A lithium battery can coating and a method of making the same

Abstract

The present application relates to a kind of lithium battery box coating and its preparation method, belong to refractory material technical field, comprising: alumina, zirconium oxide, magnesium oxide and silicon oxide are mixed according to specific mass ratio, obtain the basic powder of 1 μm~5 μm particle size;1%~3% high-purity rare earth oxide is added to it, and form uniform mixed powder by ball milling;Mixed powder is mixed with water glass solution to make slurry and be coated on the surface of box, control thickness is 0.5mm~1.5mm;Subsequently, two-stage drying is carried out;Finally, three-stage sintering is carried out in air atmosphere, and the highest sintering temperature is 1300 DEG C~1400 DEG C and keeps temperature.The present application effectively improves the compactness, chemical stability, thermal shock resistance and the bonding strength with matrix of coating by introducing rare earth oxide and combining optimized subsection drying and sintering process, so as to significantly enhance the corrosion resistance and service life of box.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a lithium battery crucible coating and its preparation method. Background Technology

[0002] In the preparation of lithium-ion battery cathode materials, the sagger serves as a crucial tool for support and sintering, and its performance directly impacts the quality and production efficiency of the cathode material. During the high-temperature sintering process, lithium-ion battery cathode materials generate highly corrosive substances (such as molten lithium salts). These substances easily erode the sagger surface, shortening its lifespan and potentially contaminating the cathode material, thus affecting battery performance. Therefore, developing sagger coatings with excellent corrosion resistance, thermal shock resistance, and long lifespan has become a key focus of industry research.

[0003] In the prior art, for example, patent document CN105777090A discloses a sagger with a high-temperature corrosion resistant coating for lithium batteries and its preparation method (hereinafter referred to as "Prior Art 1"). Prior Art 1 involves impregnating the surface of the sagger blank with a glaze composed of Al2O3, SiO2, ZrO2, MgO, and Li2O, followed by high-temperature sintering to form the coating. While this method effectively prevents the lithium-ion solution from corroding the sagger, it still has the following shortcomings: the coating contains Li2O, which may react with the cathode material, thus affecting battery performance; the coating thickness is relatively large (2-3 mm), easily leading to thermal stress concentration and decreased thermal shock resistance; the sintering temperature is high, reaching 1450℃, resulting in high energy consumption, and the coating uniformity is difficult to control, leading to a short service life of approximately 20 cycles. Furthermore, Prior Art 1 does not fully consider optimizing the thermal shock resistance of the sagger during multiple cycles of use, which may affect its long-term stability.

[0004] For example, patent publication number CN113372105B discloses a technical solution for a double-layer structure crucible for lithium battery cathode materials and its preparation method (hereinafter referred to as "Prior Art 2"). Prior Art 2 uses a combination of a substrate layer and a surface coating, preparing the crucible through steps such as premixing aggregates, processing and molding, surface coating mixing and slurry preparation, and high-temperature sintering. Its advantage lies in its good resistance to Li-. + Co 2+ It exhibits excellent corrosion resistance to erosion, along with good thermal shock stability and a certain compressive strength. However, this technology still has certain limitations: the selection of surface coating components mainly focuses on traditional refractory material systems (such as SiC-Si3N4 composite materials), failing to fully integrate the advantages of new composite materials to further improve the overall performance of the coating; in addition, the existing technology 2 does not pay enough attention to the bonding strength between the coating and the substrate, which poses a risk of coating peeling during high-temperature sintering or long-term use.

[0005] Furthermore, patent document CN115340409A discloses a crucible coating for lithium-ion battery cathode materials and its preparation method (hereinafter referred to as "Prior Art 3"). Prior Art 3 uses raw materials such as cordierite, mullite, kaolin, corundum, spinel, magnesium oxide, aluminum oxide, magnesium fluoride, spodumene, silicon carbide fiber, and binder, and forms the coating through a vacuum filtration method. Although this technology reduces the sintering temperature by combining magnesium fluoride and silicon carbide fiber, it has the following problems: rare earth oxides are not introduced into the coating composition, resulting in insufficient coating density and chemical stability, and limited corrosion resistance; although the vacuum filtration process can fill pores, it is difficult to ensure the uniformity of the coating and the bonding strength with the substrate, and microcracks or peeling are prone to occur during long-term high-temperature use; at the same time, its composition system is relatively complex, and there is still room for improvement in thermal shock resistance.

[0006] In summary, while existing technologies have improved the corrosion resistance and service life of crucible coatings to some extent, there is still room for improvement in areas such as coating uniformity, thermal shock resistance optimization, and the bonding strength between the coating and the substrate. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a lithium battery crucible coating and its preparation method.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for preparing a lithium battery crucible coating includes the following steps:

[0010] S10: Alumina, zirconium oxide, magnesium oxide and silicon oxide are mixed in a mass ratio of 5-7:2-4:1-3:1-2 to obtain a basic powder;

[0011] S20: Add 1% to 3% of rare earth oxides with a purity of ≥99.5% by mass to the base powder and form a uniformly mixed powder by ball milling; the rare earth oxides are used to promote grain densification and optimize the thermal expansion behavior of the lithium battery crucible coating during subsequent sintering.

[0012] S30: Mix the uniformly mixed powder with the water glass solution at a mass ratio of 10 to 15:1, and stir evenly to form a slurry;

[0013] S40: Apply the slurry to the surface of the sagger, with the coating thickness controlled between 0.5mm and 1.5mm;

[0014] S50: Place the coated crucible in a drying oven for drying. The drying process is divided into two stages. The first stage is drying at 50℃~80℃ for 1h~2h. The second stage is heating up to 100℃~150℃ and maintaining it for 1h~2h.

[0015] S60: The dried sagger is sintered in an air atmosphere, and then cooled to obtain the coated sagger. The sintering process is divided into three stages: the first stage is to heat from room temperature to 600℃~800℃ at a heating rate of 5℃ / min~10℃ / min; the second stage is to heat from 600℃~800℃ to 1300℃~1400℃ at a heating rate of 3℃ / min~5℃ / min; the third stage is to hold at 1300℃~1400℃ for 3h~6h to obtain the lithium battery sagger coating.

[0016] This invention introduces rare earth oxides into the base powder, enhancing the density and chemical stability of the coating. Its mechanism of action encompasses filling the micropores of the coating, promoting grain densification during sintering, and optimizing thermal expansion behavior by forming low-expansion grain boundary phases. Furthermore, this invention selects high-purity rare earth oxides (such as cerium oxide, purity ≥99.5%) and controls the sintering atmosphere to be air, avoiding the formation of low-melting-point phases and ensuring the stability of the coating at high temperatures. The addition of rare earth oxides also considers compatibility with the base powder; uniform dispersion through ball milling reduces the risk of impurity introduction. In addition, precise control of sintering temperature and time helps form a stable interfacial bonding layer between the coating and the substrate, reducing the risk of delamination.

[0017] To ensure the fluidity and coating performance of the subsequent slurry, the particle size distribution of the base powder in S10 is in the range of 1μm to 5μm.

[0018] Furthermore, in S10, the mass ratio of aluminum oxide, zirconium oxide, magnesium oxide and silicon oxide is 6:3:2:1 or 7:2:3:1 or 6:2:1:1.

[0019] To ensure the uniformity of the mixed powder, in step S20, the ball milling time is 4 h to 8 h, the ball milling medium is zirconia balls, the ball-to-material mass ratio is 5 to 10:1, and the ball milling speed is 200 r / min to 400 r / min.

[0020] Preferably, in S30, the water glass solution has a modulus of 2.5 to 3.5 and a mass fraction of 30% to 40%, with a moderate viscosity that ensures both the fluidity of the slurry and enhances the adhesion between the coating and the substrate.

[0021] To prevent the slurry from drying too quickly and causing cracks on the coating surface, in step S40, the coating method is spraying or brushing, and the coating environment temperature is controlled at 20℃~30℃ and the relative humidity is 40%~60%.

[0022] In addition, the present invention also provides a lithium battery crucible coating prepared by the above method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) In this invention, 1% to 3% of high-purity rare earth oxides are added to the base powder, and a uniformly mixed powder is formed by ball milling. This step can fill the micropores of the coating and promote grain densification during sintering. Furthermore, by controlling the sintering atmosphere, this invention avoids the formation of low-melting-point phases. At the same time, the grain boundary filling and thermal expansion optimization effects of rare earth oxides are closely related to the segmented process, significantly enhancing the density and thermal stability of the coating. Experiments show that the corrosion depth of Examples 1 to 5 with added rare earth oxides is only 4.3 to 8.5 μm, while the corrosion depth of Comparative Example 1 without added rare earth oxides is as high as 15 μm, demonstrating the key role of rare earth oxides in blocking the erosion of corrosive substances such as lithium salt molten material.

[0025] Furthermore, the introduction of rare earth oxides enhances the chemical inertness of the coating, reduces side reactions with the cathode material at high temperatures, and effectively avoids side reactions that may be caused by the use of active components such as Li2O in prior art 1, thereby preventing performance degradation of the crucible due to corrosion. This improvement not only extends the service life of the crucible but also reduces the risk of cathode material contamination, which is of great significance for ensuring the quality and consistency of lithium battery cathode materials.

[0026] (2) In this invention, a uniformly mixed powder and a water glass solution are mixed at a mass ratio of 10 to 15:1. The modulus of the water glass solution is controlled at 2.5 to 3.5, and the mass fraction is 30% to 40%. This ratio ensures the fluidity and adhesion of the slurry, avoiding uneven coating caused by unsuitable viscosity. Compared with the complex composition and high process requirements of the glaze system in prior art 1, the uniformity control problem brought about by the vacuum filtration process in prior art 3, and the problem of uniform component distribution in the coating slurry in prior art 2, the coating thickness of this invention is strictly controlled between 0.5 mm and 1.5 mm. The coating method is spraying or brushing, and the ambient temperature is controlled at 20℃ to 30℃ and the relative humidity at 40% to 60%. These conditions work together to prevent coating defects caused by excessively fast drying or abnormal flow of the slurry. Experiments show that the coating of this invention performs well in thermal shock cycling tests (45 to 58 cycles). In contrast, the performance of Comparative Example 2 declined due to unoptimized process. This fully demonstrates the positive effect of uniform coating on resisting thermal stress and corrosion. This optimization not only improves the protective performance of the coating, but also effectively reduces local stress concentration, thereby enhancing the reliability of the crucible during multiple cycles of use.

[0027] (3) The present invention employs a segmented drying process, which effectively reduces the internal stress of the coating and avoids cracking. The drying process is divided into two stages: the first stage is drying at 50℃~80℃ for 1 h~2 h, and the second stage is heating to 100℃~150℃ and maintaining it for 1 h~2 h. This segmented heating method allows the moisture in the coating to evaporate slowly, reducing volume shrinkage and stress concentration caused by rapid drying. Experiments show that the coating of the present invention achieves a bonding strength of 22~26 MPa in the bonding strength test, while Comparative Example 2, which did not use segmented drying, has a bonding strength of only 18 MPa, proving the effect of segmented drying on enhancing the adhesion between the coating and the substrate. In the present invention, the segmented drying process and rare earth oxide modification work together to provide a more uniform precursor with lower internal stress for the subsequent sintering stage by regulating the distribution and activation of rare earth oxides. This plays a key role in the grain boundary filling and thermal expansion optimization of the final coating (see Table 8).

[0028] (4) This invention employs a segmented sintering process, which promotes the orderly growth of grains within the coating and reduces the impact of thermal stress. The sintering process is divided into three stages: the first stage involves heating from room temperature at a rate of 5°C / min to 10°C / min to 600°C to 800°C; the second stage involves heating at a rate of 3°C / min to 5°C / min to 1300°C to 1400°C; and the third stage involves holding at 1300°C to 1400°C for 3 to 6 hours. This segmented control allows the coating material to gradually adapt to temperature changes, promoting uniform grain growth and densification, while reducing internal stress caused by thermal expansion mismatch. Although the sintering temperature is not high (1300°C to 1400°C), high density is achieved through the reduction of sintering activation energy by rare earth oxides and the segmented process. Compared to the higher sintering temperature (1450°C) in prior art 1, the sintering process in prior art 3, and the lack of segmented control in prior art 2, this invention effectively reduces energy consumption while ensuring coating performance. Experiments show that the coating of the present invention has a low porosity of 2.5% to 4.6% and a hardness of 890 to 1000 HV, while the comparative example 2, which was not sintered in sections, has a porosity of 7% and a hardness of only 800 HV. This indicates that sectioned sintering improves the mechanical properties of the coating.

[0029] Furthermore, in this invention, segmented sintering provides an optimized temperature-time window for the full diffusion and function of rare earth elements at grain boundaries, while rare earth oxides significantly enhance the effect of segmented sintering through their unique properties (such as grain refinement, grain boundary purification, and sintering promotion) as well as grain boundary filling and thermal expansion optimization. The combination of the two achieves the optimization of coating densification, toughness, and low thermal expansion coefficient, which exceeds the effect of using either component or process alone (see Table 8).

[0030] (5) By controlling the sintering temperature and time (sintering at 1300℃~1400℃ for 3 h~6 h), this invention promotes the diffusion bonding between the coating material and the sagger substrate, forming a strong interface layer. Compared with the insufficient bonding strength caused by the vacuum filtration process in the prior art 3, the interface stress problem caused by the thick coating in the prior art 1, and the technical defects of the prior art 2, which pays insufficient attention to the bonding strength between the coating and the substrate and has the risk of peeling, the bonding strength of this invention is between 22 and 26 MPa, while the bonding strength of the unoptimized processes in comparative examples 1 and 2 is only 15 and 18 MPa, respectively. This proves the strengthening effect of the sintering process on the interface bonding. The high bonding strength is not only a direct result of the combined effect of rare earth oxides improving interface wettability and segmented sintering promoting the interdiffusion of interface elements, but also means that the coating is not easy to fall off during high-temperature sintering or multiple thermal cycles, avoiding sagger failure and cathode material contamination caused by coating peeling.

[0031] Furthermore, the increased strength enhances the overall durability of the coating, enabling the crucible to withstand more demanding operating conditions. This improvement is achieved through optimized process parameters, requires no complex equipment, is suitable for mass production, thereby reducing maintenance costs and increasing production efficiency.

[0032] (6) The coating prepared by this invention exhibits excellent comprehensive performance in terms of corrosion resistance, thermal shock resistance, hardness, porosity, and coefficient of thermal expansion. This comprehensive and balanced performance improvement effectively overcomes the shortcomings of prior art 3 in terms of corrosion resistance and bonding strength, the defects of prior art 1 in terms of thermal shock resistance and coating uniformity, and the bottlenecks of prior art 2 in further improving the overall performance of the coating. This performance improvement is mainly attributed to the effective combination of materials, proportions, and processes such as the introduction of rare earth oxides, optimization of slurry ratio, segmented drying, and segmented sintering. For example, low porosity and high hardness enhance the wear resistance and corrosion resistance of the coating; low coefficient of thermal expansion ensures the compatibility of the coating and the substrate under temperature changes and reduces thermal stress; high thermal shock resistance keeps the crucible stable during multiple cycles of use. Therefore, this coating significantly extends the service life of the crucible, reduces the replacement frequency, and improves the production efficiency and economy of lithium battery cathode materials.

[0033] (7) By effectively combining rare earth oxides with segmented drying and sintering processes, this invention improves the long-term stability and comprehensive performance of the coating. It not only solves the problems of easy peeling and insufficient thermal shock resistance of the coating in the prior art, but also makes up for the lack of attention to the bonding strength in the prior art 2. It also provides a more reliable protection solution for the production of lithium battery cathode materials. Detailed Implementation

[0034] This invention provides a method for preparing a lithium battery crucible coating, comprising the following steps:

[0035] S10: Alumina, zirconium oxide, magnesium oxide, and silicon oxide are mixed in a mass ratio of 5–7:2–4:1–3:1–2 to obtain a base powder. The particle size distribution of the base powder ranges from 1 μm to 5 μm, which ensures that the subsequent slurry has good flowability and coating performance.

[0036] S20: 1%–3% rare earth oxides are added to the base powder by mass, and the mixture is ball-milled to form a uniform powder. In this invention, the ball milling is performed in a horizontal ball mill. The mill cylinder is equipped with a cooling water circulation system, with the cooling water flow rate controlled at 5–10 L / min and the inlet temperature at 20°C–25°C to maintain the temperature below 50°C and prevent changes in powder properties due to heat generated by friction during ball milling. The ball milling time is 4–8 hours, the milling media is zirconia balls, the ball-to-material mass ratio is 5–10:1, and the milling speed is 200–400 r / min. The purity of the rare earth oxides is controlled to ≥99.5% to minimize impurity introduction and avoid the formation of low-melting-point phases during sintering. Preferably, cerium oxide is used as the rare earth oxide because it is more stable in air and less likely to react with SiO2 in the base powder to form low-melting-point compounds.

[0037] S30: Mix the uniformly mixed powder with a water glass solution (such as sodium silicate solution) at a mass ratio of 10–15:1, and stir using a mixer at a speed of 200–400 r / min for 30–60 min to ensure that the resulting slurry is uniform and free of lumps. In this invention, the modulus of the water glass solution is 2.5–3.5, and the mass fraction is 30%–40%. It can be adjusted to pH 10–12 by dissolving solid sodium silicate in water in a certain proportion, adding 5% sodium hydroxide solution dropwise, and stirring for 10 min until uniform.

[0038] S40: Apply the slurry to the surface of the crucible, controlling the coating thickness between 0.5 mm and 1.5 mm. When using spraying, the air pressure should be 0.2 MPa to 0.4 MPa, and the nozzle diameter 1 mm to 2 mm; alternatively, brushing can be used. The ambient temperature should be controlled between 20℃ and 30℃, and the relative humidity between 40% and 60%. For example, during spraying, a spray gun with an air pressure of 0.2 MPa to 0.4 MPa and a nozzle diameter of 1 mm to 2 mm can be used to ensure the uniformity of the coating.

[0039] S50: Place the coated crucible in a drying oven and dry for 2-4 hours. The drying process is divided into two stages: the first stage is drying at 50℃-80℃ for 1-2 hours, and the second stage is heating to 100℃-150℃ and maintaining that temperature for 1-2 hours. A hot air circulating drying box with a temperature control system can be selected to achieve precise temperature control. The segmented drying method can effectively reduce the internal stress of the coating and avoid cracking. This segmented drying process, combined with the thermal stability of rare earth oxides, lays a good precursor structure foundation for the rare earth elements to fully exert their modifying effect in the subsequent sintering stage.

[0040] S60: The dried sagger is placed in a high-temperature furnace and sintered at 1300℃~1400℃ for 3 h~6 h (under air atmosphere). After cooling, the coated sagger is obtained. In this embodiment, the sintering process is divided into three stages: the first stage is to heat from room temperature to 600℃~800℃ at a heating rate of 5℃ / min~10℃ / min; the second stage is to heat from 600℃~800℃ to 1300℃~1400℃ at a heating rate of 3℃ / min~5℃ / min; and the third stage is to hold at 1300℃~1400℃ for 3 h~6 h. Segmented sintering can promote the orderly growth of grains inside the coating and reduce the influence of thermal stress on the coating. In this invention, the sagger substrate is preferably made of mullite-cordierite material, which has a coefficient of thermal expansion of (4~6)×10. -6 The coating is compatible with the temperature range of / ℃. Cooling is performed at a natural cooling rate or slowly at a rate of ≤5℃ / min to room temperature under an inert atmosphere to reduce thermal stress. This segmented sintering strategy, combined with the addition of rare earth oxides, forms an effective synergy: suitable heating rates and holding stages provide the kinetics for the segregation of rare earth oxides at grain boundaries and the formation of low-expansion stable phases, while the rare earth oxides amplify the positive effects of segmented sintering by inhibiting anomalous grain growth and promoting densification, together achieving a unified coating with low porosity, high bonding strength, and excellent thermal stability.

[0041] The present invention will be further described below with reference to embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments. Unless otherwise specified, the sagger substrate used in the following embodiments and comparative examples is made of mullite-cordierite. The coating performance testing method is as follows:

[0042] Corrosion depth test: The coated crucible is placed in a crucible containing a mixture of Li2CO3 and Co3O4 powder (mass ratio 1:1), kept at 850℃ in air atmosphere for 12 hours, and after cooling, the maximum corrosion penetration depth is measured along the cross section.

[0043] Thermal shock cycling test: The coated sample is held at 1100℃ for 15 minutes, then quickly removed and rapidly cooled in room temperature water for 3 minutes. This constitutes one cycle. Repeat this process until obvious cracks or peeling appear in the coating, and record the number of cycles.

[0044] Bond strength test: The tensile bond strength test (GB / T 8642-2002) was used.

[0045] Hardness test: Vickers hardness tester, load 1 kgf, holding pressure for 15 s.

[0046] Porosity testing: Archimedes' drainage method was used.

[0047] Thermal expansion coefficient test: Measured using a thermal expansion meter, with a test temperature range from room temperature to 1000℃.

[0048] Long-term cyclic corrosion test: Repeated corrosion depth test method, performing 50 and 100 cycles, recording the corrosion depth after each cycle to evaluate the long-term stability of the coating.

[0049] Synergistic effect test: Design different experimental groups, including complete technical solution (example), adding only rare earth oxides but not using segmented process, using only segmented process but not adding rare earth oxides, and existing technology coating, and compare their key performance indicators.

[0050] Anti-adhesion performance test: The cathode material (such as LiCoO2) and the coating sample were co-sintered at 850℃ for 12 hours. After cooling, the mass of cathode material adhering to the coating surface was weighed, and the ease of cleaning was evaluated (expressed as the percentage of residue after light brushing).

[0051] Example 1

[0052] The coatings were prepared according to S10 to S60, wherein the mass ratio of the base powder was 6:3:2:1, the cerium oxide content was 2%, and the modulus of the water glass solution in the slurry was 3 with a mass fraction of 35%. The drying process consisted of two stages: a first stage at 60℃ for 1.5 h, and a second stage at 120℃ for 2 h. The sintering process (in air atmosphere) involved a first stage at 700℃ and a second stage at 1300℃, with a holding time of 4 h.

[0053] Example 2

[0054] The coatings were prepared according to S10 to S60, wherein the mass ratio of the base powder was 5:4:1:2, the cerium oxide addition was 1%, and the modulus of the water glass solution in the slurry was 2.5, with a mass fraction of 30%. The drying process consisted of a first stage at 50℃ for 2 hours and a second stage at 100℃ for 1 hour. The sintering process (in air atmosphere) involved a first stage at 600℃ and a second stage at 1300℃, with a holding time of 3 hours.

[0055] Example 3

[0056] The coatings were prepared according to S10 to S60, wherein the mass ratio of the base powder was 7:2:3:1, the cerium oxide content was 3%, and the modulus of the water glass solution in the slurry was 3.5, with a mass fraction of 40%. The drying process consisted of two stages: a first stage at 80℃ for 1 hour, and a second stage at 150℃ for 2 hours. The sintering process (in air atmosphere) involved a first stage at 800℃ and a second stage at 1400℃, with a holding time of 6 hours. The sintering atmosphere was air.

[0057] Example 4

[0058] The coatings were prepared according to S10 to S60, wherein the mass ratio of the base powder was 6:2:1:1, the cerium oxide addition was 2.5%, and the water glass solution in the slurry had a modulus of 3 and a mass fraction of 35%. The drying process consisted of two stages: a first stage at 70℃ for 1.5 h, and a second stage at 130℃ for 1.5 h. The sintering process (in air atmosphere) involved a first stage at 750℃ and a second stage at 1350℃, with a holding time of 5 h.

[0059] Example 5

[0060] The coatings were prepared according to S10 to S60, wherein the mass ratio of the base powder was 5:3:2:2, the cerium oxide addition was 1.5%, and the modulus of the water glass solution in the slurry was 3, with a mass fraction of 35%. The drying process consisted of two stages: a first stage at 65℃ for 2 hours, and a second stage at 110℃ for 2 hours. The sintering process (in air atmosphere) involved a first stage at 650℃ and a second stage at 1350℃, with a holding time of 4 hours.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that no cerium oxide was added to the coating prepared in Comparative Example 1, and the segmented drying and sintering process was not used (i.e., one-time drying was used, directly drying at 120°C for 3 hours; direct sintering was used, directly heating from room temperature to 1300°C at a rate of 5°C / min and holding for 4 hours), while the other conditions were the same as in Example 1.

[0063] Comparative Example 2

[0064] The difference from Example 3 is that the coating prepared in Comparative Example 2 does not use the segmented drying and segmented sintering process (i.e., it uses one-time drying: directly drying at 120°C for 3 h; and direct sintering: directly heating from room temperature to 1300°C at 5°C / min and holding for 4 h), while the other conditions are the same as in Example 3.

[0065] Comparative Example 3

[0066] The difference from Example 1 is that no cerium oxide was added to the coating prepared in Comparative Example 3, while the other conditions were the same as in Example 1.

[0067] Comparative Example 4

[0068] The difference from Example 1 is that the coating prepared in Comparative Example 4 does not use the segmented drying and segmented sintering process (i.e., one-time drying: direct drying at 120°C for 3 hours; direct sintering: direct heating from room temperature to 1300°C at a rate of 5°C / min and holding for 4 hours), while the other conditions are the same as in Example 1.

[0069] The relevant experimental comparisons and conclusions between the above embodiments and comparative examples are as follows:

[0070] Table 1. Coating corrosion depth test results of Examples 1 to 5 and Comparative Examples 1 to 4

[0071]

[0072] Conclusion: The corrosion resistance of the example (using the complete scheme) is superior to all comparative examples. Comparative Example 3 (using only a segmented process) and Comparative Example 4 (adding only rare earth elements) showed limited performance improvement, far inferior to Example 1. Among all examples, Example 3 (high rare earth element addition) exhibited the best corrosion resistance.

[0073] Table 2. Results of thermal shock cycle tests on coatings in Examples 1 to 5 and Comparative Examples 1 to 4

[0074]

[0075] Conclusion: The thermal shock resistance of the examples exceeds that of the comparative examples. Notably, among all examples, Example 3 exhibited the highest number of thermal shock cycles, while Example 1 showed superior bonding strength (see Table 3), reflecting the different performance emphases of the formulations. The significant performance improvements in Examples 1 and 3 are primarily attributed to the combined effect of rare earth oxides and the segmented process, resulting in excellent interfacial bonding and low thermal stress characteristics.

[0076] Table 3. Coating bond strength test results of Examples 1 to 5 and Comparative Examples 1 to 4

[0077]

[0078] Conclusion: The bonding strength of the example was the highest. The bonding strength of Comparative Example 4 (rare earth only) was higher than that of Comparative Example 3 (segmented process only), indicating that rare earth oxides have a positive effect on improving interfacial bonding. When combined with the segmented sintering process (Example 1), the bonding strength was further improved, and the improvement was even greater.

[0079] Table 4. Coating hardness test results of Examples 1 to 5 and Comparative Examples 1 to 4

[0080]

[0081] Conclusion: The hardness of the examples was significantly higher than that of the comparative examples, indicating that the examples exhibited a high degree of densification. Hardness and porosity (Table 5) showed a clear negative correlation.

[0082] Table 5. Coating porosity test results of Examples 1 to 5 and Comparative Examples 1 to 4

[0083]

[0084] Conclusion: The porosity of the examples was significantly lower than that of the comparative examples. Low porosity is fundamental to corrosion resistance and mechanical strength. The porosity of Comparative Example 4 (rare earth only) was lower than that of Comparative Example 3 (segmented process only), but both were much higher than that of Example 1, indicating that the synergistic effect is crucial for achieving extreme densification.

[0085] Table 6. Test results of the coefficient of thermal expansion of the coatings in Examples 1 to 5 and Comparative Examples 1 to 4

[0086]

[0087] Analysis: The coefficient of thermal expansion of the embodiment is closer to that of the crucible substrate, resulting in better compatibility. This helps reduce thermal stress and improve thermal shock resistance. It is evident that the present invention optimizes the phase composition and microstructure of the coating, thereby achieving excellent thermal expansion characteristics.

[0088] As can be seen from Tables 1-6, the coatings of the embodiments are superior to those of the comparative examples in terms of corrosion resistance, thermal shock resistance, bonding strength, hardness, porosity, and coefficient of thermal expansion. In particular, by comparing Example 1 with Comparative Example 3 (without rare earth elements, but with segmented processing) and Comparative Example 4 (with rare earth elements, but without segmented processing), it can be seen that while using the segmented process alone (Comparative Example 3) or adding rare earth oxides alone (Comparative Example 4) can bring some performance improvement, their effects are lower than those of Example 1. This indicates that the introduction of rare earth oxides interacts significantly with the segmented drying and sintering processes, greatly improving the overall performance of the coating. Example 3, in particular, demonstrates outstanding performance in corrosion resistance and thermal shock resistance, while Example 1 is superior in bonding strength, providing a preferred solution for different application scenarios.

[0089] Table 7. Long-term cyclic corrosion test results of Examples 1 to 5 and Comparative Examples 1 to 4

[0090]

[0091] Analysis: The corrosion depth of the examples increased after long-term cycling, but the rate of increase varied depending on the formulation. Example 3 exhibited the best long-term stability. The comparative examples showed a significant increase in corrosion depth, indicating that the coating of the present invention, especially the optimized formulation, possesses excellent long-term stability.

[0092] Table 8. Test results of bond strength and thermal shock cycle count

[0093]

[0094] Analysis: The improvement in bonding strength and thermal shock cycle count of Example 1 exceeded that of Comparative Example 3 and Comparative Example 4, indicating a significant improvement in both bonding strength and thermal shock cycle count.

[0095] Table 9. Test results of anti-adhesion properties of Examples 1 to 5 and Comparative Examples 1 to 4

[0096]

[0097] Analysis: The adhesion amount and residue after cleaning in the examples were significantly lower than those in the comparative example, indicating that the coating of the present invention has excellent anti-adhesion properties, is easy to clean and maintain, and reduces the risk of cathode material contamination. Among all examples, Example 3 also exhibited the best anti-adhesion properties.

[0098] As shown in Tables 7-9, the coating of this invention exhibits excellent stability in long-term cyclic corrosion tests (Table 7). Combined with the strength and thermal shock cycle test results, it demonstrates an excellent synergistic effect (Table 8), and its anti-adhesion performance is significantly improved (Table 9). This indicates that this invention effectively solves the problems of insufficient long-term stability and easy contamination of coatings in existing technologies.

[0099] In summary, this invention provides a reliable basis and reference for improving the overall performance of lithium battery crucible coatings.

[0100] The above embodiments are merely preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but which still solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium battery crucible coating, characterized in that, Includes the following steps: S10: Alumina, zirconium oxide, magnesium oxide and silicon oxide are mixed in a mass ratio of 5-7:2-4:1-3:1-2 to obtain a basic powder; S20: Add 1% to 3% of cerium oxide with a purity ≥ 99.5% by mass to the base powder and form a uniformly mixed powder by ball milling; the cerium oxide is used to promote grain densification and optimize the thermal expansion behavior of the lithium battery crucible coating during subsequent sintering. S30: Mix the uniformly mixed powder with the water glass solution at a mass ratio of 10 to 15:1, and stir evenly to form a slurry; S40: Apply the slurry to the surface of the sagger, with the coating thickness controlled between 0.5mm and 1.5mm; S50: Place the coated crucible in a drying oven for drying. The drying process is divided into two stages. The first stage is drying at 50℃~80℃ for 1h~2h. The second stage is heating up to 100℃~150℃ and maintaining it for 1h~2h. S60: The dried sagger is sintered in an air atmosphere, and then cooled to obtain the coated sagger. The sintering process is divided into three stages: the first stage is to heat from room temperature to 600℃~800℃ at a heating rate of 5℃ / min~10℃ / min; the second stage is to heat from 600℃~800℃ to 1300℃~1400℃ at a heating rate of 3℃ / min~5℃ / min; the third stage is to hold at 1300℃~1400℃ for 3h~6h to obtain the lithium battery sagger coating.

2. The method for preparing the lithium battery crucible coating according to claim 1, characterized in that, In S10, the particle size distribution range of the base powder is 1μm to 5μm.

3. The method for preparing the lithium battery crucible coating according to claim 2, characterized in that, In S10, the mass ratio of aluminum oxide, zirconium oxide, magnesium oxide and silicon oxide is 6:3:2:

1.

4. The method for preparing the lithium battery crucible coating according to claim 2, characterized in that, In S10, the mass ratio of aluminum oxide, zirconium oxide, magnesium oxide and silicon oxide is 7:2:3:

1.

5. The method for preparing the lithium battery crucible coating according to claim 2, characterized in that, In S10, the mass ratio of aluminum oxide, zirconium oxide, magnesium oxide and silicon oxide is 6:2:1:

1.

6. The method for preparing the lithium battery crucible coating according to any one of claims 1 to 5, characterized in that, In step S20, the ball milling time is 4h to 8h, the ball milling medium is zirconia balls, the ball-to-material mass ratio is 5 to 10:1, and the ball milling speed is 200r / min to 400r / min.

7. The method for preparing the lithium battery crucible coating according to claim 6, characterized in that, In S30, the modulus of the water glass solution is 2.5 to 3.5, and the mass fraction is 30% to 40%.

8. The method for preparing the lithium battery crucible coating according to claim 7, characterized in that, In S40, the coating method is spraying or brushing, and the coating environment temperature is controlled at 20℃~30℃ and the relative humidity is 40%~60%.

9. A lithium battery crucible coating, characterized in that, The coating is prepared by the method according to any one of claims 1 to 8.

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