Alumina-coated manganese-titanium co-doped polyanion composite material as well as preparation method and application thereof

Abstract

The invention relates to the field of batteries, in particular to an aluminum oxide coated manganese-titanium co-doped polyanion composite material as well as a preparation method and application thereof. The chemical formula of the aluminum oxide coated manganese-titanium co-doped polyanion composite material is Na4Fe3-x-yMnxTiy (PO4) 2P2O7 / Al2O3, x is larger than or equal to 0.05 and smaller than or equal to 0.2, and y is larger than or equal to 0.02 and smaller than or equal to 0.1. According to the invention, an NFPP material is used as a matrix, manganese and titanium are doped at the same time to replace part of iron sites, and crystal structure parameters are directionally adjusted by using atomic radius difference among elements; manganese is combined with an NFPP framework through an ionic bond, titanium forms an oxide nanophase, and manganese and titanium are synergistically strengthened, so that the phase change potential barrier when sodium ions are embedded or separated is reduced, the structural distortion in the charging and discharging process is reduced, a sodium ion transmission channel is optimized, the working voltage of the material is improved, and finally, the conductivity and the energy density of the material are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to an alumina-coated manganese-titanium co-doped polyanionic composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of the energy storage field, problems such as uneven distribution and scarcity of lithium resources are becoming increasingly prominent, making the demand for new energy storage battery technologies more urgent. Sodium-ion batteries, with their advantages of high reserves, low cost, and high safety, have become one of the most promising solutions in the energy storage field, and their industrialization process is gradually accelerating.

[0003] Sodium-ion battery cathode materials generally require high potential, structural stability, and good conductivity. Common cathode materials each have their own advantages and disadvantages. Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7, abbreviated as NFPP), as a polyanionic cathode material, has advantages such as structural stability, high cycle life, and excellent high and low temperature performance. However, NFPP has poor intrinsic conductivity and low energy density, requiring modification to improve its overall electrochemical performance to meet the growing application demands of high-energy-density, long-life sodium-ion batteries.

[0004] Therefore, there is an urgent need for a modified material that can meet the requirements of high specific energy and long lifespan sodium-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing an alumina-coated manganese-titanium co-doped polyanionic composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention is to provide an alumina-coated manganese-titanium co-doped polyanionic composite material with the chemical formula Na₄Fe₂O₃. 3-x-y Mn x Ti y (PO4)2P2O7 / Al2O3, where 0.05≤x≤0.2, 0.02≤y≤0.1.

[0008] Preferably, the particle size is 50-400 nm.

[0009] Preferably, in the alumina-coated manganese-titanium co-doped polyanionic composite material, Fe has a +2 valence, Mn has a +2 valence, and Ti has a +4 valence.

[0010] A second aspect of the present invention is to provide a method for preparing the above-mentioned alumina-coated manganese-titanium co-doped polyanionic composite material, comprising the steps of:

[0011] S1. Weigh out sodium source, iron source, phosphorus source, manganese source and titanium source, mix and dissolve in water, and then perform wet ball milling and spray drying treatment in sequence to obtain the precursor.

[0012] S2. The precursor is sintered to obtain a manganese-titanium co-doped polyanionic composite material.

[0013] S3. Weigh the aluminum source and dilute acid, mix them, and then pulverize and activate them to obtain the pretreated aluminum source.

[0014] S4. The pretreated aluminum source is mixed with the manganese-titanium co-doped polyanionic composite material, and then subjected to calcination and annealing treatment in sequence to obtain the alumina-coated manganese-titanium co-doped polyanionic composite material.

[0015] Preferably, in step S1, the sodium source includes at least one of sodium hydroxide, sodium oxalate, sodium carbonate, sodium sulfate, sodium citrate, sodium nitrate, and sodium acetate;

[0016] The iron source includes at least one of ferrous chloride, ferrous sulfate, ferrous oxalate, ferrous nitrate, and ferrous acetate.

[0017] The phosphorus source includes at least one of sodium dihydrogen phosphate, sodium pyrophosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen pyrophosphate.

[0018] The manganese source includes at least one of manganese dioxide, manganese oxalate, manganese trioxide, manganese sulfate, manganese acetate, and manganese nitrate.

[0019] The titanium source includes at least one of titanium hydroxide, titanium fluoride, titanium tetrachloride, titanium sulfide, titanium carbide, and titanium oxide.

[0020] Preferably, in step S1, the wet ball milling process is performed at a speed of 300-500 rpm for 4-8 hours; the spray drying process is performed at an inlet temperature of 200-300℃ and an outlet temperature of 60-120℃.

[0021] Preferably, in step S2, the sintering treatment includes: pre-sintering by heating to 300-450°C at a heating rate of 2-10°C / min and holding for 2-5 hours, followed by heating to 500-650°C at a heating rate of 2-10°C / min and holding for 7-10 hours.

[0022] Preferably, in step S3, the aluminum source includes at least one of aluminum oxide, aluminum acetate, aluminum nitrate, aluminum propionate, aluminum formate, aluminum oxalate, and aluminum isopropoxide; the dilute acid includes one of nitric acid and boric acid; and the weight ratio of the aluminum source to the dilute acid is (3-5):1.

[0023] Preferably, in step S3, the pulverization time for pulverization activation is 20-30 seconds.

[0024] Preferably, in step S4, the mass of the aluminum source is 0.2-5 wt.% of the manganese-titanium co-doped polyanionic composite material.

[0025] Preferably, in step S4, the calcination treatment includes: heating to 300-600℃ at a heating rate of 2-10℃ / min and holding at that temperature for 4-7 hours; the annealing treatment is performed at a temperature of 300-400℃ for 1-2 hours.

[0026] A third aspect of the present invention is to provide the application of the above-mentioned alumina-coated manganese-titanium co-doped polyanionic composite material in a battery.

[0027] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0028] (1) This invention uses NFPP material as the matrix and replaces part of the iron sites by doping with manganese and titanium at the same time, and uses the difference in atomic radius between elements to adjust the crystal structure parameters in a directional manner. Manganese is combined with the NFPP framework through ionic bonds, and titanium forms an oxide nanophase. The two work together to strengthen the structure, which not only reduces the phase transition barrier when sodium ions are inserted or extracted, and reduces the structural distortion during charging and discharging, but also optimizes the sodium ion transport channel, improves the working voltage of the material, and ultimately significantly improves the conductivity and energy density of the material.

[0029] (2) This invention breaks through the traditional single modification approach and forms a stable SEI film by coating with alumina on the basis of manganese and titanium co-doping. This interface can weaken the variable valence dissolution of manganese and titanium elements, inhibit the side reaction between active materials and electrolyte, reduce interface impedance, and enhance the electronic contact between particles, achieving the dual effect of "structure optimization-interface protection". It solves the contradiction between material conductivity and cycle stability from the root and greatly extends the cycle life of polyanionic composite materials.

[0030] (3) The alumina-coated manganese-titanium co-doped polyanionic composite material provided by the present invention can optimize the material performance by adjusting the manganese-titanium doping ratio and the alumina coating amount. The preparation method is simple and the process is highly controllable. Through the process innovation of "surface activation pretreatment + sintering and annealing", the technical pain point of poor bonding between the NFPP material surface and the coating layer and easy detachment in the traditional alumina coating technology is solved, and the interface stability is enhanced. At the same time, the raw material cost is low and it is easy to scale up production, which is suitable for the industrial demand of high specific energy and long life sodium-ion battery cathode materials. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0033] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0034] Example 1

[0035] This embodiment provides an alumina-coated manganese-titanium co-doped polyanionic composite material and its preparation method, wherein the material has the general formula Na₄Fe₄. 2.93 Mn 0.05 Ti 0.02 (PO4)2P2O7 / Al2O3.

[0036] The preparation steps include:

[0037] S1. Sodium carbonate, ferric nitrate, manganese dioxide, titanium fluoride, and ammonium dihydrogen phosphate were weighed out in water at a molar ratio of 4:2.93:0.05:0.02:3 to obtain a mixed solution. The mixed solution was then subjected to wet ball milling at 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain the precursor.

[0038] S2. The precursor is sintered under nitrogen atmosphere. It is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours for pre-sintering. Then, it is heated to 600℃ at a heating rate of 5℃ / min and held for 8 hours to obtain Na4Fe. 2.93 Mn 0.05 Ti 0.02 (PO4)2P2O7 material;

[0039] S3. Mix the coating material alumina and boric acid at a weight ratio of 4:1, and pulverize them in a high-speed pulverizer for 30 seconds to perform surface activation pretreatment.

[0040] S4. The pretreated alumina is mixed with Na4Fe 2.93 Mn 0.05 Ti 0.02(PO4)2P2O7 material was mixed uniformly at a mass ratio of 0.012:1 and calcined under nitrogen atmosphere. The mixture was heated to 450℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours. Then, it was annealed at 300℃ for 1 hour to obtain Na4Fe. 2.93 Mn 0.05 Ti 0.02 (PO4)2P2O7 / Al2O3 material.

[0041] Example 2

[0042] This embodiment provides another alumina-coated manganese-titanium co-doped polyanionic composite material and its preparation method, the material having the general formula Na4Fe 2.85 Mn 0.1 Ti 0.05 (PO4)2P2O7 / Al2O3.

[0043] The preparation steps include:

[0044] S1. Sodium carbonate, ferric nitrate, manganese dioxide, titanium fluoride, and ammonium dihydrogen phosphate were weighed out in water at a molar ratio of 4:2.85:0.1:0.05:3 to obtain a mixed solution. The mixed solution was then subjected to wet ball milling at 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain the precursor.

[0045] S2. The precursor is sintered under nitrogen atmosphere. It is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours for pre-sintering. Then, it is heated to 600℃ at a heating rate of 5℃ / min and held for 8 hours to obtain Na4Fe. 2.85 Mn 0.1 Ti 0.05 (PO4)2P2O7 material;

[0046] S3. Mix the coating material alumina and boric acid at a weight ratio of 4:1, and pulverize them in a high-speed pulverizer for 30 seconds to perform surface activation pretreatment.

[0047] S4. The pretreated alumina is mixed with Na4Fe 2.85 Mn 0.1 Ti 0.05 (PO4)2P2O7 material was mixed uniformly at a mass ratio of 0.012:1 and calcined under nitrogen atmosphere. The mixture was heated to 450℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours. Then, it was annealed at 300℃ for 1 hour to obtain Na4Fe. 2.85 Mn 0.1 Ti 0.05 (PO4)2P2O7 / Al2O3 material.

[0048] Example 3

[0049] This embodiment provides another alumina-coated manganese-titanium co-doped polyanionic composite material and its preparation method, the material having the general formula Na4Fe 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7 / Al2O3.

[0050] The preparation steps include:

[0051] S1. Sodium carbonate, ferric nitrate, manganese dioxide, titanium fluoride, and ammonium dihydrogen phosphate were weighed out in water at a molar ratio of 4:2.77:0.15:0.08:3 to obtain a mixed solution. The mixed solution was then subjected to wet ball milling at 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain the precursor.

[0052] S2. The precursor is sintered under nitrogen atmosphere. It is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours for pre-sintering. Then, it is heated to 600℃ at a heating rate of 5℃ / min and held for 8 hours to obtain Na4Fe. 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7 material;

[0053] S3. Mix the coating material alumina and boric acid at a weight ratio of 4:1, and pulverize them in a high-speed pulverizer for 30 seconds to perform surface activation pretreatment.

[0054] S4. The pretreated alumina is mixed with Na4Fe 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7 material was mixed uniformly at a mass ratio of 0.012:1 and calcined under nitrogen atmosphere. The mixture was heated to 450℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours. Then, it was annealed at 300℃ for 1 hour to obtain Na4Fe. 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7 / Al2O3 material.

[0055] Comparative Example 1

[0056] This comparative example provides another polyanionic composite material and its preparation method, the material having the general formula Na4Fe3(PO4)2P2O7.

[0057] The preparation steps include:

[0058] S1. Weigh out sodium carbonate, ferric nitrate and ammonium dihydrogen phosphate in a molar ratio of 4:3:3 and dissolve them in water to obtain a mixed solution;

[0059] S2. The mixed solution is subjected to wet ball milling at a speed of 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain precursor powder.

[0060] S3. The precursor powder is pre-sintered and then sintered again under nitrogen atmosphere. First, it is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours. After pre-sintering, it is sintered again, heated to 600℃ at a heating rate of 5℃ / min and held for 8 hours to obtain Na4Fe3(PO4)2P2O7 material.

[0061] Comparative Example 2

[0062] This comparative example provides another polyanionic composite material and its preparation method, the material having the general formula Na₄Fe₄. 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7.

[0063] The preparation steps include:

[0064] S1. Sodium carbonate, ferric nitrate, manganese dioxide, titanium fluoride and ammonium dihydrogen phosphate were weighed out and dissolved in water in a molar ratio of 4:2.77:0.15:0.08:3 to obtain a mixed solution.

[0065] S2. The mixed solution is subjected to wet ball milling at a speed of 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain precursor powder.

[0066] S3. The precursor powder is pre-sintered and then sintered again under nitrogen atmosphere. First, it is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours. After pre-sintering, a second sintering is performed, heating to 600℃ at a heating rate of 5℃ / min and holding for 8 hours to obtain Na4Fe. 2.77 Mn 0.15 Ti 0.08 (PO4)2P2O7 material.

[0067] Comparative Example 3

[0068] This comparative example provides another polyanionic composite material and its preparation method. Compared with Example 3, it does not undergo manganese-titanium co-doping. The general formula of the material is Na4Fe3(PO4)2P2O7 / Al2O3.

[0069] The preparation steps include:

[0070] S1. Weigh out sodium carbonate, ferric nitrate and ammonium dihydrogen phosphate in a molar ratio of 4:3:3 and dissolve them in water to obtain a mixed solution;

[0071] S2. The mixed solution is subjected to wet ball milling at a speed of 400 rpm for 6 hours, followed by spray drying at an inlet temperature of 260℃ and an outlet temperature of 80℃ to obtain precursor powder.

[0072] S3. The precursor powder is pre-sintered and then sintered again under nitrogen atmosphere. First, it is heated to 350℃ at a heating rate of 5℃ / min and held for 3 hours. After pre-sintering, it is sintered again, heated to 600℃ at a heating rate of 5℃ / min and held for 8 hours to obtain Na4Fe3(PO4)2P2O7 material.

[0073] S4. Mix the coating material alumina and boric acid at a weight ratio of 4:1, and pulverize them in a high-speed pulverizer for 30 seconds to perform surface activation pretreatment.

[0074] S5. The pretreated alumina and Na4Fe3(PO4)2P2O7 material are mixed evenly at a mass ratio of 0.012:1 and calcined under nitrogen. The mixture is heated to 450℃ at a heating rate of 5℃ / min and held for 6 hours.

[0075] S6. After calcination, annealing is performed at 300℃ for 1 hour to obtain Na4Fe3(PO4)2P2O7 / Al2O3 material.

[0076] Detection Examples

[0077] To test the electrochemical performance of the materials, the materials prepared in Examples 1-3 and Comparative Examples 1-3 were assembled into coin cells for electrochemical performance testing. The preparation steps included: weighing the polyanionic composite material, conductive agent, and polyvinylidene fluoride binder in a mass ratio of 8:1:1, adding an appropriate amount of N-methylpyrrolidone, stirring evenly, coating the slurry onto carbon-coated aluminum foil, and then drying, rolling, and cutting the foil sequentially to obtain the positive electrode sheet; assembling the foil in the order of positive electrode shell, the positive electrode sheet, the first electrolyte, the separator, the second electrolyte, the sodium sheet, the gasket, and the negative electrode shell, and sealing the foil using a sealing press to obtain the coin cell.

[0078] The charge-discharge performance of the sodium-ion batteries described in Examples 1-3 and Comparative Examples 1-3 was tested at a rate of 1C and a voltage range of 1.5-3.6V. The test results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As shown in Table 1, the sodium-ion batteries prepared in Examples 1-3 all maintained an initial discharge specific capacity of over 110 mAh / g, an initial coulombic efficiency of over 95%, and a capacity retention of over 90% after 100 cycles. Among them, Na₄Fe₂O₃ was used... 2.77 Mn 0.15 Ti 0.08 The sodium-ion battery made from the (PO4)2P2O7 / Al2O3 material exhibits the best charge-discharge performance, with an initial discharge specific capacity of 120.1 mAh / g and a capacity retention of 95.9% after 100 cycles. In contrast, the sodium-ion battery prepared in Comparative Example 1, where the polyanionic composite material was not co-doped with manganese and titanium or coated with alumina, had an initial discharge specific capacity of only 96.8 mAh / g and a capacity retention of only 83.6% after 100 cycles. This further demonstrates that the polyanionic composite material prepared by the present invention through manganese and titanium co-doping and alumina coating has superior electrochemical performance, and the sodium-ion battery prepared using it has high specific capacity and cycle stability.

[0082] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. An alumina-coated manganese-titanium co-doped polyanionic composite material, characterized in that, The chemical formula is Na₄Fe 3-x- y Mn x Ti y (PO4)2P2O7 / Al2O3, where 0.05≤x≤0.2, 0.02≤y≤0.

1.

2. The alumina-coated manganese-titanium co-doped polyanionic composite material according to claim 1, characterized in that, The particle size is 50-400nm.

3. A method for preparing an alumina-coated manganese-titanium co-doped polyanionic composite material as described in any one of claims 1-2, characterized in that the steps... include: S1. Weigh out sodium source, iron source, phosphorus source, manganese source and titanium source, mix and dissolve in water, and then perform wet ball milling and spray drying treatment in sequence to obtain the precursor. S2. The precursor is sintered to obtain a manganese-titanium co-doped polyanionic composite material. S3. Weigh the aluminum source and dilute acid, mix them, and then pulverize and activate them to obtain the pretreated aluminum source. S4. The pretreated aluminum source is mixed with the manganese-titanium co-doped polyanionic composite material, and then subjected to calcination and annealing treatments in sequence to obtain the alumina-coated manganese-titanium co-doped polyanionic composite material.

4. The preparation method according to claim 3, characterized in that, In step S1, the sodium source includes at least one of sodium hydroxide, sodium oxalate, sodium carbonate, sodium sulfate, sodium citrate, sodium nitrate, and sodium acetate. The iron source includes at least one of ferrous chloride, ferrous sulfate, ferrous oxalate, ferrous nitrate, and ferrous acetate. The phosphorus source includes at least one of sodium dihydrogen phosphate, sodium pyrophosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen pyrophosphate. The manganese source includes at least one of manganese dioxide, manganese oxalate, manganese trioxide, manganese sulfate, manganese acetate, and manganese nitrate. The titanium source includes at least one of titanium hydroxide, titanium fluoride, titanium tetrachloride, titanium sulfide, titanium carbide, and titanium oxide.

5. The preparation method according to claim 3, characterized in that, In step S1, the wet ball milling process is performed at a speed of 300-500 rpm for 4-8 hours; the spray drying process is performed at an inlet temperature of 200-300℃ and an outlet temperature of 60-120℃.

6. The preparation method according to claim 3, characterized in that, In step S2, the sintering process includes: heating to 300-450°C at a heating rate of 2-10°C / min and holding for 2-5 hours for pre-sintering, then heating to 500-650°C at a heating rate of 2-10°C / min and holding for 7-10 hours.

7. The preparation method according to claim 3, characterized in that, In step S3, the aluminum source includes at least one of aluminum oxide, aluminum acetate, aluminum nitrate, aluminum propionate, aluminum formate, aluminum oxalate, and aluminum isopropoxide; the dilute acid includes one of nitric acid and boric acid; and the weight ratio of the aluminum source to the dilute acid is (3-5):

1.

8. The preparation method according to claim 3, characterized in that, In step S4, the mass of the aluminum source is 0.2-5 wt.% of the manganese-titanium co-doped polyanionic composite material.

9. The preparation method according to claim 3, characterized in that, In step S4, the calcination treatment includes: heating to 300-600℃ at a heating rate of 2-10℃ / min and holding at that temperature for 4-7 hours; the annealing treatment is performed at a temperature of 300-400℃ for 1-2 hours.

10. The application of an alumina-coated manganese-titanium co-doped polyanionic composite material as described in any one of claims 1-2, or an alumina-coated manganese-titanium co-doped polyanionic composite material prepared by any one of claims 3-9, in a battery.

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