Manufacturing method and application of positive electrode material for sodium ion batteries

Abstract

An embodiment of the present invention provides a method for manufacturing a positive electrode material for a sodium ion battery, the method comprising the steps of: dispersing a sodium source compound, iron hydrogen phosphate hydrate, and a carbon source compound in water in a certain ratio and stirring the mixture to obtain a dispersion; placing the dispersion in a sand mill and sand-milling it for a certain period of time to obtain a paste; drying the sand-milled paste to obtain a powdered precursor; and sintering and grinding the powdered precursor to obtain a positive electrode material for a sodium ion battery. The positive electrode material for a sodium ion battery manufactured by the manufacturing method of the present invention has a high crystalline phase purity, a high compaction density, and a high energy density. Sodium ion batteries manufactured using the positive electrode material for a sodium ion battery of the present invention have excellent battery cycle performance and stability. Furthermore, the manufacturing method is simple and suitable for large-scale industrial production.

Description

[Technical Field]

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to the manufacturing method and application of positive electrode materials for sodium ion batteries. [Background technology]

[0002] As the current representative of the most comprehensive secondary battery, the commercialization of lithium-ion batteries dates back to the 1990s. After many years of research, lithium-ion batteries have developed into a mature battery technology roadmap. However, due to the limited abundance of lithium in the earth's crust, lithium-ion batteries have difficulty supporting the currently growing energy storage market. The operating principle of sodium-ion batteries is similar to that of lithium-ion batteries, but sodium salts are abundant and easy to mine, making them more advantageous for subsequent large-scale application in the energy storage field.

[0003] Sodium-ion batteries are primarily composed of a positive electrode, a negative electrode, an electrolyte, a separator, and auxiliary components. The positive and negative electrode materials are key to the performance of a sodium-ion battery system, with the positive electrode being particularly important. Positive electrode materials for sodium-ion batteries are classified into three categories: transition metal oxides, Prussian white / blue, and polyanions. Polyanionic positive electrode materials for sodium-ion batteries have the advantages of structural stability and small volumetric change during charge and discharge. Among polyanionic positive electrode materials for sodium-ion batteries, iron-based sodium batteries have the advantages of low cost and non-toxicity. Among these, sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2P2O7) is the most promising positive electrode material for iron-based sodium batteries, boasting low cost, environmental friendliness, high theoretical capacity (129 mAh / g), excellent cycling characteristics, and low volumetric expansion (approximately 4%).

[0004] Currently, the high-temperature solid-state method using the grinding-spraying-sintering process is the most effective method for producing positive electrode materials for secondary batteries. However, when using this process to produce sodium iron phosphate pyrophosphate, the raw materials used are unevenly mixed at the microscopic level due to the influence of the processing steps, resulting in the generation of impurities such as sodium iron phosphate and sodium iron pyrophosphate, which reduces the purity of the crystalline phase of the produced positive electrode material. This drawback seriously limits the subsequent application of this sodium iron phosphate pyrophosphate positive electrode material. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above, the present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention provides a manufacturing method and application of a positive electrode material for a sodium ion battery. The positive electrode material for a sodium ion battery manufactured by the manufacturing method of the present invention has a high crystalline phase purity, and a higher compaction density and energy density. In addition, the manufacturing method is simple and suitable for application in large-scale industrial production. [Means for solving the problem]

[0006] Therefore, in a first aspect, according to an embodiment of the present invention, there is provided a method for producing a cathode material for a sodium ion battery, the method including the steps of: dispersing a sodium source compound, iron hydrogen phosphate hydrate, and a carbon source compound in water at a certain ratio, stirring and mixing them to obtain a dispersion; placing the dispersion in a sand mill and sand-milling it for a certain period of time to obtain a paste; drying the paste after sand-milling to obtain a powdery precursor; and sintering and pulverizing the powdery precursor to obtain the cathode material for a sodium ion battery.

[0007] Preferably, the sodium source compound in the dispersion and the iron hydrogen phosphate hydrate are added in a molar ratio of n(Na):n(Fe)=4:3.

[0008] Preferably, the sodium source compound is one or more of sodium formate, sodium acetate, sodium citrate, sodium oxalate, sodium chloride, sodium nitrate, and sodium sulfate.

[0009] Preferably, the addition amount of the carbon source compound is 10 wt% to 55 wt% of the addition amount of the iron hydrogen phosphate hydrate.

[0010] Preferably, the carbon source compound is one or more of vaseline, stearic acid, sucrose, ascorbic acid, formaldehyde, acetaldehyde, n-butyl aldehyde, lactic acid, citric acid, malic acid, ethanedioic acid, adipic acid, soluble starch, glucose, polyethylene glycol, maltose, cyclodextrin, carbon nanotube, acetylene black, and graphene.

[0011] Preferably, the sand milling method of the sand mill includes one of the disk type, pin type, and turbine type, and controls the particle size of the paste after sand milling to be 0.1 μm < DN50 < 5 μm.

[0012] Preferably, the drying method may be one or more of blowing drying, vacuum drying, freeze drying, and spray drying.

[0013] Preferably, the sintering conditions include a sintering atmosphere, a sintering temperature, and a sintering time. The sintering atmosphere includes a mixed atmosphere of one or more of nitrogen gas, argon gas, and helium gas. The sintering temperature is 450 to 700 °C, the heating rate is 1 to 3 °C / min, and the sintering time is 6 to 24 h.

[0014] Preferably, the pulverization method may be one or two of mechanical pulverization and airflow pulverization.

[0015] In a second aspect, according to an embodiment of the present invention, a sodium ion battery including the positive electrode material for a sodium ion battery according to the first aspect is provided.

[0016] The manufacturing method of a sodium-ion battery positive electrode material according to an embodiment of the present invention uses hydrated iron hydrogen phosphate (Fe3(HPO4)4·H2O), a raw material with a constant iron-phosphorus ratio, as a precursor during the manufacturing process, thereby eliminating the micro-level influence of the processing on the design of the raw material blend ratio and ensuring the uniformity of the raw materials. The manufactured sodium-ion battery positive electrode material has high crystalline phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Furthermore, the manufacturing method is simple and suitable for application in large-scale industrial production. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flowchart of a method for manufacturing a positive electrode material for a sodium ion battery according to an embodiment of the present invention. [Figure 2] FIG. 1 is an SEM image of a positive electrode material for a sodium ion battery manufactured in Example 1 of the present invention. [Figure 3] FIG. 1 is an XRD diagram of a positive electrode material for a sodium ion battery prepared in Example 1 of the present invention. [Figure 4] FIG. 2 is a diagram showing the initial charge / discharge curves at 0.1 C of a button-type half cell assembled with the positive electrode material for a sodium ion battery prepared in Example 1 of the present invention. [Figure 5] FIG. 2 is an XRD diagram of the positive electrode material for a sodium ion battery prepared in Example 2 of the present invention. [Figure 6] FIG. 2 is a diagram showing the initial charge / discharge curves at 0.1 C of a button-type half cell assembled with the positive electrode material for a sodium ion battery prepared in Example 2 of the present invention. [Figure 7] FIG. 2 is an XRD diagram of the positive electrode material for a sodium ion battery prepared in Example 3 of the present invention. [Figure 8] FIG. 2 is a diagram showing the initial charge / discharge curve at 0.1 C of a button-type half cell assembled with the positive electrode material for a sodium ion battery prepared in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the embodiments of the present invention will be described in detail, and examples of the embodiments are shown in the drawings, and the same or similar reference numerals indicate the same or similar parts or parts having the same or similar functions throughout. The embodiments described below with reference to the drawings are illustrative and are intended to interpret the present invention, but should not be understood as limiting the present invention.

[0019] The following disclosure provides many different embodiments or examples for realizing different structures of the present invention. To simplify the disclosure of the present invention, specific example components and arrangements are described below. It should be understood that these are merely exemplary and are not intended to limit the present invention. Furthermore, the present invention may use repeated reference numerals and / or alphabetical references in different examples. Such repetition is for the purposes of brevity and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Furthermore, while the present invention provides examples of various specific processes and materials, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0020] The present invention provides a method for producing a sodium-ion battery cathode material with high crystalline phase purity, high compaction density, and high energy density, and its application. The sodium-ion battery cathode material of the present invention is sodium iron phosphate pyrophosphate, with the chemical formula Na4Fe3(PO4)2P2O7. Sodium-ion batteries manufactured using the sodium-ion battery cathode material of the present invention have excellent battery cycle performance and stability.

[0021] As shown in FIG. 1, an embodiment of the first aspect of the present invention provides a method for producing a positive electrode material for a sodium ion battery, including the following steps S1 to S4.

[0022] In step S1, a sodium source compound, iron hydrogen phosphate hydrate, and a carbon source compound are dispersed in water at a certain ratio and mixed with stirring to obtain a dispersion.

[0023] In an embodiment of the present invention, the chemical formula of the iron hydrogen phosphate hydrate is Fe3(HPO4)4·H2O, and the sodium source compound in the dispersion liquid and the iron hydrogen phosphate hydrate are added at a molar ratio of n(Na):n(Fe)=4:3.

[0024] The sodium source compound may be one or more of sodium formate, sodium acetate, sodium citrate, sodium oxalate, sodium chloride, sodium nitrate, and sodium sulfate.

[0025] The addition amount of the carbon source compound is 10wt% - 55wt% of the addition amount of the iron hydrogen phosphate hydrate. The carbon source compound may be one or more of vaseline, stearic acid, sucrose, ascorbic acid, formaldehyde, acetaldehyde, n-butylaldehyde, lactic acid, citric acid, malic acid, ethanedioic acid, adipic acid, soluble starch, glucose, polyethylene glycol, maltose, cyclodextrin, carbon nanotube, acetylene black, and graphene.

[0026] In step S2, the dispersion liquid is put into a sand mill and sand milled for a certain period of time to obtain a paste.

[0027] The sand milling method of the sand mill includes one of disk type, pin type, and turbine type. The particle size of the paste after sand milling is controlled to be 0.1μm < DN50 < 5μm.

[0028] In step S3, the paste after sand milling is dried to obtain a powdery precursor.

[0029] The drying method may be one or more of blowing drying, vacuum drying, freeze drying, and spray drying.

[0030] In step S4, the powdery precursor is sintered and pulverized to obtain a cathode material for a sodium ion battery.

[0031] The sintering conditions include a sintering atmosphere, a sintering temperature, and a sintering time. The sintering atmosphere may include a mixed atmosphere of one or more of nitrogen gas, argon gas, and helium gas. The sintering temperature may be 450 to 700°C, and the temperature rise rate may be 1 to 3°C / min. The sintering time may be 6 to 24 hours. The pulverization method may be one or both of mechanical pulverization and airflow pulverization.

[0032] The manufacturing method of the sodium-ion battery positive electrode material according to the embodiment of the present invention uses hydrated iron hydrogen phosphate (Fe3(HPO4)4·H2O), a raw material with a consistent iron-phosphorus ratio, as a precursor during the manufacturing process. This eliminates the microscopic influence of the processing on the design of the raw material blend ratio, ensuring raw material uniformity. The manufactured sodium-ion battery positive electrode material has a high crystalline phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Sodium-ion batteries manufactured based on the sodium-ion battery positive electrode material according to the present invention have excellent battery cycle performance and stability. Furthermore, the manufacturing method is simple and suitable for large-scale industrial production.

[0033] Hereinafter, the specific steps and effects of the method for preparing a positive electrode material for a sodium ion battery of the present invention will be described in more detail with reference to some specific examples, but the scope of protection of the present invention is not limited thereto.

[0034] Example 1 This example provides a method for preparing a positive electrode material for a sodium ion battery. The positive electrode material for a sodium ion battery prepared in this example is Na4Fe3(PO4)2P2O7, and includes the following steps:

[0035] One mole of iron hydrogen phosphate hydrate and 4 moles of sodium nitrate were weighed and dispersed in deionized water. Glucose equivalent to 20% by mass of the iron hydrogen phosphate hydrate was weighed and added to the deionized water, followed by stirring and mixing to obtain a dispersion. The dispersion was then sand-milled, and when the particle size of the solid particles in the dispersion reached DN50 = 0.2 μm, polishing was stopped to obtain a paste. The polished paste was then spray-dried to obtain a powdered precursor. The obtained powdered precursor was heated to 500 °C at 2 °C / min under a nitrogen gas atmosphere, held at that temperature for 18 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0036] FIG. 2 is an SEM image of Na4Fe3(PO4)2P2O7, the positive electrode material produced in this example.

[0037] FIG. 3 is an XRD diagram of Na4Fe3(PO4)2P2O7, the positive electrode material produced in this example.

[0038] The cathode material prepared in this example, Na4Fe3(PO4)2P2O7, acetylene black, and PVDF, were added to an appropriate amount of NMP in a mass ratio of 70:20:10 and mixed uniformly. The black paste was then applied to aluminum foil using a 150 μm four-sided film applicator. The film was then vacuum-dried at 110°C for 6 hours. The dried electrode film was then punched into thin pieces of the same radius using a punching machine to obtain a cathode sheet. Metallic sodium was used as the anode sheet, a glass fiber membrane was used as the separator, and NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 volume ratio) was used as the electrolyte. Button-type half-cells were assembled in a glove box with a dissolved oxygen concentration of less than 0.01 ppm. The test results are shown in FIG. 4. When the current density was 0.1 C and the voltage range was 2.0 to 4.0 V, the discharge capacity reached 109.7 mAh / g.

[0039] Example 2 This example provides a method for preparing a positive electrode material for a sodium ion battery. The positive electrode material for a sodium ion battery prepared in this example is Na4Fe3(PO4)2P2O7, and includes the following steps:

[0040] One mole of iron hydrogen phosphate hydrate and 4 moles of sodium chloride were weighed and dispersed in deionized water. Glucose, equivalent to 30% by mass of the iron hydrogen phosphate hydrate, was weighed and added to the deionized water and stirred to obtain a dispersion. The dispersion was then sand-milled, and when the particle size of the solid particles in the dispersion reached DN50 = 3.0 μm, polishing was stopped to obtain a paste. The polished paste was then spray-dried to obtain a powdered precursor. The obtained powdered precursor was heated to 550 °C at a rate of 2 °C / min under a nitrogen gas atmosphere, held at that temperature for 16 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0041] FIG. 5 is an XRD diagram of Na4Fe3(PO4)2P2O7, the positive electrode material produced in this example.

[0042] The cathode material prepared in this example, Na4Fe3(PO4)2P2O7, acetylene black, and PVDF, were added to an appropriate amount of NMP in a mass ratio of 70:20:10 and mixed uniformly. The black paste was then applied to aluminum foil using a 150 μm four-sided film applicator. The film was then vacuum-dried at 110°C for 6 hours. The dried electrode film was then punched into thin pieces of the same radius using a punching machine to obtain a cathode sheet. Metallic sodium was used as the anode sheet, a glass fiber membrane was used as the separator, and NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 volume ratio) was used as the electrolyte. Button-type half-cells were assembled in a glove box with a dissolved oxygen concentration of less than 0.01 ppm. The test results are shown in FIG. 6. When the current density was 0.1 C and the voltage range was 2.0 to 4.0 V, the discharge capacity reached 112.9 mAh / g.

[0043] Example 3 This example provides a method for preparing a positive electrode material for a sodium ion battery. The positive electrode material for a sodium ion battery prepared in this example is Na4Fe3(PO4)2P2O7, and includes the following steps:

[0044] One mole of iron hydrogen phosphate hydrate and 4 moles of sodium acetate were weighed and dispersed in deionized water. Glucose, equivalent to 25% by mass of the iron hydrogen phosphate hydrate, was weighed and added to the deionized water and stirred to obtain a dispersion. The dispersion was then sand-milled, and when the particle size of the solid particles in the dispersion reached DN50 = 4.6 μm, polishing was stopped to obtain a paste. The polished paste was then spray-dried to obtain a powdered precursor. The obtained powdered precursor was heated to 600 °C at a rate of 5 °C / min under a nitrogen gas atmosphere, held at that temperature for 12 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0045] FIG. 7 is an XRD diagram of Na4Fe3(PO4)2P2O7, the positive electrode material produced in this example.

[0046] The cathode material prepared in this example, Na4Fe3(PO4)2P2O7, acetylene black, and PVDF, were added to an appropriate amount of NMP in a mass ratio of 70:20:10 and mixed uniformly. The black paste was then applied to aluminum foil using a 150 μm four-sided film applicator. The film was then vacuum-dried at 110°C for 6 hours. The dried electrode film was then punched into thin pieces of the same radius using a punching machine to obtain a cathode sheet. Metallic sodium was used as the anode sheet, a glass fiber membrane was used as the separator, and NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 volume ratio) was used as the electrolyte. Button-type half-cells were assembled in a glove box with a dissolved oxygen concentration of less than 0.01 ppm. The test results are shown in FIG. 8. When the current density was 0.1 C and the voltage range was 2.0 to 4.0 V, the discharge capacity reached 110.5 mAh / g.

[0047] An embodiment of the second aspect of the present invention provides a sodium ion battery including a positive electrode material for a sodium ion battery manufactured by the manufacturing method according to the embodiment of the first aspect.

[0048] As described above, the manufacturing method and application of the sodium-ion battery positive electrode material according to the embodiment of the present invention uses hydrated iron hydrogen phosphate (Fe3(HPO4)4·H2O), a raw material with a consistent iron-phosphorus ratio, as a precursor during the manufacturing process. This eliminates the microscopic influence of the processing on the design of the raw material blend ratio, ensuring raw material uniformity. The manufactured sodium-ion battery positive electrode material has a high crystalline phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Sodium-ion batteries manufactured based on the sodium-ion battery positive electrode material according to the present invention have excellent battery cycle performance and stability. Furthermore, the manufacturing method is simple and suitable for large-scale industrial production.

[0049] In the description herein, references to the terms "one embodiment," "some embodiments," "examples," "specific examples," "some examples," etc., mean that the specific features, structures, materials, or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In the description herein, the exemplary expressions of the above terms are not necessarily limited to the same embodiment or example. Furthermore, the described specific features, structures, materials, or characteristics may be appropriately combined in any one or more embodiments or examples. Furthermore, if not mutually inconsistent, a person skilled in the art may combine or combine different embodiments or examples and features of different embodiments or examples described herein.

[0050] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is limited by the claims and their equivalents.

Claims

1. a step of dispersing a sodium source compound, iron hydrogen phosphate hydrate, and a carbon source compound in water at a predetermined ratio and stirring and mixing the mixture to obtain a dispersion; Putting the dispersion into a sand mill and milling it for a certain period of time to obtain a paste; drying the paste after sand milling to obtain a powder precursor; and sintering and grinding the powder precursor to obtain a positive electrode material for a sodium ion battery. A method for producing a positive electrode material for a sodium ion battery, comprising:

2. The sodium source compound in the dispersion and the iron hydrogen phosphate hydrate are added in a molar ratio of n(Na):n(Fe)=4:

3. The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

3. the sodium source compound is one or more of sodium formate, sodium acetate, sodium citrate, sodium oxalate, sodium chloride, sodium nitrate, and sodium sulfate; The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

4. the amount of the carbon source compound added is 10 wt % to 55 wt % of the amount of the iron hydrogen phosphate hydrate added; The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

5. the carbon source compound is one or more of petrolatum, stearic acid, sucrose, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, ethanedioic acid, adipic acid, soluble starch, glucose, polyethylene glycol, maltose, cyclodextrin, carbon nanotubes, acetylene black, and graphene; The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

6. The sand milling method of the sand mill includes one of a disk type, a pin type, and a turbine type, and the particle size of the paste after sand milling is controlled to 0.1 μm<DN50<5 μm. The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

7. The drying method may be one or more of blow drying, vacuum drying, freeze drying, and spray drying. The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

8. The sintering conditions include a sintering atmosphere, a sintering temperature, and a sintering time, the sintering atmosphere including one or a mixed atmosphere of nitrogen gas, argon gas, and helium gas, the sintering temperature being 450 to 700°C, the temperature rise rate being 1 to 3°C / min, and the sintering time being 6 to 24 hours. The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

9. The pulverization method may be one or two of mechanical pulverization and airflow pulverization. The method for producing a positive electrode material for a sodium ion battery according to claim 1 .

10. The positive electrode material for a sodium ion battery manufactured by the manufacturing method according to any one of claims 1 to 9, A sodium-ion battery characterized by:

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