Non-destructive fast-charging positive electrode material based on ultrasmall particle na xfe ym z(so 4) 3, and preparation method therefor and application thereof

Abstract

A non-destructive fast-charging positive electrode material based on ultrasmall particle NaxFeyMz(SO4)3, and a preparation method therefor and an application thereof. The molecular formula of the positive electrode material is NaxFeyMz(SO4)3, wherein 1.0≤x≤3.0, 0.5≤y≤2.0, 0.5≤z≤1.5, and M is a transition metal; and the particle size of the positive electrode material is 10-80 nm. The non-destructive fast-charging positive electrode material is synthesized by means of low-temperature solvothermal, flash drying and low-temperature calcination methods, the positive electrode material can be used in a sodium ion battery, and the ultrasmall particle size of the positive electrode material is conducive to shortening the diffusion path of ions and electrons, thereby achieving fast transport of sodium ions; in addition, partial substitution of transition metal ions further improves the reaction activity of the material, thereby improving the rate performance of the material.

Description

Based on ultra-small particles of Na x Fe y M z (SO4)3 lossless fast-charging positive electrode material and its preparation method and application Technical Field

[0001] The present invention belongs to the field of electrode materials, and in particular relates to an electrode material based on ultra-small particles of Na x Fe y M z Lossless fast-charging positive electrode material of (SO4)3 and its preparation method and application. Background Art

[0002] Lithium-ion batteries (LIBs) are widely used in portable electronic devices and electric vehicles due to their small size, light weight, and high energy density. However, the global scarcity and uneven distribution of lithium resources have limited their large-scale development. Sodium-ion batteries (SIBs) share a similar structure and operating mechanism, both based on a rocking-chair electrochemical energy storage mechanism. Furthermore, sodium resources are abundant and inexpensive, spurring a surge in SIB research and development. The cathode material is the most crucial component of the SIB system, largely determining its performance, including cost, energy density, rate capability, and cycle life. An ideal cathode material should possess the following characteristics: First, it should be able to provide active sodium ions. Second, it should contain a suitable variable valence element to provide a relatively high redox potential, thereby achieving high battery operating voltage and energy density. Third, it should ideally be safe and non-toxic in air storage, a trend driven by green chemistry and a future trend. Furthermore, stable storage significantly enhances battery consistency. The development of low-cost, highly electrochemically reversible, and long-cycle-life SIB cathode materials remains a key challenge, priority, and hot topic in current research, both domestically and internationally.

[0003] In recent years, reports on cathode materials for sodium-ion batteries mainly include layered oxides, Prussian blue systems, and polyanion systems. x VO2, Na x MnO2, etc., because the layered skeletons are only connected by weak ionic bonds, they are prone to irreversible phase transitions during the electrochemical process, resulting in insufficient cycle performance. 1.72MnFe(CN)6, for example, is prone to forming [Fe(CN)6] vacancies in its structure and is easily occupied by crystal water, resulting in poor battery cycling performance and low Coulombic efficiency. Sodium vanadium phosphate cathode materials in polyanion systems face a certain risk of resource shortage due to the scarcity of vanadium resources in the Earth's crust. Furthermore, vanadium is environmentally unfriendly, increasing the risks of use. Therefore, there is an urgent need for a sodium-ion battery cathode material that can meet the needs of industrial production, is environmentally friendly, low-cost, and has excellent electrochemical performance to meet the application needs of sodium-ion batteries.

[0004] The sodium, iron and sulfur elements required for sodium ferric sulfate are all elements with abundant resources in the earth's crust, so it has the inherent advantage of low raw material cost. 2+ / Fe 3+ Strong inductive effect, sodium iron sulfate has a working voltage of up to 3.8V in iron-based polyanion cathode materials, coupled with its suitable theoretical specific capacity of 120mAh g -1 The theoretical energy density of this cathode material is as high as 456Wh / kg, second only to lithium iron phosphate cathodes. However, the sodium iron sulfate material synthesized by existing technologies has large particle size and low material utilization, resulting in poor rate performance, cycle stability, and low sodium storage capacity, which seriously hinders its industrialization process.

[0005] In order to further promote the practical application of sodium ferric sulfate as a cathode material for sodium ion batteries, it is crucial to modify sodium ferric sulfate. In recent years, many studies have been conducted to regulate the electrochemical properties of sodium ferric sulfate materials through strategies such as ion doping and coating. Cao et al. constructed a graphene-coated NaFeSO4 in a three-dimensional graphene microsphere network by spray drying. 2.4 Fe 1.8 (SO4)3 nanoparticles. The unique micro-nanostructure and component advantages of the material enable the electrode to exhibit good rate properties and long cycle life, but the entire preparation process takes too long, lasting about 48 hours, and the required conditions are relatively harsh, requiring processes such as spray drying (J.Energy Chem., 2021, 54, 564). The Chinese invention patent with publication number CN 106058251 A discloses a method for preparing a core-shell structure Na2Fe2(SO4)3@alumina composite material with good physical and chemical properties, but the addition of alumina will lead to a decrease in the energy density of the material, and the final electrode discharge capacity is 69mAh g -1 In addition, the existing synthesis method of sodium iron sulfate materials requires high temperatures and has a low safety factor. The resulting material particles are large, resulting in low material utilization and poor electrical properties, making it difficult to meet the needs of high-rate charge and discharge.

[0006] Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method based on ultra-small particles of Na x Fe y M z (SO4)3 lossless fast-charging cathode material and its preparation method and application, a nanostructured cathode with ultra-small particles of Na was synthesized by low-temperature solvent thermal, flash drying and low-temperature calcination. x Fe y M z (SO4)3 is a lossless fast-charging positive electrode material, and this positive electrode material is used in sodium-ion batteries. Its ultra-small particle size is conducive to shortening the diffusion path of ions and electrons, realizing the rapid transmission of sodium ions; in addition, the partial substitution of transition metal ions further enhances the reaction activity of the material, thereby improving the rate performance of the material.

[0008] In order to solve the above technical problems, the first aspect of the present invention provides a positive electrode material, the molecular formula of the positive electrode material is Na x Fe y M z (SO4)3, wherein 1.0≤x≤3.0, 0.5≤y≤2.0, 0.5≤z≤1.5, and M is a transition metal; the particle size of the positive electrode material is between 10-80 nm.

[0009] Specifically, the particle size of the positive electrode material of the present invention is at the nanometer level, and the nanostructured electrode material has a shorter ion diffusion path and a larger specific surface area, which is conducive to the rapid transmission of sodium ions and can provide abundant active energy storage sites, thereby improving the specific capacity of the material. At the same time, the nanostructure of the positive electrode material is conducive to alleviating the volume expansion caused by the insertion and extraction of sodium ions, thereby improving the cycle performance. In addition, the present invention partially replaces the iron ions with transition metal ions to further improve the reactivity of the material, thereby improving the rate performance of the material.

[0010] Preferably, the transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ag, Pt, Au, and Hg.

[0011] More preferably, x=2.0, y=1, z=1; and the transition metal is at least one of Mn and Ni.

[0012] A second aspect of the present invention provides a method for preparing a positive electrode material, which is used to prepare the positive electrode material described in the first aspect, comprising the following steps:

[0013] (1) dispersing a sodium source, an iron source, a transition metal source, and a sulfur source in a solvent to obtain a suspension;

[0014] (2) heating the suspension to perform a solvent thermal reaction; after cooling, separating, washing, and flash drying the product of the solvent thermal reaction in sequence to obtain Na-based x Fe y M z Powder particles of (SO4)3;

[0015] (3) calcining the powder particles under an inert gas atmosphere to obtain the positive electrode material.

[0016] Specifically, the present invention adopts the method of low-temperature solvent heat, flash drying and low-temperature calcination to synthesize a kind of ultra-small particle Na x Fe y M z (SO4)3 is a lossless fast-charging positive electrode material. Compared with the harsh conditions of the prior art such as high preparation temperature and long time, the preparation method of the present invention is simple and easy, and has low energy consumption, material cost and equipment requirements, and is more suitable for large-scale industrial production. Among them, low-temperature solvent heat can make the precursors more evenly mixed in the solvent, providing a guarantee for the uniformity of the synthetic product; the addition of a transition metal source can further enhance the reaction activity of the product; flash drying is conducive to batch and rapid reduction of the crystalline water content in the product, and promotes a large amount of nucleation of solid matter, preventing crystal growth, thereby forming a precursor of ultra-small particles; calcination in an inert gas atmosphere can promote the reaction of the precursor to generate the product and improve the product cycle performance.

[0017] Preferably, the sodium source is selected from at least one of sodium sulfate, sodium bisulfate, sodium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, sodium phosphate, sodium nitrate, sodium phosphite, sodium formate, sodium propionate, sodium acrylate, sodium benzoate, sodium hypochlorite, sodium chlorate, sodium thiosulfate, sodium persulfate, sodium silicate, sodium bromate, sodium bromide, sodium iodide, sodium fluoride, sodium bisulfite, sodium nitrite, sodium oxalate, sodium persulfate, sodium hydroxide, sodium pyrosulfate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium metabisulfite, sodium pyrophosphate, sodium hydrogen phthalate, sodium hydrogen oxalate, sodium sulfite, sodium sorbate, trisodium phosphate, sodium gluconate, sodium oleate and hydrates of the foregoing substances.

[0018] More preferably, the sodium source is at least one of sodium sulfate, sodium bisulfate, and sodium bicarbonate.

[0019] Preferably, the iron source is selected from at least one of ferric sulfate, ferrous oxide, ferric chloride, ferric nitrate, ferric acetate, ferrous bromide, ferrous nitrate, ferrous phosphate, ferrous iodide, ferrous acetate, ferrous metasilicate, ferrous metatitanate, disodium ferric sulfate, ammonium ferrous sulfate, ferrous carbonate, ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous oxide, ferrous dioxide, ferric chloride, ferric hydroxide and hydrates of the foregoing substances.

[0020] More preferably, the iron source is ferrous sulfate.

[0021] Preferably, the transition metal source is at least one selected from soluble salts of scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, zinc, silver, platinum, gold, mercury and hydrates thereof.

[0022] More preferably, the transition metal source is at least one of manganese sulfate and nickel sulfate.

[0023] Preferably, the sulfur source is selected from at least one of ferric sulfate, ferrous sulfate, sodium bisulfate, potassium sulfate, ferrous dithionite, ferrous thiosulfate, ferrous dithionate, ferrous tetrasulfide, sodium sulfate, sodium sulfite, sodium dithionite, sodium thiosulfate, sodium dithionite, sulfurous acid, sulfuric acid, ammonium persulfate, potassium persulfate, sodium persulfate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate and hydrates of the above substances.

[0024] More preferably, the sulfur source is ferrous sulfate and / or sodium bisulfate.

[0025] Preferably, the molar ratio of the sodium source, the iron source, the transition metal source and the sulfur source is (1-3): (0.5-2): (0.5-1.5): 3.

[0026] More preferably, the molar ratio of the sodium source, the iron source, the transition metal source and the sulfur source is 2:1:1:3.

[0027] Preferably, the solvent is selected from at least one of water, methanol, ethanol, acetone, ethylene glycol, and pyridine.

[0028] More preferably, the solvent is water.

[0029] Preferably, in step (2), the temperature of the solvent thermal reaction is 40-220°C; more preferably, the temperature of the solvent thermal reaction is 40-220°C.

[0030] Preferably, in step (2), the solvent thermal reaction time is 4-12 hours; more preferably, the solvent thermal reaction time is 4-8 hours.

[0031] Preferably, in step (2), the moisture content of the flash-dried imported material is 5-40 wt %; more preferably, the moisture content of the flash-dried imported material is 5-15 wt %.

[0032] Preferably, in step (2), the drying chamber size of the flash drying is 0.5-10m 3 More preferably, the flash drying chamber size is 1-3m 3 .

[0033] Preferably, in step (2), the temperature of the flash drying is 120-350°C; more preferably, the temperature of the flash drying is 120-200°C.

[0034] Preferably, in step (2), the flash drying time is 0.2-6 hours; more preferably, the flash drying time is 0.2-1 hour.

[0035] Preferably, in step (2), the gas flow rate of the flash drying is 1-30 m / s; more preferably, the gas flow rate of the flash drying is 1-10 m / s.

[0036] Preferably, in step (3), the calcination temperature is 200-400°C; more preferably, the calcination temperature is 250-350°C.

[0037] Preferably, in step (3), the heating rate of the calcination treatment is 0.5-10°C / min; more preferably, the heating rate of the calcination treatment is 1-4°C / min.

[0038] Preferably, in step (3), the calcination treatment time is 2-48 hours; more preferably, the calcination treatment time is 4-12 hours.

[0039] Preferably, in step (3), the inert gas is at least one of nitrogen, argon, or a mixture of argon and hydrogen.

[0040] The third aspect of the present invention provides a sodium ion battery positive electrode plate, comprising a current collector and a positive electrode material layer coated on the surface of the current collector; the positive electrode material layer contains a positive electrode active material, and the positive electrode active material is the positive electrode material described in the first aspect.

[0041] Preferably, the positive electrode material layer further contains a conductive agent and a binder.

[0042] The present invention has no special requirements for the conductive agent and the binder, and can use the conductive agent (such as conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fiber, graphene, reduced graphene oxide, etc.) and binder (such as polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose, SBR rubber, polyolefins, etc.) commonly used in the positive electrode of sodium ion batteries.

[0043] A fourth aspect of the present invention provides a sodium ion battery, comprising the sodium ion battery positive electrode sheet described in the third aspect.

[0044] The fifth aspect of the present invention provides an application of the sodium ion battery described in the fourth aspect.

[0045] Preferably, the applications include mobile electronic communication equipment, electric vehicles, electric bicycles, energy storage batteries, power batteries or energy storage power stations.

[0046] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0047] (1) The positive electrode material of the present invention is sodium iron sulfate partially substituted by transition metal x Fe y M z (SO4)3, this material has an ultra-small particle size at the nanoscale, which greatly shortens the diffusion distance of substances such as ions / electrons and electrolytes, reduces the diffusion barrier of sodium ions, is conducive to the rapid diffusion of sodium ions, and realizes fast charging and fast discharging of electrode materials. In addition, because the product has small grains and sufficient gaps between the grains, it is conducive to alleviating the deformation stress generated by the embedding / ejection of sodium ions, improving the cycle stability of the product, and realizing lossless charging and discharging of the product. At the same time, the material has a large specific surface area, which can provide abundant active energy storage sites and promote the utilization of the material's specific capacity. In addition, the partial substitution of transition metal ions further improves the reaction activity of the material, thereby improving the material's rate performance.

[0048] (2) The sodium ion battery positive electrode material of the present invention is prepared by a method of low-temperature solvent heat, flash drying and low-temperature calcination. The process is simple and easy to operate, with low energy consumption, material cost and equipment requirements, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG1 is a FESEM image of the cathode material prepared in Example 1;

[0050] FIG2 is a FESEM image of the positive electrode material prepared in Comparative Example 1;

[0051] FIG3 is a comparison of the cycle performance of the positive electrode materials prepared in Example 1 and Comparative Examples 1-2;

[0052] FIG4 is a comparison chart of the rate performance of the positive electrode materials prepared in Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0053] The present invention is described in detail below with reference to the examples to facilitate understanding of the present invention by those skilled in the art. It is necessary to point out that the examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned invention should still fall within the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0054] Example 1

[0055] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. A method for preparing the positive electrode material comprises the following steps:

[0056] (1) Weigh 0.05 mol of sodium bicarbonate, 0.1 mol of ferrous sulfate, 0.1 mol of manganese sulfate, and 0.1 mol of sodium sulfate, respectively, and disperse them in 50 ml of water. Stir magnetically until completely dissolved to obtain a suspension.

[0057] (2) The suspension obtained in step (1) was placed in a hydrothermal kettle with an inner lining volume of 80 mL, and a solvent thermal reaction was carried out at 100° C. for 4 h; after cooling naturally to room temperature, the solvent thermal reaction product was centrifuged and then washed with ethanol and deionized water to obtain a primary product with a water content of about 20%. The primary product was then placed in a drying chamber with a volume of 1 m 3 The mixture was flash dried in a dryer at 200°C and a gas flow rate of 2 m / s for 0.5 h to obtain powder particles based on Na2FeMn(SO4)3;

[0058] (3) The powder particles obtained in step (2) were calcined at 350° C. for 8 h under argon atmosphere, wherein the heating rate was 1° C. / min, to obtain the Na 2 FeMn (SO 4 ) 3 positive electrode material of this embodiment.

[0059] FIG1 is a field emission scanning electron microscope (FESEM) image of the cathode material prepared in Example 1. As can be seen from FIG1 , the size of the prepared cathode material is relatively uniform, and the particle size is about 10-80 nm.

[0060] Example 2

[0061] A positive electrode material, whose chemical formula is: Na3Fe 0.5 The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol of ferrous sulfate and 0.1 mol of sodium sulfate used in step (1) are replaced by 0.05 mol of ferrous sulfate and 0.15 mol of sodium sulfate, and the rest are the same as those of Example 1.

[0062] Example 3

[0063] A positive electrode material with the chemical formula: NaFeMn 1.5 (SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol manganese sulfate and 0.1 mol sodium sulfate used in step (1) are replaced by 0.15 mol manganese sulfate and 0.05 mol sodium sulfate, and the rest are the same as those of Example 1.

[0064] Example 4

[0065] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.05 mol sodium bicarbonate used in step (1) is replaced by 0.05 mol sodium acetate, and the rest is the same as that of Example 1.

[0066] Example 5

[0067] A positive electrode material having the chemical formula Na2FeMn(SO4)3. The preparation method of the positive electrode material is the same as that of Example 1 in that the 0.1 mol of ferrous sulfate used in step (1) is replaced by 0.05 mol of ferric sulfate, and the amounts of sodium bicarbonate and sodium sulfate are changed to 0.15 mol and 0.05 mol, respectively. The rest of the preparation method is the same as that of Example 1.

[0068] Example 6

[0069] A positive electrode material having the chemical formula Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol ferrous sulfate and 0.1 mol manganese sulfate used in step (1) are replaced with 0.15 mol ferrous sulfate and 0.05 mol manganese sulfate, and the rest is the same as that of Example 1.

[0070] Example 7

[0071] A positive electrode material having the chemical formula Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.05 mol sodium bicarbonate and 0.1 mol sodium sulfate used in step (1) are replaced with 0.25 mol sodium bicarbonate and 0.1 mol ammonium sulfate, and the rest is the same as that of Example 1.

[0072] Example 8

[0073] A positive electrode material, whose chemical formula is: Na3FeMn 0.5 (SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol manganese sulfate and 0.1 mol sodium sulfate used in step (1) are replaced by 0.05 mol manganese sulfate and 0.15 mol sodium sulfate, and the rest are the same as those of Example 1.

[0074] Example 9

[0075] A positive electrode material with the chemical formula: Na2Fe 1.5 Mn 0.5(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol ferrous sulfate and 0.1 mol manganese sulfate used in step (1) are replaced by 0.15 mol ferrous sulfate and 0.05 mol manganese sulfate, and the rest are the same as those of Example 1.

[0076] Example 10

[0077] A positive electrode material with the chemical formula: Na2Fe 0.5 Mn 1.5 (SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol ferrous sulfate and 0.1 mol manganese sulfate used in step (1) are replaced by 0.05 mol ferrous sulfate and 0.15 mol manganese sulfate, and the rest are the same as those of Example 1.

[0078] Example 11

[0079] A positive electrode material having the chemical formula: Na2FeNi(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol nickel sulfate, and the rest is the same as that of Example 1.

[0080] Example 12

[0081] A positive electrode material having the chemical formula: Na2FeNi(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol nickel fluoride, and the rest is the same as that of Example 1.

[0082] Example 13

[0083] A positive electrode material having the chemical formula: Na2FeNi(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol nickel nitrate, and the rest is the same as that of Example 1.

[0084] Example 14

[0085] A positive electrode material having the chemical formula: Na2FeCo(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol cobalt sulfate, and the rest is the same as that of Example 1.

[0086] Example 15

[0087] A positive electrode material having the chemical formula: Na2FeCo(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol cobalt fluoride, and the rest is the same as that of Example 1.

[0088] Example 16

[0089] A positive electrode material having the chemical formula: Na2FeCo(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol cobalt nitrate, and the rest is the same as that of Example 1.

[0090] Example 17

[0091] A positive electrode material having the chemical formula: Na2FeZn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol zinc sulfate, and the rest is the same as that of Example 1.

[0092] Example 18

[0093] A positive electrode material having the chemical formula: Na2FeZn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol zinc fluoride, and the rest is the same as that of Example 1.

[0094] Example 19

[0095] A positive electrode material having the chemical formula: Na2FeZn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the 0.1 mol manganese sulfate used in step (1) is replaced by 0.1 mol zinc nitrate, and the rest is the same as that of Example 1.

[0096] Example 20

[0097] A positive electrode material with the chemical formula: Na2Fe 1.5 Mn 0.5 (SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that in step (1), the molar ratio of the sodium source: the iron source: the transition metal source: the sulfur source is 2.5:1.5:0.5:3, and the specific raw materials are 0.05 mol of sodium bicarbonate, 0.15 mol of ferrous sulfate, 0.05 mol of manganese sulfate and 0.1 mol of sodium sulfate. The rest is the same as that of Example 1.

[0098] Example 21

[0099] A positive electrode material with the chemical formula: Na2Fe 0.5 Mn1.5 (SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that in step (1), the molar ratio of the sodium source: the iron source: the transition metal source: the sulfur source is 2.5:0.5:1.5:3, and the specific raw materials are 0.05 mol of sodium bicarbonate, 0.05 mol of ferrous sulfate, 0.15 mol of manganese sulfate and 0.1 mol of sodium sulfate. The rest is the same as that of Example 1.

[0100] Example 22

[0101] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent used in step (2) is ethanol, and the rest is the same as that of Example 1.

[0102] Example 23

[0103] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent heating temperature used in step (2) is 40°C, and the rest is the same as that of Example 1.

[0104] Example 24

[0105] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal temperature used in step (2) is 80°C, and the rest is the same as that of Example 1.

[0106] Example 25

[0107] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal temperature used in step (2) is 160°C, and the rest is the same as that of Example 1.

[0108] Example 26

[0109] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal temperature used in step (2) is 220°C, and the rest is the same as that of Example 1.

[0110] Example 27

[0111] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal reaction time in step (2) is 2 hours, and the rest is the same as that of Example 1.

[0112] Example 28

[0113] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal reaction time in step (2) is 6 hours, and the rest is the same as that of Example 1.

[0114] Example 29

[0115] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal reaction time in step (2) is 8 hours, and the rest is the same as that of Example 1.

[0116] Example 30

[0117] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the solvent thermal reaction time in step (2) is 12 hours, and the rest is the same as that of Example 1.

[0118] Example 31

[0119] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the moisture content of the imported material in step (2) is 10%, and the rest is the same as that of Example 1.

[0120] Example 32

[0121] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the moisture content of the imported material in step (2) is 30%, and the rest is the same as that of Example 1.

[0122] Example 33

[0123] A positive electrode material, whose chemical formula is: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the volume of the drying chamber in step (2) is 0.5m 3 , the rest are the same as in Example 1.

[0124] Example 34

[0125] A positive electrode material, whose chemical formula is: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the volume of the drying chamber in step (2) is 2m 3 , the rest are the same as in Example 1.

[0126] Example 35

[0127] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the drying chamber temperature in step (2) is 120°C, and the rest is the same as that of Example 1.

[0128] Example 36

[0129] A positive electrode material having a chemical formula of Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the drying chamber temperature in step (2) is 150°C, and the rest is the same as that of Example 1.

[0130] Example 37

[0131] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the drying chamber temperature in step (2) is 250°C, and the rest is the same as that of Example 1.

[0132] Example 38

[0133] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the drying time in step (2) is 0.2 h, and the rest is the same as that of Example 1.

[0134] Example 39

[0135] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the drying time in step (2) is 1 hour, and the rest is the same as that of Example 1.

[0136] Example 40

[0137] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the gas flow rate in the drying chamber in step (2) is 1 m / s, and the rest is the same as that of Example 1.

[0138] Example 41

[0139] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the gas flow rate in the drying chamber in step (2) is 5 m / s, and the rest is the same as that of Example 1.

[0140] Example 42

[0141] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the temperature of the calcination treatment in step (3) is 200°C, and the rest is the same as that of Example 1.

[0142] Example 43

[0143] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the temperature of the calcination treatment in step (3) is 300°C, and the rest is the same as that of Example 1.

[0144] Example 44

[0145] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the temperature of the calcination treatment in step (3) is 400°C, and the rest is the same as that of Example 1.

[0146] Example 45

[0147] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the heating rate of the calcination treatment in step (3) is 0.5°C / min, and the rest is the same as that of Example 1.

[0148] Example 46

[0149] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the heating rate of the calcination treatment in step (3) is 2°C / min, and the rest is the same as that of Example 1.

[0150] Example 47

[0151] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the heating rate of the calcination treatment in step (3) is 4°C / min, and the rest is the same as that of Example 1.

[0152] Example 48

[0153] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the calcination time in step (3) is 2 hours, and the rest is the same as that of Example 1.

[0154] Example 49

[0155] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the calcination time in step (3) is 24 hours, and the rest is the same as that of Example 1.

[0156] Example 50

[0157] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material is different from that of Example 1 in that the calcination time in step (3) is 48 hours, and the rest is the same as that of Example 1.

[0158] Example 51

[0159] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The difference between the preparation method of the positive electrode material and that of Example 1 is that the gas atmosphere for the calcination treatment in step (3) is nitrogen, and the rest is the same as that of Example 1.

[0160] Example 52

[0161] A positive electrode material having the chemical formula: Na2FeMn(SO4)3. The preparation method of the positive electrode material differs from that of Example 1 in that the gas atmosphere for the calcination treatment in step (3) is a mixture of argon and hydrogen (volume ratio of 9.5:0.5), and the rest is the same as that of Example 1.

[0162] Example 53

[0163] A sodium ion battery, wherein the positive electrode active material is the positive electrode material Na2FeMn(SO4)3 prepared in Example 1. The preparation method of the sodium ion battery comprises the following steps:

[0164] (1) Preparation of battery positive electrode: Na2FeMn(SO4)3 powder, carbon black, and polyvinylidene fluoride were added to an appropriate amount of N-methylpyrrolidone in a mass ratio of 8:1:1, and the mixture was thoroughly ground to obtain a uniform slurry; the slurry was then evenly coated on the surface of aluminum foil and vacuum dried; the dried electrode sheet was cut into discs with a diameter of 10 mm, and the discs were compacted and used as battery positive electrode sheets for standby use;

[0165] (2) Preparation of battery negative electrode: Press sodium metal into thin sheets and cut into discs with a diameter of 12 mm to serve as battery negative electrode sheets;

[0166] (3) Battery assembly: A glass fiber film is used as a diaphragm, and 1M sodium hexafluorophosphate is dissolved in a solvent of propylene carbonate and fluoroethylene carbonate (volume ratio 95:5) as an electrolyte. In an inert gas-protected glove box, the battery positive electrode sheet prepared in step (1), the diaphragm, and the battery negative electrode sheet prepared in step (2) are stacked tightly in sequence, and the electrolyte is added dropwise to completely soak the diaphragm. Then, the stacked part is encapsulated in a button battery shell to complete the battery assembly.

[0167] Examples 54-104

[0168] The positive electrode materials used in the sodium ion batteries of Examples 54-104 correspond to the positive electrode materials prepared in Examples 2-52, respectively, and the preparation methods of each sodium ion battery are the same as that of Example 53.

[0169] Comparative Example 1

[0170] A sodium ion battery, the preparation method of which differs from that of Example 53 in that, when preparing the battery positive electrode, the positive electrode material is replaced with Na2FeMn(SO4)3 positive electrode material particles prepared by ball milling, and all other aspects are the same as those of Example 53. The specific preparation method is as follows: 0.05 mol of sodium bicarbonate, 0.1 mol of ferrous sulfate, 0.1 mol of manganese sulfate, and 0.1 mol of sodium sulfate are dried and directly mixed, and then ball-milled in a ball mill for 12 hours to fully mix the powders; the ball-milled material is then transferred to a magnetic boat, placed in a tube furnace, and calcined at 350°C in an argon atmosphere for 8 hours at a heating rate of 1°C / min. After calcination, the Na2FeMn(SO4)3 positive electrode material particles are obtained by grinding.

[0171] Figure 2 is a FESEM image of the positive electrode material prepared by the ball milling method in Comparative Example 1. As can be seen from Figure 2, the particle size of the Na2FeMn(SO4)3 positive electrode material prepared by the ball milling method is in the range of 1-5μm, which is relatively large and easily agglomerated to form a bulk material.

[0172] Comparative Example 2

[0173] A sodium ion battery, the preparation method of which differs from that of Example 53 in that, when preparing the positive electrode, the positive electrode material is changed to a Na2Fe2(SO4)3 positive electrode material, and the rest is the same as that of Example 53. The preparation method of the Na2Fe2(SO4)3 positive electrode material differs from that of Example 1 in that the ferrous sulfate is 0.2 mol and no manganese sulfate is added, and the rest is the same as that of Example 1.

[0174] Comparative Example 3

[0175] A sodium ion battery, the preparation method of which differs from that of Example 53 in that, when preparing the positive electrode, the positive electrode material is changed to a Na2Fe2(SO4)3 positive electrode material, and the rest is the same as that of Example 53. The preparation method of the Na2Fe2(SO4)3 positive electrode material differs from that of Example 1 in that the ferrous sulfate content is 0.2 mol, and no manganese sulfate and sodium bicarbonate are added. The drying process uses a solvent evaporation method, and the mixed solution is dried at 130°C under continuous magnetic stirring; the rest is the same as that of Example 1.

[0176] Comparative Example 4

[0177] A sodium ion battery, the preparation method of which differs from that of Example 53 in that, when preparing the positive electrode, the positive electrode material is changed to Na2FeMn(SO4)3 positive electrode material; otherwise, the preparation method is the same as that of Example 53. The preparation method of the Na2FeMn(SO4)3 positive electrode material differs from that of Example 1 in that sodium bicarbonate is not added, and the drying process utilizes a solvent evaporation method, with the mixed solution dried at 130°C under continuous magnetic stirring. Otherwise, the preparation method is the same as that of Example 1.

[0178] Comparative Example 5

[0179] A sodium ion battery, the preparation method of which differs from that of Example 53 in that, when preparing the positive electrode, the positive electrode material is changed to Na2FeNi(SO4)3 positive electrode material; otherwise, the preparation method is the same as that of Example 53. The preparation method of the Na2FeNi(SO4)3 positive electrode material differs from that of Example 1 in that the nickel sulfate is 0.1 mol, and no manganese sulfate or sodium bicarbonate is added. The drying process utilizes a solvent evaporation method, and the mixed solution is dried at 130°C under continuous magnetic stirring. Otherwise, the preparation method is the same as that of Example 1.

[0180] Performance Testing

[0181] Performance testing of the sodium-ion batteries prepared in Examples 53-104 and Comparative Examples 1-5 was conducted using a BTSDA test system from Shenzhen Xinwei Electronics Co., Ltd. in a constant temperature and humidity chamber (25°C, 35%) over a voltage range of 2-4.5V. The batteries were cycled for 500 cycles at current densities of 1C and 10C (1C = 120 mAh / g), respectively. The test results are shown in Table 1.

[0182] Table 1: Comparative table of electrochemical performance tests of Examples 53-104 and Comparative Examples 1-5

[0183] As can be seen from Table 1, the sodium ion batteries (Examples 53-104) assembled with the positive electrode materials prepared in Examples 1-52 of the present invention have better discharge specific capacity and rate properties than those of Comparative Examples 1-5.

[0184] Wherein: Example 2-10 uses different sodium sources, iron sources, sulfur sources and Na, Fe, S molar ratios to obtain Na x Fe y Mn z (SO4)3 positive electrode material, Examples 54-62 are sodium ion batteries assembled using the positive electrodes obtained in Examples 2-10, and it is found that the ultra-small particles of Na obtained by reacting different sodium sources, iron sources, and sulfur sources are x Fe y Mn z (SO4)3 cathode materials have little impact on the battery's electrochemical performance because different sodium, iron, and sulfur sources only provide sodium, iron, and sulfate ions; the remaining ions do not participate in the reaction. However, the Na:Fe:S molar ratio does have a certain impact on the product. When the sodium source ratio is too high or too low, the conversion rate and purity of the product decrease, leading to reduced battery cycling performance.

[0185] Examples 11-19: Na2Fe obtained by reacting different transition metal sources y M z (SO4)3 positive electrode material, Examples 63-71 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 11-19, and it is found that the ultra-small particles of Na2Fe y M z The (SO4)3 cathode material has a certain impact on the electrochemical performance of the battery. The capacity performance of products generated by Fe and Ni as transition metal ions is better than that of Co and Zn ions. This may be due to the different reactivity of the different ions and the different chemical and coordination environments in the products, resulting in different electrochemical properties of the products. Different salt solutions of the same type of transition metal ion have little effect on the electrochemical performance of the products because the salt solution only provides the transition metal ions required for the reaction, and the remaining ions do not participate in the reaction.

[0186] Examples 20-21 are Na2Fe obtained by reacting different molar ratios of sodium source, iron source, transition metal source and sulfur source. y Mn z (SO4)3 positive electrode material, Examples 72-73 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 20-21, and it is found that the ultra-small particles of Na2Fe y Mn z(SO4)3 cathode materials have a certain impact on the electrochemical performance of batteries. When the proportion of transition metal ions is too high or too low, the battery's cycling performance decreases. This is because excessively high or low proportions of transition metal ions will affect the active energy storage sites of the product.

[0187] Example 22 presents Na2FeMn(SO4)3 cathode materials obtained by reactions using different solvents. Example 74 presents a sodium-ion battery assembled using the cathode material obtained in Example 13. It was found that the ultra-small particles of Na2FeMn(SO4)3 cathode materials obtained by reactions using different solvents had a certain impact on the electrochemical performance of the battery. Using ethanol as the solvent resulted in a sharp decline in the electrochemical performance of the product. This is due to the low solubility of the reactants in ethanol, resulting in low product purity and conversion rate, which affected product performance.

[0188] Examples 23-26 are Na2FeMn(SO4)3 positive electrode materials obtained by reactions at different hydrothermal temperatures, and Examples 75-78 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 23-26. It was found that the ultra-small particles of Na2FeMn(SO4)3 positive electrode materials obtained by reactions at different hydrothermal temperatures had a certain effect on the electrochemical performance of the battery. When the hydrothermal temperature was too low at 40-80°C or too high at 220°C, the cycle performance of the battery decreased. When the hydrothermal temperature was between 100-160°C, the electrochemical performance of the product was not much different. The reason is that when the temperature is between 100-160°C, the growth environment provided has met the growth requirements of the product. Excessively high or low hydrothermal temperatures can easily damage the crystal form of the product.

[0189] Examples 27-30 are Na2FeMn(SO4)3 cathode materials obtained by different hydrothermal reaction times. Examples 79-82 are sodium ion batteries assembled using the cathode materials obtained in Examples 27-30. It was found that the ultra-small particles of Na2FeMn(SO4)3 cathode materials obtained by different hydrothermal reaction times had a certain impact on the electrochemical performance of the battery. When the reaction time was too low, at 2 hours, the cycle performance of the battery decreased. When the reaction time was between 6 and 12 hours, the electrochemical performance of the battery did not differ much. This is because when the reaction time is insufficient, the reaction does not proceed sufficiently.

[0190] Examples 31-32 are Na2FeMn(SO4)3 positive electrode materials obtained by drying imported materials with different moisture contents, and Examples 83-84 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 31-32. It was found that the ultra-small particle Na2FeMn(SO4)3 positive electrode materials obtained by drying imported materials with different moisture contents have little effect on the electrochemical performance of the battery.

[0191] Examples 33-34 are Na2FeMn(SO4)3 positive electrode materials obtained by drying with different drying chamber volumes, and Examples 85-86 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 33-34. It was found that the ultra-small particles of Na2FeMn(SO4)3 positive electrode materials obtained by drying with different drying chamber volumes have little effect on the electrochemical performance of the battery.

[0192] Examples 35-37 are Na2FeMn(SO4)3 positive electrode materials obtained by drying at different drying chamber temperatures, and Examples 87-89 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 35-37. It was found that the ultra-small particle Na2FeMn(SO4)3 positive electrode materials obtained by drying at different drying chamber temperatures have little effect on the electrochemical performance of the battery.

[0193] Examples 38-39 are Na2FeMn(SO4)3 positive electrode materials obtained by drying for different drying times, and Examples 90-91 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 38-39. It was found that the ultra-small particles of Na2FeMn(SO4)3 positive electrode materials obtained by drying for different drying times have little effect on the electrochemical performance of the battery.

[0194] Examples 40-41 are Na2FeMn(SO4)3 positive electrode materials obtained by drying at different gas flow rates in a drying chamber, and Examples 92-93 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 40-41. It was found that the ultra-small particles of Na2FeMn(SO4)3 positive electrode materials obtained by drying at different gas flow rates have little effect on the electrochemical performance of the battery.

[0195] Examples 42-44 are Na2FeMn(SO4)3 cathode materials obtained by reactions at different calcination temperatures. Examples 94-96 are sodium-ion batteries assembled using the cathode materials obtained in Examples 42-44. It was found that the ultra-small particles of Na2FeMn(SO4)3 cathode materials obtained by reactions at different calcination temperatures had a certain impact on the electrochemical performance of the batteries, with lower calcination temperatures resulting in decreased electrochemical performance. This is due to the lower annealing temperature, resulting in a lower degree of crystallization and an unstable material structure.

[0196] Examples 45-47 are Na2FeMn(SO4)3 positive electrode materials obtained by reactions at different heating rates, and Examples 97-99 are sodium ion batteries assembled using the positive electrode materials obtained by Examples 45-47. It was found that the ultra-small particle Na2FeMn(SO4)3 positive electrode materials obtained by reactions at different heating rates have little effect on the electrochemical performance of the battery.

[0197] Examples 48-50 are Na2FeMn(SO4)3 cathode materials obtained by reaction using different calcination treatment times. Examples 100-102 are sodium ion batteries assembled using the cathode materials obtained in Examples 48-50. It was found that the ultra-small particles of Na2FeMn(SO4)3 cathode materials obtained by reaction using different calcination treatment times had a certain impact on the electrochemical performance of the battery. The electrochemical performance of the product with a shorter calcination time decreased. This is because the shorter annealing time resulted in a lower degree of crystallization of the product and an unstable structure.

[0198] Examples 51-52 are Na2FeMn(SO4)3 positive electrode materials obtained by reacting in different calcination gas atmospheres, and Examples 103-104 are sodium ion batteries assembled using the positive electrode materials obtained in Examples 51-52. It was found that the ultra-small particle Na2FeMn(SO4)3 positive electrode materials obtained by reacting in different calcination gas atmospheres have little effect on the electrochemical performance of the battery.

[0199] Comparative Example 1 is a Na2FeMn(SO4)3 positive sodium ion battery positive electrode material prepared by ball milling and calcination. As can be seen from Figure 2, its particles are large and easily agglomerated, and the material utilization rate is low, resulting in a low discharge specific capacity and a low capacity retention rate after 500 cycles.

[0200] Comparative Example 2 is a Na2Fe2(SO4)3 positive electrode material without transition metal substitution. It can be seen that its first-cycle coulombic efficiency is low, and its capacity and cycle performance are poor. The reason may be that the reaction activity is reduced due to the loss of transition metal substitution.

[0201] Comparative Example 3 is a Na2Fe2(SO4)3 positive electrode material prepared by the solvent evaporation method. It can be seen that its capacity and cycle performance are poor. The reason may be that the grains agglomerate during the reaction to form secondary particles, and there is no transition metal to replace them, resulting in a decrease in the reaction activity of the product.

[0202] Comparative Example 4 is a Na2FeMn(SO4)3 positive electrode material prepared by the solvent evaporation method. It can be seen that its cycle performance is poor. The reason may be that the electrode material agglomerates during the reaction to form secondary particles.

[0203] Comparative Example 5 is a Na2FeNi(SO4)3 positive electrode material prepared by the solvent evaporation method. It can be seen that its cycle performance is poor. The reason may be that the electrode material agglomerates during the reaction to form secondary particles.

[0204] Figure 3 is a comparison of the cycle performance of the sodium ferric sulfate-based positive electrode materials prepared by different methods in Example 1 and Comparative Examples 1-2. As can be seen from Figure 3, the ultra-small particle Na2FeMn(SO4)3 lossless fast-charging positive electrode material prepared in Example 1 has stable cycle performance and a high capacity retention rate. The sodium ferric sulfate-based positive electrode material prepared in Comparative Examples 1-2 has poor cycle performance and a low capacity retention rate.

[0205] Figure 4 is a comparison of the rate performance of the sodium ferric sulfate-based positive electrode materials prepared in Example 1 and Comparative Examples 1-2. As can be seen from Figure 4, the ultra-small particle Na2FeMn(SO4)3 lossless fast-charging positive electrode material prepared in Example 1 has good cycle performance and high capacity retention at different current densities, showing good rate properties. The sodium ferric sulfate-based positive electrode material prepared in Comparative Examples 1-2 has poor rate performance and low capacity retention.

[0206] For those skilled in the art to which the present invention belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present invention, without having to resort to creative work. Therefore, based on the disclosure of the present invention, simple improvements made by those skilled in the art to the present invention should be within the scope of protection of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should fall within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that: The molecular formula of the positive electrode material is Na x Fe y M z (SO4)3, wherein 1.0≤x≤3.0, 0.5≤y≤2.0, 0.5≤z≤1.5, and M is a transition metal; the particle size of the positive electrode material is between 10-80nm.

2. The positive electrode material according to claim 1, characterized in that The transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ag, Pt, Au, and Hg.

3. A method for preparing a positive electrode material, characterized in that: The method for preparing the positive electrode material according to claim 1 or 2 comprises the following steps: (1) dispersing a sodium source, an iron source, a transition metal source and a sulfur source in a solvent to obtain a suspension; (2) heating the suspension to perform a solvothermal reaction; after cooling, separating, washing and flash drying the product of the solvothermal reaction in sequence to obtain a Na-based x Fe y M z Powder particles of (SO4)3; (3) calcining the powder particles under an inert gas atmosphere to obtain the positive electrode material.

4. The method for preparing the positive electrode material according to claim 3, characterized in that: The sodium source is selected from at least one of sodium sulfate, sodium bisulfate, sodium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, sodium phosphate, sodium nitrate, sodium phosphite, sodium formate, sodium propionate, sodium acrylate, sodium benzoate, sodium hypochlorite, sodium chlorate, sodium thiosulfate, sodium persulfate, sodium silicate, sodium bromate, sodium bromide, sodium iodide, sodium fluoride, sodium bisulfite, sodium nitrite, sodium oxalate, sodium persulfate, sodium hydroxide, sodium pyrosulfate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrosulfite, sodium pyrophosphate, sodium hydrogen phthalate, sodium hydrogen oxalate, sodium sulfite, sodium sorbate, trisodium phosphate, sodium gluconate, sodium oleate and hydrates of the above substances; And / or, the iron source is selected from at least one of ferric sulfate, ferrous oxide, ferric chloride, ferric nitrate, ferric acetate, ferrous acetate, ferrous bromide, ferrous nitrate, ferrous phosphate, ferrous iodide, ferrous acetate, ferrous metasilicate, ferrous metatitanate, disodium ferric sulfate, ferrous ammonium sulfate, ferrous carbonate, ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous oxide, ferrous dioxide, ferric chloride, ferric hydroxide and hydrates of the above substances; and / or, the transition metal source is at least one selected from soluble salts of scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, zinc, silver, platinum, gold, mercury and hydrates thereof; And / or, the sulfur source is selected from at least one of ferric sulfate, ferrous sulfate, sodium bisulfate, potassium sulfate, ferrous dithionite, ferrous thiosulfate, ferrous dithionate, ferrous tetrasulfide, sodium sulfate, sodium sulfite, sodium dithionite, sodium thiosulfate, sodium dithionite, sulfurous acid, sulfuric acid, ammonium persulfate, potassium persulfate, sodium persulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and hydrates of the above substances.

5. The method for preparing the positive electrode material according to claim 3 or 4, characterized in that: The molar ratio of the sodium source, the iron source, the transition metal source and the sulfur source is (1-3): (0.5-2): (0.5-1.5):

3.

6. The method for preparing the positive electrode material according to claim 3, characterized in that: The solvent is selected from at least one of water, methanol, ethanol, acetone, ethylene glycol and pyridine.

7. The method for preparing the positive electrode material according to claim 3, characterized in that: In step (2), the temperature of the solvent thermal reaction is 40-220° C.; and / or the time of the solvent thermal reaction is 4-12 h.

8. The method for preparing the positive electrode material according to claim 3, characterized in that: In step (2), the flash drying temperature is 120-350° C.; and / or the flash drying time is 0.2-6 h.

9. The method for preparing the positive electrode material according to claim 3, characterized in that: In step (3), the calcination temperature is 200-400°C; and / or the calcination time is 2-48h.

10. The method for preparing the positive electrode material according to claim 3, characterized in that: In step (3), the inert gas is at least one of nitrogen, argon, or a mixed gas of argon and hydrogen.

11. A positive electrode plate for a sodium ion battery, characterized in that: It comprises a current collector and a positive electrode material layer coated on the surface of the current collector; the positive electrode material layer contains a positive electrode active material, and the positive electrode active material is the positive electrode material according to claim 1 or 2.

12. A sodium ion battery, characterized in that: Including the sodium ion battery positive electrode plate as described in claim 11.

13. Use of the sodium ion battery according to claim 12 in mobile electronic communication equipment, electric vehicles, electric bicycles, energy storage batteries, power batteries or energy storage power stations.

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