Positive electrode material, preparation method therefor and use thereof

Abstract

Disclosed in the present disclosure is a positive electrode material. The positive electrode material comprises a core and a wrapping layer. The wrapping layer wraps the core. The core comprises a lithium nickel manganese cobalt oxide material, and the wrapping layer comprises an MOFs material and a V2O5 / rGO material.

Description

A positive electrode material and its preparation method and application Technical Field

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

[0002] The main commercial cathode materials for lithium-ion batteries include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and nickel cobalt manganese oxide. Among them, lithium cobalt oxide is relatively expensive and poses a safety hazard when overcharged; layered lithium manganese oxide has poor structural stability, spinel-type lithium manganese oxide has a low specific capacity, and its structural stability at high temperatures needs to be improved. Lithium iron phosphate has poor processing performance, low tap density, and low energy density. In contrast, nickel cobalt manganese oxide has the advantages of low cost, good high-temperature performance, high energy density, and excellent processing performance, and is therefore widely used. However, during use, it was found that the high-rate performance and cycle stability of nickel cobalt manganese oxide materials were inferior to those of lithium cobalt oxide. Therefore, there is an urgent need to improve the electrochemical properties of existing lithium cobalt manganese oxide materials to meet the increasingly high technical requirements of lithium-ion batteries.

[0003] Summary of the Invention

[0004] The present disclosure aims to solve at least one of the technical problems existing in the related art. To this end, the present disclosure provides a positive electrode material, a preparation method, and an application thereof, which has good high-rate performance and cycle stability, and can meet the increasingly demanding technical requirements of existing lithium-ion batteries.

[0005] The above technical objectives of the present disclosure are achieved through the following technical solutions:

[0006] A positive electrode material comprises a core and a wrapping layer, wherein the wrapping layer is wrapped around the core, the core comprises a lithium nickel cobalt manganese oxide material, and the wrapping layer comprises a MOFs material and a V2O5 / rGO material.

[0007] In one embodiment, 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-xy>0.

[0008] In one embodiment, the mass ratio of the core to the wrapping layer is 1:(0.15-0.25).

[0009] In one embodiment, the mass ratio of the V2O5 / rGO material to the MOFs material in the encapsulating layer is 1:(0.01-0.1).

[0010] A method for preparing the positive electrode material as described above comprises the following steps:

[0011] (1) Dissolving the vanadium source, acid and surfactant in water, adding rGO, heating the reaction under stirring, washing, drying, sintering and cooling to obtain V2O5 / rGO material. The surfactant can form a micellar structure in water, forming a certain interfacial tension, which can wrap the vanadium source, acid and rGO, so that they are more evenly mixed in water. At the same time, when the temperature is increased, the reaction can be promoted, the generation of V2O5 can be accelerated, the reaction can be more complete, and the uneven precipitation of V2O5 and rGO can be prevented, so that V2O5 and rGO can be mixed more evenly.

[0012] (2) placing the V2O5 / rGO material obtained in step (1) into a MOFs generation solution for immersion, taking it out, and heating it to generate MOFs material on the surface and inside of the V2O5 / rGO material to obtain a coating layer material;

[0013] (3) The coating layer material obtained in step (2) is mixed with lithium nickel cobalt manganese oxide and heated to obtain the positive electrode material.

[0014] In one embodiment, in step (1), the vanadium source is at least one of ammonium vanadate, vanadium acetylacetonate, and vanadyl acetylacetonate.

[0015] In one embodiment, in step (1), the acid is at least one of oxalic acid and citric acid.

[0016] In one embodiment, in step (1), the surfactant is at least one of hexamethylenetetramine and dodecyl alcohol amide.

[0017] In one embodiment, in step (1), the molar ratio of the vanadium source, the acid, and the surfactant is 1:1:(0.1-0.5).

[0018] In one embodiment, in step (1), the mass of rGO added is 1.5-3 times the mass of the vanadium source.

[0019] In one embodiment, in step (1), the stirring speed in the stirring state is 600-1000 r / min.

[0020] In one embodiment, in step (1), the temperature of the temperature-raising reaction is 300-350° C., and the reaction time is 10-20 h.

[0021] In one embodiment, in step (1), the sintering is performed by heating the temperature to 600-800° C. at a rate of 15-20° C. / min and sintering for 3-5 hours.

[0022] In one embodiment, the MOFs generating solution in step (2) is prepared by dissolving Cr(NO3)3 and sodium benzoate in methanol in a molar ratio of (3-7): (2-5), and the ratio of Cr(NO3)3 to methanol is 5g: (50-100)ml. The reaction mechanism is as follows: sodium benzoate is partially protonated in methanol to produce benzoic acid and sodium ions, and Cr(NO3)3 dissolves in methanol to release Cr 3+ ions and NO 3- ions, Cr 3+ The ions react with benzoic acid to form a Cr-benzoic acid complex, which forms a crystal nucleus and gradually grows to form MOFs.

[0023] In one embodiment, in step (2), the soaking time is 6-12 hours.

[0024] In one embodiment, in step (2), the heating temperature is 130-160° C., and the heating time is 12-24 hours.

[0025] In one embodiment, in step (3), the heating temperature is 100-200° C., and the heating time is 2-12 hours.

[0026] A lithium-ion battery comprises the positive electrode material described above.

[0027] The beneficial effects of the present disclosure are as follows: the coating layer of the positive electrode material of the present disclosure is formed by a mixture of MOFs material and V2O5 / rGO material. The MOFs material has the advantages of high porosity, low density, large specific surface area, regular pores, adjustable pore size, topological structure diversity and tailorability. The V2O5 / rGO material is modified by the MOFs material to expand the specific surface area of ​​the V2O5 / rGO material, improve its spatial structure, and promote the insertion / extraction of lithium ions. 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 oxide material as the core and the electrolyte, reducing the occurrence of side reactions. At the same time, the surface coating layer significantly improves the high rate performance and cycle stability of the ternary nickel cobalt manganese oxide material. DETAILED DESCRIPTION

[0028] The present disclosure is further described below with reference to specific embodiments.

[0029] Example 1:

[0030] A positive electrode material includes a core and a coating layer, wherein the coating layer is coated on the core, the core is a lithium nickel cobalt manganese oxide material, and the coating layer is a mixture of MOFs material and V2O5 / rGO material. The molecular formula of the lithium nickel cobalt manganese oxide material is LiNi 0.8 Co 0.1 Mn 0.1 O2, the mass ratio of the core to the coating is 1:0.15, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.01.

[0031] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0032] (1) Ammonium vanadate, oxalic acid and hexamethylenetetramine were dissolved in water at a molar ratio of 1:1:0.1, rGO was added, and the mass of the added rGO was 1.5 times the mass of the ammonium vanadate. The mixture was stirred at a speed of 600 r / min, heated to 300°C under stirring and reacted for 20 h. The precipitate was washed with water, dried, and heated to 600°C at a rate of 15°C / min. The mixture was sintered for 3 h and cooled to obtain V2O5 / rGO material.

[0033] (2) Cr(NO3)3 and sodium benzoate were dissolved in methanol in a molar ratio of 3:2 to prepare a MOFs generation solution, where the ratio of Cr(NO3)3 to methanol was 5g:50ml. The V2O5 / rGO material prepared in step (1) was placed in the MOFs generation solution and soaked for 6 hours. The material was taken out and heated at 130°C for 24 hours to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating layer material.

[0034] (3) The coating material prepared in step (2) is mixed with the LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 100°C for 12 hours.

[0035] Example 2:

[0036] A positive electrode material includes a core and a coating layer, wherein the coating layer is coated on the core, the core is a lithium nickel cobalt manganese oxide material, and the coating layer is a mixture of 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 coating is 1:0.25, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.1.

[0037] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0038] (1) Ammonium vanadate, oxalic acid and hexamethylenetetramine were dissolved in water at a molar ratio of 1:1:0.5, rGO was added, and the mass of the added rGO was 3 times the mass of the ammonium vanadate. The mixture was stirred at a speed of 1000 r / min, heated to 350°C under stirring, and reacted for 10 hours. The precipitate was washed with water, dried, and heated to 800°C at a rate of 20°C / min. The mixture was sintered for 5 hours and cooled to obtain V2O5 / rGO material.

[0039] (2) Cr(NO3)3 and sodium benzoate were dissolved in methanol at a molar ratio of 7:5 to prepare a MOFs generation solution, where the ratio of Cr(NO3)3 to methanol was 5g:100ml. The V2O5 / rGO material prepared in step (1) was placed in the MOFs generation solution and soaked for 12 hours. The material was taken out and heated at 160°C for 12 hours to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating material.

[0040] (3) The coating material prepared in step (2) is mixed with the LiNi 0.9 Co 0.05 Mn 0.05 The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 200°C for 2h.

[0041] Example 3:

[0042] A positive electrode material includes a core and a coating layer, wherein the coating layer is coated on the core, the core is a lithium nickel cobalt manganese oxide material, and the coating layer is a mixture of 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 coating is 1:0.2, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.05.

[0043] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0044] (1) Ammonium vanadate, oxalic acid and hexamethylenetetramine were dissolved in water at a molar ratio of 1:1:0.4, rGO was added, and the mass of the added rGO was twice the mass of the ammonium vanadate. The mixture was stirred at a speed of 800 r / min, heated to 320°C under stirring, and reacted for 15 h. The precipitate was washed with water, dried, and heated to 700°C at a rate of 18°C / min. The mixture was sintered for 4 h and cooled to obtain V2O5 / rGO material.

[0045] (2) Cr(NO3)3 and sodium benzoate were dissolved in methanol at a molar ratio of 5:4 to prepare a MOFs generation solution, where the ratio of Cr(NO3)3 to methanol was 5g:80ml. The V2O5 / rGO material prepared in step (1) was placed in the MOFs generation solution and soaked for 10 hours. The material was taken out and heated at 150°C for 20 hours to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating material.

[0046] (3) The coating material prepared in step (2) is mixed with the LiNi 0.9 Co 0.05 Mn 0.05 The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 150°C for 8 hours.

[0047] Example 4:

[0048] A positive electrode material includes a core and a coating layer, wherein the coating layer is coated on the core, the core is a lithium nickel cobalt manganese oxide material, and the coating layer is a mixture of 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 coating is 1:0.18, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.06.

[0049] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0050] (1) Vanadyl acetylacetonate, citric acid and dodecyl alcohol amide were dissolved in water at a molar ratio of 1:1:0.3, rGO was added, and the mass of the added rGO was 1.6 times the mass of the vanadyl acetylacetonate. The mixture was stirred at a speed of 800 r / min, heated to 320°C under stirring, and reacted for 15 hours. The precipitate was washed with water, dried, and heated to 700°C at a rate of 18°C / min. It was sintered for 4 hours and cooled to obtain V2O5 / rGO material.

[0051] (2) Cr(NO3)3 and sodium benzoate were dissolved in methanol at a molar ratio of 5:3 to prepare a MOFs generation solution, where the ratio of Cr(NO3)3 to methanol was 5g:80ml. The V2O5 / rGO material prepared in step (1) was placed in the MOFs generation solution and soaked for 10 hours. The material was taken out and heated at 150°C for 20 hours to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating material.

[0052] (3) The coating material prepared in step (2) is mixed with the LiNi 0.9 Co 0.05 Mn 0.05The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 150°C for 8 hours.

[0053] Example 5:

[0054] A positive electrode material includes a core and a coating layer, wherein the coating layer is coated on the core, the core is a lithium nickel cobalt manganese oxide material, and the coating layer is a mixture of 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 coating is 1:0.16, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.03.

[0055] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0056] (1) Vanadium acetylacetonate, citric acid and hexamethylenetetramine were dissolved in water at a molar ratio of 1:1:0.2, rGO was added, and the mass of the added rGO was 1.8 times the mass of the vanadium acetylacetonate. The mixture was stirred at a speed of 800 r / min, heated to 320°C under stirring, and reacted for 15 hours. The precipitate was washed with water, dried, and heated to 700°C at a rate of 18°C / min. It was sintered for 4 hours and cooled to obtain V2O5 / rGO material.

[0057] (2) Cr(NO3)3 and sodium benzoate were dissolved in methanol at a molar ratio of 5:3 to prepare a MOFs generation solution, where the ratio of Cr(NO3)3 to methanol was 5g:80ml. The V2O5 / rGO material prepared in step (1) was placed in the MOFs generation solution and soaked for 10 hours. The material was taken out and heated at 150°C for 20 hours to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby preparing a coating material.

[0058] (3) The coating material prepared in step (2) is mixed with the LiNi 0.9 Co 0.05 Mn 0.05 The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 150°C for 8 hours.

[0059] Comparative Example 1: (Compared with Example 3, the only difference is that the wrapping layer does not contain MOFs material)

[0060] A positive electrode material includes a core and a wrapping layer, wherein the wrapping layer is wrapped on the core, the core is a lithium nickel cobalt manganese oxide material, the wrapping layer is a V2O5 / rGO material, and the molecular formula of the lithium nickel cobalt manganese oxide material is LiNi 0.9 Co 0.05 Mn 0.05O2, the mass ratio of the core to the coating is 1:0.2, and the mass ratio of V2O5 / rGO material to MOFs material in the coating is 1:0.05.

[0061] The method for preparing the above-mentioned positive electrode material comprises the following steps:

[0062] (1) Ammonium vanadate, oxalic acid and hexamethylenetetramine were dissolved in water at a molar ratio of 1:1:0.4, rGO was added, and the mass of the added rGO was twice the mass of the ammonium vanadate. The mixture was stirred at a speed of 800 r / min, heated to 320°C under stirring, and reacted for 15 h. The precipitate was washed with water, dried, and heated to 700°C at a rate of 18°C / min. The mixture was sintered for 4 h and cooled to obtain V2O5 / rGO material.

[0063] (2) The V2O5 / rGO material prepared in step (1) is mixed with a LiNi 0.9 Co 0.05 Mn 0.05 The positive electrode material is obtained by mixing lithium nickel cobalt manganese oxide and O2 and heating it at 150°C for 8 hours.

[0064] Comparative Example 2:

[0065] Weigh 1kg of ternary positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 O2, which was crushed in a jet mill to obtain ternary positive electrode material particles with a particle size D50 = 5 μm, which was used as the positive electrode material.

[0066] Test example:

[0067] The positive electrode materials from Examples 1-5 and Comparative Examples 1-2 were used as positive electrode materials for lithium-ion batteries. The mixture was mixed in a mass ratio of positive electrode material: acetylene black: polyvinylidene fluoride (PVDF) = 96:5:5, and then evenly coated onto plain aluminum foil to produce positive electrode sheets. Using the lithium sheet as the negative electrode, CR2430 button-type half-cells were assembled in an inert gas glove box. The battery performance was tested. The test results are shown in Table 1.

[0068] Table 1: Battery performance test results:

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

[0070] In addition, by comparing Example 3 with Comparative Example 1, it can be seen that when the wrapping layer does not contain MOFs material, the rate performance and 100 cycle capacity retention rate of the final battery will be significantly reduced. By comparing Example 3 with Comparative Example 2, it can be seen that the lithium battery made of the positive electrode material disclosed in the present invention has better high rate performance and cycle stability than the lithium battery made of a single ternary lithium cobalt manganese oxide material.

Claims

1. A positive electrode material, characterized in that: The positive electrode material includes a core and a wrapping layer, wherein the wrapping layer is wrapped around the core, the core includes a nickel cobalt lithium manganese oxide material, and the wrapping layer includes a MOFs material and a V2O5 / rGO material.

2. A positive electrode material according to claim 1, characterized in that: 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-xy>0.

3. A positive electrode material according to claim 1, characterized in that: The mass ratio of the core to the wrapping layer is 1:(0.15-0.25).

4. A positive electrode material according to claim 1, characterized in that: The mass ratio of V2O5 / rGO material to MOFs material in the encapsulating layer is 1:(0.01-0.1).

5. A method for preparing the positive electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) dissolving a vanadium source, an acid and a surfactant in water, adding rGO, heating the mixture under stirring, washing, drying, sintering and cooling to obtain a V2O5 / rGO material; (2) placing the V2O5 / rGO material obtained in step (1) into a MOFs generation solution for immersion, taking it out, and heating it to generate MOFs material on the surface and inside of the V2O5 / rGO material, thereby obtaining a coating layer material; (3) The coating layer material obtained in step (2) is mixed with lithium nickel cobalt manganese oxide and heated to obtain the positive electrode material.

6. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the vanadium source is at least one of ammonium vanadate, vanadium acetylacetonate and vanadyl acetylacetonate.

7. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the acid is at least one of oxalic acid and citric acid.

8. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the surfactant is at least one of hexamethylenetetramine and dodecyl alcohol amide.

9. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the molar ratio of the vanadium source, the acid and the surfactant is 1:1:(0.1-0.5).

10. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the mass of rGO added is 1.5-3 times the mass of the vanadium source.

11. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the stirring speed in the stirring state is 600-1000 r / min.

12. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the temperature of the temperature-raising reaction is 300-350° C., and the reaction time is 10-20 h.

13. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (1), the sintering is carried out by heating the temperature to 600-800°C at a rate of 15-20°C / min and sintering for 3-5h.

14. The method for preparing a positive electrode material according to claim 5, characterized in that: The MOFs generating solution in step (2) is prepared by dissolving Cr(NO3)3 and sodium benzoate in methanol in a molar ratio of (3-7):(2-5), and the ratio of Cr(NO3)3 to methanol is 5g:(50-100)ml.

15. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (2), the soaking time is 6-12 hours.

16. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (2), the heating temperature is 130-160° C., and the heating time is 12-24 hours.

17. The method for preparing a positive electrode material according to claim 5, characterized in that: In step (3), the heating temperature is 100-200° C. and the heating time is 2-12 h.

18. A lithium ion battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 4.

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