High-entropy doped polyanion positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy, and particularly relates to a high-entropy doped polyanion positive electrode material and a preparation method and application thereof. The high-entropy doped polyanion positive electrode material comprises an inner core, a coating layer 1 coating part of the inner core, and a coating layer 2 coating part of the inner core and part of the coating layer 1, the general formula of the inner core is Na4-aFe3-yTibZrcAldSneSbf (PO4) 2P2O7, a is greater than or equal to 0.02 and less than or equal to 0.10, y is greater than or equal to 0.05 and less than or equal to 0.3, y is equal to b + c + d + e + f, b is greater than or equal to 0.01 and less than or equal to 0.1, c is greater than or equal to 0.01 and less than or equal to 0.1, d is greater than or equal to 0.01 and less than or equal to 0.1, e is greater than or equal to 0.01 and less than or equal to 0.1, and f is greater than or equal to 0.01 and less than or equal to 0.1; the coating layer 1 is a first carbon layer; and the coating layer 2 is a second carbon layer. The high-entropy doped polyanion positive electrode material disclosed by the invention has excellent capacity performance and cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a high-entropy doped polyanion cathode material, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries have become a key alternative technology in the fields of energy storage and low-speed electric vehicles due to the abundance of sodium resources (2.3% of the earth's crust), the fact that their cost is only 1 / 10 of that of lithium, and the combination of high safety and wide temperature performance (capacity >70% at -40℃).

[0003] Polyanionic cathode material NFPP (Na4Fe3(PO4)2P2O7) is considered one of the most promising routes for industrialization due to its NASICON structural stability (volume change rate of only 2.5%) and thermal safety (no ignition during needle penetration / overcharge). However, NFPP suffers from insufficient capacity and cycle performance, which limits its application. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of poor discharge capacity and cycle performance of existing polyanion cathode materials NFPP, thereby providing a high-entropy doped polyanion cathode material, its preparation method and application.

[0005] Therefore, the present invention provides the following technical solution: The first aspect of this invention protects a high-entropy doped polyanion cathode material, wherein the high-entropy doped polyanion cathode material includes a core, a coating layer 1 covering a portion of the core, and a coating layer 2 covering a portion of the core and a portion of the coating layer 1. The general formula of the kernel is Na. 4-a Fe 3-y Ti b Zr c Al d Sn e Sb f (PO4)2P2O7, where 0.02≤a≤0.10, 0.05≤y≤0.3, y=b+c+d+e+f, 0.01≤b≤0.1, 0.01≤c≤0.1, 0.01≤d≤0.1, 0.01≤e≤0.1, 0.01≤f≤0.1; The coating layer 1 is a first carbon layer; The coating layer 2 is a second carbon layer.

[0006] In one alternative implementation, the general formula of the kernel is 0.02≤a≤0.05, 0.05≤y≤0.25, y=b+c+d+e+f, 0.05≤b≤0.1, 0.05≤c≤0.1, 0.05≤d≤0.1, 0.05≤e≤0.1, 0.05≤f≤0.1.

[0007] A second aspect of this invention protects a method for preparing the aforementioned high-entropy doped polyanion cathode material, wherein the preparation method includes the following steps: (1) A precursor is prepared by first mixing sodium source, iron source, titanium source, zirconium source and aluminum source in stoichiometric ratio; (2) The precursor and carbon source 1 are mixed for a second time to obtain an intermediate product; (3) The intermediate product, antimony source, tin source and carbon source 2 are mixed for the third time and sintered to obtain a high-entropy doped polyanion cathode material.

[0008] In step (1) of this invention, the first mixing method is a conventional mixing method in the art, which can be mixed evenly. Typically, without limitation, at room temperature (20-25℃), the mixture of sodium source, iron source, titanium source, zirconium source and aluminum source obtained according to the stoichiometric ratio is loaded into a zirconium oxide ball mill jar for ball milling. The ball-to-material ratio is 10-15:1, the ball milling speed is 300-600 rpm, and the first ball milling time is 2-20h. In order to avoid the decomposition of raw materials due to friction temperature, the cooling can be paused for 1-4h, and then the ball milling is carried out again at the same speed for a second time of 10-20h.

[0009] In step (1) of the present invention, the first mixing is followed by a drying step. The drying is a conventional method in the art. Typically, without limitation, spray drying is used. The spray drying conditions include: an inlet air temperature of 200-250°C, an outlet air temperature of 80-100°C, and a feed rate of 10-80 mL / min.

[0010] In one optional embodiment, the sodium source includes at least one of Na4P2O7, Na2CO3, and NaH2PO4; Na4P2O7 is optional.

[0011] In one optional embodiment, the iron source includes at least one of iron oxide (Fe2O3), iron carbonate, iron(II,III) oxide, iron chloride, iron acetate, iron sulfate, iron hydroxide, iron citrate, and ferrous oxalate; iron oxide may be selected as the iron source.

[0012] In one optional embodiment, the titanium source includes at least one of TiO2, TiOCl2, and TiOSO4, with TiO2 being the most suitable.

[0013] In one optional embodiment, the zirconium source includes at least one of ZrOCl2 and ZrO2, with ZrOCl2 being the most suitable.

[0014] In one optional embodiment, the aluminum source includes at least one of Al(NO3)3, Al2O3, and Al(OH)3, and may be selected as Al(NO3)3.

[0015] In one optional embodiment, the second mixing step includes: mixing carbon source 1 and solvent 1 to obtain a first mixture, immersing the precursor in the first mixture, wherein the precursor is completely immersed during immersion.

[0016] In one alternative implementation, the soaking time is 2-5 hours.

[0017] In this invention, solvent 1 is a conventional solvent in the art. Typically, without limitation, solvent 1 is water and / or ethanol, and water may be selected. In the first mixture, the concentration of carbon source 1 is 1-10 wt%. The precursor is immersed in the first mixture, and capillary action allows the first mixture to fully penetrate into the pores and depressions of the precursor, filling the microscopic defects and pores on the surface of the precursor.

[0018] In one alternative embodiment, the coating rate of the carbon source 1 is 2-8 wt%, optionally 3-6 wt%, based on the precursor.

[0019] In this invention, TEM (transmission electron microscopy) is used to observe the presence, morphology and interface of the coating layer with the precursor, and the coating rate is obtained by statistical analysis using the area method; a carbon-sulfur analyzer is used to analyze the material of the coating layer.

[0020] In this invention, the carbon source 1 is a conventional material in the art, typically and non-limitingly including any one of carboxymethyl cellulose and its derivatives, glucose, and graphene.

[0021] In one optional embodiment, the third mixing step includes: mixing an antimony source and a tin source in a stoichiometric ratio and then calcining to obtain an antimony-tin composite product; mixing the antimony-tin composite product, carbon source 2, and solvent 2 to obtain a second mixture; and using the second mixture to atomize and coat the intermediate product.

[0022] In this invention, the solvent 2 is a conventional solvent in the art. Typically, without limitation, the solvent 2 is water and / or ethanol, and ethanol can be selected. The solid-liquid ratio of carbon source 2 to solvent 2 is 1:1-10mL. The carbon source 2 ultimately corresponds to the coating layer 2. The atomized coating can prevent the carbon source 2 from agglomerating and ensure a significant improvement in the electronic conductivity of the material.

[0023] In one optional embodiment, the mass ratio of the antimony-tin composite product to carbon source 2 is 1:1-3.

[0024] In one optional embodiment, the coating rate of the carbon source 2 is 0.3-2 wt%, optionally 0.3-0.7 wt%, based on the intermediate product.

[0025] In this invention, TEM (transmission electron microscopy) is used to observe the presence, morphology and interface between the coating layer and the core, and the coating rate is obtained by statistical analysis using the area method; a carbon-sulfur analyzer is used to analyze the material of the coating layer.

[0026] In this invention, the carbon source 2 is a conventional material in the art, typically and non-limitingly including any one of carboxymethyl cellulose and its derivatives, glucose, and graphene.

[0027] In one optional embodiment, the calcination conditions include: a calcination temperature of 550-600°C and a calcination time of 2-10 hours.

[0028] In one optional embodiment, the atomization coating conditions include: a gas flow rate of 2-5 m / s and a pressure of 0.2-0.5 MPa.

[0029] In one alternative embodiment, the sintering includes a first sintering and a second sintering.

[0030] In this invention, the sintering is carried out in an inert gas atmosphere, typically and non-limitingly, the inert gas includes Ar.

[0031] In one optional embodiment, the conditions for the first sintering include: a heating rate of 2-10°C / min, a sintering temperature of 200-600°C, and a sintering time of 4-10 h.

[0032] In one optional embodiment, the conditions for the second sintering include: a heating rate of 1-10°C / min, a sintering temperature of 300-600°C, and a time of 5-12 hours.

[0033] A third aspect of this invention protects a secondary battery, wherein the secondary battery comprises the aforementioned high-entropy doped polyanion cathode material or the high-entropy doped polyanion cathode material prepared by the aforementioned preparation method.

[0034] The technical solution of this invention has the following advantages: 1. This invention provides a high-entropy doped polyanion cathode material, wherein the high-entropy doped polyanion cathode material comprises a core, a coating layer 1 covering a portion of the core, and a coating layer 2 covering a portion of the core and a portion of the coating layer 1; the core has the general formula Na. 4-a Fe 3-y Ti b Zr c Al d Sn eSb f (PO4)2P2O7, wherein 0.02≤a≤0.10, 0.05≤y≤0.3, y=b+c+d+e+f, 0.01≤b≤0.1, 0.01≤c≤0.1, 0.01≤d≤0.1, 0.01≤e≤0.1, 0.01≤f≤0.1; the coating layer 1 is the first carbon layer; the coating layer 2 is the second carbon layer; the high-entropy doped polyanion cathode material of the present invention has excellent capacity and cycle performance, wherein the five elements Ti, Zr, Al, Sn, and Sb doping can randomly occupy Fe sites, reducing the volume change rate and sodium ion migration barrier; wherein Ti and Zr elements can stabilize the lattice, Al elements can reduce the sodium ion migration barrier, Sn and Sb elements can improve electronic conductivity, the five elements work synergistically, and the specific coating layer ensures excellent electronic conductivity, together achieving the improvement of electrical performance.

[0035] 2. This invention provides a method for preparing a high-entropy doped polyanion cathode material, wherein the preparation method includes the following steps: (1) mixing sodium source, iron source, titanium source, zirconium source and aluminum source in a stoichiometric ratio to obtain a precursor; (2) mixing the precursor and carbon source 1 in a second mixing to obtain an intermediate product; (3) mixing the intermediate product, antimony source, tin source and carbon source 2 in a third mixing, and sintering to obtain a high-entropy doped polyanion cathode material; the five elements Ti, Zr, Al, Sn and Sb in the high-entropy doped polyanion cathode material of this invention work synergistically to improve the battery capacity and cycle retention rate; and in the preparation method, firstly, in step (2), the precursor and carbon source 1 are mixed, and carbon source 1 can fill the defects of the precursor, and then in step (3), the intermediate product is mixed with antimony source, tin source and carbon source 2 to construct a high-entropy doped polyanion cathode material. 2 Double-layer carbon coating with a carbon content greater than 85%.

[0036] 3. The specific third mixing step of this invention first mixes the antimony source and the tin source in a stoichiometric ratio and then calcines them, which enables the antimony source to undergo an in-situ transformation, such as from Sb2O3 to Sb2O4. This results in good storage properties, and the antimony-tin composite product formed after calcination has a uniform particle morphology. The atomization coating ensures that the carbon source can be uniformly attached to the surface, avoiding the coating layer from falling off or being partially missing. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0039] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0043] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0044] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0045] The ethanol is anhydrous ethanol; CMC (sodium carboxymethyl cellulose) with a weight-average molecular weight of 300-5000.

[0046] Example 1 This embodiment provides a high-entropy doped polyanion cathode material, the preparation method of which includes the following steps: (1) Na4P2O7, Fe2O3, TiO2, ZrOCl2, and Al(NO3)3 were mixed in stoichiometric ratio and ethanol was added to obtain a mixture. At room temperature, the mixture was loaded into a zirconia ball mill jar with a ball-to-material ratio of 10:1. The ball milling speed was 400 rpm for 12 h. The cooling was paused for 1 h, and then the mixture was ball milled at 400 rpm for 12 h to obtain a slurry with a solid content of 15%. The slurry was spray-dried with an inlet air temperature of 250℃, an outlet air temperature of 90℃, and a feed rate of 10 mL / min to obtain a precursor. (2) The precursor was soaked in a 5 wt% CMC aqueous solution until it was completely submerged for 2 hours and then dried at 80°C to obtain the intermediate product. The CMC coating rate was 5 wt% based on the precursor. (3) SnO2 and Sb2O3 were mixed in stoichiometric ratio and calcined at 550℃ for 4 hours to obtain an antimony-tin composite product. Graphene and ethanol were added, wherein the mass ratio of the antimony-tin composite product to graphene was 1:1, and the solid-liquid ratio of graphene to ethanol was 1g:2mL. The mixture was ultrasonically dispersed for 30 minutes to obtain a second mixture. In a fluidized bed, the second mixture was atomized and coated with the intermediate product in gas form. The gas flow rate was 2m / s, and the atomization pressure was 0.2MPa. Based on the intermediate product, the graphene content was... The coating rate was 0.5 wt%. The coated material was placed in an Ar atmosphere with a flow rate of 200 mL / min and sintered at 300 °C at a rate of 5 °C / min for 6 h. Then, it was sintered at 480 °C at a rate of 2 °C / min for 12 h to obtain a high-entropy doped polyanion cathode material, including a core and a coating layer 1 covering part of the core, and a coating layer 2 covering part of the core and part of the coating layer 1. The chemical formula of the core is Na. 3.95 Fe 2.75 Ti 0.05 Zr 0.05 Al 0.05 Sn 0.05 Sb 0.05(PO4)2P2O7; Coating layer 1 is the first carbon layer, and coating layer 2 is the second carbon layer.

[0047] Example 2 This embodiment provides a high-entropy doped polyanion cathode material, the preparation method of which includes the following steps: (1) Na4P2O7, Fe2O3, TiO2, ZrOCl2, and Al(NO3)3 were mixed in stoichiometric ratio and ethanol was added to obtain a mixture. At room temperature, the mixture was loaded into a zirconia ball mill jar with a ball-to-material ratio of 10:1. The ball milling speed was 400 rpm for 12 h. The cooling was paused for 1 h, and then the mixture was ball milled at 400 rpm for 12 h to obtain a slurry with a solid content of 15%. The slurry was spray-dried with an inlet air temperature of 250℃, an outlet air temperature of 90℃, and a feed rate of 10 mL / min to obtain a precursor. (2) The precursor was soaked in a 5 wt% CMC aqueous solution until it was completely submerged for 2 hours and then dried at 80°C to obtain the intermediate product. The CMC coating rate was 5 wt% based on the precursor. (3) SnO2 and Sb2O3 were mixed in stoichiometric ratio and calcined at 550℃ for 4 hours to obtain an antimony-tin composite product. Graphene and ethanol were added, wherein the mass ratio of the antimony-tin composite product to graphene was 1:1, and the solid-liquid ratio of graphene to ethanol was 1g:2mL. The mixture was ultrasonically dispersed for 30 minutes to obtain a second mixture. In a fluidized bed, the second mixture was atomized and coated with the intermediate product in gas form. The gas flow rate was 2m / s, and the atomization pressure was 0.2MPa. Based on the intermediate product, the graphene content was... The coating rate was 0.5 wt%. The coated material was placed in an Ar atmosphere with a flow rate of 200 mL / min and sintered at 300 °C at a rate of 5 °C / min for 6 h. Then, it was sintered at 480 °C at a rate of 2 °C / min for 12 h to obtain a high-entropy doped polyanion cathode material, including a core and a coating layer 1 covering part of the core, and a coating layer 2 covering part of the core and part of the coating layer 1. The chemical formula of the core is Na. 3.98 Fe 2.95 Ti 0.01 Zr 0.01 Al 0.01 Sn 0.01 Sb 0.01 (PO4)2P2O7; Coating layer 1 is the first carbon layer, and coating layer 2 is the second carbon layer.

[0048] Example 3 This embodiment provides a high-entropy doped polyanion cathode material, the preparation method of which includes the following steps: (1) Na4P2O7, Fe2O3, TiO2, ZrOCl2, and Al(NO3)3 were mixed in stoichiometric ratio and ethanol was added to obtain a mixture. At room temperature, the mixture was loaded into a zirconia ball mill jar with a ball-to-material ratio of 10:1. The ball milling speed was 400 rpm for 12 h. The cooling was paused for 1 h, and then the mixture was ball milled at 400 rpm for 12 h to obtain a slurry with a solid content of 15%. The slurry was spray-dried with an inlet air temperature of 250℃, an outlet air temperature of 90℃, and a feed rate of 10 mL / min to obtain a precursor. (2) The precursor was soaked in a 5 wt% CMC aqueous solution until it was completely submerged for 2 hours and then dried at 80°C to obtain the intermediate product. The CMC coating rate was 5 wt% based on the precursor. (3) SnO2 and Sb2O3 were mixed in stoichiometric ratio and calcined at 550℃ for 4 hours to obtain an antimony-tin composite product. Graphene and ethanol were added, wherein the mass ratio of the antimony-tin composite product to graphene was 1:1, and the solid-liquid ratio of graphene to ethanol was 1g:2mL. The mixture was ultrasonically dispersed for 30 minutes to obtain a second mixture. In a fluidized bed, the second mixture was atomized and coated with the intermediate product in gas form. The gas flow rate was 2m / s, and the atomization pressure was 0.2MPa. Based on the intermediate product, the graphene content was... The coating rate was 0.5 wt%. The coated material was placed in an Ar atmosphere with a flow rate of 200 mL / min and sintered at 300 °C at a rate of 5 °C / min for 6 h. Then, it was sintered at 480 °C at a rate of 2 °C / min for 12 h to obtain a high-entropy doped polyanion cathode material, including a core and a coating layer 1 covering part of the core, and a coating layer 2 covering part of the core and part of the coating layer 1. The chemical formula of the core is Na. 3.90 Fe 2.7 Ti 0.06 Zr 0.06 Al 0.06 Sn 0.06 Sb 0.06 (PO4)2P2O7; Coating layer 1 is the first carbon layer, and coating layer 2 is the second carbon layer.

[0049] Test case Battery preparation method: The positive electrode material, PVDF (polyvinylidene fluoride), and SP (conductive carbon black) prepared in the examples and comparative examples are mixed in a mass ratio of 90:5:5 to obtain a mixture. An appropriate amount of N-methylpyrrolidone is added, and the mixture is homogenized, coated, dried, and cut to form a positive electrode sheet. A metal Na sheet is used as the counter electrode, and glass fiber is used as the separator. 1 mol / L NaPF6 is mixed in ethylene carbonate (EC) and fluoroethylene carbonate (FEC) as the electrolyte, wherein the mass ratio of EC to FEC is 95:5. During testing, a CR2032 coin cell is assembled from the positive electrode sheet, glass fiber separator, Na sheet, gasket, and spring sheet. The Blue Battery Testing System was used for testing. Test method for discharge specific capacity: Voltage range 2.0V-4.0V, charge to 4.0V at 0.1C rate, discharge to 2.0V at 0.1C rate to obtain 0.1C discharge specific capacity; charge to 4.0V at 0.1C rate, discharge to 2.0V at 15C rate to obtain 15C discharge specific capacity; Cycle retention rate test method: Charge to 4.0V at a charging rate of 0.1C, then discharge to 2.0V at a discharging rate of 0.1C, and cycle for 50 cycles to obtain the cycle retention rate. Cycle retention rate = (discharge capacity at the 50th cycle / discharge capacity at the 1st cycle) × 100%; The test results are shown in Table 1. Table 1

[0050] Existing materials typically have a discharge specific capacity of 115 mAh / g at 0.1C and 90 mAh / g at 15C, with a capacity retention of 85% after 50 cycles. The high-entropy doped polyanion cathode material of this invention exhibits excellent capacity and cycle performance. The doping with five elements—Ti, Zr, Al, Sn, and Sb—can randomly occupy Fe sites, reducing the volume change rate and the sodium ion migration barrier. Among these elements, Ti and Zr stabilize the crystal lattice, Al lowers the sodium ion migration barrier, and Sn and Sb enhance electronic conductivity. The five elements work synergistically, while a specific coating layer ensures excellent electronic conductivity, collectively improving electrical performance. In Examples 1-3, the doping amounts of five elements, Ti, Zr, Al, Sn, and Sb, were adjusted. It can be seen that specific doping amounts can affect the capacity performance and cycle performance of the battery.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-entropy doped polyanion cathode material, characterized in that, The high-entropy doped polyanion cathode material includes a core, a coating layer 1 covering a portion of the core, and a coating layer 2 covering a portion of the core and a portion of the coating layer 1. The general formula of the kernel is Na. 4-a Fe 3-y Ti b Zr c Al d Sn e Sb f (PO4)2P2O7, where 0.02≤a≤0.10, 0.05≤y≤0.3, y=b+c+d+e+f, 0.01≤b≤0.1, 0.01≤c≤0.1, 0.01≤d≤0.1, 0.01≤e≤0.1, 0.01≤f≤0.1; The coating layer 1 is a first carbon layer; The coating layer 2 is a second carbon layer.

2. The high-entropy doped polyanion cathode material according to claim 1, characterized in that, In the general formula of the kernel, 0.02≤a≤0.05, 0.05≤y≤0.25, y=b+c+d+e+f, 0.05≤b≤0.1, 0.05≤c≤0.1, 0.05≤d≤0.1, 0.05≤e≤0.1, 0.05≤f≤0.

1.

3. A method for preparing the high-entropy doped polyanion cathode material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) A precursor is prepared by first mixing sodium source, iron source, titanium source, zirconium source and aluminum source in stoichiometric ratio; (2) The precursor and carbon source 1 are mixed for a second time to obtain an intermediate product; (3) The intermediate product, antimony source, tin source and carbon source 2 are mixed for the third time and sintered to obtain a high-entropy doped polyanion cathode material.

4. The preparation method according to claim 3, characterized in that, The second mixing step includes: mixing carbon source 1 and solvent 1 to obtain a first mixture, and immersing the precursor in the first mixture; Optionally, the soaking time is 2-5 hours.

5. The preparation method according to claim 3 or 4, characterized in that, The third mixing step includes: mixing antimony source and tin source in stoichiometric ratio and calcining to obtain antimony-tin composite product; mixing antimony-tin composite product, carbon source 2 and solvent 2 to obtain second mixture; and using the second mixture to atomize and coat the intermediate product.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the antimony-tin composite product to carbon source 2 is 1:1-3; Optionally, the calcination conditions include: a calcination temperature of 550-600℃ and a calcination time of 2-10 hours; Optionally, the conditions for atomization coating include: a gas flow rate of 2-5 m / s and a pressure of 0.2-0.5 MPa.

7. The preparation method according to any one of claims 3-6, characterized in that, Based on the precursor, the coating rate of the carbon source 1 is 2-8 wt%, optionally 3-6 wt%; And / or, based on intermediate products, the coating rate of the carbon source 2 is 0.3-2 wt%, optionally 0.3-0.7 wt%.

8. The preparation method according to any one of claims 3-7, characterized in that, The sodium source includes at least one of Na4P2O7, Na2CO3, and NaH2PO4; Na4P2O7 may be selected as the sodium source. And / or, the iron source includes at least one of iron oxide, iron carbonate, iron(II,III) oxide, iron chloride, iron acetate, iron sulfate, iron hydroxide, iron citrate, and ferrous oxalate, and may be selected as iron oxide; And / or, the titanium source includes at least one of TiO2, TiOCl2, and TiOSO4, and may be TiO2; And / or, the zirconium source includes at least one of ZrOCl2 and ZrO2, optionally ZrOCl2; And / or, the aluminum source includes at least one of Al(NO3)3, Al2O3, and Al(OH)3; Al(NO3)3 may be selected as the aluminum source.

9. The preparation method according to any one of claims 3-8, characterized in that, The sintering includes a first sintering and a second sintering; Optionally, the conditions for the first sintering include: a heating rate of 2-10℃ / min, a sintering temperature of 200-600℃, and a sintering time of 4-10h; Optionally, the conditions for the second sintering include: a heating rate of 1-10℃ / min, a sintering temperature of 300-600℃, and a sintering time of 5-12h.

10. A secondary battery, characterized in that, The secondary battery comprises the high-entropy doped polyanion cathode material as described in claim 1 or 2, or the high-entropy doped polyanion cathode material prepared by the preparation method described in any one of claims 3-9.

Images