Sodium-ion battery cathode material based on aluminum phosphate modification and preparation method thereof

Abstract

The application discloses a sodium ion battery positive electrode material based on aluminum phosphate modification and a preparation method thereof, and 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, and preparation of a modified layered oxide, etc. The application firstly adopts the layered aluminum phosphate to wetly coat the layered oxide precursor, forms a petal-shaped crystal aggregate, and then utilizes the destruction of the layered structure of the layered aluminum phosphate in a sintering process and the change of the precursor from a spherical shape to a layered structure to prepare a modified layered oxide with an aluminum phosphate coating on the surface, so that the modified layered oxide has the characteristics of long-acting inhibition of surface residual alkali and high stability, and the prepared battery has higher specific capacity and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of new energy battery materials technology, and in particular to sodium-ion battery cathode materials based on aluminum phosphate modification and their preparation methods. Background Technology

[0002] Sodium-ion batteries, as a novel energy storage technology, have gradually become a research hotspot due to their advantages such as low cost and abundant resources. The cathode material, as the core component of a sodium-ion battery, directly affects the overall performance of the battery. Cathode materials for sodium-ion batteries mainly include layered oxides, Prussian blue, and polyanionic materials. Among them, layered oxides are considered a promising high-energy-density sodium-ion battery cathode material due to their high theoretical capacity and high air stability.

[0003] Layered metal oxides are generally prepared using solid-state or co-precipitation methods with precursors. Solid-state methods are simple and low-cost, but careful attention must be paid to material uniformity and control of residual alkali on the surface. Co-precipitation methods prepare precursors by reacting metal salt solutions with sodium hydroxide and ammonia, followed by high-temperature calcination to obtain the cathode material, which has relatively better performance. Currently, copper-based cathodes are mostly prepared using solid-state methods, while nickel-based cathodes are mainly prepared using co-precipitation methods.

[0004] However, in practical applications, layered oxide cathode materials still have some problems. For example, when charged to above 4.0V, a large-volume phase transition from P2 to O2 and irreversible oxygen release occur, leading to a rapid decay of battery capacity and voltage. In addition, below 4.0V, the ordered rearrangement of different sodium ions / vacancies and the rearrangement of transition metals reduce the sodium ion diffusion kinetics, resulting in unsatisfactory rate performance of the electrode material at high current densities. But the bigger problem is the residual alkali problem of layered oxides.

[0005] The residual alkali on the surface of layered oxides makes them highly sensitive to air, severely hindering their practical application. During high-temperature calcination in the presence of air, highly reactive Na+ is generated on their surface. + As the calcination time increases, Na + These ions penetrate the bulk phase and combine with interlayer oxygen atoms to form layered oxides. During subsequent natural cooling and electrochemical cycling, these ions gradually lose their activity and react with atmospheric carbon dioxide and oxygen to form amorphous sodium carbonate, or residual alkali, on the particle surface. Residual alkali causes the cathode material slurry to undergo a sol-gel transition, complicating the coating process and reducing the material's electrochemical performance. The remaining sodium reacts with the electrolyte to produce gas, causing the battery to swell and posing a significant safety hazard.

[0006] Currently, the modification of layered oxides mainly includes the modification of precursors and secondary modification by coating of layered oxides. However, in actual use, once the battery is packaged, the stability of the modification or coating is difficult to guarantee for a long time and still needs further improvement. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies by coating the precursor with layered aluminum phosphate and then utilizing the destruction of the layered structure of the aluminum phosphate and the change of the precursor from a spherical to a layered structure during sintering to prepare a modified layered oxide with aluminum phosphate (weakly acidic) coating on the surface. This modified oxide has the characteristic of long-term inhibition of surface residual alkali. In other words, this invention proposes a sodium-ion battery cathode material based on aluminum phosphate modification and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention first proposes a method for preparing a sodium-ion battery cathode material, comprising the following steps:

[0010] S1. Preparation of layered aluminum phosphate fragments:

[0011] S101, Preparation of layered aluminum phosphate:

[0012] 2.0 g of aluminum isopropoxide was added to 16.0 mL of sec-butanol, followed by the addition of 4.8 mL of 4-methylpyridine under stirring. Finally, 2.72 mL of an 85 wt% aqueous phosphoric acid solution was added. After gel formation, the mixture was transferred to a reaction vessel and crystallized at 160 °C for 12 days. The product was filtered, washed, and dried in air to obtain layered aluminum phosphate AIP ([Al₂P₃O₄]₂). 10 (OH)₂][C₆NH₈]);

[0013] S102, peeling of layered aluminum phosphate:

[0014] At room temperature, layered aluminum phosphate (AIP) was dissolved in a solution containing a water-alcohol mixture and 10 mmol / g butylamine. After reacting for 3 days, reaction solution A was obtained.

[0015] Before the reaction, the AIP had a regular planar layered structure (about 10 μm). During the exfoliation process, some of the Al-OP bonds on the layers were hydrolyzed and broken into Al-OH and P-OH bonds. The large layers formed small plate-like particles (<1 μm). After the alkylamines were inserted, new crystals were formed, which had a very different morphology from the AIP crystals before the reaction. They were petal-shaped crystal aggregates (about 5 μm). This morphological change was mainly due to the fact that layered crystals mostly adopt an edge-to-edge aggregation mode during the growth process. Similar phenomena also occur in other layered materials.

[0016] S103, Crushing of layered aluminum phosphate:

[0017] The reaction solution A was directly ground using a grinding and crushing machine. The original reaction solution was a mixed system that was easy to settle and had solid-liquid separation. After grinding, a pale yellow-white colloidal solution B was obtained that was difficult to settle. The solid content of the layered aluminum phosphate fragments in the solution was 35.6%, and the side length of the layered aluminum phosphate fragments was 1.1-1.6 μm.

[0018] S2. Preparation of layered oxide precursors:

[0019] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0020] S3. Wet coating of layered oxide precursors:

[0021] S301. Colloidal solution B is added to reaction solution C, and a 25wt% NaOH aqueous solution is continuously added. The pH value is controlled at 11.5±0.6 and the temperature is 50℃. The mixture is stirred at 40-50r / min for 1.5-2h to obtain reaction solution D.

[0022] S302. Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E;

[0023] S303. The filter cake E is fed into a disc dryer, and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. A modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0024] S4. Preparation of modified layered oxides:

[0025] The modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer and sintered in an atmosphere furnace at 800℃ for 10 hours. After natural cooling to room temperature, the modified layered oxide was obtained.

[0026] Preferably, in S102, the volume ratio of water to ethanol in the water-ethanol mixture is 3:1.

[0027] Preferably, the grinding and crushing machine in S103 is a Yubang small grinding and pulverizing machine with an inner cavity made of 316 stainless steel and a grinding speed of 30 r / min. Low-speed grinding avoids premature granulation or spheroidization of the layered structure.

[0028] Preferably, the preparation process of the reaction base solution in S2 is as follows:

[0029] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0030] Preferably, the preparation process of the nickel-iron-manganese mixed salt solution in S2 is as follows:

[0031] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0032] Preferably, the preparation process of the precipitant in S2 is as follows:

[0033] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0034] Preferably, in S301, the weight ratio of solid in colloidal solution B to solid in reaction solution C is controlled to be 1-1.5:10. Layered aluminum phosphate fragments are used to coat the layered oxide precursor. When the content is too low, the coating is incomplete. When the content is too high, the coating is too dense, causing the folds to fold together, which may affect the subsequent sintering reaction with the Na source. At the same time, excessive unprecipitated nickel, iron, and manganese continue to precipitate or adsorb in the folds.

[0035] Preferably, the washing solution used for washing the filter press in S302 is a 2wt% NaOH aqueous solution and deionized water. The NaOH aqueous solution is used to wash some of the metal impurities and S impurities, and the deionized water is used to wash the Na impurities.

[0036] Preferably, in S4, the molar ratio of total nickel, iron, and manganese ions 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 ;

[0037] Based on previous research and experiments, the modified layered oxide precursor F of S3O3 was subjected to sintering tests. The steps were as follows: the modified layered oxide precursor F was sintered in an atmosphere furnace at 800℃ for 10 hours, and then naturally cooled to room temperature to obtain the layered oxide @Al2P3O 11 Aggregates were analyzed by SEM to compare the modified layered oxide precursor F before sintering with the layered oxide @Al2P3O after sintering. 11 Changes in the surface wrinkling of aggregates. When the temperature exceeds 400°C, the layered structure of layered aluminum phosphate is destroyed, forming dispersed particles that adhere to the surface of the layered oxide precursor and form an aluminum phosphate film, which facilitates the shuttle of Na ions. Furthermore, after the organic amine is evaporated, amphoteric passivated alumina and acidic phosphorus oxide are produced, which can significantly reduce the residual alkali on the surface of the layered oxide.

[0038] The present invention also proposes a layered cathode material for sodium-ion batteries based on aluminum phosphate modification prepared by the aforementioned preparation method, which has the characteristics of low residual alkali content and high cycle capacity retention.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention uses a wet coating process to coat layered aluminum phosphate fragments onto the surface of a layered oxide precursor, forming a petal-shaped crystalline aggregate. During the high-temperature sintering process (>400℃), the layered structure of the aluminum phosphate fragments will spontaneously break down, forming dispersed particles that adhere to the surface of the layered oxide precursor and form an aluminum phosphate film, which is beneficial for Na ion shuttle, thereby improving the electrochemical performance of the material.

[0041] 2. The novel modified layered oxide precursor F prepared in this invention has layered aluminum phosphate fragments coated on its surface that, after high-temperature sintering, generate amphoteric passivated aluminum oxide and acidic phosphorus oxide. These substances can react with the residual alkali on the surface of the layered oxide, thereby reducing the amount of residual alkali on the surface and improving the stability and cycle performance of the cathode material.

[0042] 3. In addition, the present invention utilizes aluminum phosphate particles transformed from layered aluminum phosphate fragments to effectively suppress structural changes of layered oxides during charge and discharge processes, reduce the occurrence of irreversible phase transitions, and thus improve the cycle stability of the material. Attached Figure Description

[0043] Figure 1 A cycle capacity test curve of a battery prepared with the cathode material of the present invention;

[0044] Figure 2 This is a SEM image of the modified layered oxide precursor F prepared in Example 2 of the present invention;

[0045] Figure 3A specially prepared layered oxide @Al2P3O for Example 2 of this invention 11 SEM image of the aggregate. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0047] I. Preparation of layered aluminum phosphate fragments:

[0048] Preparation Example 1:

[0049] Preparation of layered aluminum phosphate fragments:

[0050] References: Study on exfoliation and embedding of microporous layered aluminum phosphate materials, Huang Qiong et al., Journal of Chemical Research of Chinese Universities, November 2004, 25-11: 2065-2069;

[0051] S101, Preparation of layered aluminum phosphate:

[0052] 2.0 g of aluminum isopropoxide was added to 16.0 mL of sec-butanol, followed by the addition of 4.8 mL of 4-methylpyridine under stirring. Finally, 2.72 mL of an 85 wt% aqueous phosphoric acid solution was added. After gel formation, the mixture was transferred to a reaction vessel and crystallized at 160 °C for 12 days. The product was filtered, washed, and dried in air to obtain layered aluminum phosphate AIP ([Al₂P₃O₄]₂). 10 (OH)₂][C₆NH₈]);

[0053] S102, peeling of layered aluminum phosphate:

[0054] At room temperature, layered aluminum phosphate (AIP) was dissolved in a solution containing a water-alcohol mixture and 10 mmol / g butylamine. After reacting for 3 days, reaction solution A was obtained.

[0055] Before the reaction, the AIP had a regular planar layered structure (about 10 μm). During the exfoliation process, some of the Al-OP bonds on the layers were hydrolyzed and broken into Al-OH and P-OH bonds. The large layers formed small plate-like particles (<1 μm). After the alkylamines were inserted, new crystals were formed, which had a very different morphology from the AIP crystals before the reaction. They were petal-shaped crystal aggregates (about 5 μm). This morphological change was mainly due to the fact that layered crystals mostly adopt an edge-to-edge aggregation mode during the growth process. Similar phenomena also occur in other layered materials.

[0056] S103, Crushing of layered aluminum phosphate:

[0057] The reaction solution A was directly ground using a grinding and crushing machine. The original reaction solution was a mixed system that was easy to settle and had solid-liquid separation. After grinding, a pale yellow-white colloidal solution B was obtained that was difficult to settle. The solid content of the layered aluminum phosphate fragments in the solution was 35.6%, and the side length of the layered aluminum phosphate fragments was 1.1-1.6 μm.

[0058] In S102, the volume ratio of water to ethanol in the water-ethanol mixture is 3:1;

[0059] The grinding and crushing machine in S103 is a Yubang small grinding and pulverizing machine with an inner cavity made of 316 stainless steel. The grinding speed is 30r / min, and the low-speed grinding avoids premature granulation or spheroidization of the layered structure.

[0060] II. Synthesis of a layered cathode material for sodium-ion batteries:

[0061] Example 1:

[0062] 1. Preparation of layered oxide precursors:

[0063] Partially referencing Chinese Patent CN 119461515 A, a nickel-iron-manganese layered oxide precursor, its preparation method, and its application:

[0064] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0065] The preparation process of the reaction substrate is as follows:

[0066] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0067] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0068] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0069] The preparation process of the precipitant is as follows:

[0070] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0071] 2. Wet coating of layered oxide precursors:

[0072] 1) The colloidal solution B of Preparation Example 1 was added to the reaction solution C, and the weight ratio of solid in colloidal solution B to solid in reaction solution C was controlled to be 1:10. NaOH aqueous solution with a mass concentration of 25wt% was continuously added, and the pH value was controlled to be 11.5±0.6 and the temperature to be 50℃. The reaction was stirred at 40-50r / min for 1.5-2h to obtain reaction solution D.

[0073] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0074] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0075] 3. Preparation of modified layered oxides:

[0076] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0077] Example 2:

[0078] 1. Preparation of layered oxide precursors:

[0079] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0080] The preparation process of the reaction substrate is as follows:

[0081] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0082] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0083] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0084] The preparation process of the precipitant is as follows:

[0085] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0086] 2. Wet coating of layered oxide precursors:

[0087] 1) The colloidal solution B of Preparation Example 1 was added to the reaction solution C, and the weight ratio of solid in colloidal solution B to solid in reaction solution C was controlled at 1.2:10. NaOH aqueous solution with a mass concentration of 25wt% was continuously added, and the pH value was controlled at 11.5±0.6 and the temperature at 50℃. The reaction was stirred at 40-50 r / min for 1.5-2 h to obtain reaction solution D.

[0088] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0089] 3) Feed the filter cake E into a disc dryer, dry at a temperature range of 120±5℃, and control the moisture content of the qualified powder after discharge from the disc dryer to be <0.5%, thus obtaining a modified layered oxide precursor F coated with layered aluminum phosphate fragments. Its particle size is 10-13 μm, and its surface has numerous wrinkles, indicating successful loading of the layered aluminum phosphate fragments. (Refer to...) Figure 2 (The modified layered oxide precursor F is approximately 12.8 μm).

[0090] The modified layered oxide precursor F was sintered in an atmosphere furnace at 800℃ for 10 h and then naturally cooled to room temperature to obtain the layered oxide @Al2P3O. 11 Aggregates, such as Figure 3 As shown, the particle size of each sphere is approximately 11.9-12.4 μm. The original aluminum phosphate wrinkles covering the outer wall of the oxide spheres have disappeared, and the surface is covered with reticulated stripes (possibly phosphorus oxide or aluminum phosphorus compound) and spherical small particles (possibly aluminum oxide). Both of these have the function of removing residual alkali on the surface, thereby improving battery efficiency.

[0091] 3. Preparation of modified layered oxides:

[0092] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0093] Example 3:

[0094] 1. Preparation of layered oxide precursors:

[0095] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0096] The preparation process of the reaction substrate is as follows:

[0097] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... -The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0098] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0099] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0100] The preparation process of the precipitant is as follows:

[0101] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0102] 2. Wet coating of layered oxide precursors:

[0103] 1) The colloidal solution B of Preparation Example 1 was added to the reaction solution C, and the weight ratio of solid in colloidal solution B to solid in reaction solution C was controlled at 1.5:10. NaOH aqueous solution with a mass concentration of 25wt% was continuously added, and the pH value was controlled at 11.5±0.6 and the temperature at 50℃. The reaction was stirred at 40-50 r / min for 1.5-2 h to obtain reaction solution D.

[0104] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0105] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0106] 3. Preparation of modified layered oxides:

[0107] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, and then naturally cooled to room temperature to obtain the modified layered oxide: Na. 0.96 Ni 0.3 Fe0.4 Mn 0.3 O2@Al2P3O 11 .

[0108] Comparative Example 1:

[0109] 1. Preparation of layered oxide precursors:

[0110] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0111] The preparation process of the reaction substrate is as follows:

[0112] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0113] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0114] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0115] The preparation process of the precipitant is as follows:

[0116] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0117] 2. Wet coating of layered oxide precursors:

[0118] 1) Add reaction solution A of Preparation Example 1 to reaction solution C, control the weight ratio of solid in reaction solution A to solid in reaction solution C to be 1.2:10, continuously add 25wt% NaOH aqueous solution, 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 reaction solution D;

[0119] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0120] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0121] 3. Preparation of modified layered oxides:

[0122] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0123] Comparative Example 2:

[0124] 1. Preparation of layered oxide precursors:

[0125] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0126] The preparation process of the reaction substrate is as follows:

[0127] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0128] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0129] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0130] The preparation process of the precipitant is as follows:

[0131] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0132] 2. Wet coating of layered oxide precursors:

[0133] 1) The layered aluminum phosphate AIP of Preparation Example 1 was added to the reaction solution C, and the weight ratio of layered aluminum phosphate AIP to the solid in the reaction solution C was controlled to be 1.2:10. A 25wt% NaOH aqueous solution was continuously added, and the pH value was controlled to be 11.5±0.6 and the temperature to be 50℃. The reaction was stirred at 40-50 r / min for 1.5-2 h to obtain the reaction solution D.

[0134] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0135] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0136] 3. Preparation of modified layered oxides:

[0137] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0138] Comparative Example 3:

[0139] 1. Preparation of layered oxide precursors:

[0140] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0141] The preparation process of the reaction substrate is as follows:

[0142] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0143] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0144] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0145] The preparation process of the precipitant is as follows:

[0146] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0147] 2. Wet coating of layered oxide precursors:

[0148] 1) The colloidal solution B of Preparation Example 1 was added to the reaction solution C, and the weight ratio of solid in colloidal solution B to solid in reaction solution C was controlled at 0.7:10. NaOH aqueous solution with a mass concentration of 25wt% was continuously added, and the pH value was controlled at 11.5±0.6 and the temperature at 50℃. The reaction was stirred at 40-50 r / min for 1.5-2 h to obtain reaction solution D.

[0149] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0150] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0151] 3. Preparation of modified layered oxides:

[0152] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0153] Comparative Example 4:

[0154] 1. Preparation of layered oxide precursors:

[0155] Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0156] The preparation process of the reaction substrate is as follows:

[0157] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0158] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0159] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0160] The preparation process of the precipitant is as follows:

[0161] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0162] 2. Wet coating of layered oxide precursors:

[0163] 1) The colloidal solution B of Preparation Example 1 was added to the reaction solution C, and the weight ratio of solid in colloidal solution B to solid in reaction solution C was controlled to be 2:10. NaOH aqueous solution with a mass concentration of 25wt% was continuously added, and the pH value was controlled to be 11.5±0.6 and the temperature to be 50℃. The reaction was stirred at 40-50r / min for 1.5-2h to obtain reaction solution D.

[0164] 2) Wash and filter the reaction solution D, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0165] 3) The filter cake E is fed into a disc dryer and the drying temperature range is 120±5℃. The moisture content of the qualified powder after the disc dryer is controlled to be <0.5%. The modified layered oxide precursor F coated with layered aluminum phosphate fragments is obtained. Its particle size is 10-13μm and the surface has a lot of wrinkles, indicating that the loading of layered aluminum phosphate fragments is successful.

[0166] 3. Preparation of modified layered oxides:

[0167] Modified layered oxide precursor F and sodium carbonate were mixed evenly in a mixer, controlling the molar ratio of total nickel, iron, and manganese ions to sodium ions in the modified layered oxide precursor F to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours, 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 .

[0168] Comparative Example 5:

[0169] 1. Preparation of layered oxide precursors:

[0170] 1) Under an inert gas atmosphere, a mixed nickel-iron-manganese salt solution, a precipitant, and ammonia were continuously added to the reaction substrate. The pH value was controlled at 11.5±0.6, the NH3 content at 4.0±0.5 g / L, the temperature at 50℃, and the flow rate of the mixed nickel-iron-manganese salt solution at 350 L / h. The reaction was carried out for 5-6 h to obtain reaction solution C containing layered oxide precursors. The particle size in the system was 6-8 μm.

[0171] The preparation process of the reaction substrate is as follows:

[0172] Add 2500L of a 0.01wt% Na₂S₂O₃ aqueous solution to a sealed reaction vessel. Add ammonia to make the NH₃ content 4.0±0.5g / L, and add NaOH aqueous solution to make the OH⁻ content... - The concentration was 1-3 g / L. The reactor temperature was controlled at 50℃, and nitrogen gas was introduced for 2 hours at a flow rate of 4.5 ± 0.5 m³ / L. 3 / h, the reaction atmosphere inside the substitution synthesis reactor is an inert atmosphere.

[0173] The preparation process of the nickel-iron-manganese mixed salt solution is as follows:

[0174] A mixed salt solution with a total molar concentration of 2 mol / L was prepared using soluble salts of nickel, iron, and manganese, with the molar ratio of nickel, iron, and manganese controlled at 3:4:3.

[0175] The preparation process of the precipitant is as follows:

[0176] Prepare a 25wt% NaOH aqueous solution by dissolving Na2S2O3 in the NaOH aqueous solution, with the mass percentage of Na2S2O3 in the NaOH aqueous solution being 0.01%.

[0177] 2) Wash and filter the reaction solution C, and dehydrate it using a solid-liquid separation device to obtain filter cake E; the washing solution used for washing and filtration in S302 is a 2wt% NaOH aqueous solution and deionized water. At a temperature range of 50±5℃, some metal impurities and S impurities are washed with NaOH aqueous solution, and impurities Na are washed with deionized water.

[0178] 3) Feed the filter cake E into a disc dryer, dry at a temperature of 120±5℃, and control the moisture content of the qualified powder after the disc dryer discharge to be <0.5% to obtain the layered oxide precursor.

[0179] 3. Preparation of modified layered oxides:

[0180] The layered oxide precursor and sodium carbonate were mixed evenly in a mixer, and the molar ratio of total nickel, iron, and manganese ions to sodium ions in the layered oxide precursor was controlled to be 1:0.96. The mixture was sintered in an atmosphere furnace at 800℃ for 10 hours and then naturally cooled to room temperature to obtain the layered oxide: Na0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2.

[0181] III. Battery manufacturing and performance testing:

[0182] 1. Battery making:

[0183] The positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-5 were used as active materials. They were mixed at a mass ratio of active material:SP:PVDF of 90:5:5, and NMP was added to form a viscous adhesive. This adhesive was coated onto aluminum foil and baked in a vacuum drying oven at 120°C for 12 hours to obtain the positive electrode sheet. Using a sodium metal sheet as the counter electrode, Waterman glass fiber as the separator, and 1 mol / L NaPF6EC / DMC = 1:1 (Alfa) as the electrolyte, 2032 coin cells were assembled in an Ar protective glove box.

[0184] 2. Performance Testing

[0185] The batteries were tested within a voltage range of 2.5-4.0V. Simple tests were conducted at 1C to measure the specific capacity of each battery at the first, 50, 100, 150, 200, 250, and 300 cycles. The cycle capacity curves are shown below. Figure 1 As shown.

[0186] Depend on Figure 1 It can be seen that the specific capacity of Example 2 in the first week was 126.1 mAh / g, the capacity retention rate after 300 weeks was 66.1%, and the operating voltage range was 2V-4.3V;

[0187] Comparing Comparative Examples 1-2 and Example 2, the unbroken layered aluminum phosphate may not be completely coated when mixed with the precursor, thus significantly reducing the specific capacity and capacity stability.

[0188] Comparing Comparative Examples 3-4 and Example 2, the specific capacity in the first week increased with the increase in the content of layered aluminum phosphate fragments, possibly due to the higher sodium content of phosphorylated aluminum phosphate. However, excessive amounts of layered aluminum phosphate fragments may cause excessive acidity during sintering, which poses a significant challenge to the stability of the layered oxides.

[0189] By comparing Examples 1-3 with Comparative Example 5, the modified layered oxide Na 0.96 Ni 0.3 Fe 0.4 Mn 0.3 O2@Al2P3O 11 The specific capacity and stability are much higher than those of layered oxide Na. 0.96 Ni 0.3 Fe0.4 Mn 0.3 O2 was used to demonstrate the feasibility of this modification, and the resulting layered cathode material for sodium-ion batteries has the characteristics of low residual alkali content and high cycle capacity retention.

[0190] Experimental Design Notes: Since this invention mainly verifies the effect of coating layered oxide precursors with layered aluminum phosphate fragments on the performance of subsequently modified layered oxides, the most conventional reagent ratios are used. However, other personnel skilled in the art who use the inventive concept of coating layered oxide precursors with layered aluminum phosphate fragments should be considered to have infringed upon the scope of protection of this invention.

[0191] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

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 butylamine-containing water-alcohol mixed solution at room temperature, the content of butylamine was 10mmol / g relative to the layered aluminum phosphate AIP, and the 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: The nickel-iron-manganese mixed salt solution, the precipitating agent and ammonia water were continuously added into the reaction bottom liquid under an 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 nickel-iron-manganese mixed salt solution flow rate was 350L / h, and the reaction was carried out for 5-6h to obtain the reaction liquid C containing the 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, and the 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 the reaction liquid D; S302, the reaction liquid D was washed and pressure-filtered, and the filter cake E was obtained by dehydration by using a solid-liquid separation device; S303, the filter cake E was put into a disc dryer, the drying temperature range was 120±5℃, the water content of the qualified powder after discharging of the disc dryer was controlled to be less than 0.5%, and the modified layered oxide precursor F coated with the 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 the 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 mixed solution 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: 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.

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: The 25wt% NaOH aqueous solution 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%.

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.

Images