Composite phosphate series sodium battery positive electrode material as well as preparation method and application thereof

Abstract

The invention particularly relates to a composite phosphate series sodium battery positive electrode material as well as a preparation method and application thereof. The preparation method of the composite phosphate series sodium battery positive electrode material comprises the following steps: dissolving a phosphorus source, an iron source and a sodium source in a solvent to obtain mixed slurry; adding a dispersing agent, mixing, and sanding by using a sand mill until the particle size D50 is less than 100nm; carrying out spray drying on the sanded slurry to obtain powder A; dissolving a carbon source in a solvent to obtain a carbon source solution; placing the powder A in a horizontal stirring tank with a heating function, atomizing and spraying the carbon source solution into the powder A while stirring, and heating and drying to obtain powder B; and sintering the powder B in an inert atmosphere to obtain the composite phosphate sodium battery positive electrode material. According to the preparation method disclosed by the invention, the electrochemical performance and the physical performance of the positive electrode material are remarkably improved, and the obtained composite phosphate sodium battery positive electrode material shows good specific capacity, rate capability and cycling stability.

Description

Technical Field

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

[0002] As the global demand for renewable energy continues to grow, the development of efficient and low-cost energy storage technology has become a hot topic in current research. As the most mainstream secondary battery technology, lithium-ion batteries have achieved great commercial success, but their application in large-scale energy storage is limited due to the uneven distribution of lithium resources and cost issues. Sodium atoms have similar atomic structures and chemical properties to lithium atoms, and the global reserves of sodium are extremely abundant and low-cost, so they are considered to be a powerful alternative to lithium-ion batteries.

[0003] In recent years, composite phosphate cathode materials have gradually become the research focus of sodium ion battery cathode materials due to their advantages in safety, thermal stability and structural stability. The theoretical specific capacity of this type of material is 129mAh / g, and many literature reports show that this type of material can reach a discharge specific capacity of about 120mAh / g, and the discharge termination voltage is about 1.5V. Although a higher specific capacity can be obtained in the laboratory, the preparation process of this material generally adopts the spray drying method, and the mixed slurry before spray drying often has poor solubility and high viscosity. In addition, glucose as a carbon source is easy to caramelize during high-temperature drying, which not only easily causes grain aggregation and affects crystallinity, but also easily leads to material blocking problems during spray drying, reducing production efficiency, and the consistency of batch production will be greatly affected. Due to the influence of the process, it often leads to uneven carbon coating, a wide distribution of spherical particle size, and the presence of hollow spheres. In addition, the lower crystallinity ultimately leads to a decrease in the reversible specific capacity of the material, a lower tap density leads to a decrease in the compaction density of the pole piece, and a significant decrease in energy density, which is not suitable for commercial applications.

[0004] Although some studies have attempted to optimize the production process and improve production efficiency by reducing slurry viscosity and increasing solid content, the prepared materials often have low crystallinity and uneven carbon coating. In the voltage range of 2 to 4 V, the discharge specific capacity is generally less than 110 mAh / g. Materials with higher discharge specific capacity prepared by other methods often have smaller grains and larger gaps between particles, resulting in lower tap density of the material. Although the discharge specific capacity of the material can be improved by improving the process, doing so often sacrifices the tap density; conversely, if a high tap density is pursued, the discharge specific capacity may decrease. How to achieve both high reversible specific capacity and high tap density at the same time has become a technical problem.

[0005] The present invention aims to solve the above problems and proposes a method for preparing a composite phosphate sodium positive electrode material, improves the carbon coating uniformity of the material, and solves the problem of its unsatisfactory tap density, so as to achieve higher energy density, better electrochemical performance and lower production cost. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a composite phosphate sodium positive electrode material, which significantly improves the electrochemical and physical properties of the positive electrode material, and prepares a composite phosphate sodium positive electrode material with excellent electrochemical properties and high tap density. The composite phosphate sodium positive electrode material obtained by the present invention is applied to sodium ion batteries, showing good specific capacity, rate performance and cycle stability.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows:

[0008] A method for preparing a composite phosphate sodium positive electrode material comprises the following steps:

[0009] S1. dissolving a phosphorus source, an iron source and a sodium source in a solvent to obtain a mixed slurry;

[0010] S2. Add the dispersant, mix and grind using a sand mill until the particle size D50 is less than 100 nm;

[0011] S3. The sand-milled slurry is spray-dried to obtain powder A;

[0012] S4. dissolving the carbon source in a solvent to obtain a carbon source solution;

[0013] S5. Powder A is placed in a horizontal stirring tank with a heating function, and the carbon source solution is sprayed on powder A while stirring, and heated and dried to obtain powder B;

[0014] S6. Sintering powder B under an inert atmosphere to obtain a composite phosphate-based sodium positive electrode material.

[0015] Preferably, the phosphorus source is at least one of diammonium phosphate, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, and diammonium hydrogen phosphate.

[0016] Preferably, the iron source is at least one of ferrous oxalate, ferrous oxide, ferrous oxide, ferric phosphate, ferric pyrophosphate, ferrous citrate, ferrous acetylacetonate, ferrous nitrate, ferrous sulfate, ferrous oxalate, and ferric acetate.

[0017] Preferably, the sodium source is at least one of sodium carbonate, sodium phosphate, sodium monohydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium nitrate, sodium oxalate, sodium pyrophosphate, sodium hydrogen pyrophosphate, sodium formate, sodium acetate, sodium ethoxide, sodium hydroxide, and sodium citrate.

[0018] Preferably, the molar ratio of phosphorus in the phosphorus source, iron in the iron source and sodium in the sodium source is 4:(2.9-3):4.

[0019] Preferably, the solvent includes water or a mixed solvent of water and one or more of methanol, ethanol, propylene oxide, and ethanolamine.

[0020] Preferably, the solid content of the mixed slurry is 20-40wt%.

[0021] Preferably, the added amount of the dispersant is 0.3% to 2% of the mass of the mixed slurry.

[0022] Preferably, the dispersant is at least one of a polyether dispersant, a styrene maleic anhydride dispersant, a saturated olefin dispersant, an acrylic dispersant, an amide dispersant, and a polyurethane dispersant.

[0023] Preferably, the rotation speed of the sand mill is 1000-1200 rpm, and the sand milling time is 2-6 hours.

[0024] Preferably, the spray drying temperature is 120-250°C.

[0025] Preferably, the carbon source is a small molecule carbon source.

[0026] Specifically, the carbon source is one or more of glucose, xylose, ribose, and deoxyribose.

[0027] Preferably, the mass of the carbon source is 2% to 3% of the total mass of the phosphorus source, the iron source and the sodium source.

[0028] More preferably, the mass of the carbon source is 2.5% of the total mass of the phosphorus source, the iron source, and the sodium source. The researchers found that when the added mass of the carbon source is 2.5% of the total mass of the phosphorus source, the iron source, and the sodium source, the electrochemical performance of the resulting positive electrode material is optimal.

[0029] Preferably, the solid content of the carbon source solution is 10 to 50 wt%.

[0030] Preferably, the mass of the carbon source solution sprayed by atomization is 1% to 50% of the mass of the powder A.

[0031] More preferably, the mass of the carbon source solution sprayed by atomization is 10% to 20% of the mass of the powder A. If the mass of the carbon source solution sprayed by atomization is less than 10% of the powder A, insufficient wetting may occur; if the mass of the carbon source solution sprayed by atomization is greater than 20% of the powder A, repeated wetting may occur, resulting in uneven coating.

[0032] Preferably, the atomization spraying method comprises: atomizing the carbon source solution with an atomization device, and then spraying it into powder A.

[0033] Preferably, the atomizing device is an atomizing nozzle.

[0034] Preferably, the stirring speed of the horizontal stirring tank is 30 to 100 rpm; and the feeding speed of the atomizing device is 0.05 to 5 L / min.

[0035] Preferably, the heating and drying temperature is 100-250°C.

[0036] Preferably, the sintering is a two-stage sintering, the first stage sintering temperature is 200-400° C., the holding time is 1-3 hours, and the second stage sintering temperature is 500-650° C., the holding time is 10-20 hours.

[0037] Preferably, the preparation method further comprises subjecting the sintered composite phosphate sodium cathode material to airflow pulverization to a particle size of D50 = 5 to 10 μm.

[0038] The present invention also provides a composite phosphate sodium positive electrode material prepared by the above preparation method.

[0039] The present invention also provides the use of the composite phosphate sodium positive electrode material in the preparation of a sodium ion battery.

[0040] The present invention also provides a sodium ion battery, comprising a composite phosphate-based sodium positive electrode material.

[0041] Specifically, the sodium ion battery is composed of the composite phosphate sodium positive electrode material as the positive electrode, and is assembled with the negative electrode, a separator and an electrolyte.

[0042] The present invention has the following beneficial effects:

[0043] Compared with the existing methods for preparing phosphate-based sodium cathode materials, the present invention uses an atomization method to evenly attach the carbon source to the surface of the precursor, effectively solving the problem of caramelization and wall adhesion of glucose carbon source in the traditional solution spray method; at the same time, the method also solves the problem of uneven thickness of the carbon coating of the spherical particles obtained by spraying, ensuring the uniformity of the carbon coating layer, thereby significantly improving the conductivity and compaction density of the material, and further improving the electrochemical properties such as specific capacity and rate of the composite phosphate-based sodium cathode material. Through the preparation method of the present invention, the morphology of the crystals can be accurately controlled and the crystallinity of the crystals can be improved to obtain a pyrophosphate-based cathode material with a plug-shaped cactus structure and uniform particle size. Thanks to the uniform carbon coating layer and the optimized crystal structure, the composite phosphate-based sodium cathode material prepared by the present invention has a high tap density, which significantly improves the sodium storage capacity and Na at the Na site.+ The migration rate is increased, thereby improving the electrochemical properties of the positive electrode material, such as specific capacity and rate.

[0044] The present invention provides a method for preparing a composite phosphate sodium positive electrode material, which significantly improves the electrochemical and physical properties of the positive electrode material, and prepares a composite phosphate sodium positive electrode material with excellent electrochemical properties and high tap density. The composite phosphate sodium positive electrode material obtained by the present invention is applied to sodium ion batteries, and exhibits good specific capacity, rate performance and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 XRD comparison diagrams of the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0046] Figure 2 This is a SEM image of the composite phosphate sodium positive electrode material prepared in Example 1;

[0047] Figure 3 This is a SEM image of the composite phosphate sodium positive electrode material prepared in Example 1;

[0048] Figure 4 The first charge and discharge curve of the composite phosphate sodium positive electrode material prepared in Example 1;

[0049] Figure 5 This is a long cycle performance data diagram of the composite phosphate sodium cathode material prepared in Example 1;

[0050] Figure 6 This is a data diagram of the rate performance of the composite phosphate sodium cathode material prepared in Example 1;

[0051] Figure 7 It is a comparison diagram of the first charge and discharge curves of the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0052] Figure 8 Schematic diagram of a horizontal stirring tank with heating function and an atomizing device used in preparing composite phosphate sodium positive electrode materials in Examples 1 to 3. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention clearer, the following will be described in detail with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and are not limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0054] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0055] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0056] Embodiment 1:

[0057] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%; 59.689

[0058] S2. Add 0.995 kg of acrylic dispersant (specifically, an aqueous aliphatic acrylic dispersion), mix, and grind at 1200 rpm for 4 h using a sand mill until the particle size D50 = 80 nm;

[0059] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 160°C to obtain powder A;

[0060] S4. Dissolving 1.492 kg of glucose in 3.482 kg of water to obtain a glucose solution having a mass fraction of 30 wt %;

[0061] S5. 40 kg of powder A was placed in a horizontal stirring tank with a heating function, stirred at a speed of 60 rpm, and 4.974 kg of glucose solution was atomized by an atomizing nozzle, and then sprayed on powder A. The feed rate of the atomizing device was 0.06 L / min, and heated and dried at 120 ° C to obtain powder B;

[0062] S6. The powder B was sintered under an inert atmosphere, wherein the sintering was a two-stage sintering, wherein the first stage was sintered at a temperature of 250°C for a holding time of 1 h, the second stage was sintered at a temperature of 550°C for a holding time of 10 h, and the heating rate was 1 to 5°C / min to obtain a composite phosphate sodium positive electrode material;

[0063] S7. The sintered composite phosphate sodium positive electrode material is subjected to air flow pulverization treatment to be pulverized to a particle size of D50 = 8 μm.

[0064] Embodiment 2:

[0065] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%;

[0066] S2. Then add 0.995kg of aliphatic acrylic acid aqueous dispersion, mix and grind with a sand mill at 1200rpm for 4h until the particle size D50 = 80nm;

[0067] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 160°C to obtain powder A;

[0068] S4. Dissolve 1.492 kg of glucose in 6.797 L of water to obtain a glucose solution with a mass fraction of 18 wt %;

[0069] S5. 40 kg of powder A was placed in a horizontal stirring tank with a heating function, stirred at a speed of 60 rpm, and 8.289 kg of glucose solution was atomized by an atomizing nozzle, and then sprayed on powder A. The feed rate of the atomizing device was 0.06 L / min, and heated and dried at 120 ° C to obtain powder B;

[0070] S6. The powder B was sintered under an inert atmosphere, wherein the sintering was a two-stage sintering, wherein the first stage was sintered at a temperature of 250°C for a holding time of 1 h, the second stage was sintered at a temperature of 550°C for a holding time of 10 h, and the heating rate was 1 to 5°C / min to obtain a composite phosphate sodium positive electrode material;

[0071] S7. The sintered composite phosphate sodium positive electrode material is subjected to air flow pulverization treatment to be pulverized to a particle size of D50 = 8 μm.

[0072] Embodiment 3:

[0073] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%;

[0074] S2. Then add 0.995kg of aliphatic acrylic acid aqueous dispersion, mix and grind with a sand mill at 1200rpm for 4h until the particle size D50 = 80nm;

[0075] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 160°C to obtain powder A;

[0076] S4. Dissolve 1.492 kg of glucose in 2.238 L of water to obtain a glucose solution with a mass fraction of 40 wt %;

[0077] S5. 40 kg of powder A was placed in a horizontal stirring tank with a heating function, stirred at a speed of 60 rpm, and 3.730 kg of glucose solution was atomized by an atomizing nozzle, and then sprayed on powder A. The feed rate of the atomizing device was 0.06 L / min, and heated and dried at 120 ° C to obtain powder B;

[0078] S6. The powder B was sintered under an inert atmosphere, wherein the sintering was a two-stage sintering, wherein the first stage was sintered at a temperature of 250°C for a holding time of 1 h, the second stage was sintered at a temperature of 550°C for a holding time of 10 h, and the heating rate was 1 to 5°C / min to obtain a composite phosphate sodium positive electrode material;

[0079] S7. The sintered composite phosphate sodium positive electrode material is subjected to air flow pulverization treatment to be pulverized to a particle size of D50 = 8 μm.

[0080] The horizontal stirring tank with heating function and the atomizing device used in the preparation of the composite phosphate sodium positive electrode material in Examples 1 to 3 are as follows: Figure 8 As shown, in a horizontal stirring tank with a heating function, the stirring paddle stirs at a speed of 60 rpm, and at the same time, the atomizing nozzle atomizes the glucose solution at a feeding rate of 0.06 L / min, and then sprays it on the powder A. When the mass of the atomized sprayed glucose solution is 10% to 20% of the mass of the powder A, the stirring speed of the horizontal stirring tank is 30 to 100 rpm, and the feeding rate of the atomizing device is 0.05 to 5 L / min, the glucose solution can be evenly sprayed on the surface of the powder A to ensure uniform coating.

[0081] Comparative Example 1:

[0082] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%;

[0083] S2. Then add 0.995kg of aliphatic acrylic acid aqueous dispersion, mix and grind with a sand mill at 1200rpm for 4h until the particle size D50 = 80nm;

[0084] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 160°C to obtain powder A;

[0085] S4. Dissolving 1.791 kg of glucose in 6.498 kg of water to obtain a glucose solution having a mass fraction of 22 wt %;

[0086] S5. 40 kg of powder A was placed in a horizontal stirring tank with a heating function, stirred at a speed of 60 rpm, and 8.289 kg of glucose solution was atomized by an atomizing nozzle, and then sprayed on powder A. The feed rate of the atomizing device was 0.06 L / min, and heated and dried at 120 ° C to obtain powder B;

[0087] S6. The powder B was sintered under an inert atmosphere, wherein the sintering was a two-stage sintering, wherein the first stage was sintered at a temperature of 250°C for a holding time of 1 h, the second stage was sintered at a temperature of 550°C for a holding time of 10 h, and the heating rate was 1 to 5°C / min to obtain a composite phosphate sodium positive electrode material;

[0088] S7. The sintered composite phosphate sodium positive electrode material is subjected to air flow pulverization treatment to be pulverized to a particle size of D50 = 8 μm.

[0089] Comparative Example 2:

[0090] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%;

[0091] S2. Then add 0.995kg of aliphatic acrylic acid aqueous dispersion, mix and grind with a sand mill at 1200rpm for 4h until the particle size D50 = 80nm;

[0092] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 160°C to obtain powder A;

[0093] S4. Dissolve 1.194 kg of glucose in 2.536 kg of water to obtain a glucose solution with a mass fraction of 32 wt %;

[0094] S5. 40 kg of powder A was placed in a horizontal stirring tank with a heating function, stirred at a speed of 60 rpm, and 3.730 kg of glucose solution was atomized by an atomizing nozzle, and then sprayed on powder A. The feed rate of the atomizing device was 0.06 L / min, and heated and dried at 120 ° C to obtain powder B;

[0095] S6. The powder B was sintered under an inert atmosphere, wherein the sintering was a two-stage sintering, wherein the first stage was sintered at a temperature of 250°C for a holding time of 1 h, the second stage was sintered at a temperature of 550°C for a holding time of 10 h, and the heating rate was 1 to 5°C / min to obtain a composite phosphate sodium positive electrode material;

[0096] S7. The sintered composite phosphate sodium positive electrode material is subjected to air flow pulverization treatment to be pulverized to a particle size of D50 = 8 μm.

[0097] Comparative Example 3:

[0098] S1. Dissolve 23.004 kg of ammonium dihydrogen phosphate, 26.086 kg of ferrous oxalate, and 10.599 kg of sodium carbonate in 139.273 L of water to obtain a mixed slurry with a solid content of 30 wt%;

[0099] S2. Then add 0.995kg aliphatic acrylic acid aqueous dispersion and 1.492kg glucose, mix and use a sand mill at a speed of 1200rpm for 4h until the particle size D50 = 80nm;

[0100] S3. The sand-milled slurry was spray-dried at an air inlet temperature of 220° C. to obtain a precursor powder A;

[0101] S4. The precursor powder A is sintered under an inert atmosphere, wherein the sintering is a two-stage sintering, wherein the sintering temperature of the first stage is 250°C, the holding time is 1h, the sintering temperature of the second stage is 550°C, the holding time is 10h, and the heating rate is 1 to 5°C / min;

[0102] S5. The sintered sample is subjected to air flow pulverization treatment and pulverized to a particle size of D50 = 8 μm to obtain a pyrophosphate-based sodium positive electrode material.

[0103] The positive electrode materials prepared in the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to electrochemical performance tests and tap density tests. The main test steps are as follows:

[0104] Preparation of battery: Weigh the positive electrode material obtained in the embodiment and comparative example, Super P conductive carbon black, and binder PVDF according to the mass ratio of 8:1:1, dissolve in NMP, stir and mix, and degas, and apply it on the aluminum foil current collector by a coating machine, with a coating thickness of 150μm, dry the aluminum foil coated with slurry in a vacuum drying oven at 80℃ for 12 hours, and cut the electrode sheet into small discs with a diameter of 12mm by a cutting machine after drying; transfer the dried electrode sheet to the glove box, assemble the button battery in the order of positive electrode shell, electrode sheet, glass fiber diaphragm, sodium sheet, gasket, shrapnel, and negative electrode shell, and then use a sealing machine to seal. The electrochemical performance of the battery was tested on the Xinwei battery test system, and constant current charge and discharge tests were carried out at a current density of 0.1C, with a charge and discharge voltage range of 2 to 4.2V.

[0105] The tap density test was carried out using a tap density meter, and the test results are shown in Table 1.

[0106] Figure 1 XRD comparison diagrams of the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0107] Figures 2-3This is a SEM image of the composite phosphate sodium positive electrode material prepared in Example 1;

[0108] Figure 4 The first charge and discharge curve of the composite phosphate sodium positive electrode material prepared in Example 1; Figure 5 This is a long cycle performance data diagram of the composite phosphate sodium cathode material prepared in Example 1; Figure 6 This is a data chart of the rate performance of the composite phosphate sodium positive electrode material prepared in Example 1. Figure 4-6 It can be seen that the composite phosphate sodium cathode material prepared in Example 1 of the present invention has good electrochemical properties. At a current density of 0.1C, in the voltage range of 2 to 4V, it has a high discharge specific capacity of 123.12mAh / g; at a high rate current density of 5C, it has a reversible capacity of 100.92mAh / g; and after 100 cycles, the capacity retention rate is more than 95%.

[0109] Figure 7 It is a comparison chart of the first charge and discharge curves of the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3.

[0110] Table 1: Comparison of tap density of positive electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3

[0111] <![CDATA[Tap density g / cm 3 > First discharge specific capacity mAh / g Initial efficiency % Example 1 1.35 123 101 Example 2 1.15 119 95 Example 3 1.10 118 94 Comparative Example 1 0.85 102 102 Comparative Example 2 0.90 100 96 Comparative Example 3 0.71 104 95

[0112] Depend on Figure 7 As can be seen from Table 1, compared with the positive electrode material prepared by the comparative example preparation method, the preparation method of the embodiment of the present invention prepares a composite phosphate-based sodium positive electrode material with excellent electrochemical properties and high tap density, which is applied to sodium ion batteries and exhibits good specific capacity, rate performance and cycle stability.

[0113] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0114] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0115] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a composite phosphate sodium positive electrode material, characterized in that: The following steps are involved: S1. dissolving a phosphorus source, an iron source and a sodium source in a solvent to obtain a mixed slurry; S2. Add a dispersant, mix and grind using a sand mill until the particle size D50 is less than 100 nm; S3. The sand-milled slurry is spray-dried to obtain powder A; S4. dissolving the carbon source in a solvent to obtain a carbon source solution; S5. Powder A is placed in a horizontal stirring tank with a heating function, and the carbon source solution is sprayed on powder A while stirring, and heated and dried to obtain powder B; S6. Sintering powder B under an inert atmosphere to obtain a composite phosphate-based sodium positive electrode material.

2. The method for preparing the composite phosphate sodium positive electrode material according to claim 1, characterized in that: The molar ratio of phosphorus in the phosphorus source, iron in the iron source and sodium in the sodium source is 4:(2.9-3):4; the solid content of the mixed slurry is 20-40wt%.

3. The method for preparing the composite phosphate sodium positive electrode material according to claim 1, characterized in that: The added amount of the dispersant is 0.3% to 2% of the mass of the mixed slurry.

4. The method for preparing the composite phosphate sodium positive electrode material according to claim 1, characterized in that: The mass of the carbon source is 2% to 3% of the total mass of the phosphorus source, the iron source and the sodium source.

5. The method for preparing the composite phosphate sodium positive electrode material according to claim 1, characterized in that: The solid content of the carbon source solution is 10-50 wt %; the mass of the carbon source solution sprayed by atomization is 1%-50% of the mass of the powder A.

6. The method for preparing the composite phosphate sodium positive electrode material according to claim 1, characterized in that: The atomization spraying method includes: atomizing the carbon source solution with an atomization device, and then spraying it into the powder A.

7. The method for preparing the composite phosphate sodium positive electrode material according to claim 6, characterized in that: In step S5, the stirring speed of the horizontal stirring tank is 30-100 rpm; the feeding speed of the atomizing device is 0.05-5 L / min.

8. A composite phosphate sodium positive electrode material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the composite phosphate sodium positive electrode material according to claim 8 in the preparation of sodium ion batteries.

10. A sodium ion battery, characterized in that: Including the composite phosphate sodium positive electrode material as described in claim 9.

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