Preparation method for sodium-ion battery positive electrode material, and use of sodium-ion battery positive electrode material

Abstract

Provided is a preparation method for a sodium-ion battery positive electrode material. The preparation method comprises: dispersing a sodium source compound, an iron hydrogen phosphate hydrate, and a carbon source compound in water according to a certain ratio, and performing stirring for mixing to obtain a dispersion liquid; placing the dispersion liquid in a bead mill for bead milling for a certain duration to obtain a slurry; drying the bead-milled slurry to obtain a powdery precursor; and sintering and crushing the powdery precursor to obtain a sodium-ion battery positive electrode material. The sodium-ion battery positive electrode material prepared by the preparation method has high crystal phase purity and higher compaction density and energy density. A sodium-ion battery prepared on the basis of the sodium-ion battery positive electrode material has good battery cycle performance and stability. In addition, the preparation method has a simple process flow and is suitable for application in large-scale industrial production.

Description

Preparation method and application of sodium ion battery positive electrode material Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and more specifically, to a preparation method and application of a sodium ion battery positive electrode material. Background Art

[0002] As the current representative of secondary batteries with the best overall performance, the commercialization of lithium-ion batteries dates back to the 1990s. After years of research, lithium-ion batteries have become a mature battery technology. However, due to the limited abundance of lithium in the Earth's crust, lithium-ion batteries are unable to support the growing energy storage market. Sodium-ion batteries operate on a similar principle to lithium-ion batteries, and sodium salt reserves are abundant and easy to mine, making them more advantageous for large-scale application in the energy storage field.

[0003] Sodium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, separators and accessories. Among them, positive and negative electrode materials are the key to the performance of sodium-ion battery systems, and positive electrode materials are particularly prominent. Sodium-ion battery positive electrode materials are divided into three categories: transition metal oxides, Prussian white / blue, and polyanion types. Among them, polyanion-type sodium-ion battery positive electrode materials have the advantages of stable structure and small volume change during charge and discharge. Among the polyanion-type sodium-ion battery positive electrode materials, iron-based sodium batteries have the advantages of lowest cost and non-toxicity. Among them, sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7) is the most promising positive electrode material in iron-based sodium batteries. It has the advantages of low cost, environmental friendliness, high theoretical capacity (129mAh / g), excellent cycle performance and low volume expansion (about 4%).

[0004] Currently, the most cost-effective method for producing secondary battery cathode materials is a high-temperature solid-phase method using a grinding-spraying-sintering process. However, due to processing constraints, the raw materials used in preparing sodium ferric phosphate pyrophosphate using this process are unevenly mixed at the microscopic level, resulting in the formation of impurities such as sodium ferric phosphate and sodium ferric pyrophosphate. This results in a low crystal phase purity of the prepared cathode material. These shortcomings severely limit the subsequent application of this sodium ferric phosphate pyrophosphate cathode material.

[0005] Summary of the Invention

[0006] In view of the above, the present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a sodium-ion battery cathode material and its application. The sodium-ion battery cathode material prepared by the preparation method of the present invention has high crystal phase purity and exhibits higher compaction density and energy density. Furthermore, the preparation method has a simple process flow and is suitable for large-scale industrial production.

[0007] To this end, in a first aspect, an embodiment of the present invention provides a method for preparing a positive electrode material for a sodium ion battery, the preparation method comprising: dispersing a sodium source compound, ferric hydrogen phosphate hydrate, and a carbon source compound in water in a certain proportion, stirring and mixing, to obtain a dispersion; placing the dispersion in a sand mill and sand milling for a certain period of time to obtain a slurry; drying the sand-milled slurry to obtain a powdered precursor; and sintering and crushing the powdered precursor to obtain the positive electrode material for a sodium ion battery.

[0008] Preferably, the sodium source compound and the ferric hydrogen phosphate hydrate are added to the dispersion according to a molar ratio of n(Na):n(Fe)=4:3.

[0009] 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.

[0010] Preferably, the amount of the carbon source added is 10 wt% to 55 wt% of the amount of the ferric hydrogen phosphate hydrate added.

[0011] Preferably, the carbon source compound is one or more of vaseline, stearic acid, sucrose, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, oxalic acid, adipic acid, soluble starch, glucose, polyethylene glycol, maltose, cyclodextrin, carbon nanotubes, acetylene black and graphene.

[0012] Preferably, the sand mill includes one of the following sand milling methods: disc type, pin type, and turbine type; the particle size of the slurry after sand milling is controlled at 0.1 μm. <DN50<5μm。

[0013] Preferably, the drying method can be one or more of air drying, vacuum drying, freeze drying, and spray drying.

[0014] Preferably, the sintering conditions include sintering atmosphere, sintering temperature and sintering time, wherein the sintering atmosphere includes one or a mixture of nitrogen, argon and helium; the sintering temperature is 450-700°C, and the heating rate is 1-3°C / min; and the sintering time is 6-24h.

[0015] Preferably, the pulverization method can be one or both of mechanical pulverization and air flow pulverization.

[0016] In a second aspect, an embodiment of the present invention provides a sodium ion battery, comprising the sodium ion battery positive electrode material provided in the first aspect above.

[0017] The method for preparing a sodium-ion battery cathode material provided by an embodiment of the present invention uses hydrogen phosphate iron hydrate (Fe3(HPO4)4·H2O), a raw material with a fixed iron-phosphorus ratio, as a precursor during the preparation process. This eliminates the influence of the processing process on the designed raw material ratio at the microscopic level, ensures the uniformity of the raw materials, and ensures that the prepared sodium-ion battery cathode material has high crystal phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. At the same time, the preparation method has a simple process flow and is suitable for application in large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a flow chart of a method for preparing a positive electrode material for a sodium ion battery provided in an embodiment of the present invention.

[0019] FIG2 is a SEM image of the sodium ion battery positive electrode material prepared in Example 1 of the present invention.

[0020] FIG3 is an XRD diagram of the sodium ion battery positive electrode material prepared in Example 1 of the present invention.

[0021] FIG4 is a graph showing the first charge and discharge curves of a button-type half-cell assembled with the sodium ion battery positive electrode material prepared in Example 1 of the present invention at 0.1C.

[0022] FIG5 is an XRD diagram of the sodium ion battery positive electrode material prepared in Example 2 of the present invention.

[0023] FIG6 is a graph showing the first charge and discharge curves of a button-type half-cell assembled with the sodium ion battery positive electrode material prepared in Example 2 of the present invention at 0.1C.

[0024] FIG7 is an XRD pattern of the sodium ion battery positive electrode material prepared in Example 3 of the present invention.

[0025] FIG8 is a graph showing the first charge and discharge curves of a button-type half-cell assembled with the sodium ion battery positive electrode material prepared in Example 3 of the present invention at 0.1C. DETAILED DESCRIPTION

[0026] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0027] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will appreciate the applicability of other processes and / or the use of other materials.

[0028] Embodiments of the present invention provide a method for preparing and applying a sodium-ion battery cathode material, which is used to prepare a sodium-ion battery cathode material with high crystal phase purity, high compaction density, and high energy density. The sodium-ion battery cathode material described herein is a sodium-iron phosphate pyrophosphate cathode material with the chemical formula Na₄Fe₃(PO₄)₂P₂Oₐ. Sodium-ion batteries prepared using this sodium-ion battery cathode material exhibit excellent battery cycling performance and stability.

[0029] As shown in FIG1 , a first embodiment of the present invention provides a method for preparing a positive electrode material for a sodium ion battery, comprising the following steps:

[0030] Step S1: dispersing a sodium source compound, ferric hydrogen phosphate hydrate, and a carbon source compound in water in a certain proportion and stirring and mixing to obtain a dispersion;

[0031] In an embodiment of the present invention, the chemical formula of the ferric hydrogen phosphate hydrate is Fe3(HPO4)4·H2O, and the sodium source compound and the ferric hydrogen phosphate hydrate are added to the dispersion in a molar ratio of n(Na):n(Fe)=4:3.

[0032] 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.

[0033] The amount of the carbon source added is 10wt%-55wt% of the amount of ferric hydrogen phosphate hydrate added; the carbon source compound can be one or more of vaseline, stearic acid, sucrose, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, oxalic acid, adipic acid, soluble starch, glucose, polyethylene glycol, maltose, cyclodextrin, carbon nanotubes, acetylene black and graphene.

[0034] Step S2: placing the dispersion in a sand mill and sand-milling for a certain period of time to obtain a slurry;

[0035] The sand mill has a sand grinding method including disc type, pin type and turbine type. The particle size of the slurry after sand grinding is controlled at 0.1 μm. <DN50<5μm。

[0036] Step S3: drying the sand-milled slurry to obtain a powdered precursor;

[0037] The drying method may be one or more of air drying, vacuum drying, freeze drying, and spray drying.

[0038] Step S4: Sintering and crushing the powdered precursor to obtain the sodium ion battery positive electrode material.

[0039] The sintering conditions include sintering atmosphere, sintering temperature, and sintering time. The sintering atmosphere includes one or a mixture of nitrogen, argon, and helium. The sintering temperature can be 450-700°C, with a heating rate of 1-3°C / min. The sintering time can be 6-24 hours. The pulverization method can be one or both of mechanical pulverization and airflow pulverization.

[0040] The preparation method of the sodium ion battery positive electrode material provided in an embodiment of the present invention uses a raw material of iron hydrogen phosphate hydrate (Fe3(HPO4)4·H2O) with a fixed iron-phosphorus ratio as a precursor during the preparation process, eliminating the influence of the processing process on the designed raw material ratio at the microscopic level, ensuring the uniformity of the raw materials, and making the prepared sodium ion battery positive electrode material have high crystal phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. The sodium ion battery prepared based on the sodium ion battery positive electrode material of the present invention has good battery cycle performance and stability. At the same time, the preparation method has a simple process flow and is suitable for application in large-scale industrial production.

[0041] The following is a further detailed description of the specific process and effects of the method for preparing the positive electrode material for sodium ion batteries using the present invention in conjunction with some specific examples, but is not intended to limit the scope of protection of the present invention.

[0042] Example 1

[0043] This embodiment 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 embodiment is a Na4Fe3(PO4)2P2O7 positive electrode material, comprising the following steps:

[0044] Weigh 1 mol of ferric hydrogen phosphate hydrate and 4 mol of sodium nitrate, and disperse them in deionized water. Weigh 20% of the mass of glucose added to the deionized water, stir and mix to obtain a dispersion. Sand grind the dispersion, and stop grinding when the particle size of the solid particles in the dispersion reaches DN50 = 0.2 μm to obtain a slurry. Spray dry the ground slurry to obtain a powdered precursor. Place the obtained powdered precursor in a nitrogen atmosphere, heat it to 500°C at 2°C / min, keep it warm for 18 hours, and after the material is cooled and crushed, obtain Na4Fe3(PO4)2P2O7 sodium ion battery positive electrode material.

[0045] FIG2 is a SEM image of the Na4Fe3(PO4)2P2O7 cathode material prepared in this embodiment;

[0046] FIG3 is an XRD pattern of the Na4Fe3(PO4)2P2O7 cathode material prepared in this embodiment.

[0047] The Na4Fe3(PO4)2P2O7 cathode material prepared in this example, acetylene black, and PVDF were mixed with an appropriate amount of NMP in a mass ratio of 70:20:10. The black slurry was then coated onto aluminum foil using a 150μm four-sided film preparation device. The film was then vacuum-dried in a 110°C vacuum drying oven for 6 hours. The dried electrode film was then punched into circular discs of uniform radius using a sheet puncher to form the positive electrode. A button-type half-cell was assembled in a glove box with a water and oxygen content of less than 0.01ppm using sodium metal as the negative electrode, a glass fiber membrane as the separator, and a NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 volume ratio) electrolyte. The cells achieved a discharge capacity of 109.7mAh / g at a current density of 0.1C and a voltage range of 2.0-4.0V, as shown in Figure 4.

[0048] Example 2

[0049] This embodiment 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 embodiment is a Na4Fe3(PO4)2P2O7 positive electrode material, comprising the following steps:

[0050] Weigh 1 mol of ferric hydrogen phosphate hydrate and 4 mol of sodium chloride, and disperse them in deionized water. Weigh 30% of the mass of glucose added to the deionized water, stir and mix to obtain a dispersion. Sand grind the dispersion, and stop grinding when the particle size of the solid particles in the dispersion reaches DN50 = 3.0 μm to obtain a slurry. Spray dry the ground slurry to obtain a powdered precursor. Place the obtained powdered precursor in a nitrogen atmosphere, heat it to 550°C at 2°C / min, keep it warm for 16 hours, and after the material is cooled and crushed, obtain Na4Fe3(PO4)2P2O7 sodium ion battery positive electrode material.

[0051] FIG5 is an XRD pattern of the Na4Fe3(PO4)2P2O7 cathode material prepared in this embodiment.

[0052] The Na4Fe3(PO4)2P2O7 cathode material prepared in this example, acetylene black, and PVDF were mixed with an appropriate amount of NMP in a mass ratio of 70:20:10. The black slurry was then coated onto aluminum foil using a 150μm four-sided film preparation device. The film was then vacuum-dried in a 110°C vacuum drying oven for 6 hours. The dried electrode film was then punched into circular discs of uniform radius using a sheet puncher to form the positive electrode. A button-type half-cell was assembled in a glove box with a water and oxygen content of less than 0.01ppm, using sodium metal as the negative electrode, a glass fiber membrane as the separator, and a NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 by volume) electrolyte. The cells achieved a discharge capacity of 112.9mAh / g at a current density of 0.1C and a voltage range of 2.0-4.0V, as shown in Figure 6.

[0053] Example 3

[0054] This embodiment 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 embodiment is a Na4Fe3(PO4)2P2O7 positive electrode material, comprising the following steps:

[0055] Weigh 1 mol of ferric hydrogen phosphate hydrate and 4 mol of sodium acetate, and disperse them in deionized water. Weigh 25% of the mass of glucose added to the deionized water, stir and mix to obtain a dispersion. Sand grind the dispersion, and stop grinding when the particle size of the solid particles in the dispersion reaches DN50 = 4.6 μm to obtain a slurry. Spray dry the ground slurry to obtain a powdered precursor. Place the obtained powdered precursor in a nitrogen atmosphere, heat it to 600°C at 5°C / min, keep it warm for 12 hours, and after the material is cooled and crushed, obtain Na4Fe3(PO4)2P2O7 sodium ion battery positive electrode material.

[0056] FIG7 is an XRD pattern of the Na4Fe3(PO4)2P2O7 cathode material prepared in this embodiment.

[0057] The Na4Fe3(PO4)2P2O7 cathode material prepared in this example, acetylene black, and PVDF were mixed with an appropriate amount of NMP in a mass ratio of 70:20:10. The black slurry was then coated onto aluminum foil using a 150μm four-sided film preparation device. The film was then vacuum-dried in a 110°C vacuum drying oven for 6 hours. The dried electrode film was then punched into circular discs of uniform radius using a sheet puncher to form the positive electrode. A button-type half-cell was assembled in a glove box with a water and oxygen content of less than 0.01ppm using sodium metal as the negative electrode, a glass fiber membrane as the separator, and a NaPF6 / EC+DEC+DMC (EC:DEC:DMC = 1:1:1 volume ratio) electrolyte. The cells achieved a discharge capacity of 110.5mAh / g at a current density of 0.1C and a voltage range of 2.0-4.0V, as shown in Figure 8.

[0058] A second embodiment of the present invention provides a sodium ion battery, which includes a sodium ion battery positive electrode material prepared by the preparation method provided by the first embodiment above.

[0059] In summary, the preparation method and application of the sodium ion battery positive electrode material provided by the embodiment of the present invention adopts the raw material hydrogen phosphate iron hydrate (Fe3(HPO4)4·H2O) with a fixed iron-phosphorus ratio as a precursor in the preparation process, eliminating the influence of the processing process on the designed raw material ratio at the microscopic level, ensuring the uniformity of the raw materials, and making the prepared sodium ion battery positive electrode material have high crystal phase purity, better crystallinity, better electrochemical performance, and higher compaction density and energy density. The sodium ion battery prepared based on the sodium ion battery positive electrode material of the present invention has good battery cycle performance and stability. At the same time, the preparation method has a simple process flow and is suitable for application in large-scale industrial production.

[0060] In the description of this specification, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a positive electrode material for a sodium ion battery, characterized in that: The preparation method comprises: Dispersing a sodium source compound, ferric hydrogen phosphate hydrate and a carbon source compound in water according to a certain ratio and stirring and mixing to obtain a dispersion; placing the dispersion in a sand mill for a certain period of time to obtain a slurry; The sand-milled slurry is dried to obtain a powdered precursor; The powdered precursor is sintered and crushed to obtain the sodium ion battery positive electrode material.

2. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The sodium source compound and the ferric hydrogen phosphate hydrate are added in the dispersion according to a molar ratio of n(Na):n(Fe)=4:

3.

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

4. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The amount of the carbon source added is 10 wt% to 55 wt% of the amount of the ferric hydrogen phosphate hydrate added.

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

6. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The sand mill includes one of the following sand milling methods: disc type, pin type, and turbine type; the particle size of the slurry after sand milling is controlled at 0.1 μm. <DN50<5μm。 7. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The drying method may be one or more of air drying, vacuum drying, freeze drying, and spray drying.

8. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The sintering conditions include sintering atmosphere, sintering temperature and sintering time. The sintering atmosphere includes one or a mixed atmosphere of nitrogen, argon and helium. The sintering temperature is 450-700°C, and the heating rate is 1-3°C / min. The sintering time is 6-24h.

9. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, characterized in that: The pulverization method can be one or both of mechanical pulverization and air flow pulverization.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium ion battery positive electrode material prepared by the preparation method according to any one of claims 1 to 9.

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