Positive electrode material, preparation method of intermediate of positive electrode material and positive electrode material

Abstract

The invention relates to the technical field of positive electrode materials, in particular to a preparation method of a positive electrode material and an intermediate thereof and a positive electrode material.The preparation method comprises the following steps that a raw material containing a positive electrode active material is subjected to crystallization treatment, an aluminum-silicon-phosphorus molecular sieve is formed on the surface of the positive electrode active material, and the positive electrode material intermediate is obtained. The coating layer with directional pores is generated on the surface of the positive electrode active material in situ, and the coating layer can prevent direct contact between an electrolyte and the positive electrode active material, so that side reaction between the positive electrode material and the electrolyte is reduced, and the cycle performance of the material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of positive electrode materials, and in particular to a preparation method of a positive electrode material and an intermediate thereof, as well as the positive electrode material. Background Art

[0002] Lithium-ion batteries are secondary battery systems that use two different lithium-intercalating compounds that can reversibly insert and remove lithium ions as the positive and negative electrodes, respectively. During charging, lithium ions are removed from the positive electrode material's lattice, then inserted into the negative electrode material's lattice after passing through the electrolyte, making the negative electrode lithium-rich and the positive electrode lithium-poor. During discharge, lithium ions are removed from the negative electrode material's lattice, then inserted into the positive electrode material's lattice after passing through the electrolyte, 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 green, high-energy batteries with superior performance and have become a key focus of high-tech development. They boast high voltage, high capacity, low power consumption, no memory effect, no environmental impact, small size, low internal resistance, low self-discharge, and a high cycle life. These advantages have led to their application in numerous civilian and military applications, 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 their high gram capacity. However, high gram capacity needs to be achieved at a higher voltage (for example, 4.6~4.8V). Under high voltage conditions, the cathode activity is stronger and the stability is weakened, especially when fully charged. This makes it very easy for it to undergo side reactions with the electrolyte, causing damage to the material's structure and thus affecting battery performance. Summary of the Invention

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

[0006] The present invention discloses a method for preparing a positive electrode material intermediate, comprising the following steps: The raw materials containing the positive electrode active material are crystallized to form aluminum silicon phosphorus molecular sieve on the surface of the positive electrode active material to obtain the positive electrode material intermediate.

[0007] Furthermore, the crystallization treatment temperature is 160°C to 200°C, and the crystallization treatment time is 6 to 8 hours. For example, the crystallization treatment temperature can be 160°C, 170°C, 180°C, 190°C or 200°C, and the crystallization treatment time can be 6 hours, 7 hours or 8 hours.

[0008] Furthermore, the raw materials include positive electrode active material, aluminum salt, phosphorus-containing compound, silicate, pure water and organic structure directing agent.

[0009] Furthermore, in terms of mass ratio, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate: 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.

[0010] For example, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate: 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.

[0011] 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); 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-containing oxides, phosphoric acid and phosphates; Or / and, the silicate is at least one of tetraethyl orthosilicate or ethyl silicate; Or / and, the organic structure directing agent is methyl pyrimidine.

[0012] Furthermore, 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 of 4-amino-2,2,6,6-tetramethylpiperidine and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine; Or / and, before crystallization, the raw materials are mixed according to the following steps: First, pure water and a phosphorus-containing compound are mixed, and then silicate, an organic structure-directing agent, and an aluminum salt are added and stirred to mix. After the silicate and the aluminum salt are hydrolyzed, the positive electrode active material is added and mixed evenly. or / and, continuously stirring the raw materials during the crystallization process; or / and, performing cooling, screening and drying operations after the crystallization treatment, wherein impurities mixed in the positive electrode material intermediate are removed by the screening.

[0013] Furthermore, during the crystallization process, the stirring rate of the raw material is 5-15 rpm; For example, the stirring rate may be 5 rpm, 7 rpm, 10 rpm, 12 rpm or 15 rpm; or / and, the cooling rate after the crystallization treatment is 5-15°C / min; For example, the rate can be 5°C / min, 7°C / min, 10°C / min, 12°C / min, or 15°C / min.

[0014] Or / and, the drying temperature is 50 ℃ -100 ℃, the drying time is 1-3h; For example, the drying temperature may be 50° C., 70° C., 80° C., 90° C., or 100° C., and the drying time may be 1 h, 1.5 h, 2 h, 2.5 h, or 3 h.

[0015] or / and, after the crystallization treatment, sieving using a sieve of 80-200 mesh; For example, the screen may be 80, 90, 100, 150, 180 or 200 mesh.

[0016] A method for preparing a positive electrode material comprises sintering the positive electrode material intermediate in an oxygen-containing atmosphere to obtain the positive electrode material.

[0017] Furthermore, the volume fraction of oxygen in the oxygen-containing atmosphere is 97%-100%, the sintering temperature is 150° C.-220° C., and the sintering time is 5-10 hours.

[0018] For example, the volume fraction can be 97%, 98%, 99% or 100%, the sintering temperature can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C, and the sintering time can be 5h, 6h, 7h, 8h, 9h or 10h.

[0019] Furthermore, the positive electrode active material is LiaNibCocMndO2, wherein 1≤a≤1.5, (b+c):d=1:2.

[0020] For example, a can be 1.1, 1.2, 1.3, 1.4 or 15.

[0021] A positive electrode material is prepared using the above method.

[0022] Compared with the prior art, the present invention has the following beneficial effects: By in-situ generating a coating layer with directional pores on the surface of the positive electrode active material, the coating layer can block direct contact between the electrolyte and the positive electrode active material, especially reduce the side reaction between the positive electrode material and the electrolyte, and improve the cycle performance of the material; by in-situ generating a coating layer with directional pores, the manganese element in the positive electrode active material (such as the existing lithium-rich manganese-based positive electrode active material) cannot be dissolved in the electrolyte, thereby protecting the structure of the positive electrode active material from being destroyed, improving the cycle performance of the material, and the manganese dissolution will have an adverse effect on the negative electrode (for example, manganese elements are deposited at the negative electrode to form dendrites, piercing the diaphragm, Leading to battery short circuit; manganese elements are deposited at the negative electrode, reducing the negative electrode lithium insertion rate and the total amount of insertion (reducing the negative electrode capacity), further improving the cycle performance; by in-situ generating a coating layer with directional pores, 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 undergoes redox reactions with the electrolyte and the negative electrode, causing battery failure). The directional pores can only allow the produced oxygen to exist inside the positive electrode material, preventing it from contacting the electrolyte and the negative electrode, thereby improving the material's cycle performance. In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only represent some embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a microstructure diagram of the positive electrode material of Example 1 of the present invention.

[0024] Figure 2 This is a microstructure diagram of the positive electrode material of Comparative Example 7 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0026] In the 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.

[0027] Example 1 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and the positive electrode material, comprising the following steps: According to the 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, 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 were weighed; pure water was poured into a stainless steel reactor, and phosphoric acid was added, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after stirring, the orthosilicon was added in sequence. Tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide were added and stirred for 3 hours to completely hydrolyze tetraethyl orthosilicate and aluminum isopropoxide; after stirring, lithium-rich manganese-based positive electrode active materials were added and stirred for 5 minutes to fully mix; the reactor was sealed and heated to 180°C for crystallization to form aluminum silicon phosphorus molecular sieve (SAPO-34) on the positive electrode surface for 7 hours, and the rotation speed was reduced to 10 rpm during crystallization; after crystallization, stirring was stopped, and the reactor was quickly cooled with room temperature water, the material was sieved, and dried at 80°C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200°C in an oxygen atmosphere for 5 hours to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 01.

[0028] Example 2 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and the positive electrode material, comprising the following steps: According to the ratio of lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 90:1.3:1.3:0.13:80:0.09, 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 were weighed; pure water was poured into a stainless steel reactor, and phosphoric acid was added, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after stirring, orthosilicic acid was added in sequence. Tetraethyl orthosilicate, 4-hydroxy-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 materials were added and stirred for 5 minutes to fully mix; the reactor was sealed and heated to 160°C for crystallization to form aluminum silicon phosphorus molecular sieve (SAPO-34) on the positive electrode surface for 6 hours, and the rotation speed was reduced to 10 rpm during crystallization; after crystallization, stirring was stopped, and the reactor was quickly cooled with room temperature water, the material was sieved, and dried at 80°C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 02.

[0029] Example 3 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and the positive electrode material, comprising the following steps: According to the ratio of lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 110:1.5:1.5:0.15:120:0.11, 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 were weighed; pure water was poured into a stainless steel reactor, and phosphoric acid was added, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after stirring, the positive electrode was added in sequence. Tetraethyl orthosilicate, 4-hydroxy-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 materials were added and stirred for 5 minutes to fully mix; the reactor was sealed and heated to 200°C for crystallization to form 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 quickly cooled with room temperature water, the material was sieved, and dried at 80°C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 03.

[0030] Comparative Example 1 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The method is different from that in Example 1 except that aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate are not added. The method specifically includes the following steps: According to the 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, stir at a speed of 50rpm, and stir for 5min; after stirring, add 4-hydroxy-1,2,2,6,6-pentamethylpiperidine and stir for 3h; after stirring, add the lithium-rich manganese-based positive electrode active material and stir for 5min to fully mix; seal the reactor, heat to 180℃ for crystallization, the crystallization time is 7h, and the speed is reduced to 10rpm during crystallization; after crystallization, stop stirring, use room temperature water to quickly cool the reactor, sieve the material, and dry it at 80℃ for 2h; transfer the material into a sagger and sieve it at 200℃ under an oxygen atmosphere. After sintering in a tubular furnace for 5 hours, a lithium-rich manganese-based positive electrode material with in-situ generated directional pores was obtained, which was recorded as positive electrode material 04.

[0031] Comparative Example 2 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The method is similar to that of Example 1 except that aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate are not added and the material ratio is changed. The method specifically includes the following steps: 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, 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 were weighed; the pure water was poured into a stainless steel reactor, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after the stirring was completed, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine was added and stirred for 3h; after the stirring was completed, the lithium-rich manganese-based positive electrode active material was added and stirred for 5min to fully mix; the reactor was sealed and heated to 160℃ for crystallization for 6h, and the speed was reduced to 10rpm during crystallization; after the crystallization was completed, stirring was stopped, the reactor was quickly cooled with room temperature water, the material was sieved, and dried at 80℃ for 2h; the material was transferred to a sagger and dried at 200℃ under an oxygen atmosphere. After sintering in a tubular furnace for 5 hours, a lithium-rich manganese-based positive electrode material with in-situ generated directional pores was obtained, which was recorded as positive electrode material 05.

[0032] Comparative Example 3 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The method is similar to that of Example 1 except that aluminum isopropoxide, phosphoric acid, and tetraethyl orthosilicate are not added and the material ratio is changed. The method specifically includes the following steps: 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, 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 were weighed; pure water was poured into a stainless steel reactor, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after the stirring was completed, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine was added and stirred for 3h; after the stirring was completed, the lithium-rich manganese-based positive electrode active material was added and stirred for 5min to mix thoroughly; the reactor was sealed and heated to 200℃ for crystallization for 8h, and the speed was reduced to 10rpm during crystallization; after the crystallization was completed, stirring was stopped, the reactor was quickly cooled with normal temperature water, the material was sieved, and dried at 80℃ for 2h; the material was transferred to a sagger and dried at 200℃ in an oxygen atmosphere. After sintering in a tubular furnace for 5 hours, a lithium-rich manganese-based positive electrode material with in-situ generated directional pores was obtained, which was recorded as positive electrode material 06.

[0033] Comparative Example 4 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The only difference from Example 1 is that phosphoric acid is not added. Specifically, the method includes the following steps: According to the ratio of 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, 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 were weighed; pure water was poured into a stainless steel reactor and stirred at a speed of 50rpm for 5min; after stirring, tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine were added in sequence. After the stirring was completed, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to fully mix; the reactor was sealed and heated to 180 ° C for crystallization to form 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 the crystallization was completed, the stirring was stopped and the reactor was quickly cooled with room temperature water. The material was sieved and dried at 80 ° C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200 ° C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 07.

[0034] Comparative Example 5 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The only difference from Example 1 is that aluminum isopropoxide is not added. Specifically, the method includes the following steps: According to the 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, 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 were weighed; pure water was poured into a stainless steel reactor, and phosphoric acid was added, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after stirring was completed, 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 fully mix; the reactor was sealed and heated to 180°C for crystallization to form 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 was completed, stirring was stopped, and the reactor was quickly cooled with room temperature water, the material was sieved, and dried at 80°C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200°C for 5 hours in an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 08.

[0035] Comparative Example 6 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The method is different from that in Example 1 except that tetraethyl orthosilicate is not added. The method specifically includes the following steps: According to the lithium-rich manganese-based positive electrode active material: aluminum isopropoxide: phosphoric acid: tetraethyl orthosilicate: pure water: 4-hydroxy-1,2,2,6,6-pentamethylpiperidine = 100:1.4:0.14:0:100:0.1, 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 were weighed; pure water was poured into a stainless steel reactor, and phosphoric acid was added, stirring was started, the stirring speed was 50rpm, and stirring was carried out for 5min; after stirring was completed, the mixture was stirred according to the reaction mixture. 4-Hydroxy-1,2,2,6,6-pentamethylpiperidine and aluminum isopropoxide were added in turn and stirred for 3 hours to completely hydrolyze the aluminum isopropoxide; after the stirring was completed, lithium-rich manganese-based positive electrode active material was added and stirred for 5 minutes to fully mix; the reactor was sealed and heated to 180°C for crystallization to form 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 the crystallization was completed, the stirring was stopped, and the reactor was quickly cooled with room temperature water. The material was sieved and dried at 80°C for 2 hours; the material was transferred to a sagger and sintered in a tubular furnace at 200°C for 5 hours in an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material with in-situ generated directional pores, which was recorded as positive electrode material 09.

[0036] Comparative Example 7 This embodiment discloses a method for preparing a positive electrode material and an intermediate thereof, and a positive electrode material. The only difference from Example 1 is that the crystallization step is omitted. Specifically, the following steps are included: According to the ratio of 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, 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 were weighed; pure water was poured into a stainless steel reactor. Phosphoric acid was added to the reactor, and stirring was started at 50 rpm for 5 minutes. After stirring, tetraethyl orthosilicate, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and aluminum isopropoxide were added in sequence and 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 fully mix. The material was directly sieved and dried at 80°C for 2 hours. The material was transferred to a sagger and sintered in a tubular furnace at 200°C for 5 hours under an oxygen atmosphere to obtain a lithium-rich manganese-based positive electrode material without in-situ generated directional pores, which was recorded as positive electrode material 10.

[0037] Table 1 Comparison of the density of positive electrode materials withholding and compaction

[0038] As can be seen from Table 1, the specific surface areas of positive electrode materials 01~03 and positive electrode materials 07~09 are slightly higher than the others. The in-situ generated molecular sieves on the surface of the positive electrode materials have more pores, which increases the specific surface area of the materials, while the specific surface areas of the other positive electrode materials are relatively low, especially positive electrode material 10 (no in-situ generated molecular sieves). Compared with the positive electrode materials without in-situ generated molecular sieves, the positive electrode materials with in-situ generated molecular sieves have a maximum cycle retention rate of 20.46% after 500 cycles, and manganese dissolution is reduced by 13 times, indicating that the in-situ generated molecular sieves effectively isolate the direct contact between the electrolyte and the positive electrode materials, reduce the erosion of the electrolyte on the positive electrode materials, reduce oxygen release and manganese dissolution, and thus improve the stability and cycle performance of the materials.

[0039] from Figure 1 It can be seen that the surface of the material is significantly rough, indicating that a molecular sieve structure has been formed in situ on the surface of the positive electrode material; the in situ generated molecular sieve can effectively isolate the erosion of the electrolyte, thereby reducing manganese dissolution and inhibiting oxygen release (oxygen release and manganese dissolution occur simultaneously, oxygen release causes manganese dissolution, and manganese dissolution further aggravates oxygen release), thereby improving material stability and cycle performance.

[0040] from Figure 2 It can be seen from the figure that the surface of the material is very smooth. In this comparative experiment, the in-situ molecular sieve generation process was not carried out, resulting in poor material circulation and more manganese dissolution.

[0041] The above are the implementation methods listed in this embodiment, but this embodiment is not limited to the above optional implementation methods. Those skilled in the art can arbitrarily combine the above methods to obtain other various implementation methods. Anyone can derive other various forms of implementation methods based on the inspiration of this embodiment. The above specific implementation methods should not be understood as limiting the scope of protection of this embodiment. The scope of protection of this embodiment shall be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A method for preparing a positive electrode material intermediate, characterized in that: The following steps are involved: The raw materials containing the positive electrode active material are crystallized to form aluminum silicon phosphorus molecular sieve on the surface of the positive electrode active material to obtain the positive electrode material intermediate.

2. The method for preparing a cathode material intermediate according to claim 1, wherein: The crystallization treatment temperature is 160° C.-200° C., and the crystallization treatment time is 6-8 hours.

3. The method for preparing a cathode material intermediate according to claim 1, wherein: The raw materials include positive electrode active material, aluminum salt, phosphorus-containing compound, silicate, pure water and organic structure directing agent.

4. The method for preparing a cathode material intermediate according to claim 3, wherein: Calculated by mass ratio, the positive electrode active material: aluminum salt: phosphorus-containing compound: silicate: 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.

5. The method for preparing a cathode material intermediate according to claim 3 or 4, 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-containing oxides, phosphoric acid and phosphates; Or / and, the silicate is at least one of tetraethyl orthosilicate or ethyl silicate; Or / and, the organic structure directing agent is methyl pyrimidine.

6. The method for preparing a cathode material intermediate according to claim 5, wherein: 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 of 4-amino-2,2,6,6-tetramethylpiperidine and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine; Or / and, before crystallization, the raw materials are mixed according to the following steps: First, pure water and a phosphorus-containing compound are mixed, and then silicate, an organic structure-directing agent, and an aluminum salt are added and stirred to mix. After the silicate and the aluminum salt are hydrolyzed, the positive electrode active material is added and mixed evenly. or / and, continuously stirring the raw materials during the crystallization process; or / and, performing cooling, screening and drying operations after the crystallization treatment, wherein impurities mixed in the positive electrode material intermediate are removed by the screening.

7. The method for preparing a cathode material intermediate according to claim 6, wherein: During the crystallization process, the stirring rate of the raw materials is 5-15 rpm; or / and, the cooling rate after the crystallization treatment is 5-15°C / min; Or / and, the drying temperature is 50 ℃ -100 ℃, the drying time is 1-3h; or / and, after the crystallization treatment, sieving is performed using a sieve of 80-200 mesh.

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

9. The method for preparing the positive electrode material according to claim 8, wherein: The volume fraction of oxygen in the oxygen-containing atmosphere is 97%-100%, the sintering temperature is 150° C.-220° C., and the sintering time is 5-10 hours.

10. A positive electrode material, characterized in that: It is prepared using the preparation method according to any one of claims 8 to 9.

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