Micron hollow sphere structure sodium ion battery positive electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of battery positive electrode materials, and discloses a sodium ion battery positive electrode material with a micron hollow sphere structure and a preparation method. The preparation method comprises the following steps: fully grinding and mixing compounds or salts of manganese, iron and nickel with a sodium source according to a stoichiometric ratio to obtain a premix with uniform components and uniform particle size distribution; mixing the obtained premix with a dispersing agent to obtain premix slurry; carrying out spray drying on the obtained premix slurry to obtain a raw material with a micron spherical structure; and loading the obtained spherical raw material into a sagger, and carrying out high-temperature calcination to obtain the positive electrode material with the hollow sphere structure. According to the positive electrode material of the hollow sphere structure, the ion migration path of sodium ions in the charging and discharging process is greatly shortened in a battery, the contact area of a positive electrode active substance, a conductive agent and an electrolyte is greatly increased, and the prepared material has the advantages of being good in capacity exertion and high in rate capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials for batteries, and particularly relates to a sodium-ion battery cathode material with a micron hollow sphere structure and a preparation method thereof. Background Art

[0002] Energy storage and conversion have become a major demand in modern society. Lithium-ion batteries are widely used in various electrical equipment due to their excellent electrical energy storage and conversion performance. However, due to the limited storage of lithium resources, their wider application is restricted. Sodium, as a homologous element of lithium, has similar chemical properties to lithium and is abundant in the earth's crust, making sodium-ion batteries a favorable alternative to lithium-ion batteries. As the main component for storing energy in the battery, the cathode material has become a research hotspot, and the preparation of the cathode material is crucial.

[0003] Among the cathode materials for sodium-ion batteries, layered oxide materials have the advantages of high theoretical capacity and wide electrochemical window. At the same time, due to their production process being similar to that of ternary materials for lithium-ion batteries and the equipment being universal, they have become one of the materials with the fastest development. However, since the sodium ion radius is 34.21% larger than the lithium ion radius, its migration speed is slow during charge and discharge, resulting in poor rate performance of the battery and serious attenuation of electrical performance due to the collapse of the material structure after long-term use.

[0004] Researchers often improve the electrochemical performance of materials by controlling and changing the bulk phase structure of the materials.

[0005] In the invention patent "A micron hollow porous composite spherical sodium-ion battery cathode material and its preparation method" (publication number CN111180689A, publication date December 30, 2019), the invention discloses the preparation of a precursor of nickel cobalt manganese by the carbonate co-precipitation method and then by high-temperature calcination.

[0006] In the invention patent "A polypyrrole-coated sodium manganate hollow sphere electrode material, its preparation method and application" (publication number CN109980209A, publication date April 10, 2019), the invention discloses the preparation of sodium manganate hollow spheres by pre-preparing a manganese dioxide hollow sphere precursor and a sodium source for high-temperature calcination, and then by surface coating with pyrrole.

[0007] The preparation methods of the cathode materials in the above inventions have the disadvantages of complex preparation processes, long flowcharts, and lack of economy in the materials used. Summary of the Invention

[0008] To overcome the problems existing in the related technologies, the disclosed embodiments of the present invention provide a sodium-ion battery cathode material with a micron hollow sphere structure and a preparation method thereof, specifically relating to a micron-sized hollow spherical sodium-ion battery layered oxide cathode material and its preparation method.

[0009] The technical solution is as follows: A method for preparing a cathode material for a sodium-ion battery with a micron hollow sphere structure, comprising:

[0010] S1, thoroughly grinding and mixing a compound or salt of manganese, iron, and nickel with a sodium source according to a stoichiometric ratio to obtain a premix with uniform composition and uniform particle size distribution;

[0011] S2, mixing the obtained premix with a dispersant to obtain a premix slurry;

[0012] S3, spray-drying the obtained premix slurry to obtain a green material with a spherical structure of micron size;

[0013] S4, loading the obtained green material into a sagger and obtaining a cathode material Na X Ni a Fe b Mn 1-a-b O2, where 0 < X ≤ 1.1, 0 < a ≤ 1, 0 < b ≤ 1.

[0014] In step S1, the method of grinding and mixing is sand grinding or planetary ball milling, where the ball-to-material ratio is 1:1 to 10, the solid-to-liquid ratio is 1:0.8 to 2, and the mixing time is 0.5 to 8 h.

[0015] In step S1, the particle size of the premix obtained by grinding and mixing is 0.1 to 10 microns.

[0016] In step S2, the dispersant used is water or ethanol, the mass ratio of the premix to the dispersant is 1:1 to 2, and they are mixed evenly by stirring, and the stirring time is greater than 30 min.

[0017] In step S3, the particle size of the green material obtained by spray-drying is 0.1 to 50 microns.

[0018] In step S3, the obtained green material has a spherical morphology and a hollow structure, with a rough surface and no impurities.

[0019] In step S4, the calcination atmosphere is air or oxygen atmosphere, the calcination temperature is 700 to 1000 °C, the calcination time is 10 to 28 h, and the obtained cathode material has a hollow sphere organizational structure, and the shell layer is composed of granular single crystals.

[0020] Another object of the present invention is to provide a cathode material for a sodium-ion battery with a micron hollow sphere structure, which is prepared by the method for preparing a cathode material for a sodium-ion battery with a micron hollow sphere structure. This material has a spherical morphology and a micron-level hollow structure, and the shell layer is self-assembled by granular single crystals.

[0021] Furthermore, the battery prepared from the cathode material of the micron hollow sphere structure is applied to motor vehicles.

[0022] Furthermore, the battery prepared from the cathode material of the micron hollow sphere structure is applied to engineering production robots.

[0023] Combining all the above technical solutions, the beneficial effects of the present invention are as follows:

[0024] The cathode material of the present invention has a spherical morphology and a hollow structure. The surface layer is a shell assembled by granular single crystals, and the chemical formula is Na X Ni a Fe b Mn 1-a-b O2, where 0 < X ≤ 1.1, 0 < a ≤ 1, 0 < b ≤ 1. The cathode material with a hollow sphere structure in the present invention greatly shortens the ion migration path of sodium ions during charge and discharge in the battery, and greatly improves the contact area between the cathode active material, the conductive agent and the electrolyte. The material prepared by this invention has the advantages of good capacity performance and high rate performance.

[0025] The present invention selects commonly used raw materials and prepares the precursor through simple mechanical grinding and mixing without the use of precipitants and complexing agents, and has no requirements for temperature and pH. The process flow is simple and efficient. Spray drying forms a hollow structure. Using the non-template method, the process is simple and efficient and is easy to industrialize. The prepared cathode material with a hollow sphere structure has a larger specific surface area compared with the solid structure material, which is beneficial to the full contact between the active material, the conductive agent and the electrolyte, and provides more active sites for the electrochemical reaction. The granular single crystals on the surface provide a shorter transmission path for the diffusion of sodium ions, which is thus beneficial to improving the rate performance of the material.

[0026] The present invention provides a new cathode material, its preparation method and idea for improving the charge and discharge speed and rate performance of new energy secondary batteries. Especially for instruments and equipment, power tools, etc. that require instant large current and high-power charge and discharge, it has great commercial value in this application scenario. At present, the development direction of battery materials in the industry is mostly high energy density and long cycle life. There are few reports on battery materials for large current charge and discharge and instant high-power release. By specially designing the microscopic morphology of the material, the present invention enables it to have a hollow structure and a spherical morphology, and the shell layer has a hollow structure, improving the large current charge and discharge ability and rate performance of the battery material. This technical solution fills the technical gap in this aspect in the industry. The technical solution of the present invention solves the technical problems of controlling the spherical structure and microscopic morphology in battery materials, and prepares a material with a hollow structure, a spherical morphology, and a hollow shell layer, providing a solution and technology for controlling and adjusting the microscopic structure and morphology of battery materials. Brief Description of the Drawings

[0027] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present disclosure, and are used together with the specification to explain the principles of the present disclosure;

[0028] Figure 1 It is a flow chart of the preparation method of the cathode material of the sodium-ion battery with a micron hollow sphere structure provided by an embodiment of the present invention;

[0029] Figure 2 It is a scanning electron microscope picture of the cathode material of the sodium-ion battery with a micron hollow sphere structure obtained in Example 3 of the present invention;

[0030] Figure 3 It is a scanning electron microscope picture of the cathode material of the sodium-ion battery with a micron hollow sphere obtained in Example 4 of the present invention;

[0031] Figure 4 It is a scanning electron microscope picture of the cathode material of the sodium-ion battery obtained in Comparative Example 1 of the present invention. Detailed Embodiments

[0032] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0033] The innovation of the present invention lies in that: the present invention prepares a micron-scale material with a hollow structure and a spherical morphology through a simple spray drying process, which greatly increases its specific surface area compared with the bulk material, increases the contact interface between the active material and the electrolyte, and at the same time shortens the transmission path of sodium ions during charge and discharge, improving the fast charge and discharge ability of the material.

[0034] Example 1, as Figure 1 shown, the preparation method of the cathode material of the sodium-ion battery with a micron hollow sphere structure provided by the embodiment of the present invention includes the following steps:

[0035] S1, fully grinding and mixing the compounds or salts of manganese, iron, and nickel with the sodium source according to the stoichiometric ratio to obtain a premix with uniform composition and uniform particle size distribution;

[0036] S2, mixing the obtained premix with a dispersant to obtain a premix slurry;

[0037] S3, performing spray drying on the obtained premix slurry to obtain a green material with a micron-sized spherical structure;

[0038] S4. Load the obtained green material into a sagger and obtain a cathode material Na X Ni a Fe b Mn 1-a-b O2, where 0 < X ≤ 1.1, 0 < a ≤ 1, 0 < b ≤ 1.

[0039] Exemplarily, the methods adopted for grinding and mixing in step S1 include but are not limited to sand grinding or planetary ball milling. Among them, the ball-to-material ratio is 1:1 - 10, preferably 1:3 - 6; the solid-to-liquid ratio is 1:0.8 - 2, preferably 1:1 - 1.5; and the mixing time is 0.5 - 8 h, preferably 0.5 - 4 h.

[0040] Another exemplarily, the particle size of the premix obtained by grinding and mixing in step S1 is 0.1 - 10 μm, preferably 0.1 - 5 μm; D[3,2] is 0.2 - 0.4 μm; and D[4,3] is 0.3 - 0.4 μm. D[3,2] and D[4,3] are two expressions of the same material index, referring to the particle size distribution range.

[0041] Exemplarily, the dispersant used in step S2 is water or ethanol. The mass ratio of the premix to the dispersant is 1:1 - 2, preferably 1:1 - 1.5. Mix them evenly by stirring, and the stirring time is greater than 30 min.

[0042] Exemplarily, the particle size of the green material obtained by spray drying in step S3 is 0.1 - 50 μm, preferably 1 - 20 μm. It has a spherical morphology and a hollow structure, the surface is relatively rough, and there are no obvious impurities.

[0043] Exemplarily, the calcination atmosphere in step S4 is air or oxygen atmosphere, the calcination temperature is 700 - 1000 °C, and the calcination time is 10 - 28 h. The obtained cathode material has a hollow sphere organizational structure, and the shell layer is composed of granular single crystals.

[0044] As can be seen from the above embodiments, the cathode material prepared by the method of the present invention has a unique spherical hollow structure formed by self-assembly. The surface is composed of granular single crystals, the shell layer has a hollow structure, and the porosity of the shell layer is more than 10%. Using the material prepared by this method as the cathode material of a sodium-ion battery has the characteristics of a short sodium-ion diffusion path and a high specific surface area, that is, BET > 0.5 m 2 / g. The high specific surface area is beneficial to the full contact of the active material with the electrolyte and the conductive agent, improving the rate performance of the material. This preparation method is simple and can be directly produced using existing production lines, having great practical use value and social promotion value.

[0045] Example 2: The present invention provides a micron hollow sphere structured sodium ion battery cathode material, which has a spherical morphology and a micron-level hollow structure, and the shell is self-assembled by granular single crystals, and the chemical formula is Na X Ni a Fe b Mn 1-a- b O2, where 0<X≤1.1, 0<a≤1, 0<b≤1.

[0046] Embodiment 3, the preparation method of the micron hollow sphere structure sodium ion battery positive electrode material provided by the embodiment of the present invention comprises:

[0047] (1) Weigh 32.1 g of sodium carbonate, 19.05 g of nickel hydroxide, 16.2 g of ferric oxide, and 18.5 g of manganese dioxide, respectively, and put them into ethanol of equal mass to form a slurry, and transfer them into a planetary ball mill for thorough mixing and grinding. The ball-to-material ratio is 1:1, and the grinding time is 6 h. Finally, a premix with a particle size of about 2 μm is obtained.

[0048] (2) The premix and water are prepared into a slurry in a mass ratio of 1:1 and stirred thoroughly, and the mixture is passed through a 200-mesh sieve to remove foreign particles, and then spray-dried by a spray drying device, wherein the spray drying inlet temperature is 220° C. and the outlet temperature is 110° C. to obtain a dry material.

[0049] (3) The raw material obtained by spraying is placed in an alumina sagger and placed in a muffle furnace for sintering. The temperature is raised to 950°C at a rate of 3°C / min and then kept at this temperature for 24 hours. The temperature is naturally cooled to room temperature to obtain a sodium ion battery positive electrode material NaNi with a micron hollow sphere structure. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0050] The samples obtained in this embodiment were tested by scanning electron microscope. Figure 2 .Depend on Figure 2 It can be seen that the obtained positive electrode material has a spherical morphology with a hollow structure, and the surface of the spherical shell is self-assembled by small single crystal particles with a thickness of about 500nm.

[0051] Embodiment 4, the preparation method of the micron hollow sphere structure sodium ion battery positive electrode material provided by the embodiment of the present invention comprises:

[0052] 1) Weigh 32.1g of sodium carbonate, 12.7g of nickel hydroxide, 10.8g of ferric oxide, and 37.1g of manganese dioxide into water of equal mass to form a slurry, and grind and mix them using a sand mill. The ball-to-material ratio is 1:1, and the sand milling time is 2h. Finally, a premix with a particle size of about 1μm is obtained.

[0053] 2) Prepare a slurry by mixing the premix and water at a mass ratio of 1:2 and stir well. Pass it through a 200-mesh sieve and perform spray drying treatment using a spray drying device. The inlet temperature of the spray drying is 200 °C and the outlet temperature is 120 °C to obtain the dried material.

[0054] 3) Load the as-sprayed raw material into an alumina crucible and place it in a muffle furnace for sintering. Heat it at a heating rate of 3 °C / min to 920 °C and then hold for 20 h, and cool it to room temperature in the furnace to obtain the cathode material of sodium ion battery with a micron hollow sphere structure, NaNi 0.2 Fe 0.2 Mn 0.6 O2.

[0055] Perform a scanning electron microscope test on the cathode material prepared in this example, and the results are shown in the appendix Figure 3 . It can be seen from Figure 3 that the obtained cathode material has a spherical morphology with a hollow structure.

[0056] For the comparative example, the preparation method of the existing cathode material includes:

[0057] (a) Weigh 32.1 g of sodium carbonate, 19.05 g of nickel hydroxide, 16.2 g of iron(III) oxide, and 18.5 g of manganese dioxide and put them into ethanol of the same mass to form a slurry, and use a planetary ball mill to grind and mix the materials. The ball-to-material ratio is 1:1 and the grinding time is 6 h to finally obtain a premix with a particle size of about 1 μm.

[0058] (b) Different from Example 3, this comparative example does not use spray drying treatment. Directly transfer the premix after mixing and grinding into an oven for drying treatment, transfer it into a crucible after drying and put it into a muffle furnace, and perform high-temperature calcination at 900 °C for 24 h, and then cool it to room temperature in the furnace to obtain the NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 cathode material.

[0059] Perform a scanning electron microscope test on the sample obtained in this comparative example, and the results are shown in the appendix Figure 4 . As can be seen from the figure, the sample prepared by this method does not have a spherical morphology, does not have a hollow structure, and has a relatively large particle size.

[0060] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0061] 1. The method for preparing the cathode material with a hollow sphere structure can be further extended to prepare the cathode material with a multi-layer shell structure. By adding the clinker (unsintered) with a hollow sphere structure prepared once back to the slurry before the spray treatment and performing secondary spray treatment, a material with a double-layer shell structure can be obtained;

[0062] 2. The key steps of this method are sanding treatment and spraying treatment. The present invention provides a method for controllably preparing a hollow sphere structure material. Such a hollow sphere structure can be used to load other materials such as catalysts, additives, high-capacity cathode materials, etc., or materials with large volume changes can be embedded in the material of this structure, etc.

[0063] The prepared cathode material, conductive agent and binder are stirred and mixed according to a mass ratio of 7:2:1, NMP is added for pulping, the material is evenly coated on the aluminum foil using a coater, dried in a vacuum oven, rolled by a rolling machine, and then cut into a cathode electrode sheet with a diameter of about 12 mm. The cathode electrode sheet is made into a button cell with a sodium metal sheet as the anode in a glove box filled with argon. After aging for 12 h, electrochemical performance tests are carried out, and the relevant test data are shown in Table 1;

[0064] Table 1 Electrochemical performance test data

[0065]

[0066] As mentioned above, the above are only the more preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for preparing a positive electrode material for a sodium ion battery with a micron hollow sphere structure, characterized in that: The method includes: S1, fully grinding and mixing the manganese, iron, nickel compound or salt and the sodium source according to the stoichiometric ratio to obtain a premix with uniform composition and uniform particle size distribution; S2, mixing the obtained premix with a dispersant to obtain a premix slurry; S3, spray drying the obtained premix slurry to obtain a raw material with a micron-sized spherical structure; S4, the obtained raw material is put into a sagger and calcined at high temperature to obtain a positive electrode material Na with a hollow spherical morphology. X Ni a Fe b Mn 1-a-b O2, where 0<X≤1.1, 0<a≤1, 0<b≤1.

2. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S1, the grinding and mixing method is sand milling or planetary ball milling, wherein the ball-to-material ratio is 1:1-10, the solid-liquid ratio is 1:0.8-2, and the mixing time is 0.5-8 hours.

3. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S1, the particle size of the premix obtained by grinding and mixing is 0.1 to 10 microns.

4. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S2, the dispersant used is water or ethanol, the mass ratio of the premix to the dispersant is 1:1-2, and the mixture is mixed evenly by stirring for more than 30 minutes.

5. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S3, the raw material obtained by spray drying has a particle size of 0.1 to 50 microns.

6. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S3, the obtained raw material has a spherical morphology and a hollow structure, a rough surface, and no impurities.

7. The method for preparing the positive electrode material of sodium ion battery with micron hollow sphere structure according to claim 1, characterized in that: In step S4, the calcination atmosphere is air or oxygen atmosphere, the calcination temperature is 700-1000° C., and the calcination time is 10-28 hours. The obtained positive electrode material has a hollow sphere structure, and the shell layer is composed of granular single crystals.

8. A sodium ion battery positive electrode material with a micron hollow sphere structure, characterized in that: The material is prepared by the method for preparing a sodium ion battery positive electrode material with a micron hollow sphere structure as described in any one of claims 1 to 7. The material has a spherical morphology and a micron-level hollow structure, and the shell layer is self-assembled by granular single crystals.

9. The micron hollow sphere structure sodium ion battery positive electrode material according to claim 8, characterized in that: The battery prepared with the sodium ion battery positive electrode material with micron hollow sphere structure is used in motor vehicles.

10. The sodium ion battery positive electrode material with micron hollow sphere structure according to claim 8, characterized in that: The battery prepared from the sodium ion battery positive electrode material with micron hollow sphere structure is used in engineering production robots.

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