Zr < 4 + > double-doped vanadium manganese sodium phosphate positive electrode material and preparation method thereof

Abstract

The invention discloses a Zr < 4 + > double-doped vanadium manganese sodium phosphate positive electrode material and a preparation method thereof. Zr < 4 + > is simultaneously doped to the manganese site and the vanadium site of sodium vanadium manganese phosphate Na4MnV (PO4) 3 through a sol-gel method combined with a high-temperature roasting method, and the sodium ion battery positive electrode material Zr < 4 + > double-doped sodium vanadium manganese phosphate Na < 4-3x > Mn < 1-x > Zr < x > V < 1-x > Zr < x > (PO4) 3 (0 lt, x is smaller than or equal to 0.1) is obtained. Zr < 4 + > is introduced into a sodium vanadium manganese phosphate lattice structure, so that the ginger-Taylor effect of Mn < 3 + > can be weakened, V can be inhibited from being migrated to a sodium layer from a transition metal layer, the purposes of improving the stability of a crystal structure and expanding a sodium ion diffusion channel are achieved, the diffusion rate of sodium ions is further remarkably improved, the stability of the crystal structure is maintained, and the service life of the sodium vanadium manganese phosphate is prolonged. And the rate capability and the cycle performance of the vanadium manganese sodium phosphate are obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials and particularly relates to a Zr 4+ Double-doped sodium vanadium manganese phosphate positive electrode material and preparation method thereof. Background Art

[0002] In recent years, the use of clean and renewable energy and the popularization of electrification of lifestyles have greatly promoted the human society's demand for low-cost and high-energy-density rechargeable batteries. As a rechargeable battery, lithium-ion batteries are widely used in portable electronic products, power tools, and electric vehicles due to their long service life and high energy density. However, limited and expensive lithium resources have seriously hindered the widespread application of lithium-ion batteries. Another type of sodium-ion battery with a similar energy storage mechanism to lithium-ion batteries has attracted widespread attention from a large number of scientific researchers and the industrial community due to its wide distribution of sodium resources, abundant reserves and low cost. It has become a research hotspot for rechargeable batteries and is a new type of rechargeable battery with great application prospects.

[0003] At present, the development of sodium-ion batteries is restricted by its disadvantages of low energy density and poor cycle stability. Therefore, exploring sodium-ion battery electrode materials with high energy density, high power density and good stability has always been one of the hot spots in sodium-ion battery research. The specific capacity of sodium-ion batteries depends largely on the cathode materials with low capacity, so the development of potential cathode materials is the key to the development of sodium-ion batteries. Cathode materials are generally divided into Prussian blue analogs, layered metal oxides, organic compounds and polyanion compounds. Among them, polyanion compounds have been widely studied due to their good structural and thermodynamic stability, high ionic conductivity and high safety. Sodium vanadium phosphate (Na3V2(PO4)3) is a polyanion compound electrode material that has been studied more deeply at present, with good cycle stability and high working voltage. However, the expensive and toxic vanadium resources limit the widespread application of sodium vanadium phosphate. Sodium vanadium manganese phosphate (Na4MnV(PO4)3), which is obtained by partially replacing V with cheap and environmentally friendly Mn elements, has more advantages in terms of environmental friendliness, cost and energy density. The present invention simultaneously adds Zr at the manganese position and vanadium position of Na4MnV(PO4)3. 4+ Double doping can weaken the Mn 3+ The Jahn-Taylor effect can inhibit the migration of V from the transition metal layer to the sodium layer, expand the lattice volume of the material and improve the structural stability, thereby improving the electrochemical performance of sodium vanadium manganese phosphate. Summary of the invention

[0004] The purpose of the present invention is to provide a Zr vanadium manganese phosphate anode material for sodium ion batteries with poor cycle performance. 4+Preparation method for improving electrochemical performance of sodium manganese vanadium phosphate cathode material by double doping. This method has a simple process, and the prepared sodium manganese vanadium phosphate has the advantages of long cycle life, excellent high-current performance, high capacity, etc., significantly improving the electrochemical performance of sodium manganese vanadium phosphate.

[0005] Zr involved in the present invention 4+ The molecular formula of the double-doped sodium manganese vanadium phosphate is Na 4-3x Mn 1-x Zr x V 1-x Zr x (PO4)3 (0 < x ≤ 0.1). The specific steps of the preparation method of the Zr 4+ double-doped sodium manganese vanadium phosphate are as follows:

[0006] (1) Weigh the sodium source compound, vanadium source compound, manganese source compound, zirconium source compound, and phosphorus source compound according to the molar ratio of Na:V:Mn:Zr:(PO4)3 = (4 - 3x):(1 - x):(1 - x):2x:3 (0 < x ≤ 0.1), and dissolve them in a certain amount of complexing agent aqueous solution (where the molar ratio of the complexing agent to vanadium is 1.2 - 2.2), and obtain a precursor gel under the action of the complexing agent and the condition of heating the solution;

[0007] (2) After drying the precursor gel in (1), place it under an inert atmosphere and perform roasting. Heat it at a heating rate of 2 - 10 °C / min to 350 °C, and roast for 3 - 7 hours, then heat it at a heating rate of 2 - 10 °C / min to 650 °C - 850 °C, and keep it at a constant temperature for 8 - 12 hours, and then naturally cool it to room temperature to obtain Na 4-3x Mn 1-x Zr x V 1-x Zr x (PO4)3 material.

[0008] The sodium source is one or more of sodium hydroxide, sodium acetate, sodium nitrate, sodium carbonate, sodium citrate, and sodium bicarbonate;

[0009] The vanadium source is one or more of vanadium pentoxide, ammonium metavanadate, and vanadium trioxide;

[0010] The manganese source is one or more of manganese nitrate, manganese acetate, and manganese chloride;

[0011] The zirconium source is one or more of zirconium chloride, zirconium nitrate, zirconium acetate, and zirconium carbonate;

[0012] The complexing agent is one or more of citric acid, sodium citrate, ammonium citrate, tartaric acid, oxalic acid, and ethylenediaminetetraacetic acid;

[0013] The phosphorus source is one or more of diammonium phosphate, diammonium hydrogen phosphate, ammonium phosphate, phosphorus pentoxide, phosphoric acid and sodium dihydrogen phosphate;

[0014] The inert atmosphere is one or both of nitrogen and argon.

[0015] The present invention allows water-soluble substances such as vanadium source compounds, manganese source compounds, zirconium source compounds, sodium source compounds, and phosphorus source compounds to react with complexing agents to form reaction raw materials that are evenly dispersed at the molecular level. The preparation process is simple, the time required is short, and a product with a smaller particle size is obtained. After high-temperature roasting, the in-situ formed carbon coating is beneficial to enhancing the electronic conductivity and inhibiting the growth of material particles. 4+ The dual doping of Mn and V in sodium manganese vanadium phosphate can weaken the 3+ The Jahn-Taylor effect can inhibit the migration of V from the transition metal layer to the sodium layer, thereby improving the stability of the crystal structure and expanding the sodium ion diffusion channel, so that the doped sodium manganese vanadium phosphate has excellent high current and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The Zr prepared in Example 1 of the present invention 4+ XRD pattern of dual-doped sodium manganese vanadium phosphate.

[0017] Figure 2 It is Zr prepared in Example 2 of the present invention. 4+ XRD pattern of dual-doped sodium manganese vanadium phosphate.

[0018] Figure 3 The Zr prepared in Example 3 of the present invention 4+ The first charge and discharge curve of dual-doped sodium manganese vanadium phosphate at 0.5C.

[0019] Figure 4 It is Zr prepared in Example 2 of the present invention. 4+ Cycling performance curve of dual-doped sodium manganese vanadium phosphate at 1C. DETAILED DESCRIPTION

[0020] Embodiment 1:

[0021] (1) Dissolve 0.5761 g ammonium metavanadate, 1.2071 g manganese acetate tetrahydrate, 0.03496 g zirconium chloride, 1.7255 g ammonium dihydrogen phosphate, 1.6221 g sodium acetate, and 2.2769 g citric acid in 40 ml deionized water to prepare a mixed saline solution. Place the solution in a constant temperature water bath at 80 °C and stir continuously until a blue gel is formed. Then transfer the blue gel to a refrigerator and freeze it into ice cubes. Then, dry the ice cubes in a vacuum freeze dryer at -46 °C for 72 hours.

[0022] (2) The dry gel obtained in step (1) was heated to 350°C at a heating rate of 3°C / min in an argon atmosphere and calcined for 6 hours, then heated to 650°C at a heating rate of 5°C / min and calcined for 12 hours, and then naturally cooled to room temperature in the furnace to obtain Na 3.955 Mn 0.985 Zr 0.015 V 0.985 Zr 0.015 (PO4)3 / C composite materials.

[0023] The positive electrode material Na 3.955 Mn 0.985 Zr 0.015 V 0.985 Zr 0.015 (PO4)3 / C, conductive agent Super P and binder PVDF were evenly mixed in an agate mortar at a mass ratio of 8:1:1, and an appropriate amount of NMP solution was added to form an electrode slurry. After stirring evenly, it was evenly coated on aluminum foil and placed in a 120°C forced air oven to dry. After the electrode was dried, it was cut into 12 mm disc electrodes, rolled and weighed. The obtained electrode was used as the positive electrode, metallic sodium as the negative electrode, and the separator was glass fiber. A CR2016 button battery was assembled in a high-purity argon glove box (the moisture and oxygen content were both less than 0.1ppm). The Xinwei test system was used at 25°C (voltage range was 2.5~3.8V (vs. Na + / Na)) for constant current charge and discharge test. The Na prepared by the method of the present invention 3.955 Mn 0.985 Zr 0.015 V 0.985 Zr 0.015 The first cycle discharge capacity of the (PO4)3 / C sodium ion battery positive electrode material at 1C is 88.2 mAh / g, and the discharge capacity after 50 cycles is 75.5 mAh / g, with a retention rate of 83.4%.

[0024] Embodiment 2:

[0025] (1) Dissolve 0.5703 g of ammonium metavanadate, 0.8093 g of manganese nitrate, 0.058259 g of zirconium chloride, 1.7255 g of diammonium phosphate, 1.6098 g of sodium acetate and 1.6391 g of citric acid in 35 ml of deionized water and place in a constant temperature water bath at 90 °C. Stir the solution continuously until a blue gel is formed. Then transfer the blue gel to a refrigerator and freeze it into ice cubes. Then, dry the ice cube gel in a vacuum freeze dryer at -46 °C for 72 hours.

[0026] (2) The dry gel obtained in step (1) was heated to 350°C in an argon atmosphere at a heating rate of 5°C / min and calcined for 5 hours, then heated to 750°C at a heating rate of 5°C / min and calcined for 12 hours, and then naturally cooled to room temperature in the furnace to obtain Na 3.925 Mn 0.975 Zr 0.025 V 0.975 Zr 0.025 (PO4)3 composite materials.

[0027] The positive electrode material Na 3.925 Mn 0.975 Zr 0.025 V 0.975 Zr 0.025 (PO4)3, conductive agent Super P and binder PVDF were evenly mixed in an agate mortar at a mass ratio of 8:1:1, and an appropriate amount of NMP solution was added to form an electrode slurry. After stirring evenly, it was evenly coated on aluminum foil and placed in a 120°C forced air oven for drying. After the electrode was dried, it was cut into 12 mm disc electrodes, rolled and weighed. The obtained electrode was used as the positive electrode, metallic sodium as the negative electrode, and the diaphragm was glass fiber. They were assembled into CR2016 button batteries in a high-purity argon glove box (moisture and oxygen content were both less than 0.1ppm). The Xinwei test system was used at 25°C (voltage range was 2.5~3.8V (vs Na + / Na)) for constant current charge and discharge test. The Na prepared by the method of the present invention 3.925 Mn 0.975 Zr 0.025 V 0.975 Zr 0.025 The first-cycle discharge capacity of (PO4)3 at 1C is 95.7 mAh / g, and the discharge capacity after 50 cycles is still as high as 94.6 mAh / g, with a capacity retention rate of 98.8%.

[0028] Embodiment 3:

[0029] (1) Dissolve 0.4388 g of vanadium pentoxide, 0.9549 g of manganese chloride tetrahydrate, 0.08156 g of zirconium chloride, 1.7255 g of ammonium dihydrogen phosphate, 1.5975 g of sodium acetate and 1.2167 g of citric acid in 45 ml of deionized water, place in a constant temperature water bath at 85 °C, and continue stirring until a blue gel is formed. Then, transfer the blue gel to a refrigerator and freeze it into ice cubes. Then, dry the ice cube gel in a vacuum freeze dryer at -46 °C for 72 hours.

[0030] (2) The dry gel obtained in step (1) was heated to 350°C in an argon atmosphere at a heating rate of 5°C / min and calcined for 6 hours, then heated to 850°C at a heating rate of 5°C / min and calcined for 11 hours, and then naturally cooled to room temperature in the furnace to obtain Na 3.895 Mn 0.965 Zr 0.035 V 0.965 Zr 0.035 (PO4)3 composite materials.

[0031] The positive electrode material Na 3.925 Mn 0.975 Zr 0.025 V 0.975 Zr 0.025 (PO4)3, conductive agent Super P and binder PVDF were evenly mixed in an agate mortar at a mass ratio of 8:1:1, and an appropriate amount of NMP solution was added to form an electrode slurry. After stirring evenly, it was evenly coated on aluminum foil and placed in a 120°C forced air oven for drying. After the electrode was dried, it was cut into 12 mm disc electrodes, rolled and weighed. The obtained electrode was used as the positive electrode, metallic sodium as the negative electrode, and the diaphragm was glass fiber. They were assembled into CR2016 button batteries in a high-purity argon glove box (moisture and oxygen content were both less than 0.1ppm). The Xinwei test system was used at 25°C (voltage range was 2.5~3.8V (vs Na + / Na)) for constant current charge and discharge test. The Na prepared by the method of the present invention 3.895 Mn 0.965 Zr 0.035 V 0.965 Zr 0.035 The first-cycle discharge capacity of (PO4)3 at 1C is 88.7 mAh / g, and the discharge capacity after 50 cycles is still as high as 87.1 mAh / g, with a capacity retention rate of 98.2%.

[0032] Since there are many implementation schemes of the present invention, they are not listed here one by one. Without violating the spirit and essence of the present invention, technicians familiar with the field can make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A Zr 4+ The double-doped sodium manganese vanadium phosphate positive electrode material is characterized by: The Zr 4+ The molecular formula of the dual-doped sodium manganese vanadium phosphate is Na 4-3x Mn 1-x Zr x V 1-x Zr x (PO4)3, where 0 <x≤0.1。 2. Zr as claimed in claim 1 4+ The preparation method of the dual-doped sodium manganese vanadium phosphate positive electrode material is characterized in that: The specific steps are as follows: (1) Weigh a sodium source compound, a vanadium source compound, a manganese source compound, a zirconium source compound, and a phosphorus source compound according to the molar ratio of Na:V:Mn:Zr:(PO4)3 = (4 - 3x):(1 - x):(1 - x):2x:3 (0 < x ≤ 0.1), and dissolve them in a certain amount of aqueous solution of a complexing agent (where the molar ratio of the complexing agent to vanadium is 1.2 - 2.2). Under the action of the complexing agent and the condition of heating the solution, a precursor gel is obtained; (2) After drying the precursor gel described in (1), place it in an inert atmosphere and calcine it, heat it to 350 °C at a heating rate of 2-10 °C / min, and calcine it for 3-7 hours, then heat it to 650 °C-850 °C at a heating rate of 2-10 °C / min, and keep the temperature constant for 8-12 hours, and then cool it naturally to room temperature to obtain Na 4-3x Mn 1-x Zr x V 1-x Zr x (PO4)3 material.

3. The preparation method according to claim 2, characterized in that: The sodium source is one or more of sodium hydroxide, sodium acetate, sodium nitrate, sodium carbonate, sodium citrate, and sodium bicarbonate.

4. The preparation method according to claim 2, characterized in that: The vanadium source is one or more of vanadium pentoxide, ammonium metavanadate, and vanadium trioxide.

5. The preparation method according to claim 2, characterized in that: The manganese source is one or more of manganese nitrate, manganese acetate, and manganese chloride.

6. The preparation method according to claim 2, characterized in that: The zirconium source is one or more of zirconium chloride, zirconium nitrate, zirconium acetate, and zirconium carbonate.

7. The preparation method according to claim 2, characterized in that: The complexing agent is one or more of citric acid, sodium citrate, ammonium citrate, tartaric acid, oxalic acid, and ethylenediaminetetraacetic acid.

8. The preparation method according to claim 2, characterized in that: The phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, phosphorus pentoxide, phosphoric acid, and sodium dihydrogen phosphate.

9. The preparation method according to claim 2, characterized in that: The inert atmosphere is one or both of nitrogen and argon.

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