Positive electrode material surface coating method based on vacuum ion plating and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a cathode material surface coating method based on vacuum ion plating and application of the cathode material surface coating method. The surface coating method comprises the following steps: placing lithium cobalt oxide, nickel cobalt lithium manganate or nickel cobalt lithium aluminate and other positive electrode material powder on a vibrating screen, melting target material powder by adopting an electron beam to carry out ion-assisted deposition coating, forming a continuous coating layer of 2-50nm, and finally carrying out annealing treatment. According to the invention, the problem of capacity fading caused by unstable interface of a traditional positive electrode material under high voltage (greater than or equal to 4.5 V) is solved, atomic-scale tight coating is realized through a vacuum ion plating technology, the cycling stability and rate capability of the material are remarkably improved, and the material is suitable for a lithium ion battery for a high-end electronic product.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for coating the surface of a positive electrode material based on vacuum ion plating and an application thereof. Background Art

[0002] As lithium-ion batteries develop toward higher energy density, lithium cobalt oxide, the earliest commercialized cathode material, continues to play a key role in consumer electronics due to its high theoretical capacity and stable voltage platform. However, when charging voltages are increased above 4.5V, the material faces challenges such as structural phase transitions, interfacial side reactions, and metal ion dissolution. These issues manifest as rapid capacity decay and reduced average discharge voltage during cycling, severely restricting the battery's high-voltage applications.

[0003] Traditional modification methods, such as bulk doping or mechanical mixing and coating, have significant limitations. Bulk doping can improve intrinsic stability but can sacrifice material capacity. Mechanically mixed coatings, on the other hand, have weak bonds with the active material, easily fall off during cycling, and are difficult to achieve uniform nanoscale coverage. Furthermore, physically mixed coatings can hinder lithium ion transport, leading to reduced rate performance.

[0004] Therefore, developing a technology that can achieve tight atomic-level coating and combine interface stability and ion conductivity has become the key to breaking through the bottleneck of high-voltage applications of lithium cobalt oxide.

[0005] Vacuum ion plating technology, due to its unique atomic-level deposition capabilities, has shown potential in the field of material surface modification. This technology combines electron beam melting with ion-assisted deposition to form a dense and firmly bonded functional layer on the substrate surface. If it can be applied to the coating of positive electrode materials, it is expected to construct an interface protection layer that is both physically isolated and chemically stable. However, the existing technology lacks targeted research on the vacuum ion plating process of conventional positive electrode materials, making it difficult to balance the density of the coating layer, ionic conductivity, and interfacial compatibility with the substrate. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to propose a surface coating method of a positive electrode material based on vacuum ion plating and its application, so as to provide a positive electrode material that can still maintain excellent cycle stability and high rate performance under high voltage cycling.

[0007] Based on the above objectives, the present invention provides a method for surface coating of a positive electrode material based on vacuum ion plating, comprising the following steps: placing positive electrode material powder on a vibrating screen, then melting the target material powder and depositing and coating it on the surface of the positive electrode material powder, and after the coating is completed, performing annealing treatment and cooling to room temperature to obtain a positive electrode material based on vacuum ion plating.

[0008] Preferably, the positive electrode material powder is one of lithium cobalt oxide powder, lithium nickel cobalt manganese oxide powder and lithium nickel cobalt aluminum oxide powder.

[0009] More preferably, the particle size of the positive electrode material powder is 1-20 μm.

[0010] Preferably, the target powder is one of oxide powder, fluoride powder and phosphate powder.

[0011] More preferably, the oxide powder is one of Al2O3, ZnO, and ZrO2; the fluoride powder is one of AlF3 and LiF; and the phosphate powder is one of Li3PO4 and LiFePO4.

[0012] Furthermore, the purity of the Al2O3 powder is 99.9%, and the particle size is 5-10 μm; the purity of the AlF3 powder is 99.9%, and the particle size is 5-10 μm; the purity of the Li3PO4 powder is 99.9%, and the particle size is 5-10 μm.

[0013] Preferably, the melting is performed by using an electron beam in a vacuum environment, and the operating parameters of the electron beam are 5-10 kV and 200-500 mA.

[0014] Preferably, the deposition coating is carried out under atmosphere protection, the chamber pressure is 0.1-1.0 Pa, the power is 200-600 W, the deposition coating time is 0.5-5 h, and the coating thickness is 2-50 nm.

[0015] More preferably, the protective atmosphere is one of oxygen, argon, and nitrogen, or a mixture of two of them.

[0016] Preferably, the annealing is performed in an inert atmosphere or air atmosphere at a temperature of 200-500° C. for 2-6 hours.

[0017] Preferably, the positive electrode material coating layer based on vacuum ion plating is continuous and uniform, forms a chemical bond with the surface of the positive electrode material, has a stable structure, and an ionic conductivity of ≥1×10 -5 S / cm.

[0018] Preferably, the present invention also proposes an application of a positive electrode material based on vacuum ion plating for lithium-ion batteries.

[0019] Preferably, the lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet is obtained by uniformly mixing the above-mentioned positive electrode material with SuperP, PVDF and N-methylpyrrolidone, coating the mixture on a positive electrode current collector and drying the mixture, comprising the following steps:

[0020] The positive electrode material based on vacuum ion plating, SuperP, PVDF and N-methylpyrrolidone are mixed evenly to obtain a positive electrode slurry, and then the positive electrode slurry is coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0021] Preferably, the weight ratio of the positive electrode material based on vacuum ion plating, SuperP, PVDF, and N-methylpyrrolidone is 70-90:2-10:2-10:4-10.

[0022] Beneficial effects of the present invention:

[0023] The vacuum ion plating coating process of the present invention constructs a nano-scale dense protective layer on the surface of lithium cobalt oxide through the synergistic effect of electron beam and ion source, achieving multiple technical advantages. First, the coating layer and the substrate are combined at the atomic level to form a continuous coverage, which effectively isolates the direct contact between the electrolyte and the active material, inhibits the oxidative decomposition reaction and cobalt ion dissolution under high pressure, and significantly extends the cycle life; secondly, the uniform coating layer can alleviate the lattice volume change during the charge and discharge process, reduce particle cracks and active material peeling, and maintain the integrity of the electrode structure. In addition, the coating layer formed by ion-assisted deposition not only ensures the smooth flow of lithium ion transmission channels, but also reduces the interface impedance, thereby improving the capacity utilization at high rates.

[0024] The present invention can adapt to the deposition requirements of different coating materials (such as oxides, fluorides, and phosphates) by regulating electron beam parameters and annealing temperature, thereby achieving precise control of the coating layer thickness and crystallinity.

[0025] The present invention provides a new approach for the development of high-voltage lithium cobalt oxide positive electrode materials, and is particularly suitable for the field of high-end electronic products with stringent requirements on energy density and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the present invention or the prior art, the following briefly introduces the drawings required for the embodiments or the prior art description.

[0027] Figure 1 Schematic diagram of a vacuum ion plating device according to an embodiment of the present invention;

[0028] Figure 2 This is a TEM image of the coated positive electrode material obtained in Example 2 of the present invention;

[0029] Figure 3 The cycle capacity of the battery assembled with the positive electrode materials obtained in Examples 2, 5, and 8 of the present invention and Comparative Example 2;

[0030] Figure 4 The average discharge voltage of batteries assembled with the positive electrode materials obtained in Examples 2, 5, and 8 of the present invention and Comparative Example 2;

[0031] Figure 5 The discharge capacities of batteries assembled with the positive electrode materials obtained in Examples 2, 5, and 8 of the present invention and Comparative Example 2 at different rates. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0033] Example 1: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0034] (1) First, 200 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 50 Hz), and then 40 g of Al2O3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The Al2O3 powder is heated to a molten state by an electron beam (5 kV, 200 mA). Then, the ion source (power 200 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0035] (2) 70g of Al2O3@lithium cobalt oxide sample, 10g of Super P, 10g of PVDF and 10g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0036] Example 2: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0037] (1) First, 210 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 100 Hz), and then 45 g of Al2O3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The Al2O3 powder is heated to a molten state by an electron beam (7 kV, 350 mA). Then, the ion source (power 400 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0038] (2) 80 g of Al2O3@lithium cobalt oxide sample, 6 g of SuperP, 6 ​​g of PVDF and 8 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0039] Example 3: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0040] (1) First, 220 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 200 Hz), and then 50 g of Al2O3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The Al2O3 powder is heated to a molten state by an electron beam (10 kV, 500 mA). Then, the ion source (power 600 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0041] (2) 90 g of Al2O3@lithium cobalt oxide sample, 2 g of SuperP, 2 g of PVDF and 6 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0042] Example 4: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0043] (1) First, 200 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 50 Hz), and then 40 g of AlF3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The AlF3 powder is heated to a molten state by an electron beam (5 kV, 200 mA). Then, the ion source (power 200 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0044] (2) 70g of AlF3@lithium cobalt oxide sample, 10g of SuperP, 10g of PVDF and 10g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0045] Example 5: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0046] (1) First, 210 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 100 Hz), and then 45 g of AlF3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The AlF3 powder is heated to a molten state by an electron beam (7 kV, 350 mA). Then, the ion source (power 400 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0047] (2) 80 g of AlF3@lithium cobalt oxide sample, 6 g of SuperP, 6 ​​g of PVDF and 8 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0048] Example 6: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0049] (1) First, 220 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 200 Hz), and then 50 g of AlF3 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The AlF3 powder is heated to a molten state by an electron beam (10 kV, 500 mA). Then, the ion source (power 600 W) is started and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0050] (2) 90 g of AlF3@lithium cobalt oxide sample, 2 g of SuperP, 2 g of PVDF and 6 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0051] Example 7: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0052] (1) First, 200 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 50 Hz), and then 40 g of Li3PO4 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The electron beam (5 kV, 200 mA) is turned on to heat the Li3PO4 powder to a molten state. Then, the ion source (power 200 W) is turned on and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0053] (2) 70 g of Li3PO4@lithium cobalt oxide sample, 10 g of SuperP, 10 g of PVDF and 10 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0054] Example 8: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0055] (1) First, 210 g of lithium cobalt oxide powder (D50 is 1-20 μm) was placed in a vibrating screen (frequency 100 Hz), and then 45 g of Li3PO4 powder (purity 99.9%, particle size 5-10 μm) was placed in a crucible. The electron beam (7 kV, 350 mA) was turned on to heat the Li3PO4 powder to a molten state. Then, the ion source (power 400 W) was turned on and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0056] (2) 80 g of Li3PO4@lithium cobalt oxide sample, 6 g of SuperP, 6 ​​g of PVDF and 8 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0057] Example 9: A method for preparing a positive electrode material and a positive electrode sheet thereof based on vacuum ion plating, the specific preparation steps are as follows:

[0058] (1) First, 220 g of lithium cobalt oxide powder (D50 is 1-20 μm) is placed in a vibrating screen (frequency 200 Hz), and then 50 g of Li3PO4 powder (purity 99.9%, particle size 5-10 μm) is placed in a crucible. The electron beam (10 kV, 500 mA) is turned on to heat the Li3PO4 powder to a molten state. Then, the ion source (power 600 W) is turned on and a mixed gas of hydrogen and argon (V 氧 :V 氩 The ratio of the ...

[0059] (2) 90 g of Li3PO4@lithium cobalt oxide sample, 2 g of SuperP, 2 g of PVDF and 6 g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0060] Comparative Example 1: The difference from Example 2 is that aluminum oxide and lithium cobalt oxide are directly mixed as the positive electrode material. The remaining steps are the same as Example 2. The specific steps are as follows:

[0061] Mix 14.12g Al2O3 (purity 99.9%, particle size 5-10μm), 65.88g (D50 is 1-20μm) lithium cobalt oxide powder, 6g Super P, 6g PVDF and 8g N-methylpyrrolidone to obtain a positive electrode slurry, then apply the positive electrode slurry to an aluminum foil current collector and dry it to obtain a positive electrode sheet.

[0062] Comparative Example 2: The difference between Example 2 and Comparative Example 2 is that aluminum chloride is not added for coating. As the positive electrode material, the remaining steps are the same as those of Example 2. The specific steps are as follows:

[0063] 80g of lithium cobalt oxide powder (D50 is 1-20μm), 6g of SuperP, 6g of PVDF and 8g of N-methylpyrrolidone were mixed evenly to obtain a positive electrode slurry, which was then coated on an aluminum foil current collector and dried to obtain a positive electrode sheet.

[0064] Performance Testing

[0065] CR2032 button batteries were assembled in a glove box with an oxygen content of <0.1ppm. The batteries were assembled using the positive electrode sheets (14mm in diameter) obtained in the embodiments and comparative examples and the metallic lithium negative electrode. The separator was a Celgard 2325 polypropylene three-layer composite film. The electrolyte was EC / DMC containing 1M LiPF6 (volume ratio of 1:1). The assembled battery samples were subjected to electrochemical performance tests. The experimental parameters of the electrochemical performance test were as follows: the charge and discharge voltage range of the battery was 3.0-4.5V, and the battery working process was as follows: first, the current was cycled twice at 0.1C, and the subsequent cycle test current was 1C rate, and the cycle was repeated 400 times. The rate performance of the battery was continuously tested at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 0.1C, and each rate was cycled 5 times. The test results are shown in the figure.

[0066] Table 1 Electrochemical properties of vacuum ion plating coated positive electrode

[0067]

[0068]

[0069] Data Analysis: As can be seen from the example data in Table 1, the vacuum ion plating coated cathode material prepared by the present invention exhibits excellent cycle stability and rate performance, which is mainly attributed to the nanoscale protective barrier formed by the coating layer on the surface of lithium cobalt oxide and its unique interface regulation mechanism. Through electron beam melting combined with ion-assisted deposition process, the coating layer material is able to achieve close atomic-level contact with the lithium cobalt oxide particles. This dense coating structure effectively blocks the corrosion of the active material by the electrolyte and significantly inhibits the occurrence of cobalt dissolution and interfacial side reactions during high-voltage cycles. The material can still maintain a capacity retention rate of more than 70% at a high voltage of 4.5V and after 400 cycles, showing the potential for industrial application.

[0070] From the comparative data of Example 2 and Comparative Examples 1 and 2 in Table 1, it can be seen that the Al2O3@lithium cobalt oxide positive electrode material prepared by the vacuum ion plating coating process exhibits significantly better electrochemical performance than the physically mixed and uncoated samples. This difference is due to the multiple protection mechanisms constructed by the coating layer at the material interface. First, the nanoscale Al2O3 coating layer formed by electron beam melting combined with ion-assisted deposition achieves a close bond with the surface of the lithium cobalt oxide particles at the atomic scale, rather than mechanical contact of physical mixing. This dense coating structure can effectively block the erosion of the electrolyte on the active material during the cycle, inhibiting the dissolution of cobalt ions and interfacial side reactions, thereby maintaining a higher discharge average voltage stability; secondly, the uniform coating layer reduces the generation of particle cracks by alleviating the lattice stress concentration during the charge and discharge process, while the physical mixing sample lacks this protection, and the active material is more prone to structural degradation; and the directly mixed Al2O3 may hinder the ion conduction path due to insufficient dispersion. These differences in interface properties together explain the capacity retention advantage of the vacuum ion plating sample in long-term cycling.

[0071] Figure 1 The structural design of the vacuum ion plating device is demonstrated, and the precise deposition of coating materials is achieved through the synergistic effect of electron beam and ion source. Figure 2 TEM images show that the coating layer forms a continuous and uniform 4nm interface layer on the surface of lithium cobalt oxide particles, laying the foundation for material stability.

[0072] Figure 3 The comparison of the cycling performance shows that the capacity retention of the three coated lithium cobalt oxide samples after 400 cycles at 4.5V is significantly better than that of the uncoated sample. Figure 4 This is further verified in the voltage decay curves: the voltage decay amplitude of the three coated samples is reduced during the cycle, and the average discharge voltage is much higher than that of the uncoated sample, proving that it effectively inhibits electrode polarization. Figure 5 The rate performance test shows that the discharge capacity of the coated sample at high rate is significantly improved compared with the uncoated sample, highlighting the role of the coating layer in promoting ion transport.

[0073] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for coating the surface of a cathode material based on vacuum ion plating, characterized in that: The method comprises the following steps: placing cathode material powder on a vibrating screen, then melting target material powder and depositing and coating the target material powder on the surface of the cathode material powder; after coating, performing annealing treatment and cooling to room temperature to obtain a cathode material based on vacuum ion plating; The deposition coating is carried out under atmosphere protection, with a chamber pressure of 0.1-1.0 Pa, a power of 200-600 W, a deposition coating time of 0.5-5 h, and a coating thickness of 2-50 nm.

2. The surface coating method according to claim 1, characterized in that The positive electrode material powder is one of lithium cobalt oxide powder, lithium nickel cobalt manganese oxide powder and lithium nickel cobalt aluminum oxide powder.

3. The surface coating method according to claim 1, characterized in that: The target powder is one of oxide powder, fluoride powder and phosphate powder.

4. The surface coating method according to claim 3, characterized in that: The oxide powder is one of Al2O3, ZnO, and ZrO2; the fluoride powder is one of AlF3 and LiF; and the phosphate powder is one of Li3PO4 and LiFePO4.

5. The surface coating method according to claim 1, characterized in that: The melting is performed by using an electron beam in a vacuum environment, wherein the working parameters of the electron beam are 5-10 kV and 200-500 mA.

6. The surface coating method according to claim 1, characterized in that: The annealing is carried out in an inert atmosphere or air atmosphere at a temperature of 200-500° C. for 2-6 hours.

7. A positive electrode material based on vacuum ion plating, characterized in that: The positive electrode material is prepared by the surface coating method according to any one of claims 1 to 6, the coating layer is continuous and uniform, forms a chemical bond with the surface of the positive electrode material, has a stable structure, and an ionic conductivity of ≥1×10 -5 S / cm.

8. An application of the positive electrode material based on vacuum ion plating according to claim 7, characterized in that: Used for lithium-ion batteries; the lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet is obtained by evenly mixing a positive electrode material based on vacuum ion plating with Super P, PVDF, and N-methylpyrrolidone, coating the mixture on a positive electrode collector, and then drying the mixture. The specific steps are as follows: evenly mixing a positive electrode material based on vacuum ion plating, Super P, PVDF, and N-methylpyrrolidone to obtain a positive electrode slurry, and then coating the positive electrode slurry on an aluminum foil current collector, drying, and obtaining a positive electrode sheet.

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