Darikas, A. Barai, M. Sheikh, P. Miller, M. Amor-Segan, and D. Greenwood, in "Electrochemical Society Meeting s 242", p. 2590-2590. The Electrochemical Society, Inc., 2022. A. J. Smith, Y. Fang, A. Mikheenkova, H. Ekström, P. Svens, I. Ahmed, M. J. Lacey, G. Lindbergh, I. Furó, and R. W. Lindström, Journal of Power Sources, 573 233118 (2023). Figure 1

A New Generation of Protective Coating Materials Based on CuMn1.7Fe0.3O4-Me2O3 (Me=Y, Gd) Ceramic Bilayers for Solid Oxide Cells Interconnect

In SOCs (solid oxide cells) technology, coating of interconnects is one of the main processes that determine the long-term operation of the stack. Currently, the main material used for interconnects are steels with high chromium content (e.g. Crofer 22 APU). They are known for their high resistance towards high-temperature corrosion due to the formation of passivation layer composed of chromium oxide. This oxide is characterized by relatively high conductivity compared to other single metal oxides, but at the same time, chromium evaporation causes cathode poisoning, what causes a significant decrease in the cell efficiency. Coating the interconnects reduces the thickness of chromium oxide layer and also protects the cathode. Materials used as protective coatings must be characterized by an appropriate coefficient of thermal expansion (suitable for steel, sealant and cathode) and high electrical conductivity, because target value of the area specific resistance cannot exceed 0.1 Ω cm2. Currently, the state of the art coating material is MCO (MnCo2O4), which is characterized by high conductivity and very good protection against chromium diffusion. Due to the fact that cobalt is a critical element for many areas, it was immediately necessary to find cobalt-free alternatives.This work will present the research on the spinel material CuMn1.7Fe0.3O4 in combination with a single metal oxide – Y2O3 or Gd2O3. These combinations were made due to high affinity of the spinel material for chromium, and thin base layers of single metal oxides were intended to reduce the diffusion of chromium into the spinel layer. The layers were deposited using two techniques – electrolytic and electrophoretic deposition. The prepared samples with the layers fabricated in three configurations were subjected to oxidation tests at a temperature of 700 °C for 4000 hours. The reaction kinetics was determined by measuring weight gain and determining the Kp coefficient and instantaneous Kp. Electrical resistance measurements were also performed at various stages of oxidation to demonstrate the changes occurring during the oxidation. SEM-EDS measurements allowed for the assessment of the quality of the layer, the distribution of the elements, the thickness of chromium oxide layer and the efficiency for suppression chromium diffusion. Confocal Raman imaging, X-ray adsorption spectroscopy and X-ray diffraction measurements allowed to demonstrate potential changes occurring in the material. The results indicated very good corrosion protection properties with good chromium diffusion blocking properties. A very low value of the area specific resistance was obtained, which after 4000 hours of oxidation ranged from 8 to 20 mΩ cm2, depending on the type of a sample. Acknowledgement This research has been supported by National Science Centre (NCN) Harmonia 9 project number UMO-2017/26/M/ST8/00438: ‘Quest for novel materials for solid oxide cell interconnect coatings’.

Influence of Chloride and Electrolyte Stability on Passivation Layer Evolution at the Negative Electrode of Mg Batteries Revealed by operando EQCM-D.

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2)- and magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2)-based electrolytes, each with and without MgCl2, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)4]2-based electrolytes, highly efficient and interphase-free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so-called initial conditioning process. With the more reactive Mg(TFSI)2-based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode.

Einfluss von Chlorid und Elektrolytstabilität auf die Bildung von Passivierungsschichten an der Negativen Elektrode von Mg Batterien: eine operando EQCM‐D Studie

AbstractWieder aufladbare Magnesium Batterien sind vielversprechend für die zukünftige Energiespeicherung. Ihre praktische Anwendung wird jedoch unter anderem durch niedrige Coulomb'sche Effizienzen bei der Magnesiumabscheidung und ‐auflösung behindert. Grundlegende Prozesse wie die Bildung, Struktur und Stabilität von Passivierungsschichten und der Einfluss verschiedener Elektrolytbestandteile auf diese sind immer noch nicht vollständig verstanden. In dieser Studie erhalten wir einzigartige Einblicke in die ersten Magnesiumabscheidungs‐ und auflösungszyklen, indem wir Magnesium bis(trifluoromethansulfonyl)imid (Mg(TFSI)2)‐ und Magnesium tetrakis(hexafluoroisopropyloxy)borat (Mg[B(hfip)4]2)‐basierte Elektrolyte, jeweils mit und ohne MgCl2, operando auf Goldelektroden mittels hochempfindlicher elektrochemischer Quarzmikrowaage mit Dissipationsmessung (EQCM−D) unter Anwendung hydrodynamischer Spektroskopie vergleichen. Mit den stabilen Mg[B(hfip)4]2‐basierten Elektrolyten ist hocheffizientes und Interphasen‐freies Zyklieren möglich, während die Bildung von Passivierungsschichten Elektrolytverunreinigungen zugerechnet werden kann. Diese bilden sich und degradieren während des sogenannten Konditionierungsprozesses. Mit dem reaktiveren Mg(TFSI)2‐basierten Elektrolyten wachsen während des Zyklierens dicke Passivierungsschichten mit kleinen Poren. Wir zeigen, dass die Zugabe von MgCl2 bei diesen Elektrolyten die Menge an passiviertem Mg verringert und die stromlose Auflösung der Passivierungsschicht beschleunigt. Dies hat einen positiven Effekt, da wir das effizienteste Zyklieren und die gleichmäßigste Abscheidung beobachten, wenn sich keine Interphase auf der Elektrode befindet.

The corrosion-inhibitory influence of graphene oxide on steel reinforcement embedded in concrete exposed to a 3.5M NaCl solution

Steel reinforcement corrosion significantly reduces the durability and service life of concrete structures, particularly in chloride-rich environments such as marine and coastal areas. This study aims to reduce the corrosion rate using graphene oxide (GO) as a corrosion inhibitor. Two GO dosages (0.0005 and 0.005 wt%) were evaluated for their effectiveness in mitigating corrosion in reinforced concrete exposed to a 3.5M NaCl solution. To assess the corrosion behavior of the steel reinforcement, Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), and Linear Polarization Resistance (LPR) were evaluated over one year by wetting/drying cycles. Oxygen permeability and electrical resistivity tests were also conducted to evaluate the concrete's susceptibility to corrosion. Both GO content demonstrated significant corrosion inhibition, with the 0.005 wt% dosage providing the most effective protection. This was evidenced by the lowest icorr values recorded during the final cycle (52), larger capacitive loops, and higher impedance in EIS results, indicating enhanced corrosion resistance. Visual inspection of steel bars further confirmed these findings, showing no signs of deterioration or discoloration in GO-modified concrete compared to steel bars extracted from reference concrete. SEM-EDS analysis revealed higher carbon content on the steel surface, suggesting GO adsorption and the formation of a protective passive layer. These results suggest that GO is a promising nanomaterial for inhibiting corrosion in steel-reinforced concrete exposed to aggressive environmental conditions.

Directly Regenerating of Spent LiCoO2 with Gradient F-Doped Subsurface towards Ultra-Stable Storage Properties.

As great potential recycling strategy, the direct regeneration of spent LiCoO2 (LCO) is beneficial for lowering environmental pollutions and promoting global sustainability. However, owing to the using of binder and electrolyte, some fluorine impurities would be remained into spent materials. Considering the doping behaviors of F-elements, their suitable content introducing would facilitate the energy-storage abilities of regenerated LCO. Herein, through the tailored introduction of F-elements, spent LCO are successfully regenerated with physical-chemical evolutions. Benefitting from the existed oxygen vacancies, the diffusion energy-barrier of F-elements is reduced from 1.73 eV to 0.61 eV, facilitating the establishment of gradient F-doped subsurface, along with the formation of rigid CoO5F. Meanwhile, excess F-elements (1 wt %, as a threshold) lead to the formation of LiF passivation layer on the surface. Thus, the as-optimized sample displays a considerable capacity of 154.4 mAh g-1 even at 5.0 C, with retention rate (88.3 %) in 3.0-4.5 V. Supported by detailed electrochemical and kinetic analysis, the structural advantages are confirmed to boost the improved redox activity of Co-ions and the alleviating of irreversible oxygen-release. Give this, the work is anticipated to reveal the evolutions of regenerated LCO with the introduced F-elements, whilst providing the practical regeneration strategies toward excellent high-voltage properties.

Directly Regenerating of Spent LiCoO2 with Gradient F‐Doped Subsurface towards Ultra‐Stable Storage Properties

AbstractAs great potential recycling strategy, the direct regeneration of spent LiCoO2 (LCO) is beneficial for lowering environmental pollutions and promoting global sustainability. However, owing to the using of binder and electrolyte, some fluorine impurities would be remained into spent materials. Considering the doping behaviors of F‐elements, their suitable content introducing would facilitate the energy‐storage abilities of regenerated LCO. Herein, through the tailored introduction of F‐elements, spent LCO are successfully regenerated with physical‐chemical evolutions. Benefitting from the existed oxygen vacancies, the diffusion energy‐barrier of F‐elements is reduced from 1.73 eV to 0.61 eV, facilitating the establishment of gradient F‐doped subsurface, along with the formation of rigid CoO5F. Meanwhile, excess F‐elements (1 wt %, as a threshold) lead to the formation of LiF passivation layer on the surface. Thus, the as‐optimized sample displays a considerable capacity of 154.4 mAh g−1 even at 5.0 C, with retention rate (88.3 %) in 3.0–4.5 V. Supported by detailed electrochemical and kinetic analysis, the structural advantages are confirmed to boost the improved redox activity of Co‐ions and the alleviating of irreversible oxygen‐release. Give this, the work is anticipated to reveal the evolutions of regenerated LCO with the introduced F‐elements, whilst providing the practical regeneration strategies toward excellent high‐voltage properties.

Investigation of kinetics of passive layer formation on various microstructures in thermo-mechanically treated steel in simulated concrete pore solution

Carbon steel bars are critical in steel-reinforced concrete structures, and their corrosion can lead to significant deterioration. This research explored the passive layer formation on different carbon steel microstructures using a high throughput approach. Thermomechanically treated steel bars with three distinct microstructures, i.e., martensite in the outer layer, bainite in the middle, and pearlite in the center, were vertically cut and immersed in the simulated concrete pore solution. Scanning electrochemical microscopy was employed to study the formation of the passive layer, the kinetics of the passivation, and the effective rate constant of the species inside the solution on each microstructure. Results showed that the formation of the passive layer is a time-dependent process, and passivation was influenced by the local microstructure. Martensite demonstrated superior passivation behavior compared to pearlite and bainite.

Elucidating the effect of strain path-dependent crystallographic texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy

This research provides insight into the effect of strain path-dependent texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy in a phosphate buffer solution (pH = 8.3). To achieve this, AA2024 alloy sheets were processed using two methods: accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), i.e., rotating the sheets 90° around the normal direction (ND) axis between each cycle. The ARB-processed AA2024 alloy exhibited a pancake-shaped structure and included texture components of Copper {112}<111>, Brass {011}<211>, P {110}<221>, and S {123}<634>. Meanwhile, the CARB-processed AA2024 alloy had extremely fine and equiaxed nano-grains (< 100 nm) and texture components of S {123}<634>, Brass {011}<211>, Goss {011}<100>, Rotated Cube {001}<110>, and P {110}<221> after eight cycles. Electrochemical studies demonstrated an increase in corrosion current density due to high imposed strains in the ARB route, which in effect made the conditions of passive layer formation more difficult and lowered the corrosion resistance. Additionally, achieving a more uniform distribution of extremely fine grains and {011} orientation textures such as Brass {011}<211>, Goss {011}<100>, and P {110}<221> texture components in the CARB route, provided ideal conditions for forming oxide passive films with superior protection properties compared to ARB. These unique findings can contribute to the broader application of crystallographic-orientation-dependent electrochemical behavior of alloys in the field of corrosion management.

Understanding the role of alloying elements Cr, Ni in erosion–corrosion process of nuclear grade austenitic stainless steel 304 L by total reflection X-ray fluorescence

Stainless steel (SS) has gained an indispensable position as one of the most widely used industrial material. In nuclear industry, it is one of the technologically most important structural materials used in pressure tube, containment vessel and reprocessing-related applications. In fact, SS 304 L is the workhorse material of the reprocessing plant which faces the hostile conditions of acid, temperature as well as high radiation dose. These conditions can affect the erosion-corrosion behavior of the material and can lead to poor mechanical properties. This also affects the life of the reactor components. In the present study, a systematic work has been carried out to develop an in-depth understanding of the Corrosion Rates (CRs) with respect to the loss of major and minor elements from SS into the corrosive nitric acid medium using Total reflection X-Ray Fluorescence (TXRF). The effect of acid molarity as well as temperature, on the erosion-corrosion behavior of SS304L was studied. The TXRF studies have revealed that the CR was maximum in 2 M HNO3 and minimum in 8 M, showing that the nitric acid molarity has an important role to play in the corrosion and as the molarity increases, the passivation of SS 304 L also increases. This observation was further corroborated with the concentrations of Fe, Cr and Ni, which had leached into the nitric acid medium. The role of alloying elements, Cr and Ni, in the passivation of SS was also studied. The effect of temperature showed that at 45 °C, the rate of corrosion was minimum, as compared to at 25 °C and 90 °C which reveals that the formation of chromium oxide passive layer was thermodynamically most favorable at this temperature.

Effects of Strontium Modification on Corrosion Resistance of Al-Si Alloys in Various Corrosive Environments.

This study investigates the impact of strontium (Sr) additions on the corrosion resistance of an LM6 (A413) aluminium alloy. By incorporating varying concentrations of Sr (0.01 wt.% and 0.05 wt.%), the morphological and corrosion behaviours of the alloy were analysed under different corrosive environments, including sulphuric acid, sodium hydroxide, and sodium chloride solutions. The results demonstrate that Sr modifications significantly enhance the alloy's corrosion resistance, with the most substantial improvement observed at 0.05 wt.% Sr. The analysis revealed that the weight loss of the alloy in sulphuric acid decreased by 2.5% with 0.05 wt.% Sr after 10 days of immersion, due to the formation of a stable passive oxide layer. In sodium hydroxide, however, the weight loss was reduced by 5% with 0.05 wt.% Sr after 10 days, indicating aggressive uniform corrosion. In the 3.5% sodium chloride solution, the corrosion rates remain relatively low, and the 0.05 wt.% Sr alloy showed a decrease in corrosion product formation over time, suggesting enhanced resistance. Detailed surface analyses, including 3D profiling and morphology assessments, revealed that Sr additions refine the eutectic silicon phase, transforming it from a coarse to a more desirable fibrous or lamellar structure, thus improving the alloy's overall performance. The innovative findings underscore the potential of Sr as an effective microstructural modifier for enhancing the durability and longevity of Al-Si alloys in corrosive environments.

Towards electrochemical machining of powder superalloy René 88DT with high surface integrity in different solvent-based electrolytes

Electrochemical machining (ECM) presents numerous applications in the production of aero-engine components. The effects of current density on surface quality during ECM of René 88DT in NaCl-ethylene glycol and NaNO3-aqueous solutions was investigated here. The results indicated that the René 88DT surface has lower sensitivity to current density and more homogeneous electrochemical dissolution in NaCl-glycol solution than in NaNO3-aqueous solution, which results in the suppression of stray corrosion and consistently high surface quality regardless of current density. These strengths are attributed that C2H5O2- and Cl- ions replace OH– ions and combine with alloy ions to form solubles and complexes, which prevent the formation of obstructive passive film, oxide layer, and insoluble electrolytic products. The electrochemical dissolution model in two solutions was established. Furthermore, the high tensile strength and precision machinability of René 88DT in NaCl-glycol solution were also demonstrated.