A positive electrode material, a preparation method and application thereof

Abstract

The disclosure discloses a positive electrode material, which comprises a core and a coating layer, the coating layer is wrapped on the core, the core comprises a lithium nickel cobalt manganese oxide material, and the coating layer comprises a MOFs material and a V2O5 / rGO material.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of positive electrode materials, and particularly relates to a positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Commercialized positive electrode materials of lithium ion batteries mainly include lithium cobaltate, lithium manganate, lithium iron phosphate and lithium nickel cobalt manganate, etc. The lithium cobaltate has a high cost, and has a safety hazard when overcharged. The layered lithium manganate has poor structural stability, and the specific capacity of the spinel lithium manganate is low, and the structural stability at high temperature needs to be improved. The lithium iron phosphate has poor processing performance, low tap density and low energy density. In comparison, the lithium nickel cobalt manganate material has the advantages of low cost, good high-temperature performance, high energy density and excellent processing performance, and is thus widely used. However, it is found that the high-rate performance and cycle stability of the lithium nickel cobalt manganate material are poorer than those of the lithium cobaltate. Therefore, it is urgent to improve the electrochemical performance of the existing lithium cobalt manganate material to meet the increasingly high technical requirements of lithium ion batteries. SUMMARY

[0003] The present disclosure aims to at least solve one of the technical problems existing in the related art. To this end, the present disclosure provides a positive electrode material and a preparation method and application thereof, which has good high-rate performance and cycle stability and can meet the increasingly high technical requirements of existing lithium ion batteries.

[0004] The above technical purpose of the present disclosure is achieved by the following technical solutions:

[0005] A positive electrode material, comprising a core and a coating layer, wherein the coating layer is wrapped on the core, the core comprises a lithium nickel cobalt manganate material, and the coating layer comprises a MOFs material and a V2O5 / rGO material.

[0006] In an embodiment, the molecular formula of the lithium nickel cobalt manganate material is LiNi x Co y Mn 1-x-y O2, 1 > x > 0.8, y > 0 and 1-x-y > 0.

[0007] In an embodiment, the mass ratio of the core to the coating layer is 1: (0.15-0.25).

[0008] In an embodiment, the mass ratio of the V2O5 / rGO material to the MOFs material in the coating layer is 1: (0.01-0.1).

[0009] A preparation method of the positive electrode material, comprising the following steps:

[0010] (1) Vanadium source, acid and surfactant are dissolved in water, rGO is added, and the reaction is carried out under stirring at elevated temperature, then the product is washed, dried, sintered, and cooled to obtain V2O5 / rGO material. The surfactant can form micellar structure in water, form certain interfacial tension, and wrap vanadium source, acid and rGO, so that they are more uniformly mixed in water. At the same time, the surfactant can promote the reaction and accelerate the generation of V2O5, so that the reaction is more complete, and the uniformity of V2O5 and rGO is improved.

[0011] (2) The V2O5 / rGO material prepared in step (1) is soaked in a MOFs generating solution, taken out, and heated to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby obtaining a wrapping layer material.

[0012] (3) The wrapping layer material prepared in step (2) is mixed with lithium nickel cobalt manganese oxide and heated to obtain the positive electrode material.

[0013] In an embodiment, in step (1), the vanadium source is at least one of ammonium vanadate, vanadium acetylacetone and vanadium acetylacetone oxide.

[0014] In an embodiment, in step (1), the acid is at least one of oxalic acid and citric acid.

[0015] In an embodiment, in step (1), the surfactant is at least one of hexamethyl tetramine and dodecyl alcohol amide.

[0016] In an embodiment, in step (1), the molar ratio of vanadium source, acid and surfactant is 1:1:(0.1-0.5).

[0017] In an embodiment, in step (1), the mass of rGO added is 1.5-3 times the mass of vanadium source.

[0018] In an embodiment, in step (1), the stirring speed under stirring is 600-1000 r / min.

[0019] In an embodiment, in step (1), the temperature of the elevated temperature reaction is 300-350℃, and the reaction time is 10-20h.

[0020] In an embodiment, in step (1), the sintering is carried out at a rate of 15-20℃ / min to 600-800℃, and the sintering time is 3-5h.

[0021] In an embodiment, the MOFs generating solution in step (2) is prepared by dissolving Cr(NO3)3 and sodium benzoate in methanol according to a molar ratio of (3-7):(2-5), and the ratio of Cr(NO3)3 to methanol is 5 g:(50-100) ml. The reaction mechanism is as follows: sodium benzoate is partially protonated in methanol to produce benzoic acid and sodium ions, Cr(NO3)3 is dissolved in methanol to release Cr 3+ ions and NO 3- ions, Cr 3+ ions and benzoic acid to form a coordination reaction to form a Cr-benzoic acid complex, and the Cr-benzoic acid complex forms a crystal nucleus and gradually grows to form MOFs.

[0022] In an embodiment, in step (2), the soaking time is 6-12 h.

[0023] In an embodiment, in step (2), the heating temperature is 130-160 °C, and the heating time is 12-24 h.

[0024] In an embodiment, in step (3), the heating temperature is 100-200 °C, and the heating time is 2-12 h.

[0025] A lithium ion battery comprising the positive electrode material as described above.

[0026] The positive electrode material of the present disclosure has a wrapping layer formed by mixing MOFs material and V2O5 / rGO material. The MOFs material has the advantages of high porosity, low density, large specific surface area, regular pore channel, adjustable pore size, and diversity and tailorability of topological structure. By modifying the V2O5 / rGO material with the MOFs material, the specific surface area of the V2O5 / rGO material is expanded, the spatial structure is improved, and the lithium ion insertion / extraction is promoted. At the same time, since the MOFs material is loaded on the surface and inside of the V2O5 / rGO material, the conductivity and stability of the MOFs material are promoted, so that the surface coating layer of the positive electrode material of the present disclosure can avoid direct contact between the ternary nickel-cobalt-manganese lithium material as the core and the electrolyte, reduce the occurrence of side reactions, and at the same time, the surface coating layer significantly improves the high-rate performance and cycle stability of the ternary nickel-cobalt-manganese lithium material. DETAILED DESCRIPTION

[0027] The present disclosure will be further described below in conjunction with specific embodiments.

[0028] Embodiment 1:

[0029] A positive electrode material, comprising a core and a coating layer, the coating layer being wrapped on the core, the core being a lithium nickel cobalt manganese oxide material, the coating layer being formed by mixing a MOFs material and a V2O5 / rGO material, the molecular formula of the lithium nickel cobalt manganese oxide material being LiNi 0.8 Co 0.1 Mn 0.1 O2, the mass ratio of the core to the coating layer being 1:0.15, and the mass ratio of the V2O5 / rGO material to the MOFs material in the coating layer being 1:0.01.

[0030] The preparation method of the positive electrode material comprises the following steps:

[0031] (1) ammonium vanadate, oxalic acid and hexamethylenetetramine are dissolved in water in a molar ratio of 1:1:0.1, rGO is added, the mass of the added rGO being 1.5 times the mass of the ammonium vanadate, stirring is performed at a speed of 600 r / min, the precipitate is washed with water after the temperature is raised to 300 DEG C under the stirring state and reacted for 20 h, drying is performed, the temperature is raised to 600 DEG C at a rate of 15 DEG C / min, sintering is performed for 3 h, and cooling is performed, to obtain the V2O5 / rGO material;

[0032] (2) Cr(NO3)3 and sodium benzoate are dissolved in methanol in a molar ratio of 3:2 to prepare a MOFs generating solution, the ratio of Cr(NO3)3 to methanol is 5 g:50 ml, the V2O5 / rGO material prepared in step (1) is soaked in the MOFs generating solution for 6 h, and the V2O5 / rGO material is heated at a temperature of 130 DEG C for 24 h to generate MOFs material on the surface and inside of the V2O5 / rGO material, to obtain the coating layer material;

[0033] (3) the coating layer material prepared in step (2) is mixed with the lithium nickel cobalt manganese oxide material with the molecular formula LiNi 0.8 Co 0.1 Mn 0.1 O2, and heating is performed at a temperature of 100 DEG C for 12 h, to obtain the positive electrode material.

[0034] Example 2:

[0035] A positive electrode material, comprising a core and a coating layer, the coating layer being wrapped on the core, the core being a lithium nickel cobalt manganese oxide material, the coating layer being formed by mixing a MOFs material and a V2O5 / rGO material, the molecular formula of the lithium nickel cobalt manganese oxide material being LiNi 0.9 Co 0.05 Mn 0.05 O2, the mass ratio of the core to the coating layer being 1:0.25, and the mass ratio of the V2O5 / rGO material to the MOFs material in the coating layer being 1:0.1.

[0036] The preparation method of the positive electrode material comprises the following steps:

[0037] (1) ammonium vanadate, oxalic acid and hexamethylenetetramine are dissolved in water in a molar ratio of 1:1:0.5, rGO is added, the mass of the added rGO is 3 times the mass of the ammonium vanadate, stirring is performed at a speed of 1000 r / min, the temperature is increased to 350°C under the stirring state, and reaction is performed for 10 h, the precipitate is washed with water, drying is performed, the temperature is increased to 800°C at a rate of 20°C / min, sintering is performed for 5 h, cooling is performed, and a V2O5 / rGO material is obtained;

[0038] (2) Cr(NO3)3 and sodium benzoate are dissolved in methanol in a molar ratio of 7:5 to prepare a MOFs generating solution, the ratio of Cr(NO3)3 to methanol is 5 g:100 ml, the V2O5 / rGO material prepared in step (1) is placed in the MOFs generating solution and soaked for 12 h, and the V2O5 / rGO material is heated at a temperature of 160°C for 12 h to generate MOFs material on the surface and inside of the V2O5 / rGO material, and a wrapping layer material is prepared;

[0039] (3) the wrapping layer material prepared in step (2) is mixed with lithium nickel cobalt manganese oxide with a molecular formula of LiNi 0.9 Co 0.05 Mn 0.05 O2, and heating is performed at a temperature of 200°C for 2 h to obtain the positive electrode material.

[0040] Example 3:

[0041] A positive electrode material includes a core and a wrapping layer, the wrapping layer is wrapped on the core, the core is lithium nickel cobalt manganese oxide material, the wrapping layer is mixed from MOFs material and V2O5 / rGO material, the molecular formula of the lithium nickel cobalt manganese oxide material is LiNi 0.9 Co 0.05 Mn 0.05 O2, the mass ratio of the core to the wrapping layer is 1:0.2, and the mass ratio of the V2O5 / rGO material to the MOFs material in the wrapping layer is 1:0.05.

[0042] The preparation method of the positive electrode material includes the following steps:

[0043] (1) ammonium vanadate, oxalic acid and hexamethylenetetramine are dissolved in water in a molar ratio of 1:1:0.4, rGO is added, the mass of the added rGO is 2 times the mass of the ammonium vanadate, stirring is performed at a speed of 800 r / min, the temperature is increased to 320°C under the stirring state, and reaction is performed for 15 h, the precipitate is washed with water, drying is performed, the temperature is increased to 700°C at a rate of 18°C / min, sintering is performed for 4 h, cooling is performed, and a V2O5 / rGO material is obtained;

[0044] (2) Dissolve Cr(NO3)3 and sodium benzoate in methanol at a molar ratio of 5:4 to prepare MOFs generating solution. The ratio of Cr(NO3)3 to methanol is 5g:80ml. Soak the V2O5 / rGO material obtained in step (1) in the MOFs generating solution for 10h. Take it out and heat it at 150℃ for 20h to generate MOFs material on the surface and inside of the V2O5 / rGO material to obtain the coating material.

[0045] (3) The coating material obtained in step (2) is combined with the molecular formula LiNi 0.9 Co 0.05 Mn 0.05 The cathode material is obtained by mixing lithium nickel cobalt manganese oxide with O2 and heating it at 150°C for 8 hours.

[0046] Example 4:

[0047] A cathode material includes a core and a coating layer, wherein the coating layer is coated on the core. The core is lithium nickel cobalt manganese oxide, and the coating layer is a mixture of MOF (Metal-O-Factory Materials) and V2O5 / rGO materials. The molecular formula of the lithium nickel cobalt manganese oxide material is LiNi. 0.9 Co 0.05 Mn 0.05 The mass ratio of O2 core to encapsulation layer is 1:0.18, and the mass ratio of V2O5 / rGO material to MOFs material in the encapsulation layer is 1:0.06.

[0048] The preparation method of the above-mentioned positive electrode material includes the following steps:

[0049] (1) Vanadium acetylacetonate, citric acid and dodecyl alcohol amide were dissolved in water in a molar ratio of 1:1:0.3. rGO was added, and the mass of rGO added was 1.6 times that of vanadium acetylacetonate. The mixture was stirred at 800 r / min and heated to 320 °C for 15 h under stirring. The precipitate was washed with water, dried, heated to 700 °C at a rate of 18 °C / min, sintered for 4 h, and cooled to obtain V2O5 / rGO material.

[0050] (2) Dissolve Cr(NO3)3 and sodium benzoate in methanol at a molar ratio of 5:3 to prepare MOFs generating solution. The ratio of Cr(NO3)3 to methanol is 5g:80ml. Soak the V2O5 / rGO material obtained in step (1) in the MOFs generating solution for 10h, take it out, and heat it at 150℃ for 20h to generate MOFs material on the surface and inside of the V2O5 / rGO material to obtain the coating material.

[0051] (3) The coating material obtained in step (2) is combined with the molecular formula LiNi 0.9 Co 0.05 Mn 0.05The nickel cobalt lithium manganate of O2 is mixed, heated at a temperature of 150℃ for 8h, and the positive electrode material is obtained.

[0052] Example 5:

[0053] A positive electrode material comprises a core and a coating layer, the coating layer is wrapped on the core, the core is a nickel cobalt lithium manganate material, the coating layer is mixed by a MOFs material and a V2O5 / rGO material, the molecular formula of the nickel cobalt lithium manganate material is LiNi 0.9 Co 0.05 Mn 0.05 O2, the mass ratio of the core to the coating layer is 1:0.16, and the mass ratio of the V2O5 / rGO material to the MOFs material in the coating layer is 1:0.03.

[0054] The preparation method of the positive electrode material comprises the following steps:

[0055] (1) Vanadium acetylacetonate, citric acid and hexamethylenetetramine are dissolved in water in a molar ratio of 1:1:0.2, rGO is added, the mass of the added rGO is 1.8 times the mass of the vanadium acetylacetonate, stirring is performed at a speed of 800r / min, the stirring state is heated to 320℃ for 15h, the precipitate is washed with water, dried, heated to 700℃ at a rate of 18℃ / min, sintered for 4h, and cooled to obtain the V2O5 / rGO material;

[0056] (2) Cr(NO3)3 and sodium benzoate are dissolved in methanol in a molar ratio of 5:3 to prepare a MOFs generating solution, the ratio of Cr(NO3)3 to methanol is 5g:80ml, the V2O5 / rGO material prepared in step (1) is soaked in the MOFs generating solution for 10h, taken out, heated at a temperature of 150℃ for 20h, so that the MOFs material is generated on the surface and inside of the V2O5 / rGO material, and the coating layer material is prepared;

[0057] (3) The coating layer material prepared in step (2) is mixed with the nickel cobalt lithium manganate of O2 of the molecular formula LiNi 0.9 Co 0.05 Mn 0.05 O2, heated at a temperature of 150℃ for 8h, and the positive electrode material is obtained.

[0058] Comparative Example 1: (compared with Example 3, the only difference is that the coating layer does not contain the MOFs material)

[0059] A positive electrode material comprises a core and a coating layer, the coating layer is wrapped on the core, the core is a nickel cobalt lithium manganate material, the coating layer is a V2O5 / rGO material, the molecular formula of the nickel cobalt lithium manganate material is LiNi 0.9 Co 0.05 Mn 0.05O2, the mass ratio of the core and the coating layer is 1:0.2, and the mass ratio of the V2O5 / rGO material and the MOFs material in the coating layer is 1:0.05.

[0060] The preparation method of the positive electrode material comprises the following steps:

[0061] (1) Ammonium vanadate, oxalic acid and hexamethylenetetramine are dissolved in water in a molar ratio of 1:1:0.4, rGO is added, the mass of the added rGO is 2 times the mass of the ammonium vanadate, stirring is performed at a speed of 800 r / min, the temperature is increased to 320℃ under stirring for 15 h, the precipitate is washed with water, dried, and the temperature is increased to 700℃ at a rate of 18℃ / min, sintering is performed for 4 h, and cooling is performed to obtain a V2O5 / rGO material;

[0062] (2) The V2O5 / rGO material prepared in step (1) is mixed with lithium nickel cobalt manganese oxide with a molecular formula of LiNi 0.9 Co 0.05 Mn 0.05 O2, and heating is performed at a temperature of 150℃ for 8 h to obtain the positive electrode material.

[0063] Comparative Example 2:

[0064] 1 kg of the ternary positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 O2 is weighed, is placed in an airflow crusher for crushing, and the particle size D50 of the obtained ternary positive electrode material is 5 μm, which is used as the positive electrode material.

[0065] Test Example:

[0066] The positive electrode materials of Examples 1-5 and Comparative Examples 1-2 are respectively used as lithium ion battery positive electrode materials, are mixed in a mass ratio of positive electrode material: acetylene black: polyvinylidene fluoride = 96:5:5, are slurried, are uniformly coated on an aluminum foil to obtain positive electrode sheets. Lithium sheets are used as negative electrode sheets, are assembled into CR2430 button-shaped half-batteries in an inert gas glove box, and performance tests are performed on the batteries, and the test results are shown in Table 1.

[0067] Table 1: Battery performance test results:

[0068]

[0069] As can be seen from Table 1, the lithium battery made of the positive electrode material of the present disclosure has a 0.1C gram capacity of 199.56 mAh / g or more, a rate performance of 90.39% or more at 0.5C / 0.1C, a rate performance of 82.28% or more at 1C / 0.1C, a rate performance of 70.11% or more at 2C / 0.1C, and a capacity retention rate of 90.23% or more after 100 cycles.

[0070] In addition, as can be seen from the comparison between Comparative Example 3 and Comparative Example 1, when the MOFs material is not contained in the wrapping layer, the rate performance and the capacity retention rate after 100 cycles of the finally prepared battery are both greatly reduced. As can be seen from the comparison between Comparative Example 3 and Comparative Example 2, the lithium battery made of the positive electrode material of the present disclosure has more excellent high-rate performance and cycle stability than the lithium battery made of the single ternary lithium cobalt manganese oxide material.

Claims

1. A method for preparing a positive electrode material, characterized by: The preparation method comprises the following steps: (1) dissolving a vanadium source, an acid and a surfactant in water, adding rGO, and then reacting under stirring at an elevated temperature, washing, drying, sintering, cooling, and obtaining a V2O5 / rGO material; (2) immersing the V2O5 / rGO material prepared in step (1) in a MOFs generating solution, taking out, and heating to form a MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating material; (3) mixing the coating material prepared in step (2) with lithium nickel cobalt manganese oxide, and heating to obtain the positive electrode material; the positive electrode material comprises a core and a coating, the coating is wrapped on the core, the core comprises lithium nickel cobalt manganese oxide material, and the coating comprises a MOFs material and a V2O5 / rGO material; the MOFs generating solution in step (2) is prepared by dissolving Cr(NO3)3 and sodium benzoate in methanol according to a molar ratio of (3-7):(2-5), and the ratio of Cr(NO3)3 to methanol is 5 g:(50-100) ml.

2. The method of claim 1, wherein the method further comprises: In step (1), the vanadium source is at least one of ammonium vanadate, vanadium acetylacetonate and vanadyl acetylacetonate.

3. The method for preparing a positive electrode material according to claim 1, characterized in that: In step (1), the acid is at least one of oxalic acid and citric acid.

4. The method of claim 1, wherein the method further comprises: In step (1), the surfactant is at least one of hexamethylenetetramine and dodecyl alcohol amide.

5. The method of claim 1, wherein the method further comprises: In step (1), the molar ratio of the vanadium source, the acid and the surfactant is 1:1:(0.1-0.5).

6. The method for preparing a positive electrode material according to claim 1, characterized in that: In step (1), the mass of rGO added is 1.5-3 times the mass of the vanadium source.

7. The method for preparing a positive electrode material according to claim 1, characterized in that: In step (1), the stirring speed under stirring is 600-1000 r / min.

8. The method of claim 1, wherein the method further comprises: In step (1), the temperature of the elevated temperature reaction is 300-350°C, and the reaction time is 10-20 h.

9. The method of claim 1, wherein the method further comprises: In step (1), the sintering is performed at a rate of 15-20°C / min to 600-800°C, and the sintering time is 3-5 h.

10. The method of claim 1, wherein the method further comprises: In step (2), the immersion time is 6-12 h.

11. The method of claim 1, wherein the method further comprises: In step (2), the heating temperature is 130-160°C, and the heating time is 12-24 h.

12. The method of claim 1, wherein: In step (3), the heating temperature is 100-200°C, and the heating time is 2-12 h.

13. A positive electrode material, characterized by: The positive electrode material is prepared by the preparation method of any one of claims 1-12.

14. The positive electrode material of claim 13, wherein: The molecular formula of the lithium nickel cobalt manganese oxide material is LiNi x Co y Mn 1-x-y O2, 1 > x ≥ 0.8, y ≥ 0 and 1-x-y > 0.

15. The positive electrode material of claim 13, wherein: The mass ratio of the core to the coating is 1:(0.15-0.25).

16. The positive electrode material of claim 13, wherein: The mass ratio of the V2O5 / rGO material to the MOFs material in the coating is 1:(0.01-0.1).

17. A lithium-ion battery, characterized by, The positive electrode material comprises the positive electrode material of any one of claims 13-16.

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