Positive electrode material, and preparation method therefor and use thereof

Abstract

A positive electrode material, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: (1) mixing a vanadium source, a complexing agent and a high-molecular polymer with an organic solvent to obtain a mixed solution; (2) respectively performing an atomization treatment on the mixed solution and a metal salt solution, and respectively conveying the mixed solution and the metal salt solution with a gas into a spray pyrolysis furnace to perform mixed pyrolysis, so as to obtain a coated precursor; and (3) mixing the coated precursor with a lithium source or a sodium source, and sintering same to obtain a positive electrode material. By using a spray pyrolysis method, the tap density and uniformity of the precursor are improved while the precursor is coated, such that a positive electrode material having good performance can be prepared.

Description

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

[0001] The embodiments of the present application relate to the field of battery material technology, such as a positive electrode material and its preparation method and application. Background Art

[0002] With the depletion of non-renewable resources and the resulting severe environmental pollution from the use of traditional energy sources, there is an urgent need to research and develop new energy and energy storage technologies. Lithium-ion batteries are a new generation of secondary batteries, offering advantages such as high specific capacity, excellent cycle performance, low self-discharge, and good safety. They have been applied in electronics, new energy vehicles, aerospace, and other fields. Sodium-ion batteries have abundant reserves and high battery safety. Their potential for application in new energy vehicle power batteries and large-scale energy storage has led many countries to focus on the development of sodium-ion battery technology. Common methods for preparing sodium and lithium battery cathode materials include sol-gel method, spray drying method, co-precipitation method, solid-phase method, hydrothermal method, etc.

[0003] CN112342605A discloses a low-cost, low-cobalt single-crystal nickel-cobalt-manganese ternary cathode material and its preparation method. A nickel source, cobalt oxide, manganese oxide, a lithium source, and an M dopant in a specific stoichiometric ratio are added to a grinder and wet-ground to a slurry with an insoluble particle size of ≤0.5 μm. The slurry is then spray-dried to produce an energy-saving, low-cost, low-cobalt, lithium-containing ternary precursor A. A is then sintered at high temperature in oxygen-rich conditions and pulverized to obtain a highly dispersed single-crystal ternary material matrix B. B is then dry-coated with X, solid-phase sintered at low temperature in an air atmosphere, and pulverized to obtain a low-cost, low-cobalt single-crystal cathode material.

[0004] CN115215388A discloses a method for preparing a ternary cathode material and a ternary cathode material, which are used to improve the preparation efficiency and yield of the ternary cathode material. The method comprises: mixing a manganese salt and / or aluminum salt with a nickel salt and a cobalt salt, and performing a coprecipitation reaction with an alkaline substance and a complexing agent in a solvent to obtain a coprecipitated slurry having a target median particle size; washing the coprecipitated slurry to obtain a ternary precursor slurry; mixing a lithium source with the ternary precursor slurry in an inert atmosphere to obtain a first mixture; drying the first mixture to obtain a second mixture; and subjecting the second mixture to a high-temperature sintering treatment to obtain the ternary cathode material.

[0005] The above scheme adopts co-precipitation method and high-temperature solid-phase method to prepare positive electrode materials. The co-precipitation process is complicated and tedious, and the reaction conditions need to be precisely controlled to keep the physical and chemical indicators of the materials consistent; high-temperature solid-phase sintering is difficult to achieve atomic-level mixing, which will cause local enrichment and low discharge specific capacity. In addition, the process morphology of high-temperature solid-phase preparation is irregular, the particle size is uneven, the degree of raw material mixing is limited, and a higher heat treatment temperature and a longer heat treatment time are required.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The embodiments of the present application provide a positive electrode material, a preparation method and an application thereof. The present application adopts a spray pyrolysis method with simple operation and mild conditions, which can achieve uniform mixing of materials at the atomic level, improve the tap density and uniformity of the precursor while coating it, and prepare a positive electrode material with excellent performance.

[0009] In a first aspect, an embodiment of the present application provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0010] (1) mixing a vanadium source, a complexing agent, a high molecular weight polymer, and an organic solvent to obtain a mixed solution;

[0011] (2) After the mixed solution and the metal salt solution are atomized, they are transported to a spray pyrolysis furnace by gas for mixed pyrolysis to obtain a coating precursor;

[0012] (3) The coated precursor is mixed with a lithium source or a sodium source, and the mixture is sintered to obtain the positive electrode material.

[0013] The present application prepares a coating solution of a vanadium source, a chelating agent and a high molecular polymer and performs spray pyrolysis synchronously with a mixed metal salt. During the atomization process, the high molecular polymer forms a cross-linked network through the action of viscosity, and the vanadium source generates a complex under the action of the chelating agent, which is dispersed in the cross-linked network of the high molecular polymer and then coated on the surface of the precursor to form a vanadium / carbon co-coated precursor. Due to the presence of micropores, the sintering efficiency can be improved in the subsequent mixed sintering process with a sodium source or a lithium source, and the wettability of the electrolyte can be improved after the battery is made. The present application can obtain a precursor with a micron-scale spherical morphology and a high tap density through a simple process, and then obtain a positive electrode material with uniform morphology and particle size, high reversible specific capacity at high voltage, and good cycle stability.

[0014] Preferably, the vanadium source in step (1) comprises ammonium metavanadate.

[0015] Preferably, the complexing agent comprises oxalic acid.

[0016] Preferably, the high molecular weight polymer includes polyvinyl pyrrolidone.

[0017] Preferably, the organic solvent comprises N,N-dimethylformamide.

[0018] Preferably, the molar concentration of the vanadium source in the mixed solution of step (1) is 0.001-0.1 mol / L, for example, 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.08 mol / L or 0.1 mol / L, etc., preferably 0.01-0.05 mol / L.

[0019] Preferably, the molar concentration of the complexing agent in the mixed solution is 0.002-0.2 mol / L, for example, 0.002 mol / L, 0.005 mol / L, 0.01 mol / L, 0.1 mol / L or 0.2 mol / L, and preferably 0.02-0.1 mol / L.

[0020] Preferably, the mass concentration of the high molecular weight polymer in the mixed solution is 10 to 30 g / L, for example, 10 g / L, 15 g / L, 20 g / L, 25 g / L or 30 g / L.

[0021] Preferably, the solute in the metal salt solution in step (2) includes any one of nickel salt, cobalt salt, manganese salt, copper salt or iron salt, or a combination of at least two of them.

[0022] Preferably, the total mass concentration of metal ions in the metal salt solution is 80-150 g / L, for example, 80 g / L, 90 g / L, 100 g / L, 120 g / L or 150 g / L.

[0023] Preferably, the atomization treatment includes ultrasonic atomization treatment.

[0024] Preferably, the temperature of the mixed pyrolysis in step (2) is 700-950°C, for example, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C.

[0025] Preferably, the gas comprises nitrogen and / or oxygen.

[0026] The choice of carrier gas in this application will affect the type of precursor generated. Using oxygen as the carrier gas will generate an oxide precursor, and using nitrogen will generate a hydroxide precursor. The choice can be made according to actual needs.

[0027] This application uses oxygen to transport a mixed coating liquid of an atomized metal salt solution. The vanadium in the coating liquid is oxidized under high temperature conditions to form a vanadium pentoxide / carbon coating layer. The vanadium pentoxide has excellent electrochemical properties and has unique lithium insertion advantages. The carbon layer can improve the conductivity. The vanadium pentoxide / carbon coating layer can improve the conductivity of the positive electrode material while also improving the electrochemical performance of the material.

[0028] Preferably, the flow rate of the gas is 3 to 8 L / min, for example, 3 L / min, 4 L / min, 5 L / min, 6 L / min or 8 L / min.

[0029] Preferably, the lithium source in step (3) includes any one of lithium hydroxide, lithium carbonate or lithium nitrate, or a combination of at least two of them.

[0030] Preferably, the sodium source includes any one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium bisulfate, sodium oxalate, sodium hydroxide, sodium nitrate or sodium acetate, or a combination of at least two thereof.

[0031] Preferably, the total molar ratio of the molar amount of the lithium element in the lithium source or the sodium element in the sodium source to the main metal element in the coating precursor is 1 to 1.15:1, for example: 1:1, 1.05:1, 1.08:1, 1.1:1 or 1.15:1.

[0032] The main metal elements mentioned in this application are all metal elements except vanadium.

[0033] Preferably, the sintering process in step (3) includes one-stage sintering and two-stage sintering.

[0034] Preferably, the temperature of the first stage sintering is 550-600°C, for example, 550°C, 560°C, 570°C, 580°C or 600°C.

[0035] Preferably, the sintering time is 8 to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0036] Preferably, the temperature of the second-stage sintering is 800-900°C, for example, 800°C, 820°C, 850°C, 880°C or 900°C.

[0037] Preferably, the second-stage sintering time is 20 to 30 hours, for example, 20 hours, 22 hours, 24 hours, 28 hours or 30 hours.

[0038] In a second aspect, an embodiment of the present application provides a positive electrode material, which is prepared by the method described in the first aspect.

[0039] In a third aspect, an embodiment of the present application provides a positive electrode plate, which comprises the positive electrode material as described in the second aspect.

[0040] In a fourth aspect, an embodiment of the present application provides a battery, which includes the positive electrode plate as described in the third aspect.

[0041] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0042] (1) The embodiments of the present application form a highly conductive carbon / vanadium composite coating on the surface of the positive electrode precursor through a spray pyrolysis method, thereby improving the material's tap density and uniformity while also improving the material's stability and conductivity, resulting in a material with high reversible specific capacity and good cycle stability at high voltage.

[0043] (2) The method described in the embodiments of the present application is applicable to sodium ion battery positive electrode materials and lithium ion battery positive electrode materials. The initial discharge specific capacity of the prepared lithium ion battery positive electrode material can reach 165 mAh / g, and the capacity retention rate can reach 96.8% after 100 cycles at a rate of 1C. The initial discharge specific capacity of the prepared sodium ion battery positive electrode material can reach 143.2 mAh / g, and the capacity retention rate can reach 92.6% after 100 cycles at a rate of 1C.

[0044] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0045] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0046] Example 1

[0047] This embodiment provides a positive electrode material, which is prepared by the following method:

[0048] (1) ammonium metavanadate, oxalic acid, and polyvinylpyrrolidone (PVP) are mixed with N,N-dimethylformamide (DMF) to obtain a mixed solution, wherein the concentration of oxalic acid is 0.08 mol / L, the concentration of ammonium metavanadate is 0.04 mol / L, and the concentration of polyvinylpyrrolidone is 20 g / L;

[0049] (2) nickel sulfate, manganese sulfate, and cobalt sulfate were prepared into a metal salt solution according to Ni:Co:Mn=8:1:1, and the total mass concentration of metal ions in the metal salt solution was 100 g / L. The mixed solution and the metal salt solution were atomized, and then transported to a spray pyrolysis furnace using nitrogen at a flow rate of 4 L / min, and the mixed solution was pyrolyzed at 700 ° C to obtain a coated precursor;

[0050] (3) The coated precursor is mixed with lithium hydroxide according to Li / M=1.1:1, and sintered in two stages under an oxygen atmosphere. The heating rate of the first sintering stage is 3°C / min, and the temperature is kept at 580°C for 10 hours; the heating rate of the second sintering stage is 3°C / min, and the temperature is kept at 850°C for 24 hours to obtain the positive electrode material.

[0051] Example 2

[0052] This embodiment provides a positive electrode material, which is prepared by the following method:

[0053] (1) ammonium metavanadate, oxalic acid, and polyvinylpyrrolidone (PVP) are mixed with N,N-dimethylformamide (DMF) to obtain a mixed solution, wherein the concentration of oxalic acid is 0.1 mol / L, the concentration of ammonium metavanadate is 0.05 mol / L, and the concentration of polyvinylpyrrolidone is 22 g / L;

[0054] (2) manganese sulfate, copper sulfate and ferric sulfate were prepared into a metal salt solution according to Mn:Cu:Fe=0.45:0.45:0.4, and the total mass concentration of metal ions in the metal salt solution was 110 g / L. The mixed solution and the metal salt solution were atomized and then transported to a spray pyrolysis furnace using oxygen at a flow rate of 5 L / min. The mixed solution was pyrolyzed at 700 °C to obtain a coated precursor;

[0055] (3) The coated precursor is mixed with sodium carbonate according to Na / M=1.1:1, and sintered in two stages under an oxygen atmosphere. The heating rate of the first sintering stage is 3°C / min, and the temperature is kept at 550°C for 10 hours; the heating rate of the second sintering stage is 3°C / min, and the temperature is kept at 800°C for 24 hours to obtain the positive electrode material.

[0056] Example 3

[0057] The only difference between this embodiment and embodiment 1 is that the molar concentration of the vanadium source in the mixed solution is 0.01 mol / L, and the molar concentration of the complexing agent is 0.02 mol / L. Other conditions and parameters are exactly the same as those in embodiment 1.

[0058] Example 4

[0059] The only difference between this embodiment and embodiment 1 is that the molar concentration of the vanadium source in the mixed solution is 0.05 mol / L, and the molar concentration of the complexing agent is 0.1 mol / L. Other conditions and parameters are exactly the same as those in embodiment 1.

[0060] Example 5

[0061] The only difference between this embodiment and embodiment 1 is that the mass concentration of the high molecular weight polymer in the mixed solution is 10 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0062] Example 6

[0063] The only difference between this embodiment and embodiment 1 is that the mass concentration of the high molecular weight polymer in the mixed solution is 30 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0064] Comparative Example 1

[0065] The only difference between this comparative example and Example 1 is that no mixed solution is added during the spray pyrolysis process, and other conditions and parameters are exactly the same as those in Example 1.

[0066] Performance testing:

[0067] The positive electrode materials prepared in Examples 1-6 and Comparative Example 1 were made into buckle batteries, and the initial discharge specific capacity and capacity retention rate after 100 cycles at 2.8-4.3V, 25°C, and a rate of 1C were tested. The test results are shown in Table 1:

[0068] Table 1

[0069] As can be seen from Table 1, it can be obtained from Examples 1-2 that the method described in the present application is applicable to sodium ion battery positive electrode materials and lithium ion battery positive electrode materials, and the first discharge specific capacity of the prepared lithium ion battery positive electrode material can reach 165 mAh / g, and the capacity retention rate can reach 96.8% after 100 cycles at a rate of 1C. The first discharge specific capacity of the prepared sodium ion battery positive electrode material can reach 143.2 mAh / g, and the capacity retention rate can reach 92.6% after 100 cycles at a rate of 1C.

[0070] By comparing Example 1 with Examples 3-4, it can be seen that during the preparation process of the positive electrode material described in the present application, the concentration of the vanadium source in the mixed solution will affect its performance. The concentration of the vanadium source in the mixed solution is controlled at 0.01-0.05 mol / L (the corresponding complexing agent is adjusted to twice the vanadium source), and the positive electrode material obtained has better performance. If the concentration of the vanadium source is too high, the proportion of vanadium in the coating layer is too large and the proportion of carbon is too small, which affects the conductive properties of the material. If the concentration of the vanadium source is too low, the vanadium content in the coating layer is reduced, and the electrical properties of the material are reduced.

[0071] By comparing Example 1 with Examples 5-6, it can be seen that during the preparation process of the positive electrode material described in this application, the concentration of the polymer in the mixed solution will affect its performance. When the concentration of the polymer in the mixed solution is controlled at 10-30 g / L, the positive electrode material obtained has better performance. If the concentration of the polymer material is too high, the coating layer is too thick, which affects the electrical properties of the material. If the concentration of the polymer material is too low, a complete cross-linked network cannot be formed, and the conductive performance of the material decreases.

[0072] By comparison between Example 1 and Comparative Example 1, it can be seen that in the present application, a vanadium source, a chelating agent and a high molecular polymer are prepared into a coating solution and spray pyrolysis is carried out simultaneously with a mixed metal salt. During the atomization process, the high molecular polymer forms a cross-linked network through viscosity, and the vanadium source generates a complex under the action of the chelating agent, which is dispersed in the cross-linked network of the high molecular polymer and then coated on the surface of the precursor. After pyrolysis, the high molecular polymer is carbonized to form micropores, forming a vanadium / carbon co-coated precursor, thereby obtaining a positive electrode material with excellent performance.

[0073] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a positive electrode material, comprising the following steps: (1) mixing a vanadium source, a complexing agent, a high molecular weight polymer and an organic solvent to obtain a mixed solution; (2) After the mixed solution and the metal salt solution are respectively atomized, they are respectively transported to a spray pyrolysis furnace by gas for mixed pyrolysis to obtain a coating precursor; (3) The coated precursor is mixed with a lithium source or a sodium source, and the positive electrode material is obtained by sintering.

2. The preparation method according to claim 1, wherein The vanadium source in step (1) includes ammonium metavanadate.

3. The preparation method according to claim 1 or 2, wherein: The complexing agent includes oxalic acid.

4. The preparation method according to any one of claims 1 to 3, wherein The high molecular polymer includes polyvinyl pyrrolidone.

5. The preparation method according to any one of claims 1 to 4, wherein: The organic solvent includes N,N-dimethylformamide.

6. The preparation method according to any one of claims 1 to 5, wherein: The molar concentration of the vanadium source in the mixed solution of step (1) is 0.001 to 0.1 mol / L, preferably 0.01 to 0.05 mol / L; Preferably, the molar concentration of the complexing agent in the mixed solution is 0.002 to 0.2 mol / L, preferably 0.02 to 0.1 mol / L; Preferably, the mass concentration of the high molecular weight polymer in the mixed solution is 10 to 30 g / L.

7. The preparation method according to any one of claims 1 to 6, wherein: The solute in the metal salt solution of step (2) includes any one of nickel salt, cobalt salt, manganese salt, copper salt or iron salt, or a combination of at least two thereof; Preferably, the total mass concentration of metal ions in the metal salt solution is 80 to 150 g / L; Preferably, the atomization treatment comprises ultrasonic atomization treatment.

8. The preparation method according to any one of claims 1 to 7, wherein: The temperature of the mixed pyrolysis in step (2) is 700-950° C. Preferably, the gas comprises nitrogen and / or oxygen; Preferably, the flow rate of the gas is 3 to 8 L / min.

9. The preparation method according to any one of claims 1 to 8, wherein: The lithium source in step (3) includes any one of lithium hydroxide, lithium carbonate or lithium nitrate, or a combination of at least two thereof; Preferably, the sodium source comprises any one or a combination of at least two of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium bisulfate, sodium oxalate, sodium hydroxide, sodium nitrate or sodium acetate; Preferably, the total molar ratio of the molar amount of the lithium element in the lithium source or the sodium element in the sodium source to the main metal element in the coating precursor is 1 to 1.15:

1.

10. The preparation method according to any one of claims 1 to 9, wherein: The sintering process in step (3) includes a first stage sintering and a second stage sintering; Preferably, the temperature of the first stage sintering is 550-600°C; Preferably, the sintering time is 8 to 12 hours; Preferably, the temperature of the second stage sintering is 800-900°C; Preferably, the second-stage sintering time is 20 to 30 hours.

11. A positive electrode material, wherein: The positive electrode material is prepared by the method according to any one of claims 1 to 10.

12. A positive electrode sheet, wherein: The positive electrode sheet comprises the positive electrode material as claimed in claim 11.

13. A battery, wherein: The battery comprises the positive electrode sheet as claimed in claim 12.

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