Positive electrode material and preparation method thereof, positive plate, battery and power utilization device

Abstract

The invention discloses a positive electrode material and a preparation method thereof, a positive plate, a battery and an electric device, a ternary NCM material reacts with a cobalt-containing material and a fluorine-containing material, so that cobalt ions and fluorine ions are attached to the surface of the ternary NCM material, and a modified ternary NCM material is formed. The introduction of cobalt ions can improve the rate capability of the battery; the fluorine ions are modified on the surface of the ternary NCM material, so that a decomposition product of lithium salt in an electrolyte can form a stable deposition layer, and the cycling stability of the ternary NCM material is improved; strong acid radical ions are formed on the surface of the ternary NCM material in a strong acid reaction environment, so that generation of excessive alkaline substances in the battery is inhibited; and through the synergistic effect of cobalt ions, fluorine ions and strong acid conditions, the rate capability and the cycle performance of the battery are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to positive electrode materials and preparation methods thereof, positive electrode sheets, batteries and electrical devices. Background Art

[0002] In today's society, people's living standards are getting higher and higher, and high-quality development is becoming more and more important. New energy power tools have the characteristics of low pollution and high energy density, and are favored by more consumers. The application range of electrochemical devices such as lithium-ion batteries and sodium-ion batteries is becoming more and more extensive, and people have higher and higher requirements for their performance, especially the safety, stability, capacity, etc. of batteries, and expect batteries to have good comprehensive performance in all aspects.

[0003] One of the key factors affecting the electrical performance of batteries is the stability of the positive electrode material, which restricts the overall performance of the battery. Therefore, how to improve the rate performance and cycle performance of the positive electrode material has become the top priority of research in this field. Summary of the invention

[0004] Based on the above problems, the present invention provides a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device to improve the rate performance and cycle performance of the battery.

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] The first aspect of the present application provides a method for preparing a positive electrode material, wherein a ternary NCM material is reacted with a cobalt-containing material and a fluorine-containing material so that cobalt ions and fluorine ions adhere to the surface of the ternary NCM material to form a modified ternary NCM material.

[0007] In order to optimize the above technical solutions, the specific limitations adopted also include:

[0008] The cobalt-containing material is at least one of cobalt fluoride, cobalt sulfate, cobalt chloride, cobalt hydroxide and cobalt carbonate.

[0009] The fluorine-containing material is at least one of cobalt fluoride, calcium fluoride, magnesium fluoride and aluminum fluoride.

[0010] Preferably, the cobalt-containing material and the fluorine-containing material are directly cobalt fluoride; and the reaction mass ratio of the ternary NCM material to cobalt fluoride is in the range of 7 to 11:1.

[0011] The reaction is carried out in a strong acid solution, and the initial pH value of the reaction solution is in the range of 3.0 to 4.5.

[0012] Furthermore, the reaction temperature is 140°C to 200°C, and the reaction time is 12 to 24 hours.

[0013] A second aspect of the present application provides a positive electrode material, comprising a ternary NCM material with cobalt ions and fluoride ions attached to the surface.

[0014] The third aspect of the present application provides a positive electrode sheet having a positive electrode active material thereon, wherein the positive electrode active material includes the positive electrode material prepared by the method described in the first aspect of the present application or the positive electrode material described in the second aspect of the present application.

[0015] The fourth aspect of the present application provides a battery, which includes the positive electrode sheet provided in the third aspect of the present application.

[0016] The fifth aspect of the present application provides an electrical device, which uses the battery provided by the fourth aspect of the present application.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery and an electric device, wherein a ternary NCM material is reacted with a cobalt-containing material and a fluorine-containing material so that cobalt ions and fluorine ions are attached to the surface of the ternary NCM material to form a modified ternary NCM material; Co 2+ The introduction of F can further improve the rate performance of the battery; - The surface modification of the ternary NCM material enables the decomposition products of the lithium salt in the electrolyte to form a stable deposition layer, thereby improving the cycle stability of the ternary NCM material.

[0019] It is preferred that the reaction be carried out in an acid solution, and the acidic reaction environment allows strong acid radical ions to form on the surface of the ternary NCM material, thereby inhibiting the production of excessive alkaline substances such as Li2CO3 inside the battery. Experimental verification has found that the acidic reaction conditions and the modification of the ternary NCM material by cobalt ions and fluoride ions result in a technical effect of synergistically enhancing the battery's cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : SEM image (10.0 μm) of the modified NCM811 prepared in Example 1 of the present invention.

[0021] Figure 2 : SEM image (50.0 μm) of the modified NCM811 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0023] The experimental methods used in the following examples are all conventional methods unless otherwise specified, and the reagents, methods and equipment used are all conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0024] For the sake of simplicity, this document only specifically discloses some numerical values ​​and optional ranges. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range; the optional items in the optional range can also be combined arbitrarily.

[0025] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0026] The present application provides a method for preparing a positive electrode material, wherein a ternary NCM material is reacted with a cobalt-containing material and a fluorine-containing material so that cobalt ions and fluorine ions adhere to the surface of the ternary NCM material to form a modified ternary NCM material.

[0027] The cobalt-containing material is at least one of cobalt fluoride, cobalt sulfate, cobalt chloride, cobalt hydroxide and cobalt carbonate.

[0028] The fluorine-containing material is at least one of cobalt fluoride, calcium fluoride, magnesium fluoride and aluminum fluoride.

[0029] In a preferred embodiment, the cobalt-containing material and the fluorine-containing material directly use cobalt fluoride; the reaction mass ratio of the ternary NCM material to cobalt fluoride is in the range of 7 to 11:1.

[0030] The reaction is carried out in a strong acid solution, and the initial pH value of the reaction solution ranges from 3.0 to 4.5.

[0031] The reaction temperature is 140°C to 200°C, and the reaction time is 12 to 24 hours.

[0032] In some embodiments, the reaction product is washed and dried.

[0033] The present application also provides a positive electrode material, including a ternary NCM material with cobalt ions and fluoride ions attached to the surface.

[0034] The present invention also provides a positive electrode sheet, which contains the positive electrode active material.

[0035] In some embodiments, the positive electrode sheet also contains a conductive agent and a binder. The selection of the mixing ratio of the positive electrode active material to the conductive agent and the binder can be reasonably determined by those skilled in the art through experiments and experience.

[0036] In some embodiments, the positive electrode sheet can be prepared by:

[0037] The positive electrode active material is mixed with a binder and a conductive agent, coated on a foil, and dried.

[0038] In some embodiments, the positive electrode current collector may be a metal foil, a composite current collector or other types of current collectors. For example, as a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0039] The acidic conditions in the following embodiments are formed by concentrated nitric acid, but the acidic conditions of the present invention are not limited to the use of concentrated nitric acid, and strong acids such as concentrated hydrochloric acid and concentrated sulfuric acid can also be used.

[0040] The battery containing the positive electrode material of the present application may be a lithium ion battery, a sodium ion battery, etc. In general, the battery of the present application may include a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, the active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The present application has no special restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which mainly prevents the positive and negative electrodes from short-circuiting, and allows ions to pass through. The present application has no special restrictions on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0041] In some embodiments, the batteries of the present application may be assembled into a battery module. The number of batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0042] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0043] In an electrical device containing the battery of the present application, the battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto; as an electrical device, the battery can be selected according to its usage requirements.

[0044] The present invention is further described in detail below in conjunction with specific embodiments:

[0045] Embodiment 1:

[0046] 1. Preparation of modified NCM811

[0047] Dissolve NCM811 and CoF2 in concentrated nitric acid, stir evenly, transfer them to a reactor, and bake at a temperature of 160°C-180°C for 16-20 hours; obtain modified NCM811 after centrifugal washing and vacuum drying at 60°C for 20-24 hours; wherein, the concentration of concentrated nitric acid is 8 mol / L, the mass ratio of NCM811 to CoF2 is in the range of 9:1, the mass ratio of NCM811 to concentrated nitric acid is in the range of 1:28, and the initial pH value of the reaction solution is 3.5-4.0.

[0048] 2. Preparation of positive electrode slurry:

[0049] The positive electrode active material is the modified NCM811 product obtained in step 1, the binder is PVDF (Kureha, KF1100), and the conductive agent is Super P (Swiss Termeco); the mixture is stirred and mixed in a ratio of active material: binder: conductive agent = 95.2:2.0:3.0, and after mixing evenly, it is coated on a 14um aluminum foil and dried in a vacuum drying oven at 120°C for 12h.

[0050] 3. Assembly of button batteries:

[0051] The button battery shell uses the CR2430 model, the diaphragm uses a 20um diaphragm, and the electrode uses a positive electrode with a uniform coating. In a glove box filled with argon, the button battery is assembled in the following order: battery shell - placing the positive electrode - dripping the electrolyte - placing the diaphragm - dripping the electrolyte - placing the lithium sheet - placing the gasket spring - battery shell.

[0052] 4. Rate performance test:

[0053] A button battery charge and discharge tester (Wuhan Blue Electric, CT2001A) was used to perform charge and discharge tests on the button batteries at 0.1C, 0.2C, 0.5C, and 1C, with a voltage range of 3.0-4.5V. The test results are shown in Table 1.

[0054] 5. Cycle performance test:

[0055] The button battery was charged and discharged for 50 cycles at 0.2C using a button battery charge and discharge tester (Wuhan Blue Electric, CT2001A). The voltage range was 3.0-4.5V. The test results are shown in Table 1.

[0056] Embodiment 2:

[0057] It is basically the same as Example 1, except that the mass ratio of NCM811 to CoF2 is 7:1.

[0058] Embodiment 3:

[0059] It is basically the same as Example 1, except that the mass ratio of NCM811 to CoF2 is 8:1.

[0060] Embodiment 4:

[0061] It is basically the same as Example 1, except that the mass ratio of NCM811 to CoF2 is 10:1.

[0062] Embodiment 5:

[0063] It is basically the same as Example 1, except that the mass ratio of NCM811 to CoF2 is 11:1.

[0064] Embodiment 6:

[0065] The method is basically the same as Example 1, except that the mass ratio of NCM811 to concentrated nitric acid is 1:20, and the initial pH value of the reaction solution is 4.5-5.0.

[0066] Embodiment 7:

[0067] The method is basically the same as Example 1, except that the mass ratio of NCM811 to concentrated nitric acid is 1:24, and the initial pH value of the reaction solution is 4.0-4.5.

[0068] Embodiment 8:

[0069] The method is basically the same as Example 1, except that the mass ratio of NCM811 to concentrated nitric acid is 1:32, and the initial pH value of the reaction solution is 3.0-3.5.

[0070] Embodiment 9:

[0071] The method is basically the same as Example 1, except that the mass ratio of NCM811 to concentrated nitric acid is 1:36, and the initial pH value of the reaction solution is 2.5-3.0.

[0072] Comparative Example 1:

[0073] It is basically the same as Example 1, except that no CoF2 is introduced in step 1.

[0074] Comparative Example 2:

[0075] The method is substantially the same as Example 1, except that no concentrated nitric acid is introduced in step 1.

[0076] Comparative Example 3:

[0077] The method is basically the same as Example 1, except that concentrated nitric acid and CoF2 are not introduced in step 1.

[0078] Table 1 Test evaluation results of various embodiments and comparative examples

[0079] serial number 0.1C Capacity 0.2C Capacity 0.5C Capacity 1C Capacity 50-cycle performance Example 1 232.1mAh / g 218.3mAh / g 200.1mAh / g 179.4mAh / g 91.8％ Example 2 224.1mAh / g 210.2mAh / g 188.2mAh / g 164.3mAh / g 90.1％ Example 3 225.4mAh / g 211.6mAh / g 189.1mAh / g 164.9mAh / g 90.8％ Example 4 225.3mAh / g 211.3mAh / g 188.9mAh / g 165.4mAh / g 90.9％ Example 5 225.0mAh / g 210.9mAh / g 186.5mAh / g 164.8mAh / g 90.6％ Example 6 221.4mAh / g 209.8mAh / g 186.9mAh / g 164.9mAh / g 89.8％ Example 7 222.2mAh / g 209.9mAh / g 187.5mAh / g 165.3mAh / g 90.5％ Example 8 221.9mAh / g 210.4mAh / g 187.8mAh / g 165.1mAh / g 90.7％ Example 9 220.9mAh / g 208.3mAh / g 186.4mAh / g 163.6mAh / g 89.5％ Comparative Example 1 218.3mAh / g 204.3mAh / g 180.0mAh / g 158.4mAh / g 88.1％ Comparative Example 2 219.3mAh / g 203.8mAh / g 180.1mAh / g 157.9mAh / g 87.9％ Comparative Example 3 211.6mAh / g 201.2mAh / g 178.9mAh / g 153.4mAh / g 87.2％

[0080] Test evaluation results:

[0081] By comparing the embodiment with comparative examples 1 and 3, it can be seen that the modified NCM811 material is used as the positive electrode material, and the rate performance and cycle stability of the positive electrode material can be improved by introducing cobalt ions and fluorine ions;

[0082] By comparing the embodiment with comparative example 2, it can be seen that the strong acid reaction environment can form acid radical ions NO3 on the surface of NCM811. - , inhibit the production of excessive alkaline substances such as Li2CO3 inside the battery and improve the cycle stability of the battery.

[0083] By comparing Examples 1-9, it can be seen that the reaction mass ratio and acidic conditions have a significant impact on product performance. Selecting a suitable NCM811, CoF2 reaction mass ratio and acidic environmental conditions can obtain a better product.

[0084] It has been verified through experiments that acidic reaction conditions have an important influence on the effect of the scheme of the present application: the acidic reaction conditions and the modification of the ternary NCM material by cobalt ions and fluoride ions have achieved a technical effect of synergistically enhancing the cycle performance of the battery, which is better than the scheme of only reacting with cobalt-containing materials and fluorine-containing materials, and the effect is better when the initial pH value of the reaction solution is 3.0-4.5, and the effect is best when the initial pH value of the reaction solution is 3.5-4.0.

[0085] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that: The ternary NCM material is reacted with a cobalt-containing material and a fluorine-containing material, so that cobalt ions and fluorine ions are attached to the surface of the ternary NCM material to form a modified ternary NCM material.

2. The method for preparing the positive electrode material according to claim 1, characterized in that: The cobalt-containing material is at least one of cobalt fluoride, cobalt sulfate, cobalt chloride, cobalt hydroxide and cobalt carbonate.

3. The method for preparing the positive electrode material according to claim 1, characterized in that: The fluorine-containing material is at least one of cobalt fluoride, calcium fluoride, magnesium fluoride and aluminum fluoride.

4. The method for preparing the positive electrode material according to claim 1, characterized in that: The cobalt-containing material and the fluorine-containing material directly use cobalt fluoride; the reaction mass ratio of the ternary NCM material to cobalt fluoride is in the range of 7 to 11:

1.

5. The method for preparing the positive electrode material according to claim 1, characterized in that: The reaction is carried out in a strong acid solution, and the initial pH value of the reaction solution is in the range of 3.0 to 4.

5.

6. The method for preparing the positive electrode material according to claim 1, characterized in that: The reaction temperature is 140° C. to 200° C., and the reaction time is 12 to 24 hours.

7. A positive electrode material, characterized in that: It includes a ternary NCM material with cobalt ions and fluorine ions attached to the surface.

8. A positive electrode sheet, characterized in that: The positive electrode sheet has a positive electrode active material, and the positive electrode active material includes the positive electrode material prepared by the method according to any one of claims 1 to 6 or the positive electrode material according to claim 7.

9. A battery, characterized in that: The battery comprises the positive electrode sheet according to claim 8.

10. An electrical device, characterized in that: The electrical device uses the battery according to claim 9.

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