Ball-milling and calcining preparation method and application of high-performance novel sodium ferric sulfate pyrophosphate composite material
The sodium ferric pyrophosphate composite material prepared through ball milling and calcining processes solves the problems of low electronic conductivity and high temperature decomposition of the positive electrode material of sodium ion battery, and achieves the improvement of electrochemical performance and cost reduction of high-performance sodium ion battery.
Patent Information
- Application Number
- CN202510519262.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-25
AI Technical Summary
The existing sodium ion battery positive electrode materials have problems such as low electronic conductivity, easy high temperature decomposition and uneven carbon coating, which limits their performance and large-scale production applications under high-rate charging and discharge conditions.
The high-performance sodium ferrophosphate sulfuric acid composite material is prepared by ball milling and calcining processes, and the uniform mixing of raw materials is achieved through ball milling, and the in-situ coating of carbon materials is achieved at high temperatures through optimized calcining process to improve the electronic conductivity and thermal stability of the material.
It significantly improves the electronic conductivity and thermal stability of the material, improves the electrochemical performance of sodium ion batteries, especially the capacity retention rate and Coulomb efficiency under high-speed conditions, and provides a new way to reduce the performance and cost of sodium ion batteries.
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Figure CN120376560A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a ball milling and calcining preparation method and application of a high-performance novel sodium iron sulfate pyrophosphate composite material, belonging to the technical field of sodium ion batteries. Background Art
[0002] Under the background of global energy structure transformation and sustainable development, it is urgent to develop efficient and economical energy storage technologies to cope with the instability of energy supply and environmental challenges. Sodium-ion batteries have become one of the most popular energy storage technologies due to their abundant sodium resources, low cost and similar working mechanism to lithium-ion batteries. Sodium-ion batteries show great application potential in large-scale energy storage systems, low-speed electric vehicles and distributed energy networks. In the research of sodium-ion battery cathode materials, polyanionic compounds have attracted much attention due to their unique structural characteristics and excellent electrochemical properties.
[0003] Among them, pyrophosphate polyanion materials, such as Na2FeP2O7, are considered to be promising cathode materials due to their excellent thermal stability and structural stability, as well as high theoretical energy density. However, the currently known pyrophosphate cathode materials still have some bottlenecks in practical applications. On the one hand, the electronic conductivity of some materials is low, which restricts their performance under high-rate charge and discharge conditions. On the other hand, traditional carbon coating methods, such as high-temperature calcination, may cause damage to the material structure or produce side reactions. In addition, how to achieve uniform mixing of carbon materials and active materials and build an efficient conductive network is also a key issue that needs to be solved urgently.
[0004] It is worth noting that traditional sulfate polyanion materials, such as Alluaudite-type Na2Fe2(SO4)3 and Eldfellite-type NaFe(SO4)2, have a higher discharge voltage platform, but they are prone to decomposition at high temperatures, which makes it difficult to use biomass materials for high-temperature carbon coating modification, thus limiting their performance improvement and cost reduction. Therefore, it is urgent to develop an effective strategy that can overcome the problem of high-temperature decomposition and achieve uniform coating of carbon materials to improve the electrochemical performance of sulfate cathode materials.
[0005] Existing related patents mainly use common sodium ferric pyrophosphate and sodium ferric sulfate positive electrode materials to improve the overall performance of the positive electrode materials. However, due to the poor thermal stability of sodium ferric sulfate, low electronic conductivity, and difficulty in using biomass materials for carbon coating, the existing methods often fail to achieve the desired effect and are not conducive to large-scale industrial production. Summary of the invention
[0006] The object of the present invention is to provide a ball milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material, and a simple method based on ball milling and calcination processes is proposed for designing and preparing a high-performance novel sodium iron pyrophosphate sulfate composite material. This method aims to achieve full mixing and uniform dispersion of raw materials through the ball milling process, lay a foundation for subsequent carbon coating, and obtain a novel sodium iron pyrophosphate sulfate composite material with excellent electrochemical performance by optimizing the calcination process, thereby improving the overall performance of sodium-ion batteries.
[0007] The object of the present invention can be achieved by the following technical solutions:
[0008] A ball milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material, comprising the following steps:
[0009] (1) Sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, ferrous oxalate dihydrate, a solvent, an antioxidant and / or a carbon source are added to a ball milling tank in proportion for ball milling treatment to obtain a uniform mixed precursor material. The precursor material is dried in a vacuum oven and ground in a mortar to obtain a mixed precursor powder.
[0010] (2) The mixed precursor powder is placed in a crucible, and the crucible is placed in a heating device for high-temperature treatment. It is heated to 600 °C and calcined for 8 - 12 h. The sintering atmosphere is an inert gas. After the calcination is completed, it is cooled down to obtain a novel sodium iron pyrophosphate sulfate composite cathode material in the crucible.
[0011] Furthermore, in step (1), the molar ratio of sodium carbonate to ammonium sulfate is 1.5 - 2.5:1, the molar ratio of ferric nitrate nonahydrate to ammonium sulfate is 1 - 4:1, the molar ratio of diammonium hydrogen phosphate to ammonium sulfate is 1 - 3:1, and the chemical formula of the prepared cathode material is Na a Fe b (PO4) c SO4, where 3 ≤ a ≤ 5, 1 ≤ b ≤ 4, 1 ≤ c ≤ 3.
[0012] Furthermore, in step (1), the solvent is acetone or ethanol, and the mass ratio of the solvent to the mixed precursor powder is 0.8 - 1.5:1.
[0013] Furthermore, in step (1), the antioxidant can be citric acid or ascorbic acid, and the molar ratio of citric acid to Fe 2+ is 1:10.
[0014] Furthermore, in step (1), the carbon source accounts for 0 - 15% of the mass of sodium iron pyrophosphate sulfate, and the carbon source can be sucrose, maltose or glucose.
[0015] Further, in step (1), the ball milling speed is 500 r, and the ball milling time is 8 - 12 h.
[0016] Further, in step (1), the vacuum drying temperature is 100 °C, and the vacuum drying time is 10 h.
[0017] Further, in step (2), the heating device is a tubular furnace, the inert gas is Ar or N2, and the calcination heating rate is 3 °C / min.
[0018] Beneficial effects
[0019] The present invention discloses a ball milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material. This method adopts ball milling combined with subsequent calcination process, and innovatively introduces pyrophosphate (P2O7) into sulfate-based polyanion materials, successfully designing and synthesizing a novel sodium iron pyrophosphate sulfate composite polyanion cathode material. This innovative structural design not only inherits the high-temperature calcination stability of pyrophosphate materials, but also significantly improves the thermodynamic stability of the materials, effectively inhibiting the decomposition of sulfate radicals during the high-temperature synthesis process, so that a more extensive carbon coating strategy can be adopted. In addition, this process can achieve in-situ coating of low-cost biomass carbon under high-temperature conditions, while reducing production costs, significantly improving the electronic conductivity of the materials, and effectively improving the rate performance of the materials. The design concept of this composite material combines the advantages of pyrophosphates and sulfates, further improving the capacity of the materials on the basis of stability. Experimental data show that the carbon-coated Na2Fe2P2O7SO4 / C-10 material prepared by the method of the present invention has an initial discharge specific capacity of up to 120.67 mAh / g at a discharge rate of 0.05C. The present invention not only overcomes the problems of traditional sulfate cathode materials in terms of high-temperature stability, but also realizes a double improvement in stability and capacity through the innovative design of the material structure, opening up a new way to improve the performance of sodium-ion batteries and reduce production costs, and laying a solid foundation for the practical application of this type of material. Description of the drawings
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below.
[0021] Figure 1 It is the SEM diagram of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1.
[0022] Figure 2 It is the XRD diagram of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1.
[0023] Figure 3is the first constant current charge and discharge performance of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1 at 0.05C
[0024] charge and discharge performance.
[0025] Figure 4 is the rate performance test of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1
[0026] Figure 5 is the 1C cycle capacity performance of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1
[0027] Figure 6 is the 1C cycle Coulombic efficiency of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1
[0028] Figure 7 is the EIS diagram of the Na2Fe2P2O7SO4 / C-10 cathode material in Example 1 Detailed implementation manners
[0029] The present invention will be further described in detail below with reference to specific embodiments.
[0030] In the following examples or comparative examples:
[0031] (1) XRD test: Take an appropriate amount of the finished product powder and evenly coat it on a glass slide. According to the conventional XRD test method, the corresponding data can be obtained by testing under an XRD test instrument.
[0032] (2) Button battery assembly: At room temperature, electrochemical performance tests are carried out through CR2025 button batteries. First, weigh the active material, binder, and conductive agent prepared in the example or comparative example at a mass ratio of 7:1:2 and grind them in NMP for 30 min to obtain a black homogeneous slurry. Coat the slurry on the aluminum foil with a scraper and dry it in a vacuum oven at 100°C for 12 h to remove the solvent. Finally, use a punching machine to cut the aluminum foil coated with the sample into a circular positive electrode plate with a diameter of 1.1 cm.
[0033] (3) Electrochemical performance test: Using a sodium sheet as the negative electrode, a glass fiber as the separator, and 1M NaClO4 (EC:PC = 1:1, containing 5% FEC) as the electrolyte, the charge and discharge tests are completed under a Neware battery test system. The test voltage range is 1.5 - 4.5V and 2.0 - 4.5V, the test temperature is 30°C, and the test current density is 0.05 - 1.0C (1C = 100 mA / g).
[0034] Example 1
[0035] Preparation of Na2Fe2P2O7SO4 / C-10 material:
[0036] Weigh sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, and ferrous oxalate dihydrate with a molar ratio of 1:1:2:2 and add them to the ball milling tank. During this process, add an appropriate amount of citric acid according to a molar ratio of citric acid to Fe 2+ with a molar ratio of 10:1, 10 wt% glucose, and add an appropriate amount of acetone according to a mass ratio of solvent to mixed precursor powder of 0.9:1. Mix the mixture in a ball mill at a rotation speed of 500 r for 12 h to obtain a yellow viscous precursor material. Vacuum dry the precursor material in a vacuum oven at 100 °C for 12 h, then cool it to room temperature and grind it to obtain the precursor powder. Put the mixed precursor powder into a crucible, place the crucible in a tube furnace for high-temperature treatment, heat up to 600 °C and calcine for 10 h, with the sintering atmosphere being Ar gas. After the calcination is completed, cool it down, and a carbon-coated Na2Fe2P2O7SO4 / C-10 composite cathode material is obtained in the crucible.
[0037] Figure 1 Figure 1 is the scanning electron microscope image of the Na2Fe2P2O7SO4 / C-10 cathode material prepared in Example 1. It can be seen that Na2Fe2P2O7SO4 / C-10 has an irregular blocky morphology.
[0038] Figure 2 Figure 2 is the X-ray diffraction pattern of the Na2Fe2P2O7SO4 / C-10 cathode material prepared in Example 1. It can be seen that the intensity of the XRD diffraction peaks is relatively high, indicating that the Na2Fe2P2O7SO4 / C-10 cathode material has a high degree of crystallinity.
[0039] The electrochemical performance of the assembled battery is shown in Table 1 and Figure 3 as shown. The test voltage range is 1.5 - 4.5 V. For the sodium-ion battery assembled in this Example 1, at a current density of 0.05 C, the battery shows an initial discharge specific capacity of 120.67 mAh / g, indicating that the Na2Fe2P2O7SO4 / C-10 composite cathode material has excellent sodium-ion reversible deintercalation ability and can achieve efficient sodium-ion transport.
[0040] As Figure 4 shown, this material shows good discharge specific capacity at different current densities, indicating that the introduction of pyrophosphate ions by the ball milling method and the in-situ carbon coating process effectively improve the electronic conductivity of the polyanionic material, thus significantly improving its capacity performance under high-rate conditions.
[0041] According to Figure 5 and Figure 6As a result, after 300 cycles at a 1C rate, the sodium-ion battery assembled in Example 1 still maintained a capacity retention rate of 87.57% and a Coulombic efficiency as high as 99.37%. This fully demonstrates that the successful preparation of this composite material significantly improves the electrochemical cycling stability of the polyanionic material.
[0042] As Figure 7 shown, the sodium-ion battery assembled in Example 1 exhibited a lower internal resistance, indicating that this composite polyanionic material reduced the charge transfer resistance and improved the sodium-ion diffusion rate.
[0043] Comprehensive analysis Figures 3 to 7 of the data leads to the conclusion that the Na2Fe2P2O7SO4 / C-10 composite cathode material exhibits excellent electrochemical activity and stability, specifically manifested as: high initial discharge specific capacity, high Coulombic efficiency, and excellent cycling stability. The synergistic effect of the introduction of pyrophosphate and the in-situ carbon coating process significantly improves the electronic conductivity of the material, enabling it to maintain good capacity performance even at high current densities. Nevertheless, in order to more deeply explore the structure-activity relationship of the material and further optimize its electronic transport properties and structural stability, future research still needs to focus on exploring the deep-seated structure-property correlations to achieve a comprehensive improvement in sodium storage performance.
[0044] Example 2
[0045] Preparation of Na2Fe2P2O7SO4 material:
[0046] Weigh sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, and ferrous oxalate dihydrate with a molar ratio of 1:1:2:2 and add them to a ball milling jar. During this process, add an appropriate amount of citric acid according to a molar ratio of citric acid to Fe 2+ of 10:1, and add an appropriate amount of acetone according to a mass ratio of solvent to mixed precursor powder of 0.9:1. Mix the mixture in a ball mill at a rotation speed of 500r for 12h to obtain a yellow viscous precursor material. Vacuum dry the precursor material in a vacuum oven at 100°C for 12h, then cool it to room temperature and grind it to obtain precursor powder. Put the mixed precursor powder into a crucible, place the crucible in a tubular furnace for high-temperature treatment, heat it up to 600°C and calcine it for 10h. The sintering atmosphere is Ar gas. After the calcination is completed, cool it down to obtain a new Na2Fe2P2O7SO4 composite cathode material in the crucible.
[0047] The electrochemical performance of the assembled battery is shown in Table 1. The test voltage range is 1.5 - 4.5V. It can be seen from the table that in Example 2, the initial discharge capacity at 0.05C is 84.12 mAh / g, and the Coulombic efficiency is 96.08%.
[0048] Example 3
[0049] Preparation of Na2Fe2P2O7SO4 / C-5 material:
[0050] Weigh sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, and ferrous oxalate dihydrate with a molar ratio of 1:1:2:2 and add them to a ball milling jar. During this process, add an appropriate amount of citric acid according to a molar ratio of citric acid to Fe 2+ of 10:1, 5 wt% glucose, and add an appropriate amount of acetone according to a mass ratio of solvent to mixed precursor powder of 0.9:1. Mix the mixture in a ball mill at a speed of 500 r for 12 h to obtain a yellow viscous precursor material. Vacuum dry the precursor material in a vacuum oven at 100 °C for 12 h, then cool it to room temperature and grind it to obtain the precursor powder. Put the mixed precursor powder into a crucible, place the crucible in a tube furnace for high-temperature treatment, heat it to 600 °C and calcine it for 10 h. The sintering atmosphere is Ar gas. After the calcination is completed, cool it down to obtain the Na2Fe2P2O7SO4 / C-5 composite cathode material in the crucible.
[0051] The electrochemical performance of the assembled battery is shown in Table 1. The test voltage range is 1.5 - 4.5 V. It can be seen from the table that in Example 3, the initial discharge capacity at 0.05C is 108.47 mAh / g, and the Coulomb efficiency is 91.84%.
[0052] Example 4
[0053] Preparation of Na2Fe2P2O7SO4 / C-15 material:
[0054] Weigh sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, and ferrous oxalate dihydrate with a molar ratio of 1:1:2:2 and add them to a ball milling jar. During this process, add an appropriate amount of citric acid according to a molar ratio of citric acid to Fe 2+ of 10:1, 15 wt% glucose, and add an appropriate amount of acetone according to a mass ratio of solvent to mixed precursor powder of 0.9:1. Mix the mixture in a ball mill at a speed of 500 r for 12 h to obtain a yellow viscous precursor material. Vacuum dry the precursor material in a vacuum oven at 100 °C for 12 h, then cool it to room temperature and grind it to obtain the precursor powder. Put the mixed precursor powder into a crucible, place the crucible in a tube furnace for high-temperature treatment, heat it to 600 °C and calcine it for 10 h. The sintering atmosphere is Ar gas. After the calcination is completed, cool it down to obtain the Na2Fe2P2O7SO4 / C-15 composite cathode material in the crucible.
[0055] The electrochemical performance of the assembled battery is shown in Table 1. The test voltage range is 1.5 - 4.5 V. It can be seen from the table that in Example 4, the initial discharge capacity at 0.05C is 97.71 mAh / g, and the Coulomb efficiency is 90.42%.
[0056] Comparative Example 1
[0057] Preparation of Na 2+2x Fe 2-x (SO4)3-1 material:
[0058] First, sodium sulfate and ferrous sulfate heptahydrate were added to 25 ml of deionized water at room temperature according to a molar ratio of 1:1 and stirred to obtain a clear solution. During this process, an appropriate amount of ascorbic acid and glucose were added. Subsequently, the obtained mixed solution was slowly dropped into 100 ml of ethanol solution to form a gray-green precipitate. The precipitate was washed thoroughly with ethanol, filtered, and dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder. Finally, the precursor powder was sintered in an Ar atmosphere at 350 °C for 2 h to obtain the target product Na 2+2x Fe 2-x (SO4)3-1.
[0059] The electrochemical performance of the battery assembled in Comparative Example 1 had a discharge capacity of 22.5 mAh / g at 0.1C, and the test voltage range was 2.0 - 4.5 V.
[0060] Comparative Example 2
[0061] Preparation of Na 2+2x Fe 2-x (SO4)3-2 material:
[0062] First, sodium sulfate and ferrous sulfate heptahydrate were added to 25 ml of deionized water at room temperature according to a molar ratio of 1:2 and stirred to obtain a clear solution. During this process, an appropriate amount of ascorbic acid and glucose were added. Subsequently, the obtained mixed solution was slowly dropped into 100 ml of ethanol solution to form a gray-green precipitate. The precipitate was washed thoroughly with ethanol, filtered, and dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder. Finally, the precursor powder was sintered in an Ar atmosphere at 350 °C for 2 h to obtain the target product Na 2+2x Fe 2-x (SO4)3-2.
[0063] The electrochemical performance of the battery assembled in Comparative Example 2 had a discharge capacity of 21.0 mAh / g at 0.1C, and the test voltage range was 2.0 - 4.5 V.
[0064] Table 1 summarizes the test results of the electrochemical performance of the sodium-ion battery half-cells in the examples of the present invention. The experimental data show that by introducing pyrophosphate through the ball milling and calcination method, the thermodynamic stability of sulfates can be significantly enhanced, thus successfully realizing the in-situ coating of biomass carbon under high-temperature conditions. The introduction of this composite anion not only effectively improves Na +The transport rate of ions also brings a higher discharge specific capacity. More importantly, compared with the traditional Na2Fe2(SO4)3 material, the newly prepared Na2Fe2P2O7SO4 composite material of the present invention exhibits more excellent electrochemical activity and stability, which is mainly attributed to its more optimized crystal structure and smoother Na + diffusion channels.
[0065] Table 1 Test results of half-cell electrochemical performance
[0066] Case Initial discharge capacity of 0.05C Initial Coulombic efficiency Example 1 120.67 mAh / g 111.69％ Example 2 84.12 mAh / g 96.08％ Example 3 108.47 mAh / g 91.84％ Example 4 97.71 mAh / g 90.42％
[0067] In summary, the invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention will be regarded as within the protection scope of the present invention.
Claims
1. A method for preparing and applying a high-performance novel sodium ferric pyrophosphate sulfate composite material by ball milling and calcination, characterized in that, The novel sodium-ion battery sodium iron pyrophosphate sulfate composite polyanion cathode material is prepared by the following steps: (1) Sodium carbonate, ammonium sulfate, diammonium hydrogen phosphate, ferrous oxalate dihydrate, a solvent, an antioxidant and / or a carbon source are added to a ball milling tank in proportion for ball milling to obtain a uniform mixed precursor material. The precursor material is subjected to vacuum drying treatment in a vacuum oven, and after grinding in a mortar, a mixed precursor powder is obtained. (2) The mixed precursor powder is placed in a crucible, and the crucible is placed in a heating device for high-temperature treatment. The temperature is raised to 600 °C and calcined for 8-12 h. The sintering atmosphere is an inert gas. After the calcination is completed, it is cooled down, and a new sodium iron pyrophosphate sulfate composite cathode material is obtained in the crucible.
2. The ball milling and calcination preparation method and application of a high-performance novel sodium ferric pyrophosphate sulfate composite material according to claim 1, characterized in that, The sodium-ion battery is prepared by the following steps: First, the active material, binder and conductive agent prepared in the example are weighed at a mass ratio of 7:1:2, ground in NMP for 30 min to obtain a black uniform slurry. The slurry is coated on an aluminum foil with a scraper and dried in a vacuum oven at 100 °C for 12 h to remove the solvent. Finally, the aluminum foil coated with the sample is cut into a circular positive electrode plate with a diameter of 1.1 cm by a punching machine. Using a sodium sheet as the negative electrode, a glass fiber as the separator, 1 M NaClO4 (EC:PC = 1:1, containing 5% FEC) as the electrolyte, the charge-discharge test is completed under a Neware battery test system. The test voltage range is 1.5-4.5 V, the test temperature is 30 °C, and the test current density is 0.05-1.0 C (1 C = 100 mA / g).
3. A ball milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material according to claim 1, characterized in that The molar ratio of sodium carbonate to ammonium sulfate is 1.5 - 2.5:1, the molar ratio of iron(III) nitrate nonahydrate to ammonium sulfate is 1 - 4:1, and the molar ratio of diammonium hydrogen phosphate to ammonium sulfate is 1 - 3:
1. The chemical formula of the prepared cathode material is Na a Fe b (PO4) c SO4, where 3 ≤ a ≤ 5, 1 ≤ b ≤ 4, and 1 ≤ c ≤ 3.
4. A ball-milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material according to claim 1, characterized in that, The solvent is acetone or ethanol, and the mass ratio of the solvent to the mixed precursor powder is 0.8-1.5:
1.
5. A ball milling and calcination preparation method and application of a high-performance novel sodium ferric pyrophosphate sulfate composite material according to claim 1, characterized in that, The antioxidant may be citric acid or ascorbic acid, and the molar ratio of the citric acid to Fe 2+ is 1:
10.
6. A ball milling and calcination preparation method and application of a high-performance novel sodium ferric pyrophosphate sulfate composite material according to claim 1, characterized in that, The carbon source accounts for 0-15% of the mass of sodium iron pyrophosphate sulfate, and the carbon source can be sucrose, maltose or glucose.
7. A ball milling and calcination preparation method and application of a high-performance novel sodium ferric pyrophosphate sulfate composite material according to claim 1, characterized in that, The ball milling speed is 500 r, and the ball milling time is 8-12 h.
8. A ball milling and calcination preparation method and application of a high-performance novel sodium iron pyrophosphate sulfate composite material according to claim 1, characterized in that, The vacuum drying temperature is 100 °C, and the vacuum drying time is 10 h.
9. The ball milling and calcination preparation method and application of a high-performance novel sodium ferric pyrophosphate sulfate composite material according to claim 1, characterized in that, The heating device is a tube furnace, the inert atmosphere is Ar or N2, and the calcination heating rate is 3 °C / min.