Positive electrode slurry, positive electrode sheet and sodium ion battery

Abstract

The present application discloses a positive electrode slurry, a positive electrode sheet, and a sodium-ion battery. The positive electrode slurry comprises: 90-110 parts by mass of a positive electrode active material, which includes a Prussian blue-based positive electrode material; 50-100 parts by mass of a solvent; 0.05-1.5 parts by mass of a first dispersant, which includes at least one of a benzimidazolone and an isoindolinone; 0.02-1.0 parts by mass of a second dispersant, which includes at least one of an alcoholamine, an etheramine, an amide, and an aniline; 2-10 parts by mass of a conductive agent; and 1-8 parts by mass of a binder.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a positive electrode slurry, a positive electrode sheet and a sodium ion battery. Background Art

[0002] Compared to lithium-ion batteries, sodium-ion batteries offer significant cost advantages. For example, sodium reserves are abundant, accounting for 2.74% of the Earth's crust, approximately 420 times the reserves of lithium (0.0065%). Furthermore, sodium-ion batteries have no overdischarge characteristics, allowing them to be discharged to zero. Furthermore, they are easy to store and transport, further reducing costs.

[0003] Although the mass energy density and volume energy density of sodium-ion batteries cannot currently compare with those of ternary lithium or even lithium iron phosphate, due to their obvious cost advantages, they are expected to be used in large-scale energy storage and new energy vehicles, and are one of the important research directions for the next generation of battery technology.

[0004] Currently, cathode materials for sodium-ion batteries primarily include transition metal oxides, polyanion materials, and Prussian blue materials. Prussian blue materials, due to their low raw material cost, high voltage platform, good sodium ion conductivity, high theoretical specific capacity, and ease of preparation, have become a research hotspot for cathode materials for sodium-ion batteries.

[0005] However, there are currently three main problems facing the industrialization of Prussian blue materials: one is the vacancy defects in the Prussian blue material; another is the difficulty in removing the crystal water; and the third is the poor electronic conductivity of the material.

[0006] Among them, regarding the third problem, the current method of reducing the particle size of Prussian blue material to improve its electronic conductivity is mostly used. However, in actual use, the tiny particles of Prussian blue material are difficult to disperse in the slurry and are easy to agglomerate, which makes it difficult to manufacture the electrode, and thus causes the improvement in electronic conductivity to fall short of expectations.

[0007] Therefore, a positive electrode slurry, a positive electrode sheet and a sodium ion battery are needed to at least partially solve the above problems. Summary of the Invention

[0008] The Summary of the Invention introduces a series of simplified concepts that will be further described in the Detailed Description of the Invention. The Summary of the Invention of this application is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0009] To at least partially solve the above problems, the first aspect of the present application provides a positive electrode slurry for a sodium ion battery, the positive electrode slurry comprising:

[0010] 90-110 parts by mass of a positive electrode active material, wherein the positive electrode active material comprises a Prussian blue-based positive electrode material;

[0011] Solvent, 50-100 parts by mass;

[0012] A first dispersant, 0.05-1.5 parts by mass, wherein the first dispersant comprises at least one of a benzimidazolone substance and an isoindolinone substance;

[0013] A second dispersant, 0.02-1.0 parts by mass, wherein the second dispersant comprises at least one of an alcoholamine, an etheramine, an amide, and an aniline;

[0014] Conductive agent, 2-10 parts by mass;

[0015] Adhesive, 1-8 parts by mass.

[0016] According to the positive electrode slurry of the present application, the dispersion is uniform and not easy to agglomerate, the electronic conductivity of the slurry is improved, and the coating performance is good. The battery prepared using the positive electrode slurry of the present application has a high specific capacity and good cycle performance.

[0017] Optionally, the positive electrode slurry includes:

[0018]

[0019] Optionally, the first dispersant includes at least one of 2-benzimidazolone, isoindolin-1-one, 5-fluoroisoindolin-1-one, 2-methylisoindolin-1-one, and 5-nitroisoindolin-1-one.

[0020] Optionally, the second dispersant includes at least one of methoxy polyethylene glycol amine, polyethylene glycol diacrylamide, polyetheramine, polyetherimide, and polyaniline.

[0021] Optionally, the D50 particle size of the secondary particles of the positive electrode active material is 2 μm-5 μm;

[0022] The D50 particle size of the primary particles of the positive electrode active material is 100 nm-500 nm.

[0023] Optionally, the Prussian blue cathode material has the following chemical formula:

[0024] Na x M[Fe(CN)6] y zH2O,

[0025] Wherein, M is selected from one of Co, Mn, Ni, Fe and Cu, 0<x≤2, 0<y≤1, z≥0.

[0026] Optionally, the conductive agent includes at least one of carbon black, carbon nanotubes and graphene.

[0027] Optionally, the adhesive includes at least one of polyvinylidene fluoride, polyperfluoroethylene, polytetrafluoroethylene and polyacrylic acid emulsion.

[0028] Optionally, the solvent comprises N-methylpyrrolidone and / or N,N-dimethylformamide.

[0029] Optionally, the positive electrode slurry is prepared by the following process steps:

[0030] The positive electrode active material, the solvent and the first dispersant are mixed and then subjected to at least one process of high shear dispersion, sand milling dispersion and ultrasonic crushing dispersion to form a first slurry;

[0031] adding a second dispersant for low shear dispersion to form a second slurry;

[0032] A binder and a conductive agent are added and dispersed to form the positive electrode slurry.

[0033] A second aspect of the present application provides a positive electrode plate, the positive electrode plate comprising:

[0034] a positive conductive substrate; and

[0035] The positive electrode slurry described in the first aspect above;

[0036] The positive electrode slurry is coated on the positive electrode conductive substrate and subjected to a pressing and / or drying process to form the positive electrode sheet.

[0037] The positive electrode sheet according to the present application has the above-mentioned positive electrode slurry, and therefore has a technical effect similar to the above-mentioned positive electrode slurry. The battery prepared by the positive electrode sheet of the present application has a higher specific capacity and good cycle performance.

[0038] A third aspect of the present application provides a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the positive electrode sheet described in the second aspect.

[0039] The sodium ion battery according to the present application has a high specific capacity and good cycle performance. DETAILED DESCRIPTION

[0040] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, some technical features well known in the art are not described in order to avoid confusion with the present application.

[0041] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of the features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0042] Ordinal numbers such as “first” and “second” cited in this application are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term “first component” itself does not imply the existence of a “second component”, and the term “second component” itself does not imply the existence of a “first component”.

[0043] Now, exemplary embodiments according to the present application will be described in more detail.

[0044] A first aspect of the present application provides a positive electrode slurry for a sodium ion battery, the positive electrode slurry comprising:

[0045] Positive electrode active material, 90-110 parts by mass, the positive electrode active material is a Prussian blue positive electrode material,

[0046] Solvent, 50-100 parts by mass,

[0047] The first dispersant, 0.05-1.5 parts by mass, includes at least one of a benzimidazolone substance and an isoindolinone substance,

[0048] The second dispersant, 0.02-1.0 parts by mass, includes at least one of an alcoholamine, an etheramine, an amide, and an aniline.

[0049] Conductive agent, 2-10 parts by mass,

[0050] Adhesive, 1-8 parts by mass.

[0051] According to the positive electrode slurry of the present application, the dispersion is uniform and not easy to agglomerate, the electronic conductivity of the slurry is improved, and the coating performance is good. The battery prepared using the positive electrode slurry of the present application has a high specific capacity and good cycle performance.

[0052] Specifically, the positive electrode slurry includes a positive electrode active material, a solvent, a first dispersant, a second dispersant, a conductive agent, and a binder.

[0053] The Prussian blue-based positive electrode material may be Prussian blue and / or a Prussian blue analogue. As an optional embodiment, the positive electrode active material has the following chemical formula:

[0054] Na x M[Fe(CN)6] y ·zH2O, wherein M is selected from one of Co, Mn, Ni, Fe and Cu, 0<x≤2, 0<y≤1, z≥0. Preferably, x is 1 or 2, y is 1, and z is an integer. Exemplarily, when M is Fe, the substance is called Prussian blue (PB), and when M is other elements such as Co, Mn, Ni or Cu, the substance is called Prussian blue analogue (PBA). The amount of the positive electrode active material is 90-110 parts by mass. Preferably, the amount of the positive electrode active material is 97-103 parts by mass. Further preferably, the amount of the positive electrode active material is 100 parts by mass, that is, the other components can be added based on the weight of the positive electrode active material.

[0055] As an optional embodiment, the positive electrode active material is nanoscale Prussian blue and / or a Prussian blue analog. For example, the primary particles of the positive electrode active material have a D50 particle size of 100 nm to 500 nm. The secondary particles of the positive electrode active material have a D50 particle size of 2 μm to 5 μm. The secondary particles are formed by agglomeration, condensation, or other processes of the primary particles.

[0056] The solvent includes N-methylpyrrolidone and / or N,N-dimethylformamide. The amount of the solvent used is 50-100 parts by mass. Preferably, the amount of the solvent used is 60-80 parts by mass.

[0057] The first dispersant includes at least one of a benzimidazolone substance and an isoindolinone substance. The first dispersant is used in an amount of 0.05-1.5 parts by mass. Preferably, the first dispersant is used in an amount of 0.1-1.2 parts by mass. Specifically, the first dispersant includes at least one of 2-benzimidazolone, isoindolin-1-one, 5-fluoroisoindolin-1-one, 2-methylisoindolin-1-one, and 5-nitroisoindolin-1-one.

[0058] The second dispersant includes at least one of an alcoholamine, an etheramine, an amide, and an aniline. The second dispersant is used in an amount of 0.02-1.0 parts by mass. Preferably, the first dispersant is used in an amount of 0.05-8 parts by mass. Specifically, the second dispersant includes at least one of methoxypolyethylene glycol amine, polyethylene glycol diacrylamide, polyetheramine, polyetherimide, and polyaniline.

[0059] The conductive agent includes at least one of carbon black, carbon nanotubes, and graphene. For example, carbon black may be acetylene black or Ketjen black. Carbon nanotubes may be single-walled carbon nanotubes, multi-walled carbon nanotubes, or the like. The conductive agent is used in an amount of 2-10 parts by weight. Preferably, the conductive agent is used in an amount of 4-6 parts by weight. Too little conductive agent can result in excessive electrode sheet resistance, which in turn leads to insufficient battery capacity. Excessive conductive agent usage can reduce the proportion of positive electrode active material, affecting battery capacity.

[0060] The adhesive includes at least one of polyvinylidene fluoride, polyperfluoroethylene, polytetrafluoroethylene, and polyacrylic acid emulsion. The amount of adhesive used is 1-8 parts by mass. Preferably, the amount of adhesive used is 3-5 parts by mass. Too high a binder content affects the proportion of positive electrode active material, thereby affecting the battery capacity. Too low a binder content results in poor electrode peel strength, affecting the battery's cycling stability.

[0061] The cathode slurry is made through the following process steps:

[0062] The positive electrode active material, the solvent, and the first dispersant are mixed and then subjected to at least one of high-speed shear dispersion, sand milling dispersion, and ultrasonic crushing dispersion to form a first slurry. The high-speed shear dispersion may be a shear dispersion process with a linear velocity greater than 20 m / s.

[0063] A second dispersant is added to perform low-speed shear dispersion to form a second slurry. The low-speed shear dispersion may be a shear dispersion process with a linear speed of 20 m / s or more.

[0064] Add binder and conductive agent for dispersion to form positive electrode slurry.

[0065] First, high-speed shear dispersion, ultrasonic crushing or sand milling dispersion has a strong dispersing ability, which can help deagglomerate the agglomerated positive electrode active material particles. Adding a first dispersant therein can adsorb on the surface of the positive electrode active material particles to assist in dispersion, so that it can quickly deagglomerate and prevent the treated positive electrode active material from re-sedimenting in a short period of time.

[0066] The second dispersant added later has multiple anchoring groups that form multiple hydrogen bonds with the cathode active material, particularly the water in the Prussian White lattice. This allows it to firmly adhere to the surface of the Prussian White particles, preventing particle aggregation and maintaining slurry stability. However, to prevent the anchoring chains from being broken during the dispersion of the second dispersant, a low-speed shear dispersion process is used at this stage.

[0067] Therefore, the deagglomeration effect of the first dispersant and the suspension stabilization effect of the second dispersant cooperate to significantly improve the stability of the slurry while meeting the required fineness.

[0068] It is particularly important to note that when carbon nanotubes are used as the conductive agent, they must be added after the shearing step of the second dispersant, as the carbon nanotubes may be damaged during the shear dispersion process.

[0069] The second aspect of the present application provides a positive electrode sheet, comprising: a positive electrode conductive substrate and the positive electrode slurry of the first aspect, wherein the positive electrode slurry is applied to the positive electrode conductive substrate and subjected to a pressing and / or drying process to form the positive electrode sheet.

[0070] The positive electrode sheet according to the present application has the above-mentioned positive electrode slurry, and therefore has a technical effect similar to the above-mentioned positive electrode slurry. The battery prepared by the positive electrode sheet of the present application has a higher specific capacity and good cycle performance.

[0071] A third aspect of the present application provides a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the positive electrode plate of the second aspect.

[0072] The sodium ion battery according to the present application has a high specific capacity and good cycle performance.

[0073] The beneficial effects of the positive electrode slurry, positive electrode sheet and sodium ion battery of the present application will be further described below in combination with examples and comparative examples.

[0074] Example 1:

[0075] The positive electrode active material is Prussian blue, 100 parts by mass,

[0076] The solvent is N-methylpyrrolidone, 70 parts by mass;

[0077] The first dispersant is 2-benzimidazolone, 0.5 parts by mass;

[0078] The second dispersant is methoxy polyethylene glycol amine, 0.2 parts by mass;

[0079] The conductive agent is 41.67 parts by weight of carbon nanotubes with a solid content of 12% (the content of pure carbon nanotubes is 5 parts by weight, and the subsequent discussion will use the mass fraction of pure carbon nanotubes);

[0080] The adhesive is PVDF (polyvinylidene difluoride), brand 5130, 4 parts by mass.

[0081] Add the solvent to the container, then add the first dispersant and stir until dissolved. Then gradually add the positive electrode active material and stir until fluidity is achieved. Then, disperse the material by sand milling until the fineness is less than 30, forming the first slurry. Add the second dispersant to the first slurry and perform low-speed shear dispersion until uniform dispersion is achieved, forming the second slurry. Place the second slurry into the positive electrode slurry dispersing tank, then add the binder and conductive agent to form the positive electrode slurry.

[0082] The positive electrode slurry is coated according to the positive electrode coating process, dried, cut, slit, and stacked to make soft-pack batteries. The batteries are baked, injected, aged, formed, and secondarily aged before undergoing relevant performance tests.

[0083] Example 2:

[0084] The difference from Example 1 is that the amount of the first dispersant used is 0.05 parts by mass, and the amount of the second dispersant used is 0.02 parts by mass.

[0085] Example 3:

[0086] The difference from Example 1 is that the amount of the first dispersant used is 1.5 parts by mass, and the amount of the second dispersant used is 1.0 parts by mass.

[0087] Example 4:

[0088] The difference from Example 1 is that the amount of the first dispersant is 0.1 parts by mass, and the amount of the second dispersant is 0.05 parts by mass.

[0089] Example 5:

[0090] The difference from Example 1 is that the amount of the first dispersant is 1.2 parts by mass, and the amount of the second dispersant is 0.8 parts by mass.

[0091] Example 6:

[0092] The difference from Example 1 is that the first dispersant is isoindolin-1-one, and the second dispersant is polyetheramine.

[0093] Example 7:

[0094] The difference from Example 1 is that the first dispersant is 2-methylisoindolin-1-one, and the second dispersant is polyaniline.

[0095] Example 8:

[0096] The difference from Example 1 is that the first dispersant is 5-nitroisoindolin-1-one, and the second dispersant is polyethylene glycol diacrylamide.

[0097] Example 9:

[0098] The positive electrode active material is Prussian blue, 97 parts by mass,

[0099] The solvent is N-methylpyrrolidone, 80 parts by mass;

[0100] The first dispersant is 2-benzimidazolone, 0.5 parts by mass;

[0101] The second dispersant is methoxy polyethylene glycol amine, 0.2 parts by mass;

[0102] The conductive agent is carbon nanotubes, 4 parts by mass;

[0103] The adhesive is PVDF (brand 5130), 5 parts by mass.

[0104] The preparation process is the same as that in Example 1.

[0105] Example 10:

[0106] The positive electrode active material is Prussian blue, 103 parts by mass,

[0107] The solvent is N-methylpyrrolidone, 60 parts by mass;

[0108] The first dispersant is 2-benzimidazolone, 0.5 parts by mass;

[0109] The second dispersant is methoxy polyethylene glycol amine, 0.2 parts by mass;

[0110] The conductive agent is carbon nanotubes, 6 parts by mass;

[0111] The adhesive is PVDF (brand 5130), 3 parts by mass.

[0112] The preparation process is the same as that in Example 1.

[0113] Comparative Example 1: The difference from Example 1 is that the amount of the first dispersant used is 0.03 parts by mass, and the amount of the second dispersant used is 0.2 parts by mass.

[0114] Comparative Example 2:

[0115] The difference from Example 1 is that the amount of the first dispersant is 2 parts by mass, and the amount of the second dispersant is 0.2 parts by mass.

[0116] Comparative Example 3:

[0117] The difference from Example 1 is that the amount of the first dispersant used is 0.5 parts by mass, and the amount of the second dispersant used is 0.01 parts by mass.

[0118] Comparative Example 4:

[0119] The difference from Example 1 is that the amount of the first dispersant used is 0.5 parts by mass, and the amount of the second dispersant used is 1.5 parts by mass.

[0120] Comparative Example 5:

[0121] The difference from Example 1 is that the amount of the first dispersant used is 0.03 parts by mass, and the amount of the second dispersant used is 0.01 parts by mass.

[0122] Comparative Example 6:

[0123] The difference from Example 1 is that the amount of the first dispersant used is 2 parts by mass, and the amount of the second dispersant used is 1.5 parts by mass.

[0124] Comparative Example 7:

[0125] The difference from Example 1 is that the amount of the first dispersant is 2 parts by mass, and the amount of the second dispersant is 0.01 parts by mass.

[0126] Comparative Example 8:

[0127] The difference from Example 1 is that the amount of the first dispersant used is 0.03 parts by mass, and the amount of the second dispersant used is 1.5 parts by mass.

[0128] Comparative Example 9:

[0129] The difference from Example 1 is that no second dispersant is added.

[0130] Comparative Example 10:

[0131] The difference from Example 1 is that the first dispersant is polyvinyl pyrrolidone.

[0132] Comparative Example 11:

[0133] The difference from Example 1 is that the second dispersant is polyvinyl pyrrolidone.

[0134] Example 11:

[0135] The difference from Example 1 is that the conductive agent is added before the sand milling and dispersion process.

[0136] Example 12:

[0137] The difference from Example 1 is that no sand milling and dispersion process is performed, and all components are subjected to a conventional slurry mixing process (normal stirring).

[0138] The difference parameters of the above Examples 1-12 and Comparative Examples 1-11 are summarized in Table 1 below.

[0139] Table 1

[0140]

[0141]

[0142]

[0143] The following tests were performed on the above Examples 1-12 and Comparative Examples 1-11. The results are shown in Table 2 below.

[0144] Fineness test:

[0145] The fineness test was performed using a 50 μm scraper fineness meter (S / N: 215743). Each sample was measured three times and the average value was taken.

[0146] Viscosity test:

[0147] The viscosity test was performed using Anton Paar MCR102 rheometer, and the test results were taken at 50S. -1 The viscosity of the product is acceptable if it is 2500 ± 1000 mPa·s. After standing for 4 hours, test again and calculate the viscosity growth rate relative to the previous test.

[0148] Electrode resistance test:

[0149] The electrode resistance test was performed using a dual-electrical four-probe tester model FT-341. During the test, at least three points at different positions of the electrode were tested, and the test results were averaged.

[0150] Slurry stability test:

[0151] The stability of the slurry is characterized by a multiple light scattering instrument, and the characterization parameter is the TSI index (instability index). The larger the TSI value, the more unstable it is. It is generally believed that the slurry is stable when TSI < 1.

[0152] Battery capacity and cycle test:

[0153] Discharge capacity test: The battery was placed in a capacity sorting cabinet for capacity sorting. The capacity sorting conditions were: charge at 0.1C to 3.6V, then charge at 3.6V constant voltage until the charge current dropped to 0.05C, and then discharge at 0.1C to 1.5V. This cycle was repeated three times, and the final capacity was taken as the sorted capacity, recorded as the discharge capacity.

[0154] Cycling test: Charge at 1C to 3.6V, then charge at 3.6V constant voltage until the charge current drops to 0.05C, then discharge at 1C to 1.5V, for a total of 500 cycles. Then, test the discharge capacity again and calculate the capacity retention relative to the previous discharge capacity result.

[0155] Table 2

[0156]

[0157]

[0158] The “unmeasurable” fineness result in Table 2 above indicates that the radial size of the particles is too large and exceeds the upper limit of the test of the scraper fineness meter.

[0159] As shown in Table 2, the positive electrode slurry prepared in this application has low fineness and good dispersibility. Its TSI is less than 1, indicating good stability. The small change in viscosity after 4 hours also demonstrates good stability. The slurry viscosity is within an appropriate range, facilitating coating on the electrode sheet. Positive electrode sheets prepared using the positive electrode slurry in this application have low resistance, and the battery has high capacity and high capacity retention.

[0160] The processes and steps described in all the preferred embodiments above are merely examples. Unless adverse effects occur, various processing operations may be performed in a different order from the above process. The order of the steps in the above process may also be increased, combined, or deleted according to actual needs.

[0161] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the art of this application. The terms used herein are merely for describing specific implementation purposes and are not intended to limit this application. Features described herein in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or is otherwise indicated.

[0162] The present application has been illustrated through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and explanation, and the present application is not limited to the above-mentioned embodiments. According to the teachings of the present application, more variations and modifications can be made, and these variations and modifications all fall within the scope of protection claimed by the present application.

Claims

1. A positive electrode slurry for sodium ion battery, characterized in that: The positive electrode slurry comprises: 90-110 parts by mass of a positive electrode active material, wherein the positive electrode active material comprises a Prussian blue-based positive electrode material; Solvent, 50-100 parts by mass; A first dispersant, 0.05-1.5 parts by mass, wherein the first dispersant comprises at least one of a benzimidazolone substance and an isoindolinone substance; A second dispersant, 0.02-1.0 parts by mass, wherein the second dispersant comprises at least one of an alcoholamine, an etheramine, an amide, and an aniline; Conductive agent, 2-10 parts by mass; Adhesive, 1-8 parts by mass.

2. The positive electrode slurry according to claim 1, characterized in that The positive electrode slurry comprises:

3. The positive electrode slurry according to claim 1, characterized in that The first dispersant includes at least one of 2-benzimidazolone, isoindolin-1-one, 5-fluoroisoindolin-1-one, 2-methylisoindolin-1-one, and 5-nitroisoindolin-1-one.

4. The positive electrode slurry according to claim 1, characterized in that The second dispersant includes at least one of methoxy polyethylene glycol amine, polyethylene glycol diacrylamide, polyetheramine, polyetherimide, and polyaniline.

5. The positive electrode slurry according to claim 1, characterized in that The D50 particle size of the secondary particles of the positive electrode active material is 2 μm-5 μm; The D50 particle size of the primary particles of the positive electrode active material is 100 nm-500 nm.

6. The positive electrode slurry according to claim 1, characterized in that The Prussian blue cathode material has the following chemical formula: And x M[Fe(CN)6] y ·zH2O, Wherein, M is selected from one of Co, Mn, Ni, Fe and Cu, 0<x≤2, 0<y≤1, z≥0.

7. The positive electrode slurry according to claim 1, characterized in that The conductive agent includes at least one of carbon black, carbon nanotubes and graphene.

8. The positive electrode slurry according to claim 1, characterized in that The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene and polyacrylic acid emulsion.

9. The positive electrode slurry according to claim 1, characterized in that The solvent includes N-methylpyrrolidone and / or N,N-dimethylformamide.

10. The positive electrode slurry according to any one of claims 1 to 9, characterized in that: The positive electrode slurry is prepared by the following process steps: The positive electrode active material, the solvent and the first dispersant are mixed and then subjected to at least one process of high shear dispersion, sand milling dispersion and ultrasonic crushing dispersion to form a first slurry; adding a second dispersant for low shear dispersion to form a second slurry; A binder and a conductive agent are added and dispersed to form the positive electrode slurry.

11. A positive electrode plate, characterized in that: The positive electrode plate comprises: a positive conductive substrate; and The positive electrode slurry according to any one of claims 1 to 10; The positive electrode slurry is coated on the positive electrode conductive substrate and subjected to a pressing and / or drying process to form the positive electrode sheet.

12. A sodium ion battery, characterized in that: The positive electrode of the sodium ion battery includes the positive electrode sheet according to claim 11.

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