Perovskite oxide coated ferric sodium pyrophosphate composite material as well as preparation method and application thereof

Abstract

The invention relates to a perovskite oxide coated ferric sodium pyrophosphate composite material as well as a preparation method and application thereof. The composite material comprises a base material and a coating layer, the base material is ferric sodium pyrophosphate / carbon; the coating layer is a perovskite oxide, the general formula of the perovskite oxide is ABO3, and A site comprises at least one of La, Ce, Sm, Gd, K, Rb, Cs, Be, Mg, Ca and Ba; b comprises at least one of Co, Mn, Ti, Ni, Fe, Cr and Cu; the mass of the coating layer is 0.5%-10% of the mass of the composite material; the thickness of the coating layer is 10 to 1000 nm; according to the invention, the surface of the sodium ferric phosphate pyrophosphate / carbon matrix material is coated with the perovskite oxide layer, so that the ionic and electronic conductivity and stability of the sodium ferric phosphate pyrophosphate material can be effectively improved, and meanwhile, the modified composite material has excellent rate cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and more specifically, to a perovskite oxide-coated sodium iron phosphate pyrophosphate composite material, and a preparation method and application thereof. Background Art

[0002] Energy and environmental crises have become two long-standing problems in the path of human development. One of the important solutions is to continuously develop new energy storage and power batteries with high energy density and low pollution. The commercialization and large-scale application of lithium-ion batteries also symbolize the practicality of this rocking-chair battery. However, lithium-ion batteries have a high cost due to the gradual scarcity of lithium and cobalt mines, which is not conducive to their large-scale application and long-term development. Therefore, more and more researchers have turned their attention to sodium-ion batteries with excellent performance, lower prices and abundant resources.

[0003] Among them, sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2(P2O7)) of the phosphate system has become one of the most promising positive electrode materials for sodium ion batteries due to its high safety, long life, environmental friendliness and low cost. However, phosphate positive electrode materials have the disadvantages of poor electronic conductivity and ionic conductivity, which affects their fast charging capabilities. In addition, side reactions such as transition metal dissolution in the electrolyte will affect their battery life. Therefore, it is necessary to seek effective modification methods to improve their electrochemical properties. Carbon coating is a low-cost and common improvement method, but its main function is to improve its conductivity while improving stability to a certain extent, but the improvement effect is not significant.

[0004] Therefore, it is particularly important to seek a more effective surface modification to improve the surface ionic and electronic conductivity and stability of sodium iron pyrophosphate positive electrode materials. Summary of the invention

[0005] Based on the above technical problems existing in the prior art, the present invention provides a perovskite oxide-coated sodium iron phosphate pyrophosphate composite material, which uses perovskite oxide as a coating layer, can effectively improve the ionic and electronic conductivity and stability of the sodium iron pyrophosphate material, and the composite material obtained after modification has excellent rate performance and cycle performance.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A perovskite oxide coated sodium iron phosphate pyrophosphate composite material comprises a base material and a coating layer coated on the surface of the base material; the base material is sodium iron phosphate pyrophosphate / carbon; the coating layer is a perovskite oxide, the general formula of the perovskite oxide is ABO3, wherein the A position comprises at least one of La, Ce, Sm, Gd, K, Rb, Cs, Be, Mg, Ca, and Ba; the B position comprises at least one of Co, Mn, Ti, Ni, Fe, Cr, and Cu; the mass of the coating layer is 0.5%-10% of the mass of the composite material; and the thickness of the coating layer is 10-1000nm.

[0008] The solution of the present invention can significantly improve the electron migration and ion diffusion on the surface of the carbon-coated sodium iron phosphate pyrophosphate matrix material by coating the perovskite oxide material, thereby improving its electrochemical reaction rate and achieving excellent fast charging performance. In addition, the perovskite oxide has excellent chemical and electrochemical stability, which can inhibit the occurrence of side reactions such as electrolyte corrosion.

[0009] Specifically, the thickness of the coating layer can be 10nm, 50nm, 100nm, 200nm, 300nm, 1000nm, etc. A carbon coating layer of a certain thickness can significantly improve the electronic and ionic conductivity and stability of the surface of the positive electrode material, thereby improving the rate performance and cycle life of the battery.

[0010] In some embodiments, the carbon mass content of the matrix material is 0.5%-5%, specifically, such as 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0011] The present invention also provides a method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material of any of the above embodiments, the method comprising the following steps:

[0012] S1. Weigh a sodium source, an iron source, a phosphorus source and a carbon source according to chemical measurements, add them into water and mix them evenly to obtain a mixed slurry; spray-dry the mixed slurry, first heat it to 300-400° C. in a first inert atmosphere for pre-sintering, and then heat it to 500-600° C. for sintering to obtain a sodium iron pyrophosphate / carbon matrix material;

[0013] S2, mixing the perovskite oxide with the matrix material obtained in step S1, drying after ball milling, and then placing in a second inert atmosphere, heating to 400-600° C. for sintering to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material.

[0014] In some embodiments, in step S1, during the spray drying process, the nozzle temperature is 150-250°C, the air outlet temperature is 80-140°C; the nozzle diameter is 0.5-2.5 mm, the air source is compressed air, and it is preheated to 80-250°C before entering the spray gun; the spray feed flow rate is 500-6000 mL / h.

[0015] In some embodiments, in step S1, the sodium source is at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, sodium acetate, and sodium citrate.

[0016] In some embodiments, the iron source is at least one of ferric chloride, ferrous oxalate, ferrous oxalate, ferrous sulfate, ammonium ferrous sulfate, diammonium hydrogen phosphate, and phosphoric acid.

[0017] In some embodiments, the phosphorus source is at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid.

[0018] In some embodiments, the carbon source is at least one of soluble starch, cellulose, sucrose, glucose, and ascorbic acid.

[0019] In some embodiments, in step S1 and step S2, the first inert atmosphere and the second inert atmosphere are each independently one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0020] In some embodiments, in step S2, the ball milling rate is 400-800 r / min; and / or, the molar ratio of the matrix material to the perovskite oxide is 1:0.005-0.1.

[0021] The present invention also provides a positive electrode material, which includes the composite material described in any one of the above or the composite material obtained by the preparation method of any one of the above embodiments.

[0022] The present invention also provides a positive electrode, which comprises the positive electrode material mentioned above.

[0023] The present invention also provides an electrochemical energy storage device, which includes the above-mentioned positive electrode.

[0024] Specifically, the electrochemical energy storage device includes a sodium ion battery, a sodium ion capacitor, and the like.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention coats the surface of the carbon-coated sodium iron phosphate pyrophosphate material with a perovskite oxide material to improve the electrochemical performance of the carbon-coated sodium iron phosphate pyrophosphate material, so that the obtained composite material exhibits excellent rate performance and stability. On the one hand, the chemical and electrochemical properties of the perovskite oxide are better than those of the carbon layer, which can effectively prevent the erosion of the electrolyte, and the bonding between the perovskite and the matrix material will further inhibit the dissolution of the transition metal on the surface of the matrix material, thereby significantly improving the structural stability of the composite material, thereby improving its cycle stability; on the other hand, the nano perovskite forms a built-in electric field on the surface of the matrix material, thereby forming surface electron accumulation, and finally realizing the rapid transmission of surface electrons and ions, thereby exhibiting excellent rate performance.

[0027] The perovskite oxide-coated sodium iron phosphate pyrophosphate composite material obtained by the preparation method of the present invention is applied to an electrochemical energy storage device and exhibits excellent rate performance and cycle stability. In addition, the preparation method of the present invention has a simple process, the perovskite oxide coating layer is evenly distributed, has high versatility, is suitable for industrial application, and is helpful to promote the industrialization and application of iron-based sodium phosphate ion positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the SEM morphology of the barium titanate-coated sodium iron phosphate pyrophosphate composite material obtained in Example 1. DETAILED DESCRIPTION

[0029] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0031] Example 1

[0032] A method for preparing a perovskite oxide-coated sodium iron phosphate pyrophosphate composite material comprises the following steps:

[0033] S1. Add 490g of sodium dihydrogen phosphate, 460g of ferrous oxalate dihydrate, 100g of citric acid and 20g of thiourea into 3L of deionized water, stir in a ball mill, and stir at a speed of 500rpm for 3h to obtain a slurry; transport the slurry to a spray dryer through a peristaltic pump, with a feed rate of 2500ml / h, an inlet air temperature of 200°C, and an outlet air temperature of 130°C to obtain dry particles; in a nitrogen atmosphere, heat to 350°C at a rate of 5°C / min for sintering for 4h, and then heat to 550°C at a rate of 5°C / min for secondary sintering for 5h to obtain a sodium iron pyrophosphate / C matrix material;

[0034] S2. Mix 10g of barium titanate with 500g of sodium iron phosphate pyrophosphate / C matrix material, stir and ball-mill at 500rpm for 1h, place in a vacuum drying oven at 80°C for 5h, then place in a nitrogen atmosphere, heat to 550°C at a rate of 5°C / min and sinter for 2h to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate positive electrode material.

[0035] The composite material obtained in this example was tested by scanning electron microscopy. The test results are as follows: Figure 1 As shown, it can be seen that nano-barium titanate is obviously coated on the surface of the sodium iron pyrophosphate / C matrix material.

[0036] After testing, as shown in Table 1, the discharge specific capacity of the composite material obtained in this embodiment at a voltage of 1.7-4.3 V and a current density of 0.5 C is 90 mAh / g.

[0037] The composite material obtained in this example has a discharge capacity retention rate of 99% after 100 cycles at a voltage of 1.7-4.3 V and a current density of 0.5 C.

[0038] Comparative Example 1

[0039] A perovskite oxide coated sodium iron phosphate pyrophosphate positive electrode material and a preparation method thereof, comprising the following steps:

[0040] S1. Add 490g of sodium dihydrogen phosphate, 460g of ferrous oxalate dihydrate, 100g of citric acid and 20g of thiourea into 3L of deionized water, stir in a ball mill, and stir at a speed of 500rpm for 3h to obtain a slurry; transport the slurry to a spray dryer through a peristaltic pump, with a feed rate of 2500ml / h, an inlet air temperature of 200°C, and an outlet air temperature of 130°C to obtain dry particles; in a nitrogen atmosphere, heat to 350°C at a rate of 5°C / min for sintering for 4h, and then heat to 550°C at a rate of 5°C / min for secondary sintering for 5h to obtain a sodium iron pyrophosphate / C matrix material;

[0041] S2. Mix 30 g of barium titanate with 500 g of sodium iron phosphate pyrophosphate / C matrix material, stir and ball-mill at 500 rpm for 1 h, place in a vacuum drying oven at 80°C for 5 h, then place in nitrogen, heat to 550°C at a rate of 5°C / min and sinter for 2 h to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate positive electrode material.

[0042] After testing, as shown in Table 1, the composite material obtained in this comparative example has a discharge specific capacity of 82 mAh / g at a voltage of 1.7-4.3 V and a current density of 0.5 C.

[0043] The composite material obtained in this comparative example has a discharge capacity retention rate of 89% after 100 cycles at a voltage of 1.7-4.3V and a current density of 0.5C.

[0044] Comparative Example 2

[0045] A perovskite oxide coated sodium iron phosphate pyrophosphate positive electrode material and a preparation method thereof, comprising the following steps:

[0046] S1. Add 490g of sodium dihydrogen phosphate, 460g of ferrous oxalate dihydrate, 100g of citric acid and 20g of thiourea into 3L of deionized water, stir in a ball mill, and stir at a speed of 500rpm for 3h to obtain a slurry; transport the slurry to a spray dryer through a peristaltic pump, with a feed rate of 2500ml / h, an inlet air temperature of 200°C, and an outlet air temperature of 130°C to obtain dry particles; in a nitrogen atmosphere, heat to 350°C at a rate of 5°C / min for sintering for 4h, and then heat to 550°C at a rate of 5°C / min for secondary sintering for 5h to obtain a sodium iron pyrophosphate / C matrix material;

[0047] S2. Mix 3 g of barium titanate with 500 g of sodium iron phosphate pyrophosphate / C matrix material, stir and ball-mill at 500 rpm for 1 h, place in a vacuum drying oven at 80°C for 5 h, then place in a nitrogen atmosphere, heat to 550°C at a rate of 5°C / min and sinter for 2 h to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate positive electrode material.

[0048] After testing, as shown in Table 1, the composite material obtained in this comparative example has a discharge specific capacity of 85 mAh / g at a voltage of 1.7-4.3 V and a current density of 0.5 C.

[0049] The composite material obtained in this comparative example has a discharge capacity retention rate of 84% after 100 cycles at a voltage of 1.7-4.3V and a current density of 0.5C.

[0050] Example 2

[0051] A perovskite oxide coated sodium iron phosphate pyrophosphate positive electrode material and a preparation method thereof, comprising the following steps:

[0052] S1. Add 490g of sodium dihydrogen phosphate, 460g of ferrous oxalate dihydrate, 100g of citric acid and 20g of thiourea into 3L of deionized water, stir in a ball mill, and stir at a speed of 500rpm for 3h to obtain a slurry; transport the slurry to a spray dryer through a peristaltic pump, with a feed rate of 2500ml / h, an inlet air temperature of 200°C, and an outlet air temperature of 130°C to obtain dry particles; in a nitrogen atmosphere, heat to 350°C at a rate of 5°C / min for sintering for 4h, and then heat to 550°C at a rate of 5°C / min for secondary sintering for 5h to obtain a sodium iron pyrophosphate / C matrix material;

[0053] S2. 10 g of strontium manganate was mixed with 500 g of sodium iron phosphate pyrophosphate / C matrix material, and the mixture was stirred for 1 h in a ball mill at 500 rpm and dried in a vacuum drying oven for 5 h. The mixture was then placed in a nitrogen atmosphere and heated to 550° C. at a rate of 5° C. / min and sintered for 2 h to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate positive electrode material.

[0054] After testing, as shown in Table 1, the discharge specific capacity of the composite material obtained in this embodiment at a voltage of 1.7-4.3 V and a current density of 0.5 C is 88 mAh / g.

[0055] The composite material obtained in this embodiment has a discharge capacity retention rate of 97% after 100 cycles at a voltage of 1.7-4.3V and a current density of 0.5C.

[0056] Table 1 Discharge capacity and capacity retention rate of different samples after first cycle and cycle

[0057]

[0058] It can be seen from Table 1 that the present invention can effectively improve the capacity density and cycle stability of the sodium iron pyrophosphate material by specifically modifying the coating layer, thereby improving the electrochemical performance of the composite material.

[0059] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A perovskite oxide-coated sodium iron phosphate pyrophosphate composite material, characterized in that: The invention comprises a base material and a coating layer coated on the surface of the base material; the base material is sodium iron phosphate pyrophosphate / carbon; the coating layer is a perovskite oxide, and the general formula of the perovskite oxide is ABO3, wherein the A position comprises at least one of La, Ce, Sm, Gd, K, Rb, Cs, Be, Mg, Ca, and Ba; the B position comprises at least one of Co, Mn, Ti, Ni, Fe, Cr, and Cu; the mass of the coating layer is 0.5%-10% of the mass of the composite material; and the thickness of the coating layer is 10-1000nm.

2. The perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 1, characterized in that: The carbon mass content of the matrix material is 0.5%-5%.

3. The method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 1 or 2, characterized in that: The following steps are involved: S1. Weigh a sodium source, an iron source, a phosphorus source and a carbon source according to chemical measurements, add them into water and mix them evenly to obtain a mixed slurry; spray-dry the mixed slurry, first heat it to 300-400° C. in a first inert atmosphere for pre-sintering, and then heat it to 500-600° C. for sintering to obtain a sodium iron pyrophosphate / carbon matrix material; S2, mixing the perovskite oxide with the matrix material obtained in step S1, drying after ball milling, and then placing in a second inert atmosphere, heating to 400-600° C. for sintering to obtain the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material.

4. The method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 3, characterized in that: In step S1, during the spray drying process, the Jinfeng temperature is 150-250°C, the air outlet temperature is 80-140°C; the nozzle diameter is 0.5-2.5mm, the air source is compressed air, and it is preheated to 80-250°C before entering the spray gun; the spray feed flow rate is 500-6000mL / h.

5. The method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 3, characterized in that: In step S1, the sodium source is at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, sodium acetate, and sodium citrate; and / or the iron source is at least one of ferric chloride, ferrous oxalate, ferrous oxalate, ferrous sulfate, ammonium ferrous sulfate, diammonium hydrogen phosphate, and phosphoric acid; and / or the phosphorus source is at least one of diammonium hydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid; and / or the carbon source is at least one of soluble starch, cellulose, sucrose, glucose, and ascorbic acid.

6. The method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 3, characterized in that: In step S1 and step S2, the first inert atmosphere and the second inert atmosphere are each independently one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

7. The method for preparing the perovskite oxide-coated sodium iron phosphate pyrophosphate composite material according to claim 3, characterized in that: In step S2, the ball milling rate is 400-800 r / min; and / or the molar ratio of the matrix material to the perovskite oxide is 1:0.005-0.

1.

8. A positive electrode material, characterized in that The invention comprises the composite material according to claim 1 or 2 or the composite material obtained by the preparation method according to any one of claims 3 to 7.

9. A positive electrode, characterized in that Comprising the positive electrode material as claimed in claim 8.

10. An electrochemical energy storage device, characterized in that: Comprising the positive electrode as claimed in claim 9.

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