Coating-modified sodium ion battery positive pole piece as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sodium-ion battery positive electrode materials, and discloses a coating modified sodium-ion battery positive electrode plate as well as a preparation method and application thereof. The coating modified sodium ion battery positive pole piece comprises a current collector, a positive pole material layer coated on the surface of the current collector and a functional coating coated on the surface of the positive pole material layer, the functional coating is formed by coating the surface of the positive electrode material layer with functional coating slurry and then heating and curing the functional coating slurry. The surface of the sodium ion battery positive pole piece is coated with a layer of functional coating slurry, and a layer of functional coating containing the conductive high-molecular polymer is formed on the surface of the positive pole piece, so that the conductivity and the structural stability of the positive pole piece are improved, and the cycle performance and the rate capability of the positive pole piece are improved. Compared with a common sodium ion battery, the sodium ion battery adopting the positive pole piece has the advantages that the 0.1 C cycle life is 200 times, the capacity retention rate is improved from 80% grade to 90% grade, the cycle performance improvement effect is good, and the rate capability is obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of positive electrode materials for sodium ion batteries, and in particular to a coating-modified positive electrode sheet for sodium ion batteries, a preparation method thereof, and an application thereof. Background Art

[0002] With the growing global demand for clean energy and the rapid development of industries such as electronic devices and electric vehicles, efficient, reliable and low-cost energy storage technology has become essential. Lithium-ion batteries have achieved great success in the past few decades and are widely used in various fields. However, the limited and uneven distribution of lithium resources has led to a gradual increase in its cost and faces some challenges in large-scale energy storage applications. Sodium-ion batteries have become a potential alternative energy storage technology due to their abundant sodium resources, wide distribution and low cost.

[0003] However, the existing sodium-ion batteries still have a certain gap in performance compared to lithium-ion batteries. Commonly used sodium-ion battery positive electrode materials, such as sodium ferrous phosphate, sodium vanadium phosphate and sodium ferrous pyrophosphate, have deficiencies in cycle stability, rate performance and conductivity. For example, the above-mentioned positive electrode materials are prone to structural collapse during the charge and discharge process, resulting in rapid decay of battery capacity; some materials have low electrical conductivity, which limits the performance of the battery during high-rate charge and discharge.

[0004] Based on this, how to improve the cycle performance and rate performance of sodium-ion battery positive electrode materials is crucial to promoting the commercial application of sodium-ion batteries. Summary of the invention

[0005] The present application provides a coating-modified sodium ion battery positive electrode sheet and a preparation method and application thereof, aiming to solve the problem of poor cycle performance and rate performance of existing sodium ion battery positive electrode materials.

[0006] In order to achieve the above objectives, the present application adopts the following technical solutions.

[0007] In a first aspect of the present application, a coating-modified sodium ion battery positive electrode sheet is provided, comprising a current collector, a positive electrode material layer coated on the surface of the current collector, and a functional coating coated on the surface of the positive electrode material layer;

[0008] The functional coating is formed by coating the functional coating slurry on the surface of the positive electrode material layer and curing it by heating.

[0009] Preferably, the functional coating slurry comprises, by weight, 80 to 95 parts of coating material, 2 to 15 parts of dispersant and 3 to 5 parts of binder;

[0010] The coating material includes a conductive high molecular polymer for providing sodium ion sites.

[0011] Further preferably, the conductive high molecular polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, polyparaphenylene and polyphenylene vinylene.

[0012] Further preferably, the dispersant includes at least one of N-methylpyrrolidone, acetone, polyacrylic acid, polyvinylpyrrolidone and carboxymethyl cellulose.

[0013] More preferably, the binder includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polypyrrole.

[0014] Preferably, the thickness of the functional coating is 1 to 15 μm.

[0015] Preferably, the positive electrode material includes an active material, a conductive agent and a binder;

[0016] The active substance includes sodium ferrous phosphate, sodium ferrous pyrophosphate, sodium ferric pyrophosphate or sodium vanadium phosphate.

[0017] Preferably, the mass ratio of the active material, the conductive agent and the binder is (7-9):(0.5-2):(0.5-1).

[0018] The second aspect of the present application provides a method for preparing the above-mentioned coating-modified sodium ion battery positive electrode sheet, comprising:

[0019] S1, mixing the active material, the conductive agent and the binder evenly to obtain a positive electrode material; mixing the coating material, the dispersant and the binder evenly to obtain a functional coating slurry;

[0020] S2, bonding the positive electrode material to the surface of the current collector and drying to obtain an intermediate electrode sheet;

[0021] S3, coating the functional coating slurry on the surface of the middle electrode, and drying and curing the slurry to obtain the functional coating slurry.

[0022] The third aspect of the present application provides the use of the above-mentioned coating-modified sodium ion battery positive electrode sheet in a sodium ion battery.

[0023] Compared with the prior art, the beneficial effects of this application are:

[0024] The present invention forms a layer of functional coating containing conductive polymer on the surface of the battery pole piece by coating a layer of functional coating slurry on the surface of the positive pole piece, thereby improving the conductivity and structural stability of the positive pole piece. The functional coating of the present application can, on the one hand, more effectively promote the transmission of electrons in the electrode material, reduce the internal resistance of the battery, thereby improving the rate performance and charge and discharge efficiency of the battery; on the other hand, the functional coating can store a certain amount of sodium ions, and the electrode reaction is similar to the adsorption and dissociation of ions on the electrode surface in a supercapacitor, which can be carried out quickly and reversibly, thereby improving the discharge specific capacity and discharge specific energy of the battery; in addition, the functional coating has good environmental stability, and can form a uniform conductive network structure on the electrode surface. During the battery charging and discharging process, the electrode material will experience changes such as volume expansion and contraction, and the conductive network can play a role of buffering and supporting, reducing the structural damage of the electrode material and improving the cycle stability of the battery; finally, the functional coating can form a protective film on the surface of the electrode material to prevent direct contact between the electrode and the electrolyte, thereby inhibiting the occurrence of side reactions.

[0025] Compared with ordinary sodium ion batteries with unmodified positive electrode sheets, the sodium ion battery using the positive electrode sheet of the present invention has a capacity retention rate of 200 cycles at 0.1C cycle life increased from 80% to 90%, and has a good cycle performance improvement effect and a significant rate performance improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 The cycle performance diagram of the sodium ion battery assembled with the positive electrode sheet of the present application;

[0028] Figure 2 The rate diagram of the sodium ion battery assembled with the positive electrode sheet of the present application;

[0029] Figure 3 A discharge specific energy diagram of a sodium ion battery assembled with the positive electrode sheet of the present application;

[0030] Figure 4 The charge and discharge curve of the sodium ion battery assembled with the positive electrode sheet of Example 1 at 0.1C;

[0031] Figure 5 This is a charge and discharge specific energy diagram of a sodium ion battery assembled with the positive electrode sheet of Example 1. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are all open terms, meaning including but not limited to.

[0034] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0035] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0036] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0037] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0038] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0039] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0040] In a first aspect, the present application provides a coating-modified sodium ion battery positive electrode sheet, comprising a current collector, a positive electrode material layer coated on the surface of the current collector, and a functional coating coated on the surface of the positive electrode material layer;

[0041] The functional coating is formed by coating the functional coating slurry on the surface of the positive electrode material layer and curing it by heating. The thickness of the functional coating is 1 to 15 μm, preferably 3 to 9 μm.

[0042] The present invention forms a functional coating layer containing a conductive high molecular polymer on the surface of the battery pole piece by coating a layer of functional coating slurry on the surface of the positive pole piece, thereby improving the conductivity and structural stability of the positive pole piece.

[0043] In the present application, the functional coating slurry, measured by weight, comprises raw materials including 80-95 parts of coating material, 2-15 parts of dispersant, and 3-5 parts of binder; preferably, the raw materials include 82-93 parts of coating material, 4-12 parts of dispersant, and 3-5 parts of binder; more preferably, the raw materials include 85-90 parts of coating material, 7-10 parts of dispersant, and 3-5 parts of binder.

[0044] Wherein, the coating material includes a conductive polymer for providing sodium ion sites. Specifically, the conductive polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, polyparaphenylene, and polyphenylene vinylene, preferably a mixture of any one or more of polyaniline, polyacetylene, polypyrrole, or polythiophene, and more preferably a mixture of any one or more of polyaniline, polyacetylene, or polypyrrole.

[0045] In the present application, the morphology of the conductive polymer is preferably three-dimensional porous. The three-dimensional porous structure has abundant pores and channels, which is conducive to the rapid transmission of sodium ions. During the charge and discharge process, the insertion and extraction of sodium ions will cause the volume of the positive electrode material to change, and the three-dimensional porous conductive polymer can provide a buffer space for the volume change of the positive electrode material, reduce the damage of the volume change to the electrode structure, and improve the cycle stability of the battery.

[0046] In the present application, the binder is used to improve the adhesion between the functional coating and the positive electrode material layer, thereby increasing the stability of the electrode structure. The binder includes one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose, styrene-butadiene rubber, and polypyrrole.

[0047] In the present application, the dispersant is used to uniformly disperse the conductive polymer and the binder, prevent aggregation, and improve adhesion and conductivity. The dispersant includes at least one of N-methylpyrrolidone (NMP), acetone, polyacrylic acid (PAA), polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), preferably N-methylpyrrolidone (NMP), acetone or polyacrylic acid (PAA).

[0048] In the present application, the positive electrode material includes an active substance, a conductive agent and a binder; preferably, the mass ratio of the active substance, the conductive agent and the binder is (7-9):(0.5-2):(0.5-1), such as 7:2:1, 8:1:1 or 9:0.5:0.5.

[0049] Among them, the active substance is a phosphate compound, including sodium ferrous phosphate, sodium ferrous pyrophosphate, sodium ferric pyrophosphate or sodium vanadium phosphate, preferably sodium ferrous pyrophosphate or sodium ferric pyrophosphate, more preferably pure phase sodium ferric pyrophosphate, whose chemical formula is Na4Fe3(PO4)2P2O7.

[0050] This application has no special requirements for the conductive agent and the adhesive, and the conductive agent and adhesive commonly used in sodium ion batteries can be used.

[0051] The functional coating of the present application, on the one hand, can more effectively promote the transmission of electrons in the electrode material, reduce the internal resistance of the battery, and thus improve the rate performance and charge and discharge efficiency of the battery; on the other hand, the functional coating can store a certain amount of sodium ions, and the electrode reaction is similar to the adsorption and dissociation of ions on the electrode surface in a supercapacitor, and can proceed rapidly and reversibly, thereby improving the discharge capacity and discharge energy of the battery; in addition, the functional coating has good environmental stability and can form a uniform conductive network structure on the electrode surface. During the battery charging and discharging process, the electrode material will undergo changes such as volume expansion and contraction, and the conductive network can play a role in buffering and supporting, reducing the structural damage of the electrode material and improving the cycle stability of the battery; finally, the functional coating can form a protective film on the surface of the electrode material to prevent direct contact between the electrode and the electrolyte, thereby inhibiting the occurrence of side reactions.

[0052] In a second aspect, the present application provides a method for preparing the above-mentioned coating-modified sodium ion battery positive electrode sheet, comprising:

[0053] S1, mixing the active material, the conductive agent and the binder evenly to obtain a positive electrode material; mixing the coating material, the dispersant and the binder evenly to obtain a functional coating slurry;

[0054] S2, bonding the positive electrode material to the surface of the current collector and drying to obtain an intermediate electrode sheet; wherein the current collector is copper foil or aluminum foil.

[0055] S3, coating the functional coating slurry on the surface of the intermediate electrode sheet, drying and curing, to obtain a positive electrode sheet for a sodium ion battery.

[0056] In the present application, the coating method includes one or more of coating, spraying, brushing, coating, spraying, dipping or soaking, preferably coating or spraying, such as transfer coating, extrusion coating, spraying or gravure printing coating; by coating, drying and curing, the functional coating is coated on the surface of the intermediate electrode to obtain a coating-modified sodium ion battery positive electrode.

[0057] The coating-modified sodium ion battery positive electrode plate of the present application can be used as a positive electrode for a sodium ion battery. Compared with an ordinary sodium ion battery with an unmodified positive electrode plate, the sodium ion battery using the positive electrode plate of the present invention has a capacity retention rate of 200 cycles at 0.1C cycle life increased from 80% to 90%, with good cycle performance improvement and significant rate performance improvement.

[0058] The present application is further described below by way of examples.

[0059] Example 1

[0060] This embodiment provides a method for preparing a coating-modified sodium ion battery positive electrode sheet, comprising:

[0061] 90 parts by weight of polyaniline, 7 parts by weight of polyvinylidene fluoride and 3 parts by weight of N-methylpyrrolidone are uniformly mixed to obtain a functional coating slurry;

[0062] The active material sodium ferric phosphate pyrophosphate, the conductive agent SuperP and the binder are mixed uniformly in a mass ratio of 7:2:1 to obtain a positive electrode material; wherein the binder is polyvinylidene fluoride (PVDF) dispersed in N-methylpyrrolidone (NMP), wherein the mass proportion of PVDF in NMP is 3.5wt%; the positive electrode material is compounded on an aluminum foil current collector, and heated and cured to obtain an intermediate electrode sheet;

[0063] The functional coating slurry is evenly coated on the middle electrode sheet by transfer coating method, with a coating thickness of 6 μm, and the positive electrode sheet is obtained by heating and curing.

[0064] Example 2

[0065] The difference between Example 2 and Example 1 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 8:1:1, and the rest is the same as Example 1.

[0066] Example 3

[0067] The difference between Example 3 and Example 1 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 9:0.5:0.5, and the rest is the same as Example 1.

[0068] Example 4

[0069] The difference between Example 4 and Example 1 is that the coating thickness is 3 μm, and the rest is the same as Example 1.

[0070] Example 5

[0071] The difference between Example 5 and Example 1 is that the coating thickness is 9 μm, and the rest is the same as Example 1.

[0072] Example 6

[0073] The difference between Example 6 and Example 1 is that polyaniline is replaced by polyacetylene, and the rest is the same as Example 1.

[0074] Example 7

[0075] The difference between Example 7 and Example 6 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 8:1:1, and the rest is the same as Example 6.

[0076] Example 8

[0077] The difference between Example 8 and Example 6 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 9:0.5:0.5, and the rest is the same as Example 6.

[0078] Example 9

[0079] The difference between Example 9 and Example 6 is that the coating thickness is 3 μm, and the rest is the same as Example 6.

[0080] Example 10

[0081] The difference between Example 10 and Example 6 is that the coating thickness is 9 μm, and the rest is the same as Example 6.

[0082] Embodiment 11

[0083] The difference between Example 11 and Example 1 is that polyaniline is replaced by polypyrrole, and the rest is the same as Example 1.

[0084] Example 12

[0085] The difference between Example 12 and Example 11 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 8:1:1, and the rest is the same as Example 11.

[0086] Embodiment 13

[0087] The difference between Example 13 and Example 11 is that the mass ratio of the active material sodium ferric pyrophosphate, the conductive agent Super P and the binder is 9:0.5:0.5, and the rest is the same as Example 11.

[0088] Embodiment 14

[0089] The difference between Example 14 and Example 11 is that the coating thickness is 3 μm, and the rest is the same as Example 11.

[0090] Embodiment 15

[0091] The difference between Example 15 and Example 11 is that the coating thickness is 9 μm, and the rest is the same as Example 11.

[0092] Example 16

[0093] The difference between Example 16 and Example 1 is that when preparing the functional coating slurry, polyacetylene is 85 parts, polyvinylidene fluoride is 5 parts, and N-methylpyrrolidone is 10 parts, and the rest is the same as Example 1.

[0094] Embodiment 17

[0095] The difference between Example 17 and Example 1 is that when preparing the functional coating slurry, polyacetylene is 80 parts, polyvinylidene fluoride is 5 parts, and N-methylpyrrolidone is 15 parts, and the rest is the same as Example 1.

[0096] Embodiment 18

[0097] The difference between Example 18 and Example 1 is that when preparing the functional coating slurry, polyacetylene is 90 parts, polyvinylidene fluoride is 3 parts, and N-methylpyrrolidone is 7 parts, and the rest is the same as Example 1.

[0098] The positive electrode sheet prepared in Example 1-15 was used as the positive electrode, the metal sodium was used as the counter electrode, and the electrolyte was NC-008. Through conventional processes such as coating, drying, rolling, slicing, and film making, a button-type sodium ion battery was assembled. The electrical properties were tested, and the test results are shown in Table 1.

[0099] Table 1 Performance data of button-type sodium ion batteries assembled with positive electrode sheets of Examples 1-15

[0100]

[0101] As can be seen from Table 1, the sodium ion batteries assembled with the positive electrode sheets of the present application all have good electrical properties. When the conductive polymer of the functional coating is polyaniline, under the same conditions, the electrical performance of the battery assembled with the positive electrode sheets is the best. Among them, as shown in Examples 1-3, when the coating thickness is 6 μm, its discharge specific capacity and discharge specific energy at 0.1C and 0.5C are the best, and it has good electrical properties for positive electrode materials of different ratios, and has wide applicability.

[0102] The sodium ion battery assembled with the positive electrode sheets prepared in Examples 1-3 has the best overall performance. The principle is that, on the one hand, polyaniline is a polymer compound with special electrical properties. By doping with sodium ions, polyaniline can achieve a reversible transition from an insulating state to a conductive state, thereby improving its conductivity. During this transformation process, the positive charge is delocalized from the nitrogen atom to the conjugated π bond, which significantly enhances the conductivity of polyaniline. On the other hand, the thickness of the polyaniline coating directly affects the transmission efficiency of sodium ions in the battery. If the coating is too thick, it will increase the difficulty of sodium ions passing through the coating, resulting in a decrease in the ion transmission rate. An increase in the coating thickness will also increase the internal resistance of the battery, thereby affecting the charge and discharge performance of the battery; if the coating is too thin, a uniform protective layer cannot be formed, so 6μm is the best thickness to explore.

[0103] The sodium ion battery assembled with the positive electrode sheets prepared in Examples 1-3 was subjected to a cycle performance test and a charge-discharge performance test to evaluate its cycle performance and rate performance.

[0104] Figure 1 The cycle performance diagram of the sodium ion battery assembled with the positive electrode sheets of Examples 1-3. Figure 1 It can be seen that since the polyaniline coating can realize the adsorption and dissociation of ions during the charge and discharge process, the formed protective layer has good stability to inhibit volume changes, so that the discharge specific capacity of the sodium ion batteries with three different ratios of positive electrode materials is improved, and the cycle under 200 cycles is more stable.

[0105] Figure 2 This is a rate diagram of a sodium ion battery assembled with the positive electrode sheets of Examples 1-3. Figure 2 It can be seen that the polyaniline coating forms a uniform conductive network structure on the electrode surface, and electrons can quickly migrate from the polyaniline to the current collector, which helps to improve the high current performance of the battery, thereby improving the battery's rate performance.

[0106] Figure 3 The discharge specific energy diagram of the sodium ion battery assembled with the positive electrode sheets of Examples 1-3. Figure 3 It can be seen that the polyaniline coating can store a certain amount of sodium ions, realize adsorption and dissociation during the charging and discharging process, thereby improving the discharge specific energy of the battery.

[0107] Figure 4 The charge and discharge curve of the sodium ion battery assembled with the positive electrode sheet of Example 1 at 0.1C. Figure 4 It can be seen that the discharge capacity of the sodium ion battery at 0.1C is 128mAh / g.

[0108] Figure 5 This is the charge and discharge energy diagram of the sodium ion battery assembled with the positive electrode sheet of Example 1. Figure 5 It can be seen that the discharge energy of sodium ion batteries at 0.1C is 365mWh / g.

[0109] Although the present application has been described in detail in general terms and in specific embodiments in this specification, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in the present application.

Claims

1. A coating-modified sodium ion battery positive electrode plate, characterized in that: It includes a current collector, a positive electrode material layer coated on the surface of the current collector, and a functional coating layer coated on the surface of the positive electrode material layer; The functional coating is formed by coating the functional coating slurry on the surface of the positive electrode material layer and curing it by heating.

2. The coating-modified sodium ion battery positive electrode sheet according to claim 1, characterized in that: The functional coating slurry comprises, by weight, 80 to 95 parts of coating material, 2 to 15 parts of dispersant and 3 to 5 parts of binder; The coating material includes a conductive high molecular polymer for providing sodium ion sites.

3. The coating-modified sodium ion battery positive electrode sheet according to claim 2, characterized in that: The conductive high molecular polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, polyparaphenylene and polyphenylene vinylene.

4. The coating-modified sodium ion battery positive electrode sheet according to claim 2, characterized in that: The dispersant includes at least one of N-methylpyrrolidone, acetone, polyacrylic acid, polyvinylpyrrolidone and carboxymethyl cellulose.

5. The coating-modified sodium ion battery positive electrode sheet according to claim 2, characterized in that: The binder includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polypyrrole.

6. The coating-modified sodium ion battery positive electrode sheet according to claim 1, characterized in that: The thickness of the functional coating is 1 to 15 μm.

7. The coating-modified sodium ion battery positive electrode sheet according to claim 1, characterized in that: The positive electrode material includes an active material, a conductive agent and a binder; The active substance includes sodium ferrous phosphate, sodium ferrous pyrophosphate, sodium ferric pyrophosphate or sodium vanadium phosphate.

8. The coating-modified sodium ion battery positive electrode sheet according to claim 7, characterized in that: The mass ratio of the active material, the conductive agent and the binder is (7-9):(0.5-2):(0.5-1).

9. The method for preparing the coating-modified sodium ion battery positive electrode sheet according to claim 1, characterized in that: include: S1, mixing the active material, the conductive agent and the binder evenly to obtain a positive electrode material; mixing the coating material, the dispersant and the binder evenly to obtain a functional coating slurry; S2, bonding the positive electrode material to the surface of the current collector and drying to obtain an intermediate electrode sheet; S3, coating the functional coating slurry on the surface of the middle electrode, and drying and curing the slurry to obtain the functional coating slurry.

10. Use of the coating-modified sodium ion battery positive electrode sheet according to any one of claims 1 to 8 in a sodium ion battery.

Images