Preparation method of sodium-ion battery positive electrode material and product and application of sodium-ion battery positive electrode material

Abstract

The invention discloses a preparation method of a sodium ion battery positive electrode material and a product and application thereof, and belongs to the technical field of sodium ion batteries, the preparation method comprises the following steps: mixing an iron source, phosphorus cerium lanthanum ore, a sodium source, a rare earth metal oxide and a carbon source in a solution system, grinding, and then carrying out spray drying to obtain a precursor; the iron source comprises ferric pyrophosphate Fe4 (P2O7) 3 and ferric phosphate FePO4; the molar ratio of the ferric pyrophosphate to the ferric phosphate to the phosphorus cerium lanthanum ore to the sodium source to the rare earth metal oxide to the carbon source is 1: 5: 3: 4: (0.01-0.50): 1; and sintering the precursor in an inert gas atmosphere to obtain the rare earth element doped iron-based polyanion material as the sodium ion battery positive electrode material. According to the method disclosed by the invention, the relatively weak sodium ion diffusivity and electron conductivity of the iron-based polyanion material can be improved, and the sodium ion battery further prepared can overcome the problems of gas production expansion, poor high-voltage stability and the like of a positive electrode sodium supplementing agent.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a method for preparing a sodium-ion battery cathode material, its products, and applications. Background Technology

[0002] Sodium-ion batteries are secondary batteries based on the reversible insertion / extraction of sodium ions between the positive and negative electrodes. They are an important supplementary system to lithium-ion batteries. Due to their advantages in low-temperature performance, safety performance and low cost, sodium-ion batteries have good application prospects in energy storage, power and communication fields.

[0003] Currently, the mainstream cathode materials used in sodium-ion batteries are layered oxides, polyanionic compounds, Prussian blue analogs, and organic compound electrode materials. Layered oxides, due to their high specific capacity and structural tunability, have become the first commercially available cathode material for sodium-ion batteries. However, their inherent overcharge sensitivity, insufficient thermal stability, and susceptibility to fire under needle penetration conditions pose safety hazards, severely limiting their widespread use. While Prussian blue analogs have a specific capacity comparable to lithium iron phosphate and are inexpensive, they suffer from inherent defects such as low compaction density, difficulty in removing internal water of crystallization, and the presence of cyano-toxic groups. Polyanionic compounds (such as sodium iron pyrophosphate NFPP, sodium vanadium phosphate NVP, sodium iron sulfate NFS, and their derivatives) offer advantages such as readily available raw materials, structural stability, and low cost. However, their core drawback lies in their low intrinsic conductivity, and some systems (such as vanadium-dependent NVP) face challenges related to elemental cost, toxicity, or environmental friendliness. Sodium-containing organic compounds have not yet achieved fully mature development and application. In summary, existing sodium-ion battery cathode materials all have certain defects. Therefore, developing new cathode material systems with higher overall performance has become a key direction for promoting further breakthroughs in this technology.

[0004] Rare earth elements, also known as "industrial vitamins," include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. Doping with rare earth elements significantly improves the conductivity of sodium-ion battery cathode materials. For example, Chinese patent document CN118039811A discloses a method for preparing a sodium-ion battery cathode material. First, sodium, manganese, iron, nickel, and rare earth metal sources are mixed and ground, then calcined at high temperature to obtain an intermediate. The intermediate and carbon materials are mixed and ground to obtain a carbon-doped cathode active material. A cathode binder is then prepared using polyethylene glycol and modified chitosan. Finally, the carbon-doped cathode active material, cathode binder, and cathode conductive agent are mixed uniformly to obtain the sodium-ion battery cathode material. Chinese patent document CN119852396A discloses a modified sodium iron pyrophosphate cathode material, its preparation method, and its application. This invention involves dissolving sodium, iron, phosphoric acid, carbon, and rare earth metal sources in deionized water and stirring until completely dissolved, resulting in a transparent yellowish-brown solution. The solution is then heated while continuously stirred until a yellowish-green gel is obtained. This gel is then vacuum-dried and further sintered. The sintered product is then ground to obtain a black powder, i.e., the cathode material powder. Although related patents indicate that rare earth element doping can improve material performance, its preparation process is usually quite complex, and the raw material cost is relatively high, which to some extent restricts the large-scale application prospects of this technology. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for preparing a sodium-ion battery cathode material, which can improve the relatively weak sodium-ion diffusion ability and electronic conductivity of iron-based polyanionic materials.

[0006] The specific technical solution adopted is as follows: A method for preparing a sodium-ion battery cathode material includes the following steps: S01 The precursor is obtained by mixing an iron source, cerium lanthanum phosphate (Ce,Y,La,Th)PO4, a sodium source, rare earth metal oxides, and a carbon source in a solution system, grinding the mixture, and then spray drying it. The iron source includes iron pyrophosphate Fe4(P2O7)3 and iron phosphate FePO4. The molar ratio of iron pyrophosphate, iron phosphate, cerium lanthanum phosphate, sodium source, rare earth metal oxides, and carbon source is 1:5:3:4:0.01-0.50:1. S02 The precursor is sintered in an inert gas atmosphere at 450℃~600℃ for 5-12 h to obtain rare earth element doped iron-based polyanionic material as a cathode material for sodium-ion batteries.

[0007] In the preparation of rare earth element-doped iron-based polyanionic materials, this invention uses lanthanum phosphate ore and rare earth metal oxides. Lanthanum phosphate ore is readily available and relatively abundant. Lanthanum phosphate ore is also a phosphate and can be used as a raw material for the synthesis of iron-based polyanionic materials. At the same time, lanthanum phosphate ore is easily dissolved and refined using phosphoric acid solvents. The introduction of rare earth metal oxides into the raw material system helps to further improve electrochemical performance.

[0008] Preferably, the sodium source is sodium phosphate and the carbon source is citric acid.

[0009] Preferably, the rare earth metal oxide is CeO2, Y2O3, Sc2O3 or lanthanide metal oxide Ln2O3 (such as La2O3, Nd2O3, Eu2O3, etc.).

[0010] Preferably, the solution system is a mixed solution system composed of phosphoric acid, ethanol and water, and the mass ratio of phosphoric acid, ethanol and water is 0.01-0.1:0.2-0.6:1.

[0011] Preferably, the inert atmosphere for sintering is a nitrogen atmosphere.

[0012] The present invention also provides a sodium-ion battery cathode material prepared by the aforementioned method.

[0013] The present invention also provides the application of the sodium-ion battery cathode material in the preparation of cathode slurry, cathode sheet or sodium-ion battery.

[0014] The present invention also provides a positive electrode slurry, which includes the aforementioned sodium-ion battery positive electrode material, a positive electrode sodium supplement, a conductive agent, a binder, and a positive electrode solvent.

[0015] Preferably, the positive electrode sodium supplement is sodium squartzate (Na2C4O4), the conductive agent is selected from one or more of conductive carbon black, Ketjen black, VGCF, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene; and the binder is selected from one or more of polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polybutylene acrylate, polyacrylic acid, and polyethylene glycol.

[0016] Sodium squartz (Na2C4O4), a sodium supplement for the positive electrode, can improve the charging capacity and initial efficiency of the positive electrode material in sodium-ion batteries, thereby increasing the specific energy and energy density of sodium-ion batteries.

[0017] More preferably, the solid content of the positive electrode slurry is 55%~75%. Taking the total mass of sodium-ion battery positive electrode material, positive electrode sodium supplement, conductive agent and binder as 1, the content of sodium-ion battery positive electrode material is 90.0%-93.0%, the content of positive electrode sodium supplement is 1.0-3.5%, the content of conductive agent is 0.03%-3.2%, and the balance is binder.

[0018] The present invention also provides a positive electrode sheet, including a positive current collector and a functional coating disposed on the surface of the positive current collector, the functional coating being made of the positive electrode slurry.

[0019] The present invention also provides a sodium-ion battery, comprising the aforementioned positive electrode, negative electrode, separator, and organic electrolyte.

[0020] Furthermore, the negative electrode sheet includes a negative current collector and a functional coating disposed on the surface of the negative current collector. The functional coating is made of a negative electrode slurry, which includes hard carbon, a conductive agent, a binder, and a negative electrode solvent. The solid content of the negative electrode slurry is 40% to 60%. Taking the total mass of hard carbon, conductive agent, and binder as 1, the content of hard carbon is 93.0% to 97.0%, the content of conductive agent is 1.0% to 2.0%, and the balance is binder.

[0021] The organic electrolyte comprises sodium salt, solvent, and additives. The sodium salt includes NaPF6 and NaFSI. The solvent is selected from cyclic solvents (ethylene carbonate EC, propylene carbonate PC, etc.) and chain solvents (dimethyl carbonate DMC, ethyl methyl carbonate EMC, etc.). The additives include fluoroethylene carbonate FEC, propylene sulfonate lactone PS, or ethylene sulfate DTD, etc. The sodium salt content in the organic electrolyte is 4%~20%, the additive content is ≤5%, and the balance is solvent.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The rare earth element-doped iron-based polyanionic material prepared by the present invention has a micro-nano structure and good processability. The prepared full battery has a high discharge capacity of 105 mAh / g and electrode compaction density (≥2.5g / cm3). It has good rate charging performance (3C charging capacity accounts for 97.5% of 0.2C charging capacity), low temperature discharge (-40℃ discharge capacity accounts for 74.2%), and cycle performance (room temperature 2C / 2C cycle 2255 cycles retention rate of 93.5%).

[0023] (2) The sodium-ion battery prepared by using the iron-based polyanionic material doped with rare earth elements of the present invention can overcome the problems of gas expansion and poor high-voltage stability of sodium-ion battery positive electrode supplementation agent, and can ensure the long-term cycle stability of sodium-ion battery operation. Attached Figure Description

[0024] Figure 1 This is a SEM image of the sodium-ion battery cathode material prepared in Example 3.

[0025] Figure 2 The image shows the XRD pattern of the sodium-ion battery cathode material prepared in Example 3.

[0026] Figure 3 The above shows the rate charging patterns of the sodium-ion batteries prepared in Example 2 and Comparative Example 1.

[0027] Figure 4 The graph shows a comparison of the discharge retention rates of sodium-ion batteries prepared in Example 2 and Comparative Example 1 at different temperatures.

[0028] Figure 5 The graph shows the cycle performance of the sodium-ion batteries prepared in Example 2 and Comparative Example 1. Detailed Implementation

[0029] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0030] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0031] Cerium lanthanum phosphate ore (Ce,Y,La,Th)PO4 is a commercially available product.

[0032] Example 1: Preparation of Sodium-ion Battery Cathode Material According to molar proportions, 1 part of iron pyrophosphate Fe4(P2O7)3, 3 parts of (Ce,Y,La,Th)PO4, 4 parts of Na3PO4, 5 parts of FePO4, 0.05 parts of La2O3, and 1 part of citric acid C6H8O7 were uniformly mixed in a solution system. The solution system was a mixed solution system composed of phosphoric acid, ethanol, and water, with a mass ratio of phosphoric acid, ethanol, and water of 5:20:75. The solid content of the obtained mixed solution was 55%. The mixed solution was ground in a sand mill for 3 h and then spray-dried to obtain a solid material precursor. The precursor was placed in a sagger and calcined under a nitrogen atmosphere at a calcination temperature of 500℃ for 7 h to obtain a rare earth element-doped iron-based polyanionic material as a cathode material for sodium-ion batteries.

[0033] Example 2: Preparation of Sodium-ion Batteries The sodium-ion battery cathode material prepared in Example 1, sodium squartzate (Na2C4O4) as a sodium supplement, carbon nanotubes (CNTs), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed and stirred in a mixing tank containing NMP at a mass ratio of 92.5%:3%:0.5%:1.5%:2.5% to obtain a cathode slurry (solid content of 65%). This cathode slurry was then coated onto both sides of a 12μm+1μm+1μm carbon-coated foil using a coating machine, resulting in a double-sided areal density of 310 g / m². 2 After rolling, a positive electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 148±2mm. For the negative electrode, hard carbon (BSHC320), conductive carbon black SP, sodium carboxymethyl cellulose CMC, styrene-butadiene rubber SBR, and polyacrylic acid PAA adhesive were mixed and stirred in a mixing tank containing H2O at a mass ratio of 95%:1.5%:0.5%:2%:1% to obtain a negative electrode slurry (solid content of 45%). This slurry was then coated onto both sides of a 12μm aluminum foil using a coating machine, with a double-sided areal density of 130 g / m². 2 After rolling, the negative electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 149±2mm. The prepared positive and negative electrode sheets are each slit into specific stack sizes. The separator is selected from Enjie 9μm+3μm+1μm+1μm membranes (9μm is wet-process PE base film, 3μm is alumina ceramic, and 1μm is PVDF adhesive on both sides). A single core is formed by stacking (winding) the separator-negative electrode-separator-positive electrode. The core is then shaped by hot pressing, welded, and sealed with a film. After vacuum baking, it enters the electrolyte injection process. The electrolyte injection volume is calculated at 7g / Ah, with the first injection accounting for 95% of the total electrolyte volume. It is then immersed at 45℃ for 48 hours before entering the formation negative pressure process. After formation, a second electrolyte injection (remaining 5%) is performed, followed by a second sealing. After discharge capacity testing and cell screening, a sodium-ion battery is obtained. The organic electrolyte formula is as follows: NaPF6:NaFSI:DMC:EMC:EC:PC:FEC:DTD:PS = (by mass) Sodium ion electrolyte was prepared using a ratio of 4%:10%:5%:16%:25%:35%:1%:1.5%:2.5%. The formation process was as follows: first, a discharge treatment was performed, with the lower limit voltage set at 0V and the current at 0.5C; then, the cell was charged to 3.2V at 0.05C, then to 3.35V at 0.1C, then to 3.5V at 0.2C, and finally to 4.05V at 0.5C, with negative voltage control throughout the process.

[0034] Example 3: Preparation of sodium-ion battery cathode material According to molar proportions, 1 part of iron pyrophosphate Fe4(P2O7)3, 3 parts of (Ce,Y,La,Th)PO4, 4 parts of Na3PO4, 5 parts of FePO4, 0.05 parts of Y2O3, and 1 part of citric acid C6H8O7 were uniformly mixed in a solution system. The solution system was a mixed solution system composed of phosphoric acid, ethanol, and water, with a mass ratio of phosphoric acid, ethanol, and water of 5:20:75. The solid content of the obtained mixed solution was 55%. The mixed solution was ground in a sand mill for 3 h and then spray-dried to obtain a solid material precursor. The precursor was placed in a sagger and calcined under a nitrogen atmosphere at a calcination temperature of 500℃ for 7 h to obtain a rare earth element-doped iron-based polyanionic material as a cathode material for sodium-ion batteries.

[0035] Example 4: Preparation of Sodium-ion Batteries The sodium-ion battery cathode material prepared in Example 3, sodium squartzate (Na2C4O4) as a sodium supplement, carbon nanotubes (CNTs), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed and stirred in a mixing tank containing NMP at a mass ratio of 90.5%:3.5%:1%:2.2%:2.8% to obtain a cathode slurry (solid content of 65%). This cathode slurry was then coated onto both sides of a 12μm+1μm+1μm carbon-coated foil using a coating machine, resulting in a double-sided areal density of 340 g / m². 2After rolling, a positive electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 148±2mm. The negative electrode is prepared by mixing hard carbon (BSHC320), conductive carbon black SP, sodium carboxymethyl cellulose CMC, styrene-butadiene rubber SBR, and polyacrylic acid PAA adhesive in a mixing tank containing H2O at a mass ratio of 94.3%:1.4%:1.3%:1%:2% to obtain a negative electrode slurry (solid content of 53%). This slurry is then coated onto both sides of a 12μm aluminum foil using a coating machine, with a double-sided areal density of 160g / m². 2 After rolling, the negative electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 154±2mm. The prepared positive and negative electrode sheets are each slit into specific stack sizes. The separator is selected from Enjie 9μm+1.5μm+2μm+2μm (9μm is wet-process PE base film, 1.5μm is alumina ceramic, and 2μm is PVDF adhesive on both sides). A single core is formed by stacking (winding) the separator-negative electrode-separator-positive electrode. The core is then shaped by hot pressing, welded, and sealed with a film. After vacuum baking, it enters the electrolyte injection process. The electrolyte injection volume is calculated at 7g / Ah, with the first injection accounting for 95% of the total electrolyte volume. It is then immersed at 45℃ for 48 hours before entering the formation negative pressure process. After formation, a second electrolyte injection (remaining 5%) is performed, followed by a second sealing. After discharge capacity testing and cell screening, a sodium-ion battery is obtained. The organic electrolyte formula is as follows: NaPF6:NaFSI:DMC:EMC:EC:PC:FEC:DTD:PS = (by mass) Sodium ion electrolyte was prepared using a ratio of 4%:10%:8%:13%:15%:45%:1.5%:1%:2.5%. The formation process was as follows: first, a discharge treatment was performed, with the lower limit voltage set at 0V and the current at 0.5C; then, the cell was charged to 3.2V at 0.05C, then to 3.35V at 0.1C, then to 3.5V at 0.2C, and finally to 4.05V at 0.5C, with negative voltage control throughout the process.

[0036] Comparative Example 1 The purchased sodium ferric phosphate composite JNFP-1 (sodium gluconate NFPP composite), carbon nanotubes (CNTs), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed and stirred in a mixing tank containing NMP at a mass ratio of 95.5%:0.5%:1.5%:2.5% to obtain a positive electrode slurry (solid content of 65%). This positive electrode slurry was then coated onto both sides of a 12μm+1μm+1μm carbon-coated foil using a coating machine, achieving a double-sided areal density of 340 g / m². 2 After rolling, a positive electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 148±2mm. For the negative electrode, hard carbon (BSHC320), conductive carbon black SP, sodium carboxymethyl cellulose CMC, styrene-butadiene rubber SBR, and polyacrylic acid PAA adhesive were mixed and stirred in a mixing tank containing H2O at a mass ratio of 95%:1.5%:0.5%:2%:1% to obtain a negative electrode slurry (solid content of 45%). This slurry was then coated onto both sides of a 12μm aluminum foil using a coating machine, with a double-sided areal density of 130 g / m². 2 After rolling, the negative electrode sheet is obtained, and the thickness of the electrode sheet after rolling is 149±2mm. The prepared positive and negative electrode sheets are each slit into specific stack sizes. The separator is selected from Enjie 9μm+3μm+1μm+1μm membranes (9μm is wet-process PE base film, 3μm is alumina ceramic, and 1μm is PVDF adhesive on both sides). A single core is formed by stacking (winding) the separator-negative electrode-separator-positive electrode. The core is then shaped by hot pressing, welded, and sealed with a film. After vacuum baking, it enters the electrolyte injection process. The electrolyte injection volume is calculated at 7g / Ah, with the first injection accounting for 95% of the total electrolyte volume. It is then immersed at 45℃ for 48 hours before entering the formation negative pressure process. After formation, a second electrolyte injection (remaining 5%) is performed, followed by a second sealing. After discharge capacity testing and cell screening, a sodium-ion battery is obtained. The organic electrolyte formula is as follows: NaPF6:NaFSI:DMC:EMC:EC:PC:FEC:DTD:PS = (by mass) Sodium ion electrolyte was prepared using a ratio of 4%:10%:5%:16%:25%:35%:1%:1.5%:2.5%. The formation process was as follows: first, a discharge treatment was performed, with the lower limit voltage set at 0V and the current at 0.5C; then, the cell was charged to 3.2V at 0.05C, then to 3.35V at 0.1C, then to 3.5V at 0.2C, and finally to 4.05V at 0.5C, with negative voltage control throughout the process.

[0037] Sample Analysis Figure 1 The image shows a SEM image of the sodium-ion battery cathode material prepared in Example 3. The image shows that the prepared sodium-ion battery cathode material is a micro / nano material. Figure 2 The image shows the XRD pattern of the sodium-ion battery cathode material prepared in Example 3. Its peak distribution is basically consistent with that of PDF#04-019-7540.

[0038] The performance of the sodium-ion batteries in Example 2 and Comparative Example 1, as shown in the table below, is the result of testing. Table 1 Performance test results of sodium-ion batteries in Example 2 and Comparative Example 1

[0039] The sodium-ion batteries of Example 2 and Comparative Example 1 were compared under the following conditions: rate charging (initial charge and discharge at 1.5-3.45V at 0.2C / 0.2C, with this charge capacity as the baseline, and the ratio of the capacity at other rates to the 0.2C charge capacity as the capacity retention value at other rates), discharge at different temperatures (0.5C charge and discharge capacity at 25℃ as the baseline capacity, and the 0.5C discharge capacity at other temperatures compared with that at 25℃ to obtain the capacity retention rate at different temperatures), and cycle performance (cycle test at 25℃ with 2C charge, 10min rest period, 2C discharge, 10min rest period, and charge / discharge voltage range of 1.5-3.45V). The results are as follows: Figures 3-5 As shown, the sodium-ion battery prepared in Example 2 outperforms Comparative Example 1 in terms of high-rate charging, low-temperature discharge, and 2C / 2C 100% DOD at 25℃ cycling performance. The sodium-ion battery prepared in Example 2 has a 3C charging capacity to 0.2C charging capacity ratio of 97.5%. The sodium-ion battery prepared in Example 2 has a discharge capacity ratio of 74.2% at -40℃. In Example 2, the 2C cycle retention rate after 2255 cycles is 93.5%, while in Comparative Example 1 it is 88.8% and the capacity is irrecoverable.

[0040] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, Includes the following steps: S01 The precursor is obtained by mixing an iron source, cerium lanthanum phosphate (Ce,Y,La,Th)PO4, a sodium source, rare earth metal oxides, and a carbon source in a solution system, grinding the mixture, and then spray drying it. The iron source includes iron pyrophosphate Fe4(P2O7)3 and iron phosphate FePO4. The molar ratio of iron pyrophosphate, iron phosphate, cerium lanthanum phosphate, sodium source, rare earth metal oxides, and carbon source is 1:5:3:4:0.01-0.50:

1. S02 The precursor is sintered in an inert gas atmosphere at 450℃~600℃ for 5-12 h to obtain rare earth element doped iron-based polyanionic material as a cathode material for sodium-ion batteries.

2. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The sodium source is sodium phosphate, and the carbon source is citric acid.

3. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The rare earth metal oxides are CeO2, Y2O3, Sc2O3 or lanthanide metal oxides Ln2O3.

4. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The solution system is a mixed solution system composed of phosphoric acid, ethanol and water, with a mass ratio of phosphoric acid, ethanol and water of 0.01-0.1:0.2-0.6:

1.

5. The sodium-ion battery cathode material prepared by the method for preparing sodium-ion battery cathode material according to any one of claims 1-4.

6. The application of the sodium-ion battery cathode material according to claim 5 in the preparation of cathode slurry, cathode sheet or sodium-ion battery.

7. A positive electrode slurry, characterized in that, The positive electrode slurry includes the sodium-ion battery positive electrode material as described in claim 5, the positive electrode sodium supplement, the conductive agent, the binder, and the positive electrode solvent.

8. The positive electrode slurry according to claim 7, characterized in that, The positive electrode sodium supplement is sodium squartzate (Na2C4O4); And / or, the conductive agent is selected from one or more of conductive carbon black, Ketjen black, VGCF, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene; And / or, the adhesive is selected from one or more of polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polybutylene acrylate, polyacrylic acid, and polyethylene glycol.

9. A positive electrode plate, characterized in that, It includes a positive current collector and a functional coating disposed on the surface of the positive current collector, the functional coating being made of the positive electrode slurry as described in claim 7.

10. A sodium-ion battery, characterized in that, Includes the positive electrode, negative electrode, separator, and organic electrolyte as described in claim 9; The negative electrode sheet includes a negative electrode current collector and a functional coating disposed on the surface of the negative electrode current collector. The functional coating is made of a negative electrode slurry, which includes hard carbon, a conductive agent, a binder, and a negative electrode solvent. Organic electrolytes include sodium salts, cyclic solvents, chain solvents, and additives.

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