Coated modified ternary positive electrode material and preparation method and use thereof

Abstract

This invention provides a coated and modified ternary cathode material, its preparation method, and its applications. The coated and modified ternary cathode material includes matrix particles and a modified layer coating the matrix particles; the matrix particles include high-nickel lithium nickel cobalt manganese oxide with the chemical formula LiNi. x Co y Mn z O2, x≥0.8; the modified layer includes Co3O4. This invention effectively suppresses surface side reactions, alleviates lattice distortion, and improves thermal stability, cycle stability, and interfacial conductivity by constructing a uniform and conductive Co3O4 coating thin layer on the surface of high-nickel lithium nickel cobalt manganese oxide particles. Moreover, this coating layer has good interfacial bonding.

Description

Technical Field

[0001] This invention belongs to the field of battery materials and battery technology, and relates to a coated and modified ternary cathode material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, with their high energy density, have become the mainstream energy solution for electric vehicles. Among these, the cathode material is a key component affecting battery energy density. In recent years, high-nickel ternary materials such as lithium nickel cobalt manganese oxide (LiNi) have emerged as important energy sources. x Co y Mn z O2 (x≥0.8) has gradually become a research hotspot in the field due to its significant energy density advantage.

[0003] However, high-nickel ternary materials often have the following problems in practical applications: in order to suppress Ni 2+ / Li + Cation mixing typically requires the introduction of excess lithium source during preparation. The resulting residual lithium readily reacts with environmental moisture to form lithium carbonate, thus affecting electrochemical performance. Simultaneously, high-nickel materials are prone to lattice oxygen loss during charge-discharge processes, leading to the formation of an irreversible rock-salt phase, which reduces the lithium-ion diffusion coefficient. High-nickel materials also undergo interfacial side reactions with the electrolyte, forming an electrolyte interface layer that restricts lithium diffusion and increases charge transfer resistance. During deep delithiation, highly active Ni... 4+ Easily reduced to Ni 2+ It releases oxygen, which can easily lead to thermal runaway; moreover, the internal stress generated by the shrinkage of the anisotropic lattice during the cycle leads to the formation of microcracks, which accelerates the deterioration of the material structure.

[0004] To address these issues, existing technologies employ surface coating strategies for modification, such as coating with oxides like titanium dioxide, silicon dioxide, alumina, and zirconium oxide, to construct physical isolation layers and suppress interfacial side reactions. However, conventional oxide coatings have poor conductivity, serving only a physical isolation function and failing to effectively conduct lithium ions and electrons, resulting in severe polarization during high-rate charge-discharge cycles. Furthermore, the adhesion between the coating and the substrate is weak, making it prone to detachment after long cycles. Moreover, existing coating processes often involve high-temperature direct calcination, which easily leads to surface lithium loss and secondary particle agglomeration, resulting in insufficient thermal stability. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a coated and modified ternary cathode material, its preparation method, and its applications. The coated and modified ternary cathode material comprises matrix particles and a modified layer coating the matrix particles; the matrix particles comprise high-nickel lithium nickel cobalt manganese oxide, with the chemical formula LiNi. x Co y Mn zO2, x≥0.8; the modified layer includes Co3O4. By constructing a uniform and conductive Co3O4 coating thin layer on the surface of high-nickel lithium nickel cobalt manganese oxide particles, surface side reactions can be effectively suppressed, lattice distortion can be alleviated, thermal stability, cycle stability and interfacial conductivity can be improved, and the coating layer has good interfacial bonding.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a coated and modified ternary cathode material, comprising matrix particles and a modified layer coating the matrix particles; the matrix particles comprising high-nickel lithium nickel cobalt manganese oxide, with the chemical formula LiNi x Co y Mn z O2, x≥0.8; the modified layer includes Co3O4.

[0007] This invention utilizes a Co3O4-modified layer to coat the surface of high-nickel nickel-cobalt-manganese particles. This layer effectively isolates the electrolyte from the active material particles, suppresses side reactions, reduces excessive SEI film growth, and mitigates microcrack formation in the particles, resulting in a significant reduction in the long-cycle capacity decay rate of the cathode material. The Co3O4 coating also inhibits oxygen evolution at high temperatures, increasing the material's thermal decomposition temperature and thus reducing the risk of thermal runaway in batteries containing this cathode material, improving battery safety. More importantly, Co3O4 itself possesses excellent electronic conductivity, unlike insulating oxide coatings. The Co3O4-containing coating optimizes electron-ion transport channels, reduces interfacial impedance, and exhibits less polarization under high-rate charge-discharge, resulting in superior rate performance. Simultaneously, the modified coating allows the Co element on the surface of the substrate particles to regulate the surface lattice structure, forming a transition layer with the substrate surface to suppress lithium-nickel mixing and reduce Ni... 2+ The carbon dioxide migrates to lithium sites, thereby stabilizing the layered crystal structure, improving initial discharge capacity, and enhancing the adhesion of the coating layer. In summary, this invention effectively suppresses surface side reactions, alleviates lattice distortion, and improves thermal stability, cycle stability, and interfacial conductivity by constructing a uniform and conductive Co3O4 coating layer on the surface of high-nickel lithium nickel cobalt manganese oxide particles. Furthermore, this coating layer exhibits good interfacial adhesion.

[0008] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0009] As a preferred embodiment of the present invention, the modified layer accounts for 0.5% to 2.0% of the mass of the matrix particles, for example, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.0%; and / or, the thickness of the modified layer is 5nm to 20nm, for example, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 13nm, 14nm, 16nm, 18nm, or 20nm, preferably 9.85nm to 12.1nm. The present invention preferably controls the coating amount of the modified layer to 0.5% to 2.0%. With a suitable coating amount, the coating layer thickness is uniform, which can both isolate the electrolyte and achieve surface protection without hindering Li... + The conduction of electrons can achieve the best balance between electron conduction and lithium-ion transport, taking into account both stability and rate performance.

[0010] Preferably, in the X-ray diffraction test of the coated and modified ternary cathode material, I (003) / I (104) ≥1.4920, where I (003) and I (104) These represent the diffraction peak intensities of (003) and (104) in space group R-3m, respectively, for α-NaFeO2 type layered structures. (003) / I (104) A value of ≥1.4920 indicates that the degree of cation mixing in the material is extremely low, which is beneficial for maintaining stable polycrystalline structure characteristics even after long-term cycling.

[0011] In a second aspect, the present invention provides a method for preparing the coated and modified ternary cathode material as described in the first aspect, comprising the following steps: High-nickel ternary hydroxide was mixed and ground with a lithium source, and then subjected to a first calcination to obtain matrix particles including high-nickel lithium nickel cobalt manganese oxide; a cobalt source and a dispersant were prepared to form a cobalt source dispersion. The matrix particles are mixed with the cobalt source dispersion and evaporated to dryness to obtain the coated precursor; The coated precursor is subjected to a second calcination to form a modified layer including Co3O4 on the surface of the matrix particles, thereby obtaining a coated and modified ternary cathode material.

[0012] The preparation method provided by this invention uses liquid-phase adsorption-low-temperature calcination to achieve uniform coating of Co3O4. Unlike traditional solid-phase mixed coating, the modified layer coated by this invention has the advantages of being thinner, more continuous, free of agglomeration, and having a tighter interface with the matrix. Furthermore, the preparation method provided by this invention has a simple process, requires no complex equipment, has a low sintering temperature and low energy consumption, and can be directly adapted to existing ternary material mass production processes, showing good industrialization prospects.

[0013] As a preferred technical solution of the present invention, the amount of lithium is controlled according to the ratio of the molar amount of lithium element provided by the lithium source to the molar amount of high nickel ternary hydroxide as (1.05~1.1):1, for example, it can be 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.10:1, etc.

[0014] Preferably, the lithium source comprises lithium hydroxide monohydrate.

[0015] As a preferred embodiment of the present invention, the first calcination is carried out in an oxygen-containing atmosphere, with a heating rate of 1℃ / min to 8℃ / min. The temperature is first maintained at 500℃ to 650℃ for 4 hours to 7 hours, for example, the temperature can be 500℃, 530℃, 550℃, 580℃, 600℃, 620℃, or 650℃, and the time can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, or 7 hours, etc.; then, it is maintained at 700℃ to 850℃ for 6 hours to 14 hours. For example, the temperature can be 700℃, 730℃, 750℃, 780℃, 800℃, 820℃ or 850℃, etc., and the time can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h or 14h, etc.; preferably, the first calcination is carried out in an oxygen atmosphere, the heating rate is 3℃ / min~5℃ / min, first holding at 550℃~600℃ for 5h~6h, and then holding at 750℃~800℃ for 8h~12h.

[0016] As a preferred technical solution of the present invention, the mass of Co3O4 generated according to the cobalt source theory is controlled at 0.5% to 2.0% of the mass of the matrix particles; for example, it can be 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8% or 2.0%, etc.

[0017] Preferably, the cobalt source comprises cobalt nitrate hexahydrate. This invention preferably uses cobalt nitrate hexahydrate as the cobalt source and anhydrous ethanol as the dispersant. Ethanol has moderate polarity, which can avoid agglomeration of the matrix particles during subsequent mixing and also facilitates uniform adsorption of the cobalt source on the surface of the matrix particles.

[0018] As a preferred embodiment of the present invention, the matrix particles and the cobalt source dispersion are mixed under ultrasonic conditions for a duration of 20 to 40 minutes, such as 20, 23, 25, 28, 30, 33, 35, 38, or 40 minutes. Preferably, the ultrasonic-stirring dispersion process is performed at room temperature to avoid local agglomeration of the cobalt nitrate hexahydrate precursor due to high temperatures. This facilitates the uniform adsorption of the subsequent Co3O4 precursor on the surface of the matrix particles, thereby improving the uniformity of the coating layer.

[0019] Preferably, the dispersant comprises ethanol.

[0020] As a preferred embodiment of the present invention, the method of evaporation includes stirring under oil bath heating at 50℃~60℃, with a stirring speed of 600rpm~1200rpm. For example, the oil bath temperature can be 50℃, 52℃, 54℃, 56℃, 58℃, or 60℃, etc.; the stirring speed can be 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm, or 1200rpm, etc.

[0021] As a preferred technical solution of the present invention, before the second calcination, the coating precursor is dried. The drying temperature is 70℃~90℃ and the drying time is 5h~15h. For example, the drying temperature can be 70℃, 75℃, 80℃, 85℃ or 90℃, and the drying time can be 5h, 7h, 9h, 10h, 11h, 12h, 14h or 15h.

[0022] Preferably, the second calcination is carried out in an oxygen atmosphere, with an oxygen flow rate of 50 mL / min to 300 mL / min, a heating rate of 1℃ / min to 8℃ / min, a temperature of 500℃ to 650℃, and a time of 3h to 8h. For example, the oxygen flow rate can be 50 mL / min, 80 mL / min, 100 mL / min, 150 mL / min, 180 mL / min, 200 mL / min, 220 mL / min, 250 mL / min, or 300 mL / min, etc.; the temperature can be 500℃, 530℃, 550℃, 580℃, 600℃, 620℃, or 650℃, etc. Preferably, the second calcination is carried out in an oxygen atmosphere, with an oxygen flow rate preferably of 100 mL / min to 200 mL / min, a heating rate of 3℃ / min to 5℃ / min, a temperature of 550℃ to 600℃, and a time of 5h to 6h. The preferred temperature for the secondary calcination in this invention is 550℃~600℃. The secondary low-temperature calcination can avoid the destruction of the layered crystal structure of the high-nickel ternary matrix material and the loss of lithium elements. At the same time, it is conducive to the complete decomposition of the cobalt source, especially cobalt nitrate, to generate conductive Co3O4, and ensures that a tight interface bonding layer is formed between the Co3O4 coating layer and the matrix.

[0023] Thirdly, the present invention provides a battery comprising the coated and modified ternary cathode material described in the first aspect or the coated and modified ternary cathode material obtained by the preparation method described in the second aspect.

[0024] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0025] Compared with existing technical solutions, the present invention has at least the following beneficial effects: The modified ternary cathode material provided by this invention, by coating the surface of high-nickel nickel-cobalt-manganese particles with a modified layer containing Co3O4, effectively isolates the electrolyte from the active material particles, suppresses side reactions, reduces excessive SEI film growth, and helps alleviate microcrack formation in the particles, thus significantly reducing the long-cycle capacity decay rate of the cathode material. The Co3O4 coating layer also inhibits oxygen evolution at high temperatures, increases the thermal decomposition temperature of the material, thereby reducing the risk of thermal runaway in batteries containing this cathode material and improving battery safety. More importantly, Co3O4 itself possesses good electronic conductivity, unlike insulating oxide coatings. The Co3O4 coating layer can optimize electron-ion transport channels, reduce interfacial impedance, and exhibit less polarization under high-rate charge-discharge, resulting in excellent rate performance. Simultaneously, the modified coating layer allows the Co element on the surface of the matrix particles to play a role in regulating the surface lattice structure, forming a transition layer with the matrix surface to suppress lithium-nickel mixing and reduce Ni... 2+ The material migrates to lithium sites, thereby stabilizing the layered crystal structure and increasing the initial discharge capacity.

[0026] The preparation method provided by this invention employs a liquid-phase adsorption-low-temperature calcination method to achieve uniform coating of Co3O4 and enhance the bonding between the coating layer and the matrix particles. Unlike traditional solid-phase mixed coating, the modified layer coated by this invention has the advantages of being thinner, more continuous, free of agglomeration, and having a tighter interface with the matrix. Furthermore, the preparation method provided by this invention has a simple process, requires no complex equipment, has a low sintering temperature, and low energy consumption, and can be directly adapted to existing ternary material mass production processes, showing good industrialization prospects. Detailed Implementation

[0027] 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 in any way.

[0028] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0029] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0030] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0031] In this invention, the order in which the steps are written in the methods described in the various embodiments does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any conflict-free order, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0032] Example 1 This embodiment provides a coated and modified ternary cathode material, consisting of matrix particles and a modified layer coating the matrix particles; the matrix particles are high-nickel lithium nickel cobalt manganese oxide, with the chemical formula LiNi. 0.83 Co 0.12 Mn 0.05 O2, the modified layer is Co3O4; the mass of the modified layer accounts for 0.5% of the mass of the matrix particles.

[0033] The preparation method of this coated and modified ternary cathode material includes: S1, high-nickel lithium nickel cobalt manganese oxide precursor (Ni 0.83 Co 0.12 Mn 0.05 (OH)2) is mixed with lithium source lithium hydroxide monohydrate at a molar ratio of 1:1.05 and ground thoroughly to obtain a mixed powder; S2. Place the mixed powder in a tube furnace and heat it to 550°C at 5°C / min under an oxygen atmosphere. Hold it at that temperature for 6 hours to initially form a lithium precursor. Continue to heat it to 780°C at 4°C / min and hold it for 12 hours. Then, cool it naturally to obtain high-nickel lithium nickel cobalt manganese oxide, i.e., matrix particles. S3. Weigh out cobalt nitrate hexahydrate, dissolve it in anhydrous ethanol, and stir magnetically until completely dissolved, based on the mass of the coating layer formed by the target being 1.2% of the mass of the matrix particles, to obtain a cobalt source ethanol dispersion. S4. Add the matrix particles to the above cobalt source ethanol dispersion and ultrasonically disperse for 30 min to obtain a mixed system; S5. Place the mixture in an oil bath and stir rapidly at 1000 rpm at 60°C until the anhydrous ethanol is completely evaporated to obtain powder coated with cobalt salt precursor. S6. The powder coated with the cobalt salt precursor is dried at 80℃ for 12h to remove residual dispersant; then, in an oxygen atmosphere with an oxygen flow rate of 100mL / min, the temperature is increased to 600℃ at 5℃ / min, held for 5h, and then naturally cooled to form a coating layer on the surface of the matrix particles, thus obtaining the coated and modified ternary cathode material.

[0034] Example 2 The difference from Example 1 is that the amount of cobalt nitrate hexahydrate used in step S3 of the preparation method is adjusted so that the coating amount of the formed coating layer is changed from 1.2% of the mass of the matrix particles to 0.2%. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0035] Example 3 The difference from Example 1 is that the amount of cobalt nitrate hexahydrate in step S3 of the preparation method is adjusted so that the coating amount of the formed coating layer is changed from 1.2% of the mass of the matrix particles to 0.5%. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0036] Example 4 The difference from Example 1 is that the amount of cobalt nitrate hexahydrate used in step S3 of the preparation method is adjusted so that the coating amount of the formed coating layer is changed from 1.2% of the mass of the matrix particles to 1%. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0037] Example 5 The difference from Example 1 is that the amount of cobalt nitrate hexahydrate in step S3 of the preparation method is adjusted so that the coating amount of the formed coating layer is adjusted from 1.2% of the mass of the matrix particles to 2%. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0038] Example 6 The difference from Example 1 is that the amount of cobalt nitrate hexahydrate used in step S3 of the preparation method is adjusted so that the coating amount of the formed coating layer is adjusted from 1.2% of the mass of the matrix particles to 2.5%. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0039] Comparative Example 1 The difference from Example 1 is that only the matrix particles obtained in step S2 of Example 1 are used as the positive electrode material, without coating. Except for the above, the other conditions are exactly the same as those in Example 1.

[0040] Comparative Example 2 The difference from Example 1 is that in step S3, the cobalt source is not prepared as a dispersion. Instead, a solid cobalt source is directly used to mix with the matrix particles in step S4 to obtain a mixed system. The remaining steps are then carried out on the mixed system. Except for the above, the other conditions are exactly the same as in Example 1.

[0041] Comparative Example 3 The difference from Example 1 is that in step S3, the cobalt source is replaced with aluminum nitrate, that is, the matrix particles are coated with alumina. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0042] Characterization and testing: I. Characterize the cathode materials obtained in the examples and comparative examples: 1) Measure and count the coating layer thickness by testing the cross-section using an electron scanning microscope; 2) Calculate I by performing X-ray diffraction tests on the cathode materials. (003) / I (104) The results are recorded in Table 1.

[0043] Table 1 II. The positive electrode materials obtained in the examples and comparative examples were mixed with Super-P and PVDF at a mass ratio of 90:5:5, respectively. NMP (N-methylpyrrolidone) was added and stirred to form a slurry. The slurry was coated onto a carbon-coated aluminum foil, dried at 120°C, and then calendered to a thickness of 40 μm to 50 μm. The resulting sheet was then stamped to obtain an electrode (active loading 10 ± 0.3 mg / cm²). 2 Then, using a lithium sheet as the counter electrode, Celgard 2325 as the separator, and 1M LiPF6 in EC / EMC (volume ratio 1:1) as the electrolyte, a coin cell was assembled in an argon glove box. The obtained batteries were subjected to electrochemical tests, and the results are recorded in Table 2.

[0044] Table 2 Combining Table 1 and Table 2, we can see that: (1) Compared with the uncoated Comparative Example 1, the discharge specific capacity and cycle stability of the Co3O4-coated ternary cathode material obtained in Example 1 of the present invention are significantly improved. The discharge specific capacity reaches 222.0 mAh / g, and the capacity retention rate after 250 cycles at 0.5C reaches 36.2%, which are 6.0 mAh / g and 22.5 percentage points higher than Comparative Example 1, respectively. (2) Comparing Example 1 and Comparative Example 1 with Examples 2 to 6, it can be seen that as the coating amount increases, the coating layer thickness also increases, I (003) / I (104)- The trend shows an initial increase followed by a decrease; while the discharge specific capacity of the material first increases and then decreases, and the cycle stability first improves and then tends to stabilize. The above indicates that the modified layer has excellent comprehensive performance in the coating amount range of 0.5% to 2.0%, among which 1.2% coating amount (Example 1) achieves the best balance between capacity and cycle stability, and is the optimal example. (3) Comparing Example 1 with Comparative Example 2, it can be seen that, under the same coating amount, Example 1, which uses liquid phase adsorption process, is superior to Comparative Example 2, which uses solid phase mixed coating, in terms of both capacity and cycle performance. This shows that the preparation method of the present invention can form a more uniform and effective coating layer. (4) Comparing Example 1 with Comparative Example 3, it can be seen that compared with the conventional Al2O3-coated Comparative Example 3, the Co3O4-coated cathode material of the present invention has obvious advantages in rate performance and capacity. The 1C discharge specific capacity is about 14 mAh / g higher, which reflects the dual role of good conductivity and lattice regulation of Co3O4.

[0045] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0047] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A coated and modified ternary cathode material, characterized in that, It includes matrix particles and a modified layer coating the matrix particles; the matrix particles include high-nickel lithium nickel cobalt manganese oxide, with the chemical formula LiNi. x Co y Mn z O2, x≥0.8; the modified layer includes Co3O4.

2. The coated and modified ternary cathode material according to claim 1, characterized in that, The modified layer accounts for 0.5% to 2.0% of the mass of the matrix particles; and / or, the thickness of the modified layer is 5 nm to 20 nm. Preferably, in the X-ray diffraction test of the coated and modified ternary cathode material, I (003) / I (104) ≥1.4920, where I (003) and I (104) The diffraction intensities of the (003) and (104) peaks, respectively, represent the diffraction intensities of the α-NaFeO2 type layered structure in space group R-3m.

3. A method for preparing the coated and modified ternary cathode material according to claim 1 or 2, characterized in that, Includes the following steps: High-nickel ternary hydroxide was mixed and ground with a lithium source, and then subjected to a first calcination to obtain matrix particles including high-nickel lithium nickel cobalt manganese oxide; a cobalt source and a dispersant were prepared to form a cobalt source dispersion. The matrix particles are mixed with the cobalt source dispersion and evaporated to dryness to obtain the coated precursor; The coated precursor is subjected to a second calcination to form a modified layer including Co3O4 on the surface of the matrix particles, thereby obtaining a coated and modified ternary cathode material.

4. The method for preparing the coated and modified ternary cathode material according to claim 3, characterized in that, The dosage is controlled according to the ratio of the molar amount of lithium element provided by the lithium source to the molar amount of high-nickel ternary hydroxide, which is (1.05~1.1):

1. Preferably, the lithium source comprises lithium hydroxide monohydrate.

5. The method for preparing the coated and modified ternary cathode material according to claim 3 or 4, characterized in that, The first calcination is carried out in an oxygen-containing atmosphere, first at 500℃~650℃ for 4h~7h, and then at 700℃~850℃ for 6h~14h.

6. The method for preparing the coated and modified ternary cathode material according to any one of claims 3-5, characterized in that, The amount of Co3O4 generated according to the cobalt source theory is controlled at 0.5% to 2.0% of the mass of the matrix particles; Preferably, the cobalt source comprises cobalt nitrate hexahydrate.

7. The method for preparing the coated and modified ternary cathode material according to any one of claims 3-6, characterized in that, The matrix particles and the cobalt source dispersion are mixed under ultrasonic conditions for 20 min to 40 min. Preferably, the dispersant comprises ethanol.

8. The method for preparing the coated and modified ternary cathode material according to any one of claims 3-7, characterized in that, The method of evaporation includes stirring under oil bath heating at 50℃~60℃, with a stirring speed of 600rpm~1200rpm.

9. The method for preparing the coated and modified ternary cathode material according to any one of claims 3-8, characterized in that, Before the second calcination, the coated precursor is dried at a temperature of 70°C to 90°C for 5 to 15 hours. Preferably, the second calcination is carried out in an oxygen atmosphere, with an oxygen flow rate of 50 mL / min to 300 mL / min, a temperature of 500℃ to 650℃, and a time of 3h to 8h.

10. A battery, characterized in that, The ternary cathode material containing the coating modification as described in claim 1 or 2, or the ternary cathode material containing the coating modification as described in any one of claims 3-9.

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