Preparation method of power-type sodium iron phosphate pyrophosphate positive electrode material

Abstract

The application provides a preparation method of a power-type sodium iron phosphate positive electrode material, which comprises the following steps: using ferrous oxalate to match a composite iron source and a sodium source, and then performing spray drying and secondary calcination, and finally preparing the sodium iron phosphate positive electrode material by using a solid-phase ball milling spray drying method, so that the sodium iron phosphate power battery with excellent kinetic performance can be quickly prepared, the battery has high capacity and good rate performance, and has good cycle stability, low production cost, excellent cycle performance and low-temperature performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a preparation method of a power-type sodium iron phosphate pyrophosphate positive electrode material. BACKGROUND

[0002] Energy crisis and environmental change lead to that sustainable development and storage of energy are highly valued by countries around the world. Although lithium ion batteries have been widely used in small portable electronics, electric vehicles (EV) or plug-in hybrid electric vehicles (PHEV), but high cost and limited lithium storage limit its further development. Sodium ion batteries are considered an ideal large-scale power storage application technology because of abundant sodium resources and environmental friendliness, so in recent years, sodium ion batteries have become a hot research issue, and various sodium storage materials have been widely studied.

[0003] The development of the new energy industry makes the market of electric two-wheelers begin to be concerned. However, unlike the batteries of electric vehicles, the batteries of electric two-wheelers are more likely to be exposed to the outdoors for a long time, and higher requirements are put forward for the safety and cost of the batteries. Compared with lithium ion batteries, sodium ion batteries not only have lower raw material prices, but also have better safety because the gas generated by sodium ions at high temperatures is not flammable, so sodium ion batteries are expected to become the next generation of power sources for electric two-wheelers. SUMMARY

[0004] In view of the above problems existing in the prior art, the preparation method of the power-type sodium iron phosphate pyrophosphate positive electrode material provided by the application is used to overcome the above defects in the prior art.

[0005] To achieve the above-mentioned purposes, the technical solutions adopted by the application are as follows:

[0006] A preparation method of a power-type sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps:

[0007] Firstly, a sodium source, an iron source and a phosphorus source are added into a ball mill according to a ratio of 4: (2.9-3): 4, zirconium balls are prepared according to a ball-to-material ratio of 1:20, a ball milling medium solvent is added according to a ratio of 2-4 kg / L, and then a first carbon source is added according to 2-4% of the mass of the sodium source and the iron source, the slurry is ball milled to a particle size of 2-4 um, and spray drying is performed to obtain a first spray material;

[0008] Secondly, a roller furnace is used to pre-burn the first spray material obtained in the first step in an inert gas environment, and then the pre-burned material is air-jet pulverized and vibrated to pass through a 80-120 mesh sieve to obtain a NFPP pre-burned material;

[0009] Third step, the NFPP pre-burning material prepared in the second step is added into a ball mill, then 1.5-3% of the mass of the NFPP pre-burning material is added as the second carbon source and 0.5-1.5% of the mass of the NFPP pre-burning material is added as the additive, zirconium balls are prepared with a ball-to-material ratio of 1:20, an appropriate amount of ball milling medium solvent is added at a ratio of 5-7 kg / L, the slurry is ball milled to a particle size of 1-2 μm, and the second spray material is obtained by spray drying;

[0010] Fourth step, the second spray material obtained in the third step is calcined in an inert gas atmosphere using a roller furnace to obtain a power-type sodium iron phosphate pyrophosphate positive electrode material.

[0011] In one of the embodiments, the sodium source is one or more of sodium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium acetate, and sodium pyrophosphate;

[0012] The iron source is one or more of ferrous oxalate, iron phosphate, ferrous acetate, ferrous sulfate, and ferrous nitrate,

[0013] The phosphorus source is one or more of ammonium phosphate, ammonium dihydrogen phosphate, and ammonium hydrogen phosphate.

[0014] In one of the embodiments, the first carbon source is one or more of glucose, sucrose, citric acid, ascorbic acid, and polyethylene glycol 400-800;

[0015] The second carbon source is one or more of glucose, sucrose, citric acid, ascorbic acid, and polyethylene glycol 800-4000.

[0016] In one of the embodiments, the additive is one of ethylene glycol, stearic acid, oleic acid, fatty alcohol sulfate sodium, and carboxybetaine.

[0017] In one of the embodiments, the pre-burning operation has a temperature rising rate of 10-20 ℃ / min, a pre-burning temperature of 450-500 ℃, a high-temperature zone time of 3-6 h, and a temperature falling rate of 5-10 ℃ / min in the falling temperature zone.

[0018] In one of the embodiments, the calcination operation has a temperature rising rate of 5-10 ℃ / min, a temperature rising to 400-450 ℃ for 2 h, and a temperature rising to 500-580 ℃ for 10-12 h.

[0019] In one of the embodiments, the spray drying operation in the first step has a spray rotation speed of 10,000-12,000 rpm and a temperature of 80-90 ℃;

[0020] The spray drying operation in the third step has a spray rotation speed of 9,000-11,000 rpm and a temperature of 85-100 ℃.

[0021] In one of the embodiments, the mass of the first carbon source in the first step is 2%, the mass of the second carbon source in the third step is 1.5%, and the mass of the additive is 0.5%.

[0022] In one of the embodiments, the ball milling medium is one of methanol, ethanol or water.

[0023] Compared with the prior art, the preparation method of the power-type sodium iron phosphate positive electrode material provided by the application can quickly prepare a sodium iron phosphate power battery with excellent kinetic performance by using ferrous oxalate in combination with a composite iron source and a sodium source, through spray drying, secondary calcination, and preparation of the sodium iron phosphate positive electrode material by a solid-phase ball milling spray drying method. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The particle size peak type comparison chart of Example 1 and the comparative example provided by the application is shown in the following figure. DETAILED DESCRIPTION

[0025] The application will be further described in detail below in combination with the drawings and embodiments:

[0026] Example 1

[0027] (1) Sodium carbonate, ferrous nitrate and ammonium phosphate are added into a ball mill according to the ratio of Na:Fe:P = 4:2.95:4, zirconium balls are prepared according to the ball-to-material ratio of 1:20, anhydrous ethanol is added according to the ratio of 3 kg / L, glucose is added according to 2% of the mass of the sodium source and the iron source, the slurry is ball milled for a certain time to make the particle size of the slurry reach 2-4 μm, and first spray material is obtained by spray drying, wherein the spray rotation speed of the spray drying operation is between 10,000 and 12,000 rpm, and the temperature is between 80 and 90℃;

[0028] (2) The first spray material obtained in (1) is pre-fired using a roller furnace in an argon atmosphere, the heating rate is 10℃ / min, the temperature is 450℃, and after holding at the high-temperature zone for 3h, the material is cooled in the cooling zone, the cooling rate is controlled to make the material cooling rate in the range of 5-10℃ / min, then the pre-fired material is air-jet pulverized, and NFPP pre-fired material is obtained by vibrating and sieving to 100 mesh;

[0029] (3) Add the NFPP pre-calcined material prepared in (2) to a ball mill, then add polyethylene glycol 1000 at 1.5% of the mass of the NFPP pre-calcined material and stearic acid at 0.5% of the mass of the NFPP pre-calcined material, add zirconium balls at a ball-to-material ratio of 1:20, add anhydrous ethanol at a ratio of 5 kg / L, and mill the slurry to a particle size of 1-2 μm. Spray dry to obtain a second spray material. The spray speed of the spray drying operation is between 9000 and 11000 rpm and the temperature is between 85 and 100℃. Then calcine the second spray material under an argon atmosphere, raise the temperature to 450℃ at a rate of 10℃ / min and hold for 2 hours, then raise the temperature to 550℃ and hold for 10 hours to obtain a power-type sodium iron pyrophosphate cathode material.

[0030] Example 2

[0031] (1) Sodium dihydrogen phosphate, ferrous oxalate, and sodium carbonate were added to a ball mill in the ratio of Na:Fe:P = 4:2.95:4. Zirconium balls were prepared at a ball-to-material ratio of 1:20. Anhydrous ethanol was added at a ratio of 3 kg / L. Glucose was added at 2% of the mass of sodium and iron sources. The ball milling was carried out for a certain period of time to make the slurry particle size reach 2-4 μm. The first spray material was obtained by spray drying. The spray speed of the spray drying operation was between 10,000 and 12,000 rpm and the temperature was between 80 and 90℃.

[0032] (2) The first spray material obtained in (1) is pre-burned in a roller furnace under an argon atmosphere. The heating rate is 10℃ / min and the temperature is 450℃. After being kept in the high temperature zone for 3 hours, it enters the cooling zone. The cooling rate of the cooling zone is controlled so that the material cooling rate is in the range of 5 to 10℃ / min. Then the pre-burned material is air-jet crushed and vibrated through a 100-mesh sieve to obtain NFPP pre-burned material.

[0033] (3) The NFPP pre-calcined material prepared in (2) is added to a ball mill. Then, polyethylene glycol 1000 is added at 1.5% of the mass of the NFPP pre-calcined material and stearic acid is added at 0.5% of the mass of the NFPP pre-calcined material. Zirconium balls are prepared at a ball-to-material ratio of 1:20, and anhydrous ethanol is added at a ratio of 5 kg / L. The ball milling slurry particle size is reduced to 1-2 μm, and the second spray material is obtained by spray drying. The spraying speed of this spray drying operation is between 9000 and 11000 rpm, and the temperature is between 85 and 100℃. The second spray material is then calcined in an argon atmosphere, heated to 450℃ at a rate of 10℃ / min and held for 2 hours, and then heated to 550℃ and held for 10 hours to obtain a power-type sodium iron pyrophosphate cathode material.

[0034] Example 3

[0035] (1) Sodium carbonate, iron phosphate, sodium pyrophosphate and ammonium phosphate are added to a ball mill in the ratio of Na:Fe:P = 4:2.95:4. Zirconium balls are prepared at a ball-to-material ratio of 1:20. Anhydrous ethanol is added at a ratio of 3 kg / L. Glucose is added at 2% of the mass of sodium source and iron source. The ball mill is milled for a certain time to make the slurry particle size reach 2-4 μm. The first spray material is obtained by spray drying. The spray speed of the spray drying operation is between 10,000 and 12,000 rpm and the temperature is between 80 and 90℃.

[0036] (2) The first spray material obtained in (1) is pre-burned in a roller furnace under an argon atmosphere. The heating rate is 10℃ / min and the temperature is 450℃. After being kept in the high temperature zone for 3 hours, it enters the cooling zone. The cooling rate of the cooling zone is controlled so that the material cooling rate is in the range of 5 to 10℃ / min. Then the pre-burned material is air-jet crushed and vibrated through a 100-mesh sieve to obtain NFPP pre-burned material.

[0037] (3) The NFPP pre-calcined material prepared in (2) is added to a ball mill. Then, polyethylene glycol 1000 is added at 1.5% of the mass of the NFPP pre-calcined material and stearic acid is added at 0.5% of the mass of the NFPP pre-calcined material. Zirconium balls are prepared at a ball-to-material ratio of 1:20, and anhydrous ethanol is added at a ratio of 5 kg / L. The ball milling slurry particle size is reduced to 1-2 μm, and the second spray material is obtained by spray drying. The spraying speed of this spray drying operation is between 9000 and 11000 rpm, and the temperature is between 85 and 100℃. The second spray material is then calcined in an argon atmosphere, heated to 450℃ at a rate of 10℃ / min and held for 2 hours, and then heated to 550℃ and held for 10 hours to obtain a power-type sodium iron pyrophosphate cathode material.

[0038] Comparative Example 1:

[0039] (1) Sodium dihydrogen phosphate, ferrous oxalate, and sodium carbonate were added to a ball mill in the ratio of Na:Fe:P = 4:2.95:4. Zirconium balls were prepared at a ball-to-material ratio of 1:20. Anhydrous ethanol was added at a ratio of 3 kg / L. Glucose was added at 2% of the mass of sodium and iron sources. The ball milling was carried out for a certain period of time to make the slurry particle size reach 2-4 μm. The first spray material was obtained by spray drying. The spray speed of the spray drying operation was between 10,000 and 12,000 rpm and the temperature was between 80 and 90℃.

[0040] (2) The first spray material obtained in (1) is pre-burned in a roller furnace under an argon atmosphere. The heating rate is 10℃ / min and the temperature is 450℃. After being kept in the high temperature zone for 3 hours, it enters the cooling zone. The cooling rate of the cooling zone is controlled so that the material cooling rate is in the range of 5 to 10℃ / min. Then the pre-burned material is air-jet crushed and vibrated through a 100-mesh sieve to obtain NFPP pre-burned material.

[0041] (3) Add the NFPP pre-calcined material prepared in (2) to a ball mill, directly prepare zirconium balls at a ball-to-material ratio of 1:20, add anhydrous ethanol at a ratio of 5 kg / L, mill the slurry to a particle size of 1-2 μm, and spray dry to obtain a second spray material. The spray drying operation is between 9000 and 11000 rpm and between 85 and 100℃. Then calcine the second spray material in an argon atmosphere, raise the temperature to 450℃ at a rate of 10℃ / min and hold for 2 hours, then raise the temperature to 550℃ and hold for 10 hours to obtain a power-type sodium iron pyrophosphate cathode material.

[0042] Button cell testing: The prepared sodium iron pyrophosphate, SP, and PVDF were mixed and ground evenly in a ratio of 9:0.5:0.5. A certain amount of NMP was added, and after stirring and forming a slurry, it was coated and dried. 2032 coin cells were prepared using a GF separator and NaClO4 electrolyte. The charge-discharge capacity at 0.1-0.5-1C was tested in the 2-4V range. The results are shown in the table below:

[0043]

[0044] As can be seen from the electrical performance comparison in the table above, the preparation method provided by this invention, which produces a sodium iron pyrophosphate cathode material with a composite carbon-coated structure through two-step calcination, exhibits high rate performance. The selection of the main sodium / iron / phosphorus source has a certain impact on performance. Comparative Example 1 demonstrates that during ball milling of NFPP pre-calcined material, the absence of additional carbon source and additives leads to a significant decrease in electrical performance. Figure 1 As can be seen from the particle size peak diagram, the particle size of Comparative Example 1 without additives is much larger than that of Example 1, even after ball milling for 2 hours.

[0045] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a power-type sodium iron pyrophosphate cathode material, characterized in that, Includes the following steps: The first step involves adding sodium, iron, and phosphorus sources to a ball mill in a ratio of 4:(2.9–3):4, preparing zirconium balls at a ball-to-material ratio of 1:20, adding ball milling media solvent at a ratio of 2–4 kg / L, and then adding the first carbon source at 2–4% of the mass of sodium and iron sources. The ball milling operation is performed to reduce the slurry particle size to 2–4 μm, followed by spray drying to obtain the first spray material. The second step involves pre-firing the first spray material obtained in the first step using a roller furnace in an inert gas environment. Then, the pre-firing material is subjected to air jet pulverization and vibrated through a sieve of 80-120 mesh to obtain NFPP pre-fired material. The third step involves adding the NFPP pre-calcined material prepared in the second step to a ball mill, then adding a second carbon source at 1.5-3% of the mass of the NFPP pre-calcined material and an additive at 0.5-1.5% of the mass of the NFPP pre-calcined material, adding zirconium balls at a ball-to-material ratio of 1:20, adding an appropriate amount of ball milling media solvent at a ratio of 5-7 kg / L, milling the slurry to a particle size of 1-2 μm, and spray drying to obtain the second spray material. The fourth step involves calcining the second spray material obtained in the third step in an inert gas atmosphere using a roller furnace to obtain a power-type sodium iron pyrophosphate cathode material. The additive is one of ethylene glycol, stearic acid, oleic acid, sodium fatty alcohol sulfate, and carboxybetaine; The pre-firing temperature is 450-500℃, and the high-temperature zone time is 3-6 hours; The calcination process involves heating to 400–450°C and holding for 2 hours, then heating to 500–580°C and holding for 10–12 hours.

2. The preparation method of the power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The sodium source is one or more of sodium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium acetate, and sodium pyrophosphate. The iron source is one or more of ferrous oxalate, ferric phosphate, ferrous acetate, ferrous sulfate, and ferrous nitrate. The phosphorus source is one or more of ammonium phosphate, ammonium dihydrogen phosphate, and ammonium hydrogen phosphate.

3. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The first carbon source is one or more of glucose, sucrose, citric acid, ascorbic acid, and polyethylene glycol 400-800; The second carbon source is one or more of glucose, sucrose, citric acid, ascorbic acid, and polyethylene glycol 800-4000.

4. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The heating rate of the pre-firing process is 10-20℃ / min, and the cooling rate of the cooling zone is 5-10℃ / min.

5. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The calcination process involves heating at a rate of 5–10 °C / min.

6. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The spray speed in the first step of the spray drying operation is between 10,000 and 12,000 rpm, and the temperature is between 80 and 90°C. The spray speed in the third step of the spray drying operation is between 9000 and 11000 rpm, and the temperature is between 85 and 100°C.

7. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The mass of the first carbon source in the first step is 2%, the mass of the second carbon source in the third step is 1.5%, and the mass of the additive is 0.5%.

8. The method for preparing a power-type sodium iron pyrophosphate cathode material as described in claim 1, characterized in that, The ball milling media is one of methanol, ethanol, or water.

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