Modified lithium nickel manganese oxide positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a modified lithium nickel manganese oxide positive electrode material as well as a preparation method and application thereof, and relates to the technical field of lithium batteries. The modified lithium nickel manganese oxide positive electrode material provided by the invention comprises a lithium nickel manganese oxide positive electrode material body and a modified coating layer, wherein a modified substance in the modified coating layer is obtained by carrying out esterification reaction on an MOF material and organic acid. The organic acid and the MOF material are subjected to esterification reaction, and ester groups are introduced into a modified substance, so that gas production can be remarkably reduced, meanwhile, the stability of the material can be improved, and the cycle performance of the material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a modified lithium nickel manganese oxide positive electrode material, a preparation method and application thereof. Background Art

[0002] At present, lithium-ion batteries have been widely used. The positive electrode material of lithium batteries is the key factor that determines the performance of batteries. The main positive electrode materials of lithium batteries currently studied are LiCoO2, LiMnO4, LiFePO4, LiNi x Co y Mn 1-x-y O2, etc. Spinel nickel manganese oxide lithium cathode materials have been widely studied due to their excellent rate performance, high operating voltage, and low cost.

[0003] However, the large-scale application of spinel nickel manganese oxide cathode materials is seriously inhibited by the unstable surface structure of spinel nickel manganese oxide cathode materials and the dissolution of metal manganese during the cycle. In addition, spinel nickel manganese oxide cathode materials also have the problem of gas production, which will greatly affect the cycle performance of the battery.

[0004] Therefore, there is an urgent need to improve the lithium nickel manganese oxide positive electrode material to improve its cycle performance.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a modified lithium nickel manganese oxide positive electrode material, a preparation method and application thereof, aiming to reduce gas production and improve the cycle performance of the battery.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a modified lithium nickel manganese oxide positive electrode material, comprising a lithium nickel manganese oxide positive electrode material body and a modified coating layer coated on the lithium nickel manganese oxide positive electrode material body;

[0009] The modified substance contained in the modified coating layer is obtained by esterification reaction between MOF material and organic acid.

[0010] In an optional embodiment, the metal ion for preparing the MOF material is selected from at least one of zinc ion, aluminum ion, iron ion and copper ion, preferably zinc ion;

[0011] And / or, the organic ligand for preparing the MOF material is selected from at least one of 1,4-benzenedicarboxylic acid and terephthalic acid;

[0012] and / or, the organic acid is at least one selected from triformic acid and acetic acid, preferably triformic acid;

[0013] And / or, when preparing the modified substance, the mass ratio of the MOF material and the organic acid is controlled to be (1-3):1.

[0014] In an optional embodiment, the mass ratio of the modified coating layer to the lithium nickel manganese oxide positive electrode material body is (1-5):100.

[0015] In a second aspect, the present invention provides a method for preparing a modified lithium nickel manganese oxide positive electrode material according to any one of the aforementioned embodiments, comprising: forming a modified coating layer on a body of the lithium nickel manganese oxide positive electrode material.

[0016] In an optional embodiment, the MOF material and the organic acid are mixed and reacted to obtain a reaction solution containing the modified substance, and the reaction solution is coated on the main body of the lithium nickel manganese oxide positive electrode material by a wet coating method, and then dried.

[0017] In an optional embodiment, the mass fraction of the modified substance in the reaction solution is 25%-35%, and the volume of the reaction solution corresponding to each 500g of the lithium nickel manganese oxide positive electrode material body is 500mL-800mL;

[0018] And / or, the drying temperature is controlled to be 40°C-60°C and the drying time is controlled to be 10h-15h.

[0019] In an optional embodiment, the process of preparing the reaction solution includes: mixing the MOF material, the organic acid and water, reacting at 20° C.-40° C. for 1 h-5 h, and then washing;

[0020] Preferably, the mass ratio of MOF material to organic acid is (1-3):1.

[0021] In an optional embodiment, the preparation process of the MOF material includes: dissolving a metal salt to obtain a metal salt solution, dissolving an organic ligand to obtain an organic ligand solution, adding the metal salt solution to the organic ligand solution, and reacting at 20° C. to 30° C. for 20 h to 30 h;

[0022] Preferably, the molar ratio of the metal ion to the organic ligand in the metal salt is (1.5-2.0):1;

[0023] Preferably, the metal salt solution is obtained by mixing a metal salt and water, and the mass ratio of the metal salt to water is 1:(5-9);

[0024] Preferably, the organic ligand solution is obtained by mixing an organic ligand and an organic solvent, and the mass ratio of the organic ligand to the organic solvent is 1:(20-25);

[0025] Preferably, the preparation process of the MOF material further comprises: solid-liquid separation after the reaction is completed, and washing and drying the obtained solid material.

[0026] In a third aspect, the present invention provides a positive electrode plate, comprising any of the modified lithium nickel manganese oxide positive electrode materials in the aforementioned embodiments or a modified lithium nickel manganese oxide positive electrode material prepared by any of the preparation methods in the aforementioned embodiments.

[0027] In a fourth aspect, the present invention provides a lithium battery comprising the positive electrode sheet of the aforementioned embodiment.

[0028] The present invention has the following beneficial effects: the modified lithium nickel manganese oxide positive electrode material provided by the present invention comprises a lithium nickel manganese oxide positive electrode material body and a modified coating layer, and the modified substance in the modified coating layer is obtained by esterification reaction between a MOF material and an organic acid. By carrying out an esterification reaction between an organic acid and a MOF material, an ester group is introduced into the modified substance, which can significantly reduce gas production, and at the same time can also increase material stability and improve the material's cycle performance. This is mainly due to the fact that the hanging energy groups on the MOF, such as OH and OOH groups, form a chelating effect to capture transition metal ions, and at the same time, the synthesized material has stable positive electrode material particles, which hinders the contact and oxidation of the electrolyte with the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a SEM image of the modified lithium nickel manganese oxide positive electrode material prepared in Example 1; in the image, (a) and (b) represent different magnifications. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0032] In view of the problems that the existing nickel manganese oxide positive electrode materials produce a lot of gas and have poor material stability, an embodiment of the present invention provides a modified nickel manganese oxide positive electrode material, including a nickel manganese oxide positive electrode material body and a modified coating layer coated on the nickel manganese oxide positive electrode material body; wherein the modified substance contained in the modified coating layer is obtained by the esterification reaction of MOF material and organic acid.

[0033] It should be noted that the modified substance in the modified coating layer provided by the present invention is obtained by esterification reaction of MOF material and organic acid. The introduction of ester groups into the modified substance can significantly reduce gas production, while also increasing material stability and improving the material's cyclic performance.

[0034] In some embodiments, the metal ions used to prepare the MOF material are selected from at least one of zinc ions, aluminum ions, iron ions and copper ions, and the above metal ions are suitable as centers for combining with organic ligands to prepare framework materials with stable performance. In a preferred embodiment, the metal ions used to prepare the MOF material are zinc ions. Using zinc ions as metal ions can make the prepared MOF material easier to be coated on the main body of the lithium nickel manganese oxide positive electrode material, thereby improving the cycle performance of the positive electrode material.

[0035] Furthermore, the organic ligand for preparing the MOF material is selected from at least one of 1,4-benzenedicarboxylic acid and terephthalic acid. The organic ligand for preparing the MOF material can be any one or more of the above. By combining the organic ligand with the metal ion as the center, a stable metal framework organic compound is obtained.

[0036] Furthermore, the organic acid for esterification with the MOF material is selected from at least one of triformic acid and acetic acid, and the organic acid can be any one or more of the above, preferably triformic acid. When preparing the modified substance, the mass ratio of the MOF material and the organic acid is controlled to be (1-3):1, such as 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, etc.

[0037] Furthermore, the mass ratio of the modified coating layer to the lithium nickel manganese oxide positive electrode material body is (1-5):100, such as 1:100, 2:100, 3:100, 4:100, 5:100, etc. The coating amount of the modified coating layer is preferably controlled within the above range, which can better reduce gas production, increase material stability, and improve the cycle performance of the battery.

[0038] The embodiment of the present invention provides a method for preparing a modified lithium nickel manganese oxide positive electrode material, forming a modified coating layer on the main body of the lithium nickel manganese oxide positive electrode material to improve the stability of the material and reduce the occurrence of gas generation. The specific steps are as follows:

[0039] S1. Provide MOF materials

[0040] MOF materials can be prepared independently, or specific types of MOF materials can be purchased from the market.

[0041] In some embodiments, the preparation process of the MOF material includes: dissolving a metal salt to obtain a metal salt solution, dissolving an organic ligand to obtain an organic ligand solution, adding the metal salt solution to the organic ligand solution, and reacting at 20°C-30°C for 20h-30h to obtain the desired MOF material. Specifically, the reaction temperature can be room temperature, such as 20°C, 25°C, 30°C, etc., and the reaction time can be 20h, 23h, 25h, 28h, 30h, etc.

[0042] Furthermore, the metal salt solution is obtained by mixing a metal salt and water, and the mass ratio of the metal salt to water is 1:(5-9), such as 1:5, 1:6, 1:7, 1:8, 1:9, etc. The metal salt can be an organic metal salt or an inorganic metal salt. When the metal ion is a zinc ion, the metal salt can be Zn(OAc)22H2O. When the metal salt is Zn(OAc)2 2H2O and the organic ligand is terephthalic acid (H2BDC), the reaction formula is as follows:

[0043] 2Zn(OAc)2 2H2O+2H2BDC→Zn2(BDC)2+4HOAc+2H2O.

[0044] Furthermore, the organic ligand solution is obtained by mixing an organic ligand and an organic solvent, and the mass ratio of the organic ligand to the organic solvent is 1:(20-25), such as 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, etc. The type of organic solvent is not limited, such as N,N-dimethylformamide (DMF), but is not limited thereto.

[0045] Furthermore, by adjusting the amount of metal salt solution and organic ligand solution, the molar ratio of metal ions in the metal salt to organic ligands is (1.5-2.0):1, such as 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, etc.

[0046] Furthermore, the preparation process of the MOF material also includes: solid-liquid separation after the reaction is completed, washing and drying the obtained solid material. The solid-liquid separation method is not limited, and can be suction filtration, washing with DMF, then washing with water for multiple times, and drying overnight.

[0047] S2. Esterification reaction

[0048] The MOF material and the organic acid are mixed and reacted to obtain a reaction solution containing a modified substance. The MOF material contains an OH functional group, which undergoes an esterification reaction with the carboxyl group in the organic acid to form an emulsion.

[0049] In some embodiments, the process of preparing the reaction solution includes: mixing the MOF material, the organic acid and water, and reacting at 20° C.-40° C. for 1 h-5 h. Specifically, the reaction temperature can be 20° C., 30° C., 40° C., etc., and the reaction time can be 1 h, 2 h, 3 h, 4 h, 5 h, etc.

[0050] Furthermore, the mass ratio of MOF material and organic acid is (1-3): 1, the amount of water is not limited, deionized water is added to the solution of MOF and organic acid during the test, and the amount of organic acid is preferably within the above range to further improve the modification effect of the generated modified substance on the nickel manganese oxide lithium positive electrode material, improve the stability of the material and reduce gas production. Specifically, the mass ratio of MOF material and organic acid can be 1: 1, 2: 1, 3: 1, etc.

[0051] S3, wet coating

[0052] The reaction solution is coated on the main body of the lithium nickel manganese oxide positive electrode material by a wet coating method, and then dried to form a stable coating layer.

[0053] Specifically, the wet coating can be performed by using a wet coating machine, and the specific model is not limited. The reaction solution is evenly sprayed onto the surface of the lithium nickel manganese oxide positive electrode material body, and then heated and dried.

[0054] Furthermore, the mass fraction of the modified substance in the reaction solution is 25%-35% (the remaining materials are mainly water), and the volume of the reaction solution corresponding to every 500g of lithium nickel manganese oxide positive electrode material body is 500mL-800mL. By precisely controlling the mass ratio of the lithium nickel manganese oxide positive electrode material body and the modified substance in the reaction solution, the mass proportion of the formed coating layer is further regulated to make the coating amount more appropriate, so as to achieve the purpose of significantly reducing gas production and improving material stability.

[0055] Specifically, the mass fraction of the modified substance in the reaction solution can be 25%, 28%, 30%, 32%, 35%, etc., and the volume of the reaction solution corresponding to every 500g of lithium nickel manganese oxide positive electrode material body can be 500mL, 550mL, 600mL, 650mL, 700mL, 750mL, 800mL, etc.

[0056] Furthermore, the drying temperature is controlled to be 40°C-60°C and the drying time is 10h-15h to remove the solvent and form a uniform and stable coating layer. The drying temperature can be 40°C, 50°C, 60°C, etc. and the drying time can be 10h, 13h, 15h, etc.

[0057] An embodiment of the present invention provides a positive electrode plate, including the modified lithium nickel manganese oxide positive electrode material provided in the embodiment of the present invention, and may also include a positive electrode current collector, on which a positive electrode active coating is formed, and the modified lithium nickel manganese oxide positive electrode material is the main material in the positive electrode active coating.

[0058] An embodiment of the present invention further provides a lithium battery, including the above-mentioned positive electrode plate, and may also include a negative electrode plate, an electrolyte, a separator, etc., to form a complete battery structure.

[0059] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0060] The main reagents used in the synthesis of MOF materials in the following examples and comparative examples are: zinc acetate dihydrate [Zn(OAc)2 2H2O] (purity 98%) and terephthalic acid (H2BDC) as raw materials, deionized water and N,N-dimethylformamide (DMF, purity 98.8%) as solvents, and MOF is directly precipitated at room temperature.

[0061] The lithium nickel manganese oxide positive electrode material used in the following examples and comparative examples has a chemical formula of LNMO (LiNi 0.5 Mn 1.5 O4).

[0062] Example 1

[0063] This embodiment provides a method for preparing a modified lithium nickel manganese oxide positive electrode material, the steps are as follows:

[0064] (1) 0.68 g (4.1 mmol) of H2BDC was dissolved in 14.96 g (0.2 mol) of DMF to obtain an organic ligand solution; 1.56 g (7.1 mmol) of Zn(OAc)2 2H2O was dissolved in 11.04 g (0.61 mol) of water to obtain a zinc salt solution. The zinc salt solution was added dropwise to the organic ligand solution for 15 min. The mixture was stirred continuously for 15 min to form a white precipitate. The suspension was stirred at room temperature (about 25 °C, the same below) for 24 h. The precipitate was then filtered with DMF, washed repeatedly with water, and dried at 80 °C overnight to obtain a MOF material.

[0065] (2) 5 g of the MOF material obtained in step (1) was mixed with 10 g of tricarboxylic acid and 500 g of deionized water, heated to 30° C., magnetically stirred for 2 h, and then repeatedly washed with 45° C. water to obtain a reaction solution (the mass fraction of the modified substance was 30%).

[0066] (3) The reaction solution obtained in step (2) is evenly sprayed on the main body of the lithium nickel manganese oxide positive electrode material using a wet coating machine, and then vacuum dried at 50° C. for 12 hours to obtain MOF-PMA@LNMO. The mass fraction of the modified substance in the reaction solution used is 30% (the remaining materials are mainly water), and the volume of the reaction solution corresponding to each 500g of the lithium nickel manganese oxide positive electrode material main body is 600mL.

[0067] Example 2

[0068] The only difference from Example 1 is that in step (3), the volume of the reaction solution corresponding to every 500 g of the lithium nickel manganese oxide positive electrode material body is 200 mL (coating amount is about 10%).

[0069] Example 3

[0070] The only difference from Example 1 is that in step (3), the volume of the reaction solution corresponding to every 500 g of lithium nickel manganese oxide positive electrode material body is 500 mL.

[0071] Comparative Example 1

[0072] This comparative example provides an unmodified lithium nickel manganese oxide positive electrode material.

[0073] Test Example 1

[0074] The SEM image of the modified lithium nickel manganese oxide positive electrode material prepared in Test Example 1 is as follows: Figure 1 shown.

[0075] It can be seen that a coating layer is formed on the lithium nickel manganese oxide positive electrode material substrate.

[0076] Test Example 2

[0077] The cycle performance of the modified lithium nickel manganese oxide positive electrode material prepared in the test example and the comparative example is shown in Table 1.

[0078] Test method: 32mg / cm2 coating on both sides of the positive electrode 2 , compaction 3.1g / cm 3 , negative electrode double-sided coating 16mg / cm 2 , compaction 1.55g / cm 3 , PE diaphragm, using blue electricity test 0.33C charged to 4.9V, then constant voltage charging, cut-off current 0.05, electrolyte (LiPF6, 1,2-dimethoxypropane, ethylene glycol dimethyl ether) 10g.

[0079] Table 1 Cyclic performance of modified lithium nickel manganese oxide positive electrode materials prepared in Examples and Comparative Examples

[0080]

[0081]

[0082] It can be seen from Table 1 that the modified lithium nickel manganese oxide positive electrode material prepared in the embodiment of the present invention has significantly better cycle performance than that of the comparative example.

[0083] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A modified lithium nickel manganese oxide positive electrode material, characterized in that: It comprises a lithium nickel manganese oxide positive electrode material body and a modified coating layer coated on the lithium nickel manganese oxide positive electrode material body; Wherein, the modified substance contained in the modified coating layer is obtained by esterification reaction of MOF material and organic acid.

2. The modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The metal ion used to prepare the MOF material is selected from at least one of zinc ion, aluminum ion, iron ion and copper ion, preferably zinc ion; And / or, the organic ligand for preparing the MOF material is selected from at least one of 1,4-benzenedicarboxylic acid and terephthalic acid; and / or, the organic acid is selected from at least one of triformic acid and acetic acid, preferably triformic acid; And / or, when preparing the modified substance, the mass ratio of the MOF material to the organic acid is controlled to be (1-3):

1.

3. The modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The mass ratio of the modified coating layer to the lithium nickel manganese oxide positive electrode material body is (1-5):

100.

4. A method for preparing the modified lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 3, characterized in that: include: The modified coating layer is formed on the lithium nickel manganese oxide positive electrode material body.

5. The preparation method according to claim 4, characterized in that: The MOF material and the organic acid are mixed and reacted to obtain a reaction solution containing a modified substance, and the reaction solution is coated on the lithium nickel manganese oxide positive electrode material body by a wet coating method, and then dried.

6. The preparation method according to claim 5, characterized in that: The mass fraction of the modified substance in the reaction solution is 25%-35%, and the volume of the reaction solution corresponding to every 500g of the lithium nickel manganese oxide positive electrode material body is 500mL-800mL; And / or, the drying temperature is controlled to be 40°C-60°C and the drying time is controlled to be 10h-15h.

7. The preparation method according to claim 5, characterized in that: The process of preparing the reaction solution includes: mixing the MOF material, the organic acid and water, reacting at 20° C.-40° C. for 1 h-5 h, and then washing; Preferably, the mass ratio of the MOF material to the organic acid is (1-3):

1.

8. The preparation method according to claim 5, characterized in that: The preparation process of the MOF material comprises: dissolving a metal salt to obtain a metal salt solution, dissolving an organic ligand to obtain an organic ligand solution, adding the metal salt solution to the organic ligand solution, and reacting at 20° C. to 30° C. for 20 h to 30 h; Preferably, the molar ratio of the metal ion in the metal salt to the organic ligand is (1.5-2.0):1; Preferably, the metal salt solution is obtained by mixing a metal salt and water, and the mass ratio of the metal salt to water is 1:(5-9); Preferably, the organic ligand solution is obtained by mixing the organic ligand and an organic solvent, and the mass ratio of the organic ligand to the organic solvent is 1:(20-25); Preferably, the preparation process of the MOF material further comprises: solid-liquid separation after the reaction is completed, and washing and drying the obtained solid material.

9. A positive electrode sheet, characterized in that: It comprises the modified lithium nickel manganese oxide positive electrode material as described in any one of claims 1 to 3 or the modified lithium nickel manganese oxide positive electrode material prepared by the preparation method as described in any one of claims 4 to 8.

10. A lithium battery, characterized in that: Including the positive electrode sheet as described in claim 9.

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