A sodium ion battery positive electrode active material and its preparation method and application

Abstract

The present invention discloses a sodium ion battery positive electrode active material and its preparation method and application. The chemical formula of the sodium ion battery positive electrode active material is Na x Ni y Fe z Mn g M h A m O2, wherein M is a combination of one or more selected from Ti, Al, Mg, Ca, Zr, Y, Zn, Nb, and W, A is a combination of one or more selected from B, P, and C, 0.80≤x≤1.40, 0.05≤y≤0.95, 0.05≤z≤0.95, 0.05≤g≤0.95, 0.01≤h≤0.50, and 0.01≤m≤0.30. The present invention adds M and A elements to the positive active material of a ternary iron-manganese-nickel sodium ion battery and coordinates the proportions of the elements to achieve a perfect layered single crystal structure of the positive active material of the sodium ion battery with large particles, ultimately achieving a stable active material. When applied to a sodium ion battery, while ensuring a high gram-to-gram capacity, the cycle performance at high temperature is significantly improved.

Description

Technical Field

[0001] The present invention belongs to the field of sodium ion batteries, and in particular relates to a sodium ion battery positive electrode active material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have been widely used in electric vehicles, medium- and large-scale energy storage power stations, electric two-wheelers, power tools, portable electronic devices, and other fields. However, with the explosive growth of lithium-ion batteries in electric vehicles and medium- and large-scale energy storage power stations, the structural shortage of lithium resources has become prominent, leading to a surge in lithium salt prices and the cost of lithium-ion batteries. Sodium-ion batteries have similar electrochemical properties to lithium-ion batteries, are abundant in resources, and are relatively low in cost. They have become a popular development direction in recent years and are expected to be widely used in electric two-wheelers and medium- and large-scale energy storage power stations.

[0003] Due to the large radius of sodium ions, sodium-ion batteries have a limited selection of cathode active materials. Currently, three types of cathode active materials that have shown potential for application include Prussian blue, layered oxides, and polyanions. Among them, the O3-structured layered oxide system, similar to the ternary cathode active materials used in lithium-ion batteries, offers advantages such as high capacity and high compaction density. It is considered the most promising cathode material and is being adopted by sodium-ion battery companies both domestically and internationally.

[0004] Chinese patent CN109817970A discloses a method for preparing a single-crystal sodium-ion battery electrode material. The method comprises reacting a mixed aqueous solution of an iron salt, a manganese salt, and an M salt with a precipitant, a complexing agent, and a dispersant to obtain a solid precursor for the battery electrode material. The precursor is then mixed with a sodium salt, sintered, and cooled to obtain the single-crystal sodium-ion battery electrode material. The dispersant is ammonium polyacrylate. Without the specific ammonium polyacrylate dispersant, the crystal morphology of the grains is unclear, and single crystals with large micron-sized particles cannot be formed. Consequently, the discharge capacity and capacity retention of the corresponding battery electrode material are also low.

[0005] Layered oxide positive electrode active materials exhibit excellent electrochemical properties, but they have problems such as multiple structural phase changes during charging and discharging, poor air storage performance, high surface alkalinity, and side reactions with electrolytes, which greatly restrict the large-scale commercial application of this type of active material. Summary of the Invention

[0006] The purpose of the present invention is to provide a sodium ion battery positive electrode active material in view of the shortcomings and deficiencies of the prior art, which can ensure the excellent specific capacity performance of the sodium ion battery, improve the cycle performance under high temperature, and at the same time can form a stable single crystal structure with low surface alkalinity.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is as follows:

[0008] A positive electrode active material for a sodium ion battery, wherein the chemical formula of the positive electrode active material is Na x Ni y Fe z Mn g M h A m O2, wherein M is a combination of one or more selected from Ti, Al, Mg, Ca, Zr, Y, Zn, Nb, and W, A is a combination of one or more selected from B, P, and C, 0.80≤x≤1.40, 0.05≤y≤0.95, 0.05≤z≤0.95, 0.05≤g≤0.95, 0.01≤h≤0.50, and 0.01≤m≤0.30.

[0009] According to some preferred and specific aspects of the present invention, the chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.90≤x≤1.20, 1.2-(y+z+g+h)≥0.

[0010] According to some preferred and specific aspects of the present invention, the chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.95≤x≤1.05, 0.1≤y≤0.5, 0.1≤z≤0.6, 0.1≤g≤0.5, 0.01≤h≤0.3, 0.01≤m≤0.2.

[0011] According to some preferred and specific aspects of the present invention, the chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.98≤x≤1.03, 0.1≤y≤0.4, 0.2≤z≤0.5, 0.1≤g≤0.4, 0.01≤h≤0.2, 0.01≤m≤0.1.

[0012] In some specific embodiments of the present invention, the M is selected from a combination of one or more of Ti, Mg, and Ca, the A is selected from a combination of two or three of B, P, and C, and the molar ratio of B, P, and C is 2-4:0.1-1.5:0.1-1.5.

[0013] In some specific embodiments of the present invention, the positive electrode active material has a layered single crystal structure and an average particle size of 1-30 microns.

[0014] In some specific embodiments of the present invention, the tap density of the positive electrode active material is 1.33-2.5 g / cm 3 , pH value is below 12.6.

[0015] The inventors have discovered through research that by adding M and A elements to the positive electrode active material of a sodium ion battery, and by matching the ratios of sodium, nickel, iron, manganese elements with M, A, and O elements, the positive electrode active material of the sodium ion battery can form a perfect layered single crystal structure. The active material can form large particles, and the particles grow densely, the tap density of the active material is significantly improved, and the pH value of the material is low, the surface alkalinity is low, and it has stable surface properties and few side reactions with the electrolyte. At the same time, when used in a sodium ion battery, it can significantly improve the cycle performance at high temperature while ensuring a high gram-to-gram capacity.

[0016] In the sodium ion battery positive electrode active material of the present invention, various elements play different roles. Among them, Ni and Mn elements enable the sodium ion battery to have a higher gram capacity; Fe element has the dual functions of gram capacity and increasing the discharge voltage of the material; M element improves the stability of the active material; B element promotes the formation of a large-particle single crystal structure of the active material, thereby increasing the compaction density of the material; P element can improve the cycle performance of the active material at high temperatures. In addition, various elements also have a synergistic interaction and work together, so that the sodium ion battery positive electrode active material of the present invention achieves the above-mentioned excellent properties and significantly improves the cycle performance at high temperatures.

[0017] The present invention also provides a method for preparing the above-mentioned sodium ion battery positive electrode active material, the preparation method comprising the following steps:

[0018] 1) reacting a nickel salt, a manganese salt and a hydroxide in the presence of a complexing agent to generate nickel manganese hydroxide;

[0019] 2) nickel manganese hydroxide, iron source, compound containing M element, compound containing A element and sodium source

[0020] Add water to make a slurry, and sand grind to obtain a mixed slurry;

[0021] 3) drying and sintering the mixed slurry to obtain the positive electrode active material for the sodium ion battery.

[0022] Furthermore, the chemical formula of the nickel manganese hydroxide in step 1) is Ni a Mn b(OH)2, where 0.05≤a≤0.95, 0.05≤b≤0.95, 1-ab>0.

[0023] Furthermore, in step 1), the nickel salt is selected from a combination of one or more of nickel sulfate, nickel chloride and nickel nitrate, the manganese salt is selected from a combination of one or more of manganese sulfate, manganese chloride and manganese nitrate, the hydroxide is selected from one or both of sodium hydroxide and potassium hydroxide, and the complexing agent is selected from one or more of ethylenediamine, ethylenediaminetetraacetic acid, tartaric acid, citric acid, oxalic acid and ammonia water.

[0024] In some embodiments of the present invention, in step 1), nickel salt and manganese salt are prepared into a metal salt aqueous solution, which is then mixed with an aqueous hydroxide solution and a complexing agent to obtain a mixed solution, and then the mixed solution is reacted at a pH of 9-12, 40-70° C. and under stirring to produce nickel manganese hydroxide.

[0025] More preferably, the total concentration of nickel ions and manganese ions in the metal salt aqueous solution is 0.5-2 mol / L, and the concentration of the complexing agent in the mixed solution is 0.3-5 mol / L.

[0026] More preferably, the stirring speed is 500-1200 r / min, and after the reaction, the Ni a Mn b (OH)2.

[0027] In some embodiments of the present invention, the iron source in step 2) is selected from a combination of one or more of ferrous oxide, ferric oxide, and ferrosoferric oxide; and the sodium source is selected from one or both of sodium carbonate and sodium hydroxide.

[0028] In some embodiments of the present invention, the compound containing the M element in step 2) is selected from titanium dioxide, aluminum oxide, magnesium oxide, calcium oxide, calcium carbonate, zirconium oxide, yttrium oxide, zinc oxide, niobium oxide, and tungsten oxide; the compound containing the A element is selected from a combination of one or more of boric acid, boron oxide, sodium tetraborate, phosphorus pentoxide, phosphoric acid, sodium phosphate, sodium hypophosphite, glucose, sucrose, polyethylene glycol, and polyvinyl alcohol.

[0029] In some embodiments of the present invention, in step 2), the ratio of the total molar amount of nickel and manganese in the nickel manganese hydroxide, the iron in the iron source, the M element in the compound containing the M element, and the A element in the compound containing the A element to the molar amount of sodium in the sodium source is 1:0.90 to 1.20.

[0030] In some embodiments of the present invention, in step 2), the sand milling time is 0.5 to 8 hours, the grinding body is a zirconia ball with a particle size of 0.1 to 0.8 mm, and the sand milling speed is 800 to 3000 rpm.

[0031] In some embodiments of the present invention, the solid content of the mixed slurry is 10% to 60%, and the median particle size of the particles in the mixed slurry is 20 to 800 nm.

[0032] In some embodiments of the present invention, in step 3), the drying is spray drying, the atomizing disk speed in the spray drying equipment is 1000-3000 rpm, the inlet air temperature is 150-300°C, and the outlet air temperature is 80-120°C.

[0033] In some embodiments of the present invention, in step 3), the sintering is carried out in air at a temperature of 750-1000° C. for 5-25 hours. Preferably, the sintering is followed by pulverization.

[0034] In the preparation method of the present invention, for elements Ni and Mn, which easily form a uniform precipitate, using their hydroxides as raw materials can improve reaction activity. For elements Fe and M, which are less likely to form a uniform precipitate, using their oxides or compounds containing the M element as raw materials ensures the stability of the corresponding element content. Mixing the nickel-manganese hydroxide, the compound containing the M element, the compound containing the A element, and a sodium source, followed by sand milling, ensures that the various elements are fully mixed. Using spray drying prevents component segregation during the molding process of the various raw materials.

[0035] Compared with the prior art, the present invention has the following technical advantages:

[0036] The sodium ion battery positive electrode active material of the present invention can form a perfect layered single crystal structure, the single crystal particles are large and densely grown, the tap density of the positive electrode active material is significantly improved, and the material has a low pH value, stable surface properties, and few side reactions with the electrolyte. At the same time, when used in sodium ion batteries, it can significantly improve the cycle performance at high temperature while ensuring a high gram-to-gram capacity.

[0037] The preparation method of the present invention can produce sodium ion battery positive electrode active materials with excellent performance in large quantities and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The NaNi prepared in Example 1 0.25 Fe 0.4 Mn 0.25 Ti 0.05 B 0.05 Scanning electron microscope image of O2;

[0039] Figure 2 The NaNi prepared in Example 1 0.25 Fe 0.4 Mn 0.25 Ti 0.05 B 0.05 XRD pattern of O2;

[0040] Figure 3 The NaNi prepared in Example 1 0.25 Fe 0.4 Mn 0.25 Ti 0.05 B 0.05 The charge and discharge curve of O2;

[0041] Figure 4 The NaNi prepared in Example 1 0.25 Fe 0.4 Mn 0.25 Ti 0.05 B 0.05 O2 cycle diagram at 2.0~4.0V / 1C high temperature (60℃);

[0042] Figure 5 The NaNi prepared in Example 2 0.25 Fe 0.40 Mn 0.25 Ti 0.03 B 0.05 P 0.02 Scanning electron microscope image of O2;

[0043] Figure 6 The NaNi prepared in Example 2 0.25 Fe 0.40 Mn 0.25 Ti 0.03 B 0.05 P 0.02 XRD pattern of O2;

[0044] Figure 7 The NaNi prepared in Example 2 0.25 Fe 0.40 Mn 0.25 Ti 0.03 B 0.05 P 0.02 The charge and discharge curve of O2;

[0045] Figure 8 The NaNi prepared in Example 2 0.25 Fe 0.40 Mn 0.25 Ti 0.03 B 0.05 P 0.02 O2 cycle diagram at 2.0~4.0V / 1C high temperature (60℃);

[0046] Figure 9 The NaNi prepared in Comparative Example 1 0.25 Fe 0.45 Mn 0.25 Ti 0.05 Scanning electron microscope image of O2;

[0047] Figure 10 The NaNi prepared in Comparative Example 1 0.25 Fe 0.45 Mn 0.25 Ti 0.05 XRD pattern of O2;

[0048] Figure 11 The NaNi prepared in Comparative Example 1 0.25 Fe 0.45 Mn 0.25 Ti 0.05 The charge and discharge curve of O2;

[0049] Figure 12 The NaNi prepared in Comparative Example 1 0.25 Fe 0.45 Mn 0.25 Ti 0.05 O2 cycle diagram at 2.0~4.0V / 1C high temperature (60℃). DETAILED DESCRIPTION

[0050] In order to better understand the content of the present invention, the following is further described in conjunction with specific examples and accompanying drawings. It should be understood that these embodiments are only used for further explanation of the invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, without departing from the principles of the present invention, some improvements and adjustments made by those skilled in the art to the present invention still fall within the scope of protection of the present invention. In the following, unless otherwise specified, all raw materials are obtained from commercial sources.

[0051] In the following examples and comparative examples, charge-discharge curves and high-temperature cycling performance were tested using the following methods: First, a sodium-ion battery was prepared: 20g of the prepared positive electrode active material was weighed, 0.64g of the conductive agent SP and 0.64g of PVDF dissolved in NMP were added, mixed evenly, and coated onto aluminum foil to form an electrode sheet. In an argon-filled glove box, a coin cell was assembled using a sodium metal sheet as the negative electrode, Celgard 2700 as the separator, and 1 mol / L NaPF6 + EC:DEC (1:1) + 5% FEC as the electrolyte. Charge-discharge curves were then tested at a voltage range of 2.0-4.0V, a charge-discharge rate of 0.1C, a current of 13mA, and a test temperature of 25±2°C. Cycling performance was tested at a voltage range of 2.0-4.0V, a charge-discharge rate of 1C, a current of 130mA, and a temperature of 60°C for 100 cycles.

[0052] Example 1

[0053] This embodiment provides a sodium ion battery positive electrode active material, the chemical formula of which is NaNi 0.25 Fe 0.4 Mn 0.25 Ti 0.0 5B 0.05 O2, the preparation method comprises the following steps:

[0054] (1) nickel sulfate and manganese sulfate were added to pure water at a Ni:Mn molar ratio of 1:1 to prepare a solution with a total concentration of metal elements of 1.3 mol / L;

[0055] (2) Prepare 4.0 mol / L sodium hydroxide solution and 5.0 mol / L ammonia solution;

[0056] (3) adding the metal salt solution obtained in step (1) and the sodium hydroxide solution and ammonia solution obtained in step (2) into the reactor at a rate of 2.5 L / h, 1.5 L / h, and 0.2 L / h, respectively, controlling the reaction temperature to 50° C., the reaction pH to 11.5, the stirring speed to 650 rpm, and reacting for 12 h to obtain a precursor;

[0057] (4) The above precursor was washed with pure water, filtered, and dried to obtain Ni 0.5 Mn 0.5 (OH)2;

[0058] (5) Take 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 0.8 mol of Fe2O3, 0.2 mol of TiO2, 0.2 mol of H3BO3, 2.0 mol of Na2CO3, all raw materials are added to 3.5 L of water to prepare a slurry;

[0059] (6) The slurry obtained in step (5) was added to a sand mill and ground for 3 h. The grinding medium was zirconia balls with a particle size of 0.2 mm. The sand milling speed was 2500 rpm. The mixed slurry with an average particle size of about 350 nm was obtained.

[0060] (7) The mixed slurry obtained in step (6) was transferred into a mixing barrel and stirred thoroughly. Pure water was added to adjust the slurry to a solid content of 30±1%. The slurry was spray-dried under the conditions of an atomization frequency of 35 Hz, an inlet air temperature of 190°C, and an outlet air temperature of 85°C in a spray drying equipment. The dried product was sintered in an air atmosphere furnace at 850-940°C for 12 hours, cooled to below 80°C, crushed by jaw crushing, roller crushing, and pulverizing to obtain a positive electrode active material for a sodium ion battery. The sample was named NFM242-TB.

[0061] The scanning electron microscope image of NFM242-TB is as follows Figure 1 As shown in Figure 2, it can be seen that the material is a single crystal morphology. Figure 2 As shown in Figure 2, it can be seen that the material is an α-NaFeO2 type pure phase layered structure. The charge and discharge curve of NFM242-TB is shown in Figure 2. Figure 3 As shown in the figure, it can be seen that within the voltage window of 2.0~4.0V, the discharge capacity at 0.1C rate is 124.8mAh / g. Figure 4 As shown, it can be seen that at 60°C, within the voltage window of 2.0-4.0V, and at a rate of 1C, the capacity retention rate is 89.04% after 100 cycles.

[0062] Example 2

[0063] The chemical formula of the positive electrode active material of the sodium ion battery in this embodiment is NaNi 0.25 Fe 0.40 Mn 0.25 Ti 0.03 B 0.0 5P 0.02 O2.

[0064] The preparation method is basically the same as that in Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 0.8 mol Fe2O3, 0.12 mol TiO2, 0.2 mol H3BO3, 0.08 mol H3PO4, and 2.0 mol Na2CO3 were added to 3.5 L of water to form a slurry. The sample was named NFM242-TBP.

[0065] The scanning electron microscopy image of NFM242-TBP is as follows Figure 5As shown in Figure 2, it can be seen that the material is a single crystal morphology. Figure 6 As shown, it can be seen that the material is an α-NaFeO2 type pure phase layered structure. The charge and discharge curve of NFM242-TBP is shown in the figure. Figure 7 As shown in the figure, it can be seen that within the voltage window of 2.0~4.0V, the discharge capacity at 0.1C rate is 125mAh / g. Figure 8 As shown, it can be seen that at 60°C, within the voltage window of 2.0-4.0V, and at a rate of 1C, the capacity retention rate is 93.31% after 100 cycles.

[0066] Example 3

[0067] The chemical formula of the positive electrode active material of the sodium ion battery in this embodiment is NaNi 0.25 Fe 0.4 Mn 0.25 Ti 0.05 P 0.05 O2.

[0068] The preparation method is basically the same as that in Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 0.8mol Fe2O3, 0.20mol TiO2, 0.2mol H3PO4, 2.0mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverizing, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.4 Mn 0.25 Ti 0.05 P 0.05 O2, the sample name is NFM242-TP.

[0069] Example 4

[0070] The chemical formula of the positive electrode active material of the sodium ion battery in this embodiment is NaNi 0.25 Fe 0.4 Mn 0.25 Ca 0.05 B 0.05 O2.

[0071] The preparation method is basically the same as that in Example 1, except that: in step (5), 2.0 mol of Ni 0.5 Mn 0.5(OH)2, 0.8mol Fe2O3, 0.2mol CaCO3, 0.2mol H3BO3, 2.0mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.4 Mn 0.25 Ca 0.05 B 0.05 O2, the sample name is NFM242-CaB.

[0072] Example 5

[0073] The chemical formula of the positive electrode active material of the sodium ion battery in this embodiment is NaNi 0.25 Fe 0.4 Mn 0.25 Ca 0.05 P 0.05 O2.

[0074] The preparation method is basically the same as that in Example 1, except that: in step (5), 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 0.8mol Fe2O3, 0.2mol CaCO3, 0.2mol H3PO4, 2.0mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.4 Mn 0.25 Ca 0.05 P 0.05 O2, the sample name is NFM242-CaP.

[0075] Example 6

[0076] The chemical formula of the positive electrode active material of the sodium ion battery in this embodiment is NaNi 0.25 Fe 0.40 Mn 0.25 Ca 0.03 B 0.0 5P 0.02 O2.

[0077] The preparation method is basically the same as that in Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5(OH)2, 0.8mol Fe2O3, 0.12mol CaCO3, 0.2mol H3BO3, 0.08mol H3PO4, 2.0mol Na2CO3, all raw materials are added into 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.40 Mn 0.25 Ca 0.03 B 0.05 P 0.02 O2, the sample name is NFM242-CaBP.

[0078] Comparative Example 1

[0079] The same as Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 0.9 mol Fe2O3, 0.2 mol TiO2, 2.0 mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.45 Mn 0.25 Ti 0.05 O2, the sample name is NFM242-T.

[0080] The scanning electron microscope image of NFM242-T is as follows Figure 9 As shown in the figure, it can be seen that the material is composed of small primary particles agglomerated into a loose spherical structure and cannot form a single crystal structure. Figure 10 As shown in Figure 2, it can be seen that the material is an α-NaFeO2 type pure phase layered structure. The charge and discharge curve of NFM242-T is shown in Figure 2. Figure 11 As shown in the figure, it can be seen that within the voltage window of 2.0~4.0V, the discharge capacity at 0.1C rate is 126.6mAh / g. Figure 12 As shown, it can be seen that at 60°C, within the voltage window of 2.0 to 4.0 V, and at a rate of 1C, the capacity retention rate is 82.8% after 100 cycles.

[0081] Comparative Example 2

[0082] The same as Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5(OH)2, 0.9 mol Fe2O3, 0.2 mol CaCO3, 2.0 mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.45 Mn 0.25 Ca 0.05 O2, the sample name is NFM242-Ca.

[0083] Comparative Example 3

[0084] The same as Example 1, except that step (5) is replaced by taking 2.0 mol of Ni 0.5 Mn 0.5 (OH)2, 1.0 mol Fe2O3, 2.0 mol Na2CO3, all raw materials are added to 3.5L water to prepare slurry. After sand milling, spray drying, sintering, jaw crushing, rolling, and pulverization, the final NaNi positive electrode active material for sodium ion batteries is obtained. 0.25 Fe 0.50 Mn 0.25 O2, the sample name is NFM252.

[0085] Performance Testing

[0086] The positive electrode active materials prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to physicochemical performance testing. The pH value was tested by weighing 5 g of the prepared layered oxide positive electrode material and dispersing it in 50 mL of deionized water. The mixture was stirred on a magnetic stirrer for 5 minutes, then allowed to stand at 25°C for 30 minutes. The mixture was then filtered, and the filtrate was tested for pH using a pH meter. The physicochemical performance results are shown in Table 1 below.

[0087] Table 1. Physical properties of positive electrode active materials

[0088]

[0089]

[0090] The positive electrode active materials prepared in Examples 1-7 and Comparative Examples 1-2 were used to test the performance of sodium ion batteries. The sodium ion battery production method was as follows: 20g of the prepared positive electrode active material was weighed, 0.64g of conductive agent SP and 0.64g of PVDF dissolved in NMP were added, and the mixture was evenly coated on aluminum foil to form an electrode sheet. In an argon atmosphere glove box, a sodium metal sheet was used as the negative electrode, Celgard 2700 was used as the separator, and 1mol / L NaPF6+EC:DEC (1:1)+5% FEC was used as the electrolyte to assemble a button cell. The test voltage range was 2.0-4.0V, and the 0.1C current was 13mA. The test results are shown in Table 2 below.

[0091] Table 2. Performance of sodium ion batteries

[0092]

[0093] As can be seen from Table 1-2 above, the present invention adds B and P elements to the positive electrode active material of the sodium ion battery and controls the ratio of all elements, so that the positive electrode active material can form a perfect layered single crystal structure, and the single crystal particles are large and densely grown. The tap density of the positive electrode active material is significantly improved and the pH value is reduced. When the positive electrode active material is used in a sodium ion battery, the cycle performance at high temperature can be significantly improved while ensuring a high gram-specific capacity.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium ion battery positive electrode active material, characterized in that: The chemical formula of the positive electrode active material is Na x Ni y Fe z Mn g M h A m O2, wherein M is a combination of one or more selected from Ti, Mg, and Ca, A is a combination of B and P, 0.80≤x≤1.40, 0.05≤y≤0.95, 0.05≤z≤0.95, 0.05≤g≤0.95, 0.01≤h≤0.50, and 0.01≤m≤0.30; The positive electrode active material is prepared by a preparation method comprising the following steps: 1) reacting a nickel salt, a manganese salt and a hydroxide in the presence of a complexing agent to generate nickel manganese hydroxide; 2) adding water to nickel manganese hydroxide, an iron source, a compound containing an M element, a compound containing an B element, a compound containing an P element, and a sodium source to form a slurry, and sand-milling to obtain a mixed slurry; 3) drying and sintering the mixed slurry to obtain the positive electrode active material for the sodium ion battery.

2. The sodium ion battery positive electrode active material according to claim 1, wherein: The chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.90≤x≤1.20, 1.2-(y+z+g+h)≥0.

3. The positive electrode active material for sodium ion batteries according to claim 1, wherein: The chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.95≤x≤1.05, 0.1≤y≤0.5, 0.1≤z≤0.6, 0.1≤g≤0.5, 0.01≤h≤0.3, 0.01≤m≤0.

2.

4. The sodium ion battery positive electrode active material according to claim 1, wherein: The chemical formula Na x Ni y Fe z Mn g M h A m In O2, 0.98≤x≤1.03, 0.1≤y≤0.4, 0.2≤z≤0.5, 0.1≤g≤0.4, 0.01≤h≤0.2, 0.01≤m≤0.

1.

5. The sodium ion battery positive electrode active material according to claim 1, wherein: The positive electrode active material has a layered single crystal structure and an average particle size of 1-30 microns.

6. The positive electrode active material for sodium ion batteries according to claim 1, wherein: The tap density of the positive electrode active material is 1.33-2.5 g / cm 3 , pH value is below 12.

6.

7. A method for preparing the positive electrode active material for a sodium ion battery according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: 1) reacting a nickel salt, a manganese salt and a hydroxide in the presence of a complexing agent to generate nickel manganese hydroxide; 2) nickel manganese hydroxide, iron source, compound containing M element, compound containing B element The compound, the compound containing P element and the sodium source are added with water to form a slurry, and the mixed slurry is obtained after sand grinding. material; 3) drying and sintering the mixed slurry to obtain the positive electrode active material for the sodium ion battery.

8. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: The chemical formula of the nickel manganese hydroxide in step 1) is Ni a Mn b (OH)2, wherein 0.05≤a≤0.95, 0.05≤b≤0.95, 1-ab=0.

9. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 1), the nickel salt is selected from a combination of one or more of nickel sulfate, nickel chloride and nickel nitrate, the manganese salt is selected from a combination of one or more of manganese sulfate, manganese chloride and manganese nitrate, the hydroxide is selected from one or both of sodium hydroxide and potassium hydroxide, and the complexing agent is selected from one or more of ethylenediamine, ethylenediaminetetraacetic acid, tartaric acid, citric acid, oxalic acid and ammonia water.

10. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 1), nickel salt and manganese salt are prepared into a metal salt aqueous solution, which is then mixed with a hydroxide aqueous solution and a complexing agent to obtain a mixed solution. The mixed solution is then reacted at a pH of 9-12, 40-70° C., and stirred to generate nickel manganese hydroxide.

11. The method for preparing a positive electrode active material for a sodium ion battery according to claim 10, wherein: The total concentration of nickel ions and manganese ions in the metal salt aqueous solution is 0.5-2 mol / L, and the concentration of the complexing agent in the mixed solution is 0.3-5 mol / L.

12. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 2), the iron source is selected from a combination of one or more of ferrous oxide, ferric oxide, and ferrosoferric oxide; and the sodium source is selected from one or both of sodium carbonate and sodium hydroxide.

13. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: The compound containing the M element in step 2) is selected from a combination of one or more of titanium dioxide, magnesium oxide, calcium oxide, and calcium carbonate; the compound containing the B element is selected from a combination of one or more of boric acid, boron oxide, and sodium tetraborate; and the compound containing the P element is selected from a combination of one or more of phosphorus pentoxide, phosphoric acid, sodium phosphate, and sodium hypophosphite.

14. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 2), the ratio of the total molar amount of nickel and manganese in the nickel manganese hydroxide, the iron in the iron source, the M element in the compound containing the M element, the B element in the compound containing the B element, and the P element in the compound containing the P element to the molar amount of sodium in the sodium source is 1:0.90 to 1.

20.

15. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 2), the sand milling time is 0.5 to 8 hours, the grinding body is a zirconia ball with a particle size of 0.1 to 0.8 mm, and the sand milling speed is 800 to 3000 rpm.

16. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: The median particle size of the particles in the mixed slurry is 20 to 800 nm, and the solid content of the mixed slurry is 10% to 60%.

17. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 3), the drying is spray drying, the atomizing disk speed in the spray drying equipment is 1000-3000 rpm, the inlet air temperature is 150-300°C, and the outlet air temperature is 80-120°C.

18. The method for preparing a positive electrode active material for a sodium ion battery according to claim 7, wherein: In step 3), the sintering is carried out in air at a temperature of 750 to 1000° C. for 5 to 25 hours.

19. Use of the sodium ion battery positive electrode active material according to any one of claims 1 to 6 in a sodium ion battery positive electrode.

20. A positive electrode material for a sodium ion battery, comprising a positive electrode active material, a binder, and a conductive agent, characterized in that: The positive electrode active material comprises the positive electrode active material for a sodium ion battery according to any one of claims 1 to 6.

21. A sodium ion battery positive electrode, characterized in that: The sodium ion battery positive electrode is prepared from the sodium ion battery positive electrode material according to claim 20.

22. A sodium ion battery comprising a positive electrode, characterized in that: The positive electrode comprises the sodium ion battery positive electrode according to claim 21.

Images