Preparation method and application of in-situ synergistic modified sodium manganese vanadium phosphate electrode material

Abstract

The invention discloses a preparation method of an in-situ synergistic modified sodium manganese vanadium phosphate electrode material, which comprises the following steps: taking a phosphorus source, a manganese source, a vanadium source, a sodium source and a carbon source as raw materials to obtain a precursor, and adding a modified material to obtain a composite precursor; and calcining in an inert atmosphere to obtain the in-situ synergistically modified manganese vanadium sodium phosphate. The preparation method has the advantages that the precursor is synthesized by a simple solid-phase method, in-situ synergistic modification is performed by a wet chemical method, a fluoride coating layer is constructed on the surface of the sodium manganese vanadium phosphate material, a cation doping effect is achieved, the structural stability of the sodium manganese vanadium phosphate material is enhanced, and the diffusion rate of sodium ions is increased. An electrochemical test result of a battery assembled by the material subjected to in-situ synergistic modification shows that the material has higher capacity retention ratio and long cycle performance, and the electrochemical performance of the sodium manganese vanadium phosphate electrode material is effectively improved.

Description

Technical Field

[0001] The invention relates to a method for preparing an electrode material, in particular to a method for preparing an in-situ synergistically modified sodium manganese vanadium phosphate electrode material and application thereof. Background Art

[0002] In order to adapt to the national new energy development strategy, develop large-scale secondary battery energy storage systems, and avoid uncontrollable resource supply risks, sodium-ion batteries are considered to be one of the most promising alternatives to lithium-based battery technology. Despite the growing research in this field, the implementation of this technology has been hindered by the lack of high-energy-density cathode materials with long cycle life.

[0003] Sodium phosphate containing vanadium is a highly potential cathode material in sodium ion batteries, with the characteristics of fast sodium ion transmission, small volume strain, and stable structure. Sodium manganese vanadium phosphate material doped with manganese has higher energy storage density and longer cycle life, but in actual applications, it has problems such as low first-cycle coulomb efficiency and fast capacity decay, which leads to a serious decline in its overall performance.

[0004] At present, in the prior art, a sodium manganese vanadium phosphate electrode material and its preparation method and application (CN106946238B) mentions that phosphorus, manganese, vanadium, sodium and carbon are used as raw materials for electrode materials, but no modified materials are used to improve the precursor. A method for surface modification of aqueous ion battery electrode materials (CN109975477A) mentions that phosphorus, manganese, vanadium, sodium and carbon are used as raw materials for electrode materials, and also mentions the use of modified materials, but the modified materials are completely different from the present invention and cannot achieve the cation doping effect. The present invention adopts a simple solid phase method to synthesize the precursor, and a wet chemical method to perform in-situ synergistic modification, construct a fluoride coating layer on the surface of the sodium manganese vanadium phosphate material, and achieve the cation doping effect, which is beneficial to enhance the structural stability of the sodium manganese vanadium phosphate material, improve the diffusion rate of sodium ions, improve the capacity retention rate of the sodium manganese vanadium phosphate electrode material, and improve the comprehensive performance of the sodium manganese vanadium phosphate electrode material. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method of an in-situ synergistically modified sodium manganese vanadium phosphate electrode material. The present invention uses a simple wet chemical method to mix potassium tetrafluoroaluminate with a sodium manganese vanadium phosphate precursor, and constructs a fluoride coating layer and a cation-doped synergistically modified sodium manganese vanadium phosphate electrode material in one step in situ through a high-temperature multi-physical field, which is beneficial to enhance the structural stability of the sodium manganese vanadium phosphate material, improve the diffusion rate of sodium ions, improve the capacity retention rate of the sodium manganese vanadium phosphate electrode material, and improve the comprehensive performance of the sodium manganese vanadium phosphate electrode material.

[0006] The technical solution of the present invention is as follows: A method for preparing an in-situ synergistically modified sodium manganese vanadium phosphate electrode material comprises the following steps: (1) mixing a phosphorus source, a manganese source, a vanadium source, a sodium source and a carbon source, and grinding them into uniform fine powder by ball milling to obtain a precursor; The phosphorus source is a compound containing phosphorus element; The manganese source is a compound containing manganese; The vanadium source is a compound containing vanadium; The sodium source is a compound containing sodium; The carbon source is a compound containing carbon element; (2) adding the precursor and the modified material into anhydrous ethanol, stirring and mixing them evenly, and then heating and evaporating the anhydrous ethanol to obtain a composite precursor; (3) After the composite precursor is dried, it is calcined in an inert gas environment to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0007] In the aforementioned step (1), the molar ratio of phosphorus in the phosphorus source, manganese in the manganese source, vanadium in the vanadium source and sodium in the sodium source is 2-4:0.5-1.5:0.5-1.5:3-5, and the amount of carbon source added is 10%-30% of the total mass of the phosphorus source, manganese source, vanadium source and sodium source.

[0008] Specifically, in the aforementioned step (1), the molar ratio of phosphorus in the phosphorus source, manganese in the manganese source, vanadium in the vanadium source and sodium in the sodium source is 3:1:1:4, and the amount of carbon source added is 15%-25% of the total mass of the phosphorus source, manganese source, vanadium source and sodium source.

[0009] In the aforementioned step (2), the modified material is potassium tetrafluoroaluminate, the amount of the modified material added is 1%-5% of the mass of the precursor, and the ratio of anhydrous ethanol to the precursor is 25mL:1g.

[0010] In the above step (3), the drying equipment is a vacuum drying oven, the drying temperature is 80-120°C, and the drying time is 10-14h.

[0011] More specifically, in the aforementioned step (1), the phosphorus source is one or more of ammonium dihydrogen phosphate, phosphoric acid (solid pure phosphoric acid), sodium phosphate, and sodium dihydrogen phosphate; the manganese source is one or more of manganese carbonate, manganese acetate tetrahydrate, manganese sulfate, and manganese dioxide; the vanadium source is one or more of vanadium pentoxide, ammonium metavanadate, and vanadium trioxide; the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium acetate, and sodium oxalate; and the carbon source is one or more of glucose (solid), ascorbic acid, sodium citrate, and sucrose.

[0012] In the above step (2), the stirring time is 3-5 hours, the temperature is raised to 75-85°C, and the temperature is maintained for 3-6 hours after the temperature is raised.

[0013] In the above step (3), the calcination equipment is a tubular furnace, the calcination temperature is 600-800°C, the calcination time is 6-12h, and the inert gas is argon.

[0014] In the above step (1), the ball milling is a drum ball mill or a planetary ball mill; and the ball milling time is 6-12 hours.

[0015] A preparation method and application of an in-situ synergistically modified sodium manganese vanadium phosphate electrode material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Surface coating and element doping are effective methods to improve the electrochemical stability of materials. The present invention provides a preparation method for in-situ synergistically modified sodium manganese vanadium phosphate electrode materials. The present invention adopts a simple solid-phase method to synthesize precursors, a wet chemical method to perform in-situ synergistic modification, constructs a fluoride coating layer on the surface of the sodium manganese vanadium phosphate material, and achieves a cation doping effect, which is beneficial to enhance the structural stability of sodium manganese vanadium phosphate, increase the diffusion rate of sodium ions, and improve the comprehensive performance of the sodium manganese vanadium phosphate electrode.

[0017] 2. Potassium tetrafluoroaluminate is used as a modified material, and the in-situ synergistic modification process is simple and can be promoted. The fluoride coating layer can alleviate the corrosion of the electrolyte on the sodium manganese vanadium phosphate material during the circulation process, reduce the occurrence of surface side reactions, and thus inhibit the structural collapse from the surface to the bulk phase; at the same time, the nail pillar effect of cation doping can stabilize the structure of sodium manganese vanadium phosphate and provide a good diffusion channel for the diffusion of sodium ions.

[0018] 3. The electrode materials after in-situ synergistic modification were assembled into button batteries for electrochemical performance testing. The test results showed that the electrode materials in the present invention had significantly improved capacity retention and rate performance compared with similar conventional electrode materials, and significantly accelerated sodium ion diffusion rate, which effectively improved the electrochemical properties of sodium manganese vanadium phosphate electrode materials. Implementation Example

[0019] 1. Preparation method of in-situ synergistic modified sodium manganese vanadium phosphate electrode material: (1) 4.45 g of ammonium dihydrogen phosphate, 1.15 g of manganese carbonate, 1.82 g of vanadium pentoxide, 4.24 g of sodium carbonate and 2.3 g of glucose were mixed evenly by roller ball milling for 9 h to obtain a precursor; (2) Take 3 g of the precursor and 0.03 g of potassium tetrafluoroaluminate and add them to 75 mL of anhydrous ethanol, stir for 4 h, mix well and heat to 80 °C and keep for 4.5 h, evaporate the anhydrous ethanol to obtain a composite precursor; (3) The composite precursor was placed in a vacuum drying oven, dried at 100°C for 12 hours, and then calcined in an argon inert atmosphere at a temperature of 700°C for 9 hours to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0020] 2. Battery assembly method: The in-situ synergistically modified sodium manganese vanadium phosphate electrode material powder prepared in the above step 1 and acetylene black powder were placed in a mortar at a mass ratio of 8:1 and mixed and ground for 30 minutes, then 10wt% of a binder was added and continued to grind until it became viscous to obtain an active material. The active material was evenly coated on an aluminum foil, and finally placed in a vacuum drying oven at 110°C for 12 hours to obtain an in-situ synergistically modified sodium manganese vanadium phosphate electrode. The prepared electrode was used as the positive electrode and the sodium metal sheet as the negative electrode, and the CR2032 battery was assembled in a glove box with argon as the protective atmosphere. Example

[0021] 1. Preparation method of in-situ synergistic modified sodium manganese vanadium phosphate electrode material: (1) 4.45 g of ammonium dihydrogen phosphate, 2.45 g of manganese acetate tetrahydrate, 1.17 g of ammonium metavanadate, 1.6 g of sodium hydroxide and 1.3 g of sucrose were mixed evenly by planetary ball milling for 6 h to obtain a precursor; (2) Take 3 g of the precursor and 0.03 g of potassium tetrafluoroaluminate and add them to 75 mL of anhydrous ethanol, stir for 3-5 hours, mix well and heat to 75 °C and keep for 3 hours, evaporate the anhydrous ethanol to obtain a composite precursor; (3) The composite precursor was placed in a vacuum drying oven, dried at 80°C for 10 hours, and then calcined in an argon inert atmosphere at a temperature of 600°C for 6 hours to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0022] 2. Battery assembly method: The in-situ synergistically modified sodium manganese vanadium phosphate electrode material powder prepared in the above step 1 and acetylene black powder were placed in a mortar at a mass ratio of 8:1 and mixed and ground for 30 minutes, then 10wt% of a binder was added and continued to grind until it became viscous to obtain an active material. The active material was evenly coated on an aluminum foil, and finally placed in a vacuum drying oven at 110°C for 12 hours to obtain an in-situ synergistically modified sodium manganese vanadium phosphate electrode. The prepared electrode was used as the positive electrode and the sodium metal sheet as the negative electrode, and the CR2032 battery was assembled in a glove box with argon as the protective atmosphere. Example

[0023] 1. Preparation method of in-situ synergistic modified sodium manganese vanadium phosphate electrode material: (1) 4.45 g of ammonium dihydrogen phosphate, 1.51 g of manganese sulfate, 1.5 g of vanadium trioxide, 3.28 g of sodium acetate and 2.148 g of glucose were mixed evenly by roller ball milling for 12 h to obtain a precursor; (2) Take 3 g of the precursor and 0.09 g of potassium tetrafluoroaluminate and add them to 75 mL of anhydrous ethanol, stir for 5 h, mix well, heat to 85 °C and keep for 6 h, evaporate the anhydrous ethanol to obtain a composite precursor; (3) The composite precursor is placed in a vacuum drying oven, dried at 120° C. for 14 h, and then calcined in an argon inert atmosphere at a temperature of 800° C. for 12 h to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0024] 2. Battery assembly method: The in-situ synergistically modified sodium manganese vanadium phosphate electrode material powder prepared in the above step 1 and acetylene black powder were placed in a mortar at a mass ratio of 7:2 and mixed and ground for 30 minutes, then 10wt% of a binder was added and continued to grind until it became viscous to obtain an active material. The active material was evenly coated on an aluminum foil, and finally placed in a vacuum drying oven at 110°C for 12 hours to obtain an in-situ synergistically modified sodium manganese vanadium phosphate electrode sheet. The prepared electrode sheet was used as the positive electrode and the sodium metal sheet as the negative electrode, and the CR2032 battery was assembled in a glove box with argon as the protective atmosphere. Example

[0025] 1. Preparation method of in-situ synergistic modified sodium manganese vanadium phosphate electrode material: (1) 3.6 g of sodium dihydrogen phosphate, 0.87 g of manganese dioxide, 1.82 g of vanadium pentoxide, 4.02 g of sodium oxalate and 2 g of ascorbic acid were mixed evenly by roller ball milling for 7 h to obtain a precursor; (2) Take 3 g of the precursor and 0.03 g of potassium tetrafluoroaluminate and add them to 75 mL of anhydrous ethanol, stir for 3 h, mix well, heat to 85 °C and keep for 5 h, evaporate the anhydrous ethanol to obtain a composite precursor; (3) The composite precursor was placed in a vacuum drying oven, dried at 110° C. for 11 h, and then calcined in an argon inert atmosphere at a temperature of 775° C. for 8 h to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0026] 2. Battery assembly method: The in-situ synergistically modified sodium manganese vanadium phosphate electrode material powder prepared in the above step 1 and acetylene black powder were placed in a mortar at a mass ratio of 8:1 and mixed and ground for 30 minutes, then 10wt% of a binder was added and continued to grind until it became viscous to obtain an active material. The active material was evenly coated on an aluminum foil, and finally placed in a vacuum drying oven at 110°C for 12 hours to obtain an in-situ synergistically modified sodium manganese vanadium phosphate electrode. The prepared electrode was used as the positive electrode and the sodium metal sheet as the negative electrode, and the CR2032 battery was assembled in a glove box with argon as the protective atmosphere. Example

[0027] 1. Preparation method of in-situ synergistic modified sodium manganese vanadium phosphate electrode material: (1) 4.45 g of ammonium dihydrogen phosphate, 1.15 g of manganese carbonate, 1.17 g of ammonium metavanadate, 3.28 g of sodium acetate and 2.5 g of glucose were mixed evenly by planetary ball milling for 8 h to obtain a precursor; (2) Take 3 g of the precursor and 0.06 g of potassium tetrafluoroaluminate and add them to 75 mL of anhydrous ethanol, stir for 5 h, mix well and heat to 75 °C and keep for 4 h, evaporate the anhydrous ethanol to obtain a composite precursor; (3) The composite precursor was placed in a vacuum drying oven, dried at 90°C for 13 hours, and then calcined in an argon inert atmosphere at a temperature of 675°C for 12 hours to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

[0028] 2. Battery assembly method: The in-situ synergistically modified sodium manganese vanadium phosphate electrode material powder prepared in the above step 1 and acetylene black powder were placed in a mortar at a mass ratio of 7:2 and mixed and ground for 30 minutes, then 10wt% of a binder was added and continued to grind until it became viscous to obtain an active material. The active material was evenly coated on an aluminum foil, and finally placed in a vacuum drying oven at 110°C for 12 hours to obtain an in-situ synergistically modified sodium manganese vanadium phosphate electrode sheet. The prepared electrode sheet was used as the positive electrode and the sodium metal sheet as the negative electrode, and the CR2032 battery was assembled in a glove box with argon as the protective atmosphere.

Claims

1. A method for preparing an in-situ synergistically modified sodium manganese vanadium phosphate electrode material, characterized in that: The following steps are included: (1) mixing a phosphorus source, a manganese source, a vanadium source, a sodium source and a carbon source, and grinding them into uniform fine powder by ball milling to obtain a precursor; (2) adding the precursor and the modified material into anhydrous ethanol, stirring and mixing them evenly, and then heating and evaporating the anhydrous ethanol to obtain a composite precursor; (3) After the composite precursor is dried, it is calcined in an inert gas environment to obtain in-situ synergistically modified sodium manganese vanadium phosphate.

2. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (1), the molar ratio of phosphorus in the phosphorus source, manganese in the manganese source, vanadium in the vanadium source and sodium in the sodium source is 2-4:0.5-1.5:0.5-1.5:3-5, and the amount of carbon source added is 10%-30% of the total mass of the phosphorus source, manganese source, vanadium source and sodium source.

3. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 2, characterized in that: In the step (1), the molar ratio of phosphorus in the phosphorus source, manganese in the manganese source, vanadium in the vanadium source and sodium in the sodium source is 3:1:1:4, and the amount of carbon source added is 15%-25% of the total mass of the phosphorus source, manganese source, vanadium source and sodium source.

4. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (2), the modified material is potassium tetrafluoroaluminate, the amount of the modified material added is 1%-5% of the mass of the precursor, and the ratio of anhydrous ethanol to the precursor is 25mL:1g.

5. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (3), the drying equipment is a vacuum drying oven, the drying temperature is 80-120° C., and the drying time is 10-14 hours.

6. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to any one of claims 1 to 3, characterized in that: In the step (1), the phosphorus source is one or more of ammonium dihydrogen phosphate, phosphoric acid, sodium phosphate, and sodium dihydrogen phosphate; the manganese source is one or more of manganese carbonate, manganese acetate tetrahydrate, manganese sulfate, and manganese dioxide; the vanadium source is one or more of vanadium pentoxide, ammonium metavanadate, and vanadium trioxide; the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium acetate, and sodium oxalate; and the carbon source is one or more of glucose, ascorbic acid, sodium citrate, and sucrose.

7. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (2), the stirring time is 3-5 hours, the temperature is raised to 75-85°C, and the temperature is maintained for 3-6 hours after the temperature is raised.

8. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (3), the calcination equipment is a tubular furnace, the calcination temperature is 600-800° C., the calcination time is 6-12 hours, and the inert gas is argon.

9. The method for preparing the in-situ synergistically modified sodium manganese vanadium phosphate electrode material according to claim 1, characterized in that: In the step (1), the ball milling is a drum ball mill or a planetary ball mill; and the ball milling time is 6-12 hours.

10. An in-situ synergistically modified sodium manganese vanadium phosphate electrode material prepared according to any one of claims 1 to 9.