Composite positive electrode material, preparation method thereof and positive electrode plate

Abstract

The invention relates to a composite positive electrode material, a preparation method thereof and a positive electrode plate, the composite positive electrode material comprises a positive electrode material and a metal organic framework arranged on at least part of the surface of the positive electrode material, and the metal organic framework comprises at least one of MOF-5-NH2, MOF-5-SH, MOF-5-OH and MIL-125-NH2. In the composite positive electrode material, a transition metal-polar functional group coordination is adopted to optimize a positive electrode material interface, polar repulsion and nano confinement can accelerate dissociation of lithium ion-solvent clusters, and formation of rich inorganic components in a positive electrode-electrolyte interface (CEI) is promoted; and capacity fading and battery failure caused by interface side reaction and uneven distribution of internal stress of particles are effectively avoided, so that the problem of long cycle stability of the high-voltage positive electrode is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a composite positive electrode material, a preparation method thereof and a positive electrode sheet. BACKGROUND

[0002] Lithium ion batteries have a long service life, high energy density and low self-discharge rate, and are widely used. The positive electrode material is a core component of the lithium ion battery. In order to further improve the capacity and reduce the cost, the working voltage is increased to more than 4.55 V to release more lithium ions, which is an effective strategy to promote the positive electrode material to obtain higher energy density. However, due to the sudden change of the lattice volume during the charging and discharging process, the positive electrode material particles will be subjected to internal stress and produce microcracks, which will continuously expand along the interface between the active material and the electrolyte, accelerate the particle pulverization and electrolyte decomposition, and cause the cycle capacity to decay. SUMMARY

[0003] In view of this, the present application provides a composite positive electrode material and a preparation method thereof to solve at least one of the above technical problems. In addition, the present application also provides a positive electrode sheet.

[0004] In a first aspect, the present application provides a composite positive electrode material, which comprises a positive electrode material and a metal organic framework arranged on at least part of the surface of the positive electrode material, and the metal organic framework comprises at least one of MOF-5-NH2, MOF-5-SH, MOF-5-OH and MIL-125-NH2.

[0005] Based on the first aspect, in some possible implementation manners, the positive electrode material comprises one or both of NCM92 and LCO.

[0006] Based on the first aspect, in some possible implementation manners, the mass ratio of the metal organic framework to the positive electrode material is (0.05-0.2):1.

[0007] Based on the first aspect, in some possible implementation manners, the metal organic framework is provided with a pore structure, and the pore diameter of the pore structure is 0.6 nm to 20 nm.

[0008] In a second aspect, the present application provides a preparation method of the above-mentioned composite positive electrode material, which comprises: mixing the metal organic framework and the positive electrode material by ball milling to obtain the composite positive electrode material.

[0009] Based on the second aspect, in some possible implementation manners, the rotation speed of the ball milling is 50 rpm to 600 rpm, and the ball milling time is 1 h to 6 h.

[0010] Based on the second aspect, in some possible implementations, the metal organic framework is prepared from a metal salt, an organic ligand and a solvent by a hydrothermal method, the temperature of the hydrothermal method is 100° C. to 180° C., and the time of the hydrothermal method is 6 h to 8 h.

[0011] Based on the second aspect, in some possible implementations, the mass ratio of the metal salt to the organic ligand is 1:1 to 10:1.

[0012] Based on the second aspect, in some possible implementations, the preparation method further includes drying the metal-organic framework at a temperature of 90° C. to 120° C. for a time of 4 h to 24 h.

[0013] In a third aspect, the present application provides a positive electrode plate, which includes the above-mentioned composite positive electrode material.

[0014] Compared with the existing technology, the composite positive electrode material of the present application uses transition metal-polar functional group coordination to optimize the positive electrode material interface. The polar groups interact with anions to form polar channels, which repel solvent molecules to reduce the desolvation energy barrier. Combined with the nano-confinement effect, it can accelerate the dissociation of lithium ion-solvent clusters and promote the formation of inorganic-rich components in the positive electrode-electrolyte interface (CEI), effectively avoiding capacity attenuation and battery failure caused by interfacial side reactions and uneven stress distribution inside the particles, thereby solving the problem of long-cycle stability of high-voltage positive electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of MOF-5-NH2 provided in Example 1 of the present application.

[0016] Figure 2 This is the SEM image of MOF-5 provided in Comparative Example 2 of this application.

[0017] Figure 3 XRD patterns of MOF-5-NH2 and MOF-5 provided in Example 1 and Comparative Example 2 of the present application.

[0018] Figure 4 This is a linear scanning curve diagram of a lithium-ion battery assembled with the composite positive electrode materials provided in Example 1 and Comparative Example 1 of the present application.

[0019] Figure 5 The cycling performance test results of the lithium-ion battery assembled with the positive electrode sheet provided in Example 1 of the present application at a cut-off voltage of 4.4 V.

[0020] Figure 6 The cycling performance test results of lithium-ion batteries assembled with the positive electrode sheets provided in Example 1, Comparative Example 1, and Comparative Example 2 of the present application at a cutoff voltage of 4.6 V are shown.

[0021] Figure 7 The cycle performance test results of the lithium ion battery assembled with the positive electrode plate provided in Example 3 of the present application at a 4.6 V cut-off voltage.

[0022] Figure 8 The FIB-SEM image of the composite positive electrode material provided in Comparative Example 1 of the present application after high-voltage cycling.

[0023] Figure 9 The FIB-SEM image of the composite positive electrode material provided in Example 1 of the present application after high-voltage cycling.

[0024] Figure 10 The surface XPS spectrum of the composite positive electrode material provided in Comparative Example 1 of the present application after high-voltage cycling.

[0025] Figure 11 The surface XPS spectrum of the composite positive electrode material provided in Example 1 of the present application after high-voltage cycling.

[0026] Figure 12 The cycle performance test results of the lithium ion battery assembled with the positive electrode plate provided in Example 2 and Comparative Example 3 of the present application at a 4.5 V cut-off voltage.

[0027] Figure 13 The cycle performance test results of the lithium ion battery assembled with the composite positive electrode material provided in Example 1 and Comparative Example 1 of the present application at a 4.6 V cut-off voltage, 0.5 C current density under high loading condition (8 mg / cm 2 ).

[0028] Figure 14 The cycle performance test results of the lithium ion battery assembled with the composite positive electrode material provided in Example 1 of the present application at a 4.6 V cut-off voltage, 1 C current density under high loading condition (8 mg / cm 2 ). DETAILED DESCRIPTION

[0029] Embodiments of the present application are described in detail below. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the present application belongs; the embodiments of the present application and the features in the embodiments can be combined with each other without conflict; in the following description, many specific details are set forth in order to provide a thorough understanding of the present application, and the described embodiments are only part of the embodiments of the present application, but not all the embodiments.

[0030] In the related art, the high-voltage cycle stability of the positive electrode material (such as LCO) can be enhanced to a certain extent through surface coating, element doping, and sintering process optimization, but these methods are often complex and difficult to scale. Therefore, the present application provides an improved positive electrode material and a preparation method thereof, which achieves the purpose of improving the high-voltage cycle stability of the positive electrode material.

[0031] Based on this, an embodiment of the present application provides a composite positive electrode material, which comprises a positive electrode material and a metal organic framework arranged on at least part of the surface of the positive electrode material, and the metal organic framework comprises at least one of MOF-5-NH2, MOF-5-SH, MOF-5-OH, and MIL-125-NH2.

[0032] Modifying the positive electrode material by the metal organic framework material is beneficial to improve the cycle stability of the positive electrode material under high pressure working conditions. The present application finds that, compared with the prior art, the use of the above metal organic framework can optimize the interface of the positive electrode material by coordination of transition metals with functional groups such as amino, mercapto, and hydroxyl, which is beneficial to promote the formation of inorganic components rich in the positive electrode-electrolyte interface (CEI). Therefore, the composite positive electrode material of the present application can effectively avoid capacity attenuation and battery failure caused by interface side reactions and uneven stress distribution in the particle, thereby solving the problem of insufficient long cycle stability of the high-voltage positive electrode.

[0033] In some embodiments, the mass ratio of the metal organic framework to the positive electrode material is (0.05-0.2):1. For example, the mass ratio of the metal organic framework to the positive electrode material can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, or any value within the range formed by any two of the above values.

[0034] In some embodiments, the metal organic framework is provided with a pore structure, and the pore diameter of the pore structure is 0.6 nm to 20 nm. For example, the pore diameter of the pore structure can be 0.6 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or any value within the range formed by any two of the above values. Controlling the pore structure within the above range is beneficial to promote the transmission of active ions (such as lithium ions).

[0035] In some embodiments, the positive electrode material comprises one or both of NCM92 and LCO.

[0036] The embodiment of the present application also provides a preparation method of the composite positive electrode material, comprising: mixing the metal organic framework and the positive electrode material through ball milling to obtain the composite positive electrode material. The metal organic framework is coated on the surface of the positive electrode material through ball milling, which can reduce the heat treatment process and help maintain the structural integrity of the metal organic framework material on the basis of uniform coating of the metal organic framework and the positive electrode material.

[0037] In some embodiments, the rotation speed of the ball milling is 50 rpm to 600 rpm, and the ball milling time is 1 h to 6 h. For example, the rotation speed of the ball milling can be 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, or any value within a range defined by any two of the above values. The ball milling time can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, or any value within a range defined by any two of the above values. Controlling the rotation speed and time of the ball milling within the above range is conducive to improving the uniformity of the coating of the metal organic framework on the positive electrode material.

[0038] In some embodiments, the metal organic framework is prepared by a hydrothermal method from a metal salt, an organic ligand, and a solvent, the temperature of the hydrothermal method is 100 ℃ to 180 ℃, and the time of the hydrothermal method is 6 h to 8 h. For example, the temperature of the hydrothermal method can be 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, or any value within a range defined by any two of the above values. The time of the hydrothermal method can be 6 h, 6.3 h, 6.5 h, 6.8 h, 7 h, 7.2 h, 7.5 h, 7.8 h, 8 h, or any value within a range defined by any two of the above values. Controlling the temperature and time of the hydrothermal method within the above range is conducive to controlling the size and crystallinity of the obtained metal organic framework, and the size and crystallinity obtained under this condition are more conducive to exerting the coordination role of the specific metal organic framework, and are conducive to further improving the high-pressure cycle stability of the obtained composite positive electrode material.

[0039] In some embodiments, the mass ratio of the metal salt to the organic ligand is 1:1 to 10:1. For example, the mass ratio of the metal salt to the organic ligand can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any value within a range defined by any two of the above values. Controlling the mass ratio of the metal salt to the organic ligand within the above range is conducive to promoting the synthesis of the specific metal organic framework.

[0040] In some embodiments, the preparation method further comprises drying the metal organic framework, the drying temperature is 90-120℃, and the drying time is 4-24 h. For example, the drying temperature can be 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, or any value within the range between any two of the above values. The drying time can be 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any value within the range between any two of the above values. Controlling the drying temperature and time within the above range is conducive to promoting the volatilization of the solvent and reducing the influence of residual solvent on the process of obtaining the metal organic framework-coated positive electrode material.

[0041] The embodiment of the present application also provides a positive electrode tab, comprising the composite positive electrode material described above.

[0042] The positive electrode tab of the present application has good high-voltage cycle stability.

[0043] The scheme of the present application will be explained below in combination with examples. Those skilled in the art will understand that the following examples are only used to explain the present application and cannot be understood as a limitation of the present application. Unless otherwise stated, the reagents, software and instruments involved in the following examples, which are not specifically stated, are all conventional commercially available products or open source.

[0044] Example 1: Step 1: Dissolve the metal source (1500 mg) and the functionalized terephthalic acid (300 mg) in 30 mL of N,N-dimethylformamide (DMF), stir at room temperature for 1 h to make them uniformly mixed, transfer to a high-pressure reaction kettle, react at 180℃ for 12 h, wash the powder with dichloromethane for 3 times, and dry in a vacuum box for 10 h to obtain brown crystals, i.e. the functionalized metal organic framework material. In this embodiment, the metal source is zinc nitrate trihydrate, the functionalized terephthalic acid is 2-amino terephthalic acid, and the functionalized metal organic framework material is MOF-5-NH2.

[0045] Step 2: Mix the positive electrode material LCO with the metal organic framework prepared in step 1 by a ball milling method at a mass ratio of 10:1: the rotation speed of the ball mill is 200 rpm, and the ball milling time is 4 h to obtain LCO-MOF-5-NH2; Step 3: The material prepared in step 2, conductive carbon black, and polyvinylidene fluoride were weighed according to a mass ratio of 9:1:1, and were placed in a 5 mL shaking tank. The total mass of the material was 200 mg. Zirconium oxide grinding beads with a diameter of 3 mm were used. Then, a micro-shaking instrument was used at a speed of 280 r / min for 9 min. Subsequently, the material was coated on the surface of an aluminum foil. After drying, a positive electrode sheet was prepared.

[0046] Example 2: The difference from Example 1 is that in step 2, NCM92 is used as the positive electrode material to obtain NCM92-MOF-5-NH2.

[0047] Example 3: The difference from Example 1 is that in step 2, MOF-5-NH2 in the functionalized metal organic framework is replaced by MIL-125-NH2. After being compounded with the positive electrode material LCO, LCO-MIL-125-NH2 is obtained.

[0048] The preparation method of MIL-125-NH2 includes: 800 mg of 2-amino terephthalic acid is added to a mixture of 11.25 mL of DMF and 3.75 mL of methanol, and stirred uniformly. Then, 0.45 mL of titanium isopropylate is slowly added dropwise. Then, it is transferred to a high-pressure reaction kettle and reacted at 150 °C for 12 h. Then, it is dried in a vacuum oven to obtain MIL-125-NH2.

[0049] Comparative Example 1: The difference from Example 1 is that no metal organic framework is added in the process of preparing the electrode sheet.

[0050] Comparative Example 2: The difference from Example 1 is that in step 2, the functionalized metal organic framework material is replaced by a non-functionalized metal organic framework material. In this comparative example, the non-functionalized metal organic framework material is MOF-5. After being compounded with the positive electrode material LCO, LCO-MOF-5 is obtained.

[0051] The preparation method of the non-functionalized metal organic framework (taking MOF-5 as an example) includes: metal salt (zinc nitrate 1500 mg) and terephthalic acid (300 mg) are dissolved in 30 mL of DMF, and stirred at room temperature for 1 h to make them uniformly mixed. Then, it is transferred to a reaction kettle and reacted at 180 °C for 12 h. The powder is washed with dichloromethane for 3 times and dried in a vacuum oven for 10 h to obtain white crystals, i.e. MOF-5.

[0052] Comparative Example 3: The difference from Comparative Example 2 is that LCO is replaced by NCM92 in the process of preparing the electrode sheet.

[0053] The application performs morphology characterization on the metal organic frameworks involved in the examples and the comparative examples by scanning electron microscopy (SEM). Taking Example 1 and Comparative Example 2 as examples, please refer to Figure 1 The SEM image of MOF-5-NH2 prepared in Example 1 at 10,000 times magnification shows particles of different sizes (100 nm-200 nm); please refer to Figure 2 The SEM image of MOF-5 prepared in Comparative Example 2 at 10,000 times magnification shows flakes of different sizes (0.1 μm-3 μm).

[0054] The application also performs crystallization characterization on the metal organic frameworks involved in the examples and the comparative examples by X-ray diffraction (XRD). Taking Example 1 and Comparative Example 2 as examples, please refer to Figure 3 Both MOF-5-NH2 of Example 1 and MOF-5 of Comparative Example 2 show excellent crystallinity.

[0055] The application also assembles the positive electrode sheets of Examples 1-3 and Comparative Examples 1-3 into lithium ion batteries, respectively, and performs the following performance tests on the lithium ion batteries of Examples 1-3 and Comparative Examples 1-3: 1. The assembled batteries are left to stand at room temperature for 12 h, and battery tests are performed using a new battery test system, 0.5 C charging and discharging, and the cutoff voltage is 4.4 V, to test the discharge specific capacity and coulombic efficiency after cycling.

[0056] 2. The assembled batteries are left to stand at room temperature for 12 h, and battery tests are performed using a new battery test system, 0.5 C charging and discharging, and the cutoff voltage is 4.6 V, to test the discharge specific capacity and coulombic efficiency after cycling.

[0057] 3. The positive electrode material after high-voltage cycling is tested by focused ion beam scanning electron microscopy (FIB-SEM).

[0058] 4. The positive electrode sheet after high-voltage cycling is analyzed by X-ray photoelectron spectroscopy (XPS).

[0059] 5. The lithium ion batteries are assembled according to the positive electrode loading of 8 mg / cm 2 The lithium ion batteries are assembled, the assembled batteries are left to stand at room temperature for 12 h, and battery tests are performed using a new battery test system, 0.5 C charging and discharging, and the cutoff voltage is 4.6 V, to test the discharge specific capacity and coulombic efficiency.

[0060] Please refer to Figure 4 Compared with Comparative Example 1, the functionalized metal organic framework material (MOF-5-NH2) is compounded with the positive electrode in Example 1, and the high-pressure resistance of the system is significantly improved from 4.0 V to 5.0 V. In addition, please refer to Figure 5 whereinFigure 5 The first curve from top to bottom represents the coulombic efficiency of the lithium ion battery of Example 1 after cycling, and the second curve represents the specific capacity change of the lithium ion battery of Example 1 after cycling, wherein the change of coulombic efficiency after cycling please refer to the horizontal coordinate and the right vertical coordinate, and the change of specific capacity after cycling please refer to the horizontal coordinate and the left vertical coordinate. It can be seen from Figure 5 that the functionalized metal organic framework material (MOF-5-NH2) composite lithium cobalt oxide anode in Example 1 has no obvious attenuation in cycle performance after 150 cycles at a low cut-off voltage.

[0061] Please refer to Figure 6 , which shows the cycle performance test results of the lithium ion batteries of Example 1, Comparative Example 1 and Comparative Example 2 after the cut-off voltage is raised. Among them Figure 6 the first curve from top to bottom represents the coulombic efficiency of the lithium ion battery of Example 1 after cycling, and the remaining curves respectively represent the specific capacity change of the lithium ion batteries of Example 1, Comparative Example 1 and Comparative Example 2 after cycling. It can be seen from Figure 6 that compared with Comparative Example 1 and Comparative Example 2, the functionalized metal organic framework material (MOF-5-NH2) composite lithium cobalt oxide anode in Example 1 has better high-voltage stability, and the capacity retention rate can still be maintained at 80.1% after 700 cycles.

[0062] Please refer to Figure 7 , wherein Figure 7 the first curve from top to bottom represents the coulombic efficiency of the lithium ion battery of Example 3 after cycling, and the second curve represents the specific capacity change of the lithium ion battery of Example 3 after cycling. It can be seen from Figure 7 that the functionalized metal organic framework material (MIL-125-NH2) composite lithium cobalt oxide prepared in Example 3 has better high-voltage stability, and the capacity retention rate is close to 80% after 400 cycles, which is due to the fact that the polar functional group can effectively promote the desolvation process, and the pore size of MOF-5-NH2 (12.0 Å) material itself is larger than that of MIL-125-NH2 (6.8 Å), which has lower tortuosity and is more conducive to the transport of lithium ions, thereby having better stability.

[0063] Please refer to Figure 8 and Figure 9 , after the cycle test of the positive electrode material of Comparative Example 1, obvious cracks appear in the positive electrode material; the positive electrode material of Example 1 does not have obvious cracks after the cycle test, indicating that the metal organic framework material can effectively inhibit the interface side reaction and maintain the integrity of the positive electrode.

[0064] Please refer to Figure 10 and Figure 11The interface film (CEI) formed on the positive electrode surface is mainly formed by the oxidative decomposition of the solvent. The XPS spectrum shows that the CEI on the positive electrode of Comparative Example 1 is mainly composed of organic components, while the CEI formed on the positive electrode of Example 1 is rich in inorganic components. LiF can effectively maintain the stability of the positive electrode structure and effectively inhibit the oxidative decomposition of the electrolyte and the accumulation of by-products at high voltage.

[0065] Referring to Figure 12 After the functionalized metal organic framework material (MOF-5-NH2) prepared in Example 2 is combined with NCM92, the lithium ion battery obtained has excellent cycle performance at a current density of 0.5 C, even after 200 cycles, still has a capacity higher than 170 mAh / g, and the capacity retention rate is 81% after nearly 240 cycles, which is higher than the capacity retention rate of 70% of Comparative Example 3.

[0066] Referring to Figure 13 , wherein Figure 13 In FIG. 2, the first curve from top to bottom represents the coulombic efficiency of the lithium ion battery of Example 1 after cycling, and the remaining curves represent the specific capacity changes of the lithium ion batteries of Example 1 and Comparative Example 1 after cycling, respectively. It can be seen from Figure 13 that the lithium ion battery of Example 1 has excellent cycle performance at a current density of 0.5 C under a high loading amount (8 mg cm -2 ), even after 260 cycles, still has a capacity higher than 180 mAh / g, and the capacity retention rate is about 90%, which is significantly better than that of Comparative Example 1. Referring to Figure 14 , wherein Figure 14 In FIG. 3, the first curve from top to bottom represents the coulombic efficiency of the lithium ion battery of Example 1 after cycling, and the second curve represents the specific capacity change of the lithium ion battery of Example 1 after cycling. It can be seen from Figure 14 that the lithium battery of Example 1 has excellent cycle performance at a current density of 1 C, even after 260 cycles, the capacity retention rate is still 74.2%. This is because the anions can be electrostatically adsorbed by the NH2 in the channel to form a polar channel, repelling solvent molecules, thereby promoting the desolvation ability of lithium ions; the functionalized metal organic framework material has a nanochannel that can effectively promote the transport of lithium ions; ultimately, the polar repulsion and nanolimitation effect accelerate the dissociation of lithium ion-solvent clusters, while ensuring that the interface is rich in anions to promote the formation of inorganic interfaces.

[0067] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A composite positive electrode material, characterized in that The composite positive electrode material includes a positive electrode material and a metal organic framework provided on at least a portion of the surface of the positive electrode material, wherein the metal organic framework includes at least one of MOF-5-NH2, MOF-5-SH, MOF-5-OH and MIL-125-NH2.

2. The composite cathode material according to claim 1, wherein The positive electrode material includes one or both of NCM92 and LCO.

3. The composite cathode material according to claim 1, wherein The mass ratio of the metal organic framework to the positive electrode material is (0.05~0.2):

1.

4. The composite cathode material according to claim 1, wherein The metal organic framework is provided with a pore structure, and the pore diameter of the pore structure is 0.6 nm to 20 nm.

5. A method for preparing a composite positive electrode material according to claim 1, characterized in that: The preparation method comprises: The metal organic framework and the cathode material are mixed by ball milling to obtain the composite cathode material.

6. The preparation method according to claim 5, wherein The ball milling speed is 50 rpm to 600 rpm, and the ball milling time is 1 h to 6 h.

7. The preparation method according to claim 5, wherein The metal organic framework is prepared from a metal salt, an organic ligand and a solvent by a hydrothermal method. The temperature of the hydrothermal method is 100° C. to 180° C., and the time of the hydrothermal method is 6 h to 8 h.

8. The preparation method according to claim 7, wherein The mass ratio of the metal salt to the organic ligand is 1:1 to 10:

1.

9. The preparation method according to claim 7, wherein The preparation method further includes drying the metal organic framework, wherein the drying temperature is 90° C. to 120° C. and the drying time is 4 h to 24 h.

10. A positive electrode plate, characterized in that: The positive electrode plate comprises the composite positive electrode material according to any one of claims 1 to 4.

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