Composite saggar, method of manufacture and use

Abstract

The present application relates to a kind of material field, and a kind of composite saggar, preparation method and application.The raw material of the composite saggar includes: spinel, petalite, sodium zirconium phosphate, 10% polyvinyl alcohol solution, water and coating.The saggar provided in the present application: spinel is the mineral of magnesium alumina oxide composition, has the advantages such as erosion resistance, abrasion resistance and thermal shock stability.In the saggar, petalite and sodium zirconium phosphate are introduced, the low-temperature sintering of spinel material is realized, and the sintering strength is high, and thermal shock performance is good;By sol-gel process, a layer of zirconium oxide coating is formed on the surface of saggar, the alkali corrosion resistance of saggar can be greatly improved, and the service life is improved.The saggar provided in the present application has high strength, and the breakage rate of mechanical automatic operation during use is low.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a composite crucible, its preparation method, and its applications. Background Technology

[0002] Lithium-ion batteries generally consist of three parts: a positive electrode material, a negative electrode material, and an electrolyte solution. The positive electrode materials of lithium-ion batteries mainly include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), and lithium iron phosphate (LiFePO4).

[0003] Lithium-ion battery cathode materials are mostly prepared by high-temperature solid-phase synthesis in a kiln using refractory saggers.

[0004] However, saggars ( Figure 1 Ordinary saggers, after repeated cold and hot use, are mostly scrapped after no more than 20 uses, generally around 15. There are two reasons for this: first, the saggers are cyclically used in high-temperature kilns; second, the cathode material corrodes and peels off the saggers at high temperatures. In actual production, the short service life of saggers is often due to the combined effect of these two factors.

[0005] In order to improve the lifespan of the sagger, the inventors consulted a large number of documents and found that the zirconium oxide coating could improve the corrosion resistance of the sagger.

[0006] Zirconia sol possesses excellent properties such as high temperature resistance, corrosion resistance, wear resistance, and oxidation resistance, and is widely used in industries such as ceramics (http: / / www.forsman.com.cn / wap / rongjiao / 1126.html).

[0007] Most manufacturers use a 4mm thick zirconia plate (zirconia does not react with ferrite soft magnets) or a layer of zirconia sand evenly sprinkled inside the sagger to isolate the product from contact with the mullite sagger (e.g.) Figure 2 (As shown).

[0008] There are also reports of adding other components to zirconium oxide coatings, such as:

[0009] To enhance the properties of zirconium oxide by adding individual components: LiAlO2 (CN109956760A); Yttrium oxide (CN113501724B);

[0010] Combinations of fused zirconia with different particle sizes and other components: 4-6 parts of 60-mesh fused zirconia, 1-4 parts of 100-mesh fused zirconia, 1-3 parts of 200-mesh fused zirconia, 0.1-0.5 parts of sodium hexametaphosphate, 0.1-0.5 parts of polyvinyl alcohol, and 1-5 parts of water (CN106431423A) (polyvinyl alcohol dissolves very slowly during use at room temperature and cannot play a binding role, resulting in weak adhesion. Therefore, the product in this literature cannot be molded).

[0011] Multiple stabilizers are added: 80-mesh yttrium oxide stabilized zirconia powder, 150-mesh calcium oxide stabilized zirconia powder, 150-mesh yttrium oxide stabilized zirconia powder, and 325-mesh yttrium oxide stabilized zirconia powder (CN109279878A).

[0012] The inventors coated the inner surface of the sagger with zirconium oxide, which nearly doubled the product's lifespan. In one experiment, they unexpectedly discovered that adding sodium zirconium phosphate to the sagger material could further extend the sagger's lifespan.

[0013] Furthermore, the inventors discovered that the sagger absorbs a large amount of lithium oxide during use, causing changes in the material composition and thus affecting product performance. Therefore, it is best to avoid absorbing lithium oxide. Analysis reveals two main reasons for the sagger's absorption of lithium oxide during use: first, the sagger has a high porosity, reaching up to 30%, allowing it to hold a large amount of lithium oxide; second, it reacts with the sagger material to form lithium-containing compounds, causing volume expansion and ultimately damaging the sagger. Summary of the Invention

[0014] In order to improve the service life of existing saggers and reduce lithium adsorption in saggers, this application provides a composite sagger.

[0015] In the first aspect, the composite sagger provided in this application comprises the following raw materials: spinel, petalite, sodium zirconium phosphate, 10% polyvinyl alcohol solution, water, and coating.

[0016] Specifically, the raw materials for the composite sagger include the following components by weight: 55-60 parts spinel, 15-30 parts petalite, 10-30 parts sodium zirconium phosphate, 20-40 parts 10% polyvinyl alcohol solution, 80-120 parts water, and 10-17 parts coating.

[0017] Preferably, the raw materials of the composite sagger include the following components in parts by weight: 55-57 parts spinel, 15-28 parts petalite, 15-30 parts sodium zirconium phosphate, 20-35 parts 10% polyvinyl alcohol solution, 80-120 parts water, and 11.5-17 parts coating.

[0018] Further preferably, the raw materials of the composite sagger include the following components in parts by weight: 55 parts spinel, 20-25 parts petalite, 20-25 parts sodium zirconium phosphate, 25-30 parts 10% polyvinyl alcohol solution, 90-100 parts water, and 12-15 parts coating.

[0019] In the sagger:

[0020] The spinel contains 71-76% Al2O3, 22-27% MgO, and the total Al2O3+MgO content is greater than 98%.

[0021] The spinel is specifically sintered spinel or fused spinel, preferably fused spinel; the spinel powder has a particle size of 325 mesh.

[0022] The sodium zirconium phosphate content is ≥95%, and the particle size is 325 mesh.

[0023] The petalite described has the chemical composition Li[AlSi4O] 10 The lithium oxide content is greater than 4%, the Li2O content is not less than 4.0%, and the particle size is 325 mesh.

[0024] The 10% polyvinyl alcohol solution contains 10 parts polyvinyl alcohol and 90 parts water.

[0025] (Note: The above-mentioned limits on raw material particle size are for ease of operation during the preparation process.)

[0026] The coating contains zirconium oxide sol.

[0027] 10% polyvinyl alcohol was also added to the coating.

[0028] Each coating consists of zirconium oxide sol and 10% polyvinyl alcohol solution in a weight ratio of 100:5 to 8.

[0029] Before coating, the zirconia sol is mixed with a 10% polyvinyl alcohol solution. The inventors had previously attempted to coat the zirconia sol alone, but the release oil on the mold would stick to the sagger surface, making it difficult for the zirconia sol to adhere, resulting in separation of the coating from the sagger. After adding the polyvinyl alcohol solution, the oil burns off during sintering, allowing the coating and sagger material to bond tightly together.

[0030] Secondly, this application provides a method for preparing a composite sagger, comprising the following steps:

[0031] 1) Ball milling powder: spinel powder, lithium feldspar, sodium zirconium phosphate, 10% polyvinyl alcohol solution and water are ground for 24-36 hours, and then spray granulated to obtain granulated powder for later use.

[0032] 2) Press the spray-granulated powder into shape and let it stand on the kiln car for 12-24 hours;

[0033] 3) Coat the bottom of the sagger with a uniform layer of zirconium oxide sol containing polyvinyl alcohol, let it air dry naturally, and the gel will solidify into a gel.

[0034] 4) The drying time of the zirconium oxide sol applied in step 3);

[0035] 5) Place the dried saggar into the kiln and sinter it to obtain the product.

[0036] In the above methods:

[0037] Step 3) The coating method can be any conventional method. It can be sprayed onto the surface or a measured amount of coating can be poured into a crucible and spread out. It is better to pour a measured amount of coating into the crucible and then spread it out, as the amount is easier to control.

[0038] In step 4), the drying temperature is 50-60℃ and the drying time is 24-72 hours;

[0039] The sintering method in step 5) is to first sinter at a temperature of 1310-1410℃, hold for 3-5 hours, and then cool down with the furnace.

[0040] Thirdly, the composite crucible provided by this invention is mainly used in lithium battery cathode materials such as 811, 622, and 523 series.

[0041] In summary, this application has the following beneficial effects:

[0042] 1. The sagger provided in this application:

[0043] 1) Spinel is a mineral composed of magnesium aluminum oxide, possessing advantages such as resistance to erosion, abrasion, and thermal shock resistance. Introducing petalite and sodium zirconium phosphate into the crucible enables low-temperature sintering of spinel materials, resulting in high sintering strength and good thermal shock resistance.

[0044] 2) A zirconium oxide coating is generated on the surface of the sagger through a sol-gel process, which can greatly improve the sagger's resistance to alkali corrosion and extend its service life.

[0045] 2. The sagger provided by this invention has high strength and a low breakage rate during mechanized automatic operation. Attached Figure Description

[0046] Figure 1 A schematic diagram of a standard saggar;

[0047] Figure 2 : A schematic diagram of adding a coating to a sagger;

[0048] Figure 3 : A schematic diagram of the structure of this application. Detailed Implementation

[0049] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0050] (I) Composition of the composite sagger

[0051] Examples 1-5 and Comparative Examples 1-3: See Table 1

[0052] Table 1: Composition of Examples 1-5 and Comparative Examples 1-3 (unit: g or kg)

[0053]

[0054] Note: A 10% polyvinyl alcohol solution is 10g of polyvinyl alcohol dissolved in 90g of water.

[0055] (II) Preparation method of composite sagger:

[0056] 1) Ball milling powder: Add spinel powder, petalite, sodium zirconium phosphate, 10% polyvinyl alcohol solution and water to a ball mill and grind for 24-36 hours. Spray granulation is then performed to obtain granulated powder for later use.

[0057] 2) Pour the sagger material into the sagger mold, press it into shape, place it on the kiln car, and let it stand on the kiln car for 12 to 24 hours to allow it to air dry and release stress.

[0058] 3) First, add 10% polyvinyl alcohol solution to the zirconium oxide sol, then coat the bottom of the air-dried crucible with a uniform layer of zirconium oxide sol (see...). Figure 3 After air drying for 48 hours, the sol solidifies into a gel.

[0059] 4) Place the crucible coated with zirconium oxide sol into a drying room to dry for 48 to 72 hours at a temperature of 50 to 60°C.

[0060] 5) Place the dried saggers into the kiln, sinter at 1310-1410℃, hold for 3-5 hours, and then slowly cool down.

[0061] Comparative Example 4: Composite Sagger

[0062] The composition and preparation method are the same as in Example 3, except that 10% polyvinyl alcohol solution is added to the zirconia sol (4 parts of 10% polyvinyl alcohol solution are added to 100 parts of zirconia sol).

[0063] Experimental Example 1: Quality Assessment of Composite Saggers

[0064] 1. Samples, see Examples 1-5 and Comparative Examples 1-4.

[0065] 2. Data evaluation indicators:

[0066] 2.1 The testing methods for density, flexural strength, and porosity are shown in Table 2.

[0067] Table 2: Detection Indicators and Detection Methods

[0068] detection indicators unit Detection methods Standard value density <![CDATA[g / cm 3 ]]> GB / T30873-2014 2.7～3.0 Flexural strength MPa GB / T2997-2015 ≥60 Porosity ％ GB / T2997-2015 ≤3.0

[0069] 2.2 Service Life: Samples are prepared according to the configuration. Qualified samples are sent to the factory for trial use in the furnace. The cathode material manufacturer will test the appearance, dimensions, and physicochemical indicators according to the company's internal quality requirements to confirm that the product will not have an adverse impact on its production. Then, it is arranged for use in the production line. Generally, one sintering cycle is about 24 hours. After one sintering is completed, the sagger is tested for cracking or peeling. If there are no problems, it continues to be used until the product cracks or peels and is scrapped. The service life of each sagger is calculated. Based on the number of samples in each sagger, the average number of uses is obtained as the service life of the sagger for each formula.

[0070] 2.3 Lithium content detection: The lithium oxide content in the initial cathode material precursor is detected, and then the lithium oxide content in the sintered cathode material is detected. The difference is the lithium adsorption difference. The lithium adsorption amount is calculated as lithium adsorption difference / 29.88 (lithium oxide molecular weight) * 73.89 (lithium carbonate molecular weight).

[0071] 3. Experimental results: See Table 3

[0072] Table 4: Results of each evaluation indicator

[0073]

[0074]

[0075] The results show:

[0076] 1) The lithium absorption capacity, porosity, and service life of Examples 1 to 5 are better than those of Comparative Examples 1 and 2.

[0077] 2) Comparative Example 3 could not be molded. Polyvinyl alcohol is mainly used as a binder. Since there is no polyvinyl alcohol, there is no bonding force between the powders. It can be molded during the pressing process, but the bonding force is very poor and it cannot be demolded. It will break as soon as it is demolded.

[0078] Comparative Example 4: The entire material of the sagger is the same as that of Example 3, with a coating of 6 parts. Its service life was reduced from 125 times to 76 times. The coating used was less, and some areas were too thin, which would not cover the entire bottom. The exposed bottom areas were prone to corrosion and damage.

[0079] Therefore, there is no relevant data for comparative examples 3 and 4.

[0080] The above results indicate that the ceramic composite sagger has a longer service life and a lower lithium adsorption capacity.

[0081] The explanation is that the lithium content loss is related to the porosity of the crucible and the number of uses. In actual use, the amount of lithium absorbed will decrease, and generally, it will stop absorbing lithium after 10 uses. Taking our existing crucible with a porosity of 25.4 as an example, its size is 330mm*330mm*120mm. The production company's statistics show that the lithium absorbed in the first use is 151g, which requires an additional 151g in the positive electrode material to ensure the quality of the positive electrode material. However, the maximum lithium absorption of the crucible in this application is 16g, which is significantly reduced and saves production costs for enterprises.

[0082] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A composite sagger, characterized in that, The raw materials of the composite sagger include the following components by weight: 55-60 parts spinel, 15-30 parts petalite, 10-30 parts sodium zirconium phosphate, 20-40 parts 10% polyvinyl alcohol solution, 80-120 parts water, and 10-17 parts coating. Each part of the coating is composed of zirconium oxide sol and 10% polyvinyl alcohol solution in a weight ratio of 100:5-8.

2. The composite sagger according to claim 1, characterized in that, The raw materials of the composite sagger include the following components by weight: 55-57 parts spinel, 15-28 parts petalite, 15-30 parts sodium zirconium phosphate, 20-35 parts 10% polyvinyl alcohol solution, 80-120 parts water, and 11.5-17 parts coating.

3. The composite sagger according to claim 2, characterized in that, The raw materials of the composite sagger include the following components by weight: 55 parts spinel, 20-25 parts petalite, 20-25 parts sodium zirconium phosphate, 25-30 parts 10% polyvinyl alcohol solution, 90-100 parts water, and 12-15 parts coating.

4. The composite sagger according to claim 1, characterized in that, The spinel is sintered spinel or electrofused spinel.

5. The composite sagger according to claim 4, characterized in that, The spinel is an electrofused spinel.

6. The composite sagger according to claim 1, characterized in that, The petalite described has the chemical composition Li[AlSi4O] 10 [The lithium oxide content is greater than 4%.] 7. The method for preparing the composite sagger according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Ball milling powder: spinel powder, lepidolite, sodium zirconium phosphate, 10% polyvinyl alcohol solution and water are ground for 24-36 hours, then spray granulated to obtain granulated powder for later use. 2) Press the spray-granulated powder into shape and let it stand on the kiln car for 12-24 hours; 3) Coat the bottom of the sagger with a uniform layer of zirconium oxide sol containing polyvinyl alcohol, let it air dry naturally, and the gel will solidify into a gel. 4) Dry the crucible coated with zirconium oxide sol in step 3); 5) Place the dried saggar into the kiln and sinter it to obtain the product.

8. The composite crucible according to any one of claims 1 to 6 is applied to the 811, 622, and 523 series of lithium battery cathode materials.

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