Composite material, its preparation method, cathode material and secondary battery

Abstract

This application relates to the technical field of electrode active materials and provides a composite material, which includes a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core. The coating layer contains carbon and sulfate. For the composite material provided by this application, the contained lithium-containing metal compound core can be used for lithium supplementation. When the battery is charged in the first cycle, the lithium-containing metal compound can supplement the lithium ions consumed in forming the SEI film on the negative electrode, keeping the lithium ions in the battery system abundant, thereby improving the first charging efficiency and overall electrochemical performance of the battery. The carbon in the coating layer improves the conductivity of the lithium-containing metal compound core, and the sulfate significantly increases the conductivity and reduces the resistance. Therefore, the carbon and sulfate coated on the surface of the lithium-containing metal compound core not only increase the conductivity and structural stability of the material, but also effectively prevent the generation of residual alkali and prevent the electrolyte from eroding the lithium-containing metal compound core, thereby further improving the safety and stability of the material.

Description

Technical Field

[0001] This application belongs to the technical field of electrode active materials, and particularly relates to a composite material, a preparation method thereof, a positive electrode material, and a secondary battery. Background Art

[0002] Adding a small amount of positive electrode lithium supplement additive to the positive electrode slurry is an effective method for supplementing lithium in lithium-ion batteries. However, the existing positive electrode lithium supplement additive materials contain more residual alkali. During the preparation process of the positive electrode slurry, these residual alkalis will react with the binder and are prone to chemical gelation during the stirring process of the positive electrode slurry, thus affecting the quality of the positive electrode sheet. In addition, under high-temperature conditions, the residual alkali will also react with the electrolyte solution to generate gas or solid substances, increasing the gas generation or impedance of the battery and causing a decline in battery performance.

[0003] Therefore, how to develop a lithium supplement material that can effectively prevent the generation and dissolution of residual alkali is an urgent problem to be solved at present. Summary of the Invention

[0004] The purpose of this application is to provide a composite material, a preparation method thereof, a positive electrode material, and a secondary battery, aiming to solve the problem that the existing positive electrode lithium supplement additive is prone to generate residual alkali, resulting in a decline in the electrochemical performance of the battery.

[0005] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In the first aspect, this application provides a composite material, including a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core, and the coating layer contains carbon and sulfate.

[0007] In the second aspect, this application provides a preparation method of a composite material, including the following steps:

[0008] Dissolve a metal source compound and an alkyl sulfate anionic surfactant in a solvent, and perform heat treatment to obtain a solution with micelles coating the metal source;

[0009] After mixing the solution with micelles coating the metal source with a lithium source, perform drying treatment and sintering treatment in sequence to obtain a composite material with carbon and sulfate coating the lithium-containing metal compound core.

[0010] In the third aspect, this application provides a positive electrode material, which contains the composite material provided by this application or a composite material prepared by the preparation method of the composite material provided by this application.

[0011] In the fourth aspect, this application provides a secondary battery, which contains the positive electrode material provided by this application.

[0012] Compared with the prior art, this application has the following beneficial effects:

[0013] The composite material provided in the first aspect of the present application includes a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core. The material of the coating layer contains carbon and sulfate. The contained lithium-containing metal compound core can be used for lithium supplementation. When the battery is charging in the first cycle, the lithium supplementation material can supplement the lithium ions consumed in forming the SEI film on the negative electrode, keeping the lithium ions in the battery system abundant, thereby improving the first charging efficiency and overall electrochemical performance of the battery. The carbon in the coating layer can enhance the conductivity of the lithium-containing metal compound, and the sulfate in the coating layer can significantly increase the conductivity and reduce the resistance. Therefore, carbon and sulfate coated on the surface of the lithium-containing metal compound core not only increase the conductivity and structural stability of the material, but also can effectively prevent the generation of residual alkali and prevent the electrolyte from corroding the lithium-containing metal compound, thereby further improving the safety and stability of the material.

[0014] The preparation method of the composite material provided in the second aspect of the present application is as follows: First, dissolve the metal source compound and the alkyl sulfate anionic surfactant in a solvent, perform heat treatment to obtain a solution with micelles coating the metal source, then mix the solution with micelles coating the metal source with a lithium source, and then perform drying treatment and sintering treatment in sequence to obtain a composite material with carbon and sulfate coating the lithium-containing metal compound core. By using the alkyl sulfate anionic surfactant to in-situ coat the metal source compound and then sintering with the lithium source, the present application can form a uniform and dense carbon and sulfate coating layer on the surface of the lithium-containing metal compound core, and the binding force between the coating layer and the lithium-containing metal compound core is strong, and the material has good structural stability. In addition, the preparation process is simple and controllable, the production cost is low, and it is easy to industrialize.

[0015] The positive electrode material provided in the third aspect of the present application has good conductivity and structural stability because it contains the composite material provided in the present application or the composite material prepared by the preparation method of the composite material provided in the present application.

[0016] The secondary battery provided in the fourth aspect of the present application can improve the electrochemical performance of the secondary battery because it contains the positive electrode material provided in the present application. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is the process flow chart of the preparation method of the composite material provided in the embodiment of the present application. Detailed implementation manners

[0019] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] In the present application, the term "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may indicate: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B may be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0021] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both indicate: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively.

[0022] It should be understood that in various embodiments of the present application, the magnitude of the serial numbers of the above processes does not mean the sequence of execution. Some or all steps can be executed in parallel or sequentially. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0024] The weight of the relevant components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0025] The terms "first" and "second" are for descriptive purposes only, used to distinguish objects such as substances from each other, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0026] In the first aspect of the embodiments of the present application, a composite material is provided, which includes a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core, and the coating layer contains carbon and sulfate.

[0027] The composite material provided by the embodiments of the present application includes a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core, and the material of the coating layer contains carbon and sulfate. The contained lithium-containing metal compound core can be used for lithium supplementation. When the battery is charging in the first cycle, the lithium-containing metal compound core can supplement the lithium ions consumed in forming the SEI film at the negative electrode, so that the lithium ions in the battery system remain abundant, thereby improving the first charging efficiency and overall electrochemical performance of the battery. The carbon in the coating layer can improve the conductivity of the lithium-containing metal compound core, and the sulfate in the coating layer can significantly increase the conductivity and reduce the resistance. Therefore, carbon and sulfate coated on the surface of the lithium-containing metal compound core not only increase the conductivity and structural stability of the material, but also effectively prevent the generation of residual alkali and the erosion of the electrolyte on the lithium-containing metal compound, thereby further improving the safety and stability of the material.

[0028] In an embodiment, the coating layer includes a sulfate layer and a carbon layer, and the sulfate layer is located between the lithium-containing metal compound core and the carbon layer. In other embodiments, the coating layer includes a sulfate layer and a carbon layer, and the carbon layer is located between the lithium-containing metal compound core and the sulfate layer. Among them, the thickness of the sulfate layer is 0.5 - 250 nm, and the thickness of the carbon layer is 0.5 - 50 nm. Within the thickness range of the sulfate layer and the carbon layer provided in this embodiment, the particle size of the composite material can be adjusted, which is beneficial to giving full play to the lithium supplementation effect of the lithium-containing metal compound core, improving the stability of the material, and thus enhancing the first charging efficiency and overall electrochemical performance of the battery. In a specific embodiment, the thickness of the sulfate layer can be, but is not limited to, 0.5 nm, 1 nm, 10 nm, 30 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm. The thickness of the carbon layer can be, but is not limited to, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm.

[0029] In an embodiment, the coating layer includes a first carbon layer, a sulfate layer, and a second carbon layer that are sequentially coated on the surface of the lithium-containing metal compound core from the inside to the outside in the radial direction. Among them, the thickness of the first carbon layer is 0.1 - 100 nm, the thickness of the sulfate layer is 0.6 - 150 nm, and the thickness of the second carbon layer is 0.3 - 50 nm. Within the thickness ranges of the first carbon layer, the sulfate layer, and the second carbon layer provided in this embodiment, the particle size of the composite material can be adjusted, which is beneficial to fully exert the lithium supplementing effect of the lithium-containing metal compound core, improve the stability of the material, and thus enhance the first charge efficiency and overall electrochemical performance of the battery. In a specific embodiment, the thickness of the first carbon layer can be, but is not limited to, 0.1 nm, 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 70 nm, 100 nm. The thickness of the sulfate layer can be, but is not limited to, 0.6 nm, 1 nm, 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 120 nm, 150 nm. The thickness of the second carbon layer can be, but is not limited to, 0.3 nm, 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm.

[0030] In an embodiment, the coating layer is composed of carbon and sulfate doped with each other. Among them, the mass ratio of carbon to sulfate is (0.1 - 0.9):1. Within the mass ratio range of carbon to sulfate provided in this embodiment, the aggregation and growth of the lithium-containing metal compound core during synthesis can be inhibited, the conductivity of the lithium-containing metal compound core can be improved, the irreversible lithium loss at the negative electrode during the first charge and discharge can be compensated, the energy density of the battery can be increased, and the preparation process of doping and coating the lithium-containing metal compound with carbon and sulfate is simple, easy to implement, and conducive to wide promotion and application. In a specific embodiment, the mass ratio of carbon to sulfate can be, but is not limited to, 0.1:1, 0.3:1, 0.6:1, 0.9:1.

[0031] In an embodiment, the thickness of the coating layer is 1 - 300 nm. Within the thickness range of the coating layer provided in the embodiment of the present application, it can not only ensure that the composite material has good processing performance and ensure the timely release of active lithium, but also avoid increasing the battery impedance. In a specific embodiment, the thickness of the coating layer can be, but is not limited to, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 100 nm, 250 nm, 300 nm.

[0032] In an embodiment, the sulfate includes at least one of an alkali metal sulfate and an alkaline earth metal sulfate. Specifically, the alkali metal sulfate is selected from at least one of sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, and francium sulfate; the alkaline earth metal sulfate is selected from at least one of beryllium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate. These alkali metal sulfates and alkaline earth metal sulfates provided in the embodiments of the present application can significantly increase the conductivity of the composite material and reduce the resistance.

[0033] In an embodiment, the lithium-containing metal compound core may include a lithium-rich cathode material and a lithium supplement material. The molecular formula of the lithium-containing metal compound core is Li x A y O z , where A includes at least one of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, Zr, and Al, 1 < x < 10, 0 < y < 4, 0 < z < 8, preferably 1 < x < 7, 1 ≤ y < 4, 1 < z < 5. In a specific embodiment, the molecular formula of the lithium-containing metal compound core may be, but is not limited to, Li2NiO2, Li2CuO2, Li6CoO4, Li5FeO4, Li5AlO4, Li6Co 0.5 Mn 0.5 O4, Li6Ni 0.5 Co 0.5 O4. These lithium-containing metal compounds can be used for lithium supplementation. When the battery is charged in the first cycle, the lithium-containing metal compound can supplement the lithium ions consumed by the negative electrode to form the SEI film, so that the lithium ions in the battery system remain abundant, thereby improving the first charging efficiency and overall electrochemical performance of the battery.

[0034] In an embodiment, the morphology of the lithium-containing metal compound core can be controlled as needed, such as in the form of particles or other morphologies. The lithium-containing metal compound core is preferably in the form of particles, which can be primary particles or secondary particles. The particle size of the lithium-containing metal compound core satisfies: 0.1 μm ≤ D50 ≤ 20 μm, and the particle size of the composite material satisfies: 1 μm ≤ D50 ≤ 25 μm. The specific surface area of the composite material is 0.1 - 35 m 2 / g. Within the ranges of the particle size of the lithium-containing metal compound core, the particle size, and the specific surface area of the composite material provided in the embodiments of the present application, it is beneficial to fully exert the lithium supplementing effect of the lithium-containing metal compound core, improve the stability of the material, thereby enhancing the first charge efficiency and the overall electrochemical performance of the battery. In specific embodiments, the particle size of the lithium-containing metal compound core can be, but is not limited to, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm. The particle size of the composite material can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 21 μm, 22 μm, 23 μm, 14 μm, 25 μm.

[0035] The second aspect of the embodiments of the present application provides a method for preparing a lithium supplementing composite material, including the following steps:

[0036] S10: Dissolve a metal source compound and an alkyl sulfate anionic surfactant in a solvent, and perform heat treatment to obtain a solution with a micelle-coated metal source;

[0037] S20: After mixing the solution with the micelle-coated metal source with a lithium source, perform drying treatment and sintering treatment in sequence to obtain a composite material with a carbon and sulfate-coated lithium-containing metal compound core.

[0038] In the method for preparing the composite material provided in the embodiments of the present application, first dissolve the metal source compound and the alkyl sulfate anionic surfactant in a solvent, perform heat treatment to obtain a solution with a micelle-coated metal source, and then after mixing the solution with the micelle-coated metal source with the lithium source, perform drying treatment and sintering treatment in sequence to obtain a composite material with a carbon and sulfate-coated lithium-containing metal compound core. By using the alkyl sulfate anionic surfactant to in-situ coat the metal source compound and then sintering with the lithium source, a uniform and dense carbon and sulfate coating layer can be formed on the surface of the lithium-containing metal compound core, and the binding force between the coating layer and the lithium-containing metal compound core is strong, and the material structure has good stability. In addition, the preparation process is simple and controllable, the production cost is low, and it is easy to industrialize production.

[0039] In the above step S10, the mass ratio of the metal source compound, the solvent, and the alkyl sulfate anionic surfactant is 1:(0.4 - 2):(0.005 - 0.1). The conditions for heat treatment include: the temperature is 90 - 110 °C, and the time is 1 - 3 h.

[0040] In an embodiment, a metal source compound, a solvent, and an alkyl sulfate anionic surfactant are mixed in a mass ratio of 1:(0.4 - 2):(0.005 - 0.1). The metal source compound and the alkyl sulfate anionic surfactant are dissolved in the solvent to obtain a mixed solution. Then, the mixed solution is reacted at a temperature of 90 - 110 °C for 1 - 3 h. The organic carbon chains in the alkyl sulfate anionic surfactant attract each other and associate together to form micelles, obtaining a solution with micelles coating the metal source. The shape of the micelles can be selected from one of spherical, lamellar, and rod-shaped.

[0041] In an embodiment, the metal source compound includes at least one of metal oxides, metal hydroxides, and metal salts, and the metal element in the metal oxides, metal hydroxides, and metal salts is selected from at least one of Ni (nickel), Co (cobalt), Fe (iron), Cu (copper), Mg (magnesium), Mn (manganese), Cr (chromium), Zn (zinc), Ti (titanium), and Zr (zirconium). For example, the metal oxide in the metal source compound can be nickel oxide, cobalt oxide, iron oxide, copper oxide, manganese oxide, zinc oxide, titanium dioxide, or zirconium oxide; the metal hydroxide can be nickel hydroxide or cobalt hydroxide; and the metal salt can be iron chloride, copper chloride, or magnesium chloride.

[0042] In an embodiment, the number of carbon atoms in the alkyl group of the alkyl sulfate anionic surfactant is 10 - 20. The sulfate in the alkyl sulfate anionic surfactant includes at least one of alkali metal sulfates and alkaline earth metal sulfates. For example, the alkyl sulfate anionic surfactants corresponding to alkali metal sulfates can be sodium decyl sulfate, sodium undecyl sulfate, sodium dodecyl sulfate, sodium tridecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, potassium decyl sulfate, or potassium dodecyl sulfate; and the alkyl sulfate anionic surfactants corresponding to alkaline earth metal sulfates can be magnesium decyl sulfate or magnesium dodecyl sulfate.

[0043] In the above step S20, the lithium source can be selected from one of lithium carbonate and lithium hydroxide. In an embodiment, the conditions for the sintering treatment include: sintering in an inert atmosphere at 600 - 800 °C for 5 - 24 h.

[0044] In an embodiment, the solvent may be selected from at least one of ammonia water, water, ethanol, N-methylpyrrolidone, acetone, ethylene glycol, and methanol. For example, if the solvent is selected from ammonia water or water, a metal source compound and an alkyl sulfate anionic surfactant are dissolved in water or ammonia water to obtain a mixed solution; then the mixed solution is reacted at a temperature of 90 to 110°C for 1 to 3 hours. The organic carbon chains in the alkyl sulfate anionic surfactant aggregate to form a micelle core close to the metal source, and the sulfate forms the outer layer of the micelle, obtaining a solution with the metal source coated by micelles; after mixing the solution with the lithium source and performing a drying treatment, it is sintered in an inert atmosphere at 600 to 800°C for 5 to 24 hours to obtain a composite material with a carbon layer and a sulfate layer sequentially coated on the surface of the lithium-containing metal compound core from the inside to the outside along the radial direction. If the solvent is selected from ethanol, a metal source compound and an alkyl sulfate anionic surfactant are dissolved in ethanol to obtain a mixed solution; then the mixed solution is reacted at a temperature of 90 to 110°C for 1 to 3 hours. The sulfate in the alkyl sulfate anionic surfactant approaches the metal source, obtaining a solution with the metal source coated by micelles; after mixing the solution with the lithium source and performing a drying treatment, it is sintered in an inert atmosphere at 600 to 800°C for 5 to 24 hours to obtain a composite material with a sulfate layer and a carbon layer sequentially coated on the surface of the lithium-containing metal compound core from the inside to the outside along the radial direction. If the solvent is selected from ethanol and water, a metal source compound and an alkyl sulfate anionic surfactant are dissolved in ethanol and water to obtain a mixed solution; then the mixed solution is reacted at a temperature of 90 to 110°C for 1 to 3 hours to obtain a solution with the metal source coated by micelles; after mixing the solution with the lithium source and performing a drying treatment, it is sintered in an inert atmosphere at 600 to 800°C for 5 to 24 hours to obtain a composite material with a first carbon layer, a sulfate layer, and a second carbon layer sequentially coated on the surface of the lithium-containing metal compound core from the inside to the outside along the radial direction or a composite material with a carbon and sulfate inter-doped layer coated on the surface of the lithium-containing metal compound core.

[0045] In the third aspect of the embodiments of the present application, a cathode material is provided. The cathode material contains the composite material provided by the present application or a composite material prepared by the preparation method of the composite material provided by the present application.

[0046] The cathode material provided by the embodiments of the present application, because it contains the composite material provided by the present application or a composite material prepared by the preparation method of the composite material provided by the present application, therefore, the cathode material has good electrical conductivity and structural stability.

[0047] In the fourth aspect of the embodiments of the present application, a secondary battery is provided. The secondary battery contains the cathode material provided by the present application.

[0048] The secondary battery provided by the embodiments of the present application, because it contains the cathode material provided by the present application, therefore, it can improve the electrochemical performance of the secondary battery.

[0049] The following will be described in conjunction with specific embodiments.

[0050] Embodiment 1

[0051] This embodiment provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li2NiO2, and a carbon layer and a sodium sulfate layer sequentially coated on the surface of Li2NiO2, and the carbon layer is located between the lithium-containing metal compound core and the sodium sulfate layer.

[0052] The preparation method of the composite material of this embodiment includes the following steps:

[0053] S10: Disperse 5 g of nickel oxide in 4.5 g of ethanol, add 0.025 g of sodium dodecyl sulfate dissolved in 2 g of water (the content of sodium sulfate anionic surfactant accounts for 0.5 wt% of the mass of nickel oxide), and then react at a temperature of 90 °C for 2 h to obtain a solution of micelle-coated nickel oxide;

[0054] S20: Mix the solution of micelle-coated nickel oxide with a lithium source and then dry it, and then sinter it in a nitrogen atmosphere at 650 °C for 6 h, and naturally cool it to obtain a composite material with a carbon layer and a sodium sulfate layer coated on Li2NiO2.

[0055] After testing, the particle size of the Li2NiO2 inner core is 1.34 μm, the thickness of the carbon layer is 0.5 - 50 nm, the thickness of the sodium sulfate layer is 0.5 - 250 nm, the D50 particle size of the composite material is 1.35 μm, and the specific surface area of the composite material is 0.56 m 2 / g.

[0056] Embodiment 2

[0057] This embodiment provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li2CuO2, and a carbon layer and a sodium sulfate layer sequentially coated on the surface of Li2CuO2, and the sodium sulfate layer is located between the lithium-containing metal compound core and the carbon layer.

[0058] The preparation method of the composite material of this embodiment includes the following steps:

[0059] S10: Disperse 5 g of copper hydroxide in 4.5 g of water, add 0.025 g of sodium dodecyl sulfate dissolved in 2 g of ethanol (the content of sodium sulfate anionic surfactant accounts for 0.5 wt% of the mass of copper hydroxide), and then react at a temperature of 90 °C for 2 h to obtain a solution of micelle-coated copper hydroxide;

[0060] S20: Mix the solution of micelle-coated copper hydroxide with a lithium source and then dry it, and then sinter it in a nitrogen atmosphere at 650 °C for 6 h, and naturally cool it to obtain a composite material with a carbon layer and a sodium sulfate layer coated on Li2CuO2.

[0061] After detection, the particle size of the Li2CuO2 core is 1.44 μm, the thickness of the carbon layer is 0.5 - 50 nm, the thickness of the sodium sulfate layer is 0.5 - 250 nm, the D50 particle size of the composite material is 1.45 μm, and the specific surface area of the composite material is 0.61 m 2 / g.

[0062] Example 3

[0063] This example provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li6CoO4 and a carbon layer and a sodium sulfate layer sequentially coated on the surface of Li6CoO4, and the carbon layer is located between the lithium-containing metal compound core and the sodium sulfate layer.

[0064] The preparation method of the composite material in this example includes the following steps:

[0065] S10: Dissolve 5 g of cobalt oxide in 4.5 g of water, add 0.0225 g of sodium dodecyl sulfate dissolved in 2 g of water (the content of the sodium sulfate anionic surfactant accounts for 0.45 wt% of the mass of cobalt oxide), and then react at a temperature of 90 °C for 2 h to obtain a solution of micelle-coated cobalt oxide;

[0066] S20: Mix the solution of micelle-coated cobalt oxide with a lithium source, dry it, and then sinter it in a nitrogen atmosphere at 700 °C for 7 h, and cool it naturally to obtain a composite material of carbon and sodium sulfate-coated Li6CoO4.

[0067] After detection, the particle size of the Li6CoO4 core is 1.44 μm, the thickness of the carbon layer is 0.5 - 50 nm, the thickness of the sodium sulfate layer is 0.5 - 250 nm, the D50 particle size of the composite material is 1.45 μm, and the specific surface area of the composite material is 0.56 m 2 / g.

[0068] Example 4

[0069] This example provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li6Co 0.5 Mn 0.5 O4 and a first carbon layer, a sodium sulfate layer, and a second carbon layer sequentially coated on the surface of Li6Co 0.5 Mn 0.5 O4 along the radial direction from the inside to the outside.

[0070] The preparation method of the composite material in this example includes the following steps:

[0071] S10: Dissolve 2.5 g of cobalt oxide and 2.5 g of manganese oxide in 4.5 g of water, add 0.25 g of sodium dodecyl sulfate (the content of sulfate anion surfactant accounts for 5 wt% of the mass of cobalt oxide and manganese oxide) dissolved in 2 g of ethanol, and then react at 90 °C for 2 h to obtain a solution of micelle-coated cobalt-manganese oxide;

[0072] S20: Mix the solution of micelle-coated cobalt-manganese oxide with a lithium source and then dry it, and then sinter it in a nitrogen atmosphere at 700 °C for 7 h and cool it naturally to obtain a composite material coated with a first carbon layer, a sodium sulfate layer, and a second carbon layer of Li6Co 0.5 Mn 0.5 O4.

[0073] After detection, the particle size of the Li6Co 0.5 Mn 0.5 O4 core is 1.44 μm, the thickness of the first carbon layer is 0.5 - 50 nm, the thickness of the sodium sulfate layer is 0.5 - 250 nm, the thickness of the second carbon layer is 0.5 - 50 nm, the D50 particle size of the composite material is 1.45 μm, and the specific surface area of the composite material is 0.61 m 2 / g.

[0074] Example 5

[0075] This example provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li6Ni 0.5 Co 0.5 O4 and a carbon layer and a magnesium sulfate layer sequentially coated on the surface of Li6Ni 0.5 Co 0.5 O4, and the carbon layer is located between the lithium-containing metal compound core and the magnesium sulfate layer.

[0076] The preparation method of the composite material in this example includes the following steps:

[0077] S10: Dissolve 2.5 g of cobalt oxide and 2.5 g of nickel oxide in 4.5 g of water, add 0.3 g of magnesium dodecyl sulfate (the content of magnesium sulfate anion surfactant accounts for 6 wt% of the mass of cobalt oxide and nickel oxide) dissolved in 2 g of water, and then react at 90 °C for 2 h to obtain a solution of micelle-coated nickel-cobalt oxide;

[0078] S20: Mix the solution of micelle-coated nickel-cobalt oxide with a lithium source and then dry it, and then sinter it in a nitrogen atmosphere at 700 °C for 7 h and cool it naturally to obtain a composite material coated with carbon and magnesium sulfate of Li6Ni 0.5 Co 0.5 O4.

[0079] After detection, Li6Ni 0.5 Co 0.5The particle size of the O4 core is 1.44 μm, the thickness of the carbon layer is 0.5 - 50 nm, the thickness of the magnesium sulfate layer is 0.5 - 250 nm, the D50 particle size of the composite material is 1.5 μm, and the specific surface area of the composite material is 0.64 m 2 / g.

[0080] Example 6

[0081] This example provides a composite material and a preparation method thereof. The composite material includes a lithium-containing metal compound core Li6CoO4 and a carbon layer and a potassium sulfate layer sequentially coated on the surface of Li6CoO4, and the carbon layer is located between the lithium-containing metal compound core and the magnesium sulfate layer.

[0082] The preparation method of the composite material in this example includes the following steps:

[0083] S10: Dissolve 5 g of cobalt oxide in 4.5 g of water, add 0.025 g of potassium dodecyl sulfate (the content of the sulfate anion surfactant of potassium sulfate accounts for 13 wt% of the mass of cobalt oxide) dissolved in 2 g of water, and then react at a temperature of 90 °C for 2 h to obtain a solution of micelle-coated cobalt oxide;

[0084] S20: Mix the solution of micelle-coated cobalt oxide with a lithium source and then dry it, and then sinter it in a nitrogen atmosphere at 700 °C for 7 h and cool it naturally to obtain a composite material with a carbon layer and a potassium sulfate layer coated on Li6CoO4.

[0085] After testing, the particle size of the Li6CoO4 core is 1.44 μm, the thickness of the carbon layer is 0.5 - 50 nm, the thickness of the potassium sulfate layer is 0.5 - 250 nm, the D50 particle size of the composite material is 1.71 μm, and the specific surface area of the composite material is 0.81 m 2 / g.

[0086] Comparative Example 1

[0087] This comparative example provides a lithium supplement material Li2NiO2.

[0088] The preparation method of the lithium supplement material Li2NiO2 in this comparative example includes the following steps:

[0089] Mix nickel oxide with a lithium source, and then sinter it in a nitrogen atmosphere at 650 °C for 6 h and cool it naturally to obtain a lithium supplement material of Li2NiO2.

[0090] Comparative Example 2

[0091] This comparative example provides a lithium-containing metal compound Li2CuO2.

[0092] The preparation method of the lithium-containing metal compound Li2CuO2 in this comparative example includes the following steps:

[0093] Mix copper oxide with a lithium source, then sinter at 650 °C in a nitrogen atmosphere for 6 h, and cool naturally to obtain a lithium-containing metal compound of Li2CuO2.

[0094] Comparative Example 3

[0095] This comparative example provides a lithium-containing metal compound Li6CoO4.

[0096] The preparation method of the lithium-containing metal compound Li6CoO4 in this comparative example includes the following steps:

[0097] Mix cobalt oxide with a lithium source, then sinter at 650 °C in a nitrogen atmosphere for 6 h, and cool naturally to obtain a lithium-containing metal compound of Li6CoO4.

[0098] Comparative Example 4

[0099] This comparative example provides a lithium-containing metal compound Li6Co 0.5 Mn 0.5 O4.

[0100] The lithium-containing metal compound Li6Co 0.5 Mn 0.5 The preparation method of O4 includes the following steps:

[0101] Mix cobalt oxide, manganese oxide with a lithium source, then sinter at 750 °C in a nitrogen atmosphere for 6 h, and cool naturally to obtain a lithium-containing metal compound of Li6Co 0.5 Mn 0.5 O4.

[0102] Comparative Example 5

[0103] This comparative example provides a lithium-containing metal compound Li6Ni 0.5 Co 0.5 O4.

[0104] The lithium-containing metal compound Li6Ni 0.5 Co 0.5 The preparation method of O4 includes the following steps:

[0105] Mix cobalt oxide, nickel oxide with a lithium source, then sinter at 750 °C in a nitrogen atmosphere for 6 h, and cool naturally to obtain a lithium-containing metal compound of Li6Ni 0.5 Co 0.5 O4.

[0106] Relevant performance test and analysis:

[0107] 1. Lithium-ion battery assembly:

[0108] The composite materials provided in the above Examples 1-6 and the lithium-containing metal compounds provided in Comparative Examples 1-5 were assembled into a positive electrode and a lithium-ion battery respectively according to the following methods:

[0109] The composite materials provided in Examples 1-2 and the lithium-containing metal compounds provided in Comparative Examples 1-2 were respectively mixed and ball-milled with polyvinylidene fluoride and SP-Li according to a mass ratio of 95:3:2 to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil, roll-pressed, and vacuum-dried overnight at a temperature of 110°C to obtain a positive electrode sheet;

[0110] The composite materials provided in Examples 3-6 and the lithium-containing metal compounds provided in Comparative Examples 3-5 were respectively mixed with the LiFePO4 positive electrode material according to a mass ratio of 95:5 to obtain a mixture. The mixture, polyvinylidene fluoride, and SP-Li were mixed and ball-milled according to a mass ratio of 95:3:2 to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil, roll-pressed, and vacuum-dried overnight at a temperature of 110°C to obtain a positive electrode sheet;

[0111] Negative electrode: Lithium metal sheet;

[0112] Electrolyte: Ethylene carbonate and ethyl methyl carbonate were mixed according to a volume ratio of 3:7, and LiPF6 was added to form an electrolyte with a concentration of 1 mol / L of LiPF6;

[0113] Separator: Polypropylene microporous separator;

[0114] Assembly of lithium-ion battery: A lithium-ion battery was assembled in an inert atmosphere glove box according to the structure of lithium metal sheet - separator - electrolyte - positive electrode sheet.

[0115] 2. Electrochemical performance test and analysis of lithium-ion battery:

[0116] The batteries with the positive electrode sheets containing the composite materials provided in Examples 1-6 were respectively denoted as Examples S1-S6, and the batteries with the lithium-containing metal compounds in Comparative Examples 1-5 were respectively denoted as Comparative Examples DS1-DS5. The first charge-discharge test was carried out at 0.066C, and the test voltage was 2.5V - 4.3V. Then, a 200-cycle test was carried out at 2C, and the test voltage was 2.5V - 3.75V. The test results of the electrochemical performance of the batteries are shown in Table 1 below:

[0117] Table 1

[0118]

[0119] As can be seen from Table 1, the initial charge-discharge specific capacity and capacity retention rate of Examples S1 to S5 are significantly higher than those of Comparative Examples DS1 to DS5, indicating that the composite materials provided in the embodiments of the present application can improve the conductivity and structural stability of the lithium supplement material due to the presence of carbon and sulfate coating layers, and can also effectively prevent the generation of residual alkali and the erosion of the electrolyte on the lithium supplement material, thereby effectively improving its electrochemical performance. In addition, since the content of the coating layer in Examples S3 and S6 is not within the range defined in the present application, their electrochemical performance is slightly worse than that of Examples S1, S2, S4, and S5.

[0120] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A composite material, characterized in that, It includes a lithium-containing metal compound core and a coating layer coated on the surface of the lithium-containing metal compound core. The material of the coating layer contains carbon and sulfate; the coating layer is prepared by using a solution of micelle-coated metal source. The preparation method of the solution of micelle-coated metal source is: dissolving a metal source compound and an alkyl sulfate anionic surfactant in a solvent and performing heat treatment; wherein, the solvent in the solution of micelle-coated metal source is selected from ammonia water or water. The obtained coating layer includes a sulfate layer and a carbon layer, and the carbon layer is located between the lithium-containing metal compound core and the sulfate layer; or, wherein, the solvent in the solution of micelle-coated metal source is selected from ethanol. The obtained coating layer includes a sulfate layer and a carbon layer, and the sulfate layer is located between the lithium-containing metal compound core and the carbon layer; or, wherein, the solvent in the solution of micelle-coated metal source is selected from ethanol and water. The obtained coating layer includes a first carbon layer, a sulfate layer, and a second carbon layer coated on the surface of the lithium-containing metal compound core in sequence from inside to outside along the radial direction; or, the coating layer is composed of carbon and sulfate doped with each other.

2. The composite material according to claim 1, characterized in that, The sulfate includes at least one of alkali metal sulfates and alkaline earth metal sulfates.

3. The composite material according to claim 2, wherein, The alkali metal sulfate is selected from at least one of sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, and francium sulfate; and / or The alkaline earth metal sulfate is selected from at least one of beryllium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate.

4. The composite material according to claim 1, characterized in that The molecular formula of the lithium metal compound core is Li x A y O z , where A includes at least one of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, Zr, 1 < x < 10, 0 < y < 4, 0 < z < 8.

5. The composite material according to any one of claims 1 to 4, characterized in that, The particle size of the lithium-containing metal compound core satisfies: 0.1 μm ≤ D50 ≤ 20 μm; and / or The thickness of the coating layer is 1 - 300 nm; and / or The particle size of the composite material satisfies: 1 μm ≤ D50 ≤ 25 μm; and / or The specific surface area of the composite material is 0.1~35 m 2 / g.

6. A method for preparing the composite material according to any one of claims 1 to 5, characterized in that, It includes the following steps: Dissolving a metal source compound and an alkyl sulfate anionic surfactant in a solvent and performing heat treatment to obtain a solution of micelle-coated metal source; After mixing the solution of micelle-coated metal source with a lithium source, performing drying treatment and sintering treatment in sequence to obtain a composite material with a carbon and sulfate-coated lithium-containing metal compound core.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the metal source compound, the solvent, and the alkyl sulfate anionic surfactant is 1:(0.4 - 2):(0.005 - 0.1).

8. The preparation method according to claim 6, characterized in that, The metal source compound includes at least one of metal oxides, metal hydroxides, and metal salts, and the metal elements in the metal oxides, the metal hydroxides, and the metal salts are selected from at least one of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, and Zr; and / or, The number of carbon atoms in the alkyl group of the alkyl sulfate anionic surfactant is 10 - 20; and / or The sulfate in the alkyl sulfate anionic surfactant includes at least one of alkali metal sulfates and alkaline earth metal sulfates.

9. The preparation method according to any one of claims 6-8, characterized in that, The conditions of the heat treatment include: the temperature is 90 - 110°C and the time is 1 - 3 h; and / or The conditions of the sintering treatment include: sintering for 5 - 24 h in an inert atmosphere at 600 - 800°C.

10. A cathode material, characterized in that, The positive electrode material contains the composite material described in any one of claims 1 to 5 or the composite material prepared by the preparation method of the composite material described in any one of claims 6 to 9.

11. A secondary battery, characterized in that, The secondary battery contains the positive electrode material described in claim 10.

Images