Composite positive electrode material and preparation method thereof, and sodium ion battery

Abstract

The present application is applicable to the field of material technology, and provides a composite positive electrode material and a preparation method thereof, and a sodium ion battery, comprising: adding a specific yttrium salt and water to Na4P2O7, Fe(NO3)3·9H2O and NH4H2PO4 and uniformly mixing them; Y 3+ With P2O7 4‑ The molar ratio of yttrium-doped NFPP is (0.05-0.2):1; the mixed solution is spray-dried, and the resulting powder precursor is heated to 500-580°C at a heating rate of 2-5°C / min under an inert gas atmosphere for sintering. The present application is simple to operate, low in preparation cost, high in production capacity, and high in product quality. By optimizing the conditions for yttrium-doped NFPP, a composite material precursor composed of nanoparticles is prepared by spray drying. The carbonization is then completed by optimizing the high-temperature solid-phase sintering conditions. The resulting composite cathode material has excellent electrochemical properties, providing a new approach for the low-cost development of high-performance sodium-ion battery cathode materials.

Description

Technical Field

[0001] The present application belongs to the field of material technology, and in particular relates to a composite positive electrode material and a preparation method thereof, and a sodium ion battery. Background Art

[0002] As an emerging electrochemical energy storage technology, sodium-ion batteries have shown great development potential in the field of large-scale electrochemical energy storage due to their abundant resources, low price and high safety. In the research and development of sodium-ion batteries, the selection of cathode materials is crucial because they directly affect the energy density, cycle stability and cost-effectiveness of the battery. Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7, abbreviated as NFPP) is a promising cathode material because it combines the advantages of iron-based phosphate and pyrophosphate, such as high theoretical specific capacity (129mAh g -1 ), high average operating voltage (3.1V), small volume change (less than 4%), low cost and environmental friendliness have attracted attention.

[0003] However, due to the large anionic skeleton of NFPP, its intrinsic electronic conductivity is low and its rate performance is poor, which affects its electrochemical performance and application development. To further improve the performance of NFPP, researchers have adopted a variety of modification strategies, such as structural nanostructuring and various carbon material composites or surface carbon coatings. Studies have shown that while the design of suitable carbon composites or carbon coatings can effectively improve the surface conductivity of the material, resulting in high rate performance and good cycle stability, the inherent properties of the material itself will not be changed. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method for preparing a composite positive electrode material, aiming to solve the problem that the existing NFPP positive electrode material has low intrinsic electronic conductivity and poor rate performance, which leads to limited electrochemical performance and application development.

[0005] The embodiment of the present application is implemented as follows: a method for preparing a composite positive electrode material, comprising:

[0006] According to the chemical formula of Na4Fe3(PO4)2(P2O7), Na, Fe, PO4 3- and P2O7 4- The molar ratio of Na4P2O7, Fe(NO3)3·9H2O and NH4H2PO4 were weighed respectively, and yttrium salt and deionized water were added and mixed uniformly to obtain a mixed solution; wherein, Y 3+ With P2O7 4- The molar ratio is (0.05-0.2):1; the yttrium salt is one of Y(NO3)3, Y2(CO3)3, Y2(SO4)3 and YCl3;

[0007] The mixed solution is ground and then spray-dried to form a dry powder precursor;

[0008] The powder precursor is ground and then heated to 500-580° C. at a heating rate of 2-5° C. / min in an inert gas atmosphere for sintering to obtain a composite positive electrode material.

[0009] An embodiment of the present application further provides a composite positive electrode material, which is prepared by the above-mentioned method for preparing the composite positive electrode material.

[0010] An embodiment of the present application also provides a sodium ion battery, which includes the above-mentioned composite positive electrode material.

[0011] The embodiments of the present application provide a method for preparing a composite positive electrode material, which is simple to operate, has low preparation cost, high production capacity and high product quality. The present application optimizes the process conditions of yttrium-doped NFPP and combines it with a spray drying method to prepare a composite material precursor composed of nanoparticles. The carbonization is then completed in an inert gas atmosphere by optimizing the high-temperature solid-phase sintering conditions. The obtained NFPP-Y composite positive electrode material has excellent electrochemical properties, providing a new approach for the low-cost development of high-performance sodium-ion battery positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Na4Fe provided in Example 1 of this application 2.9 Y 0.1 SEM image of (PO4)2(P2O7) cathode material;

[0013] Figure 2 This is an SEM image of the Na4Fe3(PO4)2(P2O7) cathode material provided in Comparative Example 1 of the present application;

[0014] Figure 3 Na4Fe provided in Comparative Example 2 of this application 2.75 Y 0.25 SEM image of (PO4)2(P2O7) cathode material;

[0015] Figure 4 Na4Fe provided in Comparative Example 3 of this application 2.7 Y 0.3 SEM image of (PO4)2(P2O7) cathode material;

[0016] Figure 5 Na4Fe provided in Comparative Example 6 of this application 2.9 Y 0.1 SEM image of (PO4)2(P2O7) cathode material;

[0017] Figure 6 Na4Fe provided in Comparative Example 7 of this application 2.9 Y 0.1 SEM image of (PO4)2(P2O7) cathode material;

[0018] Figure 7 XRD diffraction patterns of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application;

[0019] Figure 8 This is a graph showing the first charge and discharge curves of the positive electrode materials provided in Example 1 and Comparative Examples 1-3 of the present application at a rate of 0.1C.

[0020] Figure 9 This is a cycling performance diagram of the positive electrode materials provided in Example 1 and Comparative Examples 1-3 of the present application at a 2C rate.

[0021] Figure 10 This is a rate performance diagram of the positive electrode materials provided in Example 1 and Comparative Examples 1-3 of the present application at a voltage of 2-4V and a temperature of 0.1-20C. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0023] The present invention provides a method for preparing a composite cathode material, comprising the following steps:

[0024] According to the chemical formula of Na4Fe3(PO4)2(P2O7), Na, Fe, PO4 3- and P2O7 4- Na4P2O7, Fe(NO3)3·9H2O and NH4H2PO4 are weighed respectively in a molar ratio, and yttrium salt and deionized water are added and uniformly mixed to obtain a mixed solution; the mixed solution is ground and then spray-dried to form a dry powder precursor;

[0025] The powder precursor is ground and then heated to 500-580° C. at a heating rate of 2-5° C. / min in an inert gas atmosphere for sintering to obtain a composite positive electrode material.

[0026] Among them, Y 3+ With P2O7 4- The molar ratio is (0.05-0.2):1, preferably 0.1:1.

[0027] Wherein, the yttrium salt is one of Y(NO3)3, Y2(CO3)3, Y2(SO4)3 and YCl3, preferably Y2(CO3)3.

[0028] In a preferred embodiment of the present application, after the powder precursor is ground, it is heated to 500-580°C at a heating rate of 2-5°C / min in an inert gas atmosphere for sintering, that is, in the step of obtaining a composite positive electrode material, the sintering treatment conditions are preferably: heating to 580°C at a heating rate of 2°C / min in an inert gas atmosphere for sintering.

[0029] In a preferred embodiment of the present application, the mixed solution is ground to a particle size of no more than 100 nm.

[0030] Optionally, the step of grinding the mixed solution and then spray drying it to form a dry powder precursor comprises:

[0031] The mixed solution is ground and then spray-dried at an inlet temperature of 220-250° C. and an outlet temperature of 85-100° C. to form a dry powder precursor.

[0032] Optionally, the powder precursor is ground and then heated to 500-580° C. at a heating rate of 2-5° C. / min in an inert gas atmosphere for sintering to obtain a composite positive electrode material, comprising:

[0033] The powder precursor is ground, heated to 500-580°C at a heating rate of 2-5°C / min in an inert gas atmosphere for sintering, kept at this temperature for 10-15 hours, cooled naturally to room temperature, and ground to obtain a composite positive electrode material.

[0034] Optionally, the preparation method of the composite positive electrode material may specifically include the following steps: (1) according to the chemical formula of Na4Fe3(PO4)2(P2O7), Na, Fe, PO4 3- and P2O7 4- The molar ratio of Na4P2O7, Fe(NO3)3·9H2O and NH4H2PO4 were weighed respectively, and a certain amount of yttrium salt was added to make Y 3+ With P2O7 4-The molar ratio of the raw materials is within the range of 0.05-0.2, and the raw materials are added to an appropriate amount of deionized water and mixed evenly by a magnetic stirrer. (2) The solution obtained in step (1) is transferred to a sand mill and ground for four hours to make the material particle size about 100 nanometers. (3) The mixed solution is spray-dried at an inlet temperature of 220-250°C and an outlet temperature of 85-100°C to form a dry powder precursor. (4) The powder precursor obtained in step (3) is fully ground with a mortar, placed in a tube furnace, and heated to 500-580°C at a heating rate of 2-5°C / min under an inert gas atmosphere, kept warm for 10-15 hours, then naturally cooled to room temperature, removed from the furnace, and ground for 10-20 minutes to obtain the NFPP-Y positive electrode material.

[0035] The amount of deionized water used can be adjusted by those skilled in the art based on the actual grinding conditions, and its amount has no effect on the properties of the obtained material.

[0036] The following examples describe the composite cathode material in detail, as shown below. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are all commercially available unless otherwise specified.

[0037] Example 1

[0038] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0039] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0040] Example 2

[0041] Press Na+ :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.95:2:1:0.05. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0042] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 3°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.95 Y 0.05 (PO4)2(P2O7) positive electrode material.

[0043] Example 3

[0044] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.8:2:1:0.2. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(SO4)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0045] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 550°C at a heating rate of 5°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.8 Y 0.2 (PO4)2(P2O7) positive electrode material.

[0046] Example 4

[0047] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and YCl3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0048] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 550°C at a heating rate of 3°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0049] Example 5

[0050] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y(NO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water with a molar ratio of 4:2.85:2:1:0.15, and mixed evenly with a magnetic stirrer.

[0051] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 500°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.85 Y 0.15 (PO4)2(P2O7) positive electrode material.

[0052] Example 6

[0053] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.95:2:1:0.05. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0054] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 500°C at a heating rate of 5°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.95 Y 0.05 (PO4)2(P2O7) positive electrode material.

[0055] Comparative Example 1

[0056] Press Na + :Fe 3+ :PO3 3- :P2O7 4- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.) and NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water at a molar ratio of 4:3:2:1 and mixed evenly using a magnetic stirrer.

[0057] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray-dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. High-temperature carbonization was carried out in a vacuum tube furnace using a one-step calcination method. That is, in an inert gas atmosphere, the temperature was increased to 580°C at a rate of 2°C / min and kept at this temperature for 10 hours. Then, the temperature was naturally cooled to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain the Na4Fe3(PO4)2(P2O7) positive electrode material.

[0058] Comparative Example 2

[0059] Press Na + :Fe3+ :PO3 3- :P2O7 4- :Y 3- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water at a molar ratio of 4:2.75:2:1:0.25 and mixed evenly using a magnetic stirrer.

[0060] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.75 Y 0.25 (PO4)2(P2O7) positive electrode material.

[0061] Comparative Example 3

[0062] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water in a molar ratio of 4:2.7:2:1:0.3 and mixed evenly using a magnetic stirrer.

[0063] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.7 Y 0.3 (PO4)2(P2O7) positive electrode material.

[0064] Comparative Example 4

[0065] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2O3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water at a molar ratio of 4:2.9:2:1:0.1 and mixed evenly using a magnetic stirrer.

[0066] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0067] Comparative Example 5

[0068] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and YF3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water at a molar ratio of 4:2.9:2:1:0.1 and mixed evenly using a magnetic stirrer.

[0069] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0070] Comparative Example 6

[0071] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y(HO)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0072] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0073] Comparative Example 7

[0074] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0075] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 1°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0076] Comparative Example 8

[0077] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0078] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 8°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0079] Comparative Example 9

[0080] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0081] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 580°C at a heating rate of 10°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0082] Comparative Example 10

[0083] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0084] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 450°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0085] Comparative Example 11

[0086] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0087] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 480°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1(PO4)2(P2O7) positive electrode material.

[0088] Comparative Example 12

[0089] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0090] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 600°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe 2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0091] Comparative Example 13

[0092] Press Na + :Fe 3+ :PO3 3- :P2O7 4- :Y 3- The molar ratio was 4:2.9:2:1:0.1. Na4P2O7 (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), Fe(NO3)3·9H2O (analytical grade, Xilong Scientific Co., Ltd.), NH4H2PO4 (analytical grade, Xilong Scientific Co., Ltd.) and Y2(CO3)3 (analytical grade, Shanghai Yien Chemical Technology Co., Ltd.) were weighed and dissolved in an appropriate amount of deionized water and mixed evenly using a magnetic stirrer.

[0093] The above solution was transferred to a sand mill and ground for four hours. The mixed solution was spray dried at an inlet temperature of 220°C and an outlet temperature of 100°C to form a dry powder precursor. The mixture was carbonized in a vacuum tube furnace using a one-step calcination method, that is, in an inert gas atmosphere, the mixture was heated to 650°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, then cooled naturally to room temperature, removed from the furnace, and ground for 10 to 20 minutes to obtain Na4Fe2.9 Y 0.1 (PO4)2(P2O7) positive electrode material.

[0094] 0.2 g of the positive electrode material synthesized in Examples 1-6 and Comparative Examples 1-13, 0.025 g of a PVDF binder, and 0.025 g of a Ketjen black conductive agent were weighed in a weight ratio of 8:1:1, and an appropriate amount of NMP solvent was added dropwise to prepare a slurry. The slurry was coated on aluminum foil, dried, and then cut into electrode discs, which were assembled into CR2025 button cells for electrochemical performance testing. The test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0099] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing a composite positive electrode material, characterized in that: include: According to the chemical formula of Na4Fe3(PO4)2(P2O7), Na, Fe, PO4 3- and P2O7 4- The molar ratio of Na4P2O7, Fe(NO3)3·9H2O and NH4H2PO4 were weighed respectively, and yttrium salt and deionized water were added and mixed uniformly to obtain a mixed solution; wherein, Y 3+ With P2O7 4- The molar ratio is 0.1:1; the yttrium salt is Y2(CO3)3; The mixed solution is ground and then spray-dried at an inlet temperature of 220-250° C. and an outlet temperature of 85-100° C. to form a dry powder precursor; The powder precursor is ground and then heated to 580° C. at a heating rate of 2° C. / min in an inert gas atmosphere for sintering to obtain a composite positive electrode material.

2. The method for preparing a composite positive electrode material according to claim 1, wherein: The mixed solution is ground to a particle size of no more than 100 nm.

3. The method for preparing a composite positive electrode material according to claim 1, wherein: The powder precursor is ground and then heated to 580° C. at a heating rate of 2° C. / min in an inert gas atmosphere for sintering to obtain a composite positive electrode material, comprising: The powder precursor is ground, heated to 580° C. at a heating rate of 2° C. / min in an inert gas atmosphere for sintering, kept at this temperature for 10-15 hours, naturally cooled to room temperature, and ground to obtain a composite positive electrode material.

4. A composite positive electrode material, characterized in that The composite positive electrode material is prepared by the method for preparing the composite positive electrode material according to any one of claims 1 to 3.

5. A sodium ion battery, characterized in that: The sodium ion battery comprises the composite positive electrode material according to claim 4.

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