Coating method of lithium nickel manganese oxide positive electrode material

Abstract

The invention discloses a coating method of a lithium nickel manganese oxide positive electrode material, relates to the technical field of lithium ion batteries, and aims to solve the problem that the process of firstly preparing lithium nickel manganese oxide and then coating is relatively complex. The preparation method comprises the following steps: weighing a nickel source, a manganese source and a lithium source according to process requirements, putting the nickel source, the manganese source and the lithium source into a ball-milling tank, adding deionized water and zirconium oxide beads, and carrying out ball-milling mixing to prepare precursor slurry; removing the zirconium oxide beads by using a screen, adding a silicon-based and / or calcium-based thickening agent, stirring to be viscous, drying, and grinding to obtain precursor powder; the precursor powder is subjected to heat treatment in the air or oxygen atmosphere, an oxide-coated lithium nickel manganese oxide positive electrode material is obtained, and a coating layer comprises silicon oxide and / or calcium oxide; the method is simple in step and easy to operate, continuous tedious process steps of mixing, reaction, heat treatment and the like after the positive electrode material is prepared are not needed, the production cost and difficulty are reduced, the product performance is excellent, and large-scale production and application are facilitated.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for coating lithium nickel manganese oxide cathode material. Background Technology

[0002] With the rapid development of emerging industries such as electric vehicles, lithium-ion battery research and development is focusing on three core objectives: low cost, high energy density, and long cycle life, continuously breaking through performance bottlenecks to meet market upgrade demands. However, existing mainstream cathode materials all have significant shortcomings: layered ternary materials are constrained by the high cost and limited resource reserves of cobalt, hindering their large-scale cost reduction; spinel lithium manganese oxide, while cost-controllable, suffers from low energy density and poor cycle stability, making it difficult to meet the needs of long-life applications; lithium iron phosphate boasts outstanding safety, but its energy density is limited by its structure, making it difficult to meet the demands of high-performance batteries. Against this backdrop, developing cathode materials that combine low cost, high energy density, and excellent cycle performance has become key to solving industry pain points. Spinel lithium nickel manganese oxide, as a modified product of lithium manganese oxide, shows a significant improvement in energy density and cycle life, and has become one of the key research directions in the field of cathode materials. However, during long-term charge-discharge cycles, its surface is prone to side reactions with the electrolyte, leading to increased interfacial impedance, and there is still a small amount of Mn element dissolution problem, affecting the long-term stability of the battery. By constructing a uniform coating layer on the surface of lithium nickel manganese oxide particles, direct contact between the material and the electrolyte can be effectively isolated, and side reactions can be suppressed to improve its stability.

[0003] Lithium nickel manganese oxide coating is mainly a post-coating process, meaning that lithium nickel manganese oxide is prepared first and then coated. For example, in the invention patent application with publication number CN116845197A entitled "A Cathode Material and Its Preparation Method and Lithium-ion Battery", a thickener solution is first prepared, and the core of the cathode material is dispersed in the thickener solution to obtain a precursor solution; a nickel-zirconium mixed solution is added dropwise to the precursor solution, and a hydrolysis reaction is carried out to obtain the cathode material precursor; calcination is then performed to obtain the cathode material. Another example is the invention patent with publication number CN116404168B entitled "Doped and Coated Composite Modified Lithium Nickel Manganese Oxide Cathode Material and Its Preparation Method", which discloses that the prepared lithium nickel manganese oxide cathode material is reacted with multi-metal grafted modified carbon nanotubes under certain conditions to obtain a doped and coated composite modified lithium nickel manganese oxide cathode material. Although this post-coating method avoids the influence of the coating agent on the preparation of the cathode material, it generally requires additional process steps such as mixing, reaction, and heat treatment after the cathode material is prepared, which increases the production cost and difficulty. Summary of the Invention

[0004] The purpose of this invention is to provide a coating method for lithium nickel manganese oxide cathode materials, so as to solve the problem that the coating process is relatively complicated after preparing lithium nickel manganese oxide.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for coating lithium nickel manganese oxide cathode material, comprising:

[0006] Ball milling and mixing: Weigh out the nickel source, manganese source and lithium source according to the process requirements and place them in the ball milling jar. Add deionized water and zirconium oxide beads and then ball mill and mix to obtain the precursor slurry.

[0007] Thickening and drying: After removing the zirconium oxide beads with a sieve, add a silicon-based and / or calcium-based thickener, stir until viscous, dry and grind to obtain the precursor powder;

[0008] Heat treatment: The precursor powder is heat-treated in an air or oxygen atmosphere to obtain an oxide-coated lithium nickel manganese oxide cathode material, the coating layer including silicon oxide and / or calcium oxide.

[0009] Preferably, the thickener is one or more of aluminum silicate, magnesium aluminum silicate, lanthanum silicate, silicon dioxide, and calcium-based bentonite, and the amount of thickener added is 0.1 to 2% of the total mass of nickel source, manganese source, lithium source, and water.

[0010] Preferably, the manganese source is one or more of manganese tetroxide, manganese dioxide, manganese carbonate, manganese oxalate, and manganese acetate; the nickel source is one or more of nickel hydroxide, nickel oxide, nickel carbonate, and basic nickel carbonate; and the lithium source is one or more of lithium carbonate and lithium hydroxide. The molar ratio of nickel, manganese, and lithium in the nickel, manganese, and lithium sources is 1:3:2.1.

[0011] Preferably, in the ball milling mixing step, the mass ratio of water to solids in the slurry is (1.1-1.5):1, the mass ratio of the added zirconia beads to the solids in the slurry is (3-5):1, the ball milling time is 1-4 hours, and the ball milling speed is 300-500 rpm.

[0012] Preferably, the heat treatment involves pretreatment at 500–600℃ for 4–8 hours, followed by heat treatment at 800–900℃ for 10–16 hours.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] 1. The coating method for the lithium nickel manganese oxide cathode material is simple and easy to operate. It eliminates the need for cumbersome mixing, reaction, and heat treatment processes after the cathode material is prepared, thus reducing production costs and difficulties. In addition, the product has excellent performance and is conducive to large-scale production and application.

[0015] 2. The coating method of this lithium nickel manganese oxide cathode material involves adding silicon-based and calcium-based thickeners to the slurry obtained after ball milling and separating the balls. The cross-linking network structure formed by the thickeners can "lock" in the solid particles in the slurry, preventing irregular agglomeration during drying and affecting the physical properties of the cathode material.

[0016] 3. The coating method of this lithium nickel manganese oxide cathode material, the addition of thickener increases the viscosity of the slurry after ball milling, avoids the stratification problem caused by the density difference of different raw materials during the drying process, and improves the uniform dispersion of lithium nickel manganese oxide elements.

[0017] 4. The coating method of the lithium nickel manganese oxide cathode material: after heat treatment of silicon-based and calcium-based thickeners, silicon oxide and calcium oxide coating layers can be formed, which improves the stability of the cathode material during cycling. Attached Figure Description

[0018] Figure 1 This is an XRD image of the sample prepared in Example 1 of this invention.

[0019] Figure 2 These are scanning electron microscope (SEM) images of the samples prepared in Example 1 of this invention.

[0020] Figure 3 This is a scanning electron microscope (SEM) image of the sample prepared in Comparative Example 1 of this invention.

[0021] Figure 4 These are the capacity test curves of the samples in Example 1 and Comparative Example 1 of this invention under a charge-discharge current of 0.1C.

[0022] Figure 5 These are the capacity retention rate cycling curves of the samples in Example 1 and Comparative Example 1 of this invention under 1C conditions. Detailed Implementation

[0023] To address the problems mentioned in the background section, this invention, after extensive theoretical conceptualization and experimental testing, ultimately yielded the following solution: a method for coating lithium nickel manganese oxide cathode material, specifically comprising the following steps:

[0024] 1) Weigh the raw materials nickel source, manganese source and lithium source according to the process requirements and place them in a ball mill jar. Add deionized water and zirconium oxide beads and then ball mill and mix to obtain the precursor slurry.

[0025] Generally, the manganese source can be one or more of manganese tetroxide, manganese dioxide, manganese carbonate, manganese oxalate, and manganese acetate; the nickel source can be one or more of nickel hydroxide, nickel oxide, nickel carbonate, and basic nickel carbonate; and the lithium source can be one or more of lithium carbonate and lithium hydroxide. Typically, the molar ratio of nickel, manganese, and lithium in the nickel, manganese, and lithium sources is 1:3:2.1.

[0026] For reference, the mass ratio of water to raw materials (nickel source, manganese source, lithium source) should be (1.1~1.5):1, the mass ratio of the added zirconia beads to the solid raw materials in the slurry should be (3~5):1, the ball milling time can be controlled at 1~4h, and the ball milling speed can be controlled at 300~500rpm.

[0027] 2) After removing the zirconium oxide beads with a sieve, add a silicon-based and / or calcium-based thickener, stir until viscous, dry and grind to obtain the precursor powder;

[0028] In a preferred embodiment, the thickener is preferably one or more of aluminum silicate, magnesium aluminum silicate, lanthanum silicate, silicon dioxide, and calcium-based bentonite. Furthermore, the amount of thickener added can be further controlled at 0.1 to 2% of the total mass of the nickel source, manganese source, lithium source, and water.

[0029] 3) The precursor powder is heat-treated in an air or oxygen atmosphere to obtain an oxide-coated lithium nickel manganese oxide cathode material, the coating layer including silicon oxide and / or calcium oxide;

[0030] For reference, the heat treatment is to first pretreat at 500-600℃ for 4-8 hours, and then heat-treat at 800-900℃ for 10-16 hours.

[0031] The present invention will be further illustrated below through several embodiments and comparative examples. The embodiments below are not all examples of the present invention, and therefore should not be regarded as an absolute limitation of the present invention. They are just a few groups randomly selected within the scope of the above-mentioned invention. Therefore, the scope of the present invention should be based on the description of the above-mentioned invention.

[0032] In the following embodiments and comparative examples, the performance of the cathode material was tested using conventional button cell technology. The battery assembly and performance testing mainly included the following steps:

[0033] ① Positive electrode preparation: The prepared lithium nickel manganese oxide material, conductive agent Super P, and binder PVDF are mixed in a weight ratio of 8:1:1 to form a positive electrode slurry, which is coated on one side of the aluminum foil surface and dried to obtain a positive electrode sheet.

[0034] ② Button battery assembly: The button battery is assembled in the following order: negative electrode shell, lithium sheet, separator, electrolyte, positive electrode sheet, gasket, spring sheet and positive electrode shell. The electrolyte solute is 1M LiPF6, the solvent volume ratio is EC:DMC:DEC=1:1:1, and the separator is a polyethylene porous membrane.

[0035] ③ Battery capacity test: The test voltage is 3.5~4.95 V. The constant current step is used for charging and then for discharging. The charge and discharge current for capacity test is 0.1C, and the charge and discharge current for cycle test is 1C.

[0036] Example 1

[0037] Weigh 94.5g of manganese tetroxide, 37.1g of nickel hydroxide, and 35.5g of lithium carbonate. Add 180.5ml of deionized water to a zirconia ball mill jar, then add 492.2g of zirconia balls. Set the milling speed to 400rpm and the milling time to 3h. Add 3.47g of aluminum silicate to the slurry obtained after milling, stir evenly, and then dry in a forced-air drying oven. Grind the dried slurry to obtain the precursor powder. After grinding, heat-treat the precursor powder at 550℃ in air for 6h, then heat-treat at 850℃ for 12h to obtain the desired lithium nickel manganese oxide cathode.

[0038] The XRD pattern of the lithium nickel manganese oxide cathode material prepared by the above method is shown in the patent appendix. Figure 1 LiNi is a spinel phase. 0.5 Mn 1.5 O4, the sample phase has high purity and good crystallinity. The SEM image of the sample obtained in Example 1 is attached. Figure 2 Comparative Example 1 (with appendix) Figure 3 Its crystal structure is complete, its particle size distribution is more uniform, and its tap density is 2.3 g / cm³. 3 Theoretically, it has a higher volumetric energy density. The 0.1C charge-discharge curves of the coin cell prepared in Example 1 are shown in the appendix. Figure 4 The 0.1C discharge specific capacity is 139.7 mAh / g, and the capacity retention rate after 1000 cycles at 1C is 92.7%, which is significantly better than the 83.3% of the comparative example. The good capacity and cycle stability are due to the addition of thickener, which makes the element distribution in the cathode material more uniform. At the same time, the oxide coating formed by coating can effectively prevent the corrosion of the cathode material and improve stability.

[0039] Comparative Example 1

[0040] This embodiment is based on Example 1, except that no thickener was added, and the ball-milled slurry was directly dried, ground, and then heat-treated. The SEM image of the sample obtained in this comparative example is attached. Figure 3 The sample particles were unevenly distributed and severely agglomerated, with a tap density of 1.8 g / cm³. 3 The 0.1C discharge specific capacity of the installed coin cell is 137.2 mAh / g, and the capacity retention rate is 83.3% after 1000 cycles at 1C.

[0041] Example 2

[0042] This embodiment is based on Embodiment 1, except that the thickener is replaced with calcium-based bentonite.

[0043] Example 3

[0044] This embodiment is based on Example 1, except that the amount of thickener added is changed to 0.35g.

[0045] Example 4

[0046] This embodiment is based on Example 1, except that the manganese source is changed to manganese dioxide, and the mass added is 52.1g.

[0047] Example 5

[0048] This embodiment is based on Example 1, except that the mass of water added during ball milling is 278.9 g, and the amount of zirconia beads added is 820.3 g, that is, the liquid-solid ratio of the ball milling step is 1.7, and the ball-to-material ratio is 5:1.

[0049] Example 6

[0050] This embodiment is based on Embodiment 1, except that the ball milling speed is 300 rpm and the ball milling time is 4 hours.

[0051] Example 7

[0052] This embodiment is based on Embodiment 1, except that the ball milling speed is 500 rpm and the ball milling time is 1 hour.

[0053] Example 8

[0054] This embodiment is based on Embodiment 1, except that the heat pretreatment procedure is changed to 500℃ for 8 hours.

[0055] Example 9

[0056] This embodiment is based on Embodiment 1, except that the second heat treatment temperature is changed to 900℃ and the heat treatment time is changed to 10h.

[0057] The results of tap density, battery capacity test, and cycle stability test of the cathode materials obtained from the examples and comparative examples are compared in Table 1 below:

[0058] Table 1: Performance Comparison of Examples and Comparative Samples

[0059]

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0061] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for coating lithium nickel manganese oxide cathode material, characterized in that, include: Ball milling and mixing: Weigh out the nickel source, manganese source and lithium source according to the process requirements and place them in the ball milling jar. Add deionized water and zirconium oxide beads and then ball mill and mix to obtain the precursor slurry. Thickening and drying: After removing the zirconium oxide beads with a sieve, add a silicon-based and / or calcium-based thickener, stir until viscous, dry and grind to obtain the precursor powder; Heat treatment: The precursor powder is heat-treated in an air or oxygen atmosphere to obtain an oxide-coated lithium nickel manganese oxide cathode material, the coating layer including silicon oxide and / or calcium oxide.

2. The coating method for lithium nickel manganese oxide cathode material according to claim 1, characterized in that: The thickener is one or more of aluminum silicate, magnesium aluminum silicate, lanthanum silicate, silicon dioxide, and calcium-based bentonite, and the amount of thickener added is 0.1 to 2% of the total mass of nickel source, manganese source, lithium source, and water.

3. The coating method for lithium nickel manganese oxide cathode material according to claim 1, characterized in that: The manganese source is one or more of manganese tetroxide, manganese dioxide, manganese carbonate, manganese oxalate, and manganese acetate; the nickel source is one or more of nickel hydroxide, nickel oxide, nickel carbonate, and basic nickel carbonate; and the lithium source is one or more of lithium carbonate and lithium hydroxide. The molar ratio of nickel, manganese, and lithium in the nickel, manganese, and lithium sources is 1:3:2.

1.

4. The coating method for lithium nickel manganese oxide cathode material according to claim 1, characterized in that: In the ball milling mixing step, the mass ratio of water to solids in the slurry is (1.1-1.5):1, the mass ratio of added zirconia beads to solids in the slurry is (3-5):1, the ball milling time is 1-4 hours, and the ball milling speed is 300-500 rpm.

5. The coating method for lithium nickel manganese oxide cathode material according to claim 1, characterized in that: The heat treatment involves first pre-treating at 500–600℃ for 4–8 hours, and then heating to 800–900℃ for 10–16 hours.

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