A method for preparing a cathode material and an intermediate thereof, and a cathode material

Abstract

This invention relates to the field of cathode material technology, specifically to a method for preparing a cathode material and its intermediates, and the cathode material itself. The method includes the following steps: crystallizing raw materials containing cathode active materials to form an aluminum-silicon-phosphorus molecular sieve on the surface of the cathode active material, thereby obtaining a cathode material intermediate. An in-situ coated layer with oriented pores is generated on the surface of the cathode active material. This coated layer can prevent direct contact between the electrolyte and the cathode active material, thereby reducing side reactions between the cathode material and the electrolyte and improving the cycle performance of the material.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, specifically to a method for preparing a cathode material and its intermediates, and the cathode material itself. Background Technology

[0002] A lithium-ion battery is a secondary battery system that uses two different lithium intercalation compounds capable of reversibly inserting and extracting lithium ions as the positive and negative electrodes, respectively. During charging, lithium ions are extracted from the crystal lattice of the positive electrode material, pass through the electrolyte, and then insert into the crystal lattice of the negative electrode material, making the negative electrode lithium-rich and the positive electrode lithium-poor. During discharging, lithium ions are extracted from the crystal lattice of the negative electrode material, pass through the electrolyte, and then insert into the crystal lattice of the positive electrode material, making the positive electrode lithium-rich and the negative electrode lithium-poor. The difference in potential between the positive and negative electrode materials relative to metallic lithium during lithium ion insertion and extraction is the battery's operating voltage.

[0003] Lithium-ion batteries are a new generation of high-performance, green, and high-energy batteries, and have become a key focus of high-tech development. Lithium-ion batteries possess the following characteristics: high voltage, high capacity, low power consumption, no memory effect, no pollution, small size, low internal resistance, low self-discharge, and a high cycle life. Due to these characteristics, lithium-ion batteries have been applied in numerous civilian and military fields, including mobile phones, laptops, camcorders, and digital cameras.

[0004] Some ideal cathode materials for high-energy-density batteries (such as lithium-rich manganese-based cathode materials) have a huge advantage in terms of high specific capacity. However, high specific capacity needs to be achieved at higher voltages (e.g., 4.6~4.8V). At high voltages, the cathode activity is stronger and the stability is weakened. Especially when fully charged, it is easy for it to undergo side reactions with the electrolyte, which can damage the material's structure and thus affect battery performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a cathode material and its intermediates, as well as the cathode material itself, to solve the technical problem that in the prior art, high-energy-density cathode materials need to achieve high specific capacity at higher voltages, but under high voltage conditions, the cathode activity is strong and the stability is weakened, especially when fully charged, which makes it very easy for it to undergo side reactions with the electrolyte, resulting in damage to the material's bulk structure and thus affecting battery performance.

[0006] This invention discloses a method for preparing a cathode material intermediate, comprising the following steps:

[0007] The raw materials containing the positive electrode active material are crystallized to form an aluminum-silicon-phosphorus molecular sieve on the surface of the positive electrode active material, thereby obtaining the positive electrode material intermediate.

[0008] Furthermore, the crystallization treatment temperature is 160℃~200℃, and the crystallization treatment time is 6~8h. For example, the crystallization treatment temperature can be 160℃, 170℃, 180℃, 190℃ or 200℃, and the crystallization treatment time can be 6h, 7h or 8h.

[0009] Furthermore, the raw materials include positive electrode active materials, aluminum salts, phosphorus-containing compounds, silicates, pure water, and organic structure directing agents.

[0010] Furthermore, by mass ratio, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate ester: pure water: organic structure directing agent = 90-110: 1.3-1.5: 1.3-1.5: 0.13-0.15: 80-120: 0.09-0.11.

[0011] For example, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate ester: pure water: organic structure directing agent can be 90:1.3:1.3:0.13:80:0.09, 100:1.4:1.4:0.14:100:0.10, 110:1.5:1.5:0.15:120:0.11 or 90:1.4:1.5:0.13:90:0.11.

[0012] Furthermore, the positive electrode active material is a lithium-rich manganese-based positive electrode active material (i.e., an existing lithium-rich manganese-based positive electrode active material or material).

[0013] Or / and, the aluminum salt is at least one of aluminum isopropoxide, aluminum sulfate, aluminum chloride and aluminum nitrate;

[0014] Or / and, the phosphorus-containing compound is at least one of phosphorus oxides, phosphoric acid, and phosphates;

[0015] Or / and, the silicate ester is at least one of tetraethyl orthosilicate or ethyl orthosilicate;

[0016] Or / and, the organic structure directing agent is methylpyrimidine.

[0017] Furthermore, the phosphorus-containing oxide is phosphorus pentoxide;

[0018] Or / and, the phosphate is at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate;

[0019] Or / and, the organic structure directing agent is at least one selected from 4-amino-2,2,6,6-tetramethylpiperidine and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine;

[0020] Or / and, before crystallization, the raw materials are mixed according to the following steps:

[0021] First, pure water and phosphorus-containing compounds are mixed, then silicate ester, organic structure directing agent and aluminum salt are added and stirred. After the silicate ester and aluminum salt have been hydrolyzed, positive electrode active material is added and mixed evenly.

[0022] Or / and, during the crystallization process, the raw materials are continuously stirred;

[0023] Or / and, after crystallization, cooling, sieving and drying operations are performed, and the sieving removes impurities mixed in the cathode material intermediate.

[0024] Furthermore, during the crystallization process, the stirring rate of the raw materials is 5-15 rpm;

[0025] For example, the stirring speed can be 5 rpm, 7 rpm, 10 rpm, 12 rpm or 15 rpm;

[0026] Or / and, the cooling rate after crystallization treatment is 5-15℃ / min;

[0027] For example, the rate can be 5℃ / min, 7℃ / min, 10℃ / min, 12℃ / min, or 15℃ / min.

[0028] Or / and, the drying temperature is 50℃-100℃, and the drying time is 1-3 hours;

[0029] For example, the drying temperature can be 50℃, 70℃, 80℃, 90℃ or 100℃, and the drying time can be 1h, 1.5h, 2h, 2.5h or 3h.

[0030] Or / and, after crystallization treatment, use an 80-200 mesh sieve for sieving;

[0031] For example, the screen mesh can be 80, 90, 100, 150, 180 or 200 mesh.

[0032] A method for preparing a cathode material involves sintering a cathode material intermediate in an oxygen-containing atmosphere to obtain the cathode material.

[0033] Furthermore, the volume fraction of oxygen in the oxygen-containing atmosphere is 97%-100%, the sintering temperature is 150℃-220℃, and the sintering time is 5-10h.

[0034] For example, the volume fraction can be 97%, 98%, 99% or 100%, the sintering temperature can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃ or 220℃, and the sintering time can be 5h, 6h, 7h, 8h, 9h or 10h.

[0035] Furthermore, the positive electrode active material is LiaNibCocMndO2, where 1≤a≤1.5, (b+c):d=1:2.

[0036] For example, 'a' can be 1.1, 1.2, 1.3, 1.4, or 15.

[0037] A positive electrode material is prepared using the method described above.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. An in-situ coating layer with oriented pores is generated on the surface of the positive electrode active material. The coating layer can block the direct contact between the electrolyte and the positive electrode active material, especially reducing the side reactions between the positive electrode material and the electrolyte, and improving the cycle performance of the material.

[0040] 2. By generating an in-situ coating layer with oriented pores, manganese in the positive electrode active material (such as existing lithium-rich manganese-based positive electrode active materials) cannot dissolve in the electrolyte, thus protecting the structure of the positive electrode active material from damage and improving the material's cycle performance. Furthermore, manganese dissolution will have adverse effects on the negative electrode (for example, manganese deposition on the negative electrode will form dendrites, pierce the separator, and cause a short circuit in the battery; manganese deposition on the negative electrode will reduce the lithium insertion rate and the total amount of lithium inserted (reducing the negative electrode capacity)), further improving cycle performance.

[0041] 3. By generating a coating layer with directional pores in situ, the oxygen release of the positive electrode active material (such as lithium-rich manganese-based positive electrode active material) at high voltage is improved (at high voltage, oxygen atoms escape from the positive electrode to form oxygen, which reacts with the electrolyte and negative electrode in a redox reaction, leading to battery failure). The directional pores ensure that the produced oxygen can only exist inside the positive electrode material, preventing it from contacting the electrolyte and negative electrode, thereby improving the material's cycle performance. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a microstructure diagram of the cathode material in Example 1 of the present invention.

[0044] Figure 2 This is a microstructure diagram of the cathode material of Comparative Example 7 of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] In this embodiment, the positive electrode active material is Li a Ni b Co c Mn d O2, where 1≤a≤1.5, (b+c):d=1:2.

[0047] Example 1

[0048] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself, including the following steps:

[0049] Weigh out 10g of lithium-rich manganese-based positive electrode active material, 0.14g of aluminum isopropoxide, 0.14g of phosphoric acid, 0.014g of tetraethyl orthosilicate, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following ratio: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine. Pour the pure water into a stainless steel reactor, add the phosphoric acid, and start stirring at 50 rpm for 5 minutes. After stirring, add the tetraethyl orthosilicate in sequence. Tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide were stirred for 3 hours to completely hydrolyze the tetraethyl orthosilicate and aluminum isopropoxide. After stirring, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 180°C for crystallization, forming an aluminum-silicon-phosphorus molecular sieve (SAPO-34) on the positive electrode surface. The crystallization time was 7 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 01.

[0050] Example 2

[0051] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself, including the following steps:

[0052] Weigh out 9g of lithium-rich manganese-based positive electrode active material, 0.13g of aluminum isopropoxide, 0.13g of phosphoric acid, 0.013g of tetraethyl orthosilicate, 8g of pure water, and 0.009g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following ratio: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine. Pour the pure water into a stainless steel reactor, add the phosphoric acid, and start stirring at 50 rpm for 5 minutes. After stirring, add the orthosilicate... Tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide were stirred for 3 hours to completely hydrolyze the tetraethyl orthosilicate and aluminum isopropoxide. After stirring, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 160°C for crystallization, forming an aluminum-silicon-phosphorus molecular sieve (SAPO-34) on the positive electrode surface. The crystallization time was 6 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 02.

[0053] Example 3

[0054] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself, including the following steps:

[0055] Weigh out 11g of lithium-rich manganese-based positive electrode active material, 0.15g of aluminum isopropoxide, 0.15g of phosphoric acid, 0.015g of tetraethyl orthosilicate, 12g of pure water, and 0.011g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following ratio: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine. Pour the pure water into a stainless steel reactor, add the phosphoric acid, start stirring at 50 rpm for 5 minutes. After stirring, add the... Tetraethyl silicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide were stirred for 3 hours to completely hydrolyze the tetraethyl silicate and aluminum isopropoxide. After stirring, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 200°C for crystallization, forming an aluminum-silicon-phosphorus molecular sieve (SAPO-34) on the positive electrode surface. The crystallization time was 8 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 03.

[0056] Comparative Example 1

[0057] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate. The specific steps include:

[0058] According to the formula of lithium-rich manganese-based positive electrode active material: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 100:100:0.1, weigh 10g of lithium-rich manganese-based positive electrode active material, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine. Pour the pure water into a stainless steel reactor, start stirring at 50 rpm for 5 minutes. After stirring, add 4-hydroxy-1,2,2,6,6-pentamethylpiperidine and stir for 3 hours. After stirring, add the lithium-rich manganese-based positive electrode active material and stir for 5 minutes to ensure thorough mixing. Seal the reactor and heat to 180℃ for crystallization for 7 hours, reducing the stirring speed to 10 rpm during crystallization. After crystallization, stop stirring, rapidly cool the reactor with room temperature water, sieve the material, and dry at 80℃ for 2 hours. Transfer the material to a crucible and heat at 200℃ in an oxygen atmosphere. Sintering in a tubular furnace for 5 hours yields a lithium-rich manganese-based cathode material with in-situ oriented pores, denoted as cathode material 04.

[0059] Comparative Example 2

[0060] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate, and a change in the material ratios. Specifically, the method includes the following steps:

[0061] Weigh out 9g of lithium-rich manganese-based positive electrode active material, 8g of pure water, and 0.009g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the ratio of lithium-rich manganese-based positive electrode active material: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 90:80:0.09. Pour the pure water into a stainless steel reactor, start stirring at 50 rpm for 5 minutes. After stirring, add 4-hydroxy-1,2,2,6,6-pentamethylpiperidine and stir for 3 hours. After stirring, add the lithium-rich manganese-based positive electrode active material and stir for 5 minutes to ensure thorough mixing. Seal the reactor and heat to 160℃ for crystallization for 6 hours, reducing the stirring speed to 10 rpm during crystallization. After crystallization, stop stirring, rapidly cool the reactor with room temperature water, sieve the material, and dry at 80℃ for 2 hours. Transfer the material to a crucible and heat at 200℃ in an oxygen atmosphere. Sintering in a tubular furnace for 5 hours yields a lithium-rich manganese-based cathode material with in-situ oriented pores, denoted as cathode material 05.

[0062] Comparative Example 3

[0063] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate, and a change in the material ratios. Specifically, the method includes the following steps:

[0064] Weigh out 11g of lithium-rich manganese-based positive electrode active material, 12g of pure water, and 0.011g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the ratio of lithium-rich manganese-based positive electrode active material: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 110:120:0.11. Pour the pure water into a stainless steel reactor, start stirring at 50 rpm for 5 minutes. After stirring, add 4-hydroxy-1,2,2,6,6-pentamethylpiperidine and stir for 3 hours. After stirring, add the lithium-rich manganese-based positive electrode active material and stir for 5 minutes to ensure thorough mixing. Seal the reactor and heat to 200℃ for crystallization for 8 hours, reducing the stirring speed to 10 rpm during crystallization. After crystallization, stop stirring, rapidly cool the reactor with room temperature water, sieve the material, and dry at 80℃ for 2 hours. Transfer the material to a crucible and heat at 200℃ in an oxygen atmosphere. Sintering in a tubular furnace for 5 hours yields a lithium-rich manganese-based cathode material with in-situ oriented pores, denoted as cathode material 06.

[0065] Comparative Example 4

[0066] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of phosphoric acid. Specifically, the method includes the following steps:

[0067] Weigh out 10g of lithium-rich manganese-based positive electrode active material, 0.14g of aluminum isopropoxide, 0.014g of tetraethyl orthosilicate, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following formula: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 100:1.4:0:0.14:100:0.1. Pour the pure water into a stainless steel reactor and start stirring at 50 rpm for 5 minutes. After stirring, add tetraethyl orthosilicate and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine in sequence. 1,2,2,6,6-pentamethylpiperidine and aluminum isopropoxide were stirred for 3 hours to completely hydrolyze tetraethyl orthosilicate and aluminum isopropoxide. After stirring, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 180°C for crystallization, forming an aluminum-silicon molecular sieve (SAPO-34) on the positive electrode surface. The crystallization time was 7 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours in an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 07.

[0068] Comparative Example 5

[0069] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of aluminum isopropoxide. Specifically, the method includes the following steps:

[0070] Weigh out 10g of lithium-rich manganese-based positive electrode active material, 0.14g of phosphoric acid, 0.014g of tetraethyl orthosilicate, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following formula: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 100:0:1.4:0.14:100:0.1. Pour the pure water into a stainless steel reactor, add the phosphoric acid, start stirring at 50 rpm for 5 minutes. After stirring, proceed sequentially... Tetraethyl orthosilicate and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine were added and stirred for 3 hours to completely hydrolyze the tetraethyl orthosilicate. After stirring, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 180°C for crystallization, forming a silicon-phosphorus molecular sieve on the positive electrode surface. The crystallization time was 7 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours under an oxygen atmosphere to obtain the lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 08.

[0071] Comparative Example 6

[0072] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only difference from Example 1 is the omission of tetraethyl orthosilicate. The specific steps include:

[0073] Weigh out 10g of lithium-rich manganese-based positive electrode active material, 0.14g of aluminum isopropoxide, 0.14g of phosphoric acid, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following ratio: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine. Pour the pure water into a stainless steel reactor, add the phosphoric acid, start stirring at 50 rpm for 5 minutes. After stirring, according to... 4-Hydroxy-1,2,2,6,6-pentamethylpiperidine and aluminum isopropoxide were added, and the mixture was stirred for 3 hours to ensure complete hydrolysis of the aluminum isopropoxide. After stirring, lithium-rich manganese-based positive electrode active material was added, and the mixture was stirred for 5 minutes to ensure thorough mixing. The reactor was sealed and heated to 180°C for crystallization, forming an aluminum-phosphorus molecular sieve on the positive electrode surface. The crystallization time was 7 hours, and the rotation speed was reduced to 10 rpm during crystallization. After crystallization, stirring was stopped, and the reactor was rapidly cooled with room temperature water. The material was then sieved and dried at 80°C for 2 hours. The material was transferred to a crucible and sintered in a tube furnace at 200°C for 5 hours under an oxygen atmosphere to obtain the lithium-rich manganese-based positive electrode material with in-situ oriented pores, denoted as positive electrode material 09.

[0074] Comparative Example 7

[0075] This embodiment discloses a method for preparing a cathode material and its intermediates, as well as the cathode material itself. The only change from Embodiment 1 is the omission of the crystallization step. Specifically, it includes the following steps:

[0076] Weigh out 10g of lithium-rich manganese-based positive electrode active material, 0.14g of aluminum isopropoxide, 0.14g of phosphoric acid, 0.014g of tetraethyl orthosilicate, 10g of pure water, and 0.01g of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine according to the following ratio: lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 100:1.4:1.4:0.14:100:0.1. Pour the pure water into a stainless steel reactor. Add phosphoric acid to the reactor, start stirring at 50 rpm for 5 minutes; after stirring, add tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide in sequence, and stir for 3 hours to completely hydrolyze tetraethyl orthosilicate and aluminum isopropoxide; after stirring, add lithium-rich manganese-based positive electrode active material, stir for 5 minutes to mix it thoroughly; sieve the material directly and dry it at 80℃ for 2 hours; transfer the material to a crucible and sinter it in a tube furnace at 200℃ for 5 hours in an oxygen atmosphere to obtain lithium-rich manganese-based positive electrode material without in-situ directional pores, denoted as positive electrode material 10.

[0077] Table 1 Comparison of coin cell and compaction densities of cathode materials

[0078]

[0079] As shown in Table 1, the specific surface area of ​​cathode materials 01-03 and 07-09 is slightly higher than that of the others. This is because the in-situ generation of molecular sieves on the surface of these cathode materials creates more pores, which increases the specific surface area of ​​the materials. In contrast, the specific surface area of ​​the remaining cathode materials is lower, especially cathode material 10 (which does not have in-situ generated molecular sieves). The cathode materials with in-situ generated molecular sieves showed a maximum 20.46% increase in the 500-cycle retention rate and a 13-fold reduction in manganese leaching compared to those without. This indicates that the in-situ generated molecular sieves effectively isolate the direct contact between the electrolyte and the cathode material, reducing the erosion of the cathode material by the electrolyte, reducing oxygen release and manganese leaching, thereby improving the stability and cycle performance of the materials.

[0080] from Figure 1 The surface of the material is noticeably rough, indicating that a molecular sieve structure has been formed in situ on the surface of the cathode material. The molecular sieve formed in situ can effectively isolate the erosion of the electrolyte, thereby reducing manganese dissolution, inhibiting oxygen release (oxygen release and manganese dissolution occur simultaneously, oxygen release leads to manganese dissolution, and manganese dissolution will further aggravate oxygen release), and improving the stability and cycle performance of the material.

[0081] from Figure 2 As can be seen, the material surface is very smooth. In this comparative experiment, the in-situ molecular sieve generation process was not carried out, resulting in poor material circulation and a large amount of manganese leaching.

[0082] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A method for preparing a cathode material intermediate, characterized in that: Includes the following steps: The raw materials containing the positive electrode active material are crystallized to form an aluminum-silicon-phosphorus molecular sieve on the surface of the positive electrode active material, thereby obtaining the positive electrode material intermediate. The raw materials include positive electrode active materials, aluminum salts, phosphorus-containing compounds, silicates, pure water, and organic structure directing agents; Before crystallization, the raw materials are mixed according to the following steps: First, pure water and phosphorus-containing compounds are mixed, then silicate ester, organic structure directing agent and aluminum salt are added and stirred. After the silicate ester and aluminum salt have been hydrolyzed, positive electrode active material is added and mixed evenly.

2. The method for preparing the cathode material intermediate according to claim 1, characterized in that: The crystallization treatment temperature is 160℃-200℃, and the crystallization treatment time is 6-8h.

3. The method for preparing the cathode material intermediate according to claim 1, characterized in that: By mass ratio, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate ester: pure water: organic structure directing agent = 90-110: 1.3-1.5: 1.3-1.5: 0.13-0.15: 80-120: 0.09-0.

11.

4. The method for preparing the cathode material intermediate according to claim 1 or 3, characterized in that: The positive electrode active material is a lithium-rich manganese-based positive electrode active material; Or / and, the aluminum salt is at least one of aluminum isopropoxide, aluminum sulfate, aluminum chloride and aluminum nitrate; Or / and, the phosphorus-containing compound is at least one of phosphorus oxides, phosphoric acid, and phosphates; Or / and, the silicate ester is at least one of tetraethyl orthosilicate or ethyl orthosilicate.

5. The method for preparing the cathode material intermediate according to claim 4, characterized in that: The phosphorus-containing oxide is phosphorus pentoxide; Or / and, the phosphate is at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; Or / and, the organic structure directing agent is at least one selected from 4-amino-2,2,6,6-tetramethylpiperidine and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine; Or / and, during the crystallization process, the raw materials are continuously stirred; Or / and, after crystallization, cooling, sieving and drying operations are performed, and the sieving removes impurities mixed in the cathode material intermediate.

6. The method for preparing the cathode material intermediate according to claim 5, characterized in that: During the crystallization process, the stirring rate of the raw materials is 5-15 rpm; Or / and, the cooling rate after crystallization treatment is 5-15℃ / min; Or / and, the drying temperature is 50℃-100℃, and the drying time is 1-3 hours; Or / and, after crystallization, use an 80-200 mesh sieve for sieving.

7. A method for preparing a positive electrode material, characterized in that: Includes the following steps: A cathode material intermediate is prepared by the preparation method according to any one of claims 1-6, and the cathode material intermediate is sintered in an oxygen-containing atmosphere to obtain the cathode material.

8. The method for preparing the cathode material according to claim 7, characterized in that: The oxygen volume fraction in the oxygen-containing atmosphere is 97%-100%, the sintering temperature is 150℃-220℃, and the sintering time is 5-10h.

9. A cathode material, characterized in that: It is prepared using the preparation method according to any one of claims 7-8.

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