A composite structure crucible for lithium battery cathode materials and its preparation method

Abstract

This invention relates to the field of sagger kiln furniture manufacturing technology, and proposes a composite structure sagger for lithium battery cathode materials and its preparation method. The aforementioned composite structure sagger for lithium battery cathode materials includes a substrate layer, an intermediate layer, and a surface coating. The preparation method of the composite structure sagger for lithium battery cathode materials includes steps such as preparing a substrate layer green body, preparing the intermediate layer and surface coating, and high-temperature sintering. The composite structure sagger for lithium battery cathode materials prepared by this method has good corrosion resistance, a high number of cycles, a long service life, and does not peel, shed slag, or cause pollution during use. It is suitable for the sintering process of various lithium battery cathode materials, which helps to reduce production costs and improve economic efficiency.

Description

Technical Field

[0001] This invention relates to the field of sagger kiln furniture preparation technology, and in particular to a composite structure sagger for lithium battery cathode materials and its preparation method. Background Technology

[0002] Saggers are one of the essential kiln tools for firing lithium-ion battery cathode materials. All types of lithium-ion battery cathode materials must first be placed in saggers before being placed into a high-temperature kiln for firing. Currently, domestically produced saggers still lag significantly behind their foreign counterparts in terms of cycle life, corrosion resistance, thermal shock stability, and material compressive strength. The annual cost of replacing saggers is substantial, and this also causes significant environmental damage.

[0003] The existing double-layer structure saggers, after a certain number of uses, show changes in the physical and chemical properties of the coating and the substrate on the sagger surface, causing the sagger surface to begin to peel off. This not only affects product quality but also easily leads to safety accidents.

[0004] Therefore, to meet the ever-increasing demand for lithium-ion battery cathode materials, it is essential to develop a crucible with excellent corrosion resistance, high reusability, long lifespan, and the ability to prevent scaling, slagging, and pollution during use. This crucible should be suitable for the sintering process of various lithium-ion battery cathode materials, thereby reducing production costs and improving economic efficiency. Developing a crucible for lithium-ion battery cathode materials that approximates or possesses these superior properties is of significant importance and industrial value. Summary of the Invention

[0005] The purpose of this invention is to provide a composite structure crucible for lithium battery cathode materials. The crucible has good corrosion resistance, does not peel, shed slag, or cause pollution during use, and is suitable for the sintering process of various lithium battery cathode materials. Most importantly, it has an extremely long service life and can be reused far more times than similar products currently on the market.

[0006] Another objective of this invention is to provide a method for preparing a composite structure crucible for lithium-ion battery cathode materials. The crucible prepared by the above method exhibits excellent corrosion resistance and can effectively resist corrosion in high-temperature environments. + It resists erosion and does not peel or crumble during repeated cycles of high-temperature sintering and cooling.

[0007] The technical problem solved by this invention is achieved by the following technical solution.

[0008] This invention proposes a composite structure crucible for lithium battery cathode materials, which includes a substrate layer, an intermediate layer and a surface coating.

[0009] The raw materials of the matrix layer, by weight, include the following components: 50-70 parts of high-purity silicon nitride powder, 10-20 parts of tabular corundum, 5-15 parts of magnesium aluminum spinel, 5-15 parts of clay, 4-6 parts of pulp waste liquor, and 5-10 parts of high-temperature resistant inorganic binder.

[0010] The intermediate layer raw material is polysilazane, which is an organic-inorganic hybrid polymer with Si-N as the main chain. It can be bonded to the substrate in the form of covalent bonds and has excellent adhesion to most substrates. In addition, it has rich and excellent physical and chemical properties such as high strength, high heat resistance, high modulus, and high density. It is an excellent coating material that can be used to prepare a dense high-temperature resistant and anti-corrosion coating, which plays a good protective role for the sagger substrate.

[0011] The raw material for the surface coating is a silane coupling agent, which is an organosilicon compound that undergoes thermal decomposition under high temperature conditions. The resulting siloxane is a compound in which silicon atoms and oxygen atoms are connected by covalent bonds. It combines with the surface of the sagger to form a stable organosilicon film with excellent shear resistance, heat resistance and chemical corrosion resistance, which can effectively enhance the surface performance of the sagger.

[0012] A method for preparing a composite structure crucible for lithium battery cathode materials includes the following steps:

[0013] Preparation of matrix layer structure green body: Under ultrasonic conditions, 10-20 parts of pulverized tabular corundum, 5-15 parts of magnesium aluminum spinel, 5-15 parts of clay and 4-6 parts of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 50-70 parts of high-purity silicon nitride powder and 5-10 parts of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 40-60 minutes and aging for 12-18 hours, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0014] Drying and high-temperature sintering: After drying the above-mentioned sagger matrix layer structure green body, it is sintered at 1250-1350℃ for 3-5 hours to obtain the sagger matrix;

[0015] Preparation of the intermediate layer: Polysilazane and aromatic solvent are mixed to form a solvent with a mass fraction of 4%-8%, and the above-mentioned sagger substrate is thoroughly brushed with this solvent, dried, and then cooled to room temperature after a heating and drying step. The mixed solvent is then brushed onto the sagger green body, heated to 170-190°C, and held at this temperature for at least 15 minutes. After cooling, the green body is heated to 700-800°C and held at this temperature for 15-25 minutes before cooling to room temperature, so that the intermediate layer is formed on the surface of the sagger substrate.

[0016] Preparation of surface coating: Prepare a 0.9-1.1% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 120~180℃ for 2~5 h to obtain a composite structure crucible for lithium battery cathode materials.

[0017] The beneficial effects of the composite structure crucible for lithium battery cathode materials and its preparation method according to embodiments of the present invention are as follows:

[0018] (1) A double-layer protective coating is designed, using polysilazane as the intermediate layer. It has excellent adhesion to most substrates and also possesses excellent physicochemical properties such as high strength, high heat resistance, high modulus, and high density. It can be used to prepare a dense, high-temperature resistant, and corrosion-resistant coating, which provides good protection for the crucible substrate. At the same time, the intermediate layer is prepared by multiple programmed heating and cooling processes, which effectively ensures the protective effect of the coating.

[0019] (2) The stable organosilicon film generated by the thermal decomposition of silane coupling agent is used as a surface coating. It has excellent shear resistance, heat resistance and chemical corrosion resistance, which can effectively enhance the surface performance of the sagger.

[0020] (3) The prepared sagger products have good corrosion resistance and long service life. During use, the sagger does not peel, shed slag, or cause pollution. It can be reused far more times than similar products on the market. It is suitable for the sintering process of various lithium battery cathode materials, which helps to reduce production costs and improve economic benefits. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The application of lithium-ion batteries is becoming increasingly widespread. Due to the highly reactive chemical properties of lithium metal, its charging and discharging capabilities are superior to those of traditional batteries, making lithium-ion batteries the mainstream in the battery manufacturing field. Saggers are one of the important kiln tools for firing lithium battery cathode materials; all types of lithium battery cathode materials must first be placed in saggers before being placed into a high-temperature kiln for firing.

[0023] Si3N4 material has excellent physical and chemical properties, characterized by high strength and high temperature resistance. It also exhibits excellent thermal shock resistance, wear resistance, oxidation resistance, and acid and alkali corrosion resistance. Even in high-temperature environments above 1000℃, it will not crack after rapid cooling and then rapid heating, demonstrating extremely strong resistance to thermal shock.

[0024] Tabular corundum is a pure sintered corundum that has undergone complete shrinkage during firing without any additives such as MgO. It has a coarse-grained, well-developed α-Al2O3 crystal structure with an Al2O3 content of over 99%. It possesses characteristics such as high refractoriness, high corrosion resistance, high erosion resistance, high thermal shock resistance, high strength, good toughness, and stable chemical properties.

[0025] Magnesium aluminum spinel belongs to the cubic crystal system. Kiln furniture containing magnesium aluminum spinel has high resistance to erosion.

[0026] Polysilazanes are a class of inorganic polymers with Si-N as the main chain. Due to the special nature of their chemical structure, they can be transformed into SiCN, SiCNO or silicon dioxide ceramics under high temperature conditions. Therefore, silazane polymers have important application value in high-temperature resistant coatings.

[0027] Silane coupling agents are a class of organosilicon compounds that contain both organic groups and silicon-oxygen bonds in their molecules. They can act as bridges between organic and inorganic materials, improve the performance and bonding strength of composite materials, and can be used for surface modification to effectively improve the surface resistance of materials.

[0028] The following is a detailed description of a composite structure crucible for lithium battery cathode materials and its preparation method according to an embodiment of the present invention.

[0029] A composite structure crucible for lithium battery cathode materials, comprising a matrix layer, an intermediate layer, and a surface coating.

[0030] The raw materials of the matrix layer, by weight, include the following components: 50-70 parts of high-purity silicon nitride powder, 10-20 parts of tabular corundum, 5-15 parts of magnesium aluminum spinel, 5-15 parts of clay, 4-6 parts of pulp waste liquor, and 5-10 parts of high-temperature resistant inorganic binder.

[0031] Furthermore, the high-purity silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, and the magnesium aluminum spinel has a particle size of 2 mm.

[0032] Furthermore, the clay is Suzhou white clay;

[0033] The intermediate layer raw material is polysilazane, which is an organic-inorganic hybrid polymer with Si-N as the main chain. It can be bonded to the substrate in the form of covalent bonds and has excellent adhesion to most substrates. In addition, it has rich and excellent physical and chemical properties such as high strength, high heat resistance, high modulus, and high density. It is an excellent coating material that can be used to prepare a dense high-temperature resistant and anti-corrosion coating, which plays a good protective role for the sagger substrate.

[0034] The raw material for the surface coating is a silane coupling agent, which is an organosilicon compound that undergoes thermal decomposition under high temperature conditions. The resulting siloxane is a compound in which silicon atoms and oxygen atoms are connected by covalent bonds. It combines with the surface of the crucible to form a stable organosilicon film with excellent shear resistance, heat resistance and chemical corrosion resistance.

[0035] Furthermore, the silane coupling agent is vinyltriisopropoxysilane.

[0036] A method for preparing a composite structure crucible for lithium battery cathode materials includes the following steps:

[0037] Preparation of matrix layer structure green body: Under ultrasonic conditions, 10-20 parts of pulverized tabular corundum, 5-15 parts of magnesium aluminum spinel, 5-15 parts of clay and 4-6 parts of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 50-70 parts of high-purity silicon nitride powder and 5-10 parts of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 40-60 minutes and aging for 12-18 hours, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0038] Furthermore, the ultrasonic intensity is 0.5~1.2 W / cm. 2 Ultrasonic treatment can make the materials mix more evenly, increase the contact surface area between materials, make it easier to compact during the molding process, and make the resulting sagger matrix structure more compact, with stronger thermal shock stability and erosion resistance.

[0039] Drying and high-temperature sintering: After drying the above-mentioned sagger matrix layer structure green body, it is sintered at 1250-1350℃ for 3-5 hours to obtain the sagger matrix;

[0040] Preparation of the intermediate layer: Polysilazane and aromatic solvent are mixed to form a solvent with a mass fraction of 4%-8%, and the above-mentioned sagger substrate is thoroughly brushed with this solvent, dried, and then cooled to room temperature after a heating and drying step. The mixed solvent is then brushed onto the sagger green body, heated to 170-190°C, and held at this temperature for at least 15 minutes. After cooling, the green body is heated to 700-800°C and held at this temperature for 15-25 minutes before cooling to room temperature, so that the intermediate layer is formed on the surface of the sagger substrate.

[0041] Furthermore, the heating and drying step in the preparation of the intermediate layer involves drying at 100°C for 5 minutes, heating to 150°C at a rate of 10°C / min, and holding at 150°C for 20-30 minutes.

[0042] Preparation of surface coating: Prepare a 0.9-1.1% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 120~180℃ for 2~5 h to obtain a composite structure crucible for lithium battery cathode materials.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments. Example 1

[0044] This embodiment proposes a composite structure crucible for lithium battery cathode materials, which includes a substrate layer, an intermediate layer, and a surface coating.

[0045] The matrix layer raw materials include the following components: 60kg of high-purity silicon nitride powder, 15kg of tabular corundum, 10kg of magnesium aluminum spinel, 10kg of clay, 5kg of pulp waste liquor, and 7.5kg of high-temperature resistant inorganic binder.

[0046] Among them, the silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, the magnesium aluminum spinel has a particle size of 2 mm, and the clay is Suzhou white clay.

[0047] The intermediate layer raw material is polysilazane;

[0048] The raw material for the surface coating is a silane coupling agent, specifically vinyltriisopropoxysilane.

[0049] This embodiment also proposes a method for preparing a composite structure crucible for lithium battery cathode materials, including the following steps:

[0050] Preparation of matrix layer structure green body: at 0.8 W / cm 2 Under ultrasonic conditions, 15 kg of pulverized tabular corundum with a particle size of 0.5-2 mm, 10 kg of magnesium aluminum spinel with a particle size of 2 mm, 10 kg of Suzhou white clay, and 5 kg of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 60 kg of high-purity silicon nitride powder with a particle size of 0.1-0.5 mm and 7.5 kg of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 50 min and aging for 16 h, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0051] Drying and high-temperature sintering: The above-mentioned sagger matrix layer structure green body is dried and then sintered at 1300℃ for 4 hours to obtain the sagger matrix;

[0052] Preparation of intermediate layer: Polysilazane and aromatic solvent are mixed to form a 6% by mass solvent. The above-mentioned sagger substrate is thoroughly brushed with this solvent and dried. It is dried at 100°C for 5 min, heated to 150°C at a rate of 10°C / min, and held at 150°C for 25 min. After cooling to room temperature, the mixed solvent is brushed on the sagger green body, heated to 180°C, and held at this temperature for 20 min. After cooling, the green body is heated to 750°C and held at this temperature for 20 min before cooling to room temperature, so that an intermediate coating is formed on the surface of the sagger substrate.

[0053] Preparation of surface coating: Prepare a 1% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 150°C for 3 h to obtain a composite structure crucible for lithium battery cathode materials. Example 2

[0054] This embodiment proposes a composite structure crucible for lithium battery cathode materials, which includes a substrate layer, an intermediate layer, and a surface coating.

[0055] The matrix layer raw materials include the following components: 50kg of high-purity silicon nitride powder, 20kg of tabular corundum, 5kg of magnesium aluminum spinel, 15kg of clay, 4kg of pulp waste liquor, and 10kg of high-temperature resistant inorganic binder.

[0056] Among them, the silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, the magnesium aluminum spinel has a particle size of 2 mm, and the clay is Suzhou white clay.

[0057] The intermediate layer raw material is polysilazane;

[0058] The raw material for the surface coating is a silane coupling agent, specifically vinyltriisopropoxysilane.

[0059] This embodiment also proposes a method for preparing a composite structure crucible for lithium battery cathode materials, including the following steps:

[0060] Preparation of matrix layer structure green body: at 0.5 W / cm 2 Under ultrasonic conditions, 20 kg of pulverized tabular corundum with a particle size of 0.5-2 mm, 5 kg of magnesium aluminum spinel with a particle size of 2 mm, 15 kg of Suzhou white clay, and 4 kg of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 50 kg of high-purity silicon nitride powder with a particle size of 0.1-0.5 mm and 10 kg of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 60 min and aging for 12 h, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0061] Drying and high-temperature sintering: The above-mentioned sagger matrix layer structure green body is dried and then sintered at 1350℃ for 3 hours to obtain the sagger matrix;

[0062] Preparation of intermediate layer: Polysilazane and aromatic solvent are mixed to form a 4% by mass solvent. The above-mentioned sagger substrate is thoroughly brushed with this solvent and dried. It is dried at 100°C for 5 min, heated to 150°C at a rate of 10°C / min, and held at 150°C for 25 min. After cooling to room temperature, the mixed solvent is brushed on the sagger green body, heated to 170°C, and held at this temperature for 25 min. After cooling, the green body is heated to 800°C and held at this temperature for 15 min before cooling to room temperature, so that an intermediate coating is formed on the surface of the sagger substrate.

[0063] Preparation of surface coating: Prepare a 1.1% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 120℃ for 5 h to obtain a composite structure crucible for lithium battery cathode material. Example 3

[0064] This embodiment proposes a composite structure crucible for lithium battery cathode materials, which includes a substrate layer, an intermediate layer, and a surface coating.

[0065] The matrix layer raw materials include the following components: 70kg of high-purity silicon nitride powder, 10kg of tabular corundum, 15kg of magnesium aluminum spinel, 5kg of clay, 6kg of pulp waste liquor, and 5kg of high-temperature resistant inorganic binder.

[0066] Among them, the silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, the magnesium aluminum spinel has a particle size of 2 mm, and the clay is Suzhou white clay.

[0067] The intermediate layer raw material is polysilazane;

[0068] The raw material for the surface coating is a silane coupling agent, specifically vinyltriisopropoxysilane.

[0069] This embodiment also proposes a method for preparing a composite structure crucible for lithium battery cathode materials, including the following steps:

[0070] Preparation of matrix layer structure green body: at 1.2 W / cm 2Under ultrasonic conditions, 10 kg of pulverized tabular corundum with a particle size of 0.5-2 mm, 15 kg of magnesium aluminum spinel with a particle size of 2 mm, 5 kg of Suzhou white clay, and 6 kg of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 70 kg of high-purity silicon nitride powder with a particle size of 0.1-0.5 mm and 5 kg of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 40 min and aging for 18 h, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0071] Drying and high-temperature sintering: The above-mentioned sagger matrix layer structure green body is dried and then sintered at 1250℃ for 5h to obtain the sagger matrix;

[0072] Preparation of intermediate layer: Polysilazane and aromatic solvent are mixed to form a solvent with a mass fraction of 8%. The above-mentioned sagger substrate is thoroughly brushed with this solvent and dried. It is dried at 100°C for 5 min, heated to 150°C at a rate of 10°C / min, and held at 150°C for 25 min. After cooling to room temperature, the mixed solvent is brushed on the sagger green body, heated to 190°C, and held at this temperature for 30 min. After cooling, the green body is heated to 700°C and held at this temperature for 25 min before cooling to room temperature, so that an intermediate coating is formed on the surface of the sagger substrate.

[0073] Preparation of surface coating: Prepare a 0.9% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 180°C for 2 h to obtain a composite structure crucible for lithium battery cathode materials. Example 4

[0074] This embodiment proposes a composite structure crucible for lithium battery cathode materials, which includes a substrate layer, an intermediate layer, and a surface coating.

[0075] The matrix layer raw materials include the following components: 60kg of high-purity silicon nitride powder, 15kg of tabular corundum, 10kg of magnesium aluminum spinel, 10kg of clay, 5kg of pulp waste liquor, and 7.5kg of high-temperature resistant inorganic binder.

[0076] Among them, the silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, the magnesium aluminum spinel has a particle size of 2 mm, and the clay is Guangxi white clay.

[0077] The intermediate layer raw material is polysilazane;

[0078] The raw material for the surface coating is a silane coupling agent, specifically vinyltrimethoxysilane.

[0079] This embodiment also proposes a method for preparing a composite structure crucible for lithium battery cathode materials, including the following steps:

[0080] Preparation of matrix layer structure green body: at 0.8 W / cm 2 Under ultrasonic conditions, 15 kg of pulverized tabular corundum with a particle size of 0.5-2 mm, 10 kg of magnesium aluminum spinel with a particle size of 2 mm, 10 kg of Suzhou white clay, and 5 kg of pulp waste liquor are uniformly mixed until the surface of the dry granules is wetted. After obtaining the mixed aggregate, 60 kg of high-purity silicon nitride powder with a particle size of 0.1-0.5 mm and 7.5 kg of high-temperature resistant inorganic binder are added to the mixed aggregate. After mixing for 50 min and aging for 16 h, the sagger matrix layer structure green body is made by slip casting or extrusion molding.

[0081] Drying and high-temperature sintering: The above-mentioned sagger matrix layer structure green body is dried and then sintered at 1300℃ for 4 hours to obtain the sagger matrix;

[0082] Preparation of intermediate layer: Polysilazane and aromatic solvent are mixed to form a 6% by mass solvent. The above-mentioned sagger substrate is thoroughly brushed with this solvent and dried. It is dried at 100°C for 5 min, heated to 150°C at a rate of 10°C / min, and held at 150°C for 25 min. After cooling to room temperature, the mixed solvent is brushed on the sagger green body, heated to 180°C, and held at this temperature for 20 min. After cooling, the green body is heated to 750°C and held at this temperature for 20 min before cooling to room temperature, so that an intermediate coating is formed on the surface of the sagger substrate.

[0083] Preparation of surface coating: Prepare a 1% silane coupling agent ethanol aqueous solution with an ethanol to water ratio of 8:2, spray it evenly on the surface of the above-mentioned crucible, and dry it at 150°C for 3 h to obtain a composite structure crucible for lithium battery cathode materials.

[0084] Comparative Example 1

[0085] Compared with Example 1, the main difference is that the composite structure crucible for the lithium battery cathode material in Comparative Example 1 does not have a surface coating.

[0086] This comparative example also proposes a method for preparing a crucible for lithium battery cathode materials. The main difference between this method and Example 1 is that Comparative Example 1 does not include a surface coating preparation step.

[0087] Comparative Example 2

[0088] Compared with Example 1, the main difference is that the composite structure crucible for the lithium battery cathode material in Comparative Example 1 does not have an intermediate layer;

[0089] This comparative example also proposes a method for preparing a crucible for lithium battery cathode materials. The main difference between this method and Example 1 is that Comparative Example 1 does not include the step of preparing an intermediate layer.

[0090] Test case

[0091] The service life performance of the saggers prepared in Examples 1-4 and Comparative Examples 1-2 were tested respectively. They were used to calcine and synthesize 333 (in the order of nickel, cobalt, and manganese) nickel-cobalt-manganese lithium-ion battery ternary materials. The service life of each sagger was determined by the occurrence of sagger breakage, resulting in partial detachment and damage. The surface condition of the sagger was also observed after 25 uses. The test results are shown in Table 1.

[0092] Table 1. Performance test results of the saggers prepared in Examples 1-4 and Comparative Examples 1-2

[0093]

[0094] After long-term use, the saggers produced by this invention have no problems such as peeling, flaking, or contamination of the firing materials, and their service life can reach more than 55 times (ternary material 333), far exceeding the traditional saggers on the market.

[0095] The experimental results show that, using the raw materials and methods provided by this invention, employing high-temperature resistant Si3N4 as the base material, designing polysilazane as the intermediate layer, and using a stable organosilicon film generated by the thermal decomposition of silane coupling agents as the surface coating, the resulting crucible has a significantly higher reuse count than the commonly used ones in the industry. The crucible of this invention exhibits excellent high-temperature corrosion resistance during use, and there is no surface peeling even after repeated use, significantly improving product quality and stability, reducing production costs, and increasing enterprise production efficiency.

[0096] In summary, the composite structure crucible for lithium battery cathode materials and its preparation method of this invention significantly enhance the corrosion resistance of the crucible substrate by using high-temperature resistant Si3N4 material in the substrate layer. The addition of ultrasonic mixing during material mixing results in more uniform material mixing and a denser substrate structure. Simultaneously, a double-layer protective coating is designed, using polysilazane as the intermediate layer. Polysilazane exhibits excellent adhesion to most substrates and possesses superior physicochemical properties such as high strength, high heat resistance, high modulus, and high density, enabling the preparation of a dense, high-temperature resistant, and corrosion-resistant coating that effectively protects the crucible substrate. A stable organosilicon film generated by the thermal decomposition of a silane coupling agent serves as the surface coating, exhibiting excellent shear resistance, heat resistance, and chemical corrosion resistance, effectively enhancing the surface performance of the crucible. Furthermore, the use of multiple programmed heating and cooling processes during the preparation of the intermediate layer effectively ensures the protective effect of the coating. This significantly extends the service life of the crucible, improves its structural strength and corrosion resistance, effectively enhances product quality and stability, and contributes to increased production efficiency for enterprises.

[0097] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A composite structure saggar for a lithium battery cathode material, characterized by, It comprises a base layer, an intermediate layer and a surface coating layer; The base layer raw material comprises the following components in parts by weight: 50-70 parts of high-purity silicon nitride powder, 10-20 parts of tabular corundum, 5-15 parts of magnesium aluminate spinel, 5-15 parts of clay, 4-6 parts of paper pulp waste liquid, 5-10 parts of high-temperature-resistant inorganic binder; The intermediate layer raw material is polysilazane; The surface coating layer raw material is silane coupling agent.

2. The composite structure sagger for a lithium battery cathode material according to claim 1, characterized in that, The high-purity silicon nitride powder has a particle size of 0.1-0.5 mm, the tabular corundum has a particle size of 0.5-2 mm, and the magnesium aluminate spinel has a particle size of 2 mm.

3. The composite structure box for a lithium battery cathode material according to claim 1, characterized in that, The clay is Suzhou white clay.

4. The composite structure box for a lithium battery cathode material according to claim 1, characterized in that, The silane coupling agent is vinyl triisopropenoxy silane.

5. A method of manufacturing a composite structure saggar for a lithium battery cathode material as claimed in any one of claims 1 to 4, characterized in that, It comprises: Preparation of the green body of the matrix layer structure: under ultrasonic condition, the intensity of the ultrasonic condition is 0.5-1.2 W / cm 2 After the mixed aggregate is prepared by uniformly mixing 10-20 parts of crushed tabular corundum, 5-15 parts of magnesium aluminate spinel, 5-15 parts of clay and 4-6 parts of paper pulp waste liquid until the surface of the dry granular material is wet, 50-70 parts of high-purity silicon nitride powder and 5-10 parts of high-temperature-resistant inorganic binder are added to the mixed aggregate, mixed for 40-60 min and aged for 12-18 h, and then a green body of the matrix layer structure of the saggar is prepared by using the slip casting method or the extrusion molding method. Drying and high-temperature sintering: after drying the above-mentioned anvil base layer structure green body, sintering at 1250-1350℃ for 3-5h to obtain an anvil base; Preparation of the intermediate layer: polysilazane is prepared into a mixed solvent with a mass fraction of 4%-8% with an aromatic hydrocarbon solvent, and the above-mentioned anvil base is fully brushed with the solvent and dried, then after the step of heating and drying, it is cooled to room temperature, and then the mixed solvent is brushed on the anvil green body, heated to 170~190℃, and kept at this temperature for at least 15 min, then cooled and heated to 700~800℃, and kept at this temperature for 15~25 min, then cooled to room temperature, so as to form the intermediate layer on the surface of the anvil base; Preparation of the surface coating layer: 0.9-1.1% silane coupling agent ethanol aqueous solution is prepared, the ratio of ethanol and water is 8:2, which is uniformly sprayed on the surface of the above-mentioned anvil, and dried at 120~180℃ for 2~5 h to obtain a composite structure anvil for lithium battery positive electrode material.

6. The method of claim 5, wherein the method further comprises: coating the graphite with a coating material to form a coated graphite; and coating the coated graphite with a coating material to form a coated graphite. The step of heating and drying is to dry at 100℃ for 5 min, then heat to 150℃ at a rate of 10℃ / min, and keep at 150℃ for 20-30 min.

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