High-compaction sodium-ion battery composite positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a high-compaction sodium ion battery composite positive electrode material as well as a preparation method and application thereof, and relates to the technical field of sodium battery positive electrode materials. The specific preparation method comprises the following steps: firstly, mixing carbonate and metal oxide, adding a solvent, stirring, and sanding to obtain turbid liquid; performing spray drying on the turbid liquid to obtain a dry powder precursor; and the dry powder precursor is subjected to heating and heat preservation to obtain the O3 type layered oxide. Adding the obtained O3 type layered oxide, an iron source, a sodium source, phosphoric acid and a carbon source into a solvent, sanding and mixing to obtain a turbid liquid; drying the turbid liquid to obtain a dry powder precursor; the dry powder precursor is subjected to temperature rise, heat preservation and air jet pulverization to obtain the high-compaction sodium ion battery composite positive electrode material. A positive plate prepared from the high-compaction sodium-ion battery composite positive electrode material prepared by the preparation method has high compaction density, and a prepared button battery has large reversible capacity and relatively good cycle retention rate, and has good application prospects in large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium battery cathode materials, and particularly relates to a high-compaction sodium-ion battery composite cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous growth of global energy demand and the enhancement of environmental protection awareness, sodium-ion batteries have shown great potential in the field of large-scale energy storage due to their rich resources, low cost, and working mechanism similar to that of lithium-ion batteries. However, the performance improvement of sodium-ion battery cathode materials is still a key factor restricting their development. Sodium iron pyrophosphate, as a kind of polyanionic compound, has received extensive attention due to its low cost, pollution-free, easy synthesis, and stable structure during charge and discharge processes. However, existing sodium iron pyrophosphate cathode materials have problems such as low tap density and small reversible capacity, which in turn limit the overall energy density of sodium-ion batteries.

[0003] In existing preparation technologies, the main method is to increase the tap density of sodium iron pyrophosphate cathode materials by reducing the particle size. For example, in patent CN117682490A, but the smaller particle size leads to a larger specific surface area, increasing the contact area between the material and the electrolyte, triggering more interfacial side reactions, and reducing the cycle stability and safety of the battery. In addition, in terms of electrochemical performance, although sodium iron pyrophosphate has a high theoretical capacity, in practical applications, due to factors such as material structure and conductivity, the actual reversible capacity is not fully utilized, and the rate performance also needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-compaction sodium-ion battery composite cathode material, a preparation method thereof, and an application thereof to solve the problems such as insufficient reversible capacity and rate performance of existing sodium iron pyrophosphate cathode materials.

[0005] To solve the above technical problems, the present invention specifically provides the following technical solutions: The present invention discloses a preparation method of a high-compaction sodium-ion battery composite cathode material, including: S1: Mix carbonate and metal oxide, add a solvent and stir, then perform sand milling to obtain a suspension; the suspension is spray-dried to obtain a dry powder precursor; in a nitrogen atmosphere, the dry powder precursor is further heated and held at a constant temperature to obtain an O3-type layered oxide; S2: Add the O3-type layered oxide, iron source, sodium source, phosphorus source, and carbon source to a solvent and sand mill and mix to obtain a suspension; the suspension is dried to obtain a dry powder precursor; in a nitrogen atmosphere, the dry powder precursor is heated, held at a constant temperature, and airflow pulverized to obtain a high-compaction sodium-ion battery composite cathode material; the mass ratio of the iron source to the O3-type layered oxide used is 1:1 - 2.

[0006] Preferably, the carbonate in S1 is sodium carbonate; the metal oxides are iron(III) oxide, manganese dioxide, nickel oxide, magnesium oxide, and aluminum oxide; the solvent is water, and the molar ratio of the usage amount of the carbonate to the solvent is 1:30 - 40.

[0007] More preferably, in S1, the molar ratio of the usage amount of sodium carbonate to iron(III) oxide is 1:0.2 - 0.6, the molar ratio of the usage amount of sodium carbonate to manganese dioxide is 1:0.4 - 0.8, the molar ratio of the usage amount of sodium carbonate to nickel oxide is 1:0.2 - 0.6, the molar ratio of the usage amount of sodium carbonate to magnesium oxide is 1:0.05 - 0.2, and the molar ratio of the usage amount of sodium carbonate to aluminum oxide is 1:0.05 - 0.2.

[0008] Preferably, the solvent in S1 is water, and the molar ratio of the usage amount of the carbonate to the solvent is 1:30 - 40.

[0009] Preferably, the iron source in S2 is at least one of ferrous oxalate, iron nitrate, ferrous acetate, iron phosphate, and iron nitrate; the solvent is ethanol, and the mass ratio of the usage amount of the iron source to the solvent is 1:8 - 11.

[0010] Preferably, the sodium source in S2 is at least one of sodium carbonate, sodium acetate, sodium oxalate, sodium pyrophosphate, sodium hydroxide, sodium chloride, and disodium hydrogen phosphate; the mass ratio of the usage amount of the iron source to the sodium source is 1:0.5 - 1.

[0011] Preferably, the phosphorus source in S2 is at least one of phosphoric acid, ammonium dihydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; the mass ratio of the usage amount of the iron source to the phosphorus source is 1:0.3 - 0.9.

[0012] Preferably, the carbon source in S2 is at least one of glucose, citric acid, sucrose, ascorbic acid, carbon nanotubes, reduced graphene oxide, oxalic acid, and oxalate compounds; the mass ratio of the usage amount of the iron source to the carbon source is 1:0.2 - 1.8; the oxalate compound is prepared from 5 - cyano - 2 - hydroxy - 3 - methoxybenzoic acid, 3 - diethylamino - 1 - propanol, and oxalyl chloride. Using the oxalate compound as the carbon source can improve the grading of the composite cathode material for high - compaction sodium - ion batteries and the full contact between active materials, thereby improving the electrochemical performance of the prepared battery.

[0013] Preferably, in S1, the stirring time is 0.3 - 1 h, the sanding speed is 2000 - 3000 rpm, the sanding time is 1 - 2 h, the temperature of spray drying is 180 - 220 °C, the feeding speed of spray drying is 250 mL / h, the heating rate of the dry - powder precursor is 3 - 6 °C / min, the heating temperature is 550 - 1000 °C, and the holding time is 15 - 20 h.

[0014] Preferably, in S2, the sanding and mixing time is 10 - 15 h, the drying temperature is 90 - 110 °C, the drying air flow rate is 2 - 5 m / s, the heating rate of the dry powder precursor is 1 - 3 °C / min, the heating temperature is 250 - 600 °C, and the heat preservation time is 15 - 20 h.

[0015] The present invention discloses a battery, comprising the high - compact sodium - ion battery composite cathode material prepared by the above - mentioned method.

[0016] The present invention discloses a preparation method of a high - compact sodium - ion battery composite cathode material, comprising: S1: Mix carbonate and metal oxide, add a solvent and stir for 0.3 - 1 h, then sand and grind at 2000 - 3000 rpm for 1 - 2 h to obtain a suspension; the suspension is spray - dried at 180 - 220 °C with a feed rate of 250 mL / h to obtain a dry powder precursor; in a nitrogen atmosphere, the dry powder precursor is further heated to 550 - 1000 °C at a heating rate of 3 - 6 °C / min and heat - preserved for 15 - 20 h to obtain an O3 - type layered oxide; S2: Add the O3 - type layered oxide, iron source, sodium source, phosphorus source and carbon source into a solvent, sand and grind for 10 - 15 h to obtain a suspension; the suspension is dried at 90 - 110 °C and an air flow rate of 2 - 5 m / s to obtain a dry powder precursor; in a nitrogen atmosphere, the dry powder precursor is further heated to 250 - 600 °C at a heating rate of 1 - 3 °C / min, heat - preserved for 15 - 20 h, and finally obtained the high - compact sodium - ion battery composite cathode material through air - flow comminution.

[0017] Preferably, the carbonate in S1 is sodium carbonate.

[0018] Preferably, the solvent in S1 is water, and the molar ratio of the usage amount of carbonate to the solvent is 1:30 - 40.

[0019] Preferably, the metal oxide in S1 is iron(III) oxide, manganese dioxide, nickel oxide, magnesium oxide and aluminum oxide.

[0020] More preferably, the molar ratio of the usage amount of sodium carbonate to iron(III) oxide is 1:0.2 - 0.6.

[0021] More preferably, the molar ratio of the usage amount of sodium carbonate to manganese dioxide is 1:0.4 - 0.8.

[0022] More preferably, the molar ratio of the usage amount of sodium carbonate to nickel oxide is 1:0.2 - 0.6.

[0023] More preferably, the molar ratio of the usage amount of sodium carbonate to magnesium oxide is 1:0.05 - 0.2.

[0024] More preferably, the molar ratio of the usage amounts of sodium carbonate and aluminum oxide is 1:0.05 - 0.2.

[0025] Preferably, in S1, the solvent is water, and the molar ratio of the usage amounts of the carbonate and the solvent is 1:30 - 40.

[0026] Preferably, in S2, the iron source is at least one of ferrous oxalate, iron nitrate, ferrous acetate, iron phosphate, and iron nitrate.

[0027] Preferably, in S2, the mass ratio of the usage amounts of the iron source and the O3-type layered oxide is 1:1 - 2.

[0028] Preferably, in S2, the sodium source is at least one of sodium carbonate, sodium acetate, sodium oxalate, sodium pyrophosphate, sodium hydroxide, sodium chloride, and disodium hydrogen phosphate; the mass ratio of the usage amounts of the iron source and the sodium source is 1:0.5 - 1.

[0029] Preferably, in S2, the phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; the mass ratio of the usage amounts of the iron source and the phosphorus source is 1:0.3 - 0.9.

[0030] Preferably, in S2, the carbon source is at least one of glucose, citric acid, sucrose, ascorbic acid, carbon nanotubes, reduced graphene oxide, oxalic acid, and oxalate compounds; the mass ratio of the usage amounts of the iron source and the carbon source is 1:0.2 - 1.8.

[0031] Preferably, in S2, the solvent is ethanol, and the mass ratio of the usage amounts of the iron source and the solvent is 1:8 - 11.

[0032] The present invention discloses a preparation method of an oxalate compound, specifically as follows: S1: Mix 5-cyano-2-hydroxy-3-methoxybenzoic acid with 3-diethylamino-1-propanol, then add concentrated sulfuric acid, and react at 110 - 135 °C for 6 - 15 h. After the reaction ends, adjust to pH 6.5 - 10, wash the oil layer, then rotary evaporate, crystallize, and dry to obtain an intermediate. S2: Under nitrogen conditions, add toluene, triethylamine, and oxalyl chloride solution to the intermediate, and react at 20 - 30 °C for 1 - 5 h. After the reaction ends, rotary evaporate, recrystallize, and finally dry to obtain the oxalate compound.

[0033] Preferably, in S1, the mass ratio of the usage amounts of 5-cyano-2-hydroxy-3-methoxybenzoic acid and 3-diethylamino-1-propanol is 1:2 - 4.

[0034] Preferably, in S1, the dosage ratio of 5-cyano-2-hydroxy-3-methoxybenzoic acid to concentrated sulfuric acid is 1 g:0.05 - 0.12 ml.

[0035] Preferably, in S1, the washing is carried out by washing with water and saturated sodium chloride solution in sequence. The saturated sodium chloride solution is composed of sodium chloride and water.

[0036] Preferably, the reagent used for recrystallization in S1 is n-hexane.

[0037] Preferably, the dosage ratio of the intermediate to toluene in S2 is 1 g: 0.3 - 0.6 ml.

[0038] Preferably, the mass ratio of the usage amount of the intermediate to triethylamine in S2 is 1: 0.25 - 0.5.

[0039] Preferably, the oxalyl chloride solution in S2 is composed of oxalyl chloride and toluene, and the dosage ratio of oxalyl chloride to toluene is 1 g: 1 - 2 ml.

[0040] Preferably, the mass ratio of the usage amount of the intermediate to the oxalyl chloride solution in S2 is 1: 0.5 - 1.

[0041] Preferably, the reagent used for recrystallization in S2 is dichloromethane.

[0042] More preferably, in the preparation of the high-compaction sodium-ion battery composite cathode material, on the basis of using the oxalate compound, mannitol monooleate can also be used. The oxalate compound and mannitol monooleate can be used in combination synergistically to further improve the particle grading of the high-compaction sodium-ion battery composite cathode material and have good electrical contact during charge and discharge, thereby further improving the electrochemical performance of the prepared battery.

[0043] Preferably, the mass ratio of the usage amount of the oxalate compound to mannitol monooleate is 1: 0.2 - 0.9.

[0044] The present invention has the following beneficial effects compared with the prior art: The present invention provides a high-compaction sodium-ion battery composite cathode material, its preparation method and application. First, a carbonate and a metal oxide are mixed, a solvent is added and stirred, and then a sanding treatment is carried out to obtain a suspension; the suspension is spray-dried to obtain a dry powder precursor; the dry powder precursor is further heated and kept warm to obtain an O3-type layered oxide. The obtained O3-type layered oxide, an iron source, a sodium source, phosphoric acid and a carbon source are added to a solvent and sanded and mixed to obtain a suspension; the suspension is dried to obtain a dry powder precursor; the dry powder precursor is heated, kept warm and airflow-crushed to obtain the high-compaction sodium-ion battery composite cathode material. The positive electrode sheet made of the high-compaction sodium-ion battery composite cathode material prepared by the present invention has a high compaction density, the button cell made has a large reversible capacity and a good cycle retention rate, and has good application prospects in large-scale industrial production. Description of the Drawings

[0045] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained based on the provided drawings.

[0046] Figure 1 It is a transmission electron microscope image of the high-compaction sodium-ion battery composite cathode material. Specific embodiments

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0048] The following will first explain the concepts involved in this application with reference to the drawings. It should be noted here that the following explanations of each concept are only for making the content of this application easier to understand, and do not represent a limitation on the protection scope of this application; at the same time, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in combination with the embodiments.

[0049] Example 1: Preparation of O3-type layered oxide: Mix sodium carbonate, iron(III) oxide, manganese dioxide, nickel oxide, magnesium oxide and aluminum oxide, then add water and stir for dispersion for 0.5 h, and then perform sand grinding treatment at 2500 rpm for 1.5 h to obtain a suspension. At a feeding rate of 200 °C and 250 mL / h, the suspension is spray-dried to obtain a dry powder precursor. Under a nitrogen atmosphere, the dry powder precursor is heated to 600 °C at a heating rate of 5 °C / min, held for 4 h, and then heated to 950 °C and held for 12 h to obtain O3-NaFe 0.4 Mn 0.3 Ni 0.2 Mg 0.05 Al 0.05 O 2 , that is, the O3-type layered oxide. The molar ratio of the usage amount of sodium carbonate to iron(III) oxide is 1:0.4, the molar ratio of the usage amount of sodium carbonate to manganese dioxide is 1:0.6, the molar ratio of the usage amount of sodium carbonate to nickel oxide is 1:0.4, the molar ratio of the usage amount of sodium carbonate to magnesium oxide is 1:0.1, the molar ratio of the usage amount of sodium carbonate to aluminum oxide is 1:0.1, and the molar ratio of the usage amount of sodium carbonate to water is 1:34.53.

[0050] Preparation of a high-compaction sodium-ion battery composite cathode material: O3-type layered oxide, ferrous oxalate, sodium pyrophosphate, ammonium dihydrogen phosphate, and oxalic acid are added to ethanol and milled and mixed for 12 h to obtain a suspension. The suspension is dried in a boiling manner at 100 °C and a gas flow rate of 3 m / s for 40 min to obtain a dry powder precursor. Under a nitrogen atmosphere, the dry powder precursor is heated to 300 °C at a heating rate of 2 °C / min, held for 6 h, and then heated to 550 °C and held for 10 h. Finally, airflow pulverization is performed to obtain O3-NaFe 0.4 Mn 0.3 Ni 0.2 Mg 0.05 Al 0.05 O 2 @Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) / C, that is, the high-compaction sodium-ion battery composite cathode material. The mass ratio of the usage amounts of ferrous oxalate to the O3-type layered oxide is 1:1.45, the mass ratio of the usage amounts of ferrous oxalate to sodium pyrophosphate is 1:0.62, the mass ratio of the usage amounts of ferrous oxalate to ammonium dihydrogen phosphate is 1:0.54, the mass ratio of the usage amounts of ferrous oxalate to oxalic acid is 1:0.46, and the mass ratio of the usage amounts of ferrous oxalate to ethanol is 1:9.48.

[0051] Example 2: The preparation of the O3-type layered oxide is the same as in Example 1.

[0052] Preparation of the oxalate compound: 5-cyano-2-hydroxy-3-methoxybenzoic acid and 3-diethylamino-1-propanol are mixed, and then concentrated sulfuric acid is added, and the reaction is carried out at 120 °C for 8 h. After the reaction is completed, the pH is adjusted to 9, and the oil layer is washed successively with water and saturated sodium chloride solution, and then rotary evaporated. n-Hexane is added for crystallization and drying to obtain an intermediate. Under nitrogen conditions, toluene, triethylamine, and oxalyl chloride solution are added to the intermediate, and the reaction is carried out at 25 °C for 2 h. After the reaction is completed, rotary evaporation is carried out, and then recrystallization with dichloromethane is carried out, and finally drying is carried out to obtain the oxalate compound. The mass ratio of the usage amounts of 5-cyano-2-hydroxy-3-methoxybenzoic acid to 3-diethylamino-1-propanol is 1:3, the dosage ratio of 5-cyano-2-hydroxy-3-methoxybenzoic acid to concentrated sulfuric acid is 1 g:0.08 ml, the saturated sodium chloride solution is composed of sodium chloride and water, the dosage ratio of the intermediate to toluene is 1 g:0.47 ml, the mass ratio of the usage amounts of the intermediate to triethylamine is 1:0.32, the oxalyl chloride solution is composed of oxalyl chloride and toluene, the dosage ratio of oxalyl chloride to toluene is 1 g:1.69 ml, and the mass ratio of the usage amounts of the intermediate to the oxalyl chloride solution is 1:0.79.

[0053] Preparation of the composite cathode material for high-compaction sodium-ion batteries: Add O3-type layered oxide, ferrous oxalate, sodium pyrophosphate, ammonium dihydrogen phosphate, and oxalate compound into ethanol, and grind and mix them for 12 h to obtain a suspension. Boil and dry the suspension at 100 °C and a gas flow rate of 3 m / s for 40 min to obtain a dry powder precursor. Under a nitrogen atmosphere, heat the dry powder precursor to 300 °C at a heating rate of 2 °C / min, hold for 6 h, and then heat it to 550 °C and hold for 10 h. Finally, perform air jet milling to obtain O3-NaFe 0.4 Mn 0.3 Ni 0.2 Mg 0.05 Al 0.05 O 2 @Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) / C, that is, the composite cathode material for high-compaction sodium-ion batteries. Among them, the mass ratio of the usage amount of ferrous oxalate to the O3-type layered oxide is 1:1.45, the mass ratio of the usage amount of ferrous oxalate to sodium pyrophosphate is 1:0.62, the mass ratio of the usage amount of ferrous oxalate to ammonium dihydrogen phosphate is 1:0.54, the mass ratio of the usage amount of ferrous oxalate to the oxalate compound is 1:0.46, and the mass ratio of the usage amount of ferrous oxalate to ethanol is 1:9.48.

[0054] Example 3: The preparation of the O3-type layered oxide is the same as that in Example 1.

[0055] The preparation of the oxalate compound is the same as that in Example 2.

[0056] Preparation of the composite cathode material for high-compaction sodium-ion batteries: In this example, compared with Example 2, the difference in the preparation of the composite cathode material for high-compaction sodium-ion batteries is that the mass ratio of the usage amount of ferrous oxalate to the oxalate compound is 1:0.82, and other conditions and parameters are the same as those in Example 2.

[0057] Example 4: The preparation of the O3-type layered oxide is the same as that in Example 1.

[0058] The preparation of the oxalate compound is the same as that in Example 2.

[0059] Preparation of the composite cathode material for high-compaction sodium-ion batteries: In this example, compared with Example 2, the difference in the preparation of the composite cathode material for high-compaction sodium-ion batteries is that the mass ratio of the usage amount of ferrous oxalate to the oxalate compound is 1:0.25, and other conditions and parameters are the same as those in Example 2.

[0060] Example 5: The preparation of the O3-type layered oxide was the same as in Example 1.

[0061] The preparation of the oxalate compound was the same as in Example 2.

[0062] Preparation of the high-compaction sodium-ion battery composite cathode material: The O3-type layered oxide, iron oxalate, sodium pyrophosphate, ammonium dihydrogen phosphate, oxalate compound, and mannitol monooleate were added to ethanol and milled and mixed for 12 h to obtain a suspension. The suspension was dried by boiling at 100 °C and a gas flow rate of 3 m / s for 40 min to obtain a dry powder precursor. Under a nitrogen atmosphere, the dry powder precursor was heated to 300 °C at a heating rate of 2 °C / min, held for 6 h, and then heated to 550 °C and held for 10 h. Finally, it was pulverized by air flow to obtain O3-NaFe 0.4 Mn 0.3 Ni 0.2 Mg 0.05 Al 0.05 O 2 @Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) / C, that is, the high-compaction sodium-ion battery composite cathode material. The mass ratio of the usage amounts of iron oxalate to the O3-type layered oxide was 1:1.45, the mass ratio of the usage amounts of iron oxalate to sodium pyrophosphate was 1:0.62, the mass ratio of the usage amounts of iron oxalate to ammonium dihydrogen phosphate was 1:0.54, the mass ratio of the usage amounts of iron oxalate to the oxalate compound was 1:0.46, the mass ratio of the usage amounts of the oxalate compound to mannitol monooleate was 1:0.3, and the mass ratio of the usage amounts of iron oxalate to ethanol was 1:9.48.

[0063] Example 6: The preparation of the O3-type layered oxide was the same as in Example 1.

[0064] The preparation of the oxalate compound was the same as in Example 2.

[0065] Preparation of the high-compaction sodium-ion battery composite cathode material: In this example, the preparation of the high-compaction sodium-ion battery composite cathode material was different from that in Example 2 in that the mass ratio of the usage amounts of the oxalate compound to mannitol monooleate was 1:0.8, and other conditions and parameters were the same as in Example 5.

[0066] Comparative Example 1: Preparation of the composite cathode material for high-compaction sodium-ion batteries: Ferrous oxalate, sodium pyrophosphate, ammonium dihydrogen phosphate, and oxalic acid were added to ethanol and milled and mixed for 12 h to obtain a suspension. The suspension was dried in a boiling manner at 100 °C and a gas flow rate of 3 m / s for 40 min to obtain a dry powder precursor. Under a nitrogen atmosphere, the dry powder precursor was heated to 300 °C at a heating rate of 2 °C / min, held for 6 h, and then heated to 550 °C and held for 10 h. Finally, airflow comminution was carried out to obtain Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) / C, that is, the composite cathode material for high-compaction sodium-ion batteries. Among them, the mass ratio of the usage amounts of ferrous oxalate to sodium pyrophosphate is 1:0.62, the mass ratio of the usage amounts of ferrous oxalate to ammonium dihydrogen phosphate is 1:0.54, the mass ratio of the usage amounts of ferrous oxalate to oxalic acid is 1:0.46, and the mass ratio of the usage amounts of ferrous oxalate to ethanol is 1:6.11.

[0067] Comparative Example 2: The preparation of the O3-type layered oxide was the same as in Example 1.

[0068] The preparation of the oxalate compound was the same as in Example 2.

[0069] Preparation of the composite cathode material for high-compaction sodium-ion batteries: In this example, the preparation of the composite cathode material for high-compaction sodium-ion batteries was different from that in Example 2 in that the mass ratio of the usage amounts of ferrous oxalate to the oxalate compound was 1:0.05, and other conditions and parameters were the same as in Example 2.

[0070] Experimental Example 1: The composite cathode material for high-compaction sodium-ion batteries prepared in Example 1 was observed for its electron microscopy microstructure, and the results are as Figure 1 shown.

[0071] Experimental Example 2: Preparation of the button cell: The composite cathode material for high-compaction sodium-ion batteries, Super P, and polyvinylidene fluoride binder were mixed, several zirconia beads with a diameter of 3 mm were added, and the mixture was ball-milled for 4 h to obtain a mixed slurry. The slurry was coated on aluminum foil, placed in a vacuum at 100 °C and dried for 6 h, and then cut into pieces to obtain a positive electrode sheet, which was used as the working electrode. Using metallic sodium as the counter electrode, NaClO 4The electrolyte is the electrolyte, and a button cell is assembled under the conditions that the O content in the air is ≤ 0.01% and the water content is ≤ 0.01%. The mass ratio of the usage amounts of the high-compaction sodium-ion battery composite cathode material, Super P, and polyvinylidene fluoride binder is 96:2:2. The high-compaction sodium-ion battery composite cathode material includes the high-compaction sodium-ion battery composite cathode materials prepared in Example 1 and Comparative Example 1.

[0072] Weigh the positive electrode sheet and calculate the tap density.

[0073] Table 1 Results of tap density measurement

[0074] The results of tap density measurement of the positive electrode sheets made of the high-compaction sodium-ion battery composite cathode materials prepared in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1. Comparing Example 1 with Comparative Example 1 shows that using the O3-type layered oxide can form a closely packed structure and improve the tap density of the positive electrode sheet made of the prepared high-compaction sodium-ion battery composite cathode material.

[0075] Experimental Example 3: The preparation of the button cell is the same as that in Experimental Example 2. The high-compaction sodium-ion battery composite cathode material includes the high-compaction sodium-ion battery composite cathode materials prepared in Examples 1-6 and Comparative Examples 1-2.

[0076] Perform a constant current charge-discharge test on the button cell to obtain the reversible capacity. The test voltage window is 2.0 - 4.0 V and the rate is 0.1C.

[0077] Table 2 Results of reversible capacity measurement

[0078] The measurement results of the reversible capacities of the button cells made of the high-compaction sodium-ion battery composite cathode materials prepared in Examples 1-6 and Comparative Examples 1-2 are shown in Table 2. Comparing Example 1 with Example 2, the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material prepared in Example 2 is higher than that in Example 1, indicating that the use of oxalate compounds can increase the reversible capacity. Comparing Example 2 with Example 3 shows that an increase in the amount of oxalate compounds within a certain range can increase the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material. Comparing Example 2 with Example 4 shows that a decrease in the amount of oxalate compounds within a certain range will reduce the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material. Comparing Example 2 with Example 5 shows that on the basis of using oxalate compounds, the use of mannitol monooleate can further increase the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material. Comparing Example 5 with Example 6 shows that an increase in the amount of mannitol monooleate within a certain range can increase the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material. Comparing Example 1 with Comparative Example 1 shows that the use of O3-type layered oxides can increase the reversible capacity of the button cell made of the prepared high-compaction sodium-ion battery composite cathode material. Comparing Example 2 with Comparative Example 2 shows that the amount of oxalate compounds needs to be within a suitable range, and too low an amount has no obvious effect on increasing the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material.

[0079] Experimental Example 4: The button cells were prepared in the same way as in Experimental Example 2. The high-compaction sodium-ion battery composite cathode materials include the high-compaction sodium-ion battery composite cathode materials prepared in Examples 1-6 and Comparative Examples 1-2.

[0080] The cycle life of the button cells was tested to obtain the capacity retention rate after 200 cycles. The test voltage window was 2.0 - 4.0 V and the rate was 0.1C.

[0081] Table 3 Measurement Results of Capacity Retention Rate

[0082] The measurement results of the capacity retention rate of the button cells made of the high-compaction sodium-ion battery composite cathode materials prepared in Examples 1-6 and Comparative Examples 1-2 are shown in Table 3. Comparing Example 1 with Example 2, the reversible capacity of the button cell made of the high-compaction sodium-ion battery composite cathode material prepared in Example 2 is higher than that in Example 1, indicating that the use of the oxalate compound can improve the capacity retention rate; comparing Example 2 with Example 3, it shows that the increase in the amount of the oxalate compound within a certain range can improve the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material; comparing Example 2 with Example 4, it shows that the decrease in the amount of the oxalate compound within a certain range will reduce the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material; comparing Example 2 with Example 5, it shows that on the basis of using the oxalate compound, the use of mannitol monooleate can further improve the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material; comparing Example 5 with Example 6, it shows that the increase in the amount of mannitol monooleate within a certain range can improve the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material; comparing Example 1 with Comparative Example 1, it shows that the use of the O3-type layered oxide can improve the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material prepared; comparing Example 2 with Comparative Example 2, it shows that the amount of the oxalate compound needs to be within a suitable range, and too low amount has no obvious effect on improving the capacity retention rate of the button cell made of the high-compaction sodium-ion battery composite cathode material.

[0083] The above-mentioned embodiments and / or implementation manners are only used to illustrate the preferred embodiments and / or implementation manners for realizing the technology of the present invention, and do not impose any formal restrictions on the implementation manners of the technology of the present invention. Any person skilled in the art, without departing from the scope of the technical means disclosed in the content of the present invention, may make some changes or modifications to other equivalent embodiments, but should still be regarded as the same technology or embodiment as the present invention in essence.

[0084] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. The above is only the preferred implementation manner of the present application. It should be noted that due to the limitation of literal expression and objectively existing infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present application, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, should all be regarded as the protection scope of the present application.

Claims

1. A method for preparing a composite positive electrode material for a high-pressure sodium ion battery, comprising: S1: mixing carbonate and metal oxide, adding solvent and stirring, and then sand-milling to obtain a suspension; spray drying the suspension to obtain a dry powder precursor; In a nitrogen atmosphere, the dry powder precursor is then heated and kept warm to obtain an O3-type layered oxide; S2: Add O3 type layered oxide, iron source, sodium source, phosphorus source and carbon source into a solvent and grind them to obtain a suspension; dry the suspension to obtain a dry powder precursor; in a nitrogen atmosphere, the dry powder precursor is subjected to heating, heat preservation and air flow pulverization to obtain a high-density sodium ion battery composite positive electrode material; the mass ratio of the iron source to the O3 type layered oxide is 1:1-2.

2. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: In the S1, the carbonate is sodium carbonate; the metal oxides are ferric oxide, manganese dioxide, nickel oxide, magnesium oxide and aluminum oxide; the solvent is water, and the molar ratio of the carbonate to the solvent is 1:30-40.

3. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 2, characterized in that: The molar ratio of sodium carbonate to ferric oxide in S1 is 1:0.2-0.6, the molar ratio of sodium carbonate to manganese dioxide is 1:0.4-0.8, the molar ratio of sodium carbonate to nickel oxide is 1:0.2-0.6, the molar ratio of sodium carbonate to magnesium oxide is 1:0.05-0.2, and the molar ratio of sodium carbonate to aluminum oxide is 1:0.05-0.

2.

4. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: The iron source in S2 is at least one of ferrous oxalate, ferric nitrate, ferrous acetate, ferric phosphate and ferric nitrate; the solvent is ethanol, and the mass ratio of the iron source to the solvent is 1:8-11.

5. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: The sodium source in S2 is at least one of sodium carbonate, sodium acetate, sodium oxalate, sodium pyrophosphate, sodium hydroxide, sodium chloride and disodium hydrogen phosphate; the mass ratio of the iron source to the sodium source is 1:0.5-1.

6. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: The phosphorus source in S2 is at least one of phosphoric acid, ammonium dihydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; the mass ratio of the iron source to the phosphorus source is 1:0.3-0.

9.

7. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: The carbon source in S2 is at least one of glucose, citric acid, sucrose, ascorbic acid, carbon nanotubes, reduced graphene oxide, oxalic acid and oxalate compounds; the mass ratio of the iron source to the carbon source is 1:0.2-1.8; the oxalate compound is prepared from 5-cyano-2-hydroxy-3-methoxybenzoic acid, 3-diethylamino-1-propanol and oxalyl chloride.

8. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: In the S1, the stirring time is 0.3-1h, the sand milling speed is 2000-3000rpm, the sand milling time is 1-2h, the spray drying temperature is 180-220°C, the spray drying feed rate is 250mL / h, the heating rate of the dry powder precursor is 3-6°C / min, the heating temperature is 550-1000°C, and the insulation time is 15-20h.

9. The method for preparing a high-density sodium ion battery composite positive electrode material according to claim 1, characterized in that: In the S2, the sand milling mixing time is 10-15h, the drying temperature is 90-110°C, the drying air flow velocity is 2-5 m / s, the heating rate of the dry powder precursor is 1-3°C / min, the heating temperature is 250-600°C, and the insulation time is 15-20h.

10. A battery comprising the high-density sodium ion battery composite positive electrode material prepared by the method according to any one of claims 1 to 9.

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