High-voltage lithium cobalt oxide positive electrode material, preparation method, positive plate and lithium ion battery

Abstract

The invention provides a high-voltage lithium cobalt oxide positive electrode material, a preparation method, a positive plate and a lithium ion battery. The preparation method comprises the following steps: mixing a cobalt source, a lithium source and an additive, and performing solid-phase sintering to prepare the high-voltage lithium cobalt oxide positive electrode material, the additive comprises a transition metal organic compound. In the preparation process of the high-voltage lithium cobalt oxide positive electrode material, the transition metal organic compound is added as an additive, so that the convective reaction effect of the raw material powder in the solid-phase sintering process is enhanced, and the phenomenon that residual lithium carbonate is randomly retained due to insufficient reaction of the raw materials is avoided; the problem that residual lithium in a local area of the surface of the prepared high-voltage lithium cobalt oxide positive electrode material is enriched to cause black spots is solved, and the uniformity and the electrochemical performance of the high-voltage lithium cobalt oxide positive electrode material are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to lithium-ion batteries, and more particularly to a high-voltage lithium cobalt oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery. Background Technology

[0002] Lithium cobalt oxide is currently recognized as one of the materials with high energy density and high volumetric density, and is widely used in 3C electronic products and other fields. In recent years, in order to further explore the energy density of lithium cobalt oxide, developing lithium cobalt oxide materials with higher voltage has become a research direction in the industry.

[0003] Currently, during the sintering process of high-voltage lithium cobalt oxide materials at 4.5V and above, there are localized black spots in blocky or sheet-like areas on the surface of the sintered material. The residual alkali content in the black spot areas is at least 0.02wt% higher than that in the non-black spot areas. This is attributed to the local enrichment of residual lithium caused by insufficient chemical reaction, which results in some raw materials not reacting fully.

[0004] CN118993161A discloses a lithium cobalt oxide production process. By doping barium oxide into the lithium cobalt oxide raw material, the properties of barium oxide are utilized to remove moisture and carbon dioxide from the material during a single sintering process. Furthermore, barium oxide reacts with oxygen to form barium peroxide, achieving oxygen storage. At temperatures above 600℃, barium peroxide gradually releases oxygen, promoting the formation of lithium cobalt oxide during the sintering reaction. In the potting process, holes are punched in each cell to ensure sufficient contact between the material and air, resulting in a more complete reaction and reducing the residual alkali content in the lithium cobalt oxide product.

[0005] CN114180641A discloses a method for preparing high-rate lithium cobalt oxide, which uses phosphate to modify the surface of material particles. The phosphate forms a coating layer on the particle surface, which improves the conductivity and can also form a complex with residual lithium. On the one hand, it neutralizes the residual lithium on the material surface and reduces the residual alkali content on the material surface; on the other hand, it isolates the active particles from direct contact with the electrolyte, thereby improving the safety performance of the full battery.

[0006] CN116093298A discloses a method for microwave sintering to synthesize lithium cobalt oxide cathode materials. This microwave sintering method can reduce residual alkali on the cathode surface, improve cycle performance and capacity, and simultaneously coat the core layer with an aluminum-containing shell, effectively suppressing segregation when the shell contains aluminum. Furthermore, this invention also provides a cathode material, its preparation method, and a battery.

[0007] Therefore, it is of great significance to provide a preparation method that can promote the full reaction of high-voltage lithium cobalt oxide raw materials and reduce residual lithium on the material surface. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a high-voltage lithium cobalt oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery. This invention enhances the convection reaction effect of the raw material powder during solid-state sintering by adding a transition metal organometallic compound as an additive during the preparation of the high-voltage lithium cobalt oxide cathode material. This avoids the problem of residual lithium carbonate randomly remaining due to insufficient raw material reaction, leading to localized lithium enrichment on the surface of the prepared high-voltage lithium cobalt oxide cathode material and the formation of black spots. This effectively improves the uniformity and electrochemical performance of the high-voltage lithium cobalt oxide cathode material.

[0009] To achieve this objective, the present invention employs the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a high-voltage lithium cobalt oxide cathode material, the method comprising:

[0011] The high-voltage lithium cobalt oxide cathode material is prepared by mixing a cobalt source, a lithium source, and additives, followed by solid-state sintering; the additives include organometallic transition metal compounds.

[0012] This invention adds a transition metal organometallic compound during the mixing process of high-voltage lithium cobalt oxide cathode materials. During solid-state sintering, the transition metal organometallic compound decomposes to generate continuously convecting high-temperature CO2 gas, which enhances the convective reaction effect of the raw material powder during solid-state sintering. This allows the lithium source and cobalt source to fully contact and react chemically in a "micro-boiling" environment, avoiding the problem of residual lithium carbonate randomly remaining and causing regional lithium accumulation and black spots on the surface of the prepared high-voltage lithium cobalt oxide cathode material due to insufficient reaction of raw materials during static reaction. This effectively improves the uniformity of the high-voltage lithium cobalt oxide cathode material, thereby enhancing its electrochemical performance.

[0013] In this invention, the transition metal component in the organometallic transition metal compound can also be used as a dopant to perform in-situ bulk phase doping of the high-voltage cathode material during solid-state sintering. Compared with traditional metal oxide dopants, it can form strong covalent bonds with the lattice oxygen in lithium cobalt oxide during sintering, thereby improving the structural stability of the high-voltage lithium cobalt oxide cathode material and mitigating the problem of its structure easily collapsing during delithiation under high voltage conditions.

[0014] Preferably, the additive comprises any one or a combination of at least two of magnesium stearate, aluminum stearate, or titanium stearate.

[0015] Preferably, the mass of the additive is 1 wt% to 12 wt% of the total mass of the cobalt source and the lithium source.

[0016] Preferably, the molar ratio of cobalt in the cobalt source to lithium in the lithium source is 1:(1.06~1.1).

[0017] Preferably, the cobalt content in the cobalt source is above 73 wt%.

[0018] Preferably, the median particle size of the cobalt source is below 20 μm, and more preferably 2 μm to 10 μm.

[0019] Preferably, the cobalt source includes cobalt tetroxide, cobalt carbonate, or cobalt hydroxide, with cobalt tetroxide being the most preferred.

[0020] Preferably, the purity of the lithium source is above 95 wt%.

[0021] Preferably, the median particle size of the lithium source is 3μm to 40μm.

[0022] Preferably, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium acetate, or lithium nitrate, with lithium carbonate being the most preferred.

[0023] Preferably, the solid-state sintering includes a first stage of sintering and a second stage of sintering.

[0024] Preferably, the solid-phase sintering is carried out in an oxygen-containing atmosphere.

[0025] Preferably, the oxygen-containing atmosphere includes air or a mixture of oxygen with an oxygen content of 60 vol% or more and an inert atmosphere, wherein the inert atmosphere includes nitrogen and / or an inert gas.

[0026] Preferably, the sintering temperature of the first stage is 700℃~800℃.

[0027] Preferably, the sintering time of the first stage is 1 hour to 3 hours.

[0028] Preferably, the sintering temperature of the second stage is 1000℃~1100℃.

[0029] Preferably, the sintering time for the second stage is 7h to 15h.

[0030] Preferably, after solid-phase sintering, the high-voltage lithium cobalt oxide cathode material is further pulverized and sieved.

[0031] Preferably, the sieving uses a 300-500 mesh sieve.

[0032] In a second aspect, the present invention provides a high-voltage lithium cobalt oxide cathode material, which is prepared by the preparation method described in the first aspect.

[0033] The high-voltage lithium cobalt oxide material provided by this invention has a low residual lithium content on its surface and exhibits good electrochemical performance in high-voltage application scenarios above 4.5V.

[0034] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the high-voltage lithium cobalt oxide positive electrode material as described in the second aspect.

[0035] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode as described in the third aspect.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) By adding transition metal organometallic compounds as additives during the preparation of high-voltage lithium cobalt oxide cathode materials, the present invention enhances the convection reaction effect of raw material powder during solid-state sintering, avoids the problem of excessive residual lithium on the surface of the prepared high-voltage lithium cobalt oxide cathode material due to insufficient raw material reaction and random retention of residual lithium carbonate, and effectively improves the electrochemical performance of high-voltage lithium cobalt oxide.

[0038] (2) The high-voltage lithium cobalt oxide material provided by the present invention has a low residual lithium content on the surface and exhibits good electrochemical performance in high-voltage application scenarios above 4.5V. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having” and any variations thereof in this invention are intended to cover non-exclusive inclusion.

[0041] In the description of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0042] In one specific embodiment, the present invention provides a method for preparing a high-voltage lithium cobalt oxide cathode material, the method comprising:

[0043] The high-voltage lithium cobalt oxide cathode material is prepared by mixing a cobalt source, a lithium source, and additives, followed by solid-state sintering; the additives include organometallic transition metal compounds.

[0044] This invention adds a transition metal organometallic compound during the mixing process of high-voltage lithium cobalt oxide cathode materials. During solid-state sintering, the transition metal organometallic compound decomposes to generate continuously convecting high-temperature CO2 gas, which enhances the convective reaction effect of the raw material powder during solid-state sintering. This allows the lithium source and cobalt source to fully contact and react chemically in a "micro-boiling" environment, avoiding the problem of residual lithium carbonate randomly remaining and causing regional lithium residue enrichment and black spots on the surface of the prepared high-voltage lithium cobalt oxide cathode material due to insufficient reaction of raw materials during static reaction. This effectively improves the electrochemical performance of high-voltage lithium cobalt oxide.

[0045] In this invention, the transition metal component in the organometallic transition metal compound can also be used as a dopant to perform in-situ bulk phase doping of the high-voltage cathode material during solid-state sintering. Compared with traditional metal oxide dopants, it can form strong covalent bonds with the lattice oxygen in lithium cobalt oxide during sintering, thereby improving the structural stability of the high-voltage lithium cobalt oxide cathode material and mitigating the problem of its structure easily collapsing during delithiation under high voltage conditions.

[0046] In some embodiments, the additive includes any one or a combination of at least two of magnesium stearate, aluminum stearate, or titanium stearate.

[0047] In this invention, stearic acid-based transition metal organometallic compounds are selected. In addition to the organic components being able to decompose and create a "micro-boiling" environment during solid-state sintering, thus enhancing the convection reaction effect of the raw material powder during solid-state sintering, stearic acid-based transition metal organometallic compounds can also improve the flowability of raw material powders such as cobalt and lithium sources during the mixing process and their compressibility before sintering, thereby reducing the contact angle of the prepared high-voltage lithium cobalt oxide cathode material and increasing the yield of lithium cobalt oxide.

[0048] In some embodiments, the mass of the additive is 1 wt% to 12 wt% of the total mass of the cobalt source and the lithium source, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, or 12 wt%, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0049] In some embodiments, the molar ratio of cobalt in the cobalt source to lithium in the lithium source is 1:(1.06 to 1.1), for example, it can be 1:1.06, 1:1.07, 1:1.08, 1:1.09 or 1:1.1, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0050] In some embodiments, the cobalt content in the cobalt source is above 73 wt%, for example, it may be 73.1 wt%, 73.2 wt%, 73.3 wt%, or 73.4 wt%, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0051] In some embodiments, the median particle size of the cobalt source is below 20 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm or 20 μm, including but not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2 μm to 10 μm.

[0052] In some embodiments, the cobalt source includes cobalt tetroxide, cobalt carbonate, or cobalt hydroxide, preferably cobalt tetroxide.

[0053] In some embodiments, the purity of the lithium source is above 95 wt%, for example, it may be 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, or 98 wt%, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0054] In some embodiments, the median particle size of the lithium source is 3μm to 40μm, for example, it can be 3μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm or 40μm, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0055] In some embodiments, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium acetate, or lithium nitrate. Typical but non-limiting combinations include a combination of lithium carbonate and lithium hydroxide, or a combination of lithium acetate and lithium nitrate, with lithium carbonate being preferred.

[0056] In some embodiments, the solid-state sintering includes a first stage sintering and a second stage sintering.

[0057] In this invention, solid-state sintering is divided into two stages. The first stage of sintering is performed, followed by a second stage of sintering with increased temperature. The purpose of the first stage of sintering is to melt the lithium source and allow the transition metal-organic compound to boil, creating a "micro-boiling" environment for the mixed raw materials. This provides the necessary convective conditions for a full chemical reaction. The second stage of sintering further allows any unreacted lithium salt from the first stage to react completely, optimizing the crystal structure of lithium cobalt oxide, increasing its orderliness, and providing a driving force for the doping of the metal obtained from the decomposition of the transition metal-organic compound into the lithium cobalt oxide crystal, ensuring that the doping level reaches the designed content. The temperature of the second stage of sintering should not be too high; otherwise, the sintered product will severely clump together, making it difficult to crush and sieve, thus hindering its application.

[0058] In some embodiments, the solid-state sintering is carried out in an oxygen-containing atmosphere.

[0059] In some embodiments, the oxygen-containing atmosphere comprises air or a mixture of oxygen with an oxygen content of 60 vol% or more and an inert atmosphere, wherein the inert atmosphere comprises nitrogen and / or an inert gas. The oxygen content in the mixture of oxygen and the inert atmosphere can be, for example, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, 95 vol%, or 100 vol%, including but not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0060] In some embodiments, the sintering temperature of the first stage is 700℃ to 800℃, for example, it can be 700℃, 720℃, 740℃, 760℃, 780℃ or 800℃, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the sintering time of the first stage is 1h to 3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] In some embodiments, the sintering temperature of the second stage is 1000℃ to 1100℃, for example, it can be 1000℃, 1020℃, 1040℃, 1060℃, 1080℃ or 1100℃, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the second sintering time is 7h to 15h, for example, it can be 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, after solid-state sintering, the high-voltage lithium cobalt oxide cathode material is further pulverized and sieved.

[0065] In some embodiments, the sieving uses a 300-500 mesh screen, for example, the screen can be 300 mesh, 350 mesh, 400 mesh, 450 mesh or 500 mesh, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0066] In another specific embodiment, the present invention provides a high-voltage lithium cobalt oxide cathode material, which is prepared by the preparation method described in one of the foregoing specific embodiments.

[0067] In yet another embodiment, the present invention provides a positive electrode sheet comprising a high-voltage lithium cobalt oxide positive electrode material as described in another preceding embodiment.

[0068] The high-voltage lithium cobalt oxide material provided by this invention has a low residual lithium content on its surface and exhibits good electrochemical performance in high-voltage application scenarios above 4.5V.

[0069] In yet another embodiment, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode sheet described in yet another embodiment above.

[0070] Example 1

[0071] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material, the method comprising:

[0072] Cobalt tetroxide with a cobalt content of 73.4 wt% and a median particle size of 5 μm, and lithium carbonate with a purity of 97 wt% and a median particle size of 6 μm are provided. Cobalt tetroxide and lithium carbonate are mixed at a Co:Li molar ratio of 1:1.08, and aluminum stearate (3 wt% of the total mass of cobalt tetroxide and lithium carbonate) is added as an additive. After being uniformly mixed by solid-phase dry mixing in a high-speed mixer, the mixture is sintered at 750°C for 2 hours in an air atmosphere in a roller kiln, and then the temperature is further increased to 1050°C for sintering for 12 hours. After pulverization and sieving through a 400-mesh sieve, the high-voltage lithium cobalt oxide cathode material is obtained.

[0073] Example 2

[0074] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material, the method comprising:

[0075] Cobalt hydroxide with a cobalt content of 73.6 wt% and a median particle size of 2 μm, and lithium nitrate with a purity of 95 wt% and a median particle size of 3 μm are provided. Cobalt hydroxide and lithium nitrate are mixed at a Co:Li molar ratio of 1:1.06, and magnesium stearate of 1 wt% of the total mass of cobalt hydroxide and lithium nitrate is added as an additive. After being uniformly mixed by solid-phase dry mixing in a high-speed mixer, the mixture is sintered at 700°C for 1 hour in a roller kiln under a mixed atmosphere of 60% vol oxygen and 40% vol nitrogen, and then the temperature is further increased to 1000°C for sintering for 7 hours. After pulverization and sieving through a 400-mesh sieve, the high-voltage lithium cobalt oxide cathode material is obtained.

[0076] Example 3

[0077] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material, the method comprising:

[0078] Cobalt tetroxide with a cobalt content of 73.3 wt% and a median particle size of 17 μm, and lithium carbonate with a purity of 99.5 wt% and a median particle size of 7 μm are provided. Cobalt tetroxide and lithium carbonate are mixed at a Co:Li molar ratio of 1:1.10, and titanium stearate of 12 wt% of the total mass of cobalt tetroxide and lithium carbonate is added as an additive. After being uniformly mixed by solid-phase dry mixing in a high-speed mixer, the mixture is sintered at 800°C for 3 hours in an air atmosphere in a roller kiln, and then the temperature is further increased to 1100°C for sintering for 15 hours. After pulverization and sieving through a 400-mesh sieve, the high-voltage lithium cobalt oxide cathode material is obtained.

[0079] Example 4

[0080] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. The preparation method is the same as in Example 1, except that the amount of aluminum stearate added is 0.5 wt% of the total mass of cobalt tetroxide and lithium carbonate.

[0081] Example 5

[0082] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. The preparation method is the same as in Example 1, except that the amount of aluminum stearate added is 15 wt% of the total mass of cobalt tetroxide and lithium carbonate.

[0083] Example 6

[0084] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the median particle size of cobalt tetroxide being 25 μm, the preparation method is the same as in Example 1.

[0085] Example 7

[0086] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the first sintering temperature of 600°C, the preparation method is the same as that in Example 1.

[0087] Example 8

[0088] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the first sintering temperature of 900°C, the preparation method is the same as that in Example 1.

[0089] Example 9

[0090] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the second-stage sintering temperature of 900°C, the preparation method is the same as that in Example 1.

[0091] Example 10

[0092] This embodiment provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the second-stage sintering temperature of 1200℃, the preparation method is the same as that in Example 1.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the absence of aluminum stearate during the mixing of lithium and cobalt sources, the preparation method is the same as in Example 1.

[0095] Comparative Example 2

[0096] This comparative example provides a method for preparing a high-voltage lithium cobalt oxide cathode material. Except for the use of an equimolar amount of aluminum oxide to replace aluminum stearate during the mixing of lithium and cobalt sources, the preparation method is the same as in Example 1.

[0097] Performance testing:

[0098] The yield of high-voltage lithium cobalt oxide cathode material in all the above examples and comparative examples was statistically analyzed. Yield = (actual weight of lithium cobalt oxide after sintering, crushing and sieving) ÷ theoretical weight of lithium cobalt oxide after chemical reaction sintering. The theoretical weight of lithium cobalt oxide after chemical reaction sintering was calculated based on the amount of lithium source and cobalt source participating in the reaction. The statistical results are shown in Table 1.

[0099] After solid-state sintering of the high-voltage lithium cobalt oxide cathode materials provided in all the above embodiments and comparative examples, the number of black spots formed by residual lithium enrichment per unit area (330mm*330mm) was counted, and the residual lithium content in the black spot area and the non-black spot area was tested. The test results are shown in Table 1.

[0100] Table 1

[0101]

[0102] Based on the test results of Examples 1 to 3 and Comparative Example 1 in Table 1, the present invention enhances the convection reaction effect of the raw material powder during solid-state sintering by adding a transition metal organometallic compound as an additive during the preparation of high-voltage lithium cobalt oxide cathode material. This avoids the problem of excessive residual lithium on the surface of the prepared high-voltage lithium cobalt oxide cathode material due to insufficient raw material reaction and random retention of residual lithium carbonate, thus effectively improving the electrochemical performance of high-voltage lithium cobalt oxide.

[0103] According to the test results of Example 1 and Comparative Example 2, if the aluminum stearate is replaced with a traditional alumina additive, no organic components decompose during the solid-state sintering process. Therefore, it is impossible to create a "micro-boiling" environment to enhance the convection reaction effect of the raw material powder during the solid-state sintering process. As a result, cobalt tetroxide and lithium carbonate cannot fully contact and react chemically, resulting in a lot of residual lithium enrichment on the surface of the prepared high-voltage cathode material, which leads to black spots and deterioration of electrochemical performance.

[0104] Based on the test results of Examples 1, 4, and 5, the amount of transition metal organometallic compound added affects the "micro-boiling" effect, convection effect, and completeness of the chemical reaction. If the amount added is too small, the amount of high-temperature CO2 gas formed by the decomposition of organic components will be small and the duration will be short. The convection reaction effect of the raw material powder during solid-state sintering will not be ideal, resulting in a small amount of residual lithium accumulating on the surface of the high-voltage lithium cobalt oxide cathode material, producing black spots. If the amount added is too large, the actual yield of the active material lithium cobalt oxide will decrease.

[0105] According to the test results of Examples 1 and 6, if the median particle size of cobalt tetroxide is too large, there will be too many large cobalt particles in the mixed raw materials, resulting in low lithiation reaction activity and incomplete reaction.

[0106] Based on the test results of Examples 1, 7, and 8, the temperature of the first sintering stage affects the "micro-boiling" effect, convection effect, and completeness of the chemical reaction. If the temperature is too high, exceeding the melting point of lithium salt, a large amount of lithium salt will evaporate rapidly before it begins to participate in the chemical reaction, causing an imbalance in the stoichiometry of the prepared lithium cobalt oxide material and reducing its charging tolerance under high voltage conditions. If the temperature is too low, the lithium salt cannot reach the molten state, resulting in poor convection effect between lithium salt and additives, reduced reaction uniformity, and the appearance of residual lithium enrichment areas, leading to a large number of black spots after sintering.

[0107] Based on the test results of Examples 1, 9, and 10, during the second sintering process, the lithium salt that did not react completely after the first sintering continues to react, while simultaneously driving the metal elements in the additives to be incorporated into the lithium cobalt oxide crystal. If the temperature is too high, although the reaction proceeds completely, it will lead to severe caking of the sintered material, making it difficult to crush and sieve, thus preventing its application. If the temperature is too low, the lithium salt that did not react completely after the first sintering will still not be able to react further during the second sintering process, resulting in a doping amount lower than the designed content and poor orderliness of the lithium cobalt oxide crystal structure.

[0108] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-voltage lithium cobalt oxide cathode material, characterized in that, The preparation method includes: The high-voltage lithium cobalt oxide cathode material was prepared by mixing a cobalt source, a lithium source, and additives and then solid-state sintering. The additives include organometallic transition metal compounds.

2. The preparation method according to claim 1, characterized in that, The additives include any one or a combination of at least two of magnesium stearate, aluminum stearate, or titanium stearate.

3. The preparation method according to claim 1, characterized in that, The mass of the additive is 1 wt% to 12 wt% of the total mass of the cobalt source and the lithium source; And / or, the molar ratio of cobalt in the cobalt source to lithium in the lithium source is 1:(1.06 to 1.1).

4. The preparation method according to claim 1, characterized in that, The cobalt source contains more than 73 wt% cobalt. And / or, the median particle size of the cobalt source is below 20 μm.

5. The preparation method according to claim 1, characterized in that, The purity of the lithium source is above 95 wt%; And / or, the median particle size of the lithium source is 3 μm to 40 μm.

6. The preparation method according to claim 1, characterized in that, The solid-state sintering includes a first-stage sintering and a second-stage sintering; And / or, the solid-phase sintering is carried out in an oxygen-containing atmosphere.

7. The preparation method according to claim 6, characterized in that, The sintering temperature of the first stage is 700℃~800℃; And / or, the sintering time of the first stage is 1h to 3h; And / or, the sintering temperature of the second stage is 1000℃~1100℃; And / or, the sintering time for the second stage is 7h to 15h; And / or, after solid-phase sintering, the high-voltage lithium cobalt oxide cathode material is further pulverized and sieved.

8. A high-voltage lithium cobalt oxide cathode material, characterized in that, The high-voltage lithium cobalt oxide cathode material is prepared by the preparation method described in any one of claims 1 to 7.

9. A positive electrode plate, characterized in that, The positive electrode includes the high-voltage lithium cobalt oxide positive electrode material as described in claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode as described in claim 9.

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