Corrosion of Li-ion battery cathode materials on mullite insulation materials during calcination

A specially designed experimental device was used in laboratory to investigate the corrosion of mullite during the calcination of Li(Ni_xCo_yMn_z)O₂ (LNCM) materials. The anti-corrosion tests were carried out at 1000, 1100, 1200 and 1300 °C, and characterized with X-ray diffraction and scanning electron microscopy. The influence of temperature on the interactions between mullite insulation materials and LNCM materials was determined. In addition, the high-temperature creep properties of the mullite insulation materials before and after corrosion were tested. The laboratory scale tests, thermodynamic and kinetic calculations allowed a more comprehensive understanding of the evolution of the mullite insulation materials during serving for the roasting process of LNCM materials. Through this research, it is suggested that the upgrading of the kiln lining in the lithium battery industry should select materials with excellent resistance to alkali corrosion, especially excellent resistance to Li⁺ corrosion.     

Firing properties and corrosion resistance of mullite-Al2TiO5 saggar materials

Conventional refractory materials used for calcining ternary lithium-ion battery cathode materials, such as mullite, cordierite, and magnesia-alumina spinel, are vulnerable to attack by Li(Ni_xCo_yMn_1−x−y)O₂ (LNCM) materials and therefore have a short service life. In order to improve the corrosion resistance of refractory materials to LNCM materials, mullite-Al₂TiO₅ materials with different contents were synthesized in this paper by using calcined mullite powder, TiO₂ powder, and La₂O₃ powder as raw materials, which were calcined at 1500–1600°C temperature, respectively. In this study, the potential of the materials for the preparation of LNCM materials was investigated in terms of its physical properties, resistance to the corrosion of LNCM materials, and resistance to thermal shock. The results showed that mullite-Al₂TiO₅ composites can be successfully synthesized at 1500–1600°C, and the physical properties of the materials met the production requirements. The prepared mullite-Al₂TiO₅ composites also exhibited better physical properties, good corrosion resistance, and proper thermal shock resistance compared with mullite refractories.     

Anti-corrosion effect of insulating firebrick coated with CA6 in the calcination of lithium-ion cathode materials

The anti-corrosion properties of calcium hexaluminate (CA6) during the roasting of Li(Ni_xCo_yMn_z)O₂ (LNCM) materials have been investigated by means of specific experimental setups and test methods to verify its feasibility as an adiabatic insulation material for the roasting kiln of LNCM materials. Mullite insulating firebrick currently in industrial use was coated with CA6 (labelled M-CA6) and corrosion tests were carried out. The corrosion tests were carried out at different additions of corrosion sources, roasting temperatures, number of cycles of corrosion experiments. And the materials before and after corrosion characterized by the X-ray diffraction and scanning electron microscopy to determine the influence of different corrosion conditions on the interactions between M-CA6 and LNCM materials. In addition, The corrosion resistance of calcium CA6 and the feasibility of its application in practical industry was identified by characterising and comparing the high-temperature creep properties of the materials. The results of the laboratory scale experiments confirmed that M-CA6 was more resistant to LNCM than mullite insulating firebrick, and confirmed the feasibility and superiority of using CA6 as a lining insulation for LNCN kilns.     

Effect of aggregate particle content on sintering and corrosion resistance of hibonite-cordierite saggar

An effective method to improve the corrosion resistance of the saggar to the cathode material for Li-ion batteries is to reduce the reaction between Li₂O and the components of the saggar matrix material. Saggars are multi-component and multi-graded functional materials, in which aggregate particles are an important factor in resisting corrosive media. Consequently, in this study, hibonite with good alkali corrosion resistance was selected as the main raw material to prepare hibonite-cordierite composite saggars with different aggregate particle contents. The effect of the aggregate particle content on the sintering performance and corrosion resistance of CA₆-M₂A₂S₅ saggars was systematically studied. The results show that the optimal hibonite aggregate content for saggar performance is 40 wt%, its bulk density is 2.44 g/cm³, and the cold and hot moduli (1100 °C × 30 min) of rupture are 15.66 MPa and 14.67 MPa, respectively, the strength retention rate of the sample after five thermal cycles at 1100 °C × 30 min was 53.30%. Additionally, during the sintering process, a dense anorthite protective layer was formed along the edges of the CA₆ particles, which hindered the reaction between the positive electrode material and saggar sample body, thereby improving the corrosion resistance of the saggar.     

Research on saggars of lightweight design used to prepare cathode materials for Li-ion batteries

The focus of lightweight refractory is equivalent volume replacement that uses lower-density raw materials to replace the original high-density raw materials. In this study, we employ porous mullite microspheres (PMM) to replace mullite particles to realize the weight-lighting of mullite–cordierite saggars used to prepare cathode materials for Li-ion batteries.To confirm that lightweight saggars satisfy the quality standards of production, we conducted various tests, including mechanical properties, thermal shock stability and corrosion resistance. Compared with samples with mullite particles, samples with PMM have a comparatively stable material structure and excellent performance. Furthermore, PMM reduce mullite consumption and enhance their resistance to prevent stress shedding in the corrosion process.     

Synthesized K2O·11Al2O3 as sagger matrix for the preparation of Li-ion battery cathode materials at high temperatures

Refractory materials such as mullite, andalusite, forsterite, and cordierite are generally used to prepare saggers for the calcination of Li-ion battery Li(Ni_xCo_yMn_z)O₂ (LNCM) cathode material. However, these compounds are prone to be attacked by the LNCM materials, thereby leading to short life spans and contamination of the Li-ion battery cathode materials. To improve the corrosion resistance of refractory sagger materials, the most clear cut-way is enhancing the corrosion resistance of matrix using a new refractory component. Potassium aluminate (K₂O·11Al₂O₃, KA₁₁) with an excellent corrosion resistance against alkaline oxide was synthesized via solid-state method using potassium carbonate (K₂CO₃) and industrial alumina powder (Al₂O₃). Interactions between KA₁₁ and LNCM cathode materials at 800°C–1100°C were characterized by refractory-LNCM precursor laboratory-scale tests to understand the corrosion behavior of KA₁₁. The microstructure and phase composition of synthesized KA₁₁ and the calcined KA₁₁-LNCM mixture cylinders were analyzed with SEM and XRD. The observations reveal that KA₁₁ shows a better corrosion resistance to LNCM materials compared with mullite, cordierite, and forsterite. The addition of synthesized KA₁₁ also favors the thermal shock resistances of mullite-based sagger materials.     

Comparison of interactions of MgO-based refractories with Li-ion battery cathode materials during calcination

To select refractory major ingredients of saggers for the calcination of Li-ion battery cathode Li(Ni_xCo_yMn_z)O₂ (LNCM) materials, interactions between MgO-based refractories, ie, magnesium aluminate (MgAl₂O₄) spinel, forsterite (2MgO·SiO₂), and cordierite (2MgO·2Al₂O₃·5SiO₂), and LNCM materials were compared respectively via refractory-LNCM precursor cylinder testing in lab-scale. The phase composition and microstructure evolution of the calcined cylinders were characterized and resulted in comprehensive understanding and comparing of degradation of the MgO-based refractories. The results reveal that cordierite is severely corroded, whereas magnesium-aluminate spinel reacts little with LNCM materials. Refractories contain both SiO₂ and Al₂O₃ with a higher SiO₂ level will suffer a more serious corrosion contacting with LNCM materials.     

Surface modification of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials via a novel mechanofusion alloy route

This study aimed to prepare a composite coating material comprising a solid ionic conductor of lithium aluminum titanium phosphate (Li_1.4Al_0.4Ti_1.6(PO₄)₃, LATP) and porous carbon through a sol-gel method. LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811) cathode material with dual-functional composite conductors (i.e., LATP@porous carbon), denoted as LATP-PC, was prepared. The dry-coating method, also called the “mechanical-fusion alloy route,” was used to modify Ni-rich LNCM811 cathode materials. X-ray diffraction (XRD), micro-Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed that the LATP ionic conductor generated herein was uniformly deposited on 3D porous carbon and served as a dual-functional composite coating on LNCM811. Furthermore, the capacity retention of LATP-PC@LNCM811 was approximately 85.57% and 80.86% after 100 cycles at −20 °C and 25 °C, respectively. By contrast, pristine LNCM811 had the capacity retention of 78% and 74.96% at −20 °C and 25 °C, respectively. Furthermore, the high-rate capability of the LATP-PC@LNCM811 material was markedly enhanced to 169.81 mAh g⁻¹ at 10C relative to that of pristine LNCM811, which was approximately 137.67 mAh g⁻¹. The electrochemical performance of LNCM811 was enhanced by the uniform dual-conductive composite coating. The results of the study indicate that the LATP-PC@LNCM811 composite material developed herein is a potentially promising material for future high-energy Li-ion batteries.     

Phase composition of alumina–mullite–zirconia refractory materials

Refractories in the Al₂O₃–SiO₂–ZrO₂ system are widely used in many applications, for ceramic rollers in particular, and are characterized by high mechanical strength, excellent thermal shock resistance, resistance to corrosion by alkaline compounds and low creep at high temperature. Their performances greatly depend on the amount and chemical composition of crystalline and glassy phases, which were investigated by quantitative XRPD (RIR–Rietveld) and XRF in order to assess the effect of various Al₂O₃/SiO₂ ratios of starting batches and different alumina particle size distributions. Refractories consist of mullite, corundum, zirconia polymorphs and a vitreous phase in largely variable amounts. The mullite percentage, unit cell parameters and composition vary with sintering temperature, being mostly influenced by the Al₂O₃/SiO₂ ratio of the batch. Its orthorhombic unit cell increased its volume from 1400 to 1500 °C, while its stoichiometry became more aluminous. The corundum stability during firing is strongly affected by the Al₂O₃/SiO₂ ratio, but not by the particle size distribution of alumina raw materials. Zirconia raw materials are involved in the high temperature reactions and about one-third of the available ZrO₂ is dissolved in the glassy phase, ensuring excellent resistance to alkali corrosion, mainly depending on the fraction of coarse alumina. The phase composition of the vitreous phase increased with sintering temperature, being over 20% when the fractions of coarse alumina in the starting batch are between 0.2 and 0.5.     

Improving the electrochemical performance of Ni-rich cathode materials using a fast ion conductor coating of Li2O–B2O3–LiBr

The high-Ni layered metal oxide, LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811), has received widespread attention in the energy field because of its high specific capacity, but its large-scale applications are hindered due to severe capacity fading. Herein, a uniform and thin Li₂O–B₂O₃–LiBr-glass (LBBrO-glass) coating was deposited on LNCM811 by a liquid-phase coating and thermal treatment method. The experimental results suggested that the LBBrO-glass coating acted as a protective layer that inhibited transition metal dissolution and side reactions, which helped improve the electrochemical properties of LNCM811. Remarkably, after 200 cycles, the 2 wt% coating (LBBrO@LNCM-2) delivered a superior capacity retention of 88.9%, while only 71.8% was obtained for the pristine material (LNCM811). The discharge capacity of LBBrO@LNCM-2 was 163.5 mAh g^?1 at 5C, while it was only 139 mAh g^?1 for the pristine material.     

Andalusite: An amazing refractory raw material with excellent corrosion resistance to sodium vapours

The chemical attack of alumina refractories by sodium vapours is far from been completely understood. In order to contribute to a better knowledge of this attack, a laboratory test was developed to simulate the sodium gaseous corrosion of different raw materials and refractories.Corrosion of alumina raw materials by sodium vapours is due to a dissolution–precipitation process by a Na₂O rich liquid phase. The gaseous corrosion strongly depends on the microstructures and the assemblage of phases in alumina raw materials. Fire clay and andalusite raw materials exhibit very high corrosion by Na vapours. In spite of an initial high silica glass content, and as a result of trapping of the main part of the glass in the capillary network of the mullite composite crystal, mullitised andalusite leads to excellent corrosion resistance which is close to monocrystalline fused mullite.Consequently, The use of mullitised andalusite particles in the matrix of alumina refractories limits the liquid phase formation during corrosion by sodium gas. These experimental results are in agreement with thermodynamic calculations.     

Damage mechanism and corrosion resistance improvement of corundum-mullite kiln furniture during calcining of Li-ion cathode materials

In order to improve the cleanliness of cathode materials of Li ion batteries (LIBs), it is necessary to develop and apply advanced kiln furniture. Low-impurities Corundum-mullite materials (CMM) with were prepared, and the damage mechanism in LNCM production was studied. Innovatively amplify the corrosion process in the form of prefabricated cracks and explore their interaction mechanism. Based on the corrosion mechanism, Si-Al sol was selected as a binder to replace PVA. The corrosion resistance of CMM with Si-Al sol was significantly improved. With the improvement of calcination temperature and purity requirements of LIBs, the research and development of this advanced CMM kiln furniture has a good application prospect in the future.     

Effects of in situ synthesized mullite whiskers on flexural strength and fracture toughness of corundum-mullite refractory materials

The method of in situ synthesis of mullite whiskers was introduced to improve the fracture toughness of the corundum-mullite refractory materials. Effects of process parameters (sintering temperature, holding time and addition amount of V₂O₅) on flexural strength and fracture toughness of corundum-mullite during the in situ toughening course were analyzed. The optimum process parameters (the sintering temperature of 1350 °C, the holding time of 2 h, and the V₂O₅ addition amount of 5%) for in situ synthesized mullite whiskers to toughen corundum-mullite were obtained by the response surface method combined with single factor analysis. SEM and EDS analysis results demonstrated that the mullite whiskers had been synthesized in corundum-mullite and they could bridge the cracks during the fracture process. After in situ toughening, the flexural strength versus deflection curves of corundum-mullite showed obvious zigzag or waveform characteristics, indicating in situ toughening effects. At the same time, the flexural strength and corresponding deflection increased remarkably.     

A study on the wetting behavior of liquid iron on forsterite,mullite, spinel and quasi-corundum substrates

Wetting characteristics of liquid iron on magnesia, alumina and silica mixture substrates were studied by sessile drop experiments. Chromium-free forsterite, mullite, spinel and quasi-corundum phases were selected as alternative refractories in MgO-Al₂O₃-SiO₂. Morphological changes of molten electrolytic iron on the oxide substrates were investigated via apparent contact angle measurements. The results showed that the wetting behavior was significantly influenced by FeO compounds that were formed via oxidation of the liquid iron. Morphologies of the reacted layer were studied by Scanning Electron Microscope (SEM)/EDX analysis. The ternary phases FeO-MgO-SiO₂ and FeO-Al₂O₃-SiO₂ improved the wetting of liquid iron on the forsterite and mullite substrates by providing liquid phases at solid (refractory)–liquid (iron) interfaces. However, corrosion by liquid iron was significantly inhibited at spinel phase which did not feature FeO based compounds at the interface. Quasi-corundum (10MgO-25SiO₂-65Al₂O₃) showed a much enhanced resistance to liquid iron compared to forsterite or mullite refractories.     

Hot corrosion of cordierite/mullite composites by Na-salts

Cordierite/mullite (C/M) ceramic composites were corroded by NaCl and Na₂SO₄ at 1000 °C for 24 h. The predominant corrosion products in attack by the Na-salts were found to be nepheline and carnegieite for the cordierite and mullite component, respectively. NaCl attacked both components with different corrosion rates, producing corrosion layers consisting of two distinct regions where both cordierite and mullite were chemically attacked near the surface region and only the cordierite phase was damaged in the succeeding inner part. In the hot corrosion by Na₂SO₄, on the other hand, only the cordierite component was severely attacked in the composites, resulting in occurrence of selective corrosion. Thus, the corrosion of the C/M composites by the Na-salts proceeded through the path of the less resistive cordierite component at 1000 °C in air.     

Study on the corrosion resistance of cordierite-mullite and SiC refractories to Li-ion ternary cathode materials

The corrosion reactions of Li-ion ternary cathode material on cordierite-mullite and SiC refractories were studied at 780 °C for 20 h. The XRD and SEM technologies were used to study the corrosion process. The results showed that the interaction between Li₂O and cordierite-mullite material produced a large number of reactants, which led to the failure of cordierite-mullite refractories. For SiC refractories, a small amount of SiO₂ were formed by the SiC oxidation reaction, then the SiO₂ reacted with Li₂O to form lithium silicate compound. Moreover, Li₂O tended to diffuse into the interior of SiC refractory slabs through pores, which avoided the formation of a large amount of reaction products and gave good corrosion resistance to the material without damaging its structure. It has been found that the corrosion resistance of the two materials can be effectively improved by the alumina sol impregnation method.     

Influence of iron on the occurrence of primary mullite in kaolin based materials: A semi-quantitative X-ray diffraction study

Iron-enriched reference kaolins (KGa-1b, KGa-2 and KF) were used to study the effect of iron on the development of mullite phases during the sintering of kaolin-based materials. Up to 1050 °C, primary mullite formation occurred at earlier temperature within iron-enriched kaolins than in the case of iron-free kaolins. At 1150 °C, the presence of ferric ions tended to promote the transformation of the spinel (γ-Al₂O₃-like) phase into primary mullite. This action was correlated with an enhancement of the diffusion mechanism of the main constitutive species of the samples (Al, Si). In the range 1300–1400 °C, iron-enriched kaolins exhibited an abnormal grain growth of secondary mullite crystals and a partial reduction of hematite (Fe₂O₃) into magnetite (Fe₃O₄). These two iron compounds reacted with mullite and cristobalite, leading to the occurrence of eutectic liquids as expected from phase equilibrium diagrams.     

Mechanical and fracture properties of zircon–mullite composites obtained by direct sintering

Refractory materials based on zircon (ZrSiO₄) are applied in high temperature applications (1400–1500 °C). They are demonstrated to have an excellent chemical attack resistance, such as corrosion or degradation due to molten glass or metals. On the other hand mullite (3Al₂O₃2SiO₂) is important both in traditional and advanced ceramics. Although multi-phase ceramic materials were always used, nowadays composite materials have an important industrial and technological development, to enlarge the designing capability of the manufacturer in properties and behaviors. The objective of the present work is to study the influence of the starting composition on the mechanical and fracture properties of zircon–mullite composites obtained by direct sintering of consolidated samples by slip cast of concentrated aqueous suspensions in plaster molds. Zircon–mullite composites using 15–45 wt% mullite were prepared and compared with pure zircon material obtained in the same conditions. Flexural strength (σ_f), dynamic elastic modulus (E), toughness (K_IC) and initiation fracture surface energy (γ_NBT) were evaluated. The results were explained by microstructure and the XRD analysis. The presence of mullite increased the zircon thermal dissociation. The ZrO₂ was a product of this reaction and also influence the mechanical and fracture properties of these materials through several combined mechanisms.Zircon composites prepared with 45 wt% of mullite in the starting powder showed a higher fracture toughness and initiation energy than ceramics derived from pure zircon. Microstructure consisting in mullite as a continuous predominant phase in which zircon and zirconia grains were distributed improved almost all the mechanical and fracture properties.     

The effect of SrSO4 and BaSO4 on the corrosion and wetting by molten aluminum alloys of mullite ceramics

In order to improve the corrosion resistance of aluminosilicate refractories by molten aluminum, SrSO₄ and BaSO₄ powders were used. Mullite substrates with and without addition of 20 wt.% SrSO₄ or BaSO₄ were sintered at 1400 °C for 6 h. Corrosion and wetting experiments with molten pure Al and Al–7.5Si were carried out at 900 °C for 24 h and 900 °C for 2 h, respectively. The corrosion layer was thicker in the mullite sample (≥2 mm) than that of the SrSO₄- or BaSO₄-containing mullite samples (<50 μm). The contact angles for mullite samples containing SrSO₄ or BaSO₄ were higher (≈118° and 149°) than those of the mullite sample (≈109° and 127°), with both pure aluminum and Al–7Si alloy. This increase in the contact angle improves the corrosion resistance in mullite samples by means of non-wetting effect.     

Flower-like hierarchical Li1.2Ni0.13Co0.13Mn0.54O2 by architectural design for lithium-ion batteries with superior capacity retention

In this work, hierarchical flower-like Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LNCM) with exposed {010} planes assembled and double-sphere Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ without {010} planes as a comparison were successfully synthesized via a simple solvothermal method. The diffusion of Li⁺ could be enhanced in the flower-like LNCM with exposed {010} active planes, and the cathode exhibits a superior electrochemical performance especially in long-term cycling stability even at high current densities. The initial discharge capacity of this sample is 274 mA h g⁻¹ at 0.1C (25 mA g⁻¹), with corresponding initial coulombic efficiencies of 77%. Especially, the capacity retention reaches up to 98% at 1250 mA g⁻¹ current density after 100 cycles. By comparing with other LNCM materials reported recently, our optimal cathode has a pretty outstanding electrochemical performance, which is promising for the next generation lithium ion batteries.