Main Cathode Research Articles

Research of Cathode Materials for Sodium-Ion Batteries

Sodium-ion batteries are being extensively studied as a replacement for lithium-ion batteries in some areas. However, there are also some problems with cathode materials at present. Sodium-ion batteries perform worse performance than lithium-ion batteries, which is due to the properties of sodium. For instance, sodium ions possess a greater ionic radius and increased atomic weight compared to lithium ions. This piece presents an overview of the operational principles behind sodium-ion batteries, examining the preparation techniques, structure, and effectiveness of three main cathode materials. Moreover, the current challenges of cathodes and the corresponding solutions for sodium-ion batteries are systematically recognized. This article provides a new perspective or idea for solving the problem of sodium-ion battery cathode.

Comparative Analysis of Single- and Poly-Crystalline Layered Cathode Materials: Determining the Superior Choice

In the field of cathode material candidates of lithium-ion batteries, there has been ongoing debate regarding which material is superior: poly-crystalline (PC) or single-crystalline (SC) cathode active materials. The PC materials are characterized by primary particles that agglomerate into secondary particles, which PCs are prone to micro-crack due to significant c-axis volumetric expansion/contraction in their lattice structure.As an alternative, the SC materials have been received attention for their physical resistance from the expansion/contraction and external pressure. However, in terms of lithium-diffusion pathway, it has been reported that SC’s structures possess certain disadvantages in lithium-ion diffusion compared to PC materials. This is attributed to the scarcity of grain boundaries and the extensive pathways of bigger primary particles in SC, which impede the efficient movement of lithium ions. Even though the comparative analysis has been needed between PC and SC above superiority, achieving an exact comparison under identical or similar conditions is challenging due to differences in particle size and surface environment, including binders and conducting materials.In this study, we standardized the size of both PC and SC particles to 10 μm to evaluate their electrochemical performance under identical environmental conditions and using a common commercial electrode composition (96:2:2, active material, carbon black, and PVDF binder) in a wet process with a 60% nickel cathode (NCM622). Consequently, in comparing PC and SC materials, the focus has been on analyzing key factors that contribute to electrode performance, specifically concerning issues of lithium-ion diffusion and the composition of materials at the electrode level that may arise. Moreover, we fabricated SC electrodes using a solvent-free dry electrode process as an alternative of better process, aimed at creating higher energy density electrodes without the addition of carbon black, but rather by employing coated carbon nanotubes (CNT) on the SC surface with the composition (99.6:0:0.4, active material, carbon black, PTFE binder) to clarify the comparison between two main cathodes’ design.Finally, we found that the dry-processed SC electrode demonstrated superior performance in full-cell tests and show excellent cycle performance at high temperature (45 °C) and high voltage (2.8 to 4.5V). The enhanced performance observed in dry-processed electrodes using CNT was found to be primarily due to the reduced ion resistance in environments devoid of internal carbon black, as confirmed through comparison with wet-processed electrodes. Although electron conductivity was ensured through the conductive material, a significant decrease in performance was noted if the environment was not conducive to the movement of internal lithium-ion. And it is attributable to enhanced surface stability under high-voltage storage conditions with a reduced specific surface area compared to PC cathode and PC wet process condition. Figure 1

Operando chemo-mechanical evolution in LiNi0.8Co0.1Mn0.1O2 cathodes.

Ni-rich LiNi x Co y Mn z O2 (NCMxyz, x+y+z=1, x≥0.8) layered oxide materials are considered the main cathode materials for high-energy-density Li-ion batteries. However, the endless cracking of polycrystalline NCM materials caused by stress accelerates the loss of active materials and electrolyte decomposition, limiting the cycle life. Hence, understanding the chemo-mechanical evolution during (de)lithiation of NCM materials is crucial to performance improvement. In this work, an optical fiber with με resolution is designed to in operando detect the stress evolution of a polycrystalline LiNi0.8Co0.1Mn0.1O2 (P-NCM811) cathode during cycling. By integrating the sensor inside the cathode, the stress variation of P-NCM811 is completely transferred to the optical fiber. We find that the anisotropy of primary particles leads to the appearance of structural stress, inducing the formation of microcracks in polycrystalline particles, which is the main reason for capacity decay. The isotropy of primary particles reduces the structural stress of polycrystalline particles, eliminating the generation of microcracks. Accordingly, the P-NCM811 with an ordered arrangement structure delivered high electrochemical performance with capacity retention of 82% over 500 cycles. This work provides a brand-new perspective with regard to understanding the operando chemo-mechanical evolution of NCM materials during battery operation, and guides the design of electrode materials for rechargeable batteries.

Activation and degradation mechanisms of α-V2O5 cathode materials in Zn-ion battery

Vanadium oxides with high specific capacity have been widely used as cathode materials for aqueous Zn-ion batteries. However, the interactions between the aqueous electrolytes and Vanadium oxides are still unclear. In particular, the intercalation of proton and water which can play a critical role in the degradation process is less well understood. Moreover, the mechanism for the capacity increase during the electrochemical cycling, known as the activation process, is still under debate. In this study, we systematically investigated the α-V2O5||Zn battery system with state-of-the-art characterization tools and electrochemical testing techniques to reveal the activation and degradation processes. It is discovered that the activation can be mainly attributed to the intercalation of protons and water in the first 100 cycles, which destabilizes the overall structural integrity, leading to capacity degradation afterward. It is also revealed that two main cathode electrolyte interface (CEI) components can be formed on the cathode surface, namely Zn3(V2O7)(OH)2·2H2O and Znm(CF3SO3)n(OH)2m-n·nH2O. The formation of Zn3(V2O7)(OH)2·2H2O-based CEI component is irreversible, while Znm(CF3SO3)n(OH)2m-n·nH2O-based CEI component can be reversibly cycled. Different structure-stabilizing charge/discharge protocols are proposed accordingly, which could leverage the structural integrity with thorough phase transition in the activation stage to enhance the cycling performance of the V-based cathodes. We hope to spur further interest in the fundamental understanding of the cathode materials in Zn-ion batteries.

Elaborating the Crystal Water of Prussian Blue for Outstanding Performance of Sodium Ion Batteries.

Prussian blue (PB) is one of the main cathode materials with industrial prospects for the sodium ion battery. The structural stability of PB materials is directly associated with the presence of crystal water within the open 3D framework. However, there remains a lack of consensus regarding whether all forms of crystal water have detrimental effects on the structural stability of the PB materials. Currently, it is widely accepted that interstitial water is the stability troublemaker, whereas the role of coordination water remains elusive. In this work, the dynamic evolution of PB structures is investigated during the crystal water (in all forms) removal process through a variety of online monitoring techniques. It can be inferred that the PB-130 °C retains trace coordination water (1.3%) and original structural integrity, whereas PB-180 °C eliminates almost all of crystal water (∼12.1%, including both interstitial and coordinated water), but inevitably suffers from structural collapse. This is mainly because the coordinated water within the PB material plays a crucial role in maintaining structural stability via forming the -N≡C-FeLS-C≡N- conjugate bridge. Consequently, PB-130 °C with trace coordination water delivers superior reversible capacity (113.6 mAh g-1), high rate capability (charge to >80% capacity in 3 min), and long cycling stability (only 0.012% fading per cycle), demonstrating its promising prospect in practical applications.

Analysis of the technology of electrochemical production of zirconium

To date, reactor-grade zircon is produced on an industrial scale using metallothermic and electrochemical methods. Electrolytic production of reactor-purity zirconium in a sealed electrolyzer is more cost-effective than metallothermic production, as it does not require iodide refining and the use of reducing metals (Na, Mg, and Ca). Despite the importance of this production, its features are not fully described in the literature. This study presents the results of industrial tests of the electrolysis process in a sealed electrolyzer with a current load of 10 kA from the molten electrolyte KCl–KF–K2ZrF6. Based on the achieved technological indicators, the current efficiencies of the main cathode and anode reactions were determined and the factors influencing them were evaluated. We analyzed the composition of nutrient salts and the mechanism of accumulation of potassium fluoride in the electrolyte, an increase in which concentration leads to an anode-destroying effect. We considered possible mechanisms of the electrochemical formation of freons and compiled material balances for all starting substances and reaction products. The change in the electrolyte density during electrolysis was calculated, which allowed justifying the volume of its daily drainage. Fine carbon and zirconium powder formed in the electrolyte due to the interaction with potassium metal are not separated and are removed for chemical redistribution, which reduces the productivity of the electrolysis process.

CALCULATION OF THE ELECTRODE REACTION RATE ON A GRAPHITE CATHODE OF ALUMINUM-ION BATTERY WITH 1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE

A method for determining the rate of sorption of chloraluminate complexes on graphite material as the main cathode reaction in aluminum-ion batteries with an ionic liquid as an electrolyte is proposed in terms of classic chemical kinetics approach. The method is applied to the description of the rate of a one-electron cathode reaction that is in the case the sorption/desorption of complexes on the electrode surface with no migration in the interlayer space of graphite taken into account. The experimental part is based on the selection and providing of measurement conditions and the ratio of the components of the cell to ensure that the rate of the cathode process sets the rate of current generation of the cell. The rate of supply/removal of electrons, as participants in the reaction, thus can be directly related to the reaction rate on graphite. The point of reaching the limiting current on the polarization curve in that case corresponds the limiting rate of the chemical sorption reaction. The approach takes into account the effect of other limiting processes, such as the rate of removal/supply of electrons, the rate of removal/supply of ions to/from the electrolyte volume, and the rate of anodic dissolution/deposition of aluminum. The calculated value of the reaction rate for graphite material grade EC-02 and low-temperature ionic liquid 1-ethyl-3-methylimidazole chloride in a mixture with aluminum chloride (1 : 1.3) was calculated to be 46 µmol/cm2 · s.

Titration Techniques for the Determination of Surface Species on Cathode Active Materials

Lithium ion batteries (LIBs) are the most important energy storage technology of our time. The number of LIBs has been constantly growing during the last years as well as the range of applications where LIBs are used, increasing the need for high energy density LIBs.One of the main cathode materials for high energy density LIBs is Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811).1 Unfortunately, due to the high Ni content this material is extremely sensitive towards water which poses a particular challenge for more sustainable aqueous processing. Contact with even traces of moisture from the air causes immediate formation of surface species such as LiOH and Li2CO3.2,3 The presence of these surface species not only leads to Li leaching from the structure and subsequent capacity loss but also facilitates side reactions with the electrolyte resulting in gas evolution and ultimately early failure of the battery.4 Developing reliable methods for the quantification of these harmful surface species can provide a link between the amount of surface species and the detrimental impact on the cell performance. Here we employed different measurement techniques to quantify the amount of LiOH and Li2CO3 on the NCM811 material surface.5 Warder titration6 and Winkler titration7 are two methods that have been long known for the determination of hydroxides and carbonates. We optimized these techniques for the determination of very small quantities of surface carbonate or hydroxide by testing the sensitivity for small lab size quantities of material and removing the possibility of additional CO2 uptake through the air. Titration as a way to quantify the amount of LiOH and Li2CO3 is a valuable measurement technique that can help to predict performance issues of the battery and can serve as a tool for quality control of cathode active materials. References (1) Armand, M.; Axmann, P.; Bresser, D.; Copley, M.; Edström, K.; Ekberg, C.; Guyomard, D.; Lestriez, B.; Novák, P.; Petranikova, M.; Porcher, W.; Trabesinger, S.; Wohlfahrt-Mehrens, M.; Zhang, H. J. Power Sources 2020, 479, 228708.(2) Hofmann, M.; Kapuschinski, M.; Guntow, U.; Giffin, G. A. J. Electrochem. Soc. 2020,(3) Jung, R.; Morasch, R.; Karayaylali, P.; Phillips, K.; Maglia, F.; Stinner, C.; Shao-Horn, Y.; Gasteiger, H. A. J. Electrochem. Soc. 2018, 165 (2), A132–A141.(4) Kim, Y. J. Mater. Sci. 2013, 48 (24), 8547–8551.(5) Schuer, A. R.; Kuenzel, M.; Yang, S.; Kosfeld, M.; Mueller, F.; Passerini, S.; Bresser, D. J. Power Sources 2022, 525 (231111).(6) Benedetti-Pichler, A. A.; Cefola, M.; Waldman, B. Ind. Eng. Chem. - Anal. Ed. 1939, 11 (6), 327–332.(7) Winkler, C. Praktische Übungen in Der Maßanalyse, 5. Auflage.; Verlag von A.Felix: Leipzig, 1920.

Dendrite-free zinc anodes via self-assembly of graphene nanoribbon for long-life aqueous zinc-ion batteries

Aqueous zinc ion batteries (AZIBs) are considered as one of the most promising aqueous energy storage devices due to their advantages of low cost, high capacity, and safety. However, a series of problems such as corrosion, hydrogen evolution, and dendrite of the zinc anode significantly hinder the application of AZIBs. In this work, graphene nanoribbons (GNRs) are initiated as a novel functional interface layer via a facile self-assembly process based on the redox reaction of graphene oxide nanoribbons (GONRs) and Zn foil, which is found to be able to act as an ion buffer layer and guide Zn2+ to nucleate uniformly at the zinc anode, thus successfully prevents the formation of passivated by-products and reduces the occurrence of hydrogen evolution reaction and serious dendrite growth. As a result, GNRs@Zn exhibits lower nucleation overpotential (18.7 and 36.5 mV at 0.2 and 1 mA cm−2), higher reversibility (≈17 times higher than that of bare Zn), and dendrite-free durability compared to the original zinc in this synergy. In addition, GNRs@Zn anode exhibits excellent compatibility with the main cathodes of rechargeable AZIBs, such as ZnxV2O5 and MnO2 cathode, among which GNRs@Zn//ZnxV2O5 full battery delivers ultra-long cycle life of more than 9000 cycles with capacity retention of 105% at 5 A g−1, showing great prospect in practical application. This work provides a new idea for realizing high-performance rechargeable zinc-based battery systems.

Galvanic corrosion behavior of Cu-Fe-Zn trimetallic couple in acidic media

The galvanic corrosion behavior of Cu-Fe-Zn trimetallic couple and its factors were investigated in acidic chloride solution using electrochemical and numerical methods. Results demonstrated that the potential difference of galvanic couple reflects only the thermodynamic tendency of galvanic corrosion, while the cathodic kinetic process controls the galvanic corrosion rate. It is found that the galvanic effect between Cu and Zn is much less than that between Zn and Fe when ohmically coupled. This is opposite to the theory of galvanic series. Despite possessing the maximum corrosion potential difference as the driving force, the galvanic current of Zn-Cu couple is less than that of Zn-Fe couple with equal area ratio. This drives the intermediate metal (Fe) to act as the main cathode in Cu-Fe-Zn trimetallic couple. Furthermore, it is found that Fe can be transformed into the anode due to the area change of Cu. The electrochemical experimental results are in good agreement with the FEM, suggesting that this method can accurately predict the galvanic corrosion behavior of multielectrode systems.

Revealing Lithium Configuration in Aged Layered Oxides for Effective Regeneration.

Layered oxides LiNixCoyMnzO2 are widely used as the main cathode material for high-energy lithium-ion batteries. Over long-term cycling, irreversible phase transformations in layered oxides usually occur along with the loss of active lithium, which directly reflects in the sharp decrease of capacity. However, it is difficult to accurately and rapidly determine lithium content in aged materials, raising extreme impediments in the direct recycling of layered oxides. Herein, we propose a facile method for quick and accurate calculation of the residual lithium content through the developed relationship of shear strain and the states of charge. Based on this recognization, a discharge capacity close to the original capacity of the pristine material is achieved in the regenerated material by combining a hydrothermal method with annealing treatment. The recycled material demonstrates a dramatic improvement in electrochemical properties, especially the high rate performance. This method not only effectively realizes the quantitative regeneration of cathode materials but also provides a possible strategy for the future development of direct regeneration.

MoWS2 Nanosheet Composite with MXene as Lithium-Sulfur Battery Cathode Material

Due to their superior theoretical specific capacity and energy density, lithium-sulfur (L‒S) batteries are gaining popularity in order to achieve the growing terms for more power generation. However, drawbacks such as low electrical conductivity of the active ingredient sulfur, severe volume expansion and shuttle effect of polysulfides, rapidly decaying battery capacity, and short battery life have hampered their development. A MoWS2@MXene@CNT composite material is used as the main cathode material for L-S batteries in this study. MoWS2 can improve the electrochemical reaction rate by accelerating polysulfide conversion, whereas MXene can suppress electrode volume expansion. Furthermore, the addition of carbon nanotubes (CNT) with high electrical conductivity improves the rate of the electrochemical reaction. Therefore, the MoWS2@MXene@CNT composites have good capacity and versatility as cathode materials and enhance the behavior of L-S batteries.

Optimization Fungal Leaching of Cobalt and Lithium from Spent Li-Ion Batteries Using Waste Spices Candlenut

Lithium-ion battery (LIB) applications in consumer electronics nowdays are rapidly growing resulting the increase of batteries solid waste containing toxic and corrosive substances for the environment. On the other hand, the main active cathode components in LIB are Lithium and Cobalt, which are hazardous and limited in nature but are valuable metals. This study aims to use bio-hydrometallurgical techniques to recover heavy metals from LIB using microorganisms to avoid toxic waste from used solvents which are usually generated in conventional chemical leaching. Filamentous fungi have an important role in secreting citric acid and several organic acids to facilitate the dissolution of metal ions from the metal solids. Self-grown fungi, Aspergillus niger isolated from waste spices (Candlenut) was used as a leaching agent. Route based on fungal activity was evaluated to optimized the detoxification and metal recovery from spent LIB in various conditions (one-step, two-step and spent medium bioleaching) in 21 days of incubation. The quantitative result of XRF and EDX analysis of battery powder before and after bioleaching confirm that fungal activities are quite effective. The maximum recovery of both metals (Cobalt and Lithium) in leached liquor reached up to 72% analyzed using ICP-OES with the one-step leaching method. With respect due to the high metal recovery, fungal leaching has proven to be an easy and cost-effective green metallurgical method for recycling heavy metals in used LIBs.

A Comparative Analysis of the Capacity Fading Mechanisms in Ni-Rich Single-Crystal and Polycrystalline Cathodes

Layered [Ni1–x–yCox(Mn or Al)y]O2 (NCM or NCA) oxides are the main cathode materials for powering current electric vehicles. Increasing the Ni fraction is the primary approach to increase the energy density of NCM and NCA cathodes, and thus enhancing the driving range of associated electric vehicles. However, high–Ni NCM and NCA cathodes with Ni contents near 90% suffer from inherent structural instability, especially in the deeply charged state, resulting in rapid capacity fading and high thermal instability. One method to address this inherent structural instability involves removing the interparticle boundaries by growing a single-crystal cathode. Single-crystal cathodes, free from interparticle microcracking, are regarded to improve cycling and thermal stability by minimizing parasitic surface degradation. Despite mechanical stability, the single-crystal cathode has some problems. In this presentation, we report a comprehensive evaluation of the fundamental properties of single-crystal and polycrystalline cathodes with a wide range of Ni-rich compositions. The electrochemical performances of single-crystal and polycrystalline cathodes are correlated with their structural changes to elucidate the dominant capacity fading mechanism of single-crystal cathodes.

Characterization of Corrosion Behavior of TA2 Titanium Alloy Welded Joints in Seawater Environment.

Titanium alloy has been widely used in Marine pipeline system because of its excellent corrosion resistance. However, there are differences in microstructure and electrochemical properties because of the heterogeneous structure of the welded joint, the corrosion behavior is often different. In this paper, the corrosion behavior of TA2 titanium alloy welded joint in seawater at different temperatures was studied by traditional macro electrochemical test analysis combined with microelectrode array test and surface morphology analysis. Conventional macroscopic electrochemical analysis results show that the corrosion resistance of heat-affected zone is always the best, followed by the base metal and the weld. And the higher the temperature, the easier the formation of passivation film. The results of microelectrode array test show that the heat-affected zone is always the cathode region of the whole welded joint, and part of the cathode near the base metal region has the largest current density, which acts as the main cathode to slow down corrosion. At slightly higher temperatures, the polarity deflection will occur in the base metal zone and weld zone due to the different formation speeds of passivation film in early corrosion stage. With the prolongation of corrosion time, the base metal eventually becomes the cathode zone and the weld zone eventually becomes the anode zone.

Topological Quantum Cathode Materials for Fast Charging Li‐Ion Battery Identified by Machine Learning and First Principles Calculation

AbstractFast charging electrode materials require excellent ion conductivity as well as high and stable electrical conductivity. However, the main commercial cathode materials are semiconducting transition metal oxides suffering from low electrical conductivity, so cathode materials with good electrical conductivity are highly desirable. It is well‐known that topological quantum materials (TQMs) can exhibit robust electrical conductivity, thus providing a promising solution to this problem. The key question becomes which TQMs can have high ionic conductivity. Herein, such topological quantum cathode materials for fast charging Li‐ion battery are identified by using machine learning combined with first‐principle calculation, where the supervised regression models are trained for diffusion energy barrier prediction. Among 7385 TQMs, 20 materials are found to have a diffusion energy barrier less than 1.0 eV. Especially, LiMnAs exhibits a reversible capacity of 195.9 mAh g−1, higher than that of commercial cathodes while with comparable diffusion energy barrier. Furthermore, LiMnAs shows high interface stability with selected solid lithium metal oxides electrolytes. This study not only opens a new path to developing novel cathode materials, but also expands the applications of TQMs.

Study of the operating modes of the electrostatic lens of the welding electron gun

The paper presents the results of a study of the operating modes of a technological electron gun used in installations for electron beam welding. The design of an electron gun, which is part of the ELA-15I power complex, is considered, and the results of modeling the accelerating gap for a new design gun with an accelerating voltage of 120 kV are presented. The current-voltage characteristics of the gun operation were experimentally obtained at different temperatures of the main LaB6 cathode. For this, the beam current was recorded at different values of the control electrode potential. A mathematical model of the accelerating gap was implemented, which makes it possible to analyze the shape of the electron beam in the region of the first lens. Using a mathematical model, the shapes of the electron beam were calculated for various operating modes of the gun, and the characteristic transverse size of the beam in the crossover was determined. The beam diameter and the angle of convergence in the area of focusing the beam on the product were determined experimentally. Conclusions were made about the equality of the crossover diameters of the full-scale and mathematical models, as well as about the sufficient coincidence of the experimental and calculated volt-ampere characteristics. The design of the accelerating gap of the ELA-15 gun was optimized with an increase in the accelerating voltage from 60 kV to 120 kV. The optimization results are shown for the original and modified design in the form of a comparison of the patterns of the distribution of the electrostatic field strength and a comparison of the current-voltage characteristics.

A Sealed-Off Pseudospark Switch With Nanosecond Stability of Triggering

This article describes the modified version of the commercially produced pseudospark switch TPI1-10k/50 (pulsed current-10 kA and anode voltage-up to 50 kV) and the results of testing. The main idea of the modification was to use the high-voltage electrode system of this switch but to incorporate the novel trigger unit in the main cathode cavity. This unit uses the auxiliary glow discharge with hollow cathode and hollow anode. The modified switch is intentionally developed for parallel operation of a large number of the switches to a common load. In such conditions, the nanosecond triggering stability of the switches is required. The results of tests demonstrate that the minimum delay time of triggering (the time interval between the instant of arrival of the trigger pulse and the instant of starting the main discharge current) amounts to 80 ns with a jitter of 3 ns. At a decreased hydrogen pressure, the delay time is not increased essentially and amounts to 105 ns with a jitter of 6 ns.

Modelling of multiple-hollow-cathode-discharge laser

A laser tube configuration for metal vapour lasers with hollow cathode sputtering is theoretically studied. The construction consists of a main hollow cathode and a few hollow cathode holes. Optimal conditions for laser oscillation are realised inside the main cathode, while the current density in the side hollow cathodes is higher and the discharges that occur in the hollow cathode holes can be used as additional sources of metal atoms produced by sputtering. To study the processes in the discharge and the unique capabilities of the construction the PLASIMO modelling platform is used.

Effects of temperature on the corrosion behaviour of X70 steel in CO2-Containing formation water

The corrosion behaviour of X70 pipeline steel in CO2-containing formation water at various temperatures was studied in a high-temperature and high-pressure reactor via weight loss measurements, scanning electron microscope, X-ray diffraction, energy dispersive spectroscopy, and electrochemical methods. The concentrations of CO2 and ions in formation water at 30–150 °C were calculated. The equilibrium potentials of anodic and cathodic reactions were determined by thermodynamic equations, and the main cathode reaction was hydrogen ion reduction. X70 steel showed the uniform corrosion in the temperature range of 30 °C–90 °C and the localized corrosion at 120 °C and 150 °C. The supersaturation (S) was not proportional to the protection effect of FeCO3 scale. At 30 °C, the deposition rate of FeCO3 was too slow to form a protective film, so the corrosion rate was high. At 60 °C, the deposition rate of the FeCO3 was lower than the rate of film undermining and the corrosion product scale was non-protective. At 90 °C, although the S was the smallest, the FeCO3 scale was dense and protective. At 120 °C, the size of FeCO3 crystals increased significantly. A void space was formed between the grown grains and the matrix surface, whereas the immature grains still showed the good density and had the protection effect on the matrix. At 150 °C, the rapid growth of FeCO3 crystals led to the increase in the stress in the FeCO3 scale and the scale finally ruptured. H+ produced in the ionization reactions of H2CO3 and HCO3− resulted in local acidification and pitting corrosion.