Preparation method of pyrophosphate doped vanadium manganese sodium phosphate / carbon composite positive electrode material with high cycle performance
By doping pyrophosphate in sodium manganese vanadium phosphate and combining with the high-temperature roasting process, the problems of poor electronic conductivity and easy structure collapse are solved, and its cycling performance and high-current performance are significantly improved.
Patent Information
- Application Number
- CN202411812749.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-03-11
AI Technical Summary
As the cathode material of sodium ion battery, sodium manganese vanadium phosphate has poor electronic conductivity, easy structure collapse and manganese dissolution, resulting in fast capacity decay and poor circulation performance, limiting its practical application.
Through the pyrophosphate doping method, the sol-gel method combined with the high-temperature calcination process is used to partially replace the phosphate anions in sodium manganese vanadium phosphate, strengthen its crystal structure stability, and improve electron conductivity through in-situ carbon coating.
The rate performance and cyclic performance of the sodium manganese vanadium phosphate/carbon composite cathode material are significantly improved, and excellent high current performance and cyclic performance are obtained.
Smart Images
Figure CN119601640A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of new energy materials, and in particular relates to a method for preparing a high-cycle performance pyrophosphate-doped sodium vanadium manganese phosphate / carbon composite positive electrode material. Background Art
[0002] With the decreasing reserves of primary energy represented by fossil energy and the rise of the "green revolution", the development of new energy has gradually become the focus of attention of all countries. In order to ease the pressure of energy storage and solve the problem of intermittent supply of new energy, more and more people are turning their attention to chemical power sources dominated by lithium-ion batteries. Compared with lithium-ion batteries, sodium-ion batteries are widely regarded as the main development direction of large-scale energy storage in the future due to their wide range of sodium resources, low cost and similar energy storage mechanism to commercial lithium-ion batteries. In order to further accelerate the development of high-performance and low-cost sodium-ion batteries, people have conducted a lot of research on a variety of existing positive electrode materials, such as transition metal oxides, polyanion compounds, Prussian blue analogs and organic matter. Among them, the fast ion conductor polyanion compound sodium manganese vanadium phosphate (Na4VMn(PO4)3) is considered to be a more promising positive electrode material for sodium ion batteries due to its higher energy density, lower cost and less toxicity. However, due to poor electronic conductivity, easy structural collapse during the cycle and manganese dissolution, the capacity of sodium manganese vanadium phosphate decays quickly and the cycle performance is poor, which hinders the practical application of sodium manganese vanadium phosphate. Therefore, the modification method can improve the electronic conductivity and inhibit the Mn 3+ The key to significantly improving the electrochemical performance of sodium manganese vanadium phosphate is to reduce the Jan-Taylor effect and improve the stability of the crystal structure. Summary of the invention
[0003] The purpose of the present invention is to provide a method for preparing a sodium manganese vanadium phosphate / carbon composite positive electrode material. The doping of pyrophosphate significantly improves the rate performance and cycle performance of the sodium manganese vanadium phosphate / carbon composite positive electrode material.
[0004] The method for preparing a high cycle performance pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite positive electrode material specifically comprises the following steps:
[0005] (1) Dissolve the vanadium source compound and the manganese source compound in hot distilled water or deionized water, then add the chelating agent, the sodium source compound, the phosphorus source compound, and sodium pyrophosphate, and continue stirring and heating until the mixed solution becomes a viscous gel, and then transfer it to a freeze dryer and dry it for 48 to 72 hours. The molar ratio of the sodium source compound, the vanadium source compound, the manganese source compound, the phosphorus source compound, and the sodium pyrophosphate is Na: V: Mn: PO4 3- : (P2O7) 4-=(4 + x):1:1:(3 - x):x, where 0 < x ≤ 0.5. The molar ratio of the chelating agent to Mn is 1.6 - 2.5.
[0006] (2) Place the dried gel in (1) in an inert atmosphere, heat it at a heating rate of 3 - 5 °C / min to 350 °C and hold for 4 - 8 h, then continue to heat it at a heating rate of 3 - 5 °C / min to 700 - 900 °C, and keep it at a constant temperature for 8 - 12 h, and then naturally cool it to room temperature to obtain the pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite material.
[0007] The sodium source compound is one or more of sodium acetate, sodium hydroxide, sodium carbonate, sodium nitrate, sodium sulfate, and sodium dihydrogen phosphate;
[0008] The vanadium source compound is one or more of vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate;
[0009] The manganese source compound is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride;
[0010] The phosphorus source compound is one or more of ammonium dihydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, and phosphoric acid;
[0011] The chelating agent is one or more of ethylenediaminetetraacetic acid, citric acid, and tartaric acid;
[0012] The inert gas is one or two of argon and nitrogen.
[0013] The present invention utilizes the advantages of the strong inductive effect and higher electronegativity of pyrophosphate, and adopts a simple sol-gel method combined with a high-temperature calcination process to partially replace the phosphate anions in sodium manganese vanadium phosphate. The strong inductive effect of pyrophosphate can effectively inhibit the Jahn-Teller effect of Mn 3+ and the dissolution of Mn, reduce the structural deformation during charge and discharge, strengthen the crystal structure stability of sodium manganese vanadium phosphate, and provide a larger channel for the rapid migration of Na + to improve the high-current performance of sodium manganese vanadium phosphate. The in-situ generated carbon coating is used to improve the electronic conductivity of the composite material and can inhibit the growth and aggregation of particles, thereby obtaining a pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite cathode material with excellent electrochemical performance. This material has excellent high-current performance and cycling performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 is the XRD pattern of the Na 4.1 MnV(PO4) 2.9 (P2O7) 0.1 / C composite material prepared in Example 1 of the present invention.
[0015] Figure 2 is the Na obtained in Example 1 of the present invention 4.1 MnV(PO4) 2.9 (P2O7) 0.1 The first charge and discharge curves of the / C composite material in the voltage range of 2.5~3.8 V and the current density of 0.5 C (56 mA / g).
[0016] Figure 3 is the Na obtained in Example 1 of the present invention 4.1 MnV(PO4) 2.9 (P2O7) 0.1 Cycling performance of the / C composite material in the voltage range of 2.5~3.8 V and current density of 0.5 C (56 mA / g).
[0017] Figure 4 It is Na obtained in Example 2 of the present invention. 4.2 MnV(PO4) 2.8 (P2O7) 0.2 / C composite material. DETAILED DESCRIPTION
[0018] Example 1
[0019] (1) 1.2254 g manganese acetate and 0.4547 g vanadium pentoxide were added to a beaker containing 30 mL hot distilled water. After the manganese acetate and vanadium pentoxide were completely dissolved, 2.3379 g ethylenediaminetetraacetic acid was added and stirred until the solution was clear. Then 1.6679 g ammonium dihydrogen phosphate, 1.517 g sodium acetate and 0.2230 g sodium pyrophosphate were slowly added to the clear solution. The mixed solution was placed in a water bath and the water bath was heated to 80 °C. After the reaction until the solution became a viscous gel, the beaker was transferred to a freeze dryer and dried for 72 h before being taken out. The dry gel was transferred to a magnetic boat and heated to 750 °C in a tube furnace under an argon atmosphere at a heating rate of 5 °C / min and maintained for 12 h. After the tube furnace was cooled to room temperature, the product was taken out to obtain pyrophosphate-doped sodium manganese vanadium phosphate Na 4.1 MnV(PO4) 2.9 (P2O7) 0.1 / C. Figure 1 is the XRD pattern of the material.
[0020] (2) According to the mass ratio of 8:1:1, 0.1 g active material, 0.0125 g PVDF (binder) and 0.0125 g acetylene black (conductive agent) were weighed respectively, and the mixture was thoroughly ground until uniform. Then, the mixture was transferred to a sample bottle, and an appropriate amount of NMP was added to stir on a magnetic stirrer. The stirred slurry was coated on aluminum foil with a coater and dried in an oven at 110 °C for 12 h. After drying, a circular electrode sheet with a diameter of 12 mm was cut out using a slicer, and the electrode sheet was rolled and weighed as the positive electrode sheet. The sodium sheet was used as the negative electrode, the GF / D glass fiber membrane was used as the separator, and 1 mol / L NaClO4 (DMC:EC:EMC=1:1:1, 2 wt% FEC) was used as the electrolyte. The CR2016 button cell was assembled in a glove box filled with argon protection (H2O<1 ppm, O2<1 ppm) and placed at room temperature for 12 h before testing. The button cell was placed on a battery testing system. When the current density was 0.5 C and the charge and discharge voltage range was 2.5~3.8V, the first discharge capacity was 96.4 mAh / g. After 50 cycles, the capacity remained at 90.7 mAh / g, with a retention rate of 94.1%. Figure 2 and Figure 3 The first charge and discharge curves and cycle performance curves of the material under the voltage range of 2.5~3.8V and current density of 0.5 C.
[0021] Example 2
[0022] (1) 1.2254 g manganese acetate and 0.5849 g ammonium metavanadate were added to a beaker containing 25 mL hot distilled water. After manganese acetate and ammonium metavanadate were completely dissolved, 2.3379 g ethylenediaminetetraacetic acid was added and stirred until the solution was clear. Then 1.6104 g ammonium dihydrogen phosphate, 1.394 g sodium acetate and 0.4461 g sodium pyrophosphate were slowly added to the clear solution. The mixed solution was placed in a water bath and the water bath was heated to 80 °C until the reaction solution became a viscous gel. The beaker was then transferred to a freeze dryer and dried for 72 h before being taken out. The dry gel was transferred to a magnetic boat and heated to 750 °C in a tube furnace under an argon atmosphere at a heating rate of 5 °C / min for 12 h. After the tube furnace was cooled to room temperature, the product was taken out to obtain pyrophosphate-doped sodium manganese vanadium phosphate Na 4.2 MnV(PO4) 2.8 (P2O7) 0.2 / C. Figure 4 This is the SEM image of the material.
[0023] (2) According to the mass ratio of 8: 1: 1, 0.1 g active material, 0.0125 g PVDF (binder) and 0.0125 g acetylene black (conductive agent) were weighed respectively, and the mixture was thoroughly ground until uniform. Then, the mixture was transferred to a sample bottle, and an appropriate amount of NMP was added and stirred on a magnetic stirrer. The stirred slurry was coated on an aluminum foil with a coater and dried in an oven at 110 °C for 12 h. After drying, a circular electrode sheet with a diameter of 12 mm was cut out using a slicer, and the electrode sheet was rolled and weighed as the positive electrode sheet. The sodium sheet was used as the negative electrode, the GF / D glass fiber membrane was used as the separator, and 1 mol / L NaClO4 (DMC:EC:EMC=1:1:1, 2 wt% FEC) was used as the electrolyte. The CR2016 button cell was assembled in a glove box filled with argon protection (H2O<1 ppm, O2<1 ppm) and placed at room temperature for 12 h before testing. The button cell was placed on a battery testing system. When the current density was 0.5 C and the charge and discharge voltage range was 2.5-3.8 V, the first discharge capacity was 88.7 mAh / g. After 50 cycles, the capacity remained at 82.5 mAh / g, with a retention rate of 93%.
[0024] Example 3
[0025] (1) Add 1.2675 g of manganese nitrate and 0.4547 g of vanadium pentoxide to a beaker containing 30 mL of hot distilled water. After the manganese nitrate and vanadium pentoxide are completely dissolved, add 2.3379 g of ethylenediaminetetraacetic acid and stir until the solution is clear. Then slowly add 1.4379 g of ammonium dihydrogen phosphate, 1.025 g of sodium acetate and 1.1151 g of sodium pyrophosphate to the clear solution. Heat the water bath to 85 °C and wait until the solution becomes a viscous gel. Then transfer the beaker to a freeze dryer and dry for 72 hours. Transfer the dry gel to a magnetic boat and heat it to 750 °C in a tubular furnace under an argon atmosphere at a heating rate of 5 °C / min for 12 hours. After cooling to room temperature, take out the product to obtain pyrophosphate-doped Na 4.5 MnV(PO4) 2.5 (P2O7) 0.5 / C composite material.
[0026] (2) According to the mass ratio of 8:1:1, 0.1 g active material, 0.0125 g PVDF (binder) and 0.0125 g acetylene black (conductive agent) were weighed respectively, and the mixture was thoroughly ground until uniform. Then the mixture was transferred to a sample bottle, and an appropriate amount of NMP was added to stir on a magnetic stirrer. The stirred slurry was coated on aluminum foil with a coater and dried in an oven at 110 °C for 12 h. After drying, a circular electrode sheet with a diameter of 12 mm was cut out using a slicer, and the electrode sheet was rolled and weighed as the positive electrode sheet. The sodium sheet was used as the negative electrode, the GF / D glass fiber membrane was used as the separator, and 1 mol / L NaClO4 (DMC:EC:EMC=1:1:1, 2 wt% FEC) was used as the electrolyte. The CR2016 button cell was assembled in a glove box filled with argon protection (H2O<1 ppm, O2<1 ppm) and placed at room temperature for 12 h before testing. The button cell was placed on a battery testing system. When the current density was 0.5 C and the charge and discharge voltage range was 2.5~3.8V, the first discharge capacity was 76 mAh / g. After 50 cycles, the capacity remained at 69.1 mAh / g, with a retention rate of 90.9%.
[0027] Since there are many implementation schemes of the present invention, they are not listed here one by one. Without departing from 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 high cycle performance pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite material, characterized in that: The molecular formula of doped sodium manganese vanadium phosphate is Na 4+x VMn(PO4) 3-x (P2O7) x , where 0 <x≤0.5。 2. The method for preparing the pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite material according to claim 1, characterized in that: The specific steps are: (1) Dissolve the vanadium source compound and the manganese source compound in hot distilled water or deionized water, then add a chelating agent, a sodium source compound, a phosphorus source compound, and sodium pyrophosphate, and continuously stir and heat until the mixed solution becomes a viscous gel, and then transfer it to a freeze dryer and dry for 48 - 72 h; wherein, the molar ratio of the sodium source compound, the vanadium source compound, the manganese source compound, the phosphorus source compound, and sodium pyrophosphate is Na: V: Mn: PO4 3- : (P2O7) 4- = (4 + x): 1: 1: (3 - x): x, where 0 < x ≤ 0.5; the molar ratio of the chelating agent to Mn is 1.6 - 2.5; (2) The dried gel in (1) is placed in an inert atmosphere, heated to 350 °C at a heating rate of 3-5 °C / min and maintained for 4-8 h, then further heated to 700-900 °C at a heating rate of 3-5 °C / min and maintained at the constant temperature for 8-12 h, and then naturally cooled to room temperature to obtain a pyrophosphate-doped sodium manganese vanadium phosphate / carbon composite material.
3. The preparation method according to claim 2, characterized in that: The sodium source compound is one or more of sodium acetate, sodium hydroxide, sodium carbonate, sodium nitrate, sodium sulfate, and sodium dihydrogen phosphate.
4. The preparation method according to claim 2, characterized in that: The vanadium source compound is one or more of vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate.
5. The preparation method according to claim 2, characterized in that: The manganese source compound is one or more of manganese nitrate, manganese acetate, manganese sulfate and manganese chloride.
6. The preparation method according to claim 2, characterized in that: The phosphorus source compound is one or more of diammonium phosphate, ammonium phosphate, sodium dihydrogen phosphate and phosphoric acid.
7. The preparation method according to claim 2, characterized in that: The chelating agent is one or more of ethylenediaminetetraacetic acid, citric acid and tartaric acid.
8. The preparation method according to claim 2, characterized in that: The inert gas is one or both of argon and nitrogen.