A cathode material, its preparation method, and a sodium-ion battery

Abstract

This invention relates to the field of sodium-ion battery technology, and discloses a cathode material, its preparation method, and a sodium-ion battery. The cathode material contains Na₄Fe₂O₃. x A complex of (PO4)2P2O7 and C, 2.5 < x ≤ 3.05; wherein the particle size Dv50 of the cathode material is ≤ 7 μm; based on the amount of total Fe in the cathode material, Fe 3+ The content of Fe is not higher than 5%; the residual alkali content in the cathode material is not higher than 6 wt%. The cathode material of this invention has a small particle size, and in the cathode material, Fe... 3+ The content of alkali is not higher than 5% of the total Fe content, and the residual alkali content is not higher than 6 wt%. Under the above physical property parameters, the cathode material can still have excellent electrochemical performance in industrial production, which is conducive to the promotion and large-scale application of the material.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a cathode material, its preparation method, and a sodium-ion battery. Background Technology

[0002] Sodium-ion batteries, with their advantages of low cost, rapid charging and discharging, and excellent low-temperature performance, have gradually attracted widespread attention from the scientific and industrial communities. Compared with Prussian blue and layered oxide materials, polyanionic materials, especially cathode materials represented by Na4Fe3(PO4)2P2O7, have outstanding performance in terms of cost and lifespan, and have the prospect of large-scale application.

[0003] However, in the mass production of Na4Fe3(PO4)2P2O7, the use of conventional gas-jet crushing processes often leads to deterioration of material properties, resulting in poor electrochemical performance and thus limiting its applications. Furthermore, currently available high-performance Na4Fe3(PO4)2P2O7 samples are all small-batch laboratory-scale samples, with no experience accumulated for large-scale production. Ensuring good electrochemical performance during large-scale production remains a challenge, and the optimal physical parameters for mass-produced Na4Fe3(PO4)2P2O7 materials are still unclear.

[0004] In summary, how to synthesize Na4Fe3(PO4)2P2O7 with excellent electrochemical performance on a large scale is one of the key research directions in the field of cathode materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of large-scale production of Na4Fe3(PO4)2P2O7 in the existing technology, and to provide a cathode material, its preparation method and sodium-ion battery.

[0006] To achieve the above objectives, the present invention provides a cathode material containing Na₄Fe₂O₃. x A complex of (PO4)2P2O7 and C, 2.5 < x ≤ 3.05;

[0007] Wherein, the particle size Dv50 of the positive electrode material is ≤7μm;

[0008] Based on the total amount of Fe in the cathode material, Fe 3+ The content of [specific ingredient] is not higher than 5%;

[0009] The residual alkali content in the cathode material is no higher than 6 wt%.

[0010] Preferably, the residual alkali content in the cathode material is less than 4 wt%.

[0011] Preferably, the water content in the positive electrode material is less than 2000 ppm by weight.

[0012] Preferably, the particle size Dv50 of the positive electrode material is less than 4 μm.

[0013] Preferably, the specific surface area of ​​the positive electrode material is 0.1–25 m². 2 / g.

[0014] Preferably, the carbon content in the cathode material is 1-3 wt%.

[0015] Preferably, the compaction density of the positive electrode material at 600 MPa is 1.5–2.5 g / cm³. 3 .

[0016] Preferably, the magnetic induction intensity of the positive electrode material is <1000ppm.

[0017] Preferably, the resistivity of the positive electrode material is 0.1–4 kΩ·m at a pressure of 600 MPa.

[0018] A second aspect of the present invention provides a method for preparing a cathode material, the method comprising:

[0019] The cathode material raw material was subjected to air abrasion to obtain cathode material with a particle size Dv50 ≤ 7 μm.

[0020] The working medium for gas pulverization is a non-oxidizing gas;

[0021] The purity of the non-oxidizing gas is above 90%;

[0022] The non-oxidizing gas contains less than 5% O2 by volume.

[0023] Preferably, the non-oxidizing gas is selected from one or more of nitrogen, argon, helium, carbon dioxide, carbon monoxide, hydrogen, and ammonia.

[0024] Preferably, the purity of the non-oxidizing gas is 99% or higher.

[0025] Preferably, the H2O content in the non-oxidizing gas is less than 1000 ppm by volume.

[0026] Preferably, the non-oxidizing gas contains less than 100 ppm of H2O and less than 0.5 ppm of O2.

[0027] Preferably, the conditions for air pulverization include: a pressure of 0.2–1.0 MPa and an air flow rate of 1–10 m³ / s. 3 The feed rate is 10-90 kg / h.

[0028] Preferably, the air pulverization is carried out in an air pulverizer, wherein the air pulverizer includes any one of a horizontal disc air pulverizer, a circulating tube air pulverizer, a counter-jet air pulverizer, a target air pulverizer, and a fluidized bed air pulverizer.

[0029] A third aspect of the present invention provides a cathode material prepared by the method described above.

[0030] A fourth aspect of the present invention provides a sodium-ion battery, the sodium-ion battery comprising the positive electrode material as described above.

[0031] Through the above technical solution, the present invention has the following advantages:

[0032] (1) The cathode material of the present invention has a small particle size, and in the cathode material, Fe 3+ The content of alkali is not higher than 5% of the total Fe content, and the residual alkali content is not higher than 6 wt%. Under the above physical property parameters, the cathode material can still have excellent electrochemical performance in industrial production, which is conducive to the promotion and large-scale application of the material.

[0033] (2) The method for preparing the cathode material of the present invention overcomes the oxidation of the cathode material raw material (Fe) during the gas crushing process by using a non-oxidizing gas as the working medium. 3+ The problem of sodium precipitation (residual alkali) affects the residual alkali content and Fe content. 3+ The content did not change significantly before and after gas pulverization, and the capacity of the material was maintained. Therefore, the cathode material prepared by this method has excellent electrochemical performance, and the large-scale preparation of Na4Fe3(PO4)2P2O7 has been achieved. Attached Figure Description

[0034] Figure 1 These are XRD patterns of the cathode material raw materials used in the embodiments and comparative examples of this invention;

[0035] Figure 2 This is the XRD pattern of the cathode material obtained after gas crushing in Comparative Example 1 of this invention;

[0036] Figure 3 This is the XRD pattern of the cathode material obtained after gas crushing in Comparative Example 2 of this invention;

[0037] Figure 4 This is the XRD pattern of the positive electrode material obtained after gas crushing in Embodiment 1 of the present invention;

[0038] Figure 5 This is the XRD pattern of the positive electrode material obtained after gas crushing in Embodiment 2 of the present invention;

[0039] Figure 6 This is a charge-discharge curve of the positive electrode material obtained after gas crushing in Comparative Example 1 of the present invention at 0.1C;

[0040] Figure 7 This is a charge-discharge curve of the positive electrode material obtained after gas crushing in Comparative Example 2 of the present invention at 0.1C;

[0041] Figure 8 This is a charge-discharge curve of the positive electrode material obtained after gas crushing in Embodiment 1 of the present invention at 0.1C;

[0042] Figure 9 This is a charge-discharge curve of the positive electrode material obtained after gas crushing in Embodiment 2 of the present invention at 0.1C. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] This invention provides a cathode material containing Na₄Fe₂O₃. x A complex of (PO4)2P2O7 and C, 2.5 < x ≤ 3.05; wherein the particle size Dv50 of the cathode material is ≤ 7 μm; based on the amount of total Fe in the cathode material, Fe 3+ The content of alkali is not higher than 5%; the residual alkali content in the cathode material is not higher than 6 wt%.

[0046] Currently, the performance of cathode materials prepared on a large scale is unstable. However, this invention clarifies the physical property parameters of the cathode material, thereby enabling the cathode material to have excellent electrochemical performance. This ensures that the cathode material still has excellent electrochemical performance in industrial production, which is conducive to the promotion and large-scale application of the material.

[0047] If the particle size of the cathode material is too large, it will not only affect the cell manufacturing process (e.g., slurry viscosity, coating uniformity, etc.) but also the electrochemical performance (e.g., capacity utilization, rate performance, etc.). In this invention, the particle size Dv50 of the cathode material is ≤7μm. Within this particle size range, the cathode material is easy to coat and exhibits good electrochemical performance. In this invention, Dv50≤7μm refers to the particle size of 50% of the particles in the cathode material being ≤7μm. Preferably, a laser particle size analyzer is used to measure the particle size.

[0048] In this invention, the amount of total Fe in the positive electrode material is used as a basis, Fe 3+ The content of Fe is no higher than 5%, thus increasing the capacity of the cathode material. The total amount of Fe refers to the sum of the amounts of Fe elements in the cathode material. Preferably, Fe... 3+ Content determination is performed using chromatography or titration.

[0049] To improve the capacity and rate performance of the cathode material, in a preferred embodiment, the residual alkali content in the cathode material is less than 4 wt%. Preferably, the residual alkali is calibrated using an alcohol titration method or an aqueous solution titration method.

[0050] In a preferred embodiment, Na4Fe x In (PO4)2P2O7, 2.9 ≤ x ≤ 3.05, therefore,

[0051] In a preferred embodiment, the water content in the cathode material is less than 2000 ppm by weight, and at this water content, the specific capacity of the cathode material is higher.

[0052] In order to improve the coating performance and electrochemical performance of the cathode material, in a preferred embodiment, the particle size Dv50 of the cathode material is <4μm.

[0053] This invention does not impose a particular limitation on the specific surface area of ​​the cathode material; the specific surface area of ​​the cathode material can be determined as needed. In a specific embodiment, the specific surface area of ​​the cathode material is 0.1–25 m². 2 / g, specifically, for example, can be 0.1m 2 / g, 1m 2 / g、2m 2 / g、5m 2 / g, 10m 2 / g, 15m 2 / g or 25m 2 / g.

[0054] In a preferred embodiment, the carbon content in the cathode material is 1 to 3 wt%, and at this carbon content, the cathode material exhibits good conductivity and energy density.

[0055] To improve the electrochemical performance of the cathode material, in a preferred embodiment, the compaction density of the cathode material at 600 MPa is 1.5–2.5 g / cm³. 3 .

[0056] In a specific embodiment, the number of metal particles larger than 200 μm in the positive electrode material is less than 200 pcs / kg. Thus, the positive electrode material is easy to prepare, and the battery made from the positive electrode material has a long service life.

[0057] In a preferred embodiment, the magnetic induction intensity of the positive electrode material is <1000ppm. There is a certain relationship between the magnetic induction intensity and the number of magnetic particles. Within this range of magnetic induction intensity, the metal content in the positive electrode material is lower, thereby making the battery made from the positive electrode material have a longer lifespan.

[0058] To further improve the capacity and rate performance of the cathode material, in a preferred embodiment, the resistivity of the cathode material is 0.1 to 4 kΩ·m at a pressure of 600 MPa.

[0059] The present invention also provides a method for preparing the cathode material, the method comprising:

[0060] The cathode material raw material was subjected to air abrasion to obtain cathode material with a particle size Dv50 ≤ 7 μm.

[0061] The working medium for gas pulverization is a non-oxidizing gas;

[0062] The purity of the non-oxidizing gas is above 90%, where purity represents the volume percentage of the effective components in the non-oxidizing gas.

[0063] The non-oxidizing gas contains less than 5% O2 by volume.

[0064] The method for preparing the cathode material of the present invention reduces the oxidation (Fe2+) of the cathode material raw materials during the gas chromatography process by using a non-oxidizing gas as the working medium. 3+ Sodium precipitation (residual alkali) may occur, which may affect the residual alkali content and Fe content. 3+ The content did not change significantly before and after gas pulverization, and the capacity of the material was maintained. Therefore, the cathode material prepared by this method has excellent electrochemical performance, and the large-scale preparation of Na4Fe3(PO4)2P2O7 has been achieved.

[0065] In the method described in this invention, before and after gas crushing, Na4Fe x The contents of the impurity phases NaFePO4 and Na2FeP2O7 in (PO4)2P2O7 remain essentially unchanged. The specific judgment method is as follows: For the cathode material obtained after gas fragmentation, after subtracting the background, the strongest diffraction peak intensity in the XRD diffraction curve near 10.8±0.5 degrees should not exceed 10% of the strongest peak intensity near 33.7±0.5 degrees; the strongest diffraction peak intensity near 33.0±0.4 degrees should not exceed 10% of the strongest peak intensity near 33.6±0.5 degrees.

[0066] In the method described in this invention, preferably, Na4Fe x In (PO4)2P2O7, 2.9 ≤ x ≤ 3.05.

[0067] The present invention does not limit the specific source of the cathode material raw materials before gas pulverization; they can be purchased or prepared by conventional methods in the art. In one specific embodiment, the cathode material raw materials are prepared according to the following steps: mixing an iron source, a sodium source, a phosphorus source, and a carbon source, followed by granulation and calcination. Preferably, the granulation is performed using spray drying, and the calcination is performed using a high-temperature solid-state method.

[0068] The present invention does not impose any particular limitation on the specific types of iron, sodium, phosphorus, and carbon sources used in the preparation of cathode materials, and the selections can be conventional in the art. Specifically, the iron source can be, for example, one or more of ferric nitrate, ferric sulfate, ferric oxide, ferric oxide, ferric phosphate, and ferrous sulfate; the sodium source can be, for example, one or more of sodium citrate, sodium acetate, sodium oxalate, trisodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate, sodium carbonate, and sodium bicarbonate; the phosphorus source can be, for example, one or more of sodium pyrophosphate, sodium phosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, and monosodium trihydrogen pyrophosphate; and the phosphorus source can be, for example, one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, and disodium hydrogen phosphate.

[0069] In a specific implementation, spray drying is used for granulation when preparing the cathode material raw materials.

[0070] In a specific implementation, the calcination conditions for preparing the cathode material raw material include: a temperature of 450–600°C, a time of 1–12 h, and a gas atmosphere of argon or nitrogen.

[0071] In a preferred embodiment, the purity of the non-oxidizing gas is above 99%, thus resulting in better electrochemical performance of the prepared cathode material.

[0072] The present invention does not limit the specific type of the non-oxidizing gas, and it can be any non-oxidizing gas conventional in the art. In a specific embodiment, the non-oxidizing gas is selected from one or more of nitrogen, argon, helium, carbon dioxide, carbon monoxide, hydrogen, and ammonia.

[0073] In a preferred embodiment, the H2O content in the non-oxidizing gas is less than 1000 ppm by volume. This better protects the original phases in the cathode material raw materials, reducing water content, residual alkali content, and Fe content. 3+ The content did not change significantly before and after air crushing.

[0074] More preferably, the content of H2O in the non-oxidizing gas is less than 100 ppm by volume, and the content of O2 is less than 0.5% by volume, thus the electrochemical performance of the obtained cathode material is better.

[0075] This invention does not limit the specific conditions for gas aeration and can be designed according to actual needs. In a specific embodiment, the conditions for gas aeration include: pressure of 0.2–1.0 MPa and air flow rate of 1–10 m³ / s. 3 The feed rate is 10–90 kg / h. Preferably, the conditions for air pulverization include: pressure of 0.7–0.9 MPa and air flow rate of 3–6 m³ / min. 3 The feed rate is 15–60 kg / h.

[0076] In the method described in this invention, the pressure during gas aeration is provided by a non-oxidizing gas. Specifically, the non-oxidizing gas is provided by a bottled high-pressure gas source or a high-pressure gas source generated by a gas generator.

[0077] In the method described in this invention, air pulverization is carried out in an air pulverizer. This invention does not limit the specific type of air pulverizer; it can be any air pulverizer commonly used in the art. In specific embodiments, the air pulverizer includes any one of a horizontal disc air pulverizer, a circulating tube air pulverizer, a counter-jet air pulverizer, a target air pulverizer, and a fluidized bed air pulverizer.

[0078] The present invention also provides a cathode material prepared by the method described above, which still exhibits excellent electrochemical performance in industrial production, thus facilitating the promotion and large-scale application of the material.

[0079] The present invention also provides a sodium-ion battery, wherein the sodium-ion battery comprises the positive electrode material as described above.

[0080] This invention does not limit the specific raw materials and preparation methods of the sodium-ion battery, and can use conventional raw materials and preparation methods in the art. In one specific embodiment, the sodium-ion battery is prepared according to the following steps: mixing a positive electrode material, a conductive additive, a binder, and NMP; coating the resulting mixture onto an aluminum current collector and then drying it to obtain a positive electrode sheet; assembling the positive electrode sheet, a glass fiber separator, metallic sodium, and NaPF6-EC / DMC electrolyte to obtain a sodium-ion battery.

[0081] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0082] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0083] Preparation Example

[0084] Cathode material raw material preparation process:

[0085] S1: Weigh out sodium carbonate (sodium source), ammonium dihydrogen phosphate (phosphorus source), ferric oxide (iron source) and glucose (carbon source) in a molar ratio of 4:8:3:2;

[0086] S2: Mix the raw materials weighed in step S1 evenly, and grind the particles of the mixture into fine particles using a sand mill. The solid content of the slurry is 50%, the solvent is pure water, the sand mill speed is 1000 r / min, and the grinding time is 6 h to obtain the slurry.

[0087] S3: Spray dry the slurry obtained in step S2. The inlet temperature of the spray dryer is 180°C and the outlet temperature is 250°C to obtain the precursor.

[0088] S4: The precursor obtained in step S3 is placed in a box furnace for calcination at a temperature of 540℃ for 12 hours. The calcination process is protected by N2.

[0089] S5: After natural cooling, collect the calcination product to obtain the cathode material raw material (a complex of Na4Fe3(PO4)2P2O7 and C).

[0090] Example 1

[0091] The cathode material raw material is fed into a fluidized bed air jet mill for gas pulverization. During the gas pulverization process, a non-oxidizing gas is used as the working medium to obtain the cathode material. The non-oxidizing gas is nitrogen (N2), with a purity >99% (i.e., N2 content >99%), and a water content below 100 ppm by volume and an oxygen content below 0.5% by volume. The gas flow rate used in operation is 3 m³ / s. 3 The working pressure is set to 0.8 MPa, and the feeding rate is 30 kg / h.

[0092] Example 2

[0093] The method described in Example 1 was implemented, except that the non-oxidizing gas was carbon dioxide (CO2), the purity of the non-oxidizing gas was >99%, and the water content in the non-oxidizing gas was less than 100 ppm by volume, and the oxygen content was less than 0.5 ppm by volume.

[0094] Example 3

[0095] The method described in Example 1 was implemented, except that the feed rate was 60 kg / h.

[0096] Example 4

[0097] The method described in Example 2 was implemented, except that the feed rate was 60 kg / h.

[0098] Example 5

[0099] The method described in Example 1 was implemented, except that a ventilation rate of 6 m³ / s was used during the operation. 3 The working pressure is set to 0.9 MPa, and the feed rate is 30 kg / h.

[0100] Example 6

[0101] The method described in Example 5 was implemented, except that the non-oxidizing gas was argon (Ar), the purity of the non-oxidizing gas was >99%, and the water content in the non-oxidizing gas was less than 100 ppm by volume, and the oxygen content was less than 0.5 ppm by volume.

[0102] Example 7

[0103] The method described in Example 5 was implemented, except that the feed rate was 60 kg / h.

[0104] Example 8

[0105] The method described in Example 5 was implemented, except that the feed rate was 15 kg / h.

[0106] Example 9

[0107] The method described in Example 1 is implemented, except that the working pressure is set to 0.7 MPa.

[0108] Example 10

[0109] The method described in Example 9 was implemented, except that the ventilation rate used in the operation was 6m³. 3 / min.

[0110] Example 11

[0111] The cathode material raw material is fed into a fluidized bed jet mill for gas pulverization. A non-oxidizing gas is used as the working medium during the gas pulverization process to obtain the cathode material. The non-oxidizing gas is nitrogen (N2) with a purity of 96.4%, containing 900 ppm water and 3.5% oxygen by volume. The gas flow rate used in the operation is 3 m³ / s. 3 The working pressure is set to 0.8 MPa, and the feeding rate is 30 kg / h.

[0112] Example 12

[0113] The cathode material raw material is fed into a fluidized bed air jet mill for gas pulverization. During the gas pulverization process, a non-oxidizing gas is used as the working medium to obtain the cathode material. The non-oxidizing gas is nitrogen (N2), with a purity >99% (i.e., N2 content >99%), and a water content below 100 ppm by volume and an oxygen content below 0.5% by volume. The gas flow rate used in operation is 3 m³ / s. 3 The working pressure is set to 0.8 MPa, and the feed rate is 90 kg / h.

[0114] Example 13

[0115] The cathode material raw material is fed into a fluidized bed air jet mill for gas pulverization. During the gas pulverization process, a non-oxidizing gas is used as the working medium to obtain the cathode material. The non-oxidizing gas is nitrogen (N2), with a purity >99% (i.e., N2 content >99%), and a water content below 100 ppm by volume and an oxygen content below 0.5% by volume. The gas flow rate used in operation is 3 m³ / s. 3 The working pressure is set to 0.5 MPa, and the feeding rate is 30 kg / h.

[0116] Example 14

[0117] The cathode material raw material is fed into a fluidized bed jet mill for gas pulverization. During the gas pulverization process, a non-oxidizing gas is used as the working medium to obtain the cathode material. The non-oxidizing gas is nitrogen (N2), with a purity >99% (i.e., N2 content >99%), and a water content below 100 ppm by volume and an oxygen content below 0.5% by volume. The gas flow rate used in operation is 1.5 m³ / s. 3 The working pressure is set to 0.8 MPa, and the feeding rate is 30 kg / h.

[0118] Comparative Example 1

[0119] The method described in Example 1 was implemented, except that the working medium was conventional compressed air, wherein the N2 content was 78.1% by volume, the O2 content was 21.2% by volume, and the water content was 0.05% by volume.

[0120] Comparative Example 2

[0121] The method described in Example 1 was implemented, except that the working medium was dry compressed air, wherein the N2 content was 78.1% by volume, the O2 content was 21.2% by volume, and the water content was <50% by volume ppm.

[0122] Test Example 1

[0123] X-ray diffraction (XRD) was performed on the cathode material raw materials before gas shock, and the cathode materials obtained after gas shock in Examples 1-2 and Comparative Examples 1-2. The results are as follows: Figure 1-5 As shown.

[0124] Depend on Figure 1 and Figure 2 It can be seen that in Comparative Example 1, the impurity content of the material increased slightly after gas pulverization. According to semi-quantitative calculation, the total impurity content increased to 7.2%.

[0125] Depend on Figure 1 and Figure 3 As can be seen from Comparative Example 2, according to semi-quantitative analysis, the impurity content of the target product did not increase significantly, i.e., <5%.

[0126] Depend on Figure 1 and Figure 4-5 It can be seen that in Examples 1 and 2, there is no significant change in the curves of the materials before and after gas pulverization, indicating that there is no significant increase in impurities during the gas pulverization process.

[0127] Test Example 2

[0128] Physical properties of the cathode material raw materials and the cathode materials obtained after gas crushing in the examples and comparative examples were tested, and the cathode material raw materials and cathode materials were assembled into batteries for electrochemical performance testing.

[0129] Battery preparation method: The positive electrode material, conductive additive Super P and binder PVDF are weighed in a mass ratio of 8:1:1, NMP solvent is added, and after being mixed evenly, the mixture is coated on an aluminum current collector, dried and cut into small discs for later use; the obtained positive electrode discs, glass fiber separator, metallic sodium and 1 mol / L NaPF6-EC / DMC electrolyte are used to assemble coin cells.

[0130] The physical performance testing methods are as follows:

[0131] Particle size Dv50 (μm): tested using a PSA laser particle size analyzer;

[0132] Fe 3+ Content (%): Fe 3+ Content was determined by titration.

[0133] Residual alkali content (wt%): Residual alkali was determined by alcohol titration.

[0134] Moisture content (ppm by weight): tested using the TGA thermogravimetric method;

[0135] Specific surface area (m²) 2 / g): Tested using a static adsorption BET ratio analyzer (N2 adsorption method);

[0136] Carbon content (wt%): determined using a sulfur / carbon analyzer;

[0137] Compacted density (g / cm³) 3 The powder is loaded into the mold and compacted using a hydraulic press at a pressure of 600 MPa.

[0138] Magnetic flux density (ppm): Tested using a magnetic material analyzer;

[0139] Resistivity (kΩ·m): The powder is loaded into the mold, compacted using a hydraulic press, and measured using a four-probe resistivity meter.

[0140] The physical performance data of the cathode material raw materials and the cathode materials in the examples and comparative examples are shown in Table 1 below. The data on gas pulverization conditions and the electrochemical performance data of the batteries are shown in Table 2 below. The charge-discharge curves of the batteries prepared from the cathode materials of Examples 1-2 and Comparative Examples 1-2 at 0.1C (1C = 129 mA / g) and 1C currents are shown below. Figure 6-9 As shown.

[0141] Table 1

[0142]

[0143]

[0144] Table 2

[0145]

[0146]

[0147] As can be seen from Tables 1 and 2, in Examples 1-14 of the present invention, the water content, residual alkali content, and Fe content are... 3+ The content did not change qualitatively before and after gas pulverization, and the capacity of the material was maintained. This indicates that in the gas pulverization process for large-scale preparation, using a non-oxidizing gas as the working medium can effectively protect the original phase, thereby producing a cathode material with excellent electrochemical performance.

[0148] Furthermore, as can be seen from Examples 1-14, by changing the air volume, working pressure, and feed rate, the particle size distribution characteristics of the material can be effectively controlled, thereby affecting parameters such as compaction density and specific surface area, and thus affecting the rate performance.

[0149] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that, The cathode material contains Na₄Fe₂ x A complex of (PO4)2P2O7 and C, 2.5 < x ≤ 3.05; Wherein, the particle size Dv50 of the positive electrode material is ≤7μm; Based on the total amount of Fe in the cathode material, Fe 3+ The content is not higher than 5%; The residual alkali content of the cathode material is no higher than 6 wt%; The positive electrode material is prepared according to the following process: The cathode material raw material was subjected to air abrasion to obtain cathode material with a particle size Dv50 ≤ 7 μm. The working medium for gas pulverization is a non-oxidizing gas; The purity of the non-oxidizing gas is above 90%; The non-oxidizing gas contains less than 5% O2 by volume.

2. The cathode material according to claim 1, characterized in that, The residual alkali content in the cathode material is less than 4 wt%.

3. The cathode material according to claim 1, characterized in that, The water content in the cathode material is less than 2000 ppm by weight.

4. The cathode material according to claim 1, characterized in that, The particle size Dv50 of the cathode material is <4μm.

5. The positive electrode material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode material is 0.1~25m². 2 / g.

6. The cathode material according to claim 1 or 5, characterized in that, The carbon content in the cathode material is 1~3wt%.

7. The cathode material according to claim 1 or 5, characterized in that, The compaction density of the cathode material at 600 MPa is 1.5~2.5 g / cm³. 3 .

8. The positive electrode material according to claim 1, characterized in that, The resistivity of the positive electrode material is 0.1~4kΩ·m at a pressure of 600MPa.

9. The positive electrode material according to claim 1, characterized in that, The non-oxidizing gas is selected from one or more of nitrogen, argon, helium, carbon dioxide, carbon monoxide, hydrogen, and ammonia.

10. The cathode material according to claim 1 or 9, characterized in that, The purity of the non-oxidizing gas is above 99%.

11. The cathode material according to claim 1 or 9, characterized in that, The H2O content in the non-oxidizing gas is less than 1000 ppm by volume.

12. The cathode material according to claim 1 or 9, characterized in that, The non-oxidizing gas contains less than 100 ppm of H2O by volume and less than 0.5 ppm of O2 by volume.

13. The cathode material according to claim 1, characterized in that, The conditions for gas catalysis include: pressure of 0.2~1.0 MPa and air flow rate of 1~10 m³ / s. 3 The feed rate is 10~90 kg / h.

14. The cathode material according to claim 1, characterized in that, The air pulverization is carried out in an air pulverizer, which includes any one of a horizontal disc air pulverizer, a circulating tube air pulverizer, a counter-jet air pulverizer, a target air pulverizer, and a fluidized bed air pulverizer.

15. A sodium-ion battery, characterized in that, The sodium-ion battery includes the positive electrode material as described in any one of claims 1-14.

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