An iron-manganese-based polyanion compound, a preparation method thereof and application thereof in a sodium ion battery

Abstract

The present application relates to iron manganese series polyanionic compound has one or two or more above structure shown in formula I, formula II, formula III: Na 4‑a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 3‑x‑z1‑z2 (PO4)2P2O7,0≤x<3 Formula INa 3‑a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 2‑x‑z1‑z2 (PO4)P2O7,0≤x<2 Formula IINa 2‑a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 1‑x‑z1‑z2 P2O7,0≤x<1 Formula III Through the cell electronic structure regulation mechanism improves the first circle charge and discharge process reversibility of material, the prepared phosphoric acid pyrophosphate composite, pyrophosphate composite polyanionic compound electrode material, the specific capacity is high and the rate performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, and relates to sodium-ion battery electrode materials, particularly phosphate-pyrophosphate composite or pyrophosphate polyanionic compound electrode materials, their preparation methods, and their applications in sodium-ion battery electrode materials. Background Technology

[0002] In recent years, with the goal of building a new power system dominated by new energy sources, the energy storage industry has maintained a high level of attention as it is crucial for regulating the volatility and indirectness of new energy sources and achieving grid connection stability. Alkali metal (Li, Na, K) ion batteries are an important component of portable large-scale stationary energy storage. Among them, lithium-ion batteries (LIBs) are widely used in electric vehicles and electronic devices due to their significant advantages such as high energy density, high electrode potential, stable cycle performance, and environmental friendliness. However, in recent years, the uneven distribution of lithium sources has become a key factor restricting the development of lithium-ion batteries. Sodium resources, with their uniform distribution, low cost, and abundance, have also attracted increasing attention. Therefore, developing high-performance sodium-ion battery cathode materials is particularly important.

[0003] Polyanionic sodium-ion battery cathode materials, such as sodium iron (manganese) pyrophosphate and sodium iron (manganese) phosphate pyrophosphate, are preferred cathode materials for alkali metal-ion batteries due to their advantages such as high raw material abundance, structural stability, high safety, and high redox potential. The redox potential of iron is approximately 3.0V vs. Na. + The crystal structure is stable and the electrolyte is highly compatible during the insertion / extraction of sodium ions (Na). The redox potential of manganese is approximately 3.6V vs. Na. + Because of the presence of Na, manganese-containing polyanion cathode materials have higher specific energy, but often exhibit problems due to Mn. 3+ The JT effect in the middle leads to instability issues such as atomic migration, rearrangement, and Mn dissolution in the polyanionic structure. Therefore, developing and preparing manganese-rich iron-manganese composite phosphate pyrophosphate cathode materials will be one of the preferred materials for high specific energy and long cycle life.

[0004] Iron and manganese, as redox centers, play a crucial role in the reduction process. 3+ Reduced to Fe 2+ Mn 3+ (3d4) is reduced to Mn 2+ However, during the electrochemical reduction process (with a lower voltage limit of approximately 1.5V), the reaction is not complete, and some Fe remains in the structure. 3+ or Mn 3 + Even iron and manganese in other valence states do not contribute to the reduction capacity, resulting in a low discharge specific capacity and thus a low specific energy. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a high-specific-energy iron-manganese-based phosphate-pyrophosphate composite or pyrophosphate polyanionic compound structure and its preparation method through cell-based electronic modulation.

[0006] In a first aspect, the present invention provides an iron-manganese based polyanionic compound, wherein the iron-manganese based polyanionic compound is one or more of a phosphate-pyrophosphate complex or a pyrophosphate polyanionic compound, and the phosphate-pyrophosphate complex or pyrophosphate polyanionic compound has one or more of the structures shown in Formula I, Formula II, and Formula III:

[0007] Na 4-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 3-x-z1-z2 (PO4)2P2O7 Formula I

[0008] Na 3-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 2-x-z1-z2 (PO4)P2O7 formula II

[0009] Na 2-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 1-x-z1-z2 P2O7 type III

[0010] Wherein, 4-a, x, z1, z2, and 3-x-z1-z2 represent the molar number of their corresponding elements, and n1 and n2 represent the valence of their corresponding elements; when the iron-manganese polyanionic compound is as shown in Formula I, (4-a)+2x+2*(3-x-z1-z2)+n1*z1+n2*z2=10;

[0011] When the iron-manganese polyanionic compound is as shown in Formula II, (3-a)+2x+2*(2-x-z1-z2)+n1*z1+n2*z2=7;

[0012] When the iron-manganese polyanionic compound is as shown in Formula III, (2-a)+2x+2*(1-x-z1-z2)+n1*z1+n2*z2=4;

[0013] In Equation I, 0 ≤ x < 3, 0.01 <z1<0.2,0.35≤z2 / z1≤0.75;

[0014] In Equation II, 0 ≤ x < 2, 0.01 <z1<0.2,0.35≤z2 / z1≤0.75;

[0015] In Equation III, 0 ≤ x < 1, 0.01 <z1<0.15,0.35≤z2 / z1≤0.75;

[0016] M1 is selected from Ti 3+ Ti 4+ V 3+ V 4+ or V 5+ One or more of the following; M2 is selected from Ni 2+ Cu + Cu 2+ or Zn 2+ One or more of them.

[0017] Further, in Equation I, 0.1≤x≤2.9, 0.05≤z1≤0.10, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤2.5;

[0018] In Equation II, 0.1≤x≤1.9, 0.05≤z1≤0.10, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤1.5;

[0019] In Formula III, 0.1≤x≤0.9, 0.03≤z1≤0.05, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤0.6.

[0020] More preferably, when M1 is selected from Ti 3+ At that time, M2 was selected from Ni 2+ Cu + One or more of them;

[0021] When M1 is selected from Ti 4+ At that time, M2 was selected from Zn 2+ ;

[0022] When M1 is selected from V 3+ V 4+ or V 5+ When one or more are present, M2 is selected from Zn. 2+ Cu + or Cu 2+One or more of them.

[0023] Furthermore, the iron-manganese-based polyanionic compound may also be a compound of the structures shown in Formula I, Formula II, and Formula III supported by C. In the C-supported compound, the mass content of C is 1 wt% - 20 wt%, preferably 3 wt% - 10 wt%.

[0024] In a second aspect, the present invention provides a method for preparing the iron-manganese-based polyanionic compound, comprising the following steps:

[0025] Step 1: Mix a sodium source, an iron source and / or a manganese source, an M1 source, an M2 source, a phosphorus source, and a carbon source evenly in a solvent to obtain a precursor slurry, and dry it to obtain a precursor powder P1;

[0026] Step 2: Heat-treat the precursor powder P1 obtained in Step 1 in an inert atmosphere or an inert atmosphere containing H2. After the heat treatment, a product P2 of an iron-based and / or manganese-based phosphate polyanionic compound can be obtained; the particle size of the product P2 is 5 - 10 microns.

[0027] Furthermore, in Step 1, the method of mixing the sodium source, the iron source and / or the manganese source, the M1 source, the M2 source, the phosphorus source, and the carbon source evenly includes one or more of ball milling, tank milling, and sand milling; the solid content of the precursor slurry is 15 wt% - 60 wt%, preferably 25 wt% - 45 wt%:

[0028] The solvent is water, ethanol, or a mixed solvent of water and ethanol. The proportion of water in the mixed solvent in the total mass of the mixed solvent is (30 - 80) wt%, preferably (45 - 55) wt%, and the proportion of ethanol in the total mass of the mixed solvent is (20 - 70) wt%, preferably (45 - 55) wt%;

[0029] The drying method is spray drying. Among them, the feed flow rate is controlled at 20 mL / min - 60 mL / min, the inlet air temperature is controlled at 140°C - 225°C, the outlet air temperature is 70°C - 120°C, and the compressed air pressure is 0.2 Mpa - 0.7 Mpa;

[0030] In Step 2, in the inert atmosphere containing H2, the molar content of H2 is 0 - 50%, preferably 10% - 20%; the heat treatment includes a process of treating at a first temperature T1 in sequence and a process of treating at a second temperature T2 after treating at the first temperature T1; the first temperature T1 is 200 ≤ T1 ≤ 400°C, and the treatment time is 0.5 - 6 h; the second temperature T2 is 400°C < T1 ≤ 750°C, and the treatment time is 3 - 20 h; the difference between T2 and T1 is greater than or equal to 50°C.

[0031] Furthermore, when the iron-manganese polyanionic compound has the structure shown in Formula I, the molar ratio of sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source is 4-a:x:z1:z2:3-x-z1-z2:4, and the molar ratio of sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source is expressed in terms of the molar amounts of sodium, iron, manganese, M1, M2, and phosphorus, respectively.

[0032] When the iron-manganese polyanionic compound has the structure shown in Formula II, the molar ratio of sodium source, iron source, manganese source, M1 source, M2 source and phosphorus source is 3-a:z1:z2:2-x-z1-z2:3, and the molar ratio of sodium source, iron source, manganese source, M1 source, M2 source and phosphorus source is expressed in terms of the molar amounts of sodium, iron, manganese, M1, M2 and phosphorus, respectively.

[0033] When the iron-manganese polyanionic compound has the structure shown in Formula III, the phosphate polyanionic compound has the structure shown in Formula IV. The molar ratio of sodium source, iron source, manganese source, M1 source, M2 source and phosphorus source is 2-a:x:z1:z2:1-x-z1-z2:2. The molar ratio of sodium source, iron source, manganese source, M1 source, M2 source and phosphorus source is expressed in terms of the molar amounts of sodium, iron, manganese, M1, M2 and phosphorus, respectively.

[0034] Furthermore, the sodium source is selected from one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, sodium citrate, sodium oxalate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, and sodium hydrogen pyrophosphate.

[0035] The iron source is selected from one or more of the following: iron powder, iron(II) oxide, ferric oxide, ferrous oxide, ferric oxalate, ferrous oxalate (dihydrate), ferric phosphate, ferric pyrophosphate, ferrous citrate, ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric acetate, ferrous ammonium sulfate, ferric citrate, ferric ammonium citrate, and sodium ferric citrate succinate.

[0036] The manganese source is selected from one or more of manganese monoxide, manganese dioxide, manganese trioxide, manganese tetroxide, manganese hydroxide, manganese sulfate, manganese chloride, manganese nitrate, manganese phosphate, manganese phosphate, manganese dihydrogen phosphate, manganese nitrate tetrahydrate, and manganese nitrate solution (concentration of 5-50 wt%).

[0037] The M1 and M2 sources are respectively selected from one or more of the oxides, hydroxides, acetates, nitrates, carbonates, oxalates, phosphates, pyrophosphates, chlorides, citrates, and sulfates corresponding to the M1 and M2 sources, respectively.

[0038] The phosphorus source is selected from one or more of the following: ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, pyrophosphate, sodium pyrophosphate, and sodium hydrogen pyrophosphate.

[0039] The carbon source is one or more of the following: polyethylene glycol, cellulose, starch, polyvinyl alcohol, formic acid, acetic acid, citric acid, malic acid, lactic acid, oxalic acid, tartaric acid, ascorbic acid, cyclohexanediol, salicylic acid, caffeic acid, ethylene acrylate copolymer, maleic acid copolymer, polyacrylic acid, polyvinyl acid, polyamic acid, and polybutenoic acid.

[0040] Thirdly, the present invention provides the application of the iron-manganese polyanionic compound or the iron-manganese polyanionic compound prepared by the preparation method as a positive electrode active material in sodium-ion batteries, wherein the pyrophosphate and / or phosphate-pyrophosphate composite polyanionic compound is used as an active material in the positive electrode of sodium-ion batteries.

[0041] Furthermore, in the sodium-ion battery cathode material, the content of the pyrophosphate and / or phosphoric acid pyrophosphate composite polyanionic compound electrode material is (60-98) wt%.

[0042] The positive electrode material also contains a conductive agent and a binder, and the mass ratio of the pyrophosphate and / or phosphoric acid pyrophosphate composite polyanionic compound, the conductive agent and the binder is (60-98) wt%:(1-39) wt%:(1-39) wt%.

[0043] The conductive agent is one or more of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene.

[0044] The adhesive is one or more of polyvinylidene fluoride: PVDF5130, HSV900, and kynar761A.

[0045] This invention selects a transition metal M based on the electron filling status of the d orbitals to form a unique MO6 structure in the unit cell. Preferably, the metal ion M1 is rich in 3d empty orbitals and its nucleus has a higher electron attraction ability than Fe. 3+ Mn 3+ Weak; simultaneously, the preferred metal ion M2 in the structure has essentially full 3d orbitals and it interacts with Fe. 3+ Mn 3+ Compared to atomic nuclei, M1 has a stronger attraction for electrons. Furthermore, since M1 and M2 exhibit opposite electronic effects, there is an optimal relationship between the types and amounts of M1 and M2, thereby forming specific electronic effects in MO6, which in turn affects the material's specific capacity and stability.

[0046] Beneficial effects

[0047] The invention of the above-mentioned novel iron-manganese-based phosphate-pyrophosphate complex and pyrophosphate polyanionic compounds is achieved by selecting compounds rich in 3d empty orbitals and with a higher electron-attracting ability to their atomic nuclei than Fe.3+ Mn 3+ The weaker metal ion has its M1 and 3d orbitals almost full and its interaction with Fe 3+ Mn 3+ Compared to the more electron-attracting metal ion M2, the atomic nucleus of Fe is constructed using the optimized electronic structure and controlled dosage of M1 and M2 to create a MO6 structure. This enhances the electron-accepting ability and transfer efficiency of the unit cell structure, achieving a greater amount of Fe, primarily composed of Fe and Mn, within a limited voltage range. 3+ The reduction reaction effectively improves the specific capacity and rate performance of iron-manganese-based polyanionic materials.

[0048] The synthesis process is simple. By improving the ionic and electronic conductivity of the material through the unit cell electronic regulation mechanism, the prepared iron-manganese-based phosphoric acid-pyrophosphate composite and pyrophosphate polyanionic compound electrode materials have high specific capacity and good rate performance. Attached Figure Description

[0049] Figure 1 The XRD diffraction patterns are of the materials in Example 1 and Comparative Example 1. Detailed Implementation

[0050] Example 1

[0051] 1) Add 2L of deionized water to a beaker, heat to 70℃, and then add 4mol of citric acid monohydrate (C6H2O) sequentially. 10 O8, 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50wt%), 0.1 mol titanium tetrachloride TiCl4, 0.05 mol zinc acetate dihydrate Zn(Ac)2·2H2O, the above raw materials are stirred until fully dissolved;

[0052] 2) Then add 3.8 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) to the above aqueous solution and continue stirring until the raw materials are completely dissolved to form a precursor solution;

[0053] 3) The precursor solution is passed into a spray drying device for spray drying. The inlet temperature is 170℃, the outlet temperature is 90℃, the feed flow rate is 50mL / min, and the compressed air pressure is 0.5Mpa, yielding approximately 1.2kg of precursor powder.

[0054] 4) Subsequently, 1.2 kg of precursor powder was transferred to a high-temperature rotary kiln under nitrogen atmosphere for heat treatment. First, heat treatment temperature T1 was 400℃ for 2 hours at a heating rate of 5℃ / min; then, heat treatment temperature T2 was 600℃ for 5 hours at a heating rate of 2℃ / min. The heat-treated sample was a loose powder with the chemical formula Na. 3.8 Fe 0.425 Mn 2.425 Ti 4+ 0.1 Zn 2+ 0.05 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.4 wt%.

[0055] 5) Perform XRD tests on the prepared fluffy powder, such as... Figure 1 Compared to Comparative Example 1, Na without elemental doping... 4.0 Fe 0.5 Mn 2.5 Compared to (PO4)2P2O7, the crystal structure remains unchanged, both belonging to the orthorhombic crystal system with space group Pn21a.

[0056] Example 2

[0057] The difference from Example 1 is as follows:

[0058] 1) 0.4325 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4325 mol -Mn(NO3)2 aqueous solution (50wt%), and 0.035 mol zinc acetate dihydrate Zn(Ac) 2. 2H₂O, replacing the corresponding Fe, Mn, and Zn sources;

[0059] Everything else is consistent with Example 1 (other processes and conditions are consistent with Example 1, the same below); 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.8 Fe 0.4325 Mn 2.4325 Ti 4+ 0.1 Zn 2+ 0.035 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.7 wt%.

[0060] Example 3

[0061] The difference from Example 1 is as follows:

[0062] 1) 0.43 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.43 mol of Mn(NO3)2 aqueous solution (50wt%), and 0.04 mol of zinc acetate dihydrate Zn(Ac)2·2H2O, to replace the corresponding Fe source, Mn source, and Zn source;

[0063] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.8 Fe 0.43 Mn 2.43 Ti 4+ 0.1 Zn 2+ 0.04 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.8 wt%.

[0064] Everything else remains the same as in Example 1.

[0065] Example 4

[0066] The difference from Example 1 is as follows:

[0067] 1) 0.42 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.42 mol of Mn(NO3)2 aqueous solution (50wt%), and 0.06 mol of zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, and Zn source;

[0068] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.8 Fe 0.42 Mn 2.42 Ti 4+ 0.1 Zn 2+ 0.06 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.7 wt%.

[0069] Everything else remains the same as in Example 1.

[0070] Example 5

[0071] The difference from Example 1 is as follows:

[0072] 1) 0.4125 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4125 mol Mn(NO3)2 aqueous solution (50wt%), and 0.075 mol zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, and Zn source;

[0073] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.8 Fe0.4125 Mn 2.4125 Ti 4+ 0.1 Zn 2+ 0.075 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 6.0 wt%.

[0074] Everything else remains the same as in Example 1.

[0075] Example 6

[0076] The difference from Example 1 is as follows:

[0077] 1) 0.485 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.485 mol Mn(NO3)2 aqueous solution (50wt%), 0.02 mol titanium tetrachloride TiCl4, and 0.01 mol zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0078] 2) Subsequently, 3.96 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0079] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.96 Fe 0.485 Mn 2.485 Ti 4+ 0.02 Zn 2+ 0.01 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.4 wt%.

[0080] Everything else remains the same as in Example 1.

[0081] Example 7

[0082] The difference from Example 1 is as follows:

[0083] 1) 0.44375 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.44375 mol Mn(NO3)2 aqueous solution (50wt%), 0.075 mol titanium tetrachloride TiCl4, and 0.0375 mol zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, titanium source, and Zn source;

[0084] 2) Subsequently, 3.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0085] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.85 Fe 0.44375 Mn 2.44375 Ti 4+ 0.075 Zn 2+ 0.0375 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.2 wt%.

[0086] Everything else remains the same as in Example 1.

[0087] Example 8

[0088] The difference from Example 1 is as follows:

[0089] 1) 0.41 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.41 mol of Mn(NO3)2 aqueous solution (50wt%), 0.12 mol of titanium tetrachloride TiCl4, and 0.06 mol of zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0090] 2) Subsequently, 3.76 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0091] Everything else remains the same as in Example 1;

[0092] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.76 Fe 0.41 Mn 2.41 Ti 4+ 0.12 Zn 2+ 0.06 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.8 wt%.

[0093] Everything else remains the same as in Example 1.

[0094] Example 9

[0095] The difference from Example 1 is as follows:

[0096] 1) 0.3575 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.3575 mol Mn(NO3)2 aqueous solution (50wt%), 0.19 mol titanium tetrachloride TiCl4, and 0.095 mol zinc acetate dihydrate Zn(Ac)2·2H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0097] 2) Subsequently, 3.62 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0098] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.62 Fe 0.3575 Mn 2.3575 Ti 4+ 0.19 Zn 2+ 0.095 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 6.7 wt%.

[0099] Everything else remains the same as in Example 1.

[0100] Example 10

[0101] The difference from Example 1 is as follows:

[0102] 1) 0.445 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4451 mol of Mn(NO3)2 aqueous solution (50wt%), 0.04 mol of titanium trioxide Ti2O3, and 0.03 mol of nickel nitrate hexahydrate Ni(NO3)2·6H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0103] 2) Subsequently, 3.92 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0104] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.92 Fe 0.445 Mn 2.445 Ti 4+ 0.08 Ni 2+ 0.03 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.05 wt%.

[0105] Everything else remains the same as in Example 1.

[0106] Example 11

[0107] The difference from Example 1 is as follows:

[0108] 1) 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50wt%), 0.045 mol titanium trioxide Ti2O3, and 0.03 mol cuprous oxide Cu2O, replacing the corresponding Fe source, Mn source, titanium source, and Zn source;

[0109] 2) Subsequently, 3.97 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0110] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.97 Fe 0.425 Mn 2.425 Ti 3+ 0.09 Cu + 0.06 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.5 wt%.

[0111] Everything else remains the same as in Example 1.

[0112] Example 12

[0113] The difference from Example 1 is as follows:

[0114] 1) 0.43 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.43 mol Mn(NO3)2 aqueous solution (50wt%), 0.05 mol vanadium trioxide V2O3, and 0.04 mol copper chloride CuCl2, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0115] 2) Subsequently, 3.90 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0116] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.90 Fe 0.43 Mn 2.43 V 3+ 0.10 Cu 2+ 0.04 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.9 wt%.

[0117] Everything else remains the same as in Example 1.

[0118] Example 13

[0119] The difference from Example 1 is as follows:

[0120] 1) 0.4475 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4475 mol Mn(NO3)2 aqueous solution (50wt%), 0.075 mol vanadium dioxide VO2, and 0.03 mol copper chloride CuCl2, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0121] 2) Subsequently, 3.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0122] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.85 Fe 0.4475 Mn 2.4475 V 4+ 0.075 Cu 2+ 0.03 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.1 wt%.

[0123] Everything else remains the same as in Example 1.

[0124] Example 14

[0125] The difference from Example 1 is as follows:

[0126] 1) 0.44 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.44 mol Mn(NO3)2 aqueous solution (50 wt%), 0.04 mol titanium trioxide Ti2O3, and 0.04 mol zinc acetate dihydrate Zn(Ac). 2. 2H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0127] 2) Subsequently, 3.92 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0128] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.92 Fe 0.44 Mn 2.44 Ti 3+ 0.08 Zn 2+ 0.04 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.1 wt%.

[0129] Everything else remains the same as in Example 1.

[0130] Example 15

[0131] The difference from Example 1 is as follows:

[0132] 1) 0.44 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.44 mol Mn(NO3)2 aqueous solution (50wt%), 0.04 mol titanium trioxide Ti2O3, and 0.04 mol copper chloride CuCl2, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0133] 2) Subsequently, 3.92 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0134] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.92 Fe 0.44 Mn 2.44 Ti 3+ 0.08 Cu 2+ 0.04 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.05 wt%.

[0135] Everything else remains the same as in Example 1.

[0136] Example 16

[0137] The difference from Example 1 is as follows:

[0138] 1) 0.43 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.43 mol of Mn(NO3)2 aqueous solution (50wt%), 0.05 mol of vanadium trioxide V2O3, and 0.04 mol of nickel nitrate hexahydrate Ni(NO3)2·6H2O, replacing the corresponding Fe source, Mn source, titanium source and Zn source;

[0139] 2) Subsequently, 3.90 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0140] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.90 Fe 0.43 Mn 2.43 V 3+ 0.10 Ni 2+ 0.04 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 6.03 wt%.

[0141] Everything else remains the same as in Example 1.

[0142] Example 17

[0143] The difference from Example 1 is as follows:

[0144] 1) 0.05 mol of nickel nitrate hexahydrate Ni(NO3)2·6H2O, replacing the corresponding Zn source;

[0145] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.425 Mn 2.425 Ti 4+ 0.10 Ni 2+ 0.05 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.57 wt%.

[0146] Everything else remains the same as in Example 1.

[0147] Example 18

[0148] The difference from Example 1 is as follows:

[0149] 1) A 1.425 mol-Mn(NO3)2 aqueous solution (50 wt%) was used to replace the corresponding Mn source;

[0150] 2) Subsequently, 2.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0151] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 2.80 Fe 0.425 Mn 1.425 Ti 4+ 0.10 Zn 2+ 0.05 (PO4)P2O7, and it is a C-supported structure with a C mass content of 6.9 wt%.

[0152] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 15, and was similar to that of undoped Na. 3.0 Fe 0.5 Mn 1.5 Compared to (PO4)P2O7, the crystal structure remains unchanged, both belonging to the orthorhombic crystal system, with space group P212121.

[0153] Everything else remains the same as in Example 1.

[0154] Example 19

[0155] The difference from Example 1 is as follows:

[0156] 1) 0.4475 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 1.4475 mol Mn(NO3)2 aqueous solution (50wt%), 0.075 mol vanadium dioxide VO2, and 0.03 mol copper chloride CuCl2 were used to replace the corresponding Fe source, Mn source, titanium source and Zn source.

[0157] 2) Subsequently, 2.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0158] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 2.85 Fe 0.4475 Mn 1.4475 V 4+ 0.075 Cu 2+ 0.03 It is (PO4)P2O7, and it has a C-supported structure with a C mass content of 6.7 wt%.

[0159] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 15, and was similar to that of undoped Na. 3.0 Fe 0.5 Mn 1.5 Compared to (PO4)P2O7, the crystal structure remains unchanged; it is still an orthorhombic crystal system with space group P212121.

[0160] Everything else remains the same as in Example 1.

[0161] Example 20

[0162] The difference from Example 1 is as follows:

[0163] 1) 0.43 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 1.43 mol Mn(NO3)2 aqueous solution (50wt%), 0.05 mol vanadium trioxide V2O3, and 0.04 mol copper chloride CuCl2 were used to replace the corresponding Fe source, Mn source, titanium source, and Zn source.

[0164] 2) Subsequently, 2.9 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0165] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 2.90 Fe 0.43 Mn 1.43 V3+ 0.10 Cu 2+ 0.04 It is (PO4)P2O7, and it has a C-supported structure with a C mass content of 6.3 wt%.

[0166] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 15, and was similar to that of undoped Na. 3.0 Fe 0.5 Mn 1.5 Compared to (PO4)P2O7, the crystal structure remains unchanged; it is still an orthorhombic crystal system with space group P212121.

[0167] Everything else remains the same as in Example 1.

[0168] Example 21

[0169] The difference from Example 1 is as follows:

[0170] 1) 0.22 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 0.72 mol Mn(NO3)2 aqueous solution (50 wt%), 0.04 mol titanium tetrachloride TiCl4, and 0.02 mol zinc acetate dihydrate Zn(Ac) 2. 2H2O replaces the corresponding Fe source, Mn source, titanium source, and Zn source;

[0171] 2) Subsequently, 1.92 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0172] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 1.92 Fe 0.22 Mn 0.72 Ti 4+ 0.04 Zn 2+ 0.02 P2O7, and it has a C-supported structure with a C mass content of 7.9 wt%.

[0173] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 16, and was similar to that of undoped Na. 2.0 Fe 0.5 Mn 1.5 Compared to P2O7, the crystal structure remains unchanged, both belonging to the triclinic crystal system with space group P1;

[0174] Everything else remains the same as in Example 1.

[0175] Example 22

[0176] The difference from Example 1 is as follows:

[0177] 1) 0.1975 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 0.6975 mol Mn(NO3)2 aqueous solution (50wt%), 0.075 mol vanadium dioxide VO2, and 0.03 mol copper chloride CuCl2 were used to replace the corresponding Fe source, Mn source, titanium source and Zn source.

[0178] 2) Subsequently, 1.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0179] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 1.85 Fe 0.1975 Mn 0.6975 V 4+ 0.075 Cu 2+ 0.03 P2O7, and it has a C-supported structure with a C mass content of 8.1 wt%.

[0180] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 16, and was similar to that of undoped Na. 2.0 Fe 0.5 Mn 1.5 Compared to P2O7, the crystal structure remains unchanged; it is still a triclinic crystal system with space group P1.

[0181] Everything else remains the same as in Example 1.

[0182] Example 23

[0183] The difference from Example 1 is as follows:

[0184] 1) 0.18 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 0.68 mol Mn(NO3)2 aqueous solution (50wt%), 0.05 mol vanadium trioxide V2O3, and 0.04 mol copper chloride CuCl2 were used to replace the corresponding Fe source, Mn source, titanium source, and Zn source.

[0185] 2) Subsequently, 1.90 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0186] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 1.90 Fe 0.18 Mn 0.68 V 3+ 0.10Cu 2+ 0.04 P2O7, and it has a C-supported structure with a C mass content of 8.5 wt%.

[0187] 5) XRD analysis of the prepared fluffy powder showed that the crystal structure remained unchanged compared to Comparative Example 16, and was similar to that of undoped Na. 2.0 Fe 0.5 Mn 1.5 Compared to P2O7, the crystal structure remains unchanged; it is still a triclinic crystal system with space group P1.

[0188] Everything else remains the same as in Example 1.

[0189] Comparative Example 1

[0190] 1) Add 2L of deionized water to a beaker, heat to 70℃, and then add 4mol of citric acid monohydrate (C6H2O) sequentially. 10 O8, 0.50 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.50 mol -Mn(NO3)2 aqueous solution (50wt%), the above raw materials are stirred until fully dissolved;

[0191] 2) Then add 4 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) to the above aqueous solution and continue stirring until the raw materials are completely dissolved to form a precursor solution;

[0192] 3) The precursor solution is passed into a spray drying device for spray drying. The inlet temperature is 170℃, the outlet temperature is 90℃, the feed flow rate is 50ml / min, and the compressed air pressure is 0.5Mpa. Approximately 1.2kg of precursor powder is obtained.

[0193] 4) Subsequently, 1.2 kg of precursor powder was transferred to a high-temperature rotary kiln under nitrogen atmosphere protection for heat treatment. First, heat treatment temperature T1 was 400℃, heat treatment time was 2 h, and heating rate was 5℃ / min; heat treatment temperature T2 was 600℃, heat treatment time was 5 h, and heating rate was 2℃ / min. The heat-treated sample was a loose powder with the chemical formula Na₄Fe₂O₃. 0.5 Mn 2.5 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 4.05 wt%.

[0194] 5) Perform XRD tests on the prepared fluffy powder, such as... Figure 1 It belongs to the orthorhombic crystal system, with space group Pn21a.

[0195] Comparative Example 2

[0196] The difference from Comparative Example 1 is as follows:

[0197] 1) 0.49625 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.49625 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.005 mol titanium tetrachloride TiCl4 and 0.0025 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0198] 2) Subsequently, 3.99 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0199] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.99 Fe 0.49625 Mn 2.49625 Ti 4+ 0.005 Zn 2+ 0.0025 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.25 wt%. Other parameters are consistent with Comparative Example 1.

[0200] Comparative Example 3

[0201] The difference from Comparative Example 1 is as follows:

[0202] 1) 0.4925 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4925 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.01 mol titanium tetrachloride TiCl4 and 0.005 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0203] 2) Subsequently, 3.98 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0204] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.98 Fe 0.4925 Mn 2.4925 Ti 4+ 0.01 Zn 2+ 0.005 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 4.33 wt%.

[0205] Everything else remains the same as Comparative Example 1.

[0206] Comparative Example 4

[0207] The difference from Comparative Example 1 is as follows:

[0208] 1) 0.3125 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.3125 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.25 mol titanium tetrachloride TiCl4 and 0.125 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0209] 2) Subsequently, 3.50 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0210] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.50 Fe 0.3125 Mn 2.3125 Ti 4+ 0.25 Zn 2+ 0.125 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.57 wt%.

[0211] Everything else remains the same as Comparative Example 1.

[0212] Comparative Example 5

[0213] The difference from Comparative Example 1 is as follows:

[0214] 1) 0.275 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.275 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.30 mol titanium tetrachloride TiCl4 and 0.15 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0215] 2) Subsequently, 3.40 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0216] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.40 Fe 0.275 Mn 2.275 Ti 4+ 0.30 Zn 2+ 0.15 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.73 wt%.

[0217] Everything else remains the same as Comparative Example 1.

[0218] Comparative Example 6

[0219] The difference from Comparative Example 1 is as follows:

[0220] 1) 0.45 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.45 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 to replace the corresponding Fe source and Mn source;

[0221] 2) Subsequently, 3.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0222] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.45 Mn 2.45 Ti 4+ 0.10 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 5.45 wt%. Other parameters are consistent with Comparative Example 1.

[0223] Comparative Example 7

[0224] The difference from Comparative Example 1 is as follows:

[0225] 1) 0.445 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.445 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.01 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0226] 2) Subsequently, 3.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0227] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.445 Mn 2.445 Ti 4+ 0.10 Zn 2+ 0.01 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.62 wt%.

[0228] Everything else remains the same as Comparative Example 1.

[0229] Comparative Example 8

[0230] The difference from Comparative Example 1 is as follows:

[0231] 1) 0.44 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.44 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.02 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0232] 2) Subsequently, 3.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0233] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.44 Mn 2.44 Ti 4+ 0.10 Zn 2+ 0.02 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.26 wt%.

[0234] Everything else remains the same as Comparative Example 1.

[0235] Comparative Example 9

[0236] The difference from Comparative Example 1 is as follows:

[0237] 1) 0.4075 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.4075 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.085 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0238] 2) Subsequently, 3.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0239] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.4075 Mn 2.4075 Ti 4+ 0.10 Zn 2+ 0.085 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.33 wt%.

[0240] Everything else remains the same as Comparative Example 1.

[0241] Comparative Example 10

[0242] The difference from Comparative Example 1 is as follows:

[0243] 1) 0.40 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.40 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.10 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0244] 2) Subsequently, 3.80 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0245] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.80 Fe 0.40 Mn 2.40 Ti 4+ 0.10 Zn 2+ 0.10 It is (PO4)2P2O7, and it has a C-supported structure with a C mass content of 5.24 wt%.

[0246] Everything else remains the same as Comparative Example 1.

[0247] Comparative Example 11

[0248] The difference from Comparative Example 1 is as follows:

[0249] 1) 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.05 mol silver nitrate AgNO3 to replace the corresponding Fe source and Mn source;

[0250] 2) Subsequently, 3.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0251] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.85 Fe 0.425 Mn 2.425 Ti 4+ 0.10 Ag + 0.05 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.80 wt%.

[0252] Everything else remains the same as Comparative Example 1.

[0253] Comparative Example 12

[0254] The difference from Comparative Example 1 is as follows:

[0255] 1) 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol titanium tetrachloride TiCl4 and 0.05 mol chloroauric acid AuCl3·HCl·4H2O to replace the corresponding Fe source and Mn source;

[0256] 2) Subsequently, 3.85 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0257] 4) The heat-treated sample is a fluffy powder with the chemical formula Na. 3.85 Fe 0.425 Mn 2.425 Ti 4+ 0.10 Au + 0.05 (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.80 wt%.

[0258] Everything else remains the same as Comparative Example 1.

[0259] Comparative Example 13

[0260] The difference from Comparative Example 1 is as follows:

[0261] 1) 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50wt%), and then add 0.10 mol barium nitrate Ba(NO3)2 and 0.05 mol zinc acetate dihydrate Zn(Ac)2·2H2O to replace the corresponding Fe source and Mn source;

[0262] 4) The heat-treated sample is a fluffy powder with the chemical formula Na₄Fe₂O₃. 0.425 Mn 2.425 Ba 2+ 0.10 Zn 2+ 0.05 It is (PO4)2P2O7, and it is a C-supported structure with a C mass content of 3.97 wt%.

[0263] Everything else remains the same as Comparative Example 1.

[0264] Comparative Example 14

[0265] The difference from Comparative Example 1 is as follows:

[0266] 1) 0.425 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O, 2.425 mol Mn(NO3)2 aqueous solution (50 wt%), then add 0.10 mol strontium nitrate Sr(NO3)2 and 0.05 mol zinc acetate dihydrate Zn(Ac). 2. 2H₂O, replacing the corresponding Fe and Mn sources;

[0267] 4) The heat-treated sample is a fluffy powder with the chemical formula Na₄Fe₂O₃. 0.425 Mn 2.425 Sr 2+ 0.10 Zn 2+ 0.05 It is (PO4)2P2O7, and it is a C-supported structure with a C mass content of 4.27 wt%.

[0268] Everything else remains the same as Comparative Example 1.

[0269] Comparative Example 15

[0270] The difference from Comparative Example 1 is as follows:

[0271] 1) 0.5 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O and 1.5 mol Mn(NO3)2 aqueous solution (50wt%) were used to replace the corresponding Fe and Mn sources;

[0272] 2) Subsequently, 3.0 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0273] 4) The heat-treated sample is a fluffy powder with the chemical formula Na3Fe. 0.5 Mn 1.5 (PO4)P2O7; and it is a C-supported structure with a C mass content of 7.3 wt%; other characteristics are consistent with Comparative Example 1;

[0274] 5) The prepared fluffy powder was subjected to XRD test and was found to be orthorhombic crystal system with space group P212121.

[0275] Comparative Example 16

[0276] The difference from Comparative Example 1 is as follows:

[0277] 1) 0.25 mol ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.75 mol-Mn(NO3)2 aqueous solution (50wt%), to replace the corresponding Fe source and Mn source;

[0278] 2) Subsequently, 2.00 mol of sodium dihydrogen phosphate dihydrate NaH2PO4·2H2O (sodium source / phosphorus source) was added to the above aqueous solution to replace the corresponding sodium source / phosphorus source;

[0279] 4) The heat-treated sample is a fluffy powder. 化学式为 Na2Fe0.25Mn0.75P2O7 It is a C-loaded structure; the C mass content is 8.7 wt%; other characteristics are consistent with Comparative Example 1.

[0280] 5) The prepared fluffy powder was subjected to XRD test and was found to be triclinic with space group P1.

[0281] Implement Test Example 1

[0282] The sample prepared in Example 1 was used as the positive electrode active material for sodium-ion batteries. It was mixed uniformly with conductive agent acetylene black and binder polyvinylidene fluoride at a mass ratio of 8.35:0.82:0.83, and then mixed with solvent N-methylpyrrolidone to form a paste. This paste was then applied to an aluminum current collector, dried, and cut into 12.8 mm diameter discs. The areal density of the active material was 8–12 mg / cm² (9.63 mg / cm² in this case), and this was used as the positive electrode. A sodium metal sheet was used as the negative electrode. A 1M NaClO₄ / EC / DEC electrolyte (EC / DEC V / V = 1:1) was used, and a glass fiber membrane was used as the separator. The assembled battery was subjected to charge-discharge tests. The charging cutoff voltage was 4.5V, and the discharging cutoff voltage was 1.5V. The battery performance was tested under 0.2C / ICE / 1.0C conditions, and the test data under these conditions are recorded in Table 1.

[0283] Implement test case 2-23

[0284] The samples obtained in Examples 2#-23# were tested according to the test method of Example 1, and the test data under 0.2C / ICE / 1.0C conditions were recorded in Table 1.

[0285] Comparative Test Case 1

[0286] The sample prepared in Comparative Example 1 was used as the positive electrode active material for sodium-ion batteries. It was mixed uniformly with conductive agent acetylene black and binder polyvinylidene fluoride at a mass ratio of 8.35:0.82:0.83. An appropriate amount of solvent N-methylpyrrolidone was added and mixed thoroughly to form a paste, which was then coated onto an aluminum current collector. After drying, it was cut into discs with a diameter of 12.8 mm. The areal density of the active material was 8–12 mg / cm² (9.51 mg / cm² in this case), and this was used as the positive electrode. A sodium metal sheet was used as the negative electrode. A 1M NaClO₄ / EC / DEC electrolyte (EC / DEC V / V = 1:1) was used, and a glass fiber membrane was used as the separator. The assembled battery was subjected to charge-discharge tests. The charging cutoff voltage was 4.5V, and the discharging cutoff voltage was 1.5V. The battery performance was tested under 0.2C / ICE / 1.0C conditions, and the test data under these conditions are recorded in Table 2.

[0287] Comparative test case 2-23

[0288] The samples obtained from comparative examples 2#-17# were tested according to the test method of comparative test example 1, and the test data under the conditions of 0.2C / ICE / 1.0C were recorded in Table 2.

[0289] Table 1 Examples

[0290]

[0291] Table 2 Comparative Examples

[0292]

[0293] in conclusion

[0294] As can be seen from Example 1, in the composite sodium iron manganese phosphate (Formula I, x = 0.5) material, when Ti is selected at the M1 site... 4+ M2 position uses Zn 2+ The synergistic effect of the two metal ions significantly improves the material's specific capacity, initial efficiency, and rate performance, achieving a specific capacity of 122 mAh / g at 0.2C discharge with an ICE of 97%, and a specific capacity of 105 mAh / g at 1.0C discharge. This effect is comparable to that of Ti. 4+ Zn 2+ The electron distribution of the 3d orbitals and the attraction of the atomic nuclei to electrons are closely related. In the MO6 unit cell structure, the presence of the above-mentioned specific electronic effects has a certain effect on the battery performance of the composite sodium iron manganese phosphate material.

[0295] In addition Ti 4+ Zn 2+ The electronic structures are different, but there is a synergistic effect between them, therefore Ti 4+ Zn2+ The quantitative relationship between them, z1 / z2, is particularly important. As can be seen from Examples 1-5, when Ti 4+ With Zn 2+ When the ratio z1 / z2 is between 0.35 and 0.75, the 0.2C glycine capacity reaches 113-122 mAh / g, the ICE reaches 91%-97%, and the 1.0C glycine capacity reaches 92-105 mAh / g. When z1 / z2 is further optimized to be between 0.5 and 0.6, the effect is even better. For example, in Examples 1 and 3-4, the 0.2C glycine capacity reaches 116-122 mAh / g, the ICE reaches 94%-97%, and the 1.0C glycine capacity reaches 92-105 mAh / g. However, when z1 / z2 is less than 0.35 or greater than 0.75, such as in Comparative Examples 6-10, the 0.2C glycine capacity is only 99-106 mAh / g, the ICE is only 80%-87%, and the 1.0C glycine capacity is as high as 79-83 mAh / g.

[0296] Under appropriate synergistic ratios, compared to the optimal implementation example 1, when the combined amount of the two is low, the synergistic effect of the two will decrease to some extent. For example, in Examples 6 and 7, the 0.2C discharge capacity is 110-114 mAh / g, the ICE is 89.5%-94%, and the 1.0C discharge capacity is 90-94 mAh / g. However, when the amount of the two is further reduced to 0, such as in Comparative Examples 1-3, the 0.2C capacity is only 100-101 mAh / g, the ICE is only 82%-83.5%, and the 1.0C capacity is only 80-80.7 mAh / g, with virtually no effect.

[0297] Under suitable synergistic ratios, compared to the optimal implementation example 1, when the combined amount of both is too high, the performance tends to decline due to a decrease in the number of active sites at transition metal sites, the amount of active sodium, and structural stability. For example, in Examples 8-9, the 0.2C discharge specific capacity is as high as 112-117 mAh / g, the ICE is 90-95%, and the 1.0C discharge specific capacity is 90-93 mAh / g. However, when the amount of both is further increased, such as in Comparative Examples 4-5, the 0.2C specific capacity is only 92-96 mAh / g, the ICE is only 78-79.5%, and the 1.0C specific capacity is only 70-75 mAh / g.

[0298] Furthermore, the technical effects of this invention are also applicable to the doping and synergistic effects of other metal ions at the M1 and M2 sites, as well as to other polyanionic compounds with similar structures, such as Examples 10-23, where the 0.2C specific capacity is 90-120 mAh / g, the ICE is 90%-96%, and the 1.0C specific capacity is 86-101 mAh / g. In contrast, in Comparative Examples 15-16, under the same conditions, the undoped polyanionic compounds have a 0.2C specific capacity of only 88-97 mAh / g, an ICE of only 80%-81%, and a 1.0C specific capacity of only 71-78 mAh / g.

[0299] Similarly, during the implementation of this invention, it was found that if the doping of metal ions at sites M1 and M2 is not appropriate, it will lead to insignificant or even deteriorated technical effects. For example, in Comparative Examples 11-14, the 0.2C specific capacity is 96-98 mAh / g, the ICE is 81%-82%, and the 1.0C specific capacity is 70-75 mAh / g.

Claims

1. A ferromanganese-based polyanionic compound, characterized in that, The iron-manganese polyanionic compound is one or more of the following: phosphate-pyrophosphate complex and pyrophosphate polyanionic compound, wherein the phosphate-pyrophosphate complex and pyrophosphate polyanionic compound has one or more of the structures shown in Formula I, Formula II, and Formula III: Na 4-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 3-x-z1-z2 (PO4)2P2O7 Formula I Na 3-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 2-x-z1-z2 (PO4)P2O7 Formula II Na 2-a Fe 2+ x M1 n1+ z1 M2 n2+ z2 Mn 2+ 1-x-z1-z2 P2O7 formula III Wherein, 4-a, x, z1, z2, and 3-x-z1-z2 represent the molar number of their corresponding elements, and n1 and n2 represent the valence of their corresponding elements; when the iron-manganese polyanionic compound is as shown in Formula I, (4-a)+2x+2*(3-x-z1-z2)+n1*z1+n2*z2=10; When the iron-manganese polyanionic compound is as shown in Formula II, (3-a)+2x+2*(2-x-z1-z2)+n1*z1+n2*z2=7; When the iron-manganese polyanionic compound is as shown in Formula III, (2-a)+2x+2*(1-x-z1-z2)+n1*z1+n2*z2=4; In Equation I, 0 ≤ x < 3, 0.01 <z1<0.2,0.35≤z2 / z1≤0.75; In Equation II, 0 ≤ x < 2, 0.01 <z1<0.2,0.35≤z2 / z1≤0.75; In Equation III, 0 ≤ x < 1, 0.01 <z1<0.15,0.35≤z2 / z1≤0.75; M1 is selected from Ti 3+ Ti 4+ V 3+ V 4+ or V 5+ One or more of them; M2 is selected from Ni 2+ Cu + Cu 2+ or Zn 2+ One or more of them.

2. The iron-manganese polyanionic compound according to claim 1, characterized in that, In Formula I, 0.1≤x≤2.9, 0.05≤z1≤0.10, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤2.5; In Equation II, 0.1≤x≤1.9, 0.05≤z1≤0.10, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤1.5; In Formula III, 0.1≤x≤0.9, 0.03≤z1≤0.05, 0.40≤z2 / z1≤0.60; preferably 0.3≤x≤0.

6.

3. The iron-manganese polyanionic compound according to claim 1, characterized in that, When M1 is selected from Ti 3+ At that time, M2 was selected from Ni 2+ Cu + One or more of them; When M1 is selected from Ti 4+ At that time, M2 was selected from Zn 2+ ; When M1 is selected from V 3+ V 4+ or V 5+ When one or more are present, M2 is selected from Zn. 2+ Cu + or Cu 2+ One or more of them.

4. The iron-manganese polyanionic compound according to claim 1, characterized in that, The iron-manganese polyanionic compound can also be a C-supported compound with the structure shown in Formula I, Formula II, or Formula III, wherein the mass content of C in the C-supported compound is 1wt%-20wt%, preferably 3wt%-10wt%.

5. A method for preparing the iron-manganese-based polyanionic compound according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Mix sodium source, iron source and / or manganese source, M1 source, M2 source, phosphorus source and carbon source evenly in solvent to obtain precursor slurry, and dry to obtain precursor powder P1; Step 2: The precursor powder P1 obtained in Step 1 is heat-treated in an inert atmosphere or an inert atmosphere containing H2. After heat treatment, product P2 of iron-based and / or manganese-based phosphate polyanionic compounds is obtained; the particle size of product P2 is 5-10 micrometers.

6. The preparation method according to claim 5, characterized in that, In Step 1, the method of uniformly mixing the sodium source, iron source and / or manganese source, M1 source, M2 source, phosphorus source, and carbon source includes one or more of ball milling, pot milling, and sand milling; the solid content of the precursor slurry is 15 wt% to 60 wt%, preferably 25 wt% to 45 wt%: The solvent is water, ethanol, or a mixed solvent of water and ethanol. The proportion of water in the mixed solvent by mass accounts for (30 - 80) wt% of the total mass of the mixed solvent, preferably (45 - 55) wt%, and the proportion of ethanol in the mixed solvent by mass accounts for (20 - 70) wt% of the total mass of the mixed solvent, preferably (45 - 55) wt%; The drying method is spray drying. Among them, the feed flow rate is controlled at 20 mL / min to 60 mL / min, the inlet air temperature is controlled at 140°C to 225°C, the outlet air temperature is 70°C to 120°C, and the compressed air pressure is 0.2 Mpa to 0.7 Mpa; In Step 2, in the inert atmosphere containing H2, the molar content of H2 is 0 - 50%, preferably 10% - 20%; the heat treatment includes a process of treating at the first temperature T1 sequentially and a process of treating at the second temperature T2 after treating at the first temperature T1; the first temperature T1 is 200 ≤ T1 ≤ 400°C, and the treatment time is 0.5 - 6 h; the second temperature T2 is 400°C < T1 ≤ 750°C, and the treatment time is 3 - 20 h; the difference between T2 and T1 is greater than or equal to 50°C.

7. The preparation method according to claim 5, wherein When the iron-manganese-based polyanionic compound has the structure shown in Formula I, the molar ratio of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source is 4 - a:x:z1:z2:3 - x - z1 - z2:4, and the molar ratios of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source are based on the molar amounts of sodium, iron, manganese, M1, M2, and phosphorus respectively; When the iron-manganese-based polyanionic compound has the structure shown in Formula II, the molar ratio of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source is 3 - a:z1:z2:2 - x - z1 - z2:3, and the molar ratios of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source are based on the molar amounts of sodium, iron, manganese, M1, M2, and phosphorus respectively; When the iron-manganese-based polyanionic compound has the structure shown in Formula III and the phosphate-based polyanionic compound has the structure shown in Formula IV, the molar ratio of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source is 2 - a:x:z1:z2:1 - x - z1 - z2:2, and the molar ratios of the sodium source, iron source, manganese source, M1 source, M2 source, and phosphorus source are based on the molar amounts of sodium, iron, manganese, M1, M2, and phosphorus respectively.

8. The preparation method according to claim 6 or 7, wherein: The sodium source is selected from one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, sodium citrate, sodium oxalate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, and sodium hydrogen pyrophosphate; The iron source is selected from one or more of the following: iron powder, iron(II) oxide, ferric oxide, ferrous oxide, ferric oxalate, ferrous oxalate (dihydrate), ferric phosphate, ferric pyrophosphate, ferrous citrate, ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric acetate, ferrous ammonium sulfate, ferric citrate, ferric ammonium citrate, and sodium ferric citrate succinate. The manganese source is selected from one or more of the following: manganese monoxide, manganese dioxide, manganese trioxide, manganese tetroxide, manganese hydroxide, manganese sulfate, manganese chloride, manganese nitrate, manganese phosphate, manganese phosphate, manganese dihydrogen phosphate, manganese nitrate tetrahydrate, and manganese nitrate solution. The M1 and M2 sources are respectively selected from one or more of the oxides, hydroxides, acetates, nitrates, carbonates, oxalates, phosphates, pyrophosphates, chlorides, citrates, and sulfates corresponding to the M1 and M2 sources, respectively. The phosphorus source is selected from one or more of the following: ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, pyrophosphate, sodium pyrophosphate, and sodium hydrogen pyrophosphate. The carbon source is one or more of the following: polyethylene glycol, cellulose, starch, polyvinyl alcohol, formic acid, acetic acid, citric acid, malic acid, lactic acid, oxalic acid, tartaric acid, ascorbic acid, cyclohexanediol, salicylic acid, caffeic acid, ethylene acrylate copolymer, maleic acid copolymer, polyacrylic acid, polyvinyl acid, polyamic acid, and polybutenoic acid.

9. The application of the iron-manganese polyanionic compound according to any one of claims 1-4 or the iron-manganese polyanionic compound prepared by the preparation method according to any one of claims 5-8 as a positive electrode active material in sodium-ion batteries, characterized in that, The pyrophosphate and / or phosphate-pyrophosphate complex polyanionic compounds are used as active materials in the positive electrode of sodium-ion batteries.

10. The application according to claim 9, characterized in that, In the positive electrode material of sodium-ion batteries, the content of the pyrophosphate and / or phosphoric acid pyrophosphate composite polyanionic compound electrode material is (60-98) wt%. The positive electrode material also contains a conductive agent and a binder, and the mass ratio of the pyrophosphate and / or phosphoric acid pyrophosphate composite polyanionic compound, the conductive agent and the binder is (60-98) wt%:(1-39) wt%:(1-39) wt%. The conductive agent is one or more of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene. The adhesive is one or more of polyvinylidene fluoride: PVDF5130, HSV900, and kynar761A.

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