Lithium cobalt oxide film positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to a lithium cobalt oxide film positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing cobalt source powder and lithium source powder to obtain mixed powder, and carrying out cold pressing sintering on the mixed powder to obtain a target material; the cold pressing sintering temperature is below 800 DEG C; and (2) carrying out magnetron sputtering on a sputtering substrate by adopting the target material to obtain the lithium cobalt oxide film positive electrode material, the magnetron sputtering is accompanied by performing heat treatment on a sputtering substrate subjected to the magnetron sputtering at the same time. The cobalt source powder and the lithium source powder are used as raw materials and are subjected to cold pressing sintering to form the target material, and the magnetron sputtering and heat treatment processes which are simultaneously carried out are combined, so that the preparation of the lithium cobalt oxide film positive electrode material with good form uniformity, high film integrity and excellent performance is realized.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a lithium cobalt oxide thin film cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, the application and development of microelectronic products such as microelectromechanical systems (MEMS) and flexible wearable devices have become increasingly widespread. As a core component of these devices, the power supply supporting them is particularly important. The limitations of traditional batteries in terms of structure, size, and weight make them unsuitable for these microelectronic devices. Therefore, all-solid-state thin-film batteries have emerged, attracting widespread attention due to their advantages such as small size, customizable structure, high energy density, and flexible manufacturing capabilities. Thin-film cathode materials are a key component of all-solid-state thin-film lithium batteries, and their performance directly determines the overall performance of the thin-film battery. Therefore, the development of high-performance lithium battery cathode films has become a key focus of solid-state thin-film battery research. Among existing cathode materials, LiCoO2 is one of the most suitable for use as a thin-film cathode material due to its high energy density, small cycle deformation, and good conductivity.

[0003] Traditional methods for preparing thin-film cathodes primarily employ solution methods. This involves dissolving a metal salt or other precursor solution in a solvent, coating it onto a substrate, and then heat-treating it at high temperatures to ensure the formation of the thin-film material's crystal structure. This method is relatively simple to operate, can be completed at lower temperatures, and allows for easy control of the film's thickness and composition. It is suitable for various substrates and is less expensive than other methods, thus making it widely used.

[0004] For example, prior art CN104071854A discloses a precursor solution for forming a LiCoO2 film and a method for forming a LiCoO2 film using the solution. The LiCoO2 film precursor solution is a precursor solution for forming a LiCoO2 film used as a positive electrode material for a thin-film lithium secondary battery. The LiCoO2 film precursor solution is formed by dissolving an organolithium compound and an organocobalt compound in an organic solvent. The LiCoO2 film precursor solution is coated on a substrate and then heat-treated to form a LiCoO2 film used as a positive electrode material for a thin-film lithium secondary battery.

[0005] However, although solution methods can yield uniform cathode films, in large-scale production, the quality and uniformity of the films can be affected by the operating environment and conditions, making precise thickness control difficult and challenging to meet stringent requirements for consistency. Furthermore, during heat treatment, the film material needs to be annealed at high temperatures to remove solvents and increase crystallinity. Controlling heat treatment is complex and can lead to film cracks or morphological inhomogeneity, affecting the final performance of the LiCoO2 battery.

[0006] Therefore, how to prepare LiCoO2 thin film cathode materials with good morphological uniformity, high film integrity and excellent performance has become an urgent problem to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a lithium cobalt oxide thin-film cathode material, its preparation method, and its applications. The present invention uses cobalt source powder and lithium source powder as raw materials, which are cold-pressed and sintered to form a target material. Combined with simultaneous magnetron sputtering and heat treatment processes, this achieves the preparation of a lithium cobalt oxide thin-film cathode material with good morphological uniformity, high film integrity, and excellent performance.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a lithium cobalt oxide thin-film cathode material, the method comprising the following steps:

[0010] (1) Mix cobalt source powder and lithium source powder to obtain mixed powder, and perform cold pressing sintering on the mixed powder to obtain a target material; the temperature of the cold pressing sintering is below 800℃;

[0011] (2) The target material is used to perform magnetron sputtering on the sputtering substrate to obtain the lithium cobalt oxide thin film cathode material; the magnetron sputtering is accompanied by heat treatment of the sputtering substrate.

[0012] The lithium cobalt oxide thin film cathode material provided by this invention uses cobalt source powder and lithium source powder as raw materials. These are mixed and cold-pressed at a relatively low temperature below 800°C to form a target material still composed of cobalt and lithium sources. The target material is then magnetron sputtered, and the sputtered substrate is simultaneously heat-treated. Furthermore, the products formed during sputtering are also heat-treated. This process enables the preparation of lithium cobalt oxide thin films. The synergistic effect of these processes improves the uniformity of the target material sputtering distribution on the substrate surface and facilitates the control of the film's microstructure and crystallinity during lithium cobalt oxide synthesis. The simultaneous heat treatment during magnetron sputtering effectively reduces stress concentration during film preparation, preventing crack formation and ensuring film integrity. This process improves preparation efficiency while further optimizing the quality of the prepared lithium cobalt oxide thin film cathode material. This invention, through a simple, low-energy-consumption, low-cost, and high-efficiency preparation process, produces lithium cobalt oxide thin film cathode materials with good uniformity, high integrity, and excellent performance, which is beneficial for the industrial production of lithium cobalt oxide thin films.

[0013] Preferably, the cobalt source powder in step (1) includes cobalt tetroxide powder.

[0014] Preferably, the lithium source powder in step (1) includes lithium oxide powder.

[0015] Preferably, the molar ratio of lithium in the lithium source powder to cobalt in the cobalt source powder in step (1) is (1.2-1.5):1, for example, 1.20:1, 1.25:1, 1.30:1, 1.35:1, 1.40:1, 1.45:1 or 1.50:1, etc.

[0016] In the mixing process of step (1), the present invention introduces an excess of lithium source powder to compensate for the loss of lithium elements. During the cold pressing sintering process, the lithium source will volatilize at high temperature, resulting in insufficient lithium content. The excess lithium salt can ensure the lithium content in the final cathode material and avoid the instability of the material structure due to the lack of lithium.

[0017] Preferably, the particle size D50 of the cobalt source powder in step (1) is less than 1 μm, such as 1.0 μm, 0.8 μm, 0.6 μm, 0.4 μm, 0.2 μm, 0.1 μm, 0.08 μm or 0.06 μm.

[0018] Preferably, the particle size D50 of the lithium source powder in step (1) is less than 1 μm, such as 1.0 μm, 0.8 μm, 0.6 μm, 0.4 μm, 0.2 μm, 0.1 μm, 0.08 μm or 0.06 μm.

[0019] This invention improves the uniformity of raw material mixing by controlling the particle size of cobalt source powder and lithium source powder, thereby improving the quality of lithium cobalt oxide thin film cathode material obtained after simultaneous magnetron sputtering and heat treatment processes.

[0020] Preferably, the mixing method in step (1) includes ball milling.

[0021] Preferably, the specific process of mixing in step (1) includes: sequentially performing a first ball milling and a second ball milling on the mixed cobalt source powder and lithium source powder, wherein the rotation speed of the first ball milling is greater than the rotation speed of the second ball milling.

[0022] In this invention, cobalt source powder and lithium source powder are subjected to a first ball mill and a second ball mill together. The ball milling process is carried out with a high speed followed by a low speed to improve the mixing uniformity of the cobalt source powder and lithium source powder, thereby further improving the performance of the lithium cobalt oxide thin film cathode material obtained by subsequent processes.

[0023] Preferably, the rotational speed of the first ball mill is 380-420 rpm, such as 380 rpm, 390 rpm, 400 rpm, 410 rpm or 420 rpm.

[0024] Preferably, the first ball milling time is 30-60 minutes, such as 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes.

[0025] Preferably, the rotational speed of the second ball mill is 280-320 rpm, such as 280 rpm, 290 rpm, 300 rpm, 310 rpm or 320 rpm.

[0026] Preferably, the second ball milling time is 2-4 hours, such as 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours or 4.0 hours.

[0027] Preferably, the temperature of cold pressing sintering in step (1) is 400-800℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃.

[0028] The cold pressing sintering process provided by the present invention presses powdered raw materials of cobalt source and lithium source into block target material, and the substances in the target material still exist in the form of lithium source and cobalt source.

[0029] Preferably, the pressure of cold pressing sintering in step (1) is 100-400MPa, such as 100MPa, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa or 400MPa.

[0030] Preferably, the cold pressing and sintering time in step (1) is 1-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0031] Preferably, the target material obtained in step (1) includes a cobalt source and a lithium source.

[0032] Preferably, the cold pressing and sintering process in step (1) includes: pressing and sintering the mixed powder in sequence.

[0033] Preferably, before the magnetron sputtering in step (2), the cavity of the equipment used for magnetron sputtering is evacuated until the vacuum level of the cavity is 5.0 × 10⁻⁶. -4 -6.0×10 -4 Pa, for example 5.0 × 10 -4 Pa, 5.2 × 10 -4 Pa, 5.4 × 10 -4 Pa, 5.6 × 10 -4 Pa, 5.8 × 10 -4 Pa or 6.0 × 10 -4 Pa, etc.

[0034] Preferably, during the magnetron sputtering process in step (2), the distance between the target and the sputtering substrate is 50-70 mm, such as 50 mm, 52 mm, 54 mm, 56 mm, 58 mm, 60 mm, 62 mm, 64 mm, 66 mm, 68 mm or 70 mm.

[0035] Preferably, during the magnetron sputtering process described in step (2), a working gas is introduced into the cavity of the equipment used for magnetron sputtering.

[0036] Preferably, the working gas includes an inert gas and oxygen.

[0037] Preferably, the inert gas includes any one or a combination of at least two of argon, neon, or helium.

[0038] Preferably, the volume ratio of the inert gas to the oxygen is (20-50):1, such as 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, etc.

[0039] Preferably, the gas pressure in the cavity after the working gas is introduced is (2-5)×10⁻⁶. -3 Pa, for example 2.0 × 10 - 3 Pa, 2.5 × 10 -3 Pa, 3.0 × 10 -3 Pa, 3.5 × 10 -3 Pa, 4.0 × 10 -3 Pa, 4.5 × 10 -3 Pa or 5.0 × 10 -3 Pa, etc.

[0040] Preferably, the magnetron sputtering in step (2) includes pre-sputtering and formal sputtering in sequence.

[0041] Preferably, the sputtering substrate used in the pre-sputtering process is a sacrificial plate.

[0042] The present invention performs a pre-sputtering process before formal sputtering, which can remove the influence of impurities on the target surface on the final product and improve the quality of the obtained lithium cobalt oxide thin film cathode material.

[0043] Preferably, the pre-sputtering time is 5-20 min, such as 5 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, or 20 min.

[0044] Preferably, the sputtering substrate used in the formal sputtering process includes either a quartz substrate or a silicon substrate.

[0045] Preferably, the sputtering process is accompanied by rotation of the sputtering substrate.

[0046] Preferably, the rotation speed of the sputtering substrate is 10-20 r / min, such as 10 r / min, 12 r / min, 14 r / min, 16 r / min, 18 r / min or 20 r / min.

[0047] This invention rotates the sputtering substrate at a specific speed during the actual sputtering process to improve the uniformity of target sputtering, thereby optimizing the quality of the obtained lithium cobalt oxide thin film cathode material and improving its performance.

[0048] Preferably, the formal sputtering time is 0.5-2 hours, such as 0.5 hours, 0.6 hours, 0.8 hours, 1.0 hours, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2.0 hours.

[0049] Preferably, the power of the pre-sputtering and the formal sputtering are independently selected from 100-200W, such as 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W or 200W.

[0050] Preferably, the set temperature of the heat treatment in step (2) is 300-600℃, such as 300℃, 325℃, 350℃, 375℃, 400℃, 425℃, 450℃, 475℃, 500℃, 525℃, 550℃, 575℃ or 600℃.

[0051] This invention combines magnetron sputtering with heat treatment, enabling the preparation of high-performance lithium cobalt oxide thin-film cathode materials at lower temperatures, thereby reducing energy consumption and cost.

[0052] Preferably, the heating rate of the heat treatment is 5-15℃ / min, such as 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min or 15℃ / min, etc.

[0053] Preferably, after magnetron sputtering, the cavity for magnetron sputtering is further cooled.

[0054] Preferably, the specific process of the cooling treatment includes: maintaining the flow of working gas into the cavity of the equipment used for magnetron sputtering until the temperature of the sputtered substrate is below 200°C, and then stopping the flow of working gas, for example, at 200°C, 190°C, 180°C, 170°C, 160°C, or 150°C.

[0055] This invention maintains the flow of working gas into the cavity during the cooling process, effectively preventing air from entering the cavity during cooling and affecting the lithium cobalt oxide thin film cathode material formed inside the cavity, thereby damaging the excellent morphology and performance of the thin film material. The flow of working gas can be stopped below 200°C to avoid excessive flow of working gas, which would increase the preparation cost.

[0056] In this invention, since the sputtering products and the substrate have different coefficients of thermal expansion, they will separate during the cooling process, thereby obtaining lithium cobalt oxide thin film cathode material.

[0057] In a second aspect, the present invention provides a lithium cobalt oxide thin film cathode material, which is prepared by the preparation method described in the first aspect.

[0058] Thirdly, the present invention provides a lithium-ion battery comprising the lithium cobalt oxide thin film cathode material as described in the second aspect.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] The lithium cobalt oxide thin film cathode material provided by this invention uses cobalt source powder and lithium source powder as raw materials. These are mixed and cold-pressed at a relatively low temperature below 800°C to form a target material still composed of cobalt and lithium sources. The target material is then magnetron sputtered, and the sputtered substrate is simultaneously heat-treated. Furthermore, the products formed during sputtering are also heat-treated. This process enables the preparation of lithium cobalt oxide thin films. The synergistic effect of these processes improves the uniformity of the target material sputtering distribution on the substrate surface and facilitates the control of the film's microstructure and crystallinity during lithium cobalt oxide synthesis. The simultaneous heat treatment during magnetron sputtering effectively reduces stress concentration during film preparation, preventing crack formation and ensuring film integrity. This process improves preparation efficiency while further optimizing the quality of the prepared lithium cobalt oxide thin film cathode material. This invention, through a simple, low-energy-consumption, low-cost, and high-efficiency preparation process, produces lithium cobalt oxide thin film cathode materials with good uniformity, high integrity, and excellent performance, which is beneficial for the industrial production of lithium cobalt oxide thin films. Detailed Implementation

[0061] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0062] Example 1

[0063] This embodiment provides a method for preparing a lithium cobalt oxide thin film cathode material, including the following steps:

[0064] S1. Co3O4 powder with a particle size D50 of 0.5 μm and Li2O powder with a particle size D50 of 0.8 μm are ball-milled and mixed at a molar ratio of cobalt in Co3O4 powder to lithium in Li2O powder of 1:1.3. The specific process of ball milling is as follows: the mixed Co3O4 powder and Li2O powder are first ball-milled at 400 rpm for 50 min, and then ball-milled at 300 rpm for 3 h to obtain mixed powder. Then, the mixed powder is pressed into shape at 250 MPa for 1 h, and then sintered at 600℃ for 2 h to obtain the target material, which includes Co3O4 and Li2O.

[0065] S2. Place the target and sputtering substrate obtained in step S1 into the cavity of the magnetron sputtering equipment, with the distance between the target and the sputtering substrate set to 60 mm. Use a turbomolecular pump to evacuate the cavity of the magnetron sputtering equipment until the vacuum level of the cavity reaches 5.5 × 10⁻⁶ mm. -4 Pa.

[0066] S3. A heat treatment process in which the sputtering substrate in the magnetron sputtering cavity is heated at a heating rate of 10℃ / min, the set temperature of the heat treatment is 400℃, and a working gas is introduced into the cavity of the magnetron sputtering equipment. The working gas consists of argon and oxygen in a volume ratio of 30:1, and the working gas pressure of the cavity is maintained at 3×10. -3 Pa, set the magnetron sputtering power to 150W, and then, under heat treatment conditions, first use a sacrificial plate as the sputtering substrate, and use the target material obtained in step S1 to perform pre-sputtering on the sacrificial plate for 10 minutes to remove impurities on the target material surface. Then, use a silicon substrate as the sputtering substrate, and rotate the silicon substrate at 15 r / min, and continue to use the target material to perform formal sputtering on the silicon substrate for 2 hours.

[0067] S4. After magnetron sputtering is completed, the heat treatment of the substrate after magnetron sputtering is stopped, and the obtained product is allowed to cool down naturally with the cavity. During the cooling process, the working gas is continued to be introduced into the cavity until the temperature of the product drops to 200°C. Then, the introduction of the working gas is turned off, and the cooling continues until the temperature drops to 25°C. The obtained product is then removed to obtain the lithium cobalt oxide thin film cathode material.

[0068] Example 2

[0069] This embodiment provides a method for preparing a lithium cobalt oxide thin film cathode material, including the following steps:

[0070] S1. Co3O4 powder with a particle size D50 of 0.6 μm and Li2O powder with a particle size D50 of 0.7 μm are ball-milled and mixed at a molar ratio of cobalt in Co3O4 powder to lithium in Li2O powder of 1:1.2. The specific process of ball milling is as follows: the mixed Co3O4 powder and Li2O powder are first ball-milled at a speed of 380 rpm for 60 min, and then ball-milled at a speed of 280 rpm for 2 h to obtain mixed powder. Then, the mixed powder is pressed into shape at 100 MPa for 1 h, and then sintered at 400℃ for 4 h to obtain the target material, which includes Co3O4 and Li2O.

[0071] S2. Place the target and sputtering substrate obtained in step S1 into the cavity of the magnetron sputtering equipment, with the distance between the target and the sputtering substrate set to 50 mm. Use a turbomolecular pump to evacuate the cavity of the magnetron sputtering equipment until the vacuum level of the cavity reaches 5 × 10⁻⁶ mm. -4 Pa.

[0072] S3. A heat treatment process in which the sputtering substrate in the magnetron sputtering cavity is heated at a heating rate of 5℃ / min, the set temperature of the heat treatment is 300℃, and a working gas is introduced into the cavity of the magnetron sputtering equipment. The working gas consists of argon and oxygen in a volume ratio of 20:1, and the working gas pressure of the cavity is maintained at 2.0×10⁻⁶. -3 Pa, set the magnetron sputtering power to 100W, and then, under heat treatment conditions, first use a sacrificial plate as the sputtering substrate, and use the target material obtained in step S1 to perform pre-sputtering on the sacrificial plate for 20 minutes to remove impurities on the target material surface. Then, use a quartz substrate as the sputtering substrate, and rotate the quartz substrate at 10 r / min, and continue to use the target material to perform formal sputtering on the quartz substrate for 0.5 hours.

[0073] S4. After magnetron sputtering is completed, the heat treatment of the substrate after magnetron sputtering is stopped, and the obtained product is allowed to cool naturally in the cavity. During the cooling process, the working gas is continued to be introduced into the cavity until the temperature of the product drops to 180°C. Then, the introduction of the working gas is turned off, and the cooling continues until the temperature drops to 25°C. The obtained product is then removed to obtain the lithium cobalt oxide thin film cathode material.

[0074] Example 3

[0075] This embodiment provides a method for preparing a lithium cobalt oxide thin film cathode material, including the following steps:

[0076] S1. Co3O4 powder with a particle size D50 of 0.3 μm and Li2O powder with a particle size D50 of 0.8 μm are ball-milled and mixed at a molar ratio of cobalt in Co3O4 powder to lithium in Li2O powder of 1:1.5. The specific process of ball milling is as follows: the mixed Co3O4 powder and Li2O powder are first ball-milled at a speed of 420 rpm for 30 min, and then ball-milled at a speed of 320 rpm for 4 h to obtain mixed powder. Then, the mixed powder is pressed into shape at 400 MPa for 1 h, and then sintered at 800℃ for 1 h to obtain the target material, which includes Co3O4 and Li2O.

[0077] S2. Place the target and sputtering substrate obtained in step S1 into the cavity of the magnetron sputtering equipment. Set the distance between the target and the sputtering substrate to 70 mm. Use a direct-drive pump to evacuate the cavity of the magnetron sputtering equipment until the vacuum level of the cavity reaches 6 × 10⁻⁶ mm. -4 Pa.

[0078] S3. A heat treatment process is performed to heat the sputtering substrate in the magnetron sputtering cavity at a heating rate of 15℃ / min. The set temperature for the heat treatment is 600℃. Furthermore, a working gas, comprising argon and oxygen in a volume ratio of 50:1, is introduced into the cavity of the magnetron sputtering equipment, maintaining the working gas pressure in the cavity at 5.0 × 10⁻⁶. -3 Pa, set the magnetron sputtering power to 200W, and then, under heat treatment conditions, first use a sacrificial plate as the sputtering substrate, and use the target material obtained in step S1 to perform pre-sputtering on the sacrificial plate for 10 minutes to remove impurities on the target material surface. Then, use a silicon substrate as the sputtering substrate, and rotate the silicon substrate at 20 r / min, and continue to use the target material to perform formal sputtering on the silicon substrate for 1.5 hours.

[0079] S4. After magnetron sputtering is completed, the heat treatment of the substrate after magnetron sputtering is stopped, and the obtained product is allowed to cool naturally in the cavity. During the cooling process, the working gas is continued to be introduced into the cavity until the temperature of the product drops to 190°C. Then, the introduction of the working gas is turned off, and the cooling continues until the temperature drops to 25°C. The obtained product is then removed to obtain the lithium cobalt oxide thin film cathode material.

[0080] Example 4

[0081] The only difference between this embodiment and Embodiment 1 is that in step S1, Co3O4 powder and Li2O powder are ball-milled and mixed with a molar ratio of cobalt in Co3O4 powder to lithium in Li2O powder of 1:1. All other aspects are the same as in Embodiment 1.

[0082] Example 5

[0083] The only difference between this embodiment and Embodiment 1 is that in step S1, Co3O4 powder and Li2O powder are ball-milled and mixed at a molar ratio of cobalt in Co3O4 powder to lithium in Li2O powder of 1:1.7. All other contents are the same as in Embodiment 1.

[0084] Example 6

[0085] The only difference between this embodiment and Embodiment 1 is that in step S2, the distance between the target and the sputtering substrate is 40mm. All other aspects are the same as in Embodiment 1.

[0086] Example 7

[0087] The only difference between this embodiment and Embodiment 1 is that in step S2, the distance between the target and the sputtering substrate is 80mm. All other aspects are the same as in Embodiment 1.

[0088] Example 8

[0089] The only difference between this embodiment and Embodiment 1 is that in step S3, the set temperature for the heat treatment is 200°C. All other aspects are the same as in Embodiment 1.

[0090] Example 9

[0091] The only difference between this embodiment and Embodiment 1 is that in step S3, the set temperature for the heat treatment is 700°C. All other aspects are the same as in Embodiment 1.

[0092] Example 10

[0093] The only difference between this embodiment and Embodiment 1 is that step S3, the rotation process of the silicon substrate, is omitted. All other aspects are the same as in Embodiment 1.

[0094] Example 11

[0095] The only difference between this embodiment and Embodiment 1 is that step S4, which involves introducing working gas into the cavity during the cooling process, is omitted. All other aspects are the same as in Embodiment 1.

[0096] Example 12

[0097] The only difference between this embodiment and Embodiment 1 is that in step S4, when the temperature drops to 300°C, the supply of the working gas is shut off. All other aspects are the same as in Embodiment 1.

[0098] Example 13

[0099] The only difference between this embodiment and Embodiment 1 is that the particle size D50 of the Co3O4 powder and the Li2O powder used in step S1 is 3 μm. All other aspects are the same as in Embodiment 1.

[0100] Example 14

[0101] The only difference between this embodiment and Embodiment 1 is that the ball milling process used in step S1 is as follows: the mixed Co3O4 powder and Li2O powder are directly ball milled at 400 rpm for 4 hours. All other aspects are the same as in Embodiment 1.

[0102] Comparative Example 1

[0103] The only difference between this comparative example and Example 1 is that the sintering temperature in step S1 is 900°C. All other aspects are the same as in Example 1.

[0104] Comparative Example 2

[0105] The only difference between this comparative example and Example 1 is that step S3, the heat treatment process, is omitted. All other aspects are the same as in Example 1.

[0106] Comparative Example 3

[0107] The only difference between this comparative example and Example 1 is that the heat treatment process in step S3 during magnetron sputtering is omitted, and the magnetron sputtering process is performed only at 25°C. After magnetron sputtering, the sputtered product is subjected to heat treatment at 400°C for 2 hours. All other contents are the same as in Example 1.

[0108] The lithium cobalt oxide thin film cathode materials provided in the above embodiments and comparative examples are used in all-solid-state lithium-ion batteries. The lithium cobalt oxide thin film cathode materials provided in the above embodiments and comparative examples are assembled with lithium zirconium oxide solid electrolyte film and metal Li anode to prepare an all-solid-state lithium-ion battery.

[0109] The crystallinity of the lithium cobalt oxide thin-film cathode materials provided in the above embodiments and comparative examples was tested, and the electrochemical tests were performed on the batteries assembled from the lithium cobalt oxide thin-film cathode materials provided in the above embodiments and comparative examples. The testing process is as follows:

[0110] (1) Crystallinity testing process: The crystallinity of the material is calculated by measuring the diffraction intensity at different diffraction angles using XRD.

[0111] (2) Electrochemical test process: Cycle 200 times at room temperature 25℃, voltage range of 2.4~4.6V, and 1C rate, and record the first discharge specific capacity of the battery and the capacity retention rate after 200 cycles.

[0112] The test results are shown in Table 1:

[0113] Table 1

[0114]

[0115]

[0116] The test results show that:

[0117] (1) As can be seen from Examples 1 to 3, the present invention uses cobalt source powder and lithium source powder as raw materials to form a target material by cold pressing and sintering. Combined with the simultaneous magnetron sputtering and heat treatment process, the preparation of lithium cobalt oxide thin film cathode material with good morphological uniformity, high film integrity and excellent performance is achieved, thereby improving the electrochemical performance of the battery assembled with lithium cobalt oxide thin film cathode material.

[0118] (2) By comparing Examples 1 and Examples 4-5, it can be seen that if the relative amount of cobalt source added is too large and the relative amount of lithium source added is too small, the excess cobalt element will be unevenly distributed in the lattice of lithium cobalt oxide, affecting the stability of the crystal structure of the lithium cobalt oxide film; if the relative amount of cobalt source added is too small and the relative amount of lithium source added is too large, the lithium cobalt oxide lattice will be unstable and the formed grains will be small, thereby affecting the crystallinity and electrochemical performance of the obtained lithium cobalt oxide film cathode material.

[0119] (3) By comparing Examples 1 and 6-7, it can be seen that if the target and the sputtering substrate are too close during the magnetron sputtering process, the lattice structure of the formed lithium cobalt oxide film will be unsatisfactory, the uniformity and quality of the film will be reduced, and the electrochemical cycle performance of the battery will be reduced. If the target and the sputtering substrate are too far apart, the deposition of the formed lithium cobalt oxide film may be uneven, resulting in non-uniform thickness or surface morphology problems, which will affect the improvement of the electrochemical performance of the battery.

[0120] (4) By comparing Examples 1 and Examples 8-9, it can be seen that if the heat treatment temperature is set too low, it will affect the crystallinity, uniformity and integrity of the obtained film, resulting in cracks on the surface of the film, decreased film performance, worse battery performance, or even failure to prepare lithium cobalt oxide film; if the heat treatment temperature is set too high, it will cause the obtained film to have lattice defects, affecting the crystallinity of the film.

[0121] (5) By comparing Example 1 and Example 10, it can be seen that if the rotation of the substrate is omitted in the magnetron sputtering process, the sputtering will be uneven, the quality of the final lithium cobalt oxide thin film cathode material will be worse, and the battery performance will be reduced.

[0122] (6) By comparing Example 1 and Example 11-12, it can be seen that if the process of introducing working gas into the cavity during the cooling process is omitted or the temperature of stopping the introduction of working gas is too high, air will enter the cavity during the cooling process, which will cause the quality of the obtained lithium cobalt oxide thin film cathode material to deteriorate and the battery performance to decline.

[0123] (7) By comparing Example 1 and Example 13, it can be seen that if the raw materials used in this invention are Co3O4 powder and Li2O powder with larger particle size, the uniformity of the raw material mixing will be poor, and the distribution of cobalt oxide and lithium oxide in the target material will be uneven, thereby affecting the quality of the subsequently obtained lithium cobalt oxide thin film cathode material, and thus causing the electrochemical performance of the battery to decline.

[0124] (8) By comparing Example 1 and Example 14, it can be seen that if the present invention adopts a one-stage ball milling process, the uniformity of raw material mixing will decrease, thereby affecting the quality and electrochemical cycle performance of the final prepared lithium cobalt oxide thin film cathode material.

[0125] (9) By comparing Example 1 with Comparative Example 1, it can be seen that if the sintering temperature during the cold pressing sintering process is too high, the target material will undergo physical changes, such as melting, expansion or structural damage. This will not only affect the function of the target material, but may also lead to instability during the sputtering process, thereby affecting the quality of the film.

[0126] (10) By comparing Example 1 with Comparative Examples 2-3, it can be seen that if the heat treatment process is omitted during the magnetron sputtering process, the preparation of lithium cobalt oxide thin film cathode material cannot be achieved, thus affecting the electrochemical performance of the battery. If magnetron sputtering is performed first and then heat treatment is performed, the crystallinity, uniformity and integrity of the lithium cobalt oxide thin film cathode material will deteriorate, the film quality will deteriorate, and the electrochemical cycle performance of the battery will deteriorate.

[0127] In summary, the lithium cobalt oxide thin film cathode material provided by this invention uses cobalt source powder and lithium source powder as raw materials. These are mixed and cold-pressed at a relatively low temperature below 800°C to form a target material still composed of cobalt and lithium sources. The target material is then subjected to magnetron sputtering, and the sputtered substrate is simultaneously heat-treated. Furthermore, the products formed during sputtering are also heat-treated. This process enables the preparation of lithium cobalt oxide thin films. Moreover, the synergistic effect of these processes improves the uniformity of target sputtering distribution on the substrate surface and promotes the control of the film's microstructure and crystallinity during lithium cobalt oxide synthesis. The simultaneous heat treatment during magnetron sputtering effectively reduces stress concentration during film preparation, preventing crack formation and ensuring film integrity. The aforementioned process improves preparation efficiency while further optimizing the quality of the prepared lithium cobalt oxide thin film cathode material. This invention utilizes a simple, low-energy-consumption, low-cost, and high-efficiency preparation process to prepare lithium cobalt oxide thin film cathode materials with good uniformity, high integrity, and excellent performance, which is beneficial for the industrial production of lithium cobalt oxide thin films.

[0128] 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 lithium cobalt oxide thin-film cathode material, characterized in that, The preparation method includes the following steps: (1) Mix cobalt source powder and lithium source powder to obtain mixed powder, and perform cold pressing sintering on the mixed powder to obtain a target material; the temperature of the cold pressing sintering is below 800℃; (2) The target material is used to perform magnetron sputtering on the sputtering substrate to obtain the lithium cobalt oxide thin film cathode material; the magnetron sputtering is accompanied by heat treatment of the sputtering substrate.

2. The preparation method according to claim 1, characterized in that, The cobalt source powder mentioned in step (1) includes cobalt tetroxide powder; Preferably, the lithium source powder in step (1) includes lithium oxide powder; Preferably, the molar ratio of lithium in the lithium source powder to cobalt in the cobalt source powder in step (1) is (1.2-1.5):1; Preferably, the particle size D50 of the cobalt source powder in step (1) is less than 1 μm; Preferably, the particle size D50 of the lithium source powder in step (1) is less than 1 μm; Preferably, the specific process of mixing in step (1) includes: sequentially performing a first ball milling and a second ball milling on the mixed cobalt source powder and lithium source powder, wherein the rotation speed of the first ball milling is greater than the rotation speed of the second ball milling.

3. The preparation method according to claim 1 or 2, characterized in that, The temperature for cold pressing and sintering in step (1) is 400-800℃; Preferably, the pressure of cold pressing sintering in step (1) is 100-400 MPa; Preferably, the cold pressing and sintering time in step (1) is 1-5 hours; Preferably, the target material obtained in step (1) includes a cobalt source and a lithium source.

4. The preparation method according to any one of claims 1-3, characterized in that, Before the magnetron sputtering in step (2), the cavity of the equipment used for magnetron sputtering is evacuated until the vacuum level of the cavity is 5.0 × 10⁻⁶. -4 -6.0×10 -4 Pa; Preferably, during the magnetron sputtering process in step (2), the distance between the target and the sputtering substrate is 50-70 mm.

5. The preparation method according to any one of claims 1-4, characterized in that, During the magnetron sputtering process described in step (2), working gas is introduced into the cavity of the equipment used for magnetron sputtering; Preferably, the working gas includes an inert gas and oxygen; Preferably, the volume ratio of the inert gas to the oxygen is (20-50):1; Preferably, the gas pressure in the cavity after the working gas is introduced is (2-5)×10⁻⁶. -3 Pa.

6. The preparation method according to any one of claims 1-5, characterized in that, Step (2) of the magnetron sputtering includes pre-sputtering and formal sputtering in sequence; Preferably, the pre-sputtering time is 5-20 minutes.

7. The preparation method according to claim 6, characterized in that, The sputtering substrate used in the formal sputtering process includes either a quartz substrate or a silicon substrate. Preferably, the formal sputtering process is accompanied by rotation of the sputtering substrate; Preferably, the rotational speed of the sputtering substrate is 10-20 r / min; Preferably, the power of the pre-sputtering and the formal sputtering are independently selected from 100-200W.

8. The preparation method according to any one of claims 1-7, characterized in that, The set temperature for the heat treatment in step (2) is 300-600℃; Preferably, the heating rate of the heat treatment in step (2) is 5-15℃ / min; Preferably, after magnetron sputtering, the cavity for magnetron sputtering is further subjected to a cooling treatment; Preferably, the specific process of the cooling treatment includes: maintaining the flow of working gas into the cavity of the equipment used for magnetron sputtering until the temperature of the sputtered substrate is below 200°C, and then stopping the flow of working gas.

9. A lithium cobalt oxide thin-film cathode material, characterized in that, The lithium cobalt oxide thin film cathode material is prepared by the preparation method described in any one of claims 1-8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium cobalt oxide thin film cathode material as described in claim 9.

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