Lithium ion battery positive electrode material transition metal layered oxide and preparation method thereof, positive electrode material and lithium ion battery

Abstract

The invention discloses a lithium ion battery positive electrode material transition metal layered oxide and a preparation method thereof, a positive electrode material and a lithium ion battery, the lithium ion battery positive electrode material transition metal layered oxide comprises a layered oxide LiTMO2 and a Li2O-B2O3-SiO2-MgF2 glass coating layer coating the surface of the layered oxide LiTMO2, and TM in the layered oxide LiTMO2 is selected from at least one of Ni, Co and Mn. Components of the transition metal layered oxide are reasonably designed, Li2O-B2O3-SiO2-MgF2 system glass is selected for coating, the material is resistant to high temperature and can be directly coated on the surface of the layered oxide by adopting a heat treatment method, and the technical bottleneck that when a solution method is adopted, only glass raw materials dissolved in a solvent can be used for melting glass for coating is broken through; and methods such as atomic layer deposition and magnetron sputtering do not need to be adopted for coating the glass.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a transition metal layered oxide for lithium-ion battery cathode material and its preparation method, and also to lithium-ion battery cathode materials and lithium-ion batteries. Background Technology

[0002] Layered oxides, as cathode materials for lithium-ion batteries, have attracted widespread attention due to their advantages of high theoretical specific capacity, high energy density, and ease of synthesis. However, layered oxide materials are prone to side reactions with the electrolyte, which can lead to short battery life, poor rate performance, and performance instability during cycling. These side reactions can cause surface structure reconstruction, excessive metal dissolution, and the formation of microcracks, exposing more reaction sites. Furthermore, electrolyte penetration along cracks can lead to phase transitions and microcrack propagation. Therefore, improving the structural stability of layered oxides, and thus enhancing battery cycle life and rate performance, has become a key issue in lithium-ion battery technology.

[0003] Glass surface coating modification methods can enhance structural stability by suppressing particle erosion by electrolytes and inhibiting particle volume changes. Currently, commonly used coating methods include atomic layer deposition (ALD) and magnetron sputtering; however, these methods suffer from problems such as expensive equipment, low efficiency, and high cost. Specifically: Atomic layer deposition (ALD) has a slow deposition rate. Although it can ensure the uniformity and consistency of the film by depositing single atomic layers one by one, the deposition rate is slow, which limits its application in large-scale production. Moreover, the equipment cost is high. ALD equipment requires precise control of the introduction and cleaning process of the precursor, which increases the complexity of the equipment and the manufacturing cost.

[0004] Magnetron sputtering (MS): High equipment cost. Magnetron sputtering equipment requires complex magnetic field and vacuum systems, resulting in relatively high manufacturing and maintenance costs. Sensitive to process parameters: The process parameters of magnetron sputtering (such as sputtering voltage, current, gas pressure, magnetic field strength, etc.) have a significant impact on the quality and performance of the thin film, requiring precise control and optimization. Limitations: For workpieces of certain specific shapes or sizes, magnetron sputtering may be difficult to achieve uniform sputtering coverage. In particular, the applicability of magnetron sputtering is also limited for applications in certain high-temperature or corrosive environments.

[0005] To address the aforementioned issues with atomic layer deposition (ALD) and magnetron sputtering coating, a solution-based method is commonly used to coat glass onto particle surfaces. The specific process is as follows: (1) First, prepare the solution: Dissolve the glass powder (such as silicate) in a suitable solvent, usually ethanol or water. Ensure that the concentration of the solution is appropriate so that a uniform coating layer is formed on the particle surface.

[0006] (2) Mixing and stirring: Add the particles to be coated (such as silica particles) to the above solution and stir and mix thoroughly. Ensure that the particles are evenly dispersed in the solution.

[0007] (3) Coating process: The matrix particles are dispersed in the solution under stirring conditions, and coating is achieved through adsorption and deposition. Parameters such as coating time and solution concentration are controlled to allow the glass material to deposit on the particle surface. The coating effect can be optimized by adjusting the pH value, temperature, and other conditions of the solution.

[0008] (4) Washing and drying: The deposited mixture was centrifuged and washed several times with ethanol and deionized water to remove uncoated glass material. Finally, it was dried in a vacuum drying oven to remove residual solvent.

[0009] (4) Post-processing: After drying, the coated particles are further processed, such as grinding and screening, to ensure the uniformity of the coating layer and the dispersibility of the particles. Through the above steps, a glass layer can be successfully coated on the surface of the particles, improving the physical and chemical properties of the particles and enhancing their stability and functionality.

[0010] However, the solution method can only use glass raw materials that are uniformly soluble in the solvent to melt glass for coating, and the process is still complex, the synthesis process needs to be strictly controlled, and the synthesis cost is high.

[0011] Therefore, this patent application is filed. Summary of the Invention

[0012] To address the aforementioned technical problems, this invention provides a transition metal layered oxide as a cathode material for lithium-ion batteries, along with its preparation method, cathode material, and lithium-ion battery.

[0013] This invention is achieved through the following technical solution: The first objective of this invention is to provide a transition metal layered oxide for lithium-ion battery cathode material, including layered oxide LiTMO2 and a Li2O-B2O3-SiO2-MgF2 glass coating layer on the surface of layered oxide LiTMO2, wherein TM in layered oxide LiTMO2 is selected from at least one of Ni, Co, and Mn.

[0014] In this invention, the composition of the transition metal layered oxide is rationally designed, and a Li2O-B2O3-SiO2-MgF2 system glass is selected for coating. The advantage of this system glass is that it uses high-temperature resistant components, and the material is resistant to high temperatures. It can be directly coated onto the surface of the layered oxide by heat treatment, which breaks through the technical bottleneck of using solution methods, which can only use glass raw materials dissolved in solvents to melt glass for coating. It also eliminates the need for other glasses, such as CoB metallic glasses, which, although reducing surface oxygen activity and enhancing the mechanical and electrochemical stability of the electrode, still require precise control of synthesis conditions (such as solution concentration and reaction time) using methods such as atomic layer deposition. Otherwise, local uncovered areas are likely to occur. Moreover, the synthesis of metallic glasses involves precious metals (such as cobalt) and complex processes, resulting in high mass production costs.

[0015] Furthermore, in this invention, a Li2O-B2O3-SiO2-MgF2 system glass is selected for coating, which on the one hand hinders the Li on the surface of the material. + The reaction with H2O and CO2 in the air to generate residual alkali significantly improves the air stability of the material, thereby effectively preventing slurry gelation and improving the material's cycling performance. On the other hand, it suppresses the structural changes caused by volume changes in layered transition metal oxide materials during cycling, improving the structural stability of the material during cycling. Furthermore, the LBS-MgF2 glass cladding layer has advantages such as a wide voltage window and good conductivity. The introduction of MgF2 gives the glass cladding layer resistance to HF corrosion, greatly improving the protective effect of the glass cladding layer. In addition, unlike other crystalline cladding layers, amorphous glass has better plasticity, which can offset the stress caused by volume changes during the cycling of layered oxides, which is more conducive to the structural stability of layered oxides.

[0016] Furthermore, the presence of the LBS-MgF2 (i.e., Li2O-B2O3-SiO2-MgF2) glass coating layer in the layered oxide coating of this invention, to a certain extent, avoids direct contact between the material and the electrolyte, ensuring the stability of the material interface, improving the cycle performance of the layered oxide material, and reducing the interfacial resistance for lithium-ion migration. As a preferred design, the layered oxide LiTMO2 is LiNi. i Co j Mn k O2, i+j+k=1, where: 0 <i≤1,0<j≤1,0<k≤1。

[0017] As a preferred design, the particle size D50 of the layered oxide LiTMO2 is 10~25 μm, and the thickness of the Li2O-B2O3-SiO2-MgF2 glass coating layer is 1~15 nm.

[0018] The second objective of this invention is to provide a method for preparing a transition metal layered oxide cathode material for lithium-ion batteries according to any of the above-mentioned methods, comprising the following steps: Obtain layered oxide LiTMO2 powder; Li2O-B2O3-SiO2-MgF2 system glass for surface coating was prepared using high-temperature melt-quenching technology; The glass obtained above is ground into powder, sieved, and then thoroughly ground and mixed with layered oxide LiTMO2 powder in a mortar until homogeneous. The mixture obtained after grinding was heat-treated to obtain a layered oxide coating on the surface of LBS-MgF2 glass.

[0019] As a preferred design, the preparation method of the Li2O-B2O3-SiO2-MgF2 system glass for surface coating is as follows: a. Mix the raw materials and reagents containing Li, B, and Si, along with MgF2, in a mortar for 1 hour; b. The mixture obtained in step a is subjected to high-temperature melting treatment to obtain the Li2O-B2O3-SiO2-MgF2 system glass; c. Quickly pour the molten glass into cold water for quenching, collect it, and then dry it in an oven.

[0020] The glass design based on the Li2O-B2O3-SiO2-MgF2 system in this invention can be heat-treated at high temperatures, and the surface coating can be completed in a single calcination. The method is simple and easy to apply on a large scale.

[0021] As a preferred design, in step a, the Li-containing raw material reagent is at least one of LiOH and Li2CO3, the B-containing raw material reagent is at least one of B2O3 and H3BO3, and the Si-containing raw material reagent is SiO2; And / or, in step b, the high-temperature melting temperature is 850~1050℃, and the high-temperature melting firing time is 1~2h.

[0022] If the temperature is below 850℃, SiO2 may not melt completely, resulting in unreacted particles or crystalline phase residues in the molten glass, forming internal defects (such as bubbles and streaks); it can also cause excessively high viscosity, poor fluidity of the molten glass, difficulty in uniform forming, and easy formation of surface cracks or uneven thickness. If the temperature is above 1050℃, it may cause glass crystallization, initiating unexpected crystallization and destroying the amorphous structure; excessively high temperatures will also increase the preparation cost and cause irreversible damage to the preparation equipment, resulting in no economic benefit.

[0023] As a preferred design, when preparing Li2O-B2O3-SiO2-MgF2 system glass, the molar ratio of Li2CO3, B2O3, SiO2, and MgF2 is 1:1:1:1.

[0024] As a preferred design, the amount of glass added to the Li2O-B2O3-SiO2-MgF2 system is 0.25wt%~1wt% of the mass of layered oxide LiTMO2. If too much glass is added, it will affect the capacity utilization of layered oxide LiTMO2 and reduce the first-efficiency; while if too little is added, it will affect the cycling performance of layered oxide LiTMO2.

[0025] As a preferred design, the heat treatment process is as follows: first, heat treatment at 400-600℃ for 1-3 hours, followed by heat treatment at 700-900℃ for 1-5 hours.

[0026] This invention achieves surface coating in a single calcination process, a simple method suitable for large-scale application. Furthermore, this high-temperature heat treatment method is applicable to coating various glass systems, overcoming the limitations of solution-based methods.

[0027] A third objective of this invention is to provide a lithium-ion cathode material, comprising a transition metal layered oxide as described in any of the preceding claims.

[0028] A fourth objective of the present invention is to provide a lithium-ion battery comprising the lithium-ion electron cathode material as described above.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the layered oxide with surface coating of the present invention, the layered oxide LiTMO2 and the LBS-MgF2 glass coating layer located on the surface of the layered oxide LiTMO2 have the advantage that the glass itself has good air stability, thus preventing the Li on the surface of the layered oxide from oxidizing. + It reacts with H2O and CO2 in the air to generate residual alkali, which greatly improves the air stability of the material, thereby effectively preventing the slurry from freezing and improving the material's cycling performance. On the other hand, it effectively inhibits the structural changes of layered transition metal oxide materials caused by volume changes during cycling, thus improving the structural stability of the material during cycling.

[0030] 2. In the layered oxide with surface coating of the present invention, the presence of LBS-MgF2 glass coating layer avoids direct contact between the material and the electrolyte to a certain extent, ensuring the stability of the material interface and improving the cycle performance of the layered oxide material. Furthermore, since the glass itself contains a large number of lithium ions and has good conductivity, it reduces the interfacial resistance of lithium ion migration.

[0031] 3. Currently, the traditional process for coating glass with layered oxides is the solution method, which involves dissolving the glass raw material in deionized water or anhydrous ethanol, adding the layered oxide, stirring thoroughly, drying, and then performing medium-to-high temperature heat treatment to achieve glass coating. Compared with the solution method for coating glass on the surface of particles, the coating method of this invention is simpler, has fewer steps, and has a higher yield. Furthermore, it can use a variety of different glass systems for coating, while the solution method can only use glass raw materials that are uniformly soluble in the solvent to melt the glass for coating, which is complex, has many steps, and can only process a small number of samples. This method breaks through the limitations of the solution method. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 The X-ray diffraction pattern (XRD) of LBS-MgF2 glass. Figure 2 The X-ray diffraction pattern (XRD) of Example 1 is shown. Figure 3 This is a transmission electron microscope (TEM) image of Example 1. Figure 4 This is a scanning electron microscope (SEM) image of Example 1. Figure 5 A comparison chart of the rate performance of different embodiments; Figure 6 This is a comparison chart of the cyclic performance of different embodiments. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0034] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. The process is performed sequentially. For example, the method includes steps (a) and (b), indicating that the method may include step (a) performed sequentially. (b) may also include steps (b) and (a) performed sequentially. For example, the method may also include step (c). This indicates that step (c) can be added to the method in any order; for example, the method may include steps (a), (b), and (c). It may also include steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0038] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0039] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0040] Example 1: A transition metal layered oxide for lithium-ion battery cathode material is prepared by the following method: 1. Mix Li2CO3, B2O3, SiO2 and MgF2 in a mortar at a molar ratio of 1:1:1:1 for 1 hour to obtain a mixture reagent. Calcinate the mixture at 1000℃ in air atmosphere for 2 hours. After the heat treatment, quickly pour it into ice-cold water for water quenching. Then dry it in an oven at 100℃ for 8 hours to obtain a Li2O-B2O3-SiO2-MgF2 system glass. 2. Weigh out layered oxide LiTMO2 and glass powder in a mass ratio of 1:0.0125, mix them thoroughly in a mortar, and heat the mixture in an electric furnace at 550℃ for 2 hours, followed by heating at 850℃ for 4 hours. After cooling, collect the layered oxide@1.25 glass material (denoted as NCM@1.25G). The layered oxide LiTMO2 can be LiNi. 0.6 Co 0.1 Mn 0.3 O2 is available commercially.

[0041] Example 2: The difference from Example 1 is that in step 2, layered oxide and glass powder are added at a mass ratio of 1:0.0015 (denoted as NCM@0.15G).

[0042] Example 3: The difference from Example 1 is that in step 2, layered oxide and glass powder with a mass ratio of 1:0.02 (denoted as NCM@2G) are added.

[0043] Comparative Example 1: The difference from Example 1 is that in step 2, sintering is first carried out at 200°C for 3 hours, and then the temperature is raised to 400°C and held for 5 hours. The rest is the same as in Example 1.

[0044] Comparative Example 2: The difference from Example 1 is that in step 2, sintering is first carried out at 550°C for 3 hours, and then the temperature is raised to 1000°C and held for 5 hours. The rest is the same as in Example 1.

[0045] Comparative Example 3: The difference from Example 1 is that in step 1, the Li-containing raw material reagent is a mixture of LiOH and Li₂CO₃, and the mass ratio of the two is 1:1. All other aspects are the same as in Example 1.

[0046] The inventors performed XRD characterization on the Li2O-B2O3-SiO2-MgF2 system glass obtained in step 1, and the results are shown in [Figure number missing]. Figure 1 Meanwhile, the final material NCM@1.25G obtained in step 2 was also subjected to XRD standardization. The results are shown below. Figure 2 .from Figure 1 and Figure 2 As can be seen, no impurity peaks appeared in the LBS-MgF2 glass-coated layered oxide, indicating that the glass coating does not cause any changes in the crystal structure of the layered oxide.

[0047] Furthermore, the material obtained in Example 1 was characterized by TEM and SEM morphology, and the results are shown in [Figure 1]. Figure 3 and Figure 4 .from Figure 3 As can be seen, the glass was successfully coated on the surface of the layered positive electrode. The area surrounded by the red dashed line is the glass coating layer. The Fourier image (inset in the upper left corner) proves that the coating layer is an amorphous structure.

[0048] from Figure 4 It can be seen that the layered oxides after heat treatment still maintain the spherical secondary particle morphology, proving that glass coating does not affect the morphology of the layered oxides.

[0049] The inventors applied the layered oxides obtained from the various embodiments and comparative examples to battery assembly and conducted tests. The specific process is as follows: (1) Battery assembly: The product of this invention, conductive agent SuperP, and binder PVDF are mixed at a mass ratio of 90:5:5, and an appropriate amount of NMP is added to prepare a positive electrode material slurry; subsequently, after coating, vacuum drying, rolling, and slicing, coin cells 2025 are assembled and tested. The electrolyte is 1.2 mol / L LiPF6, and the solvent is EC:EMC=3:7 (volume ratio); the separator is Celgard PP membrane.

[0050] (2) Capacity Test: Button cell tests were conducted at a constant temperature of 25℃. 0.1C charge / discharge was performed using the CC / CV method at 2.8 to 4.3V, and the 0.1C discharge capacity was recorded. Results are shown in Table 1 and... Figure 5 As shown in the image.

[0051] (3) Cyclic testing: In a constant temperature environment of 25℃, 100 cycles of 1C charge-discharge were performed using the CC / CV method at 2.8 to 4.3V. The capacity retention rate at the end of the 100th cycle was recorded. The results are shown in Table 1. Figure 6 As shown.

[0052] Table 1 shows the performance test results of the materials prepared in the examples and comparative examples.

[0053] From Table 1 and Figure 5 It can be seen that the cathode material prepared in the examples also has good electrochemical performance and rate performance at 0.1C discharge capacity, and Example 1 can be regarded as the optimal ratio.

[0054] From Table 1 and Figure 6 As can be seen from the data, after 100 cycles at 1C, the capacity retention of Examples 1-3 is significantly higher than that of the layered oxide, indicating that coating with LBS-MgF2 glass can improve the cycling stability of ternary layered materials.

[0055] Analysis of the comparative examples reveals that the cathode materials in the comparative examples have significantly lower discharge capacities at 0.1C than those in the embodiments, and their initial efficiency and capacity retention after 100 cycles at 1C are also significantly lower. This indicates that a high-performance layered oxide can only be obtained under the preparation conditions of this invention.

[0056] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A transition metal layered oxide for lithium-ion battery cathode material, characterized in that, It includes layered oxide LiTMO2 and a Li2O-B2O3-SiO2-MgF2 glass coating layer on the surface of layered oxide LiTMO2, wherein TM in layered oxide LiTMO2 is selected from at least one of Ni, Co and Mn.

2. The lithium-ion battery cathode material transition metal layered oxide according to claim 1, characterized in that, The layered oxide LiTMO2 is LiNi. i Co j Mn k O2, i+j+k=1, where: 0 <i≤1,0<j≤1,0<k≤1。 3. A transition metal layered oxide for lithium-ion battery cathode material according to claim 1, characterized in that, The particle size D50 of the layered oxide LiTMO2 is 10~25 μm, and the thickness of the Li2O-B2O3-SiO2-MgF2 glass coating layer is 1~15 nm.

4. A method for preparing a transition metal layered oxide cathode material for a lithium-ion battery according to any one of claims 1 to 3, characterized in that, Includes the following steps: Obtain layered oxide LiTMO2 powder; Li2O-B2O3-SiO2-MgF2 system glass for surface coating was prepared using high-temperature melt-quenching technology; The glass obtained above is ground into powder, sieved, and then thoroughly ground and mixed with layered oxide LiTMO2 powder in a mortar until homogeneous. The mixture obtained after grinding was heat-treated to obtain a layered oxide coating on the surface of LBS-MgF2 glass.

5. The method for preparing a transition metal layered oxide cathode material for a lithium-ion battery according to claim 4, characterized in that, The preparation method of the Li2O-B2O3-SiO2-MgF2 system glass for surface coating is as follows: a. Mix the raw materials and reagents containing Li, B, and Si, along with MgF2, in a mortar for 1 hour; b. The mixture obtained in step a is subjected to high-temperature melting treatment to obtain the Li2O-B2O3-SiO2-MgF2 system glass; c. Quickly pour the molten glass into cold water for water quenching, collect it, and then dry it in an oven.

6. A method for preparing a transition metal layered oxide for a lithium-ion battery cathode material according to claim 5, characterized in that, In step a, the Li-containing raw material reagent is at least one of LiOH and Li2CO3, the B-containing raw material reagent is at least one of B2O3 and H3BO3, and the Si-containing raw material reagent is SiO2. And / or, in step b, the high-temperature melting temperature is 850~1050℃, and the high-temperature melting firing time is 1~2 h.

7. The method for preparing a transition metal layered oxide cathode material for a lithium-ion battery according to claim 4, characterized in that, When preparing the Li2O-B2O3-SiO2-MgF2 system glass, the molar ratio of Li2CO3, B2O3, SiO2, and MgF2 is 1:1:1:

1.

8. The method for preparing a transition metal layered oxide cathode material for a lithium-ion battery according to claim 4, characterized in that, The amount of Li2O-B2O3-SiO2-MgF2 glass added is 0.25wt%~1wt% of the mass of layered oxide LiTMO2; And / or, the heat treatment process is as follows: first, heat treatment at 400-600℃ for 1-3 h, followed by heat treatment at 700-900℃ for 1-5 h.

9. A lithium-ion battery cathode material, characterized in that, This includes transition metal layered oxides prepared by the method as described in any one of claims 1 to 3 or 4 to 8.

10. A lithium-ion battery, characterized in that, Including the lithium-ion electronic cathode material as described in claim 9.

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