Method for preparing high-performance lithium manganate positive electrode material based on regulation and control of high-oxygen atmosphere

Abstract

The invention discloses a method for preparing a high-performance lithium manganate positive electrode material based on high-oxygen atmosphere regulation and control, and belongs to the technical field of lithium ion battery positive electrode materials. The preparation method comprises the following steps: S1, uniformly mixing a lithium source, a manganese source and an optional additive in a high-speed mixer according to a ratio to obtain precursor powder; s2, putting the obtained precursor powder into a crucible, putting the crucible into a controllable atmosphere muffle furnace, and carrying out high-temperature sintering in an oxidizing atmosphere to obtain a sintered product; and S3, coarsely crushing the obtained sintered product by a jaw crusher, preliminarily grading by a screen, finely crushing by a jet mill, and further screening the crushed material by a screen to prepare the high-performance lithium manganate positive electrode material. The lithium manganate positive electrode material prepared through high-oxygen atmosphere regulation and control can effectively inhibit dissolution of manganese ions, so that the structural stability and the rate capability of the material are improved, and the cycle life of the material is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery positive electrode materials, and specifically relates to a method for preparing high-performance lithium manganate positive electrode materials under the control of a high-oxygen atmosphere. Background Art

[0002] Amidst the growing global demand for clean energy, lithium-ion batteries, with their high energy density, long cycle life, and lack of memory effect, have become core energy storage devices in fields such as electric vehicles and energy storage systems. As a key component of lithium-ion batteries, the performance of cathode materials directly impacts the overall performance of the battery. Lithium manganese oxide (LiMn2O4) is considered one of the most promising cathode materials for lithium-ion batteries due to its significant advantages, including low cost, high safety, and environmental friendliness.

[0003] However, lithium manganese oxide faces many challenges in practical application, among which short cycle life and significant capacity decay are particularly prominent, severely limiting its large-scale commercial application. In-depth research has shown that manganese dissolution and structural distortion caused by the Jahn-Teller effect are the main causes of these problems. During the charge and discharge process, manganese ions in the spinel LiMn2O4 lattice dissolve into the electrolyte, destroying the structural integrity of the electrode material and causing a rapid decrease in capacity. At the same time, lattice distortion caused by the Jahn-Teller effect further deteriorates the structural stability of the material and exacerbates capacity decay.

[0004] To improve the performance of lithium manganese oxide, researchers have conducted extensive research, currently primarily modifying it through methods such as doping and coating. For example, other metal ions are introduced into the lithium manganese oxide lattice to stabilize the crystal structure; or coating is performed on the material surface to isolate the electrolyte from the electrode material and inhibit manganese dissolution. However, these existing technologies still have significant drawbacks. For example, the doping process may alter the electronic structure of the material, leading to complex synthesis processes; and coating techniques face challenges such as high costs and limited effectiveness, making it difficult to achieve the desired performance improvement.

[0005] Therefore, developing a simple, efficient, low-cost method that can significantly improve the cycle stability and rate performance of lithium manganese oxide is of great significance to promoting the widespread application of lithium manganese oxide in the field of lithium-ion batteries. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing high-performance lithium manganate positive electrode materials under high oxygen atmosphere control. The present invention effectively promotes the Mn 3+ Xiang Mn 4+The oxidation conversion reduces oxygen vacancy defects, stabilizes the spinel structure, and solves the current problems of lithium manganese oxide positive electrode materials such as poor cycle performance under high rate conditions, insufficient crystal structure stability, and easy dissolution of manganese elements.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a high-performance lithium manganate positive electrode material under high oxygen atmosphere control, comprising the following steps:

[0009] S1. Weigh the lithium source, manganese source and optional additives according to the designed ratio, place the weighed raw materials in a high-speed mixer, and mix them evenly at a speed of 600 to 800 r / min for 1 to 2 hours using a dry mixing method to obtain a precursor powder with uniform composition;

[0010] S2. The precursor powder obtained in step S1 is placed in a crucible, placed in a controlled atmosphere muffle furnace, and sintered at a high temperature under an oxidizing atmosphere to obtain a structurally stable sintered product;

[0011] S3. The sintered product obtained in step S2 is coarsely crushed by a jaw crusher, preliminarily graded through a 100-mesh sieve, and then finely ground using a jet mill to control the particle size D50 of the finished powder to 8 to 12 μm. The ground material is further sieved through a 300-mesh sieve to obtain a high-performance lithium manganese oxide positive electrode material with uniform particle size distribution and high purity.

[0012] Preferably, in step S1, the lithium source is lithium carbonate (Li2CO3), the manganese source is manganese tetraoxide (Mn3O4), and the additives are aluminum oxide (Al2O3), lanthanum oxide (La2O3), and lithium fluoride (LiF).

[0013] Preferably, the molar ratio of Li, Mn, Al, La and F in Li2CO3, Mn3O4, Al2O3, La2O3 and LiF is (1-1.03):(1-2):(0-0.03):(0-0.03):(0-0.01).

[0014] Preferably, in step S2, the volume fraction of oxygen in the muffle furnace is controlled to be 25% to 100% during the high-temperature sintering.

[0015] Preferably, in step S2, the volume fraction of oxygen in the muffle furnace is controlled to be 30% to 60% during the high-temperature sintering.

[0016] Preferably, in step S2, the process of high-temperature sintering in the muffle furnace is: first heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, and finally naturally cooling to room temperature.

[0017] The present invention also discloses a high performance lithium manganate cathode material prepared by the above preparation method, the chemical formula of which is Li a Mn 2-x-y La x Al y O 4-z F z , where 1≤a≤1.03, 0<x≤0.03, 0<y≤0.03, 0<z≤0.01.

[0018] The invention also discloses the application of the high-performance lithium manganate positive electrode material in lithium ion batteries.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the present invention, the entire sintering process is carried out under the protection of a flowing high oxygen concentration atmosphere (oxygen volume fraction of 25% to 100%), and the final sintering temperature is controlled to 720°C, wherein the temperature is kept at 700°C for 6 hours. By introducing a high oxygen concentration atmosphere, the present invention significantly increases the oxygen partial pressure in the furnace, thereby promoting the partial low-valent Mn in the precursor to be quenched. 3+ Oxidized to Mn 4 + The Mn in lithium manganate exists mainly in +3 and +4 valence states. In the ideal stoichiometric ratio, the average valence state of Mn is +3.5, that is, the Mn 3+ and Mn 4+ Composition; When sintered in an oxygen-deficient or air atmosphere, Mn is likely to appear 3+ Too high a content will trigger the Jahn-Teller effect, causing lattice distortion and even local structural collapse or phase transition (such as from cubic phase to tetragonal phase), destroying the stability of the spinel structure. 3+ It can react with HF in the electrolyte to form soluble MnF2, causing capacity decay and reduced cycle life. The introduction of a high-oxygen atmosphere in the present invention helps reduce the number of oxygen vacancies, improve oxygen coordination integrity, and enhance the covalency and bonding strength of the Mn-O bond, thereby improving the thermal stability of the crystal structure. Furthermore, during the 6-hour holding period at 700°C, it facilitates grain growth and grain boundary reconstruction, making the material structure more uniform and dense, further enhancing the stability of the spinel structure.

[0021] At the same time, the test results show that, under the same test conditions, the lithium manganese oxide samples prepared by sintering in a high oxygen atmosphere exhibit significantly improved cycle stability. Specifically: the sample prepared in an atmosphere with an oxygen volume fraction of 30%, after 50 charge and discharge cycles, its capacity retention rate reached 98.6%; the sample prepared in an atmosphere with an oxygen volume fraction of 40%, the capacity retention rate was further improved to 99.19%. The above results are significantly better than the performance of the samples sintered in traditional air (oxygen volume fraction of 21%), which can usually only achieve a capacity retention rate of about 97.8%, and further improvement is more difficult. The present invention successfully increases the capacity retention rate of the material to more than 98% by combining a high oxygen atmosphere of a specific ratio with an optimized preparation process, significantly improving the cycle life and structural stability of the lithium manganese oxide positive electrode material, and providing strong support for its application in high-power lithium-ion batteries.

[0022] In summary, the present invention effectively promotes the Mn 3+ Xiang Mn 4+ The oxidation conversion reduces oxygen vacancy defects, stabilizes the spinel structure, and inhibits the dissolution of manganese ions, significantly improving the structural stability, rate performance and cycle life of lithium manganese oxide positive electrode materials, providing a solid material foundation for its application in the field of high-power lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the lithium manganate positive electrode material prepared in Example 1 of the present invention;

[0024] Figure 2 This is the cycle performance curve of the lithium manganate positive electrode material prepared in Example 1 of the present invention at room temperature;

[0025] Figure 3 This is the cycle performance curve of the lithium manganate positive electrode material prepared in Example 2 of the present invention at room temperature;

[0026] Figure 4 This is the cycle performance curve of the lithium manganate positive electrode material prepared in Comparative Example 1 of the present invention at room temperature. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0030] The present invention provides a method for preparing a high-performance lithium manganate positive electrode material under high oxygen atmosphere control, comprising the following steps:

[0031] S1. According to the molar ratio of Li, Mn, Al, La, F is (1-1.03): (1-2):

[0032] The raw materials lithium carbonate, manganese manganese oxide, aluminum oxide, lanthanum oxide and lithium fluoride are weighed in a designed ratio of (0-0.03): (0-0.03): (0-0.01), the weighed raw materials are placed in a high-speed mixer, and the dry mixing method is used to uniformly mix them at a speed of 600-800 r / min for 1-2 hours to obtain a precursor powder with uniform composition.

[0033] S2. The precursor powder obtained in step S1 is loaded into a crucible, placed in a controlled atmosphere muffle furnace, and sintered at an oxygen volume fraction of 25% to 100% using the following process: heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, performing high-temperature sintering, and finally cooling naturally to obtain a sintered product with a stable structure.

[0034] S3. The sintered product obtained in step S2 was crushed by a jaw crusher, and then preliminarily graded by a 100-mesh sieve. Then, it was finely ground by a jet mill to control the particle size D50 of the finished powder to 8-12 μm. The crushed material was further sieved by a 300-mesh sieve to obtain high-performance Li a Mn 2-x-y La x Al y O 4-z F z Lithium manganese oxide positive electrode material.

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0036] Example 1

[0037] This embodiment is based on a method for preparing a high-performance lithium manganese oxide positive electrode material under high oxygen atmosphere control, and the specific steps are as follows:

[0038] S1. Weigh the raw materials Li2CO3, Mn3O4, Al2O3, La2O3, and LiF according to the molar ratio of Li, Mn, Al, La, and F of 1.012:1.966:0.02:0.014:0.008. Place the weighed raw materials in a high-speed mixer and mix them evenly at a speed of 600 r / min using a dry mixing method for 1 hour to obtain a precursor powder with uniform composition.

[0039] S2. The precursor powder obtained in step S1 is loaded into a crucible, placed in a controlled atmosphere muffle furnace, and sintered at an oxygen volume fraction of 40% using the following process: heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, performing high-temperature sintering, and finally naturally cooling to obtain a structurally stable sintered product.

[0040] S3. The sintered product obtained in step S2 was crushed by a jaw crusher, and then preliminarily graded by a 100-mesh sieve. Then, it was finely ground by a jet mill to control the particle size D50 of the finished powder to 8-12 μm. The crushed material was further sieved by a 300-mesh sieve to obtain high-performance Li 1.012 Mn 1.966 La 0.014 Al 0.0 2O 3.992 F 0.008 Lithium manganese oxide positive electrode material.

[0041] Example 2

[0042] This embodiment is based on a method for preparing a high-performance lithium manganese oxide positive electrode material under high oxygen atmosphere control, and the specific steps are as follows:

[0043] S1. Weigh the raw materials Li2CO3, Mn3O4, Al2O3, La2O3, and LiF according to the molar ratio of Li, Mn, Al, La, and F of 1.012:1.966:0.02:0.014:0.008. Place the weighed raw materials in a high-speed mixer and mix them evenly at a speed of 600 r / min using a dry mixing method for 1 hour to obtain a precursor powder with uniform composition.

[0044] S2. The precursor powder obtained in step S1 is loaded into a crucible, placed in a controlled atmosphere muffle furnace, and sintered at an oxygen volume fraction of 30% using the following process: heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, performing high-temperature sintering, and finally cooling naturally to obtain a structurally stable sintered product.

[0045] S3. The sintered product obtained in step S2 was crushed by a jaw crusher, and then preliminarily graded by a 100-mesh sieve. Then, it was finely ground by a jet mill to control the particle size D50 of the finished powder to 8-12 μm. The crushed material was further sieved by a 300-mesh sieve to obtain high-performance Li 1.012 Mn 1.966 La 0.014 Al 0.0 2O 3.992 F 0.008 Lithium manganese oxide positive electrode material.

[0046] Comparative Example 1

[0047] This comparative example is based on a method for preparing lithium manganese oxide positive electrode materials under a traditional air atmosphere, and the specific steps are as follows:

[0048] S1. Weigh the raw materials Li2CO3, Mn3O4, Al2O3, La2O3, and LiF according to the molar ratio of Li, Mn, Al, La, and F of 1.012:1.966:0.02:0.014:0.008. Place the weighed raw materials in a high-speed mixer and mix them evenly at a speed of 600 r / min using a dry mixing method for 1 hour to obtain a precursor powder with uniform composition.

[0049] S2. The precursor powder obtained in step S1 is loaded into a crucible, placed in a controlled atmosphere muffle furnace, and sintered at an oxygen volume fraction of 21% using the following process: heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, performing high-temperature sintering, and finally naturally cooling to obtain a structurally stable sintered product.

[0050] S3. The sintered product obtained in step S2 was coarsely crushed by a jaw crusher, initially graded through a 100-mesh sieve, and then finely ground using a jet mill to control the particle size D50 of the finished powder to 8-12 μm. The crushed material was further sieved through a 300-mesh sieve to obtain Li 1.012 Mn 1.966 La 0.014 Al 0.02 O 3.992 F 0.008 Lithium manganese oxide positive electrode material.

[0051] Figure 1 middle, Figure 1 (a) Figure 1 (b) Figure 1(c) Scanning electron microscope (SEM) images of the lithium manganate cathode materials prepared in Example 1, Example 2, and Comparative Example 1, respectively. The images show that the materials prepared in Example 1, Example 2, and Comparative Example 1 all have approximately spherical particle structures. These particles have relatively rough surfaces, exhibiting the characteristics of agglomerates composed of smaller secondary particles. Furthermore, the particle surfaces are uneven, with numerous protrusions and depressions, indicating a high specific surface area, which may facilitate ion transport and charge exchange during electrochemical reactions.

[0052] Performance testing:

[0053] The lithium manganate material obtained in Example 1, Example 2, and Comparative Example 1 was used as the active material and mixed with a binder of polyvinylidene fluoride (PVDF) and a conductive agent of Super P in the following mass ratio: active material: PVDF: Super P = 11: 0.9: 0.7; then, an appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent to prepare a uniform slurry; the slurry was evenly coated on aluminum foil and then vacuum dried to remove the solvent; the dried electrode was further compacted by a roller pressing process to prepare a positive electrode; metallic lithium was used as the negative electrode, LiPF6 electrolyte was used, and a polypropylene microporous membrane was selected as the separator; in a glove box filled with an inert gas (such as argon or nitrogen), the positive electrode, separator, and negative electrode were sequentially assembled into a CR2032 button cell. The electrochemical performance of the assembled CR2032 button cell was tested using a battery charge and discharge tester. Multiple charge and discharge cycles were performed under constant current conditions, and the capacity retention rate of each cycle was recorded.

[0054] Figure 2 、 Figure 3 and Figure 4The capacity retention curves of the lithium manganese oxide positive electrode materials prepared in Example 1 (oxygen volume fraction 40%), Example 2 (oxygen volume fraction 30%) and the comparative example (oxygen volume fraction 21%, i.e., traditional air atmosphere) after 50 cycles at 5C rate at room temperature are shown. As can be seen from the figure, under the same test conditions, the samples prepared in different oxygen concentration atmospheres show obvious differences in electrochemical performance: the lithium manganese oxide material prepared in Example 1 in a high oxygen atmosphere with an oxygen volume fraction of 40% has a capacity retention rate of 99.19% after 50 cycles at 5C rate; the sample prepared in Example 2 in an atmosphere with an oxygen volume fraction of 30% has a capacity retention rate of 98.6%; the sample prepared in ordinary air (oxygen volume fraction of about 21%) in the comparative example has a capacity retention rate of only 97.8%. This shows that by increasing the oxygen volume fraction during the sintering process, the structural stability and cycle performance of the lithium manganate positive electrode material can be effectively improved; especially when the oxygen volume fraction is 40%, the material exhibits better capacity retention ability, showing that high oxygen atmosphere regulation is effective in improving the material lattice oxygen content and promoting Mn 3+ Xiang Mn 4+ It has significant advantages in conversion and inhibition of manganese dissolution, which further verifies the effectiveness of the technical solution of the present invention to improve the performance of lithium manganese oxide positive electrode materials through coordinated regulation of high oxygen atmosphere and material components.

[0055] The above is a detailed introduction to the method for preparing high-performance lithium manganese oxide positive electrode materials based on the regulation of a high oxygen atmosphere disclosed in the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-performance lithium manganate positive electrode materials under high oxygen atmosphere control, characterized in that: The following steps are involved: S1. Weigh the lithium source, manganese source and optional additives according to the designed ratio, place the weighed raw materials in a high-speed mixer, and mix them evenly at a speed of 600 to 800 r / min for 1 to 2 hours using a dry mixing method to obtain a precursor powder with uniform composition; S2. The precursor powder obtained in step S1 is placed in a crucible, placed in a controlled atmosphere muffle furnace, and sintered at a high temperature under an oxidizing atmosphere to obtain a structurally stable sintered product; S3. The sintered product obtained in step S2 is coarsely crushed by a jaw crusher, preliminarily graded through a 100-mesh sieve, and then finely ground using a jet mill to control the particle size D50 of the finished powder to 8 to 12 μm. The ground material is further sieved through a 300-mesh sieve to obtain a high-performance lithium manganese oxide positive electrode material with uniform particle size distribution and high purity.

2. The method for preparing a high-performance lithium manganate cathode material under high oxygen atmosphere control according to claim 1, characterized in that: In step S1, the lithium source is Li2CO3, the manganese source is Mn3O4, and the additives are Al2O3, La2O3, and LiF.

3. The method for preparing a high-performance lithium manganate cathode material under high oxygen atmosphere control according to claim 2, characterized in that: The molar ratio of Li, Mn, Al, La and F in Li2CO3, Mn3O4, Al2O3, La2O3 and LiF is (1-1.03): (1-2): (0-0.03): (0～0.03)：(0～0.01)。 4. The method for preparing a high-performance lithium manganate cathode material under high oxygen atmosphere control according to claim 1, characterized in that: In step S2, the volume fraction of oxygen in the muffle furnace is controlled to be 25% to 100% during the high-temperature sintering.

5. The method for preparing a high-performance lithium manganate cathode material under high oxygen atmosphere control according to claim 4, characterized in that: In step S2, the volume fraction of oxygen in the muffle furnace is controlled to be 30% to 60% during the high-temperature sintering.

6. The method for preparing a high-performance lithium manganate cathode material under high oxygen atmosphere control according to claim 4, characterized in that: In step S2, the high-temperature sintering process in the muffle furnace is as follows: first, heating to 700°C at a heating rate of 1°C / min and keeping warm for 6 hours, then heating to 720°C at a heating rate of 0.5°C / min and keeping warm for 1 hour, and finally naturally cooling to room temperature.

7. The high-performance lithium manganate positive electrode material prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The chemical formula of the high-performance lithium manganate positive electrode material is Li a Mn 2-x-y La x Al y O 4-z F z , where 1≤a≤1.03, 0<x≤0.03, 0<y≤0.03, 0<z≤0.

01.

8. Use of the high-performance lithium manganate cathode material according to claim 7 in lithium-ion batteries.

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