Method for manufacturing 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 particularly to a method for manufacturing and an application of a cathode material for sodium-ion batteries.

Background Art

[0002] As a representative of secondary batteries with the best overall performance at present, the commercialization of lithium-ion batteries can be traced back to the 1990s. Through years of research, lithium-ion batteries have developed into a mature battery technology roadmap. However, due to the limitation of the crust abundance of lithium elements, it is difficult for lithium-ion batteries to support the currently growing energy storage market. The operating principle of sodium-ion batteries is similar to that of lithium-ion batteries, and the storage amount of sodium salts is abundant, the mining is simple, and it is more advantageous in large-scale applications in the subsequent energy storage field.

[0003] Sodium-ion batteries are mainly composed of a cathode, an anode, an electrolyte, a separator and accessory members. The positive and negative electrode materials are the key factors affecting the performance of the sodium-ion battery system, and the cathode material is particularly prominent. The cathode materials for sodium-ion batteries are classified into three types: transition metal oxides, Prussian white / blue and polyanions. Among them, the cathode material for polyanionic sodium-ion batteries has the advantages of stable structure and small volume change during charge and discharge. Among the cathode materials for polyanionic sodium-ion batteries, iron-based sodium batteries have the advantages of the lowest cost and no toxicity. Among them, sodium pyrophosphate iron phosphate (Na4Fe3(PO4)2P2O7) has the highest possibility as a cathode material for iron-based sodium batteries, with low cost, environmental friendliness, high theoretical capacity (129 mAh / g), excellent cycle characteristics, and low volume expansion (about 4%).

[0004] Currently, the high-temperature solid-phase method using the polishing-spray-sintering process route is the most effective manufacturing method for cathode materials for secondary batteries. However, due to the effects of the processing, when sodium iron pyrophosphate is produced using this process route, the raw materials used are mixed non-uniformly at the micro level, resulting in the generation of impurities such as sodium iron phosphate and sodium iron pyrophosphate. This leads to low purity of the crystalline phase of the produced cathode material, and the aforementioned drawbacks seriously limit the subsequent applications of this sodium iron pyrophosphate cathode material. [Overview of the Initiative] [Problems that the invention aims to solve]

[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 method for manufacturing a positive electrode material for sodium-ion batteries and its applications. The positive electrode material for sodium-ion batteries manufactured by the manufacturing method of the present invention has high purity of the crystalline phase and higher compaction density and energy density. Furthermore, the manufacturing method is simple and suitable for application in large-scale industrial production. [Means for solving the problem]

[0006] Therefore, in the first embodiment, according to an example of the present invention, a method for producing a positive electrode material for a sodium-ion battery is provided, comprising the steps of: dispersing a sodium source compound, iron hydrogen phosphate hydrate, and a carbon source compound in water in a certain proportion and 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 powdered precursor; and sintering and grinding the powdered precursor to obtain a positive electrode material for a sodium-ion battery.

[0007] Preferably, the sodium source compound and the iron hydrogen phosphate hydrate in the dispersion 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 petrolatum, 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 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 grinding method may be one or two of mechanical grinding and airflow grinding.

[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 method for producing a positive electrode material for sodium-ion batteries according to an embodiment of the present invention uses iron hydrogen phosphate hydrate (Fe3(HPO4)4·H2O), a raw material having a constant iron-phosphorus ratio, as a precursor in the manufacturing process. This eliminates the micro-level influence of the processing process on the design of the raw material blending ratio, guarantees the uniformity of the raw materials, and results in a manufactured positive electrode material for sodium-ion batteries with high purity of the crystalline phase, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Furthermore, this manufacturing method is simple and suitable for application in large-scale industrial production. [Brief explanation of the drawing]

[0017] [Figure 1] This 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] This is an SEM diagram of the cathode material for a sodium-ion battery manufactured in Example 1 of the present invention. [Figure 3] This is an XRD diagram of the cathode material for a sodium-ion battery manufactured in Example 1 of the present invention. [Figure 4] This is a diagram of the initial charge-discharge curve at 0.1C for a button-type half-cell assembled with the sodium-ion battery positive electrode material manufactured in Example 1 of the present invention. [Figure 5] This is an XRD diagram of the cathode material for a sodium-ion battery manufactured in Example 2 of the present invention. [Figure 6] This is a diagram of the initial charge-discharge curve at 0.1C for a button-type half-cell assembled with the sodium-ion battery positive electrode material manufactured in Example 2 of the present invention. [Figure 7] This is an XRD diagram of the cathode material for a sodium-ion battery manufactured in Example 3 of the present invention. [Figure 8] This is a diagram of the initial charge-discharge curve at 0.1C for a button-type half-cell assembled with the sodium-ion battery positive electrode material manufactured in Example 3 of the present invention. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present invention will be described in detail. Examples of the above embodiments are shown in the drawings, and throughout, the same or similar reference numerals indicate the same or similar components, or components having the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are intended to interpret the present invention and should not be construed as limiting the present invention.

[0019] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the members and arrangements of specific examples are described below. Of course, these are merely exemplary and not intended to limit the present invention. Also, the present invention can repeatedly use reference numerals and / or reference alphabets in different examples. Such repetition is for the purpose of simplification and clarification and does not itself indicate the relationship between the various embodiments and / or arrangements considered. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art can be aware of the applicability of other processes and / or the use of other materials.

[0020] Embodiments of the present invention provide a method for manufacturing a positive electrode material for a sodium-ion battery and an application for manufacturing a positive electrode material for a sodium-ion battery with high purity of the crystal phase, high compaction density, and high energy density. The positive electrode material for a sodium-ion battery according to the present invention is sodium pyrophosphate iron phosphate, and its chemical formula is Na4Fe3(PO4)2P2O7. A sodium-ion battery manufactured based on the positive electrode material for a sodium-ion battery according to the present invention has 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 manufacturing a positive electrode material for a sodium-ion battery, including the following steps S1 to S4.

[0022] In step S1, a sodium source compound, an iron hydrogen phosphate hydrate, and a carbon source compound are dispersed in water at a certain ratio and stirred and mixed 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 and the iron hydrogen phosphate hydrate in the dispersion 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-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.

[0026] In step S2, the dispersion is put into a sand mill and sand milled for a certain 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 air drying, vacuum drying, freeze drying, and spray drying.

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

[0031] The sintering conditions include a sintering atmosphere, a sintering temperature, and a sintering time. The sintering atmosphere includes a mixture of one or more gases selected from nitrogen gas, argon gas, and helium gas. The sintering temperature may be 450 to 700°C, and the heating rate may be 1 to 3°C / min. The sintering time may be 6 to 24 hours. The grinding method may be one or two of mechanical grinding and pneumatic grinding.

[0032] The method for producing a positive electrode material for sodium-ion batteries according to an embodiment of the present invention uses iron hydrogen phosphate hydrate (Fe3(HPO4)4·H2O), a raw material having a constant iron-phosphorus ratio, as a precursor in the manufacturing process. This eliminates the micro-level influence of the processing process on the design of the raw material blending ratio, guarantees the uniformity of the raw materials, and results in a manufactured positive electrode material for sodium-ion batteries with high purity of the crystalline phase, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Sodium-ion batteries manufactured based on the positive electrode material for sodium-ion batteries according to the present invention exhibit excellent battery cycle performance and stability. Furthermore, the manufacturing method is simple and suitable for application in large-scale industrial production.

[0033] The specific process and effects of the method for producing the positive electrode material for sodium-ion batteries of the present invention will be described in more detail below with reference to several specific examples, but without limiting the scope of protection of the present invention.

[0034] (Example 1) This embodiment provides a method for manufacturing a positive electrode material for a sodium-ion battery, the positive electrode material for a sodium-ion battery manufactured in this embodiment being Na4Fe3(PO4)2P2O7, and includes the following steps.

[0035] 1 mole of iron hydrogen phosphate hydrate and 4 moles of sodium nitrate were weighed and dispersed in deionized water. 20% by mass of glucose was weighed off the iron hydrogen phosphate hydrate and added to the deionized water. The mixture was stirred to obtain a dispersion. The dispersion was sand-milled until the particle size of the solid particles in the dispersion reached DN50 = 0.2 μm, at which point polishing was stopped to obtain a paste. The polished paste was spray-dried to obtain a powdered precursor. The obtained powdered precursor was heated to 500°C at a rate of 2°C / min under a nitrogen gas atmosphere, maintained at this temperature for 18 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0036] Figure 2 is an SEM image of Na4Fe3(PO4)2P2O7, the cathode material manufactured in this embodiment.

[0037] Figure 3 is an XRD diagram of Na4Fe3(PO4)2P2O7, the cathode material manufactured in this embodiment.

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

[0039] (Example 2) This embodiment provides a method for manufacturing a positive electrode material for a sodium-ion battery, the positive electrode material for a sodium-ion battery manufactured in this embodiment being Na4Fe3(PO4)2P2O7, and includes the following steps.

[0040] 1 mole of iron hydrogen phosphate hydrate and 4 moles of sodium chloride were weighed and dispersed in deionized water. 30% by mass of glucose was weighed off the iron hydrogen phosphate hydrate and added to the deionized water. The mixture was stirred and mixed to obtain a dispersion. The dispersion was sand-milled until the particle size of the solid particles in the dispersion reached DN50 = 3.0 μm, at which point polishing was stopped to obtain a paste. The polished paste was 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, maintained at this temperature for 16 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0041] Figure 5 is an XRD diagram of Na4Fe3(PO4)2P2O7, the cathode material manufactured in this embodiment.

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

[0043] (Example 3) This embodiment provides a method for manufacturing a positive electrode material for a sodium-ion battery, the positive electrode material for a sodium-ion battery manufactured in this embodiment being Na4Fe3(PO4)2P2O7, and includes the following steps.

[0044] 1 mole of iron hydrogen phosphate hydrate and 4 moles of sodium acetate were weighed and dispersed in deionized water. 25% by mass of glucose was weighed off the iron hydrogen phosphate hydrate and added to the deionized water. The mixture was stirred to obtain a dispersion. The dispersion was sand-milled until the particle size of the solid particles in the dispersion reached DN50 = 4.6 μm, at which point polishing was stopped to obtain a paste. The polished paste was 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, maintained for 12 hours, cooled, and then crushed to obtain Na4Fe3(PO4)2P2O7, a positive electrode material for sodium-ion batteries.

[0045] Figure 7 is an XRD diagram of Na4Fe3(PO4)2P2O7, the cathode material manufactured in this embodiment.

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

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

[0048] Based on the above, the method for producing and applying the positive electrode material for sodium-ion batteries according to the embodiments of the present invention eliminates the micro-level influence of the processing process on the design of the raw material blending ratio by using iron hydrogen phosphate hydrate (Fe3(HPO4)4·H2O), a raw material having a constant iron-phosphorus ratio, as a precursor in the manufacturing process, thereby ensuring the uniformity of the raw materials. As a result, the manufactured positive electrode material for sodium-ion batteries has high purity of the crystalline phase, better crystallinity, better electrochemical performance, and higher compaction density and energy density. Sodium-ion batteries manufactured based on the positive electrode material for sodium-ion batteries according to the present invention exhibit excellent battery cycle performance and stability. Furthermore, the manufacturing method is simple and suitable for application in large-scale industrial production.

[0049] In this specification, any reference to terms such as “one embodiment,” “several embodiments,” “example,” “specific example,” or “several examples” means that the specific features, structures, materials, or properties described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms are not necessarily limited to the same embodiment or example. The specific features, structures, materials, or properties described can be appropriately combined in any one or more embodiments or examples. Furthermore, a person skilled in the art can combine or link different embodiments or examples and features of different embodiments or examples described herein, provided that they do not conflict with each other.

[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 objectives of the present invention, and that the scope of the present invention is limited by the claims and their equivalents.

Claims

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

3. The steps include adding the carbon source compound in an amount equal to 10 wt% to 55 wt% of the amount of iron hydrogen phosphate hydrate added, dispersing it in water, and stirring to obtain a dispersion, The steps include: placing the dispersion into a sand mill and sand milling until the particle size of the paste after sand milling is 0.1 μm < DN50 < 5 μm to obtain a paste; The steps include drying the paste after sand milling to obtain a powdered precursor, The step of sintering and grinding the aforementioned powdered precursor to obtain a positive electrode material for a sodium-ion battery is included, The aforementioned sodium source compound is sodium chloride. A method for manufacturing a positive electrode material for sodium-ion batteries, characterized by the above.

2. The carbon source compound is one or more of the following: 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. A method for producing a positive electrode material for a sodium-ion battery according to feature 1.

3. The sand milling method of the aforementioned sand mill includes one of the following: disc type, pin type, or turbine type. A method for producing a positive electrode material for a sodium-ion battery according to feature 1.

4. The drying method is one or more of the following: forced air drying, vacuum drying, freeze-drying, and spray drying. A method for producing a positive electrode material for a sodium-ion battery according to feature 1.

5. The sintering conditions include a sintering atmosphere, a sintering temperature, and a sintering time. The sintering atmosphere includes a mixture of one or more gases selected from nitrogen, argon, and helium. 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 hours. A method for producing a positive electrode material for a sodium-ion battery according to feature 1.

6. The aforementioned grinding method is one or two of the following: mechanical grinding and air-jet grinding. A method for producing a positive electrode material for a sodium-ion battery according to feature 1.

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