Aluminum phosphate modification-based sodium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses a sodium ion battery positive electrode material based on aluminum phosphate modification and a preparation method thereof. The preparation method comprises the steps of preparation of layered aluminum phosphate fragments, preparation of a layered oxide precursor, wet coating of the layered oxide precursor, preparation of a modified layered oxide and the like. The preparation method comprises the following steps: carrying out wet coating on a layered oxide precursor by adopting layered aluminum phosphate for the first time to form a petal-shaped crystal polymer, and then preparing the modified layered oxide coated with aluminum phosphate on the surface by utilizing the damage to the layered structure of the layered aluminum phosphate in the sintering process and the change of the precursor from a sphere-like structure to a layered structure. The composite material has the characteristics of long-acting inhibition of surface residual alkali and high stability, and the prepared battery has high specific capacity and cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy battery materials, and particularly relates to a sodium ion battery positive electrode material based on aluminum phosphate modification and a preparation method thereof. BACKGROUND

[0002] As a new type of energy storage technology, sodium ion batteries gradually become a research hotspot due to their low cost and abundant resources. As a core component of sodium ion batteries, the performance of the positive electrode material directly affects the overall performance of the battery. The positive electrode material of the sodium ion battery mainly includes layered oxides, prussian blue and polyanions. Among them, layered oxides are considered as a high-capacity sodium ion battery positive electrode material with broad application prospects due to their high theoretical capacity and high air stability.

[0003] Layered metal oxides are generally prepared by a solid phase method or a coprecipitation method. The solid phase method is simple and low in cost, but the material uniformity and surface residual alkali control need to be paid attention to. The coprecipitation method prepares a precursor by the reaction of a metal salt solution with sodium hydroxide and ammonia water, and then obtains a positive electrode material by high-temperature calcination. The product performance is relatively good. At present, the solid phase method is mainly used for the preparation of copper-based positive electrodes, and the coprecipitation method is mainly used for the preparation of nickel-based positive electrodes.

[0004] However, in practical applications, the layered oxide positive electrode material still has some problems. For example, when charged to above 4.0V, a large volume phase change from P2 to O2 and irreversible oxygen release occur, resulting in rapid decay of battery capacity and voltage. In addition, different sodium ion / vacancy ordered rearrangements and transition metal rearrangements below 4.0V reduce the sodium ion diffusion kinetics, resulting in unsatisfactory rate performance of the electrode material at a large current density. However, the more serious problem is the residual alkali problem of the layered oxide.

[0005] The residual alkali on the surface of the layered oxide makes it very sensitive to air, which seriously hinders its practical application. During high-temperature calcination in the presence of air, high-activity Na + , with the prolongation of calcination time, Na + seeps into the bulk phase and combines with interlayer oxygen atoms to form layered oxides. In the subsequent natural cooling, electrical cycling and other processes, these ions gradually lose activity and react with carbon dioxide and oxygen in the atmosphere to form amorphous sodium carbonate on the surface of the particles, i.e. residual alkali. The residual alkali will cause sol-gel transition of the positive electrode material slurry, complicate the coating process and reduce the electrochemical performance of the material. The remaining Na substance reacts with the electrolyte to produce gas, causing the battery to swell, which poses a major safety hazard.

[0006] At present, the modification of layered oxides mainly includes modification of precursors and secondary modification of coating of layered oxides, but in actual use, the stability of the modification or coating is difficult to be guaranteed for a long time after the battery is packaged, and further improvement is still needed. SUMMARY

[0007] The purpose of the present application is to solve the problems existing in the prior art, to coat the precursors with layered aluminum phosphate, and to prepare a modified layered oxide with aluminum phosphate (weak acid) coating on the surface by using the destruction of the layered structure of the layered aluminum phosphate during sintering and the change of the precursor from a spherical shape to a layered structure, which has the characteristics of long-term inhibition of surface residual alkali, namely a sodium ion battery cathode material modified based on aluminum phosphate and a preparation method thereof are proposed.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: The present application first proposes a preparation method of a sodium ion battery cathode material, comprising the following steps: S1, preparation of layered aluminum phosphate fragments: S101, preparation of layered aluminum phosphate: 2.0g of aluminum isopropoxide is added to 16.0mL of sec-butanol, 4.8mL of 4-methylpyridine is added under stirring, and finally 2.72mL of 85wt% phosphoric acid aqueous solution is added. After the gel is formed, it is put into a reaction kettle and crystallized at 160℃ for 12 days. The product is filtered, washed, and dried in air to obtain layered aluminum phosphate AIP ([Al2P3O 10 (OH)2][C6NH8]); S102, exfoliation of layered aluminum phosphate: At room temperature, the layered aluminum phosphate AIP is dissolved in a solution with a solute of water-alcohol mixed solution and a butylamine amount of 10mmol / g AIP. After 3 days of reaction, a reaction liquid A is obtained. The AIP before the reaction has a regular flat plate type layered structure (about 10μm). During the exfoliation process, part of the Al-O-P bonds on the layer plate hydrolyze and break into Al-OH bonds and P-OH bonds, and the large layer plate forms small flaky particles (<1μm). After the embedding of the alkyl amine, a new crystal is formed, which has a great difference in morphology from the AIP crystal before the reaction, and is a petal-shaped crystal aggregate (about 5μm). This change in morphology is mainly due to the fact that most layered crystals grow in an edge-to-edge aggregation manner, and similar phenomena also occur in other layered materials; S103, breaking of layered aluminum phosphate: The reaction liquid A is directly ground by a grinding crusher. The original reaction liquid is a mixed system of easy settlement and solid-liquid stratification. After grinding, a colloidal solution B of difficult settlement and light yellow whitish color is obtained. The solid content of the layered aluminum phosphate fragments in the solution is 35.6%, and the edge length size of the layered aluminum phosphate fragments is 1.1-1.6 μm. S2, preparation of a layered oxide precursor: Under an inert gas atmosphere, a nickel-iron-manganese mixed salt solution, a precipitant and ammonia water are continuously added to a reaction bottom liquid. The pH value is controlled to be 11.5±0.6, the NH3 content is controlled to be 4.0±0.5 g / L, the temperature is controlled to be 50℃, the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, and the reaction is performed for 5-6 h to obtain a reaction liquid C containing a layered oxide precursor. The particle size in the system is 6-8 μm. S3, wet coating of the layered oxide precursor: S301, the colloidal solution B is poured into the reaction liquid C, and a 25wt% NaOH aqueous solution is continuously poured. The pH value is controlled to be 11.5±0.6, the temperature is controlled to be 50℃, and the stirring reaction is performed at 40-50 r / min for 1.5-2 h to obtain a reaction liquid D. S302, the reaction liquid D is subjected to washing and pressure filtration, and a filter cake E is obtained by dehydration using a solid-liquid separation device. S303, the filter cake E is poured into a disc dryer. The drying temperature range is 120±5℃, and the water content of the qualified powder after the disc dryer is discharged is controlled to be less than 0.5%. A modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. The particle size is 10-13 μm, and the surface has a large number of wrinkles, indicating that the loading of the layered aluminum phosphate fragments is successful. S4, preparation of a modified layered oxide: The modified layered oxide precursor F and sodium carbonate are uniformly mixed in a mixer, and sintered at 800℃ in an atmosphere furnace for 10 h. After natural cooling to room temperature, a modified layered oxide is obtained.

[0009] Preferably, in S102, the volume ratio of water to ethanol in the water-alcohol mixed solution is 3:1.

[0010] Preferably, the grinding crusher in S103 is a Yubang small grinding crusher, and the inner cavity is made of 316 stainless steel. The grinding speed is 30 r / min, and low-speed grinding avoids the premature granulation or spheroidization of the layered structure.

[0011] Preferably, the preparation process of the reaction bottom liquid in S2 is as follows: A 2500 L closed synthesis reactor is added with a 0.01wt% Na2S2O3 aqueous solution, ammonia water is added to make the NH3 content 4.0±0.5 g / L, and a NaOH aqueous solution is added to make the OH -The content is 1-3 g / L, the temperature of the reaction kettle is controlled at 50°C, nitrogen is introduced for 2 h, the nitrogen flow is 4.5±0.5 m 3 / h, and the reaction gas atmosphere in the synthesis reaction kettle is replaced with an inert gas atmosphere.

[0012] Preferably, the preparation process of the nickel-iron-manganese mixed salt solution in S2 is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0013] Preferably, the preparation process of the precipitant in S2 is as follows: A NaOH aqueous solution with a mass concentration of 25wt% is configured, and Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass fraction of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0014] Preferably, in S301, the weight ratio of the solids in the colloidal solution B to the solids in the reaction liquid C is controlled to be 1-1.5:10, and the layered aluminum phosphate fragments are used for coating the layered oxide precursor. When the content is too low, the coating is not complete, and when the content is too high, the coating is too dense, which may cause the wrinkle to fold on each other, which may affect the later sintering reaction with the Na source, and at the same time, the excess nickel, iron and manganese which are not completely precipitated continue to precipitate or are adsorbed in the wrinkle.

[0015] Preferably, in S302, the washing liquid used for pressure filtration is a NaOH aqueous solution with a mass concentration of 2wt% and deionized water, and the temperature range is 50±5°C. The NaOH aqueous solution is used to wash part of metal impurities and S impurities, and the deionized water is used to wash impurity Na.

[0016] Preferably, in S4, the molar ratio of the total ions of nickel, iron and manganese to sodium ions in the modified layered oxide precursor F is controlled to be 1:0.96, and the modified layered oxide is Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 ; According to the previous research and test, the modified layered oxide precursor F in S303 is sintered, and the steps are as follows: the modified layered oxide precursor F is sintered at 800°C in an atmosphere furnace for 10 h, and then naturally cooled to room temperature to obtain a layered oxide@Al2P3O 11 aggregate. The modified layered oxide precursor F before sintering and the layered oxide@Al2P3O 11The change of the surface wrinkle of the aggregate. The layered aluminum phosphate is destroyed at more than 400 DEG C, and dispersed granular particles are attached to the surface of the layered oxide precursor, and aluminum phosphate film is formed, which is beneficial to Na ion shuttling, and after the organic amine is evaporated, the amphoteric passivated aluminum oxide and the acidic phosphorus oxide are produced, which can greatly reduce the surface residual alkali of the layered oxide.

[0017] The application also provides a layered positive electrode material for a sodium ion battery based on aluminum phosphate modification prepared by the preparation method.

[0018] Compared with the prior art, the application has the following beneficial effects: 1. In the application, the layered aluminum phosphate fragments are coated on the surface of the layered oxide precursor by a wet coating process to form petal-shaped crystal aggregates; in the high-temperature sintering process (> 400 DEG C), the layered structure of the layered aluminum phosphate fragments is destroyed to form dispersed granular particles attached to the surface of the layered oxide precursor, and aluminum phosphate film is formed, which is beneficial to Na ion shuttling, thereby improving the electrochemical performance of the material.

[0019] 2. In the application, the layered aluminum phosphate fragments coated on the surface of the novel modified layered oxide precursor F will generate amphoteric passivated aluminum oxide and acidic phosphorus oxide after high-temperature sintering, and these substances can react with the residual alkali on the surface of the layered oxide, thereby reducing the surface residual alkali content and improving the stability and cycle performance of the positive electrode material.

[0020] 3. In addition, the aluminum phosphate particles formed by the conversion of the layered aluminum phosphate fragments can effectively inhibit the structural change of the layered oxide during the charging and discharging process, reduce the occurrence of irreversible phase change, and improve the cycle stability of the material. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The battery cycle capacity test curve of the positive electrode material prepared in the application; Figure 2 The SEM image of the modified layered oxide precursor F prepared in Example 2 of the application; Figure 3 The SEM image of the layered oxide @ Al2P3O 11 The SEM image of the aggregate. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the prior known technology. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application.

[0023] I. Preparation of layered aluminum phosphate fragments: Preparation Example 1 Preparation of layered aluminum phosphate fragments: Reference: Study on exfoliation and intercalation of microporous layered aluminum phosphate materials, Huang Qiong et al, Higher School Chemistry Journal, November 2004, 25-11: 2065-2069; S101, Preparation of layered aluminum phosphate: 2.0 g of aluminum isopropoxide was added to 16.0 mL of sec-butanol, 4.8 mL of 4-methylpyridine was added under stirring, and finally 2.72 mL of 85 wt% phosphoric acid aqueous solution was added. After the gel was formed, it was put into a reaction kettle and crystallized at 160°C for 12 days. The product was filtered, washed, and dried in air to obtain layered aluminum phosphate AIP ([Al2P3O 10 (OH)2][C6NH8]); S102, Exfoliation of layered aluminum phosphate: At room temperature, the layered aluminum phosphate AIP was dissolved in a solution with a solute of water-ethanol mixture and a butylamine amount of 10 mmol / g AIP. After 3 days of reaction, reaction liquid A was obtained. The AIP before the reaction had a regular flat plate type layered structure (about 10 μm). During the exfoliation process, part of the Al-O-P bonds on the layer plate were hydrolyzed to break into Al-OH bonds and P-OH bonds, and the large layer plate was formed into small flaky particles (<1 μm). After the intercalation of the alkyl amine, a new crystal was formed, which had a great difference in morphology from the AIP crystal before the reaction, and was a petal-shaped crystal aggregate (about 5 μm). The change in the morphology was mainly due to the fact that the layered crystal mostly adopted an edge-to-edge aggregation mode during the growth process, and similar phenomena also occurred in other layered materials; S103, Fragmentation of layered aluminum phosphate: The reaction liquid A was directly ground by using a grinding crusher. The original reaction liquid was an easily settled, solid-liquid layered mixed system. After grinding, a difficult-to-settle, light yellow whitish colloidal solution B was obtained. The solid content of the layered aluminum phosphate fragments in the solution was 35.6%, and the edge length size of the layered aluminum phosphate fragments was 1.1-1.6 μm. In S102, the volume ratio of water to ethanol in the water-ethanol mixture was 3:1. The grinding crusher in S103 was a Yubang small grinding crusher, the inner cavity was made of 316 stainless steel, and the grinding rotation speed was 30 r / min. The low-speed grinding avoided the premature granulation or spheroidization of the layered structure.

[0024] II. Synthesis of a layered positive electrode material for a sodium ion battery: Example 1: 1. Preparation of a layered oxide precursor: Partly referring to Chinese patent CN 119461515 A, a nickel-iron-manganese layered oxide precursor, its preparation method and application: Under the inert gas atmosphere, the nickel-iron-manganese mixed salt solution, the precipitant and ammonia water are continuously added into the reaction bottom solution, the pH value is controlled to be 11.5±0.6, the NH3 content is 4.0±0.5 g / L, the temperature is 50℃, the flow rate of the nickel-iron-manganese mixed salt solution is 350 L / h, the reaction is carried out for 5-6 h, and a reaction liquid C containing the layered oxide precursor is obtained, and the particle size in the system is 6-8 μm; The preparation process of the reaction bottom solution is as follows: Into the closed synthesis reaction kettle, 2500 L of the Na2S2O3 aqueous solution with a mass concentration of 0.01 wt% is added, the ammonia water is added to make the NH3 content be 4.0±0.5 g / L, the NaOH aqueous solution is added to make the OH - The content is 1-3 g / L, the temperature of the reaction kettle is controlled to be 50℃, the nitrogen gas is introduced for 2 h, the flow rate of the nitrogen gas is 4.5±0.5 m 3 / h, and the reaction atmosphere in the synthesis reaction kettle is replaced to be inert gas atmosphere.

[0025] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0026] The preparation process of the precipitant is as follows: The Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0027] 2. Wet coating of the layered oxide precursor: 1) The colloidal solution B of the preparation example 1 is poured into the reaction liquid C, the weight ratio of the solid in the colloidal solution B to the solid in the reaction liquid C is controlled to be 1:10, the NaOH aqueous solution with a mass concentration of 25 wt% is continuously poured, the pH value is controlled to be 11.5±0.6, the temperature is controlled to be 50℃, the stirring is carried out at 40-50 r / min, and the reaction is carried out for 1.5-2 h to obtain a reaction liquid D; 2) The reaction liquid D is washed and pressure-filtered, and the filter cake E is obtained by dehydration with a solid-liquid separation device; the washing liquid used in the washing and pressure filtration in S302 is the NaOH aqueous solution with a mass concentration of 2 wt% and deionized water, the NaOH aqueous solution is used to wash part of the metal impurities and S impurities, and the deionized water is used to wash the impurity Na; 3) Put the filter cake E into a tray dryer, the drying temperature range is 120±5℃, control the qualified powder moisture content <0.5% after discharging from the tray dryer, get the modified layered oxide precursor F coated with layered aluminum phosphate fragments, the particle size is 10-13μm, the surface has a large number of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful; 3. Preparation of modified layered oxide: Put the modified layered oxide precursor F and sodium carbonate into a mixer and mix uniformly, control the molar ratio of total ions of nickel, iron and manganese in the modified layered oxide precursor F to sodium ions to be 1:0.96, sinter at 800℃ in an atmosphere furnace for 10h, and naturally cool to room temperature to obtain the modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

[0028] Example 2: 1. Preparation of layered oxide precursor: Under inert gas atmosphere, continuously add nickel-iron-manganese mixed salt solution, precipitant and ammonia water into the reaction bottom solution, control the pH value to be 11.5±0.6, the NH3 content to be 4.0±0.5g / L, the temperature to be 50℃, the flow rate of nickel-iron-manganese mixed salt solution to be 350L / h, and react for 5-6h to obtain the reaction liquid C containing layered oxide precursor, and the particle size in the system is 6-8μm; The preparation process of the reaction bottom solution is as follows: Into the closed synthesis reactor, add 2500L of Na2S2O3 aqueous solution with a mass concentration of 0.01wt%, add ammonia water to make the NH3 content be 4.0±0.5g / L, add NaOH aqueous solution to make the OH - content be 1-3g / L, control the temperature of the reactor to be 50℃, pass nitrogen for 2h, the nitrogen flow rate is 4.5±0.5m 3 / h, and replace the reaction atmosphere in the synthesis reactor with inert atmosphere.

[0029] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: Configure the soluble salts of nickel, iron and manganese into a mixed salt solution with a total molar concentration of 2mol / L, and control the molar ratio of nickel, iron and manganese to be 3:4:3.

[0030] The preparation process of the precipitant is as follows: Configure NaOH aqueous solution with a mass concentration of 25wt%, and dissolve Na2S2O3 in the NaOH aqueous solution, the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0031] 2. Wet coating of layered oxide precursor: 1) The colloidal solution B of Preparation Example 1 was put into the reaction liquid C, the weight ratio of solid in the colloidal solution B to solid in the reaction liquid C was controlled to be 1.2:10, the mass concentration of the NaOH aqueous solution was continuously put in at 25wt%, the pH value was controlled to be 11.5±0.6, the temperature was controlled to be 50℃, the reaction was stirred at 40-50r / min for 1.5-2h, and the reaction liquid D was obtained; 2) The reaction liquid D was washed and pressure-filtered, and the filter cake E was obtained by dehydration with a solid-liquid separation device; the washing liquid used in the washing and pressure-filtering in S302 was the NaOH aqueous solution with a mass concentration of 2wt% and deionized water, the NaOH aqueous solution was used to wash part of metal impurities and S impurities, and the deionized water was used to wash the impurity Na; 3) The filter cake E was put into a tray dryer, the drying temperature range was 120±5℃, the water content of the qualified powder after the discharge of the tray dryer was controlled to be <0.5%, and the modified layered oxide precursor F coated with layered aluminum phosphate fragments was obtained, the particle size of which was 10-13μm, and the surface had a large number of wrinkles, indicating that the loading of the layered aluminum phosphate fragments was successful, as shown in Figure 2 (the particle size of the modified layered oxide precursor F was about 12.8μm); The modified layered oxide precursor F was sintered at 800℃ in an atmosphere furnace for 10h, and naturally cooled to room temperature, and the layered oxide @Al2P3O 11 aggregates, such as Figure 3 as shown, wherein the particle size of each sphere was about 11.9-12.4μm, the original aluminum phosphate wrinkles coated on the outer wall of the oxide sphere disappeared, and the surface was attached with a net-like strip (which may be a phosphorus oxide or a phosphorus aluminum compound) and a spherical small particle (which may be aluminum oxide), both of which had the effect of removing the residual alkali on the surface, thereby improving the battery efficiency.

[0032] 3. Preparation of modified layered oxide: The modified layered oxide precursor F and sodium carbonate were mixed uniformly in a mixer, the molar ratio of the total ions of nickel, iron and manganese in the modified layered oxide precursor F to sodium ions was controlled to be 1:0.96, sintering was carried out at 800℃ in an atmosphere furnace for 10h, and the modified layered oxide Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

[0033] Example 3: 1. Preparation of layered oxide precursor: The nickel-iron-manganese mixed salt solution, the precipitant and ammonia water are continuously added into the reaction bottom liquid under inert gas atmosphere, the pH value is controlled to be 11.5±0.6, the NH3 content is controlled to be 4.0±0.5 g / L, the temperature is controlled to be 50℃, the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, the reaction is carried out for 5-6 h, and a reaction liquid C containing the layered oxide precursor is obtained, and the particle size in the system is 6-8 μm; The preparation process of the reaction bottom liquid is as follows: The 2500 L Na2S2O3 aqueous solution with a mass concentration of 0.01 wt% is added into the closed synthesis reaction kettle, the ammonia water is added to make the NH3 content be 4.0±0.5 g / L, the NaOH aqueous solution is added to make the OH - The content is 1-3 g / L, the temperature of the reaction kettle is controlled to be 50℃, the nitrogen gas is introduced for 2 h, the flow rate of the nitrogen gas is 4.5±0.5 m 3 / h, and the reaction atmosphere in the synthesis reaction kettle is replaced to be inert gas atmosphere.

[0034] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0035] The preparation process of the precipitant is as follows: The Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0036] 2. Wet coating of the layered oxide precursor: 1) The colloidal solution B of the preparation example 1 is added into the reaction liquid C, the weight ratio of the solid in the colloidal solution B to the solid in the reaction liquid C is controlled to be 1.5:10, the NaOH aqueous solution with a mass concentration of 25 wt% is continuously added, the pH value is controlled to be 11.5±0.6, the temperature is controlled to be 50℃, the stirring is carried out at 40-50 r / min, and the reaction is carried out for 1.5-2 h to obtain a reaction liquid D; 2) The reaction liquid D is washed and pressure-filtered, the filter cake E is obtained by dehydration with a solid-liquid separation device; the washing liquid used in the washing and pressure filtration in S302 is the NaOH aqueous solution with a mass concentration of 2 wt% and deionized water, the NaOH aqueous solution is used to wash part of metal impurities and S impurities, and the deionized water is used to wash the impurity Na at a temperature of 50±5℃; 3) The filter cake E is added into a tray dryer, the drying temperature is controlled to be 120±5℃, the water content of the qualified powder after the discharge of the tray dryer is controlled to be less than 0.5%, and a modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained, the particle size is 10-13 μm, and the surface has a large number of wrinkles, which indicates that the loading of the layered aluminum phosphate fragments is successful; 3. Preparation of modified layered oxide: The modified layered oxide precursor F and sodium carbonate were placed in a mixer and mixed uniformly, the molar ratio of total ions of nickel, iron and manganese to sodium ions in the modified layered oxide precursor F was controlled to be 1:0.96, sintering at 800℃ in an atmosphere furnace for 10h, and naturally cooled to room temperature to obtain the modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O3 11 .

[0037] Comparative Example 1: 1. Preparation of layered oxide precursor: The nickel-iron-manganese mixed salt solution, precipitant and ammonia water were continuously added in the reaction bottom liquid under inert gas atmosphere, the pH value was controlled to be 11.5±0.6, the NH3 content was 4.0±0.5g / L, the temperature was 50℃, the flow rate of nickel-iron-manganese mixed salt solution was 350L / h, and the reaction time was 5-6h to obtain the reaction liquid C containing layered oxide precursor, and the particle size in the system was 6-8μm; The preparation process of the reaction bottom liquid was as follows: A 2500L Na2S2O3 aqueous solution with a mass concentration of 0.01wt% was added into a closed synthesis reactor, ammonia water was added to make the NH3 content 4.0±0.5g / L, NaOH aqueous solution was added to make the OH - content 1-3g / L, the temperature of the reactor was controlled to be 50℃, nitrogen gas was introduced for 2h, the flow rate of nitrogen gas was 4.5±0.5m 3 / h, and the reaction atmosphere in the synthesis reactor was replaced to be inert atmosphere.

[0038] The preparation process of the nickel-iron-manganese mixed salt solution was as follows: The soluble salts of nickel, iron and manganese were configured into a mixed salt solution with a total molar concentration of 2mol / L, and the molar ratio of nickel, iron and manganese was controlled to be 3:4:3.

[0039] The preparation process of the precipitant was as follows: Na2S2O3 was dissolved in NaOH aqueous solution, and the mass ratio of Na2S2O3 in NaOH aqueous solution was 0.01%.

[0040] 2. Wet coating of layered oxide precursor: 1) Put the reaction liquid A of Preparation Example 1 into the reaction liquid C, control the weight ratio of the solid in the reaction liquid A to the solid in the reaction liquid C to be 1.2:10, continuously put the aqueous solution of NaOH with a mass concentration of 25wt%, control the pH value to be 11.5±0.6 and the temperature to be 50℃, stir the reaction at 40-50r / min for 1.5-2h to obtain the reaction liquid D; 2) Wash and filter the reaction liquid D by using a solid-liquid separation device to obtain the filter cake E; the washing liquid used in the washing and filtering in S302 is the aqueous solution of NaOH with a mass concentration of 2wt% and deionized water, the aqueous solution of NaOH is used to wash part of the metal impurities and S impurities and the deionized water is used to wash the impurity Na at a temperature range of 50±5℃; 3) Put the filter cake E into a tray dryer, control the drying temperature range to be 120±5℃, control the water content of the qualified powder after the discharge of the tray dryer to be <0.5% to obtain the modified layered oxide precursor F coated with layered aluminum phosphate fragments, the particle size of which is 10-13μm and the surface of which has a large number of wrinkles, indicating that the loading of the layered aluminum phosphate fragments is successful; 3. Preparation of the modified layered oxide: Put the modified layered oxide precursor F and sodium carbonate into a mixer to mix uniformly, control the molar ratio of the total ions of nickel, iron and manganese in the modified layered oxide precursor F to sodium ions to be 1:0.96, sinter in an atmosphere furnace at 800℃ for 10h, and naturally cool to room temperature to obtain the modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

[0041] Comparative Example 2: 1. Preparation of the layered oxide precursor: Under the inert gas atmosphere, continuously add the nickel-iron-manganese mixed salt solution, the precipitating agent and the ammonia water into the reaction bottom liquid, control the pH value to be 11.5±0.6, the NH3 content to be 4.0±0.5g / L and the temperature to be 50℃, the flow rate of the nickel-iron-manganese mixed salt solution to be 350L / h, and react for 5-6h to obtain the reaction liquid C containing the layered oxide precursor, the particle size in the system being 6-8μm; The preparation process of the reaction bottom liquid is as follows: Into a closed synthesis reactor, add 2500L of the aqueous solution of Na2S2O3 with a mass concentration of 0.01wt%, add the ammonia water to make the NH3 content to be 4.0±0.5g / L, add the aqueous solution of NaOH to make the OH - content to be 1-3g / L, control the temperature of the reactor to be 50℃, and pass nitrogen gas for 2h, the flow rate of the nitrogen gas being 4.5±0.5m 3 / h, the reaction atmosphere in the displacement synthesis reaction kettle is inert gas.

[0042] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0043] The preparation process of the precipitant is as follows: A NaOH aqueous solution with a mass concentration of 25wt% is configured, and Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0044] 2. Wet coating of layered oxide precursor: 1) The layered aluminum phosphate AIP prepared in Preparation Example 1 is put into the reaction liquid C, and the weight ratio of the layered aluminum phosphate AIP to the solids in the reaction liquid C is controlled to be 1.2:10. A NaOH aqueous solution with a mass concentration of 25wt% is continuously added, and the pH value is controlled to be 11.5±0.6 and the temperature is controlled to be 50℃. The stirring reaction is carried out at 40-50r / min for 1.5-2h to obtain a reaction liquid D; 2) The reaction liquid D is washed and pressure-filtered, and the filter cake E is obtained by dehydration with a solid-liquid separation device. The washing liquid used in the washing and pressure filtration in S302 is a NaOH aqueous solution with a mass concentration of 2wt% and deionized water. The NaOH aqueous solution is used to wash part of the metal impurities and S impurities, and the deionized water is used to wash the impurity Na at a temperature range of 50±5℃. 3) The filter cake E is put into a tray dryer, and the drying temperature range is 120±5℃. The water content of the qualified powder after discharging from the tray dryer is controlled to be <0.5%, and a modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained, which has a particle size of 10-13μm and a large number of wrinkles on the surface, indicating that the loading of the layered aluminum phosphate fragments is successful. 3. Preparation of modified layered oxide: The modified layered oxide precursor F and sodium carbonate are uniformly mixed in a mixer, and the molar ratio of the total ions of nickel, iron and manganese in the modified layered oxide precursor F to sodium ions is controlled to be 1:0.96. Sintering is carried out at 800℃ in an atmosphere furnace for 10h, and natural cooling is carried out to room temperature to obtain a modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

[0045] Comparative Example 3: 1. Preparation of layered oxide precursor: The nickel-iron-manganese mixed salt solution, the precipitant and ammonia water are continuously added into the reaction bottom liquid under inert gas atmosphere, the pH value is controlled to be 11.5±0.6, the NH3 content is controlled to be 4.0±0.5 g / L, the temperature is controlled to be 50℃, the flow rate of the nickel-iron-manganese mixed salt solution is controlled to be 350 L / h, the reaction is carried out for 5-6 h, and a reaction liquid C containing the layered oxide precursor is obtained, and the particle size in the system is 6-8 μm; The preparation process of the reaction bottom liquid is as follows: The 2500 L Na2S2O3 aqueous solution with a mass concentration of 0.01 wt% is added into the closed synthesis reaction kettle, the ammonia water is added to make the NH3 content be 4.0±0.5 g / L, the NaOH aqueous solution is added to make the OH - The content is 1-3 g / L, the temperature of the reaction kettle is controlled to be 50℃, the nitrogen gas is introduced for 2 h, the flow rate of the nitrogen gas is 4.5±0.5 m 3 / h, and the reaction atmosphere in the synthesis reaction kettle is replaced to be inert gas atmosphere.

[0046] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0047] The preparation process of the precipitant is as follows: The Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0048] 2. Wet coating of the layered oxide precursor: 1) The colloidal solution B of the preparation example 1 is added into the reaction liquid C, the weight ratio of the solid in the colloidal solution B to the solid in the reaction liquid C is controlled to be 0.7:10, the NaOH aqueous solution with a mass concentration of 25 wt% is continuously added, the pH value is controlled to be 11.5±0.6, the temperature is controlled to be 50℃, the stirring is carried out at 40-50 r / min, and the reaction is carried out for 1.5-2 h to obtain a reaction liquid D; 2) The reaction liquid D is washed and pressure-filtered, the filter cake E is obtained by dehydration with a solid-liquid separation device; the washing liquid used in the washing and pressure filtration in S302 is the NaOH aqueous solution with a mass concentration of 2 wt% and deionized water, the NaOH aqueous solution is used to wash part of metal impurities and S impurities, and the deionized water is used to wash the impurity Na at a temperature of 50±5℃; 3) The filter cake E is added into a tray dryer, the drying temperature is controlled to be 120±5℃, the water content of the qualified powder after the discharge of the tray dryer is controlled to be less than 0.5%, and a modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained, the particle size of the modified layered oxide precursor F is 10-13 μm, and the surface has a large number of wrinkles, which indicates that the loading of the layered aluminum phosphate fragments is successful. 3. Preparation of modified layered oxide: The modified layered oxide precursor F and sodium carbonate were placed in a mixer and mixed uniformly, the molar ratio of total ions of nickel, iron and manganese to sodium ions in the modified layered oxide precursor F was controlled to be 1:0.96, sintering at 800℃ in an atmosphere furnace for 10h, and naturally cooled to room temperature to obtain the modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O3 11 .

[0049] Comparative Example 4: 1. Preparation of layered oxide precursor: The nickel-iron-manganese mixed salt solution, precipitant and ammonia water were continuously added in the reaction bottom liquid under inert gas atmosphere, the pH value was controlled to be 11.5±0.6, the NH3 content was 4.0±0.5g / L, the temperature was 50℃, the flow rate of nickel-iron-manganese mixed salt solution was 350L / h, and the reaction time was 5-6h to obtain the reaction liquid C containing layered oxide precursor, and the particle size in the system was 6-8μm; The preparation process of the reaction bottom liquid was as follows: A 2500L Na2S2O3 aqueous solution with a mass concentration of 0.01wt% was added into a closed synthesis reactor, ammonia water was added to make the NH3 content 4.0±0.5g / L, NaOH aqueous solution was added to make the OH - content 1-3g / L, the temperature of the reactor was controlled to be 50℃, nitrogen gas was introduced for 2h, the flow rate of nitrogen gas was 4.5±0.5m 3 / h, and the reaction atmosphere in the synthesis reactor was replaced to be inert atmosphere.

[0050] The preparation process of the nickel-iron-manganese mixed salt solution was as follows: The soluble salts of nickel, iron and manganese were configured into a mixed salt solution with a total molar concentration of 2mol / L, and the molar ratio of nickel, iron and manganese was controlled to be 3:4:3.

[0051] The preparation process of the precipitant was as follows: A NaOH aqueous solution with a mass concentration of 25wt% was configured, and Na2S2O3 was dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution was 0.01%.

[0052] 2. Wet coating of layered oxide precursor: 1) The colloidal solution B of Preparation Example 1 is added into the reaction liquid C, the weight ratio of the solid in the colloidal solution B to the solid in the reaction liquid C is controlled to be 2:10, the mass concentration of the NaOH aqueous solution continuously added is 25wt%, the pH value is controlled to be 11.5±0.6, the temperature is controlled to be 50℃, the stirring speed is 40-50r / min, and the reaction is carried out for 1.5-2h to obtain a reaction liquid D; 2) The reaction liquid D is subjected to washing and pressure filtration, and is dehydrated by using a solid-liquid separation device to obtain a filter cake E; the washing liquid used in the washing and pressure filtration in S302 is a NaOH aqueous solution with a mass concentration of 2wt% and deionized water, the NaOH aqueous solution is used to wash part of metal impurities and S impurities, and the deionized water is used to wash the impurity Na; 3) The filter cake E is put into a tray dryer, the drying temperature range is 120±5℃, the water content of the qualified powder after the discharge of the tray dryer is controlled to be less than 0.5%, and a modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained, the particle size of the modified layered oxide precursor F is 10-13μm, and the surface has a large number of wrinkles, which indicates that the loading of the layered aluminum phosphate fragments is successful; 3. Preparation of the modified layered oxide: The modified layered oxide precursor F and sodium carbonate are mixed uniformly in a mixer, the molar ratio of the total ions of nickel, iron and manganese in the modified layered oxide precursor F to sodium ions is controlled to be 1:0.96, and the mixture is sintered in an atmosphere furnace at 800℃ for 10h, and then naturally cooled to room temperature to obtain the modified layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

[0053] Comparative Example 5: 1. Preparation of the layered oxide precursor: 1) The nickel-iron-manganese mixed salt solution, the precipitating agent and ammonia water are continuously added into the reaction bottom liquid under an inert gas atmosphere, the pH value is controlled to be 11.5±0.6, the NH3 content is controlled to be 4.0±0.5g / L, the temperature is controlled to be 50℃, the flow rate of the nickel-iron-manganese mixed salt solution is 350L / h, and the reaction is carried out for 5-6h to obtain a reaction liquid C containing a layered oxide precursor, and the particle size in the system is 6-8μm; The preparation process of the reaction bottom liquid is as follows: Into a closed synthesis reactor, 2500L of an aqueous solution containing Na2S2O3 with a mass concentration of 0.01wt% is added, ammonia water is added to make the NH3 content be 4.0±0.5g / L, an NaOH aqueous solution is added to make the OH - content be 1-3g / L, the temperature of the reactor is controlled to be 50℃, nitrogen gas is introduced for 2h, the flow rate of the nitrogen gas is 4.5±0.5m 3 / h, the reaction atmosphere in the displacement synthesis reaction kettle is inert gas.

[0054] The preparation process of the nickel-iron-manganese mixed salt solution is as follows: The soluble salts of nickel, iron and manganese are configured into a mixed salt solution with a total molar concentration of 2 mol / L, and the molar ratio of nickel, iron and manganese is controlled to be 3:4:3.

[0055] The preparation process of the precipitant is as follows: A NaOH aqueous solution with a mass concentration of 25wt% is configured, and Na2S2O3 is dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution is 0.01%.

[0056] 2) The reaction liquid C is washed and pressure-filtered, and a filter cake E is obtained by dehydration with a solid-liquid separation device; the washing liquid used in the washing and pressure filtration in S302 is a NaOH aqueous solution with a mass concentration of 2wt% and deionized water, and the temperature range is 50±5℃, the NaOH aqueous solution is used to wash part of metal impurities and S impurities, and the deionized water is used to wash impurities Na; 3) The filter cake E is put into a tray dryer, the drying temperature range is 120±5℃, the water content of the qualified powder after discharging from the tray dryer is controlled to be less than 0.5%, and a layered oxide precursor is obtained; 3. Preparation of modified layered oxide: The layered oxide precursor and sodium carbonate are mixed uniformly in a mixer, the molar ratio of total ions of nickel, iron and manganese in the layered oxide precursor to sodium ions is controlled to be 1:0.96, and sintering is carried out at 800℃ in an atmosphere furnace for 10h, and then natural cooling is carried out to room temperature, to obtain a layered oxide: Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2.

[0057] III. Preparation of batteries and performance test: 1. Battery preparation: The positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-5 are used as active substances, mixed according to the mass ratio of active substance: SP: PVDF = 90:5:5, added with NMP to form a viscous glue liquid, coated on an aluminum foil, and baked in a vacuum drying oven at 120℃ for 12h to obtain a positive electrode sheet. A metal sodium sheet is used as a counter electrode, glass fiber (Waterman) is used as a separator, 1mol / L NaPF6EC / DMC=1:1 (Alfa) is used as an electrolyte, and a 2032 button cell is assembled in an Ar protection glove box.

[0058] 2. Performance test The batteries were tested in the voltage range of 2.5-4.0 V, and the first-week specific capacity, 50-week specific capacity, 100-week specific capacity, 150-week specific capacity, 200-week specific capacity, 250-week specific capacity and 300-week specific capacity of each battery were simply tested at 1C, and the test cycle capacity curve is shown in Figure 1 .

[0059] As can be seen from Figure 1 , the first-week specific capacity of Example 2 is 126.1 mAh / g, the 300-week capacity retention rate is 66.1%, and the working voltage interval is 2-4.3 V; By comparing Comparative Examples 1-2 and Example 2, it can be seen that the unbroken layered aluminum phosphate may not be completely coated in the mixing with the precursor, so that the specific capacity and capacity stability are greatly reduced; By comparing Comparative Examples 3-4 and Example 2, it can be seen that as the content of the layered aluminum phosphate fragments increases, the first-week specific capacity is improved, which may be due to the higher Na content of the phosphatized material; but too high a dosage of the layered aluminum phosphate fragments may cause excessive acidity during sintering, which greatly challenges the stability of the layered oxide.

[0060] By comparing Examples 1-3 with Comparative Example 5, the specific capacity and stability of the modified layered oxide Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 are much higher than those of the layered oxide Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2, which proves the feasibility of the modification, and the obtained sodium-ion battery layered positive electrode material has the characteristics of low residual alkali content and high cycle capacity retention rate.

[0061] Test design description: Since the present application mainly verifies the influence of the layered aluminum phosphate fragments coated layered oxide precursor on the performance of the subsequent modified layered oxide, the most conventional reagent ratio is adopted, but other skilled persons in the technical field should be considered as infringing the protection scope of the present application if they adopt the concept of the present application of the layered aluminum phosphate fragments coated layered oxide precursor.

[0062] The above description is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the technical field, according to the technical solution and the inventive concept of the present application, can make equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, The method comprises the following steps: S1, preparation of layered aluminum phosphate fragments: S101, preparation of layered aluminum phosphate: 2.0g of aluminum isopropoxide was added into 16.0mL of sec-butyl alcohol, 4.8mL of 4-methylpyridine was added under stirring, and finally 2.72mL of 85wt% phosphoric acid aqueous solution was added, and the mixture was put into a reaction kettle after forming a gel, and was crystallized at 160℃ for 12 days, and the product was filtered, washed, and dried in air to obtain layered aluminum phosphate AIP; S102, exfoliation of layered aluminum phosphate: The layered aluminum phosphate AIP was dissolved in a solution with a solute of water-alcohol mixture and a butylamine amount of 10mmol / g AIP at room temperature, and a reaction liquid A was obtained after reacting for 3 days; S103, breaking of layered aluminum phosphate: The reaction liquid A was directly ground by using a grinding crusher, and a yellowish white colloidal solution B which was difficult to settle was obtained after grinding, the solid content of the layered aluminum phosphate fragments in the solution was 35.6%, and the edge length of the layered aluminum phosphate fragments was 1.1-1.6μm; S2, preparation of layered oxide precursor: A nickel-iron-manganese mixed salt solution, a precipitating agent and ammonia water were continuously added into a reaction bottom liquid under an inert gas atmosphere, the pH value was controlled to be 11.5±0.6, the NH3 content was controlled to be 4.0±0.5g / L, the temperature was controlled to be 50℃, the nickel-iron-manganese mixed salt solution flow rate was controlled to be 350L / h, and the reaction was carried out for 5-6h to obtain a reaction liquid C containing layered oxide precursor, and the particle size in the system was 6-8μm; S3, wet coating of layered oxide precursor: S301, the colloidal solution B was put into the reaction liquid C, a 25wt% NaOH aqueous solution was continuously added, the pH value was controlled to be 11.5±0.6 and the temperature was controlled to be 50℃, and the reaction was carried out under stirring at 40-50r / min for 1.5-2h to obtain a reaction liquid D; S302, the reaction liquid D was washed and pressure-filtered, and a filter cake E was obtained by dehydration by using a solid-liquid separation device; S303, the filter cake E was put into a tray dryer, the drying temperature range was 120±5℃, the water content of the qualified powder after discharging of the tray dryer was controlled to be less than 0.5%, and a modified layered oxide precursor F coated with layered aluminum phosphate fragments was obtained, the particle size of the modified layered oxide precursor F was 10-13μm, and the surface of the modified layered oxide precursor F had a large number of wrinkles; S4, preparation of modified layered oxide: The modified layered oxide precursor F and sodium carbonate were uniformly mixed in a mixer, and were sintered at 800℃ in an atmosphere furnace for 10h, and were naturally cooled to room temperature to obtain a modified layered oxide.

2. The method of claim 1, wherein the sodium-ion battery cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion battery cathode material; (2) mixing the precursor with a sodium source; and (3) annealing the mixture of the precursor and the sodium source. In the S102, the volume ratio of water to ethanol in the water-alcohol mixture was 3:

1.

3. The method of claim 1, wherein the sodium-ion battery cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion battery cathode material; (2) mixing the precursor with a sodium source; and (3) annealing the mixture of the precursor and the sodium source. The preparation process of the reaction bottom liquid in the S2 is as follows: Into a closed synthesis reactor, 2500 L of 0.01 wt% Na2S2O3 aqueous solution was added, ammonia water was added to make the NH3 content 4.0±0.5 g / L, and NaOH aqueous solution was added to make the OH - content 1-3 g / L, the temperature of the reactor was controlled at 50°C, nitrogen was introduced at a flow rate of 4.5±0.5 m 3 / h for 2 h, and the reaction atmosphere in the synthesis reactor was replaced with inert gas.

4. The method of claim 1, wherein the sodium-ion battery cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion battery cathode material; (2) mixing the precursor with a sodium source; and (3) annealing the mixture of the precursor and the sodium source. The preparation process of the nickel-iron-manganese mixed salt solution in the S2 is as follows: Soluble salts of nickel, iron and manganese were configured into a mixed salt solution with a total molar concentration of 2mol / L, and the molar ratio of nickel, iron and manganese was controlled to be 3:4:

3.

5. The method of claim 1, wherein the sodium-ion battery cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion battery cathode material; (2) mixing the precursor with a sodium source; and (3) annealing the mixture of the precursor and the sodium source. The preparation process of the precipitating agent in the S2 is as follows: A 25wt% NaOH aqueous solution was configured, Na2S2O3 was dissolved in the NaOH aqueous solution, and the mass ratio of Na2S2O3 in the NaOH aqueous solution was 0.01%.

6. The method for preparing a sodium-ion battery cathode material according to claim 1, characterized in that, In the S301, the weight ratio of the solid in the colloidal solution B to the solid in the reaction solution C is 1-1.5:

10.

7. The method for preparing a sodium-ion battery cathode material according to claim 1, characterized in that, In the S302, the washing liquid used in the washing and pressure filtration is a 2wt% NaOH aqueous solution and deionized water, and at a temperature of 50±5℃, the NaOH aqueous solution is used to wash part of the metal impurities and S impurities, and the deionized water is used to wash the impurity Na.

8. The method for preparing a sodium-ion battery cathode material according to claim 1, characterized in that, The modified layered oxide precursor F of S303 is subjected to sintering test, the steps are: the modified layered oxide precursor F is sintered at 800℃ in an atmosphere furnace for 10h, and naturally cooled to room temperature to obtain layered oxide @Al2P3O 11 The aggregate of the modified layered oxide precursor F before sintering and the aggregate of the layered oxide @Al2P3O 11 The change of the surface wrinkle of the aggregate.

9. The method for preparing a sodium-ion battery cathode material according to claim 1, characterized in that, In the S4, the molar ratio of total ions of nickel, iron and manganese to sodium ions in the modified layered oxide precursor F is 1:0.96, and the modified layered oxide is Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 .

10. A sodium-ion battery cathode material based on aluminum phosphate modification, characterized in that, The preparation method of any one of claims 1-9.

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