Layered transition metal oxide positive electrode material of sodium-ion battery as well as preparation method and application of layered transition metal oxide positive electrode material

Abstract

The invention relates to a sodium-ion battery layered transition metal oxide positive electrode material and a preparation method and application thereof, and belongs to the technical field of battery materials. The method comprises the following steps: mixing and grinding an NFM hydroxide precursor and a sodium source according to a mass ratio of greater than 1.5 to form slurry; evaporating and crystallizing the slurry at 60 DEG C or above to obtain a precursor; pre-sintering the precursor for more than 1 hour at the temperature of more than 450 DEG C, then calcining for more than 10 hours at the temperature of more than 800 DEG C, and naturally cooling to obtain a black positive electrode material; crushing the material into small particles with the maximum particle diameter of not more than 10mm; and finally, carrying out jet milling and grinding to obtain the micron-sized sodium ferro-nickel manganate positive electrode material with the maximum particle diameter of not more than 10 [mu] m. The preparation of the high-performance layered transition metal oxide positive electrode material of the sodium-ion battery is realized through a multi-step accurately controlled preparation process, and the material has excellent electrochemical performance and is suitable for the field of sodium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and more particularly to a sodium ion battery layered transition metal oxide positive electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] Traditional coal-fired power generation severely pollutes the environment, making it difficult to meet the demand for "green, low-carbon" energy. Due to the uneven distribution and limited reserves of conventional fossil fuels such as coal and oil, energy costs have been rising. Consequently, there has been significant interest in the development and utilization of renewable energy. However, the unpredictable and uncontrollable nature of most renewable energy sources limits their practical application in power storage operations. Consequently, energy storage technology has received significant development and attention.

[0003] Technologies that store and convert energy electrochemically can be seen as an excellent solution to today's thorny energy challenges. With advantages such as high energy density, high output voltage, and long cycle life, lithium-ion batteries (LIBs) lead the industry in various electrochemical energy storage systems and are a key component of smartphones, laptops, cameras, and other portable electronic devices. However, due to the limited supply, high cost, and uneven distribution of lithium materials on Earth, new low-cost alternatives to lithium-ion batteries are essential.

[0004] Compared with lithium-ion batteries (LIBs), sodium (Na) has broad application prospects in the fields of smart grids and large-scale energy storage due to its abundant reserves and low price. And sodium-ion batteries (SIBs) operate using the same "rocking chair mechanism" as lithium-ion batteries (LIBs). Developing suitable sodium-ion storage electrode materials seems to be more challenging than studying lithium-ion storage electrode materials because the larger ionic radius of sodium causes the energy density of sodium-ion batteries to be lower than that of lithium-ion batteries. In sodium-ion batteries, positive electrode materials play a vital role in improving energy density. Therefore, exploring positive electrode materials with excellent reversible capacity and cycle performance is of great significance and strong demand for promoting sodium-ion batteries as a low-cost and sustainable grid energy storage device.

[0005] Various cathode materials have been extensively studied for sodium-ion batteries (SIBs), including polyanionic materials, Prussian blue compounds, and layered transition metal oxides. Among them, layered transition metal oxides (LTMOs) have attracted much attention due to their high theoretical capacity, low cost, and simple synthesis process.

[0006] Generally, LTMO is expressed as NaxTMO2 (0 < x ≤ 1, TM represents transition metal). These oxides consist of a transition metal oxide layer of (MO2)n, where sodium ions (Na+) are located between them for insertion. The (MO2)n layer is composed of edge-sharing MO6 octahedral units, and each transition metal ion is surrounded by six oxygen ions. Currently, layered oxides have been classified into four structural types according to the differences in sodium ion occupancy positions and oxygen stacking sequences: O3, O2, P2, and P3. In these structures, if the Na+ between LTMO occupies a prismatic or octahedral position, the material is called P-type or O-type LTMO respectively. The number represents the number of stacked oxide layers within a unit cell. Generally speaking, P-type oxides have a lower ionic diffusion barrier and a more stable structure, while O-type oxides have a higher sodium content and a larger charge-discharge capacity.

[0007] Combined with the above description, the layered transition metal oxide cathode materials mainly include two crystal structures: P2 type and O3 type. In the P2-type structure, sodium ions are located at the trigonal prism sites, while in the O3-type structure, sodium ions are located at the octahedral sites. Both of these structures will undergo phase changes of varying degrees during the charge-discharge process, affecting the electrochemical performance and cycle stability of the materials. CN119637955A discloses a preparation method for a sodium-ion layered oxide cathode material sodium nickel iron manganate. This method obtains the cathode material by mixing a sodium source with an alkali metal / alkaline earth metal carbonate and then mixing it with a Ni / Fe / Mn-based ternary precursor followed by high-temperature sintering. CN116986649A proposes a preparation method for a low-residual-alkali sodium-ion battery cathode material. By using a nickel iron manganese ternary precursor with a certain specific surface area and tap density and sintering it with a sodium source under the synergistic action of a flux, the surface residual alkali of the synthesized material can be significantly reduced.

[0008] In order to further improve the electrochemical performance of layered oxide cathode materials, researchers have tried various modification strategies. CN119370910A introduces a potassium rhenate-doped layered oxide sodium-ion battery cathode material. Through potassium rhenate doping and surface coating treatment, the specific capacity and cycle performance of the material are improved. CN116826033A discloses a preparation method for a sodium-ion battery layered cathode material Na （x） Ni 0.6 Co 0.1 Mn 0.2 O2. By means of ball milling and high-temperature sintering processes, the problem of difficult sodium ion insertion is solved. CN119170796A proposes a fluoride ion and rare earth metal ion co-doped P2-phase sodium-ion battery layered oxide cathode material, which has a high specific capacity and good cycle stability.

[0009] However, the existing layered transition metal oxide cathode materials for sodium-ion batteries still have some problems that need to be solved urgently. First, during the charge and discharge process, as sodium ions are continuously extracted, the transition metal layers will undergo relative sliding to reduce the influence of electrostatic repulsion, resulting in phase change and decreased electrochemical performance. Specifically, P2-type oxides usually undergo P2-O2 phase transition under high voltage, while O3-type oxides tend to undergo more complex phase transitions. In O3-type oxides, due to the sliding of the TMO2 layer, Na⁺ becomes stable at the prismatic site to form the so-called P3 phase. This structural transformation seriously affects the electrochemical properties of the material. Secondly, existing preparation methods often have problems such as complex processes, high energy consumption, and uneven reactions, making it difficult to achieve large-scale production of high-quality cathode materials. In addition, the particle morphology control and particle size distribution of the material also directly affect the electrochemical properties of the electrode material and the cycle life of the battery.

[0010] However, as sodium ions are continuously extracted, the transition metal layers will slide relative to each other to reduce the effect of electrostatic repulsion, resulting in phase change and a decrease in electrochemical performance. Among various layered oxides, P2 and O3 type materials have been widely studied. P2 type oxides usually undergo P2-O2 phase transition under high pressure, while O3 type oxides tend to undergo more complex phase transitions. In O3 type oxides, due to the sliding of the TMO2 layer, Na+ becomes stable at the prismatic site, thus forming the so-called P3 phase. This structural transformation leads to a decrease in the electrochemical performance of the cathode material. Therefore, it is of great significance to the development of a sodium ion battery positive electrode material with high capacity and good cycle performance by introducing suitable element species and proportions through a preparation method for the development of sodium ion batteries. Summary of the Invention

[0011] In order to solve the technical problem that the existing sodium ion battery layered transition metal oxide positive electrode material undergoes phase change during the charge and discharge process, resulting in a decrease in electrochemical performance, and to achieve the technical effects of high capacity and excellent cycle performance, the present invention provides a high-performance sodium ion battery layered transition metal oxide positive electrode material and its preparation method and application, to solve the problems raised in the above background technology.

[0012] To achieve the above objectives, the present invention is implemented through the following technical means: In a first aspect, the present invention discloses a method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Step 2: evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried positive electrode material precursor; Step 3: Sintering the precursor material at high temperature and then cooling it naturally to obtain a black sodium ion battery layered oxygen cathode material; Step 4, crushing the calcined positive electrode material to obtain powdered small particles; Step 5: Grind the small particles by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0013] In some embodiments, the mass ratio of the NFM hydroxide precursor to the sodium source in step 1 is greater than 1.5.

[0014] In some embodiments, in step 1, the grinding method is sand milling or ball milling, and the mixed grinding is used to achieve particle pulverization, crushing or atomic separation in the form of shear force, gravity, and friction.

[0015] In some embodiments, the sodium source in step 1 can be one of sodium carbonate, sodium bicarbonate or sodium hydroxide.

[0016] In some embodiments, the drying temperature in step 2 is greater than 60°C.

[0017] In some embodiments, in step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period to ensure sufficient crystallization growth of the material. After naturally cooling to room temperature, the final high-performance sodium ion battery layered transition metal oxide positive electrode material is obtained, wherein the first temperature is greater than 450°C and the first time period is greater than 1 hour.

[0018] In some embodiments, in step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period to ensure sufficient crystallization growth of the material. After naturally cooling to room temperature, the final high-performance sodium ion battery layered transition metal oxide positive electrode material is obtained, wherein the second temperature is greater than 800°C and the second time period is greater than 10 hours.

[0019] In some embodiments, in step 4, the crushing method is mechanical grinding, air flow grinding or jaw crusher crushing, and the above crushing methods achieve the purpose of material pulverization in the form of shear force, and the maximum particle diameter Dmax in the powder is ≤10mm.

[0020] In some embodiments, the crushing method in step 5 is mechanical grinding, air flow grinding or jaw crusher crushing, and the above crushing methods achieve the purpose of material pulverization in the form of shear force, and the maximum particle diameter Dmax in the powder is ≤10um.

[0021] In a second aspect, the present invention discloses a layered transition metal oxide positive electrode material for a sodium ion battery, which is prepared using the above-mentioned preparation process.

[0022] In a third aspect, the present invention also discloses the application of the method described in the above technical solution in the preparation of sodium ion batteries.

[0023] In a fourth aspect, the present invention further discloses a sodium ion battery, which contains a sodium ion battery layered transition metal oxide positive electrode material prepared by the method described in the above technical solution.

[0024] Compared with the prior art, the present invention has the following beneficial effects: By precisely controlling the molar ratio of the three transition metals nickel, iron, and manganese, this invention successfully prepared a layered NaxTMO2 (TM = Ni, Fe, Mn) ternary cathode material. This effectively addresses the problem of phase transitions during charge and discharge in existing layered transition metal oxide cathode materials for sodium-ion batteries, which can lead to decreased electrochemical performance. Compared to existing technologies, the cathode material prepared in this invention maintained a reversible capacity of approximately 130 mAh / g in cycling tests at a rate of 1C (120 mA / g), with a capacity retention of 100% after 50 cycles, demonstrating excellent cycling stability. Furthermore, the preparation process of this invention offers significant industrial advantages: the raw materials used are all commercially available, with the nickel-iron-manganese hydroxide precursor already commercially available, and the sodium source materials are all basic chemical products with a mature and stable supply chain. The prepared layered oxide cathode material has been validated in soft-pack batteries and demonstrates excellent commercial application prospects. It provides a cost-effective and process-simplified solution for sodium-ion battery cathode materials, aligning with the development trend of green manufacturing and poised for large-scale industrialization. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is the X-ray powder diffraction test pattern of the high-performance sodium ion battery layered transition metal oxide positive electrode material prepared in Example 1.

[0025] Figure 2 This is a scanning electron microscope test image of the high-performance sodium ion battery layered transition metal oxide positive electrode material prepared in Example 1.

[0026] Figure 3 This is a constant current charge and discharge curve diagram of the high-performance sodium ion battery layered transition metal oxide positive electrode material prepared in Example 1. DETAILED DESCRIPTION The following detailed description of the embodiments of the technical solution of this application is provided in conjunction with the accompanying drawings. The following embodiments and drawings are intended only to more clearly illustrate the technical solution of this application and are therefore provided as examples only and are not intended to limit the scope of protection of this application. The accompanying drawings schematically illustrate only the parts relevant to the technical solution of this application and do not represent the actual structure of the product.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0028] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two), and "multiple pieces" refers to more than two (including two).

[0029] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0031] In this embodiment, in a first aspect, the present invention discloses a method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Step 2: evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried positive electrode material precursor; Step 3: Sintering the precursor material at high temperature and then cooling it naturally to obtain a black sodium ion battery layered oxygen cathode material; Step 4, crushing the calcined positive electrode material to obtain powdered small particles; Step 5: Grind the small particles by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0032] In some embodiments, the mass ratio of the NFM hydroxide precursor to the sodium source in step 1 is greater than 1.5.

[0033] In some embodiments, in step 1, the grinding method is sand milling or ball milling, and the mixed grinding is used to achieve particle pulverization, crushing or atomic separation in the form of shear force, gravity, and friction.

[0034] In some embodiments, the sodium source in step 1 can be one of sodium carbonate, sodium bicarbonate or sodium hydroxide.

[0035] In some embodiments, the drying temperature in step 2 is greater than 60°C.

[0036] In some embodiments, in step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period to ensure sufficient crystallization growth of the material. After naturally cooling to room temperature, the final high-performance sodium ion battery layered transition metal oxide positive electrode material is obtained, wherein the first temperature is greater than 450°C and the first time period is greater than 1 hour.

[0037] In some embodiments, in step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period to ensure sufficient crystallization growth of the material. After naturally cooling to room temperature, the final high-performance sodium ion battery layered transition metal oxide positive electrode material is obtained, wherein the second temperature is greater than 800°C and the second time period is greater than 10 hours.

[0038] In some embodiments, in step 4, the crushing method is mechanical grinding, air flow grinding or jaw crusher crushing, and the above crushing methods achieve the purpose of material pulverization in the form of shear force, and the maximum particle diameter Dmax in the powder is ≤10mm.

[0039] In some embodiments, the crushing method in step 5 is mechanical grinding, air flow grinding or jaw crusher crushing, and the above crushing methods achieve the purpose of material pulverization in the form of shear force, and the maximum particle diameter Dmax in the powder is ≤10um.

[0040] In a second aspect, the present invention discloses a layered transition metal oxide positive electrode material for a sodium ion battery, which is prepared using the above-mentioned preparation process.

[0041] In a third aspect, the present invention also discloses the application of the method described in the above technical solution in the preparation of sodium ion batteries.

[0042] In a fourth aspect, the present invention further discloses a sodium ion battery, which contains a sodium ion battery layered transition metal oxide positive electrode material prepared by the method described in the above technical solution.

[0043] By precisely controlling the molar ratio of the three transition metals nickel, iron, and manganese, a layered NaxTMO2 (TM = Ni, Fe, Mn) ternary cathode material was successfully prepared. This effectively addresses the issue of phase transitions during charge and discharge in existing layered transition metal oxide cathode materials for sodium-ion batteries, which can lead to decreased electrochemical performance. Compared to existing technologies, the cathode material prepared in this invention maintains a reversible capacity of approximately 130 mAh / g in cycling tests at a rate of 1C (120 mA / g), with a capacity retention of 100% after 50 cycles, demonstrating excellent cycling stability. Furthermore, the preparation process of this invention offers significant advantages for industrialization: the raw materials used are all commercially available, including the nickel-iron-manganese hydroxide precursor, which has achieved industrial mass production. The sodium source materials are all basic chemical products with a mature and stable supply chain. The prepared layered oxide cathode material has been validated in soft-pack batteries and demonstrates excellent commercial application prospects. It provides a cost-effective and process-simplified solution for sodium-ion battery cathode materials, aligning with the development trend of green manufacturing and poised for large-scale industrialization.

[0044] Example 1 A high-performance sodium ion battery layered transition metal oxide positive electrode material and a preparation method thereof, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Specifically, take an appropriate amount of NFM hydroxide precursor, which is a mixed hydroxide of nickel, iron and manganese, wherein the molar ratio of nickel, iron and manganese is 3:3:4. Sodium carbonate is weighed as a sodium source, and the mass ratio of the NFM hydroxide precursor to the sodium source is 2.0. The weighed NFM hydroxide precursor and sodium carbonate are placed in a ball mill, and an appropriate amount of anhydrous ethanol is added as a dispersion medium, and mixed grinding is carried out using a ball mill. During the ball milling process, the particles are pulverized, crushed and separated between atoms through the action of shear force, gravity and friction, so that the NFM hydroxide precursor and the sodium source are fully mixed to form a uniform slurry. The ball milling time is 4 hours, and the ball milling speed is 300 rpm.

[0045] Step 2: Evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried cathode material precursor; Specifically, the slurry obtained in step 1 was poured into an evaporating dish and dried in an oven at 80°C for 12 hours to completely evaporate the alcohol and achieve solid-liquid separation. The resulting material after drying was a uniform, fine powder with a light brown color.

[0046] Step 3: Sintering the precursor material obtained in the previous step at a high temperature and then cooling it naturally to obtain a black sodium ion battery layer oxygen cathode material; Specifically, the precursor material obtained in step 2 is placed in an alumina crucible and first pre-fired at 500°C in a muffle furnace for 2 hours to remove residual organic matter and moisture in the precursor. After the pre-fire is completed, the temperature is raised to 900°C for calcination, and the holding time is 15 hours to ensure sufficient crystal growth of the material. After the calcination is completed, the muffle furnace power is turned off and the material is allowed to cool naturally to room temperature in the furnace to obtain a black sodium ion battery layered transition metal oxide positive electrode material.

[0047] Step 4: crushing the calcined positive electrode material to obtain powdered small particles; Specifically, the black cathode material obtained in step 3 was removed and initially crushed using a mechanical mill. The mill pulverized the material through shear force, keeping the maximum particle diameter (Dmax) below 5 mm. The crushing process was intermittent, with each crushing cycle lasting 30 seconds followed by a 10-second pause, and repeated 10 times to avoid localized overheating of the material due to excessive grinding.

[0048] Step 5: Grind the small particles obtained in the previous step by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0049] Specifically, the small particles obtained in step 4 are placed in a jet mill for fine grinding. The jet mill uses the shear force generated by the high-speed airflow to further pulverize the particles, ultimately obtaining a micron-sized, high-performance sodium ion battery layered transition metal oxide positive electrode material, sodium nickel iron manganese oxide. The maximum particle diameter Dmax in the ground powder is controlled to be below 5 μm, and the average particle size is 2 μm. The airflow pressure during the grinding process is controlled at 0.6 MPa, and the grinding time is 30 minutes.

[0050] The sodium nickel iron manganese oxide cathode material prepared through the above steps exhibits excellent crystallinity and uniform particle size distribution, with a specific surface area of ​​15 m² / g and a tap density of 2.3 g / cm³. As a sodium-ion battery cathode material, this material achieves an initial discharge capacity of 160 mAh / g at a 0.1C rate, and maintains a capacity retention of over 85% after 100 cycles, demonstrating excellent electrochemical performance.

[0051] Example 2 A high-performance sodium ion battery layered transition metal oxide positive electrode material and a preparation method thereof, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Specifically, take an appropriate amount of NFM hydroxide precursor, which is a mixed hydroxide of nickel, iron and manganese, wherein the molar ratio of nickel, iron and manganese is 2:4:4. Sodium bicarbonate is weighed as a sodium source, and the mass ratio of the NFM hydroxide precursor to the sodium source is 1.8. The weighed NFM hydroxide precursor and sodium bicarbonate are placed in a sand mill, and an appropriate amount of isopropanol is added as a dispersion medium, and mixed and ground using a sand mill. During the sand milling process, the particles are pulverized, crushed and separated between atoms through the action of shear force, gravity and friction, so that the NFM hydroxide precursor and the sodium source are fully mixed to form a uniform slurry. The sand milling time is 3 hours, and the sand milling speed is 250 rpm.

[0052] Step 2: Evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried cathode material precursor; Specifically, the slurry obtained in step 1 was poured into an evaporating dish and dried in an oven at 70°C for 10 hours to completely evaporate the isopropyl alcohol and achieve solid-liquid separation. The resulting material after drying was a uniform, fine powder with a light brown color.

[0053] Step 3: Sintering the precursor material obtained in the previous step at a high temperature and then cooling it naturally to obtain a black sodium ion battery layer oxygen cathode material; Specifically, the precursor material obtained in step 2 is placed in an alumina crucible and first pre-fired at 480°C in a muffle furnace for 1.5 hours to remove residual organic matter and moisture in the precursor. After the pre-fire is completed, the temperature is raised to 850°C for calcination, and the holding time is 12 hours to ensure sufficient crystal growth of the material. After the calcination is completed, the muffle furnace power is turned off and the material is allowed to cool naturally to room temperature in the furnace to obtain a black sodium ion battery layered transition metal oxide positive electrode material.

[0054] Step 4: crushing the calcined positive electrode material to obtain powdered small particles; Specifically, the black cathode material obtained in step 3 was removed and initially crushed using a jaw crusher. The jaw crusher pulverizes the material through shear force, keeping the maximum particle diameter (Dmax) below 8 mm. The crushing process was intermittent, with each crushing cycle lasting 20 seconds followed by a 15-second pause, repeated eight times to avoid localized overheating of the material due to excessive grinding.

[0055] Step 5: Grind the small particles obtained in the previous step by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0056] Specifically, the small particles obtained in step 4 are placed in a jet mill for fine grinding. The jet mill uses the shear force generated by the high-speed airflow to further pulverize the particles, ultimately obtaining a micron-sized, high-performance sodium ion battery layered transition metal oxide positive electrode material, sodium nickel iron manganese oxide. The maximum particle diameter Dmax in the ground powder is controlled to be less than 8μm, and the average particle size is 3μm. The airflow pressure during the grinding process is controlled at 0.5MPa, and the grinding time is 25 minutes.

[0057] The sodium nickel iron manganese oxide cathode material prepared through the above steps exhibits excellent crystallinity and uniform particle size distribution, with a specific surface area of ​​18 m² / g and a tap density of 2.1 g / cm³. As a sodium-ion battery cathode material, this material achieves an initial discharge capacity of 155 mAh / g at a 0.1C rate, and maintains a capacity retention of over 82% after 100 cycles, demonstrating excellent electrochemical performance.

[0058] Example 3 A high-performance sodium ion battery layered transition metal oxide positive electrode material and a preparation method thereof, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Specifically, an appropriate amount of NFM hydroxide precursor is used, which is a mixed hydroxide of nickel, iron and manganese, wherein the molar ratio of nickel, iron and manganese is 4:2:4. Sodium hydroxide is weighed as a sodium source, and the mass ratio of the NFM hydroxide precursor to the sodium source is 1.6. The weighed NFM hydroxide precursor and sodium hydroxide are placed in a ball mill, and an appropriate amount of methanol is added as a dispersion medium, and mixed and ground using a ball mill. During the ball milling process, the particles are pulverized, crushed and separated between atoms through the action of shear force, gravity and friction, so that the NFM hydroxide precursor and the sodium source are fully mixed to form a uniform slurry. The ball milling time is 5 hours, and the ball milling speed is 350 rpm.

[0059] Step 2: Evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried cathode material precursor; Specifically, the slurry obtained in step 1 was poured into an evaporating dish and dried in an oven at 65°C for 15 hours to completely evaporate the methanol and achieve solid-liquid separation. The resulting material after drying was a uniform, fine powder with a light brown color.

[0060] Step 3: Sintering the precursor material obtained in the previous step at a high temperature and then cooling it naturally to obtain a black sodium ion battery layer oxygen cathode material; Specifically, the precursor material obtained in step 2 is placed in an alumina crucible and first pre-fired at 550°C in a muffle furnace for 3 hours to remove residual organic matter and moisture in the precursor. After the pre-fire is completed, the temperature is raised to 950°C for calcination, and the holding time is 18 hours to ensure sufficient crystal growth of the material. After the calcination is completed, the muffle furnace power is turned off and the material is allowed to cool naturally to room temperature in the furnace to obtain a black sodium ion battery layered transition metal oxide positive electrode material.

[0061] Step 4: crushing the calcined positive electrode material to obtain powdered small particles; Specifically, the black cathode material obtained in step 3 was removed and initially crushed using a mechanical mill. The mill pulverized the material through shear force, keeping the maximum particle diameter (Dmax) below 3 mm. The crushing process was intermittent, with each crushing cycle lasting 40 seconds followed by a 20-second pause, repeated 12 times to avoid localized overheating of the material due to excessive grinding.

[0062] Step 5: Grind the small particles obtained in the previous step by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0063] Specifically, the small particles obtained in step 4 are placed in a jet mill for fine grinding. The jet mill uses the shear force generated by the high-speed airflow to further pulverize the particles, ultimately obtaining a micron-sized, high-performance sodium ion battery layered transition metal oxide positive electrode material, sodium nickel iron manganese oxide. The maximum particle diameter Dmax in the ground powder is controlled to be less than 3 μm, and the average particle size is 1 μm. The airflow pressure during the grinding process is controlled at 0.7 MPa, and the grinding time is 40 minutes.

[0064] The sodium nickel iron manganese oxide cathode material prepared through the above steps exhibits excellent crystallinity and uniform particle size distribution, with a specific surface area of ​​22 m² / g and a tap density of 2.5 g / cm³. As a sodium-ion battery cathode material, this material achieves an initial discharge capacity of 170 mAh / g at a 0.1C rate, and maintains a capacity retention of over 88% after 100 cycles, demonstrating excellent electrochemical performance.

[0065] Example 4 A high-performance sodium ion battery layered transition metal oxide positive electrode material and a preparation method thereof, comprising the following steps: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Specifically, take an appropriate amount of NFM hydroxide precursor, which is a mixed hydroxide of nickel, iron and manganese, wherein the molar ratio of nickel, iron and manganese is 3:4:3. Sodium carbonate is weighed as a sodium source, and the mass ratio of the NFM hydroxide precursor to the sodium source is 2.2. The weighed NFM hydroxide precursor and sodium carbonate are placed in a ball mill, and an appropriate amount of anhydrous ethanol is added as a dispersion medium, and mixed grinding is carried out using a ball mill. During the ball milling process, the particles are pulverized, crushed and separated between atoms through the action of shear force, gravity and friction, so that the NFM hydroxide precursor and the sodium source are fully mixed to form a uniform slurry. The ball milling time is 6 hours, and the ball milling speed is 280 rpm.

[0066] Step 2: Evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried cathode material precursor; Specifically, the slurry obtained in step 1 was poured into an evaporating dish and dried in an oven at 90°C for 8 hours to completely evaporate the ethanol and achieve solid-liquid separation. The resulting material after drying was a uniform, fine powder with a light brown color.

[0067] Step 3: Sintering the precursor material obtained in the previous step at a high temperature and then cooling it naturally to obtain a black sodium ion battery layer oxygen cathode material; Specifically, the precursor material obtained in step 2 is placed in an alumina crucible and first pre-fired at 520°C in a muffle furnace for 2.5 hours to remove residual organic matter and moisture in the precursor. After the pre-fire is completed, the temperature is raised to 880°C for calcination, and the holding time is 14 hours to ensure sufficient crystal growth of the material. After the calcination is completed, the muffle furnace power is turned off and the material is allowed to cool naturally to room temperature in the furnace to obtain a black sodium ion battery layered transition metal oxide positive electrode material.

[0068] Step 4: crushing the calcined positive electrode material to obtain powdered small particles; Specifically, the black cathode material obtained in step 3 was removed and initially crushed using a jet mill. The jet mill pulverizes the material through shear force, and the maximum particle diameter Dmax of the crushed powder is controlled to be less than 7 mm. The airflow pressure during the crushing process is controlled at 0.4 MPa, and the crushing time is 15 minutes.

[0069] Step 5: Grind the small particles obtained in the previous step by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

[0070] Specifically, the small particles obtained in step 4 are placed in a jet mill for fine grinding. The jet mill uses the shear force generated by the high-speed airflow to further pulverize the particles, ultimately obtaining a micron-sized, high-performance sodium ion battery layered transition metal oxide positive electrode material, sodium nickel iron manganese oxide. The maximum particle diameter Dmax in the ground powder is controlled to be less than 6 μm, and the average particle size is 2.5 μm. The airflow pressure during the grinding process is controlled at 0.6 MPa, and the grinding time is 35 minutes.

[0071] The sodium nickel iron manganese oxide cathode material prepared through the above steps exhibits excellent crystallinity and uniform particle size distribution, with a specific surface area of ​​16 m² / g and a tap density of 2.2 g / cm³. As a sodium-ion battery cathode material, this material achieves an initial discharge capacity of 158 mAh / g at a 0.1C rate, and maintains a capacity retention of over 83% after 100 cycles, demonstrating excellent electrochemical performance.

[0072] It should be noted that Example 1, Example 2, Example 3, and Example 4 are all a type of high-performance sodium ion battery layered transition metal oxide positive electrode material and a preparation method thereof.

[0073] The present invention is further described below with reference to specific experimental examples.

[0074] Experimental Example 1 (1) After weighing NFM111 hydroxide precursor and sodium carbonate at a mass ratio of 1.62, add them into 200 mL of anhydrous alcohol and stir by ball milling for 120 min to obtain a uniform mixed solution; (2) placing the slurry obtained in step (1) in a forced air drying oven at 80°C for evaporation and crystallization to obtain a brown powder with uniform color; (3) The powder obtained in step (2) was placed in a crucible and pre-fired at 500°C, kept at this temperature for 2 hours, and a heating rate of 2°C / min, and then heated to 850°C and kept at this temperature for 15 hours. After naturally cooling to room temperature, a black high-performance layered transition metal oxide positive electrode material for sodium ion batteries was obtained; (4) The bulk sodium ion battery layer oxygen cathode material obtained in step (3) is preliminarily crushed, and the maximum particle diameter Dmax in the powder is 10 mm.

[0075] (5) The cathode material after the initial crushing in step (4) is crushed again by a jet mill, and the maximum particle diameter Dmax in the powder is 4 μm, thereby obtaining the final high-performance sodium ion battery layered transition metal oxide cathode material NaNi 0.33 Fe 0.33 Mn 0.33 O2.

[0076] Experimental Example 2 (1) After weighing NFM424 hydroxide precursor and sodium carbonate in a mass ratio of 1.62, add them into 200 mL of anhydrous alcohol and stir by ball milling for 120 min to obtain a uniform mixed solution; (2) placing the slurry obtained in step (1) in a forced air drying oven at 80°C for evaporation and crystallization to obtain a brown powder with uniform color; (3) The powder obtained in step (2) was placed in a crucible and pre-fired at 500°C, kept at this temperature for 2 hours, and a heating rate of 2°C / min, and then heated to 850°C and kept at this temperature for 15 hours. After naturally cooling to room temperature, a black high-performance layered transition metal oxide positive electrode material for sodium ion batteries was obtained; (4) The bulk sodium ion battery layer oxygen cathode material obtained in step (3) is preliminarily crushed, and the maximum particle diameter Dmax in the powder is 10 mm.

[0077] (5) The cathode material after the initial crushing in step (4) is crushed again by a jet mill, and the maximum particle diameter Dmax in the powder is 4 μm, thereby obtaining the final high-performance sodium ion battery layered transition metal oxide cathode material NaNi 0.4 Fe 0.2 Mn 0.4 O2.

[0078] Performance testing: (1) XRD test: The high performance sodium ion battery layered transition metal oxide positive electrode material NaNi prepared in Example 1 above was 0.33 Fe 0.33 Mn 0.33 O2 was tested by XRD, as shown in the attached Figure 1 shown.

[0079] (2) SEM test: The positive electrode material NaNi 0.33 Fe 0.33 Mn 0.33 O2 was observed under a scanning electron microscope, as shown in the attached Figure 2 .

[0080] (3) Electrochemical performance test: The prepared powder material, conductive agent and binder were mixed in a ratio of 7:2:1 and coated on aluminum foil with a coating thickness of 150 μm. After drying, the electrodes were cut into electrodes with a diameter of 12 mm. The electrodes were assembled in the glove box in the order of positive electrode shell, positive electrode sheet, electrolyte, diaphragm, negative electrode, gasket, shrapnel and negative electrode shell. The counter electrode was sodium metal and the electrolyte was 1M NaCIO4 (PC+5% FEC). The electrochemical performance test was carried out. Figure 3As shown, it was cycled at a rate of 1C (120mA / g), and it was found that it could maintain a reversible capacity of about 130mAh / g at a high rate, and the capacity retention rate was 100% after 50 cycles. This shows that the present invention has significantly improved the material performance to a certain extent.

[0081] The specific embodiments disclosed in the present invention fall within the scope of protection of the claims of the present invention and are the specific lower implementation scope of the characteristic part of the present invention. The protection content of the specific embodiments is only an explanation of the protection scope of the claims of the present invention. The protection scope of the present invention is not limited to the protection content of the specific embodiments, and the protection content of the specific embodiments should not be understood as limiting the protection scope of the claims of the present invention. The product structure connection relationship that falls within the protection scope of the present invention falls within the protection content of the present invention; without departing from the protection essence of the present invention, conventional technical improvements to the structure of product components, such as improvements to the product structure in the specific embodiments of the present invention, will also fall within the protection essence of the present invention.

Claims

1. A method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery, characterized in that: The following steps are involved: Step 1: Mix and grind the NFM hydroxide precursor, sodium source and alcohol to form a uniform slurry; Step 2: evaporating and crystallizing the slurry to achieve solid-liquid separation to obtain a uniformly dried positive electrode material precursor; Step 3: Sintering the precursor material at high temperature and then cooling it naturally to obtain a black sodium ion battery layered oxygen cathode material; Step 4, crushing the calcined positive electrode material to obtain powdered small particles; Step 5: Grind the small particles by air flow to obtain micron-sized high-performance sodium ion battery layered transition metal oxide positive electrode material sodium nickel iron manganese oxide.

2. The method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery according to claim 1, wherein: In step 1, the mass ratio of the NFM hydroxide precursor to the sodium source is greater than 1.

5.

3. The method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery according to claim 1, wherein: The sodium source in step 1 can be one of sodium carbonate, sodium bicarbonate or sodium hydroxide.

4. The method for preparing a layered transition metal oxide positive electrode material for a sodium ion battery according to claim 1, wherein: The drying temperature in step 2 is greater than 60°C.

5. The method for preparing a layered transition metal oxide positive electrode material for sodium ion batteries according to claim 1, wherein: The mass ratio of the main material hard carbon to water in step 4 is greater than 1.0, and the time of dispersion and stirring in step 4 is not less than 2 hours.

6. The method for preparing a layered transition metal oxide cathode material for sodium ion batteries according to claim 1, wherein: In the step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period. After naturally cooling to room temperature, the first temperature is greater than 450°C and the first time period is greater than 1 hour. In the step 3, the dried precursor material is pre-fired at a first temperature and kept warm for a first time period, and then calcined at a second temperature and kept warm for a second time period. After naturally cooling to room temperature, the second temperature is greater than 800°C and the second time period is greater than 10 hours.

7. The method for preparing a layered transition metal oxide cathode material for sodium ion batteries according to claim 1, wherein: In the step 4, the crushing method is mechanical grinding, air flow grinding or jaw crusher crushing, and the maximum particle diameter Dmax in the powder is ≤10mm; in the step 5, the maximum particle diameter Dmax in the powder is ≤10um.

8. A layered transition metal oxide cathode material for a sodium ion battery, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the preparation method according to any one of claims 1 to 7 in the preparation of sodium ion batteries.

10. A sodium ion battery, characterized in that: The sodium ion battery contains a sodium ion battery layered transition metal oxide positive electrode material prepared by the method according to any one of claims 1 to 7.

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