Single-crystal sodium-ion battery positive electrode active material, its manufacturing method, and applications

Abstract

The present invention discloses a method for preparing a single crystal sodium ion battery positive electrode active material, the single crystal sodium ion battery positive electrode active material includes sodium, M metal, boron and oxygen elements, and the preparation method includes the steps of adding water to an M element-containing compound, a boron element-containing compound and a sodium source, preparing a slurry, and sanding the slurry to obtain a mixed slurry, and spray-drying and sintering the mixed slurry to obtain the single crystal sodium ion battery positive electrode active material. The preparation method of the present invention is applicable to a wide variety of raw materials, and can efficiently realize uniform mixing of various raw materials at the nano level, and the mixed slurry can form a perfect layered O3 phase structure after sintering, and the prepared single crystal sodium ion battery positive electrode material can be used to provide excellent electrochemical performance and cycle performance in sodium ion batteries.

Description

[Technical Field]

[0001] This invention relates to the field of sodium-ion batteries, and more specifically to a method for producing a positive electrode active material for a single-crystal sodium-ion battery. [Background technology]

[0002] Due to the large radius of sodium ions, the selection of cathode active materials for sodium-ion batteries is relatively limited. Currently, the cathode active materials for sodium-ion batteries with potential applications include three systems: Prussian blue, layered oxides, and polyanions. The O3-phase layered oxide system is similar to the ternary cathode active materials in lithium-ion batteries, offering advantages such as high capacity and high compaction density. It is considered the most promising cathode material and is used by sodium-ion battery companies both domestically and internationally.

[0003] Currently, oxide-based sodium-ion battery cathode active materials mainly have a secondary spherical particle structure. For example, Chinese Patent CN110416521A publishes a magnesium-doped sodium-ion battery ternary cathode material and a method for manufacturing the same. The manufacturing method includes: Step 1: Weighing out 112 parts by weight of sodium carbonate, 40-50 parts by weight of nickel monoxide, 54 parts by weight of ferric oxide, 48 parts by weight of manganese monoxide, and 0.1-5.6 parts by weight of magnesium oxide, adding them to 610 parts by weight of deionized water, and stirring to obtain a mixture; Step 2: Adding the mixture obtained in Step 1) to a nanoball mill and ball milling for 20-80 minutes, removing the slurry and spray drying at 80-120°C to obtain a precursor powder; and Step 3: Heating the precursor powder obtained in Step 2 to 750-1000°C at 2-5°C / min in an air atmosphere and sintering for 9-15 hours, then cooling to room temperature to obtain a magnesium-doped sodium-ion battery ternary cathode material. As shown in Figure 2 of the patent, the material obtained by this method is a fluffy secondary particle sphere with a secondary particle size of approximately 8 μm and a primary particle size of 0.15 to 0.4 μm. Such a spherical structure is easily crushed, has low compaction density and a large specific surface area, and during battery cycling, there are many side reactions between the positive electrode material and the electrolyte, generating a large amount of gas, thus resulting in poor battery cycle performance and safety performance.

[0004] China Patent CN113471431A contains NaMn 0.5 Ni 0.5 B x A cathode material for O2 sodium ion batteries has been disclosed. This material has a composite phase of P2 and O3 phases and possesses a relatively dense secondary spherical morphology. The manufacturing method involves mixing materials containing a sodium source, manganese source, nickel source, and boron source in a molar ratio of Na:Mn:Ni:B elements (1~1.05):0.5:0.5:x to obtain a mixture, which is then heat-treated at 800~900°C in an oxygen-containing atmosphere to obtain the cathode material. This cathode material improves the electrochemical performance of the P2 phase by using the O3 phase, and thus has improved electrochemical performance compared to the P2 phase material. However, this patented method cannot produce a pure O3 phase material, leaving room for further improvement in the corresponding electrochemical performance of the material.

[0005] The above-mentioned conventional secondary spherical particle structure has several problems as follows. 1. The mechanical strength of the particle structure is low, and in the process of compressing the pole piece, the secondary spheres are likely to break, which affects the pole piece compaction density and cycle performance. 2. The active material has a large contact surface area with the electrolyte, and more side reactions occur when contacting the electrolyte, which affects the cycle performance and safety performance.

[0006] Regarding this, engineers are engaged in manufacturing the positive electrode active material of the oxide-based sodium-ion battery in a single crystal form. For example, in Chinese Patent CN109817970A, after mixing and reacting an aqueous mixed solution of an iron salt, a manganese salt and an M salt, a precipitant, a complexing agent and a dispersant, the obtained solid is used as a precursor of the battery electrode material, and the precursor and a sodium salt are mixed and sintered, and then cooled to obtain a single crystal sodium-ion battery electrode material, and a method for manufacturing a single crystal sodium-ion battery electrode material in which the dispersant is ammonium polyacrylate is disclosed. Such a method has a solubility product constant of the iron salt too low in a large-scale production process, is likely to precipitate earlier than other metals, and the coprecipitated substances are unevenly distributed, directly affecting the electrochemical performance.

Summary of the Invention

Problems to be Solved by the Invention

Means for Solving the Problems

[0007] In view of the disadvantages and deficiencies of the prior art, the present invention aims to provide a method for manufacturing a positive electrode active material of a single crystal sodium-ion battery that can stably manufacture a positive electrode active material of a single crystal sodium-ion battery with high compaction density, small specific surface area and excellent electrochemical performance on a large scale.

Means for Solving the Problems

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows.

[0009] A method for manufacturing a single-crystal sodium-ion battery cathode active material, wherein the single-crystal sodium-ion battery cathode active material contains elements of sodium, M metal, boron and oxygen, and the manufacturing method includes adding water to a compound containing M element, a compound containing boron element and a sodium source to produce a slurry and sanding to obtain a mixed slurry, and spray-drying and sintering the mixed slurry to obtain the single-crystal sodium-ion battery cathode active material.

[0010] According to some preferred specific embodiments of the present invention, the chemical formula of the single-crystal sodium-ion battery cathode active material is Na x M y B z O2, where M is one or a combination of more selected from Li, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, W, Ta, Ba, Bi, La, Ce, Eu, and 0.80≦x≦1.40, 0.6≦y≦0.9999, 0.0001≦z≦0.4.

[0011] Preferably, in the chemical formula Na x M y B z O2, 0.95≦x≦1.05, 0.8≦y≦0.9999, 0.0001≦z≦0.2.

[0012] More preferably, in the chemical formula Na x M y B z O2, 0.98≦x≦1.04, 0.9≦y≦0.9999, 0.0001≦z≦0.1.

[0013] In some specific embodiments of the present invention, the M is selected from one or a combination of more of Fe, Ni, Mn, Cu, Ti.

[0014] In some specific embodiments of the present invention, the M-element-containing compound is selected from one or more combinations of oxides, hydroxides, carbonates, oxalates, and nitrates of the M-element.

[0015] Furthermore, the M-element-containing compound is selected from one or more combinations of nickel manganese hydroxide, ferric oxide, titanium dioxide, nickel oxide, and manganese dioxide.

[0016] In some specific embodiments of the present invention, the boron-containing compound is selected from one or more combinations of boron oxide, boric acid, borate, borohydride salt, boron trihalide, trifluoroboric acid, borate ester, borane, and metal borides.

[0017] Furthermore, the boron-containing compound is selected from one or a combination of boric acid and boron oxide.

[0018] In some specific embodiments of the present invention, the sodium source is selected from one or more combinations of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium nitrate, sodium acetate, and sodium oxalate.

[0019] Furthermore, the sodium source is selected from one or more combinations of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0020] In some specific embodiments of the present invention, the molar ratio of the M-element-containing compound, the boron-containing compound, and the sodium source is (0.6~0.9999):(0.4~0.0001):(0.80~1.40).

[0021] More preferably, the molar ratio of the M-element-containing compound, the boron-containing compound, and the sodium source is (0.9~0.9999):(0.1~0.0001):(0.90~1.10).

[0022] Furthermore, the molar ratio of the M-element-containing compound, the boron-containing compound, and the sodium source is 0.95:0.05:1.0.

[0023] In some specific embodiments of the present invention, the sanding time is 0.6 to 7.8 hours.

[0024] Furthermore, the sanding time is 1 to 4 hours.

[0025] In some specific embodiments of the present invention, the sanding abrasive is a zirconia sphere with a particle size of 0.1 to 0.8 mm.

[0026] In some specific embodiments of the present invention, the sanding speed is 800 to 3000 rpm.

[0027] Furthermore, the sanding speed is 1500 to 2500 rpm.

[0028] In some specific embodiments of the present invention, the solid content of the mixed slurry is 10% to 60%.

[0029] Furthermore, the solid content of the mixed slurry is 20-40%.

[0030] In some specific embodiments of the present invention, the median particle size of the particles in the mixed slurry is 20 to 800 nm.

[0031] In some specific embodiments of the present invention, the mixed slurry is pulverized after sintering.

[0032] Furthermore, in the case of spray drying, the rotation speed of the atomizer disc is 1000 to 3000 rpm, the intake air temperature is 150 to 300°C, and the discharge air temperature is 80 to 120°C.

[0033] In some specific embodiments of the present invention, the sintering is carried out in air, and the sintering is performed at a temperature of 750 to 1100°C for a period of 5 to 25 hours.

[0034] Furthermore, the sintering process is carried out at a temperature of 850-1000°C for 8-16 hours.

[0035] In the manufacturing method of the present invention, sanding is used during the production of the mixed slurry to process water-soluble substances and achieve uniform mixing at the molecular level, process water-insoluble raw materials and achieve uniform mixing of insoluble substances at the nano level, and process uniform mixing at the nano level between water-soluble and water-insoluble raw materials. Sanding ensures uniform mixing of raw materials at the nano level, and a positive electrode material with excellent electrochemical activity can be stably obtained during high-temperature sintering. Furthermore, by adding a boron-containing compound to the raw materials, nano-level primary particles rapidly melt and bond during high-temperature sintering, enabling the sintering of single-crystal sodium-ion battery positive electrode active material of about 1 to 30 μm. Since this material is not fluffy, it has a high compaction density and can significantly reduce side reactions between the positive electrode material and the electrolyte. In addition, the particle size of the positive electrode active material single crystal particles can be controlled by adjusting the boron content in the single-crystal positive electrode active material. The sanding method and the addition of boron-containing compounds have a synergistic effect, and both are essential for the production of perfect single-crystal cathode active materials.

[0036] Furthermore, the present invention allows for spray drying of a mixed slurry, and the spray drying method ensures that the uniform distribution of various raw materials is maintained during the drying process of a uniformly mixed slurry, guaranteeing that the various raw materials do not separate during the molding process.

[0037] This invention exhibits a single-crystal structure in its fine morphology, and has an average grain size D 50 The particle size is 1-30 μm, and the compacted density is 2.8-3.6 g / cm³. 3 , with a specific surface area of ​​0.2 to 1.0 m² 2Further, we provide a single-crystal sodium-ion battery positive electrode active material produced by the above manufacturing method, which has a density of / g.

[0038] The present invention further provides the use of a single-crystal sodium-ion battery cathode active material in the cathode of a sodium-ion battery.

[0039] When this single-crystal sodium-ion battery positive electrode active material is applied to the positive electrode of a sodium-ion battery, the resulting sodium-ion battery has an initial gram capacity of 123-130 mAh / g at 0.1C and 25°C, a gram capacity of 117-127 mAh / g after one cycle at 1C and 60°C, and a gram capacity of 100-120 mAh / g after 100 cycles at 1C and 60°C. In other words, the cycle retention rate after 100 cycles at a high temperature of 60°C is 84-92%.

[0040] The present invention further provides a sodium-ion battery cathode material comprising a cathode active material including the single-crystal sodium-ion battery cathode active material, an adhesive, and a conductive agent.

[0041] The present invention further provides a sodium-ion battery cathode manufactured from the sodium-ion battery cathode material described above.

[0042] The present invention further provides a sodium-ion battery comprising a positive electrode including the sodium-ion battery positive electrode.

[0043] Compared to the prior art, the present invention has the following technical advantages.

[0044] The manufacturing method of the present invention can be applied to a wide variety of raw materials and can efficiently achieve uniform mixing of various raw materials at the nanoscale. The mixed slurry can form a perfect layered O3 phase structure after sintering.

[0045] By doping with boron element based on the sanding method, it is possible to manufacture large single crystals. This overcomes the drawbacks of conventional technology, where the raw material particles are too fine, the sintered material is very fluffy, the specific surface area is large, the compaction density during electrode manufacturing of the positive electrode active material is low, there are many side reactions between the positive electrode material and the electrolyte during battery cycling, a large amount of gas is generated, and the battery cycle performance and safety performance are low. This invention allows for the adjustment and manufacture of single crystal particles at the 1 to 30 μm level by controlling the boron element content in the single crystal positive electrode active material. This results in stable surface properties, fewer side reactions with the electrolyte, and, assuming high gram-to-capacity when used in sodium-ion batteries, significantly improved high-temperature cycle performance. [Brief explanation of the drawing]

[0046] [Figure 1] This is a scanning electron microscope image of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Example 1. [Figure 2] This is an XRD diagram of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Example 1. [Figure 3] This is a charge-discharge curve diagram of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Example 1. [Figure 4] This is a scanning electron microscope image of NaNi0.31Fe0.33Mn0.31B0.05O2 produced in Example 2. [Figure 5] This is an XRD diagram of NaNi0.31Fe0.33Mn0.31B0.05O2 produced in Example 2. [Figure 6] This is a charge-discharge curve diagram of NaNi0.31Fe0.33Mn0.31B0.05O2 produced in Example 2. [Figure 7] This is the cycle diagram of NaNi0.31Fe0.33Mn0.31B0.05O2 produced in Example 2 at a high temperature of 2.0~4.0V / 1C (60°C). [Figure 8]This is a scanning electron microscope image of NaNi0.25Fe0.40Mn0.25Ti0.05B0.05O2 produced in Example 4. [Figure 9] This is an XRD diagram of NaNi0.25Fe0.40Mn0.25Ti0.05B0.05O2 produced in Example 4. [Figure 10] This is a charge-discharge curve diagram of NaNi0.25Fe0.40Mn0.25Ti0.05B0.05O2 produced in Example 4. [Figure 11] This is the cycle diagram of NaNi0.25Fe0.40Mn0.25Ti0.05B0.05O2 produced in Example 4 at a high temperature of 2.0~4.0V / 1C (60°C). [Figure 12] This is a scanning electron microscope image of NaNi1 / 3Fe1 / 3Mn1 / 3O2 produced in Comparative Example 1. [Figure 13] This is an XRD diagram of NaNi1 / 3Fe1 / 3Mn1 / 3O2 produced in Comparative Example 1. [Figure 14] This is a charge-discharge curve diagram of NaNi1 / 3Fe1 / 3Mn1 / 3O2 produced in Comparative Example 1. [Figure 15] This is the cycle diagram of NaNi1 / 3Fe1 / 3Mn1 / 3O2 produced in Comparative Example 1 at a high temperature of 2.0~4.0V / 1C (60°C). [Figure 16] This is a scanning electron microscope image of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Comparative Example 2. [Figure 17] This is an XRD diagram of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Comparative Example 2. [Figure 18] This is a charge-discharge curve diagram of NaNi0.32Fe0.33Mn0.32B0.03O2 produced in Comparative Example 2. [Modes for carrying out the invention]

[0047] To better understand the contents of the present invention, further explanation will be given below with reference to specific examples and drawings. It should be understood that these examples are merely for the purpose of further illustrating the invention and do not limit the scope of the present invention. Furthermore, after reading the contents of the present invention, it should be understood that any improvements or modifications made by those skilled in the art to the present invention without departing from the principles of the present invention are also covered within the scope of the present invention. Unless otherwise specified below, all raw materials are commercially available.

[0048] In the following examples and comparative examples, charge-discharge curves and high-temperature cycle performance tests were performed using the methods described below. First, to manufacture the sodium-ion battery, 20g of prepared positive electrode active material was weighed out, 0.64g of conductive agent SP and 0.64g of NMP dissolved in PVDF were added, and after uniform mixing, the mixture was coated onto aluminum foil to manufacture an electrode sheet. In a glove box under an argon atmosphere, a button cell was assembled using metallic sodium flakes as the negative electrode, Celgard 2700 as the diaphragm, and 1 mol / L NaPF6 + EC:DEC (1:1) + 5% FEC as the electrolyte. The charge-discharge curve was then tested under the conditions of a voltage range of 2.0~4.0V, a charge-discharge ratio of 0.1C, a current of 13mA, and a test temperature of 25±2℃. The cycle performance was then tested by performing 100 cycles under the conditions of a voltage range of 2.0-4.0V, a charge-discharge ratio of 1C, a current of 130mA, and a temperature of 60℃.

[0049] Example 1 In this embodiment, the chemical formula is NaNi 0.32 Fe 0.33 Mn 0.32 B 0.03 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) 3.2 mol Ni 0.5 Mn 0.5 The process involves taking (OH)2, 0.825 mol Fe2O3, 0.15 mol H3BO3, and 2.5 mol Na2CO3, and adding all the raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, and pure water is added to prepare a slurry with a solid content of 30±1%. The slurry is spray-dried under conditions where the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190°C, and the blown air temperature is 85°C. After drying, the product is sintered in an atmospheric furnace at 850~1000°C for 12 hours, cooled to below 80°C, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery positive electrode active material (sample name is NFM-B1).

[0050] A scanning electron microscope image of NFM-B1 is shown in Figure 1, which shows that the material is in a single-crystal form. The XRD of NFM-B1 is shown in Figure 2, which shows that the material has an α-NaFeO2 type pure-phase layered structure. The charge-discharge curve of NFM-B1 is shown in Figure 3, which shows that the discharge ratio capacity at a 0.1C magnification within a voltage window of 2.0 to 4.0 V is 128.8 mAh / g.

[0051] Example 2 In this embodiment, the chemical formula is NaNi 0.31 Fe 0.33 Mn 0.31 B 0.05 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) 3.1 mol Ni 0.5 Mn 0.5 The process involves taking (OH)2, 0.825 mol Fe2O3, 0.25 mol H3BO3, and 2.5 mol Na2CO3, and adding all the raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, and pure water is added to prepare a slurry with a solid content of 30±1%. The slurry is spray-dried under conditions where the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃. After drying, the product is sintered in an atmospheric furnace at 850~1000℃ for 12 hours, cooled to below 80℃, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery positive electrode active material (sample name is NFM-B2).

[0052] A scanning electron microscope image of NFM-B2 is shown in Figure 4, which shows that the material is in a single-crystal form. The XRD of NFM-B2 is shown in Figure 5, which shows that the material has an α-NaFeO2 type pure-phase layered structure. The charge-discharge curve of NFM-B2 is shown in Figure 6, which shows that the discharge ratio capacity at a 0.1C magnification within a voltage window of 2.0 to 4.0 V is 129.1 mAh / g. The high-temperature cycle diagram of NFM-B2 is shown in Figure 7, which shows that after 100 cycles at 60°C, within a voltage window of 2.0 to 4.0 V, and at a 1C magnification, the capacity retention rate is 90.9%.

[0053] Example 3 In this embodiment, the chemical formula is NaNi 0.31 Fe 0.33 Mn 0.31 B 0.05 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) Take 1.55 mol NiO, 1.55 mol MnO2, 0.825 mol Fe2O3, 0.25 mol H3BO3, and 2.5 mol Na2CO3, and add all raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, pure water is added to prepare a slurry with a solid content of 30±1%, spray-dried under conditions where the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃, and the dried product is sintered in an atmospheric furnace at 850~1000℃ for 12 hours, cooled to below 80℃, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery positive electrode active material (sample name is NFM-B3).

[0054] Example 4 In this embodiment, the chemical formula is NaNi 0.25 Fe 0.40 Mn 0.25 Ti 0.05 B 0.05 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) 2.5 mol Ni 0.5 Mn 0.5 The process involves taking (OH)2, 1 mol of Fe2O3, 0.25 mol of TiO2, 0.25 mol of H3BO3, and 2.5 mol of Na2CO3, and adding all the raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, pure water is added to prepare a slurry with a solid content of 30±1%, spray-dried under conditions where the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃, and the dried product is sintered in an atmospheric furnace at 850~1000℃ for 12 hours, cooled to below 80℃, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery cathode active material, the sample name of which is NFM-B3.

[0055] A scanning electron microscope image of NFM-TB1 is shown in Figure 8, showing that the material is in a single-crystal form. TB1 of NFM-B2 is shown in Figure 9, showing that the material is in an α-NaFeO2 type pure-phase layered structure. The charge-discharge curve of NFM-TB1 is shown in Figure 10, and 2 Within a voltage window of 0.0 to 4.0V, the discharge ratio capacity at a 0.1C multiplier is 124.8mAh / g. The high-temperature cycle diagram of NFM-B2 is shown in Figure 7, and it can be seen that after 100 cycles at 60°C, within a voltage window of 2.0 to 4.0V, and at a 1C multiplier, the capacity retention rate is 90.9%.

[0056] Example 5 In this embodiment, the chemical formula is NaNi 0.25 Fe 0.40 Mn 0.25 Ti 0.05 B 0.05 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) A step in which 1.25 mol NiO, 1.25 mol MnO2, 1 mol Fe2O3, 0.25 mol TiO2, 0.25 mol H3BO3, and 2.5 mol Na2CO3 are taken and all raw materials are added to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, and pure water is added to prepare a slurry with a solid content of 30±1%. The slurry is spray-dried under conditions where the atomization frequency of the spray drying equipment is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃. After drying, the product is sintered in an atmospheric furnace at 850~1000℃ for 12 hours, cooled to below 80℃, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery positive electrode active material (sample name is NFM-B3).

[0057] Example 6 In this embodiment, the chemical formula is NaNi 0.25 Fe 0.40 Mn 0.30 B 0.05 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) Take 1.25 mol NiO, 1.50 mol MnO2, 1 mol Fe2O3, 0.25 mol H3BO3, and 2.5 mol Na2CO3, and add all raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) The mixed slurry produced in step (2) is transferred to a mixing drum, thoroughly stirred, pure water is added to prepare a slurry with a solid content of 30±1%, spray-dried under conditions where the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃, and the dried product is sintered in an atmospheric furnace at 850~1000℃ for 12 hours, cooled to below 80℃, jaw-crushed, roller-paired, and pulverized to obtain a sodium-ion battery positive electrode active material (sample name is NFM-B3).

[0058] Comparative Example 1 In this embodiment, the chemical formula is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) 3.33 mol Ni 0.5 Mn 0.5 The process involves taking (OH)2, 0.835 mol of Fe2O3, and 2.5 mol of Na2CO3, and adding all the raw materials to 3.5 L of water to prepare a slurry. (2) Add the slurry obtained in step (1) to a sand mill and polish for 3 hours, the abrasive material being zirconia spheres with a particle size of 0.2 mm, the sanding rotation speed being 2500 rpm, and the polishing process to obtain a mixed slurry with an average particle size of approximately 350 nm. (3) Transfer the mixed slurry produced in step (2) to a mixing drum, stir thoroughly, add pure water to prepare a slurry with a solid content of 30±1%, spray dry under the conditions that the atomization frequency of the spray dryer is 35Hz, the intake air temperature is 190℃, and the blown air temperature is 85℃, and after drying, sinter the product in an atmospheric furnace at 850~1000℃ for 12 hours until it reaches below 80℃. The process includes cooling, jaw crushing, roller pairing, grinding, and obtaining a sodium-ion battery cathode active material (sample name is NFM-1).

[0059] A scanning electron microscope image of NFM-1 is shown in Figure 12, revealing that the material consists of fluffy secondary particle spheres with primary particles of approximately 0.5 μm within the spheres. The XRD of NFM-1 is shown in Figure 13, revealing that the material has an α-NaFeO2 type pure-phase layered structure. The charge-discharge curve of NFM-1 is shown in Figure 14, showing that the discharge ratio capacity at a 0.1C magnification within a voltage window of 2.0 to 4.0 V is 125.0 mAh / g. The high-temperature cycle diagram of NFM-1 is shown in Figure 15, revealing that after 100 cycles at 60°C, within a voltage window of 2.0 to 4.0 V, and at a 1C magnification, the capacity retention rate is 83%.

[0060] Comparative Example 2 In this embodiment, the chemical formula is NaNi 0.32 Fe 0.33 Mn 0.32 B 0.03 We provide a sodium ion battery positive electrode active material that is O2, and a method for manufacturing it. (1) A step of preparing a solution in which nickel sulfate, ferrous sulfate, and manganese sulfate are added to pure water in a Ni:Fe:Mn molar ratio of 1:1:1 to obtain a total concentration of metal elements of 1.3 mol / L. (2) A step of preparing a 4.0 mol / L sodium hydroxide solution and a 5.0 mol / L ammonia solution, (3) Add the metal salt solution obtained in step (1) and the sodium hydroxide solution and ammonia solution obtained in step (2) to the reactor at rates of 2.5 L / h, 1.5 L / h, and 0.2 L / h, respectively, and react for 12 hours at a reaction temperature of 50°C, a reaction pH of 11.5, and a stirring speed of 650 rpm to produce a precursor. (4) Wash the above precursor with pure water, filter it, dry it, and then Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 The process of obtaining (OH)2, (5) The process includes mixing a precursor, boric acid, and sodium carbonate in such a way that the total amount of metal elements in the precursor and the molar ratio of boron to sodium elements in sodium carbonate are 0.97:0.03:1, polishing the mixture, then sintering it in an atmospheric furnace at 850-1000°C for 12 hours, cooling it to below 80°C, jaw crushing, roller pairing, and grinding to obtain a sodium ion battery positive electrode active material (sample name is NFM-B5).

[0061] In this manufacturing method, water is not added during the polishing of the precursor, it is not manufactured in the form of a mixed slurry, and spray drying is not performed before sintering.

[0062] A scanning electron microscope image of NFM-B5 is shown in Figure 16, revealing that the material has a quasi-single crystal structure with an irregular shape. The XRD of NFM-B5 is shown in Figure 17, revealing that the material has a composite phase structure of P2 and O3. The charge-discharge curve of NFM-1 is shown in Figure 18, revealing that the discharge ratio capacity at a 0.1C magnification within a voltage window of 2.0 to 4.0 V is 125.0 mAh / g.

[0063] Performance Test Physical and chemical performance tests were performed on the positive electrode active materials produced in Examples 1-6 and Comparative Examples 1-2, and the results of the physical and chemical performance tests are shown in Table 1 below.

[0064] [Table 1]

[0065] The positive electrode active materials produced in Examples 1-6 and Comparative Examples 1-2 were used for sodium-ion battery performance tests. The sodium-ion battery was manufactured by weighing out 20g of the prepared positive electrode active material, adding 0.64g of conductive agent SP and 0.64g of NMP dissolved in PVDF, mixing uniformly, and then coating aluminum foil to produce an electrode sheet. A button cell was assembled in an argon-atmosphere glove box using metallic sodium flakes as the negative electrode, Celgard 2700 as the diaphragm, and 1 mol / L NaPF6+EC:DEC(1:1)+5%FEC as the electrolyte. 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.

[0066] [Table 2]

[0067] As can be seen from Tables 1 and 2 above, the present invention achieves the formation of a perfect layered single-crystal structure in the positive electrode active material by adding water during the polishing of the precursor to produce a mixed slurry, performing spray drying before sintering, and adding a boron-containing compound to the raw materials. Furthermore, the single-crystal particles grow large and densely packed, the compaction density of the positive electrode active material is clearly improved, the specific surface area is reduced, and, assuming that the positive electrode active material exhibits a high gram-to-capacity when used in a sodium-ion battery, the cycle performance at high temperatures is clearly improved.

[0068] The above embodiments are solely for the purpose of illustrating the technical idea and features of the present invention, and their purpose is to enable those familiar with this art to understand the content of the present invention and to implement it accordingly. This does not limit the scope of protection of the present invention, and any equivalent changes or modifications substantially made in accordance with the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a positive electrode active material for a single-crystal sodium ion battery containing the elements sodium, M metal, boron, and oxygen, The manufacturing method includes the steps of: adding water to an M-element-containing compound, a boron-element-containing compound, and a sodium source to produce a slurry; adding the slurry to a sand mill having an abrasive body inside; polishing the slurry for 0.6 to 7.8 hours at a rotational speed of 800 to 3000 rpm to polish the particles in the slurry to a median particle size of 20 to 800 nm to obtain a mixed slurry; The process includes spray-drying the mixed slurry and sintering it to obtain the single-crystal sodium-ion battery positive electrode active material. A method for producing a positive electrode active material for a single-crystal sodium-ion battery, characterized by the features described above.

2. The chemical formula of the positive electrode active material of the aforementioned single-crystal sodium ion battery is Na ｘ M ｙ B ｚ O ２ Here, M is one or more combinations selected from Li, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, W, Ta, Ba, Bi, La, Ce, Eu, and 0.80 ≤ x ≤ 1.40, 0.6 ≤ y ≤ 0.9999, and z = 0.03 or 0.

05. The manufacturing method according to claim 1, characterized in that it

3. The aforementioned M-element-containing compound is selected from one or more combinations of oxides, hydroxides, carbonates, oxalates, and nitrates of the M-element. The manufacturing method according to claim 1, characterized in that it

4. The boron-containing compound is selected from one or more combinations of boron oxide, boric acid, borate salts, borohydride salts, boron trihalides, trifluoroboric acid, borate esters, boranes, and metal borides. The manufacturing method according to claim 1, characterized in that it

5. The sodium source is sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxide. Selected from one or more combinations of thorium, sodium peroxide, sodium nitrate, sodium acetate, and sodium oxalate. The manufacturing method according to claim 1, characterized in that it

6. The molar ratio of the M-element-containing compound, the boron-containing compound, and the sodium source is (0.6 to 0.9999):(0.4 to 0.0001):(0.80 to 1.40). The manufacturing method according to claim 1, characterized in that it

7. The abrasive body is a zirconia sphere with a particle size of 0.1 to 0.8 mm. The manufacturing method according to claim 1, characterized in that it

8. The solid content of the mixed slurry is 10% to 60%. The manufacturing method according to claim 1, characterized in that it

9. In the case of the aforementioned spray drying, the rotation speed of the atomizer disc is 1000 to 3000 rpm, the intake air temperature is 150 to 300°C, and the discharge air temperature is 80 to 120°C. The manufacturing method according to claim 1, characterized in that it

10. The sintering is carried out in air, at a temperature of 750 to 1100°C for 5 to 25 hours, and / or the mixed slurry is pulverized after sintering. The manufacturing method according to claim 1, characterized in that it

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