A sintering process, sintering system apparatus, target product and application

Abstract

This application provides a sintering process, a sintering system apparatus, a target product, and its application. The sintering process includes: performing a first-stage sintering on a water- and sulfur-containing substance to remove a first substance, followed by a second-stage sintering to remove a second substance, thereby obtaining the target product; wherein the first-stage sintering is an n-stage sintering process, where n ≥ 2 and n is an integer; the first substance includes water, and the second substance includes sulfur. The sintering process of this application can omit the traditional flash drying process, reducing production costs and energy consumption, and simplifying the production process; through sequential first-stage and second-stage sintering, moisture and sulfur in the water- and sulfur-containing substance can be effectively removed, reducing the sulfur content in the target product and minimizing condensation.

Description

Technical Field

[0001] This application belongs to the field of battery technology and relates to a sintering process, sintering system apparatus, target product and application. Background Technology

[0002] Lithium iron phosphate (LFP) is an important cathode material for lithium-ion batteries. Due to its absence of expensive rare metals such as cobalt, it possesses excellent electrochemical performance and broad application prospects, thus attracting significant attention. With continuous societal development and increasing environmental awareness, the demand for high-performance and high-safety battery materials is constantly growing. Iron phosphate is a crucial precursor material for LFP. As the performance requirements of lithium-ion batteries continue to rise, higher demands are being placed on the cost, quality, and performance of iron phosphate precursors. Therefore, optimizing the production process of iron phosphate and improving product quality and production efficiency have become urgent issues to be addressed.

[0003] In traditional ferric phosphate production processes, filter presses are commonly used to filter and compact aqueous ferric phosphate solutions, forming ferric phosphate filter cakes with relatively low moisture content. Then, to remove free moisture from the filter cake, a flash drying process is typically required. During flash drying, the moisture in the filter cake evaporates, resulting in a drier ferric phosphate filter cake. This dried filter cake is then fed into a rotary kiln for sintering. However, flash drying requires significant energy and equipment investment, increasing production costs and energy consumption. Furthermore, the drying process in traditional methods is cumbersome, increasing production time and complexity, and reducing production efficiency. Besides drying issues, controlling sulfur content in traditional production processes is also a challenge. Sulfur may exist as an impurity in ferric phosphate during production. Ferric phosphate products with high sulfur content may not meet the requirements of specific industries, reducing the product's market competitiveness.

[0004] Furthermore, when sintering is carried out in a single hot kiln, free water, crystal water, and sulfur impurities are simultaneously degassed into a gaseous state at high temperatures and then pumped into the dust collection bin of the hot kiln under negative pressure. During the negative pressure conveying process, some materials are pumped into the dust collection bin. When the materials in the dust collection bin meet the gaseous water vapor and sulfides and reach the dew point, condensation will occur. If the materials are returned to the hot kiln for sintering, a large amount of sulfur will be introduced. If the materials are not returned to the rotary kiln, there are two ways to handle this part of the material: ① scrapping; ② reprocessing of sulfur-containing materials. This increases production costs, and the condensation can easily cause equipment malfunctions, thereby disrupting the production rhythm.

[0005] Therefore, there is an urgent need for a simple process that can effectively remove moisture, reduce sulfur content, decrease condensation, and reduce production costs and energy consumption. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] To address the shortcomings of existing technologies, the purpose of this application is to provide a sintering process, a sintering system apparatus, a target product, and its application. The sintering process of this application can omit the traditional flash drying step, reducing production costs and energy consumption, and simplifying the production process. Through sequential first-stage and second-stage sintering, moisture and sulfur in water- and sulfur-containing substances can be effectively removed, reducing the sulfur content in the target product and minimizing condensation.

[0008] To achieve this objective, the following technical solution is adopted in this application:

[0009] In a first aspect, this application provides a sintering process, the sintering process comprising:

[0010] The aqueous and sulfur-containing substances are subjected to a first-stage sintering to remove the first substance, followed by a second-stage sintering to remove the second substance, thereby obtaining the target product.

[0011] Wherein, the sintering of a section is an n-stage sintering, where n≥2 and n is an integer (for example, it can be 2 stages, 3 stages, 4 stages, 5 stages, 6 stages, 7 stages, 8 stages, 9 stages, 10 stages or 15 stages, etc.);

[0012] The first substance includes water, and the second substance includes sulfur.

[0013] This application provides a sintering process, which firstly removes moisture from water-containing and sulfur-containing substances through an n-stage sintering step in a first-stage sintering process; then, it further removes sulfur through a second-stage sintering step, reducing the sulfur content in the target product; in addition, the BET surface area of ​​the target product can be increased through the first-stage and second-stage sintering processes, thereby improving product quality.

[0014] The sintering process described in this application can omit the traditional flash drying process, reducing production costs and energy consumption, simplifying the production process, improving production efficiency, and also helping to save energy and reduce environmental pollution. The flash drying process usually requires a large amount of heat energy, and omitting this process can reduce energy consumption and carbon dioxide emissions. Furthermore, in this sintering process, gaseous sulfides and water vapor do not come into contact with the material simultaneously, which can reduce condensation, reduce waste generation, improve production continuity, improve the purity and quality of the target product, reduce impurity content, and make the product more in line with market demands and industry standards. In addition, this sintering process has a wide range of applications and can be used to dehydrate and desulfurize various water-containing and sulfur-containing substances.

[0015] In one embodiment, the aqueous sulfur-containing substance includes free water and a sulfur-containing component, wherein the sulfur-containing component includes at least one of sulfur-containing ferric phosphate dihydrate, sulfur-containing cobalt carbonate, sulfur-containing basic cobalt carbonate, and sulfur-containing cobalt hydroxide, and may be selected as sulfur-containing ferric phosphate dihydrate.

[0016] It should be noted that during the first-stage sintering process, free water is removed from the hydrous and sulfur-containing substances. Simultaneously, the water of crystallization in sulfur-containing ferric phosphate dihydrate is also removed. Furthermore, the H₂O produced during the decomposition of sulfur-containing basic cobalt carbonate and sulfur-containing cobalt hydroxide in the first-stage sintering process is also removed. In other words, the water removed during the first-stage sintering process includes at least one of free water, water of crystallization, and water produced by thermal decomposition. During the second-stage sintering process, sulfur in the sulfur-containing components can be removed. In addition, carbon dioxide is also removed from sulfur-containing cobalt carbonate and sulfur-containing basic cobalt carbonate during the second-stage sintering process.

[0017] This application does not specify the preparation process of sulfur-containing dihydrate ferric phosphate, including but not limited to the ammonia method, sodium method and iron oxide red process.

[0018] In one embodiment, with the total mass of the water-containing and sulfur-containing substances being 100%, the mass content of the free water is less than 40%, for example, it can be 39%, 36%, 35%, 32%, 30%, 25%, 20%, or 10%, etc.

[0019] In this application, when the free water content in the water-containing and sulfur-containing substances is less than 40%, the free water content is relatively low, and the dispersion effect is better during the first-stage sintering, and it will not agglomerate. If the free water content is too high, it will easily cause the feed of the first-stage sintering to get stuck, and the material cannot be effectively dispersed, resulting in agglomerated material.

[0020] In one embodiment, the water of crystallization content in the sulfur-containing dihydrate ferric phosphate is 19-21%, for example, it can be 19%, 19.5%, 20%, 20.5%, or 21%, etc.

[0021] In one embodiment, based on the total mass of the aqueous sulfur-containing substances as 100%, the mass content of sulfur in the aqueous sulfur-containing substances is 0.1-1.0%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%, etc.

[0022] In this application, if the sulfur content is too low, the sulfur removal can be completed without multi-stage hot kiln sintering. If the sulfur content is too high, it is not easy to remove, which may result in a high sulfur content in the product. Therefore, process adjustments should be made in the synthesis stage.

[0023] In one embodiment, the particle size D50 of the sulfur-containing component is 7-50 μm, for example, it can be 7 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm or 45 μm, etc.

[0024] In this application, when the particle size D50 of the sulfur-containing component is 7-50μm, the particles are relatively large, the material moisture content is low, and it is easy to disperse during feeding without producing a lot of particle agglomeration, thus reducing lumps.

[0025] In one embodiment, the n-stage sintering includes a first-stage sintering, a second-stage sintering, and an x-stage sintering, where x ≥ 3 and x is an integer, such as 3, 4, 5, 6, 7, 8, 9, 10, or 15. In this case, n ≥ 3.

[0026] It should be noted that the x-th sintering stage refers to the sintering stages other than the first and second stages in the n-stage sintering process. For example, when n = 6, the sintering segment is a 6-stage sintering process, which includes the first, second, third, fourth, fifth, and sixth stages of sintering. In this case, the x-th stage of sintering is the third, fourth, fifth, and sixth stage of sintering. The maximum value of x in the x-th stage of sintering is the same as the value of n.

[0027] In one embodiment, the temperatures of the first-stage sintering and the second-stage sintering are independently 150-250°C, for example, 150°C, 170°C, 200°C, 220°C, or 250°C.

[0028] In this application, the temperature settings of the first and second stages of sintering in the first stage of sintering are quite important. If the temperature is too high, the water-containing and sulfur-containing substances will quickly agglomerate during the dehydration process, affecting the dehydration and desulfurization process; if the temperature is too low, the moisture will be difficult to remove quickly, and there is a risk of moisture residue when entering the second stage of sintering.

[0029] The term "independently" refers to the fact that the temperature for the first-stage sintering is 150-250℃, and the temperature for the second-stage sintering is also 150-250℃. The selection of these two temperatures does not interfere with each other; they can be the same or different. The same principle applies to the rest.

[0030] In one embodiment, the temperature of the second-stage sintering is higher than the temperature of the first-stage sintering.

[0031] In this application, the temperature of the second-stage sintering is set higher than that of the first-stage sintering in order to allow free water to be gradually removed and to avoid clumping.

[0032] In one embodiment, the sintering times for the first stage and the second stage are independently 0.05-0.50 h, for example, 0.05 h, 0.1 h, 0.15 h, 0.2 h, 0.25 h, 0.3 h, 0.35 h, 0.4 h, 0.45 h, or 0.5 h, and can be selected as 0.10-0.30 h.

[0033] In this application, when the sintering time of the first stage and the second stage are independently 0.05-0.50h, the removal of free water can be completed. If the time is too short, the free water cannot be effectively removed, which will affect the removal of water such as crystal water during subsequent sintering. If the time is too long, it will result in energy waste.

[0034] In one embodiment, the temperature of the xth stage sintering is independently 200-500°C, for example, it can be 200°C, 220°C, 250°C, 300°C, 350°C, 400°C or 450°C, etc.

[0035] In this application, when the temperature of the xth stage sintering is independently 200-500℃, it is possible to remove moisture (such as water of crystallization) without removing sulfur. If the temperature is too low, it is difficult to remove water of crystallization, resulting in the removal of water of crystallization while removing sulfur in the second stage sintering, which easily leads to condensation. If the temperature is too high, the removal of sulfur is likely to occur while removing water in the first stage sintering, leading to condensation.

[0036] In one embodiment, the sintering time of the xth stage is independently 0.05-0.50h, for example, it can be 0.05h, 0.1h, 0.15h, 0.2h, 0.25h, 0.3h, 0.35h, 0.4h, 0.45h or 0.5h, etc., and can be selected as 0.10-0.30h.

[0037] In this application, when the sintering time of the xth stage is independently 0.05-0.50h, the removal of moisture (such as water of crystallization) can be effectively completed. If the time is too short, the water of crystallization will not be effectively removed in the first stage of sintering and will be removed in the second stage of sintering. Dehydration and desulfurization are both carried out in the second stage of sintering. Water vapor will condense when it encounters sulfides, which will affect the product quality. If the time is too long, it will cause energy waste.

[0038] In one embodiment, the sintering time is the same for each stage in the n-stage sintering.

[0039] In one implementation, n satisfies the following condition: 4≤n≤8, for example, it can be 4, 5, 6, 7 or 8, etc.

[0040] In this application, when n is 4≤n≤8, the number of sintering stages is appropriate, which can complete the removal of moisture without causing a lot of energy waste.

[0041] In one embodiment, the sintered product obtained by the first sintering contains trace amounts of moisture, but does not cause condensation. Based on the total mass of the sintered product as 100%, the water content in the sintered product is less than 1.5%, for example, it could be 1.4%, 1.2%, 1.0%, or 0.5%, etc.

[0042] In one embodiment, the two-stage sintering is m-level sintering, where m ≥ 2 and m is an integer, such as level 2, level 3, level 4, level 5, level 6, level 7, level 8, level 9, level 10, or level 15, etc.

[0043] In this application, when the two-stage sintering is divided into m stages, the desulfurization effect can be improved by adjusting the sintering temperature of each stage. The sintering temperatures of each stage in the m-stage sintering can be the same or different.

[0044] In one embodiment, the m-stage sintering includes a first-stage sintering, a second-stage sintering, and a y-th stage sintering, where y ≥ 3 and y is an integer. For example, y can be three, four, five, six, seven, eight, nine, ten, or fifteen, etc. In this case, m ≥ 3.

[0045] It should be noted that the y-th sintering stage refers to the sintering stages other than the first and second stages in the m-th sintering stage. For example, when m = 6, the sintering segment is a 6-stage sintering stage, which includes the first, second, third, fourth, fifth, and sixth stages of sintering; in this case, the y-th stage sintering stage is the third, fourth, fifth, and sixth stages of sintering. The maximum value of y in the y-th stage sintering stage is the same as the value of m.

[0046] In one embodiment, the temperatures of the first-stage sintering and the second-stage sintering are independently 550-750°C, for example, 550°C, 570°C, 600°C, 650°C, 700°C, or 750°C.

[0047] In this application, when the temperatures of the first-stage sintering and the second-stage sintering are independently 550-750℃, impurity S can be effectively removed. If the temperature is too low, there is no desulfurization effect, and if the temperature is too high, the energy consumption is too high and the product is prone to overheating.

[0048] In one embodiment, the sintering time for the first stage and the second stage is independently 0.10-0.50h, for example, it can be 0.1h, 0.15h, 0.2h, 0.25h, 0.3h, 0.35h, 0.4h, 0.45h or 0.5h, etc., and can be selected as 0.10-0.30h.

[0049] In this application, when the sintering time of the first stage and the second stage are independently 0.10-0.50h, if the time is too short, the desulfurization effect will be poor and the S content of the product will be too high. If the time is too long, it will easily cause the product to be overburned and the BET specific surface area will be too low.

[0050] In one embodiment, the temperature of the y-th stage sintering is independently 600-750°C, for example, it can be 600°C, 620°C, 650°C, 700°C, 720°C or 750°C, etc.

[0051] In this application, when the temperature of the y-th stage sintering is independently 600-750℃, impurity S can be effectively removed. If the temperature is too low, there is no desulfurization effect. If the temperature is too high, the energy consumption is too high and the product is easily overburned, which in turn results in a low BET specific surface area.

[0052] In one embodiment, the sintering time of the y-th stage is independently 0.10-0.50h, for example, it can be 0.1h, 0.15h, 0.2h, 0.25h, 0.3h, 0.35h, 0.4h, 0.45h or 0.5h, etc., and can be selected as 0.10-0.30h.

[0053] In this application, when the sintering time of the yth stage is independently 0.10-0.50h, if the time is too short, the desulfurization effect will be poor and the S content of the product will be too high; if the time is too long, it will easily cause the product to overburn.

[0054] In one embodiment, the sintering time is the same for each stage in the m-stage sintering.

[0055] In one implementation, m satisfies the following condition: 4≤m≤8, for example, it can be 4, 5, 6, 7 or 8, etc.

[0056] In this application, when m is 4≤m≤8, desulfurization can be completed without causing the product to overheat.

[0057] As an optional technical solution of this application, the sintering process specifically includes:

[0058] The aqueous sulfur-containing slurry is pressure filtered and crushed to obtain an aqueous sulfur-containing substance, which includes free water and sulfur-containing components. The sulfur-containing components include at least one of sulfur-containing ferric phosphate dihydrate, sulfur-containing cobalt carbonate, sulfur-containing basic cobalt carbonate, and sulfur-containing cobalt hydroxide. The aqueous sulfur-containing substance is then subjected to a first-stage sintering to remove water, followed by a second-stage sintering to remove sulfur and / or carbon dioxide, to obtain the target product.

[0059] Wherein, the sintering stage is an n-stage sintering, where 4≤n≤8 and n is an integer; the n-stage sintering includes a first-stage sintering, a second-stage sintering, and an x-stage sintering, where 3≤x≤8 and x is an integer; the temperatures of the first-stage sintering and the second-stage sintering are independently 150-250℃, and the temperature of the x-stage sintering is independently 200-500℃;

[0060] The two-stage sintering is m-stage sintering, where 4≤m≤8 and m is an integer; the m-stage sintering includes a first-stage sintering, a second-stage sintering, and a y-th stage sintering, where 3≤y≤8 and y is an integer; the temperatures of the first-stage sintering and the second-stage sintering are independently 550-750℃, and the temperature of the y-th stage sintering is independently 600-750℃.

[0061] In one embodiment, after the two-stage sintering, the process involves sieving, demagnetizing, and packaging.

[0062] Secondly, this application provides a sintering system apparatus, in which the sintering process described in the first aspect is carried out;

[0063] The sintering system includes a first-stage hot kiln and a second-stage hot kiln connected in sequence. The first-stage hot kiln is equipped with at least two sintering constant temperature zones (e.g., 2, 3, 4, 5, 6, 7, 8, 10, or 15 zones, etc.).

[0064] In one embodiment, the tilt angles of the first-stage and second-stage hot kilns are independently 0-2° and are not 0.

[0065] In this application, the primary and secondary hot kilns convey materials forward through a set tilt angle and the driving force generated by continuous rotation.

[0066] In one embodiment, the first kiln includes a first kiln head and a first kiln body connected in sequence. The first kiln head is provided with a feed inlet, a discharge outlet and a dust outlet. The feed inlet of the first kiln head is connected to a feed pipe, the discharge outlet of the first kiln head is connected to the feed end of the first kiln body, and the dust outlet of the first kiln head is connected to a first dust collection device.

[0067] In this application, the first dust collection device can draw material dust and other particles into the device through negative pressure.

[0068] In one embodiment, the first dust collection device is provided with a dust collection port and a discharge port. The dust collection port of the first dust collection device is connected to the dust discharge port of the first kiln head, and the discharge port of the first dust collection device is connected to the feed end of the first kiln body.

[0069] In this application, the material in the first dust collection device can be directly returned to the first kiln body without affecting the product quality after the first sintering stage.

[0070] In one embodiment, the two-stage hot kiln is provided with at least two sintering temperature zones (e.g., 2, 3, 4, 5, 6, 7, 8, 10 or 15, etc.).

[0071] In one embodiment, the two-stage kiln includes a second kiln head and a second kiln body connected in sequence. The second kiln head is provided with a feed inlet, a discharge outlet and a dust outlet. The feed inlet of the second kiln head is connected to the discharge end of the first kiln body. The dust outlet of the second kiln head is connected to a second dust collection device. The discharge outlet of the second kiln head is connected to the feed end of the second kiln body.

[0072] In this application, the second dust collection device can draw material dust and other particles into the device through negative pressure.

[0073] In one embodiment, the discharge end of the first kiln body is higher than the feed inlet of the second kiln head.

[0074] In one embodiment, the second dust collection device is provided with a dust collection port and a discharge port. The dust collection port of the second dust collection device is connected to the dust discharge port of the second kiln head, and the discharge port of the second dust collection device is connected to the feed end of the second kiln body.

[0075] In this application, the material in the second dust collection device can be directly returned to the second kiln body without affecting the product quality after the second sintering.

[0076] In one embodiment, the discharge end of the second kiln body is connected to a cold kiln.

[0077] In one embodiment, lifting plates are provided on the kiln walls of the first and second kiln bodies. The lifting plates are used to lift materials and dust, ensuring the contact area between the materials and the kiln body, so that the materials are completely dispersed and heat is exchanged in a timely manner, which can improve the dehydration and desulfurization effect.

[0078] In one embodiment, the sintering system further includes a filter press and a crusher. A conveying device is located below the filter press for transferring the water-containing filter cake to the crusher; the crusher is used for coarse crushing of the water-containing filter cake, after which the ferric phosphate filter cake is directly conveyed to a primary hot kiln. The crusher only breaks down the water-containing filter cake from the filter press and does not affect the product particle size. The conveying device includes a conveyor belt, a vibrating conveyor, a belt conveyor, or other suitable conveying device.

[0079] Thirdly, this application provides a target product prepared by the sintering process described in the first aspect.

[0080] In one embodiment, the target product includes ferric phosphate and / or Co3O4.

[0081] In this application, when the sulfur-containing component in the aqueous sulfur-containing substance is sulfur-containing dihydrate ferric phosphate, the target product obtained by the sintering process is ferric phosphate. When the sulfur-containing component in the aqueous sulfur-containing substance is sulfur-containing cobalt carbonate, sulfur-containing basic cobalt carbonate, or sulfur-containing cobalt hydroxide, the target product obtained by the sintering process is Co3O4.

[0082] In one embodiment, the sulfur content in the target product is 0.01-0.05% based on the total mass of the target product as 100%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%, etc.

[0083] Fourthly, this application provides a cathode material, which is obtained by sintering the target product described in the third aspect with a lithium source.

[0084] Fifthly, this application provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery includes the positive electrode material described in the fourth aspect.

[0085] The system refers to an equipment system, device system, or production device.

[0086] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0087] Compared with the prior art, the beneficial effects of this application are as follows:

[0088] This application provides a sintering process, which firstly removes moisture from water-containing and sulfur-containing substances through an n-stage sintering step in a first-stage sintering process; then, it further removes sulfur through a second-stage sintering step, reducing the sulfur content in the target product; in addition, the BET surface area of ​​the target product can be increased through the first-stage and second-stage sintering processes, thereby improving product quality.

[0089] The sintering process described in this application can omit the traditional flash drying process, reducing production costs and energy consumption, simplifying the production process, improving production efficiency, and also helping to save energy and reduce environmental pollution. The flash drying process usually requires a large amount of heat energy, and omitting this process can reduce energy consumption and carbon dioxide emissions. Furthermore, in this sintering process, gaseous sulfides and water vapor do not come into contact with the material simultaneously, which can reduce condensation, reduce waste generation, improve production continuity, improve the purity and quality of the target product, reduce impurity content, and make the product more in line with market demands and industry standards. In addition, this sintering process has a wide range of applications and can be used to dehydrate and desulfurize various water-containing and sulfur-containing substances.

[0090] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0091] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0092] Figure 1 A schematic diagram illustrating the connection relationship and structure of a primary hot kiln, a secondary hot kiln, and a cold kiln provided in Embodiment 1 of this application;

[0093] Figure 2This is a schematic diagram of the usage process of the sintering system apparatus provided in Embodiment 1 of this application;

[0094] Figure 3 An SEM image of a sintered product provided in Embodiment 1 of this application;

[0095] Figure 4 An XRD pattern of a sintered product provided in Example 1 of this application;

[0096] Figure 5 SEM image of the two-stage sintering product provided in Example 1 of this application;

[0097] Figure 6 The XRD pattern of the two-stage sintering product provided in Example 1 of this application;

[0098] Among them, 1-first stage hot kiln; 2-second stage hot kiln; 3-cold kiln; 4-first dust collection device; 5-second dust collection device. Detailed Implementation

[0099] It should be understood that in the description of this application, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0100] It should be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0101] The technical solution of this application will be further described below through specific implementation methods.

[0102] Example 1

[0103] This embodiment provides a sintering system apparatus for water- and sulfur-containing materials. The sintering system apparatus includes a filter press, a crushing device, and a first-stage hot kiln 1, a second-stage hot kiln 2, and a cold kiln 3 connected in sequence. Figure 1 As shown;

[0104] A conveying device, which is a conveyor belt, is provided below the filter press to transport the filtered material to the crushing device. The crushing device is a crusher, which is used to coarsely crush the filtered material. The coarsely crushed material is pushed into a first-stage hot kiln 1 by a screw.

[0105] The first-stage kiln 1 includes a first kiln head and a first kiln body connected in sequence. The first kiln head is provided with a feed inlet, a discharge outlet, and a dust outlet. The feed inlet of the first kiln head is connected to a feed pipe, and the discharge outlet of the first kiln head is connected to the feed end of the first kiln body. The dust outlet of the first kiln head is connected to a first dust collection device 4 (i.e., a dust collection bin). The first dust collection device 4 is provided with a dust collection outlet and a discharge outlet. The dust collection outlet of the first dust collection device 4 is connected to the dust outlet of the first kiln head, and the discharge outlet of the first dust collection device 4 is connected to the feed end of the first kiln body. The first kiln body has an inclination angle of 2°, and its kiln wall is provided with lifting plates. Eight sintering constant temperature zones are provided in the first kiln body along the material movement direction.

[0106] The two-stage kiln 2 includes a second kiln head and a second kiln body connected in sequence. The second kiln head is provided with a feed inlet, a discharge outlet, and a dust outlet. The feed inlet of the second kiln head is connected to the discharge end of the first kiln body. The dust outlet of the second kiln head is connected to a second dust collection device 5 (i.e., a dust collection bin). The discharge outlet of the second kiln head is connected to the feed end of the second kiln body. The second kiln body has an inclination angle of 2°. Lifting plates are provided on its kiln wall, and eight sintering temperature zones are provided in the second kiln body along the material movement direction.

[0107] The discharge end of the first kiln body is higher than the feed inlet of the second kiln head;

[0108] The second dust collection device 5 is equipped with a dust collection port and a discharge port. The dust collection port of the second dust collection device 5 is connected to the dust discharge port of the second kiln head, and the discharge port of the second dust collection device 5 is connected to the feed end of the second kiln body. The discharge end of the second kiln body is connected to the cold kiln 3.

[0109] The operating procedure of the sintering system is as follows: Figure 2As shown, the slurry containing water and sulfur first enters the filter press for filtration, and then is conveyed to the crushing device for crushing via a conveying device. After crushing, the material enters the first-stage hot kiln 1 for first-stage sintering. There is an exchange of material-containing water vapor and material between the first-stage hot kiln 1 and the dust collection bin connected to it. After the first-stage sintering, the material enters the second-stage hot kiln 2 for second-stage sintering. There is an exchange of material-containing sulfides and material between the second-stage hot kiln 2 and the dust collection bin connected to it. After the second-stage sintering, the material enters the cold kiln for cooling. The crushing device, the first-stage hot kiln 1 and its connected dust collection bin, the second-stage hot kiln 2 and its connected dust collection bin, and the cold kiln can be referred to as a rotary kiln system.

[0110] This embodiment also provides a sintering process for water- and sulfur-containing materials. The sintering process is carried out in the above-mentioned sintering system apparatus and includes the following steps:

[0111] (1) Slurry pretreatment: The sulfur-containing dihydrate ferric phosphate slurry is pumped into a filter press by a centrifugal pump and washed until the conductivity of the wash water is 254 μs / cm, and then discharged to the top of the belt conveyor.

[0112] (2) Coarse crushing: The filter cake with a free water content of 29.5% after pressure filtration is conveyed to the crusher and the dihydrate filter cake is initially crushed by the crusher screw; at this time, the free water content of the sulfur-containing dihydrate iron phosphate material is 29.5%, the sulfur content is 0.1477%, and the particle size D50 is 8.53μm;

[0113] (3) Dehydration: The first-stage hot kiln 1 contains 8 sintering constant temperature zones. The temperatures of each zone are set sequentially along the material movement direction as 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, and 450℃. After coarse crushing, the material is pushed to the first-stage hot kiln 1 by a screw for first-stage sintering (i.e., 8-stage sintering). The placement time in each temperature zone is 0.15h. During the first-stage sintering process, the water vapor and a small amount of material generated are drawn into the dust collection bin through negative pressure. The material is returned to the first-stage hot kiln 1 through the discharge butterfly valve, while the water vapor is drawn into the exhaust gas treatment system by a dehumidifying fan. The SEM and XRD images of the first-stage sintering products are shown below. Figure 3 and Figure 4 As shown;

[0114] (4) Desulfurization: The second-stage hot kiln 2 contains 8 sintering constant temperature zones. The temperatures of each zone are set sequentially along the material movement direction as follows: 550℃, 550℃, 600℃, 600℃, 650℃, 650℃, 700℃, and 700℃. After the first-stage sintering, the powder is transported to the second-stage hot kiln 2 for second-stage sintering (i.e., 8-stage sintering). The placement time in each temperature zone is 0.15h. During the second-stage sintering process, the sulfides generated and a small amount of material are drawn into the dust collection bin under negative pressure. Since there is no water vapor in the dust collection bin, the sulfides will not react with the material to form condensation when cooled. The material is returned to the second-stage hot kiln 2 through the discharge butterfly valve of the dust collection bin, while the sulfides are drawn into the exhaust gas treatment system by the dehumidifying fan. The SEM and XRD images of the second-stage sintering products are shown below. Figure 5 and Figure 6 As shown;

[0115] (5) Discharge: After desulfurization, anhydrous ferric phosphate is processed through screening, demagnetization, packaging and other processes to obtain qualified ferric phosphate finished product.

[0116] Example 2

[0117] The only difference between the sintering system device provided in this embodiment and that in embodiment 1 is that the first-stage hot kiln is equipped with 4 constant temperature sintering zones and the second-stage hot kiln is equipped with 6 temperature sintering zones.

[0118] The sintering process for water- and sulfur-containing materials provided in this embodiment includes the following steps:

[0119] (1) Slurry pretreatment: The sulfur-containing dihydrate ferric phosphate slurry is pumped into a filter press by a centrifugal pump and washed until the conductivity of the wash water is 325 μs / cm, and then discharged to the top of the belt conveyor.

[0120] (2) Coarse crushing: The filter cake with a free water content of 28.5% after pressure filtration is conveyed to the crusher and the dihydrate filter cake is initially crushed by the crusher screw; at this time, the free water content of the sulfur-containing dihydrate ferric phosphate material is 28.5%, the sulfur content is 0.1618%, and the particle size D50 is 10.51μm;

[0121] (3) Dehydration: The first-stage hot kiln contains four sintering constant temperature zones. The temperatures of each zone are set to 150℃, 250℃, 350℃ and 450℃ respectively along the material movement direction. After coarse crushing, the material is pushed to the first-stage hot kiln by the screw for first-stage sintering (i.e., 4-stage sintering). The placement time in each temperature zone is 0.25h. The water vapor generated during the first-stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. The material is returned to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn to the exhaust gas treatment system through the dehumidifying fan.

[0122] (4) Desulfurization: The two-stage hot kiln contains 6 sintering constant temperature zones. The temperature of each zone is set to 550℃, 600℃, 650℃, 650℃, 700℃ and 700℃ in sequence along the material movement direction. After the first stage sintering, the powder is transported to the second stage hot kiln for second stage sintering (i.e., 6-stage sintering). The placement time in each temperature zone is 0.20h. The sulfides generated during the second stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. Since there is no water vapor in the dust collection bin, the sulfides will not react with the material to form condensation when they are cooled. The material is returned to the second stage hot kiln through the discharge butterfly valve of the dust collection bin, while the sulfides are drawn to the tail gas treatment system through the dehumidifying fan.

[0123] (5) Discharge: After desulfurization, anhydrous ferric phosphate is processed through screening, demagnetization, packaging and other processes to obtain qualified ferric phosphate finished product.

[0124] Example 3

[0125] The only difference between the sintering system device provided in this embodiment and that in embodiment 1 is that the first-stage hot kiln is equipped with 6 constant temperature sintering zones and the second-stage hot kiln is equipped with 6 temperature sintering zones.

[0126] The sintering process for water- and sulfur-containing materials provided in this embodiment includes the following steps:

[0127] (1) Slurry pretreatment: The sulfur-containing dihydrate ferric phosphate slurry is pumped into a filter press by a centrifugal pump and washed until the conductivity of the wash water is 441 μs / cm, and then discharged to the top of the belt conveyor.

[0128] (2) Coarse crushing: The filter cake with a moisture content of 29.3% after pressure filtration is conveyed to the crusher, and the dihydrate filter cake is initially crushed by the crusher screw; at this time, the free water content of the sulfur-containing dihydrate ferric phosphate material is 29.3%, the sulfur content is 0.1577%, and the particle size D50 is 9.31μm;

[0129] (3) Dehydration: The first-stage hot kiln contains 6 sintering constant temperature zones. The temperature of each zone is set to 150℃, 150℃, 250℃, 350℃, 400℃ and 450℃ in sequence along the material movement direction. After coarse crushing, the material is pushed to the first-stage hot kiln by the screw for first-stage sintering (i.e. 6-stage sintering). The placement time in each temperature zone is 0.20h. The water vapor generated during the first-stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. The material is returned to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn to the exhaust gas treatment system through the dehumidifying fan.

[0130] (4) Desulfurization: The two-stage hot kiln contains 6 sintering constant temperature zones. The temperature of each zone is set to 550℃, 600℃, 650℃, 650℃, 700℃ and 700℃ in sequence along the material movement direction. After the first stage sintering, the powder is transported to the second stage hot kiln for second stage sintering (i.e., 6-stage sintering). The placement time in each temperature zone is 0.20h. The sulfides generated during the second stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. Since there is no water vapor in the dust collection bin, the sulfides will not react with the material to form condensation when they are cooled. The material is returned to the second stage hot kiln through the discharge butterfly valve of the dust collection bin, while the sulfides are drawn to the tail gas treatment system through the dehumidifying fan.

[0131] (5) Discharge: After desulfurization, anhydrous ferric phosphate is processed through screening, demagnetization, packaging and other processes to obtain qualified ferric phosphate finished product.

[0132] Example 4

[0133] The only difference between the sintering system device provided in this embodiment and that in embodiment 1 is that the first-stage hot kiln is equipped with 4 constant temperature sintering zones and the second-stage hot kiln is equipped with 4 temperature sintering zones.

[0134] The sintering process for water- and sulfur-containing materials provided in this embodiment includes the following steps:

[0135] (1) Slurry pretreatment: The sulfur-containing dihydrate ferric phosphate slurry is pumped into a filter press by a centrifugal pump and washed until the conductivity of the wash water is 387 μs / cm, and then discharged to the top of the belt conveyor.

[0136] (2) Coarse crushing: The filter cake with a moisture content of 25.4% after pressure filtration is conveyed to the crusher, and the dihydrate filter cake is initially crushed by the crusher screw; at this time, the free water content of the sulfur-containing dihydrate ferric phosphate material is 25.4%, the sulfur content is 0.1674%, and the particle size D50 is 12.51μm;

[0137] (3) Dehydration: The first-stage hot kiln contains four sintering constant temperature zones. The temperatures of each zone are set to 150℃, 250℃, 350℃ and 450℃ respectively along the material movement direction. After coarse crushing, the material is pushed to the first-stage hot kiln by the screw for first-stage sintering (i.e., 4-stage sintering). The placement time in each temperature zone is 0.25h. The water vapor generated during the first-stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. The material is returned to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn to the exhaust gas treatment system through the dehumidifying fan.

[0138] (4) Desulfurization: The two-stage hot kiln contains four sintering constant temperature zones. The temperatures of each zone are set to 550℃, 600℃, 650℃ and 700℃ respectively along the material movement direction. After the first stage sintering, the powder is transported to the second stage hot kiln for second stage sintering (i.e., 4-stage sintering). The placement time in each temperature zone is 0.25h. The sulfides generated during the second stage sintering process and a small amount of material are drawn into the dust collection bin through negative pressure. Since there is no water vapor in the dust collection bin, the sulfides will not react with the material to form condensation when they are cooled. The material is returned to the second stage hot kiln through the discharge butterfly valve of the dust collection bin, while the sulfides are drawn to the tail gas treatment system through the dehumidifying fan.

[0139] (5) Discharge: After desulfurization, anhydrous ferric phosphate is processed through screening, demagnetization, packaging and other processes to obtain qualified ferric phosphate finished product.

[0140] Example 5

[0141] The difference between this embodiment and Embodiment 1 is that, in the eight sintering constant temperature zones of the primary kiln, the temperatures of each zone are set sequentially along the material movement direction as 300℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ and 450℃.

[0142] The rest remains the same as in Example 1.

[0143] Example 6

[0144] The difference between this embodiment and embodiment 1 is that steps (3) and (4) are respectively:

[0145] (3) The first-stage hot kiln contains 8 sintering constant temperature zones. The temperatures of each zone are set sequentially along the material movement direction as 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ and 450℃. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin by negative pressure. Some water vapor and sulfides condense when they come into contact with the material after cooling. The material returns to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn into the tail gas treatment system by the dehumidifying fan.

[0146] (4) The temperature of each zone of the two-stage hot kiln is set to 650℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0147] The rest remains the same as in Example 1.

[0148] Comparative Example 1

[0149] The difference between this comparative example and Example 1 is that steps (3) and (4) are respectively:

[0150] (3) The first-stage hot kiln contains 8 sintering constant temperature zones. The temperature of each zone is set to 550℃, 550℃, 600℃, 600℃, 650℃, 650℃, 700℃ and 700℃ in sequence along the direction of material movement. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin by negative pressure. Some water vapor and sulfides condense when they come into contact with the material after cooling. The material returns to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn to the tail gas treatment system by the dehumidifying fan.

[0151] (4) The temperature of each zone of the second-stage hot kiln is set to 0℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0152] The rest remains the same as in Example 1.

[0153] Comparative Example 2

[0154] The difference between this comparative example and Example 1 is that steps (3) and (4) are respectively:

[0155] (3) The first-stage hot kiln contains 8 sintering constant temperature zones. The temperatures of each zone are set sequentially along the material movement direction as 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ and 450℃. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin by negative pressure. Some water vapor and sulfides condense when they come into contact with the material after cooling. The material returns to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn into the tail gas treatment system by the dehumidifying fan.

[0156] (4) The temperature of each zone of the second-stage hot kiln is set to 0℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0157] The rest remains the same as in Example 1.

[0158] Comparative Example 3

[0159] The difference between this comparative example and Example 1 is that steps (3) and (4) are respectively:

[0160] (3) The first-stage hot kiln contains 8 sintering constant temperature zones, and the temperature of each zone is set to 700℃. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin through negative pressure. Some water vapor and sulfides condense when they come into contact with the material after cooling. The material is returned to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn into the tail gas treatment system through the dehumidifying fan.

[0161] (4) The temperature of each zone of the second-stage hot kiln is set to 0℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0162] The rest remains the same as in Example 1.

[0163] Comparative Example 4

[0164] The difference between this comparative example and Example 1 is that steps (3) and (4) are respectively:

[0165] (3) The first-stage hot kiln contains 8 sintering constant temperature zones, and the temperature of each zone is set to 700℃. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin through negative pressure. Some water vapor and sulfides condense when they come into contact with the material after cooling. The material is returned to the first-stage hot kiln through the feeding butterfly valve, while the water vapor is drawn into the tail gas treatment system through the dehumidifying fan.

[0166] (4) The temperature of each zone of the two-stage hot kiln is set to 700℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0167] The rest remains the same as in Example 1.

[0168] Comparative Example 5

[0169] The difference between this comparative example and Example 1 is that steps (3) and (4) are respectively:

[0170] (3) The first-stage hot kiln contains 8 sintering constant temperature zones, and the temperature of each zone is set to 700℃. After coarse crushing, the material is pushed into the first-stage hot kiln by the screw for dehydration and desulfurization. The water vapor, sulfides and a small amount of material generated during the dehydration and desulfurization process are drawn into the dust collection bin through negative pressure. The material in the dust collection bin is no longer returned to the first-stage hot kiln. The material is discharged separately through the feeding butterfly valve and is not mixed with the production line material. The water vapor is drawn into the tail gas treatment system through the dehumidifying fan.

[0171] (4) The temperature of each zone of the second-stage hot kiln is set to 0℃. After the powder is sintered in the first stage, it is transported to the second-stage hot kiln and then from the second-stage hot kiln to the cold kiln.

[0172] The rest remains the same as in Example 1.

[0173] Performance testing

[0174] Test 1: The physicochemical properties of the products obtained after one-stage heating in Examples 1-6 and Comparative Examples 1-5 were determined. Specific elemental data were obtained using inductively coupled plasma atomic emission spectrometry (ICP-AES). BET specific surface area, particle size D50, and tap density TD were obtained using a specific surface area analyzer, a Malvern particle size analyzer, and a tap density analyzer, respectively. The test results are shown in Table 1. The contents of S, H2O, Fe, and P are calculated based on the total mass of the products obtained after one-stage heating in the furnace, which is 100%.

[0175] Table 1

[0176]

[0177]

[0178] As shown in Table 1, Examples 1-4 and 6 demonstrate that low-temperature sintering in a single-stage hot kiln can remove most of the moisture from sulfur-containing ferric phosphate dihydrate, but the sulfur content remains essentially unchanged. Comparative Examples 1-3 and 5 did not undergo two-stage sintering, and Comparative Example 4 did not involve graded sintering in either the single-stage or two-stage process. The results of Comparative Examples 1-5 indicate that when the first-stage temperature is high, single-stage sintering removes both sulfur and moisture simultaneously, but the sulfur removal rate is low.

[0179] As can be seen from Examples 1 and 5, if the temperature of the first temperature zone in a single-stage kiln is higher than that of the second temperature zone, it will cause the filter cake to clump together rapidly during the dehydration process, affecting the dehydration process.

[0180] Test 2: The physicochemical properties of the products obtained after two-stage furnace treatment in Examples 1-6 and Comparative Examples 1-5 were tested. Specific elemental data were obtained using inductively coupled plasma atomic emission spectrometry (ICP-AES). BET specific surface area, particle size D50, and tap density TD were obtained using a specific surface area analyzer, a Malvern particle size analyzer, and a tap density analyzer, respectively. The test results are shown in Table 2. The contents of S, H2O, Fe, and P are calculated based on the total mass of the products obtained after two-stage furnace treatment, which is 100%.

[0181] Table 2

[0182]

[0183]

[0184] Table 2 shows that, as seen in Examples 1-4, after the low-temperature sintering in the first-stage hot kiln removes most of the moisture, the second-stage hot kiln desulfurization effectively reduces the sulfur content in the product. Examples 1 and 6 show that, compared to single-temperature desulfurization, the low-high temperature platform sintering in the second-stage sintering has a better desulfurization effect, and the resulting product has a higher specific surface area. The results of Examples 1, Comparative Examples 1-3, and Comparative Example 5 show that Comparative Examples 1-3, being single-stage dehydration and desulfurization, results in condensation and poor desulfurization. Comparative Example 5, also a single-stage dehydration and desulfurization, significantly reduces the sulfur content by separately discharging the material from the dust collection bin, but this separate discharging leads to material waste and increased processing costs. The results of Examples 1 and Comparative Example 4 show that if the first-stage sintering does not use staged sintering, and both the first-stage and second-stage sintering are performed at a single temperature, the desulfurization effect is poor. Furthermore, the results of Comparative Examples 1 and 3-5 show that their products have a lower specific surface area.

[0185] As can be seen from Examples 1 and 5, if the temperature of the first temperature zone in a single-stage hot kiln is higher than that of the second temperature zone, the filter cake will quickly clump together during the dehydration process, affecting the subsequent desulfurization process and resulting in a higher sulfur content in the product.

[0186] Test 3: The iron phosphate provided in Examples 1-6 and Comparative Examples 1-5 was co-fired with lithium carbonate and glucose to prepare lithium iron phosphate cathode material. Lithium iron phosphate, conductive carbon black and polyvinylidene fluoride were dispersed in N-methylpyrrolidone to prepare cathode slurry. After coating, cathode sheet was obtained. Then, graphite was used as negative electrode and assembled with separator and LiPF6 electrolyte to form lithium-ion battery.

[0187] The compaction density of lithium iron phosphate cathode material powder was tested using a powder compaction density meter; tests were conducted using equipment such as an electrochemical workstation: ① Initial discharge capacity and initial coulombic efficiency were tested at room temperature (25℃) with a charge / discharge voltage of 2.0-3.65V and a charge / discharge rate of 0.1C; ② Cycling performance for 200 cycles was tested at room temperature (25℃) with a charge / discharge voltage of 2.0-3.65V and a charge / discharge rate of 1C.

[0188] Table 3

[0189]

[0190] As shown in Table 3, Examples 1-4 and 6 demonstrate that the precursor obtained through two-stage dehydration, desulfurization, and sintering in this application improves the powder characteristics, thereby increasing the compaction density and discharge specific capacity of the synthesized lithium iron phosphate. Compared with Comparative Examples 1-5, the comparative examples exhibit poorer overall performance, including compaction and electrochemical properties.

[0191] As can be seen from Examples 1 and 5, if the temperature of the first temperature zone in a hot kiln is higher than that of the second temperature zone, the lithium iron phosphate corresponding to the final sintered product will exhibit lower compaction density, capacity, and coulombic efficiency.

Claims

1. A sintering process, comprising: The aqueous and sulfur-containing substances are subjected to a first-stage sintering to remove the first substance, followed by a second-stage sintering to remove the second substance, thereby obtaining the target product. The aqueous sulfur-containing substance comprises free water and sulfur-containing components; based on the total mass of the aqueous sulfur-containing substance (100%), the free water content is 25-39% by mass; based on the total mass of the aqueous sulfur-containing substance (100%), the sulfur content in the aqueous sulfur-containing substance is 0.1-1.0% by mass. Wherein, the sintering stage is an n-stage sintering, where n ≥ 2 and n is an integer; the n-stage sintering includes a first-stage sintering, a second-stage sintering, and an x-stage sintering, where x ≥ 3 and x is an integer; the temperature of the second-stage sintering is higher than the temperature of the first-stage sintering; the temperatures of the first-stage sintering and the second-stage sintering are independently 150-250℃; The first substance includes water, and the second substance includes sulfur.

2. The sintering process according to claim 1, wherein, The sulfur-containing component includes at least one of sulfur-containing iron phosphate dihydrate, sulfur-containing cobalt carbonate, sulfur-containing basic cobalt carbonate, and sulfur-containing cobalt hydroxide.

3. The sintering process according to claim 1, wherein, The particle size D50 of the sulfur-containing component is 7-50 μm.

4. The sintering process according to claim 1, wherein, The sintering times for the first and second stages are independently 0.05-0.50 h.

5. The sintering process according to claim 1, wherein, The temperature for the xth stage sintering is independently 200-500℃.

6. The sintering process according to claim 1, wherein, The sintering time for the xth stage is independently 0.05-0.50 h.

7. The sintering process according to claim 1, wherein, The n satisfies the following condition: 4≤n≤8.

8. The sintering process according to claim 1, wherein, The two-stage sintering is m-stage sintering, where m ≥ 2 and m is an integer.

9. The sintering process according to claim 8, wherein, The m-stage sintering includes the first stage sintering, the second stage sintering, and the y-th stage sintering, where y ≥ 3 and y is an integer.

10. The sintering process according to claim 9, wherein, The temperatures for the first-stage sintering and the second-stage sintering are independently 550-750℃.

11. The sintering process according to claim 9, wherein, The sintering times for the first and second stages are independently 0.10-0.50 h.

12. The sintering process according to claim 9, wherein, The temperature for the y-th stage sintering is independently 600-750℃.

13. The sintering process according to claim 9, wherein, The sintering time for the y-th stage is independently 0.10-0.50 h.

14. The sintering process according to claim 8, wherein, The m satisfies the following condition: 4≤m≤8.

15. The sintering process according to claim 1, wherein, The sintering process specifically includes: The aqueous sulfur-containing slurry is pressure filtered and crushed to obtain an aqueous sulfur-containing substance, which includes free water and sulfur-containing components. The sulfur-containing components include at least one of sulfur-containing ferric phosphate dihydrate, sulfur-containing cobalt carbonate, sulfur-containing basic cobalt carbonate, and sulfur-containing cobalt hydroxide. The aqueous sulfur-containing substance is then subjected to a first-stage sintering to remove water, followed by a second-stage sintering to remove sulfur and / or carbon dioxide, to obtain the target product. Wherein, the sintering stage is an n-stage sintering, where 4≤n≤8 and n is an integer; the n-stage sintering includes a first-stage sintering, a second-stage sintering, and an x-stage sintering, where 3≤x≤8 and x is an integer; the temperatures of the first-stage sintering and the second-stage sintering are independently 150-250℃, and the temperature of the x-stage sintering is independently 200-500℃; The two-stage sintering is m-stage sintering, where 4≤m≤8 and m is an integer; the m-stage sintering includes a first-stage sintering, a second-stage sintering, and a y-th stage sintering, where 3≤y≤8 and y is an integer; the temperatures of the first-stage sintering and the second-stage sintering are independently 550-750℃, and the temperature of the y-th stage sintering is independently 600-750℃.

16. A sintering system apparatus for the sintering process according to any one of claims 1-15, comprising a first-stage hot kiln and a second-stage hot kiln connected in sequence, wherein the first-stage hot kiln is provided with at least two sintering constant temperature zones.

17. The sintering system apparatus according to claim 16, wherein, The first-stage kiln includes a first kiln head and a first kiln body connected in sequence. The first kiln head is provided with a feed inlet, a discharge outlet and a dust outlet. The feed inlet of the first kiln head is connected to a feed pipe. The discharge outlet of the first kiln head is connected to the feed end of the first kiln body. The dust outlet of the first kiln head is connected to a first dust collection device.

18. The sintering system apparatus according to claim 17, wherein, The first dust collection device is provided with a dust collection port and a discharge port. The dust collection port of the first dust collection device is connected to the dust discharge port of the first kiln head, and the discharge port of the first dust collection device is connected to the feed end of the first kiln body.

19. The sintering system apparatus according to claim 16, wherein, The two-stage hot kiln is equipped with at least two sintering temperature zones.

20. The sintering system apparatus according to claim 17, wherein, The two-stage kiln includes a second kiln head and a second kiln body connected in sequence. The second kiln head is provided with a feed inlet, a discharge outlet and a dust outlet. The feed inlet of the second kiln head is connected to the discharge end of the first kiln body. The dust outlet of the second kiln head is connected to a second dust collection device. The discharge outlet of the second kiln head is connected to the feed end of the second kiln body.

21. The sintering system apparatus according to claim 20, wherein, The second dust collection device is provided with a dust collection port and a discharge port. The dust collection port of the second dust collection device is connected to the dust discharge port of the second kiln head, and the discharge port of the second dust collection device is connected to the feed end of the second kiln body.

22. A target product prepared by the sintering process according to any one of claims 1-15.

23. A cathode material obtained by sintering the target product as described in claim 22 and a lithium source.

24. A lithium-ion battery comprising the cathode material of claim 23.

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