A preparation method for improving the storage and gas generation performance of ternary cathode materials

Abstract

This disclosure discloses a method for preparing a ternary cathode material with a coating layer, comprising the following steps: S1: mixing a ternary material precursor with a lithium source and pre-calcining to obtain a pre-calcined material; the pre-calcined material is then mixed again and calcined to obtain a primary ternary cathode material; S2: dissolving an additive T to obtain a solution U; mixing and washing the primary ternary cathode material with the solution U; and drying the solution to obtain a secondary ternary cathode material; S3: performing atomic layer deposition on the secondary ternary cathode material to obtain a ternary cathode material; wherein the additive T is composed of lithium-containing materials and sodium-containing materials; and the stirring Reynolds number during the washing process is 200–20000.

Description

Technical Field

[0001] This disclosure belongs to the field of lithium-ion battery technology, specifically relating to a preparation method for improving the storage and gas generation performance of ternary cathode materials. Background Technology

[0002] Ternary batteries, with their high energy density, long cycle life, environmental friendliness, and lack of memory effect, have rapidly gained market attention due to their superior overall performance. Ultra-high nickel ternary cathode materials have received widespread global attention due to their high energy density. During the preparation of ultra-high nickel ternary materials, to prevent the formation of divalent nickel and reduce lithium-nickel mixing, the lithium content is typically increased, resulting in an excess of lithium. This excess lithium content generates excessive residual lithium on the material surface during sintering, which can easily lead to gelation during battery fabrication, preventing proper coating. Even if a battery is successfully fabricated, residual lithium can react with the electrolyte during cycling, degrading the material's storage performance and even generating excessive gas, affecting battery safety.

[0003] Currently, water washing is commonly used to reduce residual lithium on the material surface, and the intensity of the water wash has a significant impact on the residual lithium content. Insufficient water washing intensity will not remove residual lithium, affecting battery safety performance; excessive water washing intensity will not only remove residual lithium from the surface but also wash out surface lattice lithium, and may even cause primary particles to detach, affecting battery capacity. During this process, residual lithium acts as a binder; if this binder is excessively removed, some primary particles on the material surface will also fail to adhere. Therefore, it is necessary to control the water washing intensity and improve the compactness between material particles to ensure effective washing.

[0004] Ultra-high nickel materials are extremely sensitive to water due to their high nickel content. During water washing, lattice lithium is easily washed out. Also due to the high nickel content, ultra-high nickel materials have an inherent disadvantage in terms of gas generation and storage performance compared to low-nickel materials. Summary of the Invention

[0005] This disclosure aims to at least address one of the technical problems existing in the prior art. To this end, this disclosure proposes a preparation method for improving the storage and gas generation performance of ternary cathode materials, which can optimize both storage and gas generation performance.

[0006] According to a first aspect of this disclosure, a method for preparing a ternary cathode material with a coating layer is proposed, comprising the following steps:

[0007] S1: The ternary material precursor is mixed with the lithium source and pre-calcined to obtain the pre-calcined material. The pre-calcined material is mixed again and then calcined to obtain the primary ternary cathode material.

[0008] S2: Dissolve additive T to obtain solution U, mix the primary ternary cathode material with solution U, wash, and dry to obtain secondary ternary cathode material;

[0009] S3: Perform atomic layer deposition on the secondary ternary cathode material to obtain the ternary cathode material;

[0010] The additive T is composed of lithium-containing materials and sodium-containing materials;

[0011] The stirring Reynolds number during the washing process is 200 to 20000.

[0012] The stirring Reynolds number is controlled by adjusting the size of the stirring paddle, the stirring speed, and the viscosity of the material. If the stirring Reynolds number is too low, the washing effect is poor, the residual lithium content is too high, and the material capacity is low. When the stirring Reynolds number is too high, the residual lithium content is too low, which will also aggravate the primary particle detachment phenomenon, leading to a decrease in material capacity. At the same time, the material structure is damaged, resulting in poor gas production performance.

[0013] In some embodiments, the stirring Reynolds number during the washing process is 3000 to 10000. Within this stirring Reynolds number range, the washing effect on the cathode material is superior.

[0014] In some embodiments, the molar ratio of the lithium-containing material to the sodium-containing material is 3 to 5:1. The presence of an appropriate amount of sodium during the washing process can effectively improve the gas-generating performance of the material; however, if the sodium content is too high, the material's capacity will decrease.

[0015] In some embodiments, the lithium-containing material is selected from at least one of lithium hydroxide, lithium carbonate, lithium acetate, or lithium chloride; and / or, the sodium-containing material is selected from at least one of sodium hydroxide, sodium carbonate, sodium acetate, sodium chloride, or sodium aluminate.

[0016] In some embodiments, the solution U is an aqueous solution of the additive T.

[0017] In some embodiments, in step S1, the chemical formula of the ternary cathode material precursor is Ni. x Co y Mn z (OH)2, where x≥0.9, y>0, z>0, x+y+z=1.

[0018] In some embodiments, in step S1, the re-mixing process involves cooling the pre-calcined material and then mixing it again. During the pre-calcination process, the moisture (crystallization water) in the lithium source is decomposed and carried away by the high temperature. After cooling and re-mixing, the pre-calcined material is repacked in a mortar, and no large amount of moisture is generated during calcination, resulting in a more compact material structure.

[0019] In some embodiments, in step S1, the pre-calcination temperature is 450–650°C, and the pre-calcination time is 5–20 hours. Under these pre-calcination conditions, the water of crystallization in the raw material can be removed relatively completely.

[0020] In some embodiments, in step S1, the calcination temperature is 700–850°C, and the calcination time is 5–20 h.

[0021] In some embodiments, the primary ternary cathode material has the chemical formula LiNi. x Co y Mn z O2, where x≥0.9, y>0, z>0, x+y+z=1.

[0022] In some embodiments, in step S1, the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium oxalate, lithium citrate, or lithium acetate.

[0023] In some embodiments, the molar ratio of the ternary cathode material precursor to lithium in the lithium source is 1:(1 to 1.15).

[0024] In some embodiments, in step S2, the molar concentration of solution U is 0.05–0.1 mol / L. The molar concentration refers to the total concentration of cations or anions contained in solution U. By controlling the cation concentration in the solution, not only can the excessive removal of residual alkali from the material surface be prevented during the washing process, but additives can also be coated onto the material surface, optimizing material storage and gas generation performance, and ensuring the washing effect.

[0025] In some embodiments, in step S2, the particle size Dv50 of the primary ternary cathode material is 8–10 μm. The particle size of the primary ternary cathode material affects the viscosity of the material during washing; the higher the particle size, the greater the viscosity of the material.

[0026] In some embodiments, in step S2, the solid-liquid ratio of the primary ternary cathode material to the solution U is 1–3 kg / L. The solid-liquid ratio of the primary ternary cathode material to the solution U affects the viscosity of the material during washing; within this range, the washing effect is better.

[0027] In some embodiments, the temperature of the solution U in step S2 is 2–25°C. If the solution temperature is too high, it will negatively affect the gas-generating performance of the material.

[0028] In some embodiments, in step S2, the stirring speed during washing is 20–2000 rpm. The stirring speed affects the stirring Reynolds number during the washing process. If the stirring speed is too low, the washing effect on the material is limited; if the stirring speed is too high, the residual alkali on the material surface will be excessively washed away, the capacity will decrease, and the surface structure of the material will also be damaged.

[0029] In some embodiments, in step S2, after the primary ternary cathode material is mixed and washed with the solution U, the primary ternary cathode material is further subjected to centrifugation. The centrifugation speed is 20-80 Hz, and the centrifugation atmosphere is nitrogen.

[0030] In some embodiments, in step S2, the drying temperature is 110–150°C, and the drying time is 3–8 hours.

[0031] In some embodiments, in step S2, the secondary ternary cathode material is further subjected to sieving, with the sieve mesh size being 200 mesh.

[0032] In some embodiments, step S3 involves the following steps: ALD (Atomic Layer Deposition) reagent is introduced into the secondary ternary cathode material under negative pressure, followed by the introduction of inert gas, followed by evacuation and the introduction of water vapor. This process is repeated 10-30 times after evacuation to obtain the ternary cathode material. The ALD reagent undergoes chemical adsorption on the material surface, and the subsequently introduced water vapor reacts with the ALD reagent to form a coating layer on the material surface. The thickness of the coating layer is controlled by the deposition time and number of deposition cycles.

[0033] In some embodiments, the coating thickness of the ternary cathode material is 1–10 nm. If the coating thickness is too low, the material may not be fully coated; if the coating thickness is too high, it will negatively affect the capacity of the material.

[0034] In some implementations, the negative pressure is a pressure below 10 Pa.

[0035] In some embodiments, the ALD reaction reagent is at least one selected from titanium tetrachloride, isopropyl titanate, silicon tetrachloride, trimethylaluminum, germanium tetrafluoride, tris(N,N'-diisopropylformamidinium)lanthanum, or tetra(dimethylamino)zirconium.

[0036] In some embodiments, the ALD reagent is trimethylaluminum. Using trimethylaluminum as the ALD reagent can be effective in improving the storage and gas generation properties of the material.

[0037] In some embodiments, the ALD reaction reagent is introduced for 2 to 5 seconds.

[0038] In some embodiments, the inert gas is introduced for approximately 120 seconds; the inert gas is argon.

[0039] In some embodiments, the water vapor is introduced for approximately 5 to 15 seconds.

[0040] In some embodiments, the temperature of the water vapor is 100–150°C.

[0041] In some embodiments, the atomic layer deposition process is carried out at a temperature of 100–150°C. A temperature within this range in the atomic layer deposition reaction chamber is conducive to the reaction of water vapor with the ALD reagent.

[0042] Using washed high-nickel ternary materials as ALD substrates, the washing process generates a spinel phase protective layer on the material surface, which protects the substrate from damage by water vapor during the ALD reaction. This allows the material to obtain a uniform metal oxide coating layer, reducing the material's specific surface area without structural damage.

[0043] According to a second aspect of this disclosure, a ternary cathode material is proposed, prepared by the method described in the first aspect of this disclosure. The ternary cathode material has a sodium content of 0.01%–0.2%, a sulfur content of <0.1%, and a residual lithium content of 0.15%–0.3% by mass. After washing in a sodium-containing solution, the ternary cathode material is coated with a small amount of sodium, which can reduce side reactions with the electrolyte during storage, thereby helping to improve the capacity retention and gas generation performance during storage. Since the ternary material precursor is prepared by co-precipitation of transition metal sulfates, excessive residual sulfur content will affect the material's capacity. Excessive residual lithium content leads to more severe side reactions during cycling; conversely, insufficient residual lithium content makes it easier for lattice lithium to be washed out during washing, resulting in a decrease in capacity.

[0044] According to a third aspect of this disclosure, a lithium-ion battery is proposed, comprising a ternary cathode material as described in a second aspect of this disclosure.

[0045] According to one embodiment of this disclosure, at least the following beneficial effects are achieved:

[0046] (1) This disclosure avoids the looseness of the material after the precursor and lithium source are dehydrated by pre-sintering, re-mixing and re-sintering the ternary material precursor, increases the contact area between the materials during the sintering process, makes the secondary spheres of the material more tightly bonded, improves the hardness of the material and improves the washing resistance of the material.

[0047] (2) This disclosure controls the degree of washing by controlling the Reynolds number during the washing process and thus the flow of the fluid. Controlling the washing intensity within a certain range reduces residual lithium to a suitable level, preventing over-washing that could lead to lithium deficiency or primary particle removal. Simultaneously, this disclosure adds lithium-containing and sodium-containing materials to the washing solution to inhibit excessive washing away of residual lithium from the material surface, while also coating the material surface with a small amount of sodium, thus optimizing the material's storage and gas generation performance. The high-nickel ternary cathode material prepared using the method described in this disclosure has a high capacity and is suitable for application in the lithium-ion battery field.

[0048] (3) This disclosure performs atomic layer deposition coating on the washed ternary cathode material to coat the material surface with a nanoscale oxide coating layer, thereby repairing the damage to the material surface caused by washing. Attached Figure Description

[0049] The present disclosure will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0050] Figure 1 This is a 10,000x magnified SEM image of the high-nickel ternary cathode material prepared in Example 1 of this disclosure;

[0051] Figure 2 This is a 10,000x magnified SEM image of the high-nickel ternary cathode material prepared in Comparative Example 1 of this disclosure;

[0052] Figure 3 This is a 10,000x magnified SEM image of the high-nickel ternary cathode material prepared in Comparative Example 2 of this disclosure.

[0053] Figure 4 The graphs show the gas production data of Examples 1-2 and Comparative Examples 2-3 of this disclosure at 70°C.

[0054] Figure 5 This is a diagram showing the storage data of Embodiments 1-2 and Comparative Examples 2-3 of this disclosure at 60°C. Detailed Implementation

[0055] The following will describe the concept and technical effects of this disclosure clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of this disclosure.

[0056] Example 1

[0057] A method for preparing a ternary cathode material includes the following steps:

[0058] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01(OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0059] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0060] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0061] (4) Take 4L of deionized water at 10℃, add 67.11g of lithium hydroxide monohydrate and 16.00g of sodium hydroxide to prepare solution U.

[0062] (5) Take solution U and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 150 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the stirring was carried out at a Reynolds number of 4000 for 2 minutes. After stirring, the mixture was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was placed in a vibrating dryer for drying at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the mixture was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0063] (6) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating. The SEM image of the high-nickel ternary cathode material C is shown below. Figure 1 As shown.

[0064] Example 2

[0065] A method for preparing a ternary cathode material includes the following steps:

[0066] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0067] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0068] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0069] (4) Take 5L of deionized water at 10℃, add 83.88g of lithium hydroxide monohydrate and 20.00g of sodium hydroxide to prepare solution U.

[0070] (5) Take solution U and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 150 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the mixture was stirred at a Reynolds number of 10,000 for 2 minutes. After stirring, it was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was dried in a vibrating dryer at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the material was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0071] (6) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating.

[0072] Comparative Example 1

[0073] A method for preparing a ternary cathode material differs from Example 1 only in that the sintering process of mixture A is different, and specifically includes the following steps:

[0074] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0075] (2) Mixture A was placed in a box furnace for sintering at a temperature of 530℃ / 8h + 710℃ / 10h in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0076] (3) Take 4L of deionized water at 10℃, add 67.11g of lithium hydroxide monohydrate and 16.00g of sodium hydroxide to prepare solution D1.

[0077] (4) Take solution D1 and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 150 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the stirring was carried out at a Reynolds number of 4000 for 2 minutes. After stirring, the mixture was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was placed in a vibrating dryer for drying at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the mixture was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0078] (5) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating. The SEM image of the high-nickel ternary cathode material C is shown below. Figure 2 As shown.

[0079] Comparative Example 2

[0080] A method for preparing a ternary cathode material differs from Example 1 only in the parameters of the washing process, and specifically includes the following steps:

[0081] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0082] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0083] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0084] (4) Take 5L of deionized water at 10℃, add 83.88g of lithium hydroxide monohydrate and 20.00g of sodium hydroxide to prepare solution D2.

[0085] (5) Take solution D2 and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 400 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi 0.92 Co 0.07 Mn 0.01O2 was added to the reactor, and the mixture was stirred at a Reynolds number of 50,000 for 2 minutes. After stirring, it was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was dried in a vibrating dryer at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the material was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0086] (6) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating. The SEM image of the high-nickel ternary cathode material C is shown below. Figure 3 As shown.

[0087] Comparative Example 3

[0088] A method for preparing a ternary cathode material, differing from Example 1 only in that the amount of lithium hydroxide monohydrate added in step (4) is different and sodium hydroxide is not added, specifically including the following steps:

[0089] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0090] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0091] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0092] (4) Take 4L of deionized water at 10℃ and add 83.88g of lithium hydroxide monohydrate to prepare solution D3.

[0093] (5) Take solution D3 and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 150 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the stirring was carried out at a Reynolds number of 4000 for 2 minutes. After stirring, the mixture was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was placed in a vibrating dryer for drying at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the mixture was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0094] (6) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating.

[0095] Comparative Example 4

[0096] A method for preparing a ternary cathode material, differing from Example 1 only in the amount of sodium hydroxide added and the absence of lithium hydroxide monohydrate, specifically includes the following steps:

[0097] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0098] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0099] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0100] (4) Take 4L of deionized water at 10℃, add 80.00g of sodium hydroxide, and prepare solution D4.

[0101] (5) Take solution D4 and place it in a water washing vessel with a stirring paddle diameter of 16 cm. Stir at 150 rpm for 10 min. Then add 10 kg of ternary cathode material LiNi 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the stirring was carried out at a Reynolds number of 4000 for 2 minutes. After stirring, the mixture was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was placed in a vibrating dryer for drying at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the mixture was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0102] (6) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating.

[0103] Comparative Example 5

[0104] A method for preparing a ternary cathode material, differing from Example 1 only in that lithium hydroxide monohydrate and sodium hydroxide are not added in step (4), specifically including the following steps:

[0105] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01 (OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0106] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0107] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0108] (4) Take 4L of deionized water at 10℃ and place it in a water washing vessel with a stirring paddle diameter of 16cm. Stir at 150rpm for 10min. Then add 10kg of ternary cathode material LiNi 0.92 Co 0.07 Mn 0.01 O2 was added to the reactor, and the stirring was carried out at a Reynolds number of 4000 for 2 minutes. After stirring, the mixture was placed in a centrifuge and centrifuged at 50 Hz for 50 minutes. Then, it was placed in a vibrating dryer for drying at 150°C for 3 hours with a vibration frequency of 50 Hz. After drying, the mixture was sieved through a 200-mesh sieve to obtain high-nickel ternary cathode material B.

[0109] (5) Place the high-nickel ternary material B into the ALD reaction chamber, evacuate the reaction chamber, and wait until the pressure drops below 10 Pa. Open the valve of the container containing trimethylaluminum, introduce trimethylaluminum vapor into the reaction chamber, and maintain this for 3 seconds. The temperature of the reaction chamber is 120°C. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted trimethylaluminum. When the pressure in the reaction chamber drops to 10 Pa, open the valve of the container containing water, introduce water vapor into the reaction chamber, and maintain this for 10 seconds. Introduce argon gas into the reaction chamber for 120 seconds, then evacuate to remove unreacted water vapor. Repeat the above cycle 20 times to obtain the high-nickel ternary cathode material C with a nanoscale alumina coating.

[0110] Comparative Example 6

[0111] A method for preparing a ternary cathode material, differing from Example 1 only in that washing and atomic layer deposition are not performed, specifically includes the following steps:

[0112] (1) Take 11.100 kg of nickel-cobalt-manganese hydroxide precursor Ni 0.92 Co 0.07 Mn 0.01(OH)2 and 5.059 kg of coarse lithium hydroxide particles (Dv50 range of 200-350 μm) were mixed once in a high-speed mixer with mixing parameters of 150 rpm and 15 min to obtain mixture A.

[0113] (2) The mixture A was placed in a box furnace for pre-sintering at a temperature of 530°C for 8 hours in an oxygen atmosphere to obtain pre-sintered material A.

[0114] (3) Pour the pre-calcined material A into a high-efficiency mixer and mix at 300 rpm for 15 minutes. After mixing, place it in a box furnace for sintering at 710℃ for 10 hours in an oxygen atmosphere to obtain the ternary cathode material LiNi. 0.92 Co 0.07 Mn 0.01 O2.

[0115] Test case

[0116] The embodiments and comparative examples of this disclosure were tested for Na content, S content, residual lithium, charge / discharge capacity, and first-cycle coulombic efficiency. Na and S content were tested using ICP-based analysis, with elemental wavelengths of 589.592 nm for Na and 180.669 nm for S. Residual lithium content in LiOH and Li₂CO₃ was tested using potentiometric titration. Charge capacity, discharge capacity, and first-cycle efficiency were tested using a constant current charge / discharge method with a current density of 0.1 C and a cutoff voltage of 2.8–4.3 V. The test results are shown in Table 1.

[0117] Table 1

[0118]

[0119] It can be seen that Comparative Example 1, without the pre-calcination process, had lower residual lithium and lower capacity after washing compared to Example 1 under the same experimental conditions. Comparative Example 2, with increased stirring speed and a greater degree of washing, showed a significant decrease in both lithium carbonate and LiOH compared to the Example, resulting in lower capacity. Comparative Example 3, using only lithium hydroxide while maintaining the same hydroxide concentration, lacked sodium ions in the washing solution, leading to poor gas production and storage performance. Comparative Example 4, using only sodium hydroxide while maintaining the same hydroxide concentration, lacked lithium ions in the washing solution, resulting in more significant lithium removal from the material surface, significantly lower residual lithium compared to the Example, and decreased capacity. Comparative Example 5, using pure water for washing, made it easier to wash away alkaline substances and lithium from the material surface, severely damaging the material surface structure and significantly reducing both residual lithium and capacity. Comparative Example 6, omitting the washing step, resulted in a product with higher LiOH and residual lithium content and lower capacity.

[0120] SEM tests were performed on the high-nickel cathode materials prepared in the embodiments and comparative examples of this disclosure. The test results are as follows: Figures 1-3 As shown. By Figure 1 It can be seen that the cathode material particles prepared in Example 1 showed no cracking and no primary particle detachment; Figure 2 It can be seen that the high-nickel cathode material prepared in Comparative Example 1 exhibits small particle disintegration under high stirring speed, with obvious primary particle detachment. This may be due to the lack of a pre-calcination process, resulting in weaker bonding of the secondary particles, making them prone to disintegration during washing. Figure 3 It can be seen that the pre-calcined high-nickel cathode material can still maintain its structural integrity under a washing process with a high Reynolds number, with only a small number of primary particles coming off, indicating that the sample using the pre-calcination process can indeed enhance the structural stability of the secondary spheres.

[0121] Gas production tests were conducted on the embodiments and comparative examples of this disclosure at 70°C using a flexible packaging system. The test results are as follows: Figure 4 As shown in the figures, the experimental results indicate that Example 1 exhibited the best gas production, followed by Example 2, demonstrating that washing with lithium hydroxide and sodium hydroxide solutions can reduce the gas production of the material. Furthermore, controlling the Reynolds number at a lower level can further reduce gas production. The gas production of Comparative Example 2 was significantly higher than other samples after 20 days, indicating that even with only a small amount of primary particles being released, the gas production still increased significantly, proving that washing processes with higher Reynolds numbers can damage the material structure, leading to excessive gas production during high-temperature storage. The gas production of Comparative Example 3 shows that the absence of sodium hydroxide in the washing solution worsens the gas production performance of the material. This may be because the presence of sodium hydroxide in the washing solution coats the material surface with sodium, which may reduce side reactions between the material and the electrolyte under high-temperature conditions, thereby reducing gas production.

[0122] The embodiments and comparative examples of this disclosure were subjected to a soft-pack storage test at 60°C, and the test results are as follows: Figure 5 As shown in the figure. Similar to the gas production results, the storage performance of the examples is significantly better, indicating that the washing process using a lithium hydroxide-sodium hydroxide mixed solution and controlling the Reynolds number is beneficial to the storage performance of the material. The storage performance of Comparative Example 2 is significantly worse, possibly because the partial release of small particles leads to increased porosity on the material surface, resulting in faster capacity decay during storage. Comparative Example 3 shows that the lack of sodium ions on the material surface deteriorates the storage performance, indicating that the presence of sodium ions is helpful for the material's storage performance.

Claims

1. A method for preparing a ternary cathode material with a coating layer, characterized in that, The method comprises the following steps: S1: mixing a ternary material precursor with a lithium source for pre-burning to obtain a pre-burnt material, mixing the pre-burnt material again for calcination to obtain a primary ternary positive electrode material; S2: dissolving an additive T to obtain a solution U, mixing the primary ternary positive electrode material with the solution U for washing, and drying to obtain a secondary ternary positive electrode material; S3: performing atomic layer deposition treatment on the secondary ternary positive electrode material to obtain a ternary positive electrode material; In step S1, the chemical formula of the ternary material precursor is Ni x Co y Mn z (OH)2, wherein x≥0.9, y>0, z>0, x+y+z=1; the re-mixing process is that the pre-sintered material is cooled and then mixed again. In step S2, the additive T is composed of a lithium-containing material and a sodium-containing material; the lithium-containing material is at least one selected from lithium hydroxide, lithium carbonate, lithium acetate or lithium chloride; the sodium-containing material is at least one selected from sodium hydroxide, sodium carbonate, sodium acetate, sodium chloride or sodium metaaluminate; the molar ratio of the lithium-containing material to the sodium-containing material is 3-5:1; The solution U has a concentration of 0.05-0.1 mol / L; The Reynolds number of stirring in the washing process is 3000-10000.

2. The production method according to claim 1, characterized by, In step S2, the particle size Dv50 of the primary ternary positive electrode material is 8-10 μm.

3. The preparation method according to claim 1, characterized in that, In step S2, the solid-liquid ratio of the primary ternary positive electrode material to the solution U is 1-3 kg / L.

4. The method of claim 1, wherein, In step S2, the temperature of the solution U is 2-25℃.

5. The preparation method according to claim 1, characterized in that, In step S2, the stirring speed of the washing is 20-2000 rpm.

6. The method of claim 1, wherein, In step S3, the process of the atomic layer deposition treatment is as follows: under negative pressure, ALD reaction reagents are introduced into the secondary ternary positive electrode material, followed by introduction of inert gas, vacuum extraction, introduction of water vapor, again introduction of inert gas, re-extraction of vacuum, and repetition of the above steps for 10-30 times to obtain the ternary positive electrode material.

7. The preparation method according to claim 6, characterized in that, The ALD reaction reagents are at least one selected from titanium tetrachloride, isopropyl titanate, silicon tetrachloride, trimethylaluminum, germanium tetrafluoride, tris(N,N'-diisopropylformamidinato) lanthanum or tetrakis(dimethylamino) zirconium.

8. The preparation method according to claim 6, characterized in that, The time for introducing the ALD reaction reagents is 2-5 s.

9. The preparation method according to claim 6, characterized in that, The time for introducing the water vapor is 5-15 s.

10. The preparation method according to claim 6, characterized in that, The temperature of the atomic layer deposition treatment is 100-150℃.

11. A ternary cathode material prepared by the method of any one of claims 1-10, characterized in that, The sodium content of the ternary positive electrode material is 0.01%-0.2%, the sulfur content is <0.1%, and the mass content of residual lithium is 0.15%-0.3%.

12. A lithium-ion battery, characterized by, The ternary positive electrode material as claimed in claim 11.

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