A regenerated sagger based on waste sagger recycling material and its preparation method and application

Abstract

The present invention discloses a regenerated sagger based on recycled materials from waste saggers, and a preparation method and application thereof. The specific steps of the preparation method are as follows: S1. Mixing recycled materials from waste saggers, third-grade high-alumina bauxite, charcoal, ferroaluminum spinel and clay to obtain a premix; S2. Adding phosphoric acid solution to the premix and stirring to obtain a mixture; S3. Sealing the mixture, placing it in a mold, and machine pressing to obtain a sagger green body; S4. Heat-treating the sagger green body to obtain a regenerated sagger based on recycled materials from waste saggers; the recycled materials from waste saggers are oxide saggers that are scrapped after calcining lithium iron phosphate positive electrode materials. The method of the present invention has a simple process, low cost, energy conservation and environmental protection, and the prepared saggers have high density, high strength, strong corrosion resistance and permeability resistance, and high thermal shock stability.

Description

Technical Field

[0001] The present invention relates to the technical field of saggers, and in particular to a regenerated sagger based on recycled materials from waste saggers, and a preparation method and application thereof. Background Art

[0002] New energy batteries such as lithium batteries have developed rapidly. In the high-temperature solid-phase preparation process, the calcination of positive electrode materials for new energy batteries requires a large amount of saggers, which generates a large amount of industrial solid waste.

[0003] Unlike other industrial solid waste, waste saggers are not simply stored or buried. This is because, on the one hand, they contain a large number of high-value components (such as lithium, cobalt, nickel, manganese and other high-value components) that can be recycled; on the other hand, they may contain toxic components that pollute environmental health. In addition, positive electrode material manufacturers will also perform surface treatment on waste saggers based on technical confidentiality requirements to prevent the leakage of key positive electrode material technology secrets due to the discard of waste saggers. At present, most positive electrode material manufacturers use "surface separation" technology to make the positive electrode materials adhered to the waste saggers fall off, and then the waste saggers are processed.

[0004] Among the many cathode materials, lithium iron phosphate (LiFePO4, abbreviated as LFP) is one of the earliest and most widely studied cathode materials for lithium-ion batteries. Although its voltage platform is low and its energy density is also low, its raw material sources are wide ( Zhang Chi , Zheng Lei, Shen Weiyun, et al. Research progress of lithium iron phosphate cathode material[J]. Metallurgy and Materials, 2023, 43(8): 31-33 ), low price (Fe and P are both readily available), safe, and free of toxic components (such as cobalt). Therefore, lithium iron phosphate combines these advantages and shares a market share of nearly 50% with LNCM ternary cathodes in commercial lithium-ion batteries. According to data released by the Ministry of Industry and Information Technology, the annual production of LFP in China exceeded 1.2 million tons in 2022. Therefore, the large amount of saggers used for LFP cathode calcination faces recycling and environmental issues.

[0005] Unlike other cathode materials, on the one hand, LFP cathode does not contain toxic components such as cobalt, so the environmental risk faced by the recycling of LFP cathode sintering saggers is relatively small; on the other hand, LFP cathode materials have no obvious rejection of iron elements. This is because Fe itself is a component of LFP, and lithium cobalt oxide or LNCM cathodes have strict control over the iron content. Therefore, after the LFP cathode calcination saggers are scrapped, the use of them is limited due to the residual risk of FeO in the waste saggers. There are reports that the waste saggers after calcining LFP cathode materials are used to prepare permeable bricks ( Sun Guoliang, Shi Jijun, Shao Zhuang, et al. Using waste boxes Research on the production of porous water-permeable bricks with earthenware[J]. China Ceramic Industry, 2006, 13(3): 1-4 ), clay bricks( A waste box Method for preparing low-porosity clay bricks from potting material, CN200810049833.1 ), or to replace alumina powder to prepare refractory materials ( Liu Pengcheng, Zhang Wei, Qian Fan. Effect of waste sagger powder addition on the properties of cordierite-mullite refractory materials[J]. Materials, 2021, 55(4): 319-321 The related work provides a good research basis for the recycling of waste saggers after calcination of LFP positive electrode materials, but there is no detailed report on the use of recycled materials from waste saggers to re-prepare saggers for LFP positive electrode sintering. Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to propose a regenerated sagger based on recycled materials from waste saggers, as well as a preparation method and application thereof. The method is simple in process, low in cost, energy-saving and environmentally friendly, and the prepared sagger has high density, high strength, strong corrosion and permeability resistance, and high thermal shock stability.

[0007] The present invention provides a method for preparing a regenerated sagger based on recycled materials from waste saggers, and the specific steps are as follows:

[0008] S1. The waste sagger recycled material, three-grade high-alumina bauxite, coke gem, iron aluminum spinel and clay are mixed to obtain a premix;

[0009] S2. A phosphoric acid solution was added to the premix, and stirred to obtain a mixture;

[0010] S3. The mixture is sealed and trapped, placed in a mold, and pressed to obtain a green sagger;

[0011] S4. The sagger green body is heat treated to obtain a regenerated sagger based on the waste sagger recycled material;

[0012] The waste sagger recycled material is the oxide sagger that is scrapped after the lithium iron phosphate positive electrode material is calcined.

[0013] Furthermore, the mass ratio of the waste sagger recycled material: third-grade high-alumina bauxite: charcoal: ferroaluminum spinel: clay is 100: (60-65): (12-20): (10-15): (8-12).

[0014] Furthermore, the concentration of the phosphoric acid solution is 12-16 wt%.

[0015] Furthermore, the phosphoric acid solution accounts for 6.2 to 7.5 wt % of the premix.

[0016] Furthermore, in step S3, the mixture is sealed and trapped at 25-30° C. for 6-8 hours, then placed in a mold and subjected to machine pressing at a pressure of 50-60 MPa to obtain a sagger green body.

[0017] Furthermore, in step S4, heat treatment is performed at 550-800° C. for 4-6 hours.

[0018] Furthermore, the (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

[0019] Furthermore, the particle size of the third-grade high-alumina bauxite is 0.1 to 1.0 mm; and\or,

[0020] The particle size of the coke gemstone is 1 to 2 mm; and\or,

[0021] The particle size of the iron-aluminum spinel is 55 to 60 μm; and\or,

[0022] The particle size of the clay is 40 to 50 μm.

[0023] A regenerated sagger based on recycled materials from waste saggers is prepared by the above-mentioned preparation method.

[0024] A regenerated sagger based on recycled waste sagger as described above is used for calcining lithium iron phosphate positive electrode materials.

[0025] Recycled saggers can be used as raw materials for the calcination of lithium iron phosphate cathode materials. The reasons are: (1) LFP cathode materials have lower service requirements for saggers. Graphite saggers (high cost) or oxide saggers can be used for LFP cathode sintering. This is because the atmosphere for LFP cathode sintering is a reducing atmosphere rather than air or an oxidizing atmosphere, which is completely different from the sintering of lithium cobalt oxide or LNCM ternary cathodes. In addition, due to the influence of many processes such as spraying, granulation and coating of LFP precursors, the contact form between LFP cathode materials and saggers is changed. Therefore, the erosion damage of LFP cathode to saggers is relatively small, and the service and performance requirements are also reduced accordingly, which facilitates the incorporation and use of recycled waste saggers.

[0026] (2) The alkalinity of LFP cathode material is relatively low. In the precursor of LFP cathode material, due to the strong acidic group [PO4 3- The presence of significantly reduces the alkalinity of the LFP positive electrode material, thereby further reducing the erosion of the LFP positive electrode material on the sagger, which is one of the reasons why the recycled materials from the waste sagger can be recycled.

[0027] The beneficial effects of the present invention are:

[0028] (1) The waste sagger recycled material has the basis for preparing the regenerated sagger. The present invention uses the waste sagger recycled material as the main raw material, and combines it with cheap raw materials such as third-grade high-alumina bauxite and coke gemstone, which greatly reduces the development cost of the regenerated sagger, expands the application path of the waste sagger recycled material, realizes the circular comprehensive utilization of the waste sagger recycled material, is environmentally friendly, does not produce toxic components, and has good social and economic benefits.

[0029] (2) After high-temperature sintering and repeated high-temperature service, the saggers used for LFP positive electrode calcination have fully grown and stable performance. At the same time, since the recycled materials of waste saggers absorb iron and lithium components, the recycled saggers prepared with the recycled materials of waste saggers as the main raw material will not only not affect the service performance of the saggers, but will also increase the alkalinity of the saggers and enhance the corrosion resistance of the saggers.

[0030] (3) The present invention uses phosphoric acid solution as a binder, which has a wide source and low cost. Phosphoric acid reacts with the aluminum and iron components in the raw material components (such as third-grade high-alumina bauxite, coke gemstone, and waste sagger recycling materials) to form a phosphate chemical bond, thereby improving the bonding strength of the regenerated sagger, thereby improving the density of the regenerated sagger. In addition, the phosphoric acid bond does not introduce other impurities or salt components, and increases the concentration of phosphorus-containing components in the regenerated sagger matrix, which is beneficial for resisting the erosion and diffusion of lithium iron phosphate.

[0031] (4) The present invention improves the corrosion resistance of the regenerated sagger by introducing ferroaluminum spinel, utilizes the larger lattice voids of the FeO-Al2O3 solid solution in the reducing atmosphere during the service of the sagger, absorbs the lithium-containing components, improves the corrosion resistance of the regenerated sagger, and extends the service life of the sagger.

[0032] (5) The present invention does not require high-temperature firing. Instead, the softening filling is formed by the phosphate ceramic phase produced by low-temperature heat treatment (550-800°C), and the network microcrystals produced by the pyrolysis of clay (such as Guangxi mud, Suzhou soil, etc.) are combined to effectively absorb the thermal stress during the sagger's cyclic service process, thereby improving the sagger's thermal shock resistance.

[0033] (6) The process of the present invention is simple. It does not require special raw materials and processing methods. Instead, it uses low-quality refractory raw materials as the main raw materials, fully utilizes the glassy state formed by impurity components (Fe2O3, Na2O, etc.) to improve sintering and bonding, and from the perspective of reducing the concentration difference between the lithium iron phosphate positive electrode material and the components of the regeneration sagger body, it synergistically resists the penetration and diffusion of lithium iron phosphate.

[0034] The regenerated saggers prepared by the present invention based on the recycled materials of waste saggers are tested:

[0035] The apparent porosity is 12-14%; the compressive strength is 44-52 MPa; the residual flexural strength retention rate after three thermal shock stability tests at 1100°C with circulating water cooling is 92.7-94.4%; the erosion index of the static crucible method slag resistance test at 1100°C×10h is 2.2-3.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a SEM image of the microstructure of the regenerated sagger based on the waste sagger recycled material prepared in Example 1. DETAILED DESCRIPTION

[0037] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0038] Example 1

[0039] The present embodiment provides a method for preparing a regenerated sagger based on recycled materials from waste saggers, and the specific steps are as follows:

[0040] 1) Add the waste sagger recycled material: third-grade high-alumina bauxite: pyrope stone: ferroaluminum spinel: clay in a mass ratio of 100:60:20:15:8 to a roller mixer and mix for 15-20 minutes to obtain a premix;

[0041] 2) adding a phosphoric acid solution accounting for 7.5 wt % of the premix to the premix, stirring for 10 to 12 minutes to obtain a mixture; the concentration of the phosphoric acid solution is 12 wt %;

[0042] 3) After sealing the mixture at 25-30° C. for 6-8 hours, the mixture is placed in a mold and pressed at a pressure of 50-60 MPa to obtain a sagger green body;

[0043] 4) The sagger green body is placed under heat treatment at 800° C. for 4 hours and cooled to room temperature to obtain a recycled sagger based on the waste sagger recycled material.

[0044] The waste sagger recycled material is the oxide sagger discarded after the lithium iron phosphate positive electrode material is calcined; the (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

[0045] The particle size of third-grade high-alumina bauxite is 0.1-1.0 mm.

[0046] The particle size of the coke gemstone is 1 to 2 mm.

[0047] The particle size of the iron-aluminum spinel is 55 to 60 μm.

[0048] The clay is Guangxi mud.

[0049] The particle size of clay is 40 to 50 μm.

[0050] Figure 1 This is an SEM image of the microstructure of the recycled sagger based on the waste sagger prepared in Example 1. It can be seen that the components of the recycled sagger are evenly dispersed, the particles are well bonded to the matrix, and there is no cracking or peeling; the matrix is tightly filled and wrapped, with no through holes or cracks.

[0051] The regenerated saggers based on the waste saggers recycled materials prepared in this embodiment were tested:

[0052] The apparent porosity is 12%; the compressive strength is 51 MPa; the residual flexural strength retention rate after three thermal shock stability tests at 1100℃ circulating water cooling is 92.9%, and the erosion index of the static crucible method slag resistance test at 1100℃×10h is 3.4%.

[0053] Example 2

[0054] The present embodiment provides a method for preparing a regenerated sagger based on recycled materials from waste saggers, and the specific steps are as follows:

[0055] 1) Add the waste sagger recycled material: third-grade high-alumina bauxite: pyrope stone: ferroaluminum spinel: clay in a mass ratio of 100:65:12:10:12 to the material in a roller mixer and mix for 15-20 minutes to obtain a premix;

[0056] 2) adding a phosphoric acid solution accounting for 6.2 wt % of the premix to the premix, stirring for 10 to 12 minutes to obtain a mixture; the concentration of the phosphoric acid solution is 16 wt %;

[0057] 3) After sealing the mixture at 25-30° C. for 6-8 hours, the mixture is placed in a mold and pressed at a pressure of 50-60 MPa to obtain a sagger green body;

[0058] 4) heat-treating the sagger green body at 550° C. for 6 hours and cooling it to room temperature to obtain a recycled sagger based on the waste sagger recycled material.

[0059] The waste sagger recycled material is the oxide sagger discarded after the lithium iron phosphate positive electrode material is calcined; the (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

[0060] The particle size of third-grade high-alumina bauxite is 0.1-1.0 mm.

[0061] The particle size of the coke gemstone is 1 to 2 mm.

[0062] The particle size of the iron-aluminum spinel is 55 to 60 μm.

[0063] The clay is Guangxi mud.

[0064] The particle size of clay is 40 to 50 μm.

[0065] The regenerated saggers based on the waste saggers recycled materials prepared in this embodiment were tested:

[0066] The apparent porosity is 14%; the compressive strength is 44 MPa; the residual flexural strength retention rate after three thermal shock stability tests at 1100℃ circulating water cooling is 94.4%, and the erosion index of the static crucible method slag resistance test at 1100℃×10h is 3.5%.

[0067] Example 3

[0068] The present embodiment provides a method for preparing a regenerated sagger based on recycled materials from waste saggers, and the specific steps are as follows:

[0069] 1) Add the waste sagger recycled material: third-grade high-alumina bauxite: pyrope stone: ferroaluminum spinel: clay in a mass ratio of 100:63:17:13:9 to the material in a roller mixer and mix for 15-20 minutes to obtain a premix;

[0070] 2) adding a phosphoric acid solution accounting for 6.6 wt % of the premix to the premix, stirring for 10 to 12 minutes to obtain a mixture; the concentration of the phosphoric acid solution is 15 wt %;

[0071] 3) After sealing the mixture at 25-30° C. for 6-8 hours, the mixture is placed in a mold and pressed at a pressure of 50-60 MPa to obtain a sagger green body;

[0072] 4) The sagger green body is subjected to heat treatment at 600° C. for 5 hours and then cooled to room temperature to obtain a recycled sagger based on the waste sagger recycled material.

[0073] The waste sagger recycled material is the oxide sagger discarded after the lithium iron phosphate positive electrode material is calcined; the (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

[0074] The particle size of third-grade high-alumina bauxite is 0.1-1.0 mm.

[0075] The particle size of the coke gemstone is 1 to 2 mm.

[0076] The particle size of the iron-aluminum spinel is 55 to 60 μm.

[0077] The clay is Suzhou soil.

[0078] The particle size of clay is 40 to 50 μm.

[0079] The regenerated saggers based on the waste saggers recycled materials prepared in this embodiment were tested:

[0080] The apparent porosity is 13%; the compressive strength is 52 MPa; the residual flexural strength retention rate after three thermal shock stability tests at 1100℃ circulating water cooling is 93.8%, and the erosion index of the static crucible method slag resistance test at 1100℃×10h is 2.2%.

[0081] Comparative Example 1

[0082] The preparation method of a regenerated sagger based on the recycled material of waste sagger in this comparative example comprises the following specific steps:

[0083] 1) Add the waste sagger recycled material: third-grade high-alumina bauxite: charcoal: clay in a mass ratio of 100:65:12:12 to a roller mixer and mix for 15 to 20 minutes to obtain a premix;

[0084] 2) adding a phosphoric acid solution accounting for 6.2 wt % of the premix to the premix, stirring for 10 to 12 minutes to obtain a mixture; the concentration of the phosphoric acid solution is 16 wt %;

[0085] 3) After sealing the mixture at 25-30° C. for 6-8 hours, the mixture is placed in a mold and pressed at a pressure of 50-60 MPa to obtain a sagger green body;

[0086] 4) heat-treating the sagger green body at 550° C. for 6 hours and cooling it to room temperature to obtain a recycled sagger based on the waste sagger recycled material.

[0087] The waste sagger recycled material is the oxide sagger discarded after the lithium iron phosphate positive electrode material is calcined; the (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

[0088] The particle size of third-grade high-alumina bauxite is 0.1-1.0 mm.

[0089] The particle size of the coke gemstone is 1 to 2 mm.

[0090] The clay is Guangxi mud.

[0091] The particle size of clay is 40 to 50 μm.

[0092] The regenerated saggers based on the waste saggers recycled materials prepared in this comparative example were tested:

[0093] The apparent porosity is 23%; the compressive strength is 22 MPa; the residual flexural strength retention rate after three thermal shock stability tests at 1100℃ circulating water cooling is 84.5%, and the erosion index of the static crucible method slag resistance test at 1100℃×10h is 7.6%.

[0094] Compared with Example 2, it can be seen that the regenerated sagger prepared without adding the ferroaluminum spinel component cannot effectively absorb the lithium-containing component due to the loss of the solid solution effect of the spinel, thereby reducing the corrosion resistance of the regenerated sagger; at the same time, the chemical reaction combination of ferroaluminum spinel and phosphoric acid disappears synchronously, resulting in the weakening of the mechanical strength and thermal shock resistance of the regenerated sagger.

[0095] Any matters not mentioned above shall be subject to the existing technology.

[0096] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a regenerated sagger based on recycled materials from waste saggers, characterized in that: The specific steps are as follows: S1. The waste sagger recycled material, three-grade high-alumina bauxite, coke gem, iron aluminum spinel and clay are mixed to obtain a premix; S2. A phosphoric acid solution was added to the premix, and stirred to obtain a mixture; S3. The mixture is sealed and trapped, placed in a mold, and pressed to obtain a green sagger; S4. The green sagger is heat treated to obtain a regenerated sagger based on recycled material from waste sagger; The waste sagger recycled material is the oxide sagger discarded after the lithium iron phosphate positive electrode material is calcined; Recycled materials from scrap saggers: third-grade high-alumina bauxite: pyroxene: ferroaluminum spinel: clay in a mass ratio of 100: (60-65): (12-20): (10-15): (8-12); The concentration of the phosphoric acid solution is 12-16 wt %; In step S4, heat treatment is performed at 550-800° C. for 4-6 hours; The (Al2O3+SiO2+FeO) content of the waste sagger recycled material is ≥90wt%; and the particle size of the waste sagger recycled material is 60-80μm.

2. The method for preparing a regenerated sagger based on recycled materials from waste saggers according to claim 1, characterized in that: The phosphoric acid solution accounts for 6.2-7.5 wt % of the premix.

3. The method for preparing a regenerated sagger based on recycled materials from waste saggers according to claim 1, characterized in that: In step S3, the mixed material is sealed and trapped at 25-30° C. for 6-8 hours, then placed in a mold and subjected to machine pressing at a pressure of 50-60 MPa to obtain a sagger green body.

4. The method for preparing a regenerated sagger based on recycled materials from waste saggers according to any one of claims 1 to 3, characterized in that: The particle size of the third-grade high-alumina bauxite is 0.1-1.0 mm; and\or, The particle size of the coke gemstone is 1-2 mm; and\or, The particle size of the iron-aluminum spinel is 55-60 μm; and\or, The clay is one of Guangxi clay and Suzhou clay; The particle size of the clay is 40-50 μm.

5. A regenerated sagger based on recycled materials from waste saggers, prepared by the preparation method according to any one of claims 1 to 4.

6. A regenerated sagger based on recycled waste sagger as claimed in claim 5 is used for calcining lithium iron phosphate positive electrode materials.

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