A ferronickel powder, a preparation method thereof and application thereof

Abstract

The application discloses a kind of nickel-iron powder and its preparation method and application, belong to nickel-iron alloy technical field.The nickel-iron powder includes +2 valence nickel and +3 valence iron, in XPS test, the atomic ratio sample standard deviation of nickel and iron is 0.01~0.05, the sample standard deviation s1 of the relative percentage content of +2 valence nickel in nickel element is not more than 10%, and the sample standard deviation s2 of the relative percentage content of +3 valence iron in iron element is not more than 10%.The nickel-iron powder is not easy to absorb moisture and cake during storage, can maintain free-flowing characteristics for a long time and has good acid leaching efficiency.The preparation method includes: nickel-iron alloy smelting, atomization, drying and oxidation.The method is simple and easy to operate, and can be industrialized.The above-mentioned nickel-iron powder can be used for preparing battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of nickel-iron alloy technology, and more specifically, to a nickel-iron powder, its preparation method, and its application. Background Technology

[0002] With the rise of the new energy industry, especially the popularization of lithium-ion batteries, the demand for lithium nickel cobalt manganese oxide and lithium iron phosphate, which are the cathode materials of lithium-ion batteries, is gradually increasing. The demand for their corresponding raw material elements, such as nickel and iron, is also increasing. Nickel-iron alloy obtained from nickel ore can meet the needs of obtaining nickel and iron elements at the same time.

[0003] Currently, acid leaching is commonly used to extract nickel and iron from nickel-iron alloys to obtain the desired nickel and iron elements. To increase the acid dissolution rate, large chunks of nickel-iron alloy raw materials are often processed into powder. However, due to their increased specific surface area, powdered nickel-iron easily absorbs moisture from the air during storage, tending to agglomerate or clump. As the powder size decreases, the tendency to clump and become damp increases, hindering the free flow of the powder. After absorbing moisture, fine nickel-iron powder will aggregate due to the bridging effect of moisture, forming large clumps of powder, affecting subsequent processes such as conveying and acid leaching. Furthermore, large clumps of powder are detrimental to acid leaching efficiency.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a nickel-iron powder, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a nickel-iron powder, which includes +2 valent nickel and +3 valent iron. In XPS testing, the sample standard deviation of the atomic ratio of nickel to iron is 0.01 to 0.05, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in nickel element does not exceed 10%, and the sample standard deviation s2 of the relative percentage content of +3 valent iron in iron element does not exceed 10%.

[0007] In an optional implementation, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in the XPS test is 0.5% to 10%; And / or, the sample standard deviation (s²) of the relative percentage of +3 valent iron in iron is 0.5% to 8%; And / or, the sample standard deviation s3 of the ratio of the relative percentage of +3 valent iron to the relative percentage of +2 valent iron in iron is 0.015 to 0.2.

[0008] In an optional embodiment, the nickel-iron powder also has at least one of the following characteristics: Feature 1: In XPS testing, the atomic ratio of nickel to iron is 0.3~0.5; Feature 2: In XPS testing, the relative percentage of +2 valent nickel in the nickel element is 40%~95%; Feature 3: In XPS testing, the relative percentage of +3 valent iron in the iron element is 40%~75%; Feature 4: In XPS testing, the relative percentage of +2 valent iron in the iron element is 20%~45%; Feature 5: In XPS testing, the ratio of the relative percentage of +3 valent iron to the relative percentage of +2 valent iron in iron is 1~2.8; Feature 6: The tap density of the nickel-iron powder is 3.3 g / cm³. 3 ~4.5g / cm 3 .

[0009] Feature 7: The particle size of the nickel-iron powder is 70μm~200μm; Feature 8: The water absorption rate of nickel-iron powder does not exceed 5.2%; Feature 9: The acid leaching efficiency of nickel-iron powder is not less than 80%.

[0010] Secondly, the present invention provides a method for preparing nickel-iron powder as described in any of the foregoing embodiments, comprising the following steps: melting a nickel-iron alloy to obtain a nickel-iron liquid; atomizing the nickel-iron liquid to obtain a slurry; and drying and oxidizing the slurry.

[0011] In an optional embodiment, the molten nickel-iron is mixed at 1650°C to 1750°C before atomization.

[0012] In an optional implementation, atomization is achieved using a coaxial double-layer annular slit nozzle, with the outermost annular slit serving as the high-pressure gas outlet, the middle annular slit serving as the high-pressure water outlet, and the inner hole serving as the melt outlet.

[0013] In an optional embodiment, the coaxial double-layer annular slit nozzle has at least one of the following features: Feature 10: The melt flow outlet diameter is 10mm~15mm; Feature 11: The high-pressure water flow outlet slit is 0.5mm~0.8mm; Feature 12: The high-pressure gas outlet slit is 1mm~2mm; Feature 13: The gas, water and melt all form an impact angle of 15°~30°.

[0014] In an optional embodiment, the gas is a mixture of inert gas and hydrogen, with the inert gas accounting for 96.5% to 98% by volume and the remainder being hydrogen.

[0015] In an optional implementation, the atomization conditions include at least one of the following characteristics: Feature 14: Melt flow rate is 0.5 kg / s to 1.0 kg / s; Feature 15: Water pressure is 8MPa~15MPa; Feature 16: Water temperature is 70℃~85℃; Feature 17: Water flow rate is 140m³ 3 / h~160m 3 / h; Feature 18: Gas pressure is 1.0 MPa to 2.5 MPa; Feature 19: Gas flow rate is 100m / s~150m / s.

[0016] In an optional embodiment, oxidation includes: drying at 100°C to 120°C for 25 to 35 minutes under a protective atmosphere, then introducing oxygen at 0.5% to 1% of the protective gas and treating at 150°C to 250°C for 5 to 15 minutes.

[0017] Thirdly, the present invention provides an application of nickel-iron powder as described in any of the foregoing embodiments, wherein the nickel-iron powder is used to prepare battery cathode materials.

[0018] The beneficial effects of this invention include: This invention creatively proposes a nickel-iron powder that is not prone to moisture absorption or clumping during storage, maintains free-flowing characteristics even after long-term storage, and has good acid leaching efficiency. The nickel-iron powder includes +2 valent nickel and +3 valent iron. In XPS testing, the sample standard deviation of the atomic ratio of nickel to iron is 0.01~0.05, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in nickel element does not exceed 10%, and the sample standard deviation s2 of the relative percentage content of +3 valent iron in iron element does not exceed 10%.

[0019] Nickel-iron powder meeting the above characteristics exhibits nickel and iron in oxidation states on its surface, with these oxidation states evenly distributed, indicating the presence of a uniform metal oxide layer on the surface. This uniform oxide layer reduces the differences in surface active sites, decreasing the nickel-iron powder's sensitivity to humidity changes. Furthermore, the passivation film formed by the uniform oxide layer possesses high density and chemical stability, effectively inhibiting contact between the metal substrate and moisture in the environment. Disordered or uneven oxide layers often contain defects (such as microcracks and pores), which can actually accelerate moisture absorption and corrosion. In addition, the uniform oxide layer acts as a physical barrier, reducing direct contact between airborne water molecules and the metal substrate, slowing the rate of water molecule diffusion into the interior. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the atomization system involved in the atomization process of the present invention; Figure 2 This is a bottom view schematic diagram of the coaxial double-layer annular slit nozzle used in the atomization process of this invention; Figure 3 The image shows the XPS plot of the nickel-iron powder obtained in Example 1.

[0022] Icons: 1-Inner hole; 2-Middle layer; 3-Outermost layer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] The following is a detailed description of the nickel-iron powder, its preparation method, and its applications provided by this invention.

[0025] This invention provides a nickel-iron powder comprising +2 valent nickel and +3 valent iron. In XPS testing, the sample standard deviation of the atomic ratio of nickel to iron is 0.01~0.05, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in nickel element does not exceed 10%, and the sample standard deviation s2 of the relative percentage content of +3 valent iron in iron element does not exceed 10%.

[0026] XPS stands for X-ray photoelectron spectroscopy, which can measure the surface composition of nickel-iron powder. The nickel-iron powder of the present invention has the composition as shown above, as obtained by XPS testing.

[0027] The standard deviation of the atomic ratio of nickel to iron reflects the uniformity of nickel and iron distribution. Theoretically, the smaller the standard deviation, the more uniform the distribution of nickel and iron, and the more consistent the oxide film structure. This is beneficial to reduce the formation of local high-activity sites and reduce moisture adsorption. However, an overly uniform oxide layer will slow down the acid leaching reaction rate during the acid leaching process. If the standard deviation of the atomic ratio of nickel to iron is greater than 0.05, nickel and iron are prone to uneven oxidation and are more likely to adsorb moisture from the air.

[0028] Nickel-iron powder meeting the above characteristics exhibits nickel and iron in oxidation states on its surface, with these oxidation states evenly distributed, indicating the presence of a uniform metal oxide layer on the surface. This uniform oxide layer reduces the differences in surface active sites, decreasing the nickel-iron powder's sensitivity to humidity changes. Furthermore, the passivation film formed by the uniform oxide layer possesses high density and chemical stability, effectively inhibiting contact between the metal substrate and moisture in the environment. Disordered or uneven oxide layers often contain defects (such as microcracks and pores), which can actually accelerate moisture absorption and corrosion. In addition, the uniform oxide layer acts as a physical barrier, reducing direct contact between airborne water molecules and the metal substrate, slowing the rate of water molecule diffusion into the interior.

[0029] In some alternative implementations, the sample standard deviation of the atomic ratio of nickel to iron in the XPS test can be 0.01 to 0.05, such as 0.01, 0.02, 0.03, 0.04 or 0.05, or other values ​​in the range of 0.01 to 0.05, for example, 0.031 to 0.042.

[0030] In some optional implementations, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in the XPS test can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.5%, or other values ​​not exceeding 10%, such as 0.23% to 9.57%. In some more typical implementations, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in the XPS test is 0.5% to 10%, for example, it can be 0.78% to 9.57%.

[0031] In some optional implementations, the sample standard deviation s² of the relative percentage content of +3 valent iron in the XPS test can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%, or other values ​​not exceeding 10%, such as 0.18% to 8.12%. In some optional implementations, the sample standard deviation s² of the relative percentage content of +3 valent iron in the XPS test is 0.5% to 8%, for example, it can be 0.75% to 6.63%.

[0032] In some optional embodiments, the nickel-iron powder further includes +2 valent iron. In XPS testing, the sample standard deviation s3 of the ratio of the relative percentage content of +3 valent iron to the relative percentage content of +2 valent iron in the iron element can be 0.013~0.2. In some more typical embodiments, s3 is 0.015~0.2, such as 0.015, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18 or 0.2, or other values ​​in the range of 0.015~0.2, for example, 0.019~0.16.

[0033] A uniform oxide layer acts as a physical barrier, reducing direct contact between airborne water molecules and the metal substrate, and slowing down the diffusion of water molecules inward. However, an excessively uniform oxide layer during acid leaching causes the reaction to proceed only from the outside in, lacking internal diffusion channels. This prolongs the acid leaching induction period and may actually decrease the overall reaction rate, requiring higher acid concentrations, higher temperatures, or longer times to achieve the same extraction rate, leading to increased energy and acid consumption. Therefore, to maintain a suitablely uniform oxide layer, this invention, by defining the aforementioned characteristics, can obtain a suitablely uniform oxide layer.

[0034] In some alternative implementations, the atomic ratio of nickel to iron in the XPS test can be 0.3 to 0.5, such as 0.3, 0.4, or 0.5, or other values ​​in the range of 0.3 to 0.5, such as 0.390 to 0.494.

[0035] In some alternative implementations, the relative percentage of +2 valent nickel in the nickel element in the XPS test can be 40% to 95%, such as 40%, 50%, 60%, 70%, 80%, 90% or 95%, or other values ​​in the range of 40% to 95%, such as 40.42% to 91.14%.

[0036] In some optional implementations, the relative percentage content of +3 valent iron in the XPS test can be 40% to 75%, such as 45%, 50%, 55%, 60%, 65%, 70%, or 75%, or other values ​​within the range of 45% to 75%. In some more typical implementations, the relative percentage content of +3 valent iron in the XPS test is 41.67% to 74.49%.

[0037] In some alternative implementations, the relative percentage of +2 valent iron in the XPS test can be 20% to 45%, such as 20%, 25%, 30%, 35%, 40%, or 45%, or other values ​​within the range of 20% to 45%.

[0038] In some optional implementations, during XPS testing, the ratio of the relative percentage of +3 ferric iron to the relative percentage of +2 ferric iron can be 1 to 2.8, such as 1, 1.5, 2, 2.5, or 2.8, or other values ​​within the range of 1 to 2.8. In some more typical implementations, during XPS testing, the ratio of the relative percentage of +3 ferric iron to the relative percentage of +2 ferric iron is 1.07 to 2.6.

[0039] Nickel-iron powder that meets the above requirements has a uniform distribution of nickel and iron on its surface, and the nickel and iron are uniformly oxidized, which can effectively inhibit the adsorption and penetration of moisture, while ensuring the acid leaching efficiency of the nickel-iron powder.

[0040] In some alternative embodiments, the tap density of the nickel-iron powder can be 3.3 g / cm³. 3 ~4.5g / cm 3 For example, 3.3g / cm 3 3.5g / cm 3 3.8g / cm 3 4g / cm 3 4.2g / cm 3 Or 4.5g / cm 3 etc., can also be 3.3 g / cm 3 ~4.5g / cm 3 Other values ​​within the range, for example, could be 3.35 g / cm³. 3 ~4.23g / cm 3 .

[0041] The aforementioned nickel-iron powder has a relatively high tap density, indicating that the porosity between the nickel-iron powder particles is small. This reduces capillary porosity between the powder particles, decreases capillary adsorption of moisture, and lowers the moisture absorption rate. However, the tap density should not be too high, as excessive density hinders sufficient and effective contact between the nickel-iron powder and the acid leaching solution, reducing the leaching effect.

[0042] In some optional embodiments, the particle size of the nickel-iron powder can be 70μm to 200μm, such as 70μm to 180μm, 75μm to 180μm, 75μm to 200μm, etc., or other values ​​within the range of 70μm to 200μm. The particle size of the nickel-iron powder can be obtained by testing with a sieve of a certain aperture. For example, 70μm to 200μm means that all nickel-iron powder can pass through a 200μm aperture sieve but cannot pass through a 70μm aperture sieve.

[0043] If the nickel-iron powder particles are too small, they may have a high specific surface area, making it easier for water molecules to diffuse between particles and on the surface; while if the nickel-iron powder particles are too large, the specific surface area will be too small, which is not conducive to the full and effective contact between the nickel-iron powder and the acid leaching solution, thus reducing the leaching effect.

[0044] In some alternative embodiments, the water absorption rate of the nickel-iron powder does not exceed 5.2%, for example, it can be 2.27% to 5.13%. In some more typical embodiments, the water absorption rate of the nickel-iron powder does not exceed 3.5%, such as it can be 2.27% to 3.38%.

[0045] In some optional embodiments, the acid leaching efficiency of the nickel-iron powder is not less than 80%, for example, it can be 80.33% to 86.13%.

[0046] As mentioned above, the nickel-iron powder provided by this invention is not prone to moisture absorption or clumping during storage, and can maintain its free-flowing characteristics even after long-term storage, making it easy to transport and unload, and also has good acid leaching efficiency.

[0047] Accordingly, the present invention provides a method for preparing nickel-iron powder as described in any of the foregoing embodiments, comprising the following steps: melting a nickel-iron alloy to obtain a nickel-iron liquid; atomizing the nickel-iron liquid to obtain a slurry; and drying and oxidizing the slurry.

[0048] In some alternative embodiments, the nickel-iron alloy raw material may, by way of example but not by way of limitation, be derived from the product of reduction smelting of laterite nickel ore.

[0049] In some alternative embodiments, the molten nickel-iron is mixed at 1650°C to 1750°C before atomization. The mixing temperature can be 1650°C, 1680°C, 1700°C, 1720°C, or 1750°C, or other values ​​within the range of 1650°C to 1750°C.

[0050] For example, nickel-iron alloy raw materials are added to a furnace to melt them into molten nickel-iron, which is then poured into a tundish. The temperature of the tundish is controlled at 1650℃~1750℃, and the molten nickel-iron is magnetically stirred to ensure uniform distribution. Subsequently, the molten nickel-iron is fed from the tundish into an atomization system (such as...). Figure 1 (As shown) to perform atomization.

[0051] In some alternative implementations, atomization employs a coaxial double-layer annular slit nozzle (e.g.) Figure 2 As shown in the figure, the outermost 3 annular slits are the high-pressure gas outlets, the middle 2 annular slits are the high-pressure water outlets, and the inner hole 1 is the melt outlet.

[0052] The outlet diameter of the melt flow can be 10mm~15mm, such as 10mm, 11mm, 12mm, 13mm, 14mm or 15mm, or other values ​​within the range of 10mm~15mm.

[0053] The slit at the outlet of the high-pressure water flow can be 0.5mm to 0.8mm, such as 0.5mm, 0.6mm, 0.7mm or 0.8mm, or other values ​​within the range of 0.5mm to 0.8mm.

[0054] The high-pressure gas outlet slit can be 1mm to 2mm, such as 1mm, 1.5mm or 2mm, or other values ​​within the range of 1mm to 2mm.

[0055] The air-water mixture and the melt form an impact angle of 15° to 30°, such as 15°, 18°, 20°, 25°, or 30°, or other values ​​within the range of 15° to 30°. The aforementioned impact angle refers to the angle between the air-water jet direction (slanted downward jetting of the melt) and the vertically downward direction (melt outflow direction). An impact angle within this range allows the high-pressure water and high-pressure gas to fully condense and break up the melt, producing nickel-iron powder with suitable particle size and morphology. If the impact angle between the air-water mixture and the melt is too small, it is not conducive to the impact and breaking up of the melt, easily leading to poor sphericity, large particle size, and narrow particle size distribution in the resulting nickel-iron powder. Conversely, if the impact angle is too large, it is also not conducive to the impact and breaking up of the melt, easily leading to small particle size, irregular powder shape, and low apparent density in the resulting nickel-iron powder.

[0056] In some optional embodiments, the gas is a mixture of an inert gas and hydrogen, with the inert gas comprising 96.5% to 98% by volume (e.g., 96.5%, 97%, 97.5%, or 98%), and the balance being hydrogen. The inert gas may be nitrogen and / or argon, etc.

[0057] In some alternative implementations, the melt flow rate can be 0.5 kg / s to 1.0 kg / s, such as 0.5 kg / s, 0.6 kg / s, 0.7 kg / s, 0.8 kg / s, 0.9 kg / s or 1 kg / s, or other values ​​within the range of 0.5 kg / s to 1.0 kg / s.

[0058] The water pressure can be between 8MPa and 15MPa, such as 8MPa, 10MPa, 12MPa, or 15MPa, or other values ​​within the range of 8MPa to 15MPa. If the water pressure is too low, it can easily lead to insufficient atomization, making it difficult for the molten metal droplets to solidify, resulting in larger powder particle size and poor sphericity; if the water pressure is too high, it can easily lead to excessive crushing, resulting in a large amount of fine powder, which affects the tapped density.

[0059] The water temperature can be between 70℃ and 85℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, or 85℃, or other values ​​within the range of 70℃ to 85℃. If the water temperature is too low, the molten metal droplets solidify quickly, increasing internal stress and making the powder prone to cracking and breakage, resulting in irregularly shaped powder. If the water temperature is too high, the molten metal droplets solidify too slowly, causing them to stick together and resulting in irregularly shaped powder, large particles, which is not conducive to improving the tap density and also increases production costs.

[0060] The water flow rate can be 140m³ 3 / h~160m 3 / h, such as 140m 3 / h, 145m 3 / h, 150m 3 / h, 155m 3 / h or 160m 3 / h, etc., can also be 140m 3 / h~160m 3 Other values ​​within the / h range. If the water flow rate is too low, the cooling capacity is insufficient, and the molten metal droplets cannot be cooled and solidified sufficiently, which can easily lead to irregular powder shapes and poor sphericity; if the water flow rate is too high, the excessive impact force will cause the powder to be excessively broken and the particle size to be too small, affecting the tap density.

[0061] The gas pressure can be 1.0MPa to 2.5MPa, such as 1MPa, 1.5MPa, 2MPa or 2.5MPa, or other values ​​within the range of 1.0MPa to 2.5MPa.

[0062] The gas flow rate can be 100m / s to 150m / s, such as 100m / s, 120m / s or 150m / s, or other values ​​within the range of 100m / s to 150m / s.

[0063] Gas pressure and gas flow rate also affect the atomization effect. If the gas pressure is too low or the gas flow rate is too slow, the impact crushing effect will not be achieved. If the gas pressure is too high or the gas flow rate is too fast, it will easily lead to excessive impact crushing, which will increase the fine powder, adsorption agglomeration and adhesion, which is not conducive to the compaction density of the powder.

[0064] At the same time, the above air and water atomization process parameters are coordinated to ensure that nickel-iron powder with suitable morphology and particle size is obtained. Nickel-iron powder with suitable morphology and particle size is conducive to subsequent oxidation to obtain nickel-iron powder with a suitable and uniform oxide layer.

[0065] Continuing from the above, during atomization, a three-layer structure of "gas-encapsulated water-encapsulated metal" is adopted. The outermost layer 3, high-pressure gas, can protect and assist in crushing. The gas contains hydrogen, which can form a reducing gas curtain, isolate the air, prevent oxidation at high temperatures, and obtain a metal matrix with low oxygen content. The middle layer 2, high-pressure hot water, can reduce the cooling rate, promote spheroidization, and utilize the Leidenfrost effect to delay solidification and improve sphericity, thereby increasing the tap density of the product. The inner melt layer has a small aperture to ensure that the melt flow is slender and easy to crush. Through the dual crushing function of high-pressure water and high-pressure gas, powder with appropriate particle size distribution and sphericity is obtained, thereby improving the tap density.

[0066] In some alternative embodiments, drying includes: firstly, using a magnetic separator to perform preliminary separation of the powder slurry in an inert gas protected environment, and then using a filter press to dehydrate the wet nickel-iron powder obtained by magnetic separation.

[0067] In some alternative embodiments, oxidation includes: drying at 100°C to 120°C (e.g., 100°C, 110°C, or 120°C) for 25 min to 35 min (e.g., 25 min, 30 min, or 35 min) under a protective atmosphere, followed by introducing 0.5% to 1% (e.g., 0.5%, 0.8%, or 1%) of oxygen and treating at 150°C to 250°C (e.g., 150°C, 200°C, or 250°C) for 5 min to 15 min (e.g., 5 min, 10 min, or 15 min).

[0068] For example, the solid obtained from dehydration is transferred to a rotary kiln to be uniformly heated and oxidized. The loading amount is controlled to be 10% to 15% of the rotary kiln volume (e.g., 10%, 12%, or 15%), and the rotary kiln speed is controlled to be 2 to 6 rpm (e.g., 2 rpm, 4 rpm, or 6 rpm). Under a protective atmosphere, it is dried at 100°C to 120°C for 25 to 35 minutes. Then, oxygen accounting for 0.5% to 1% (volume percentage) of the protective atmosphere is introduced, and it is treated at 150°C to 250°C for 5 to 15 minutes. After treatment, the oxygen supply is cut off, and it is cooled to room temperature under a protective atmosphere to prevent the oxide film from cracking due to contact with air in a hot environment.

[0069] If the amount of oxygen introduced is too small, an effective oxide layer cannot be formed, which is not conducive to hindering the absorption of moisture in the air; if the amount of oxygen introduced is too large, the oxide layer is too thick, forming a physical barrier during acid leaching, resulting in high acid penetration resistance, reduced metal leaching rate, and poor acid leaching efficiency.

[0070] The above process, by introducing a trace amount of oxygen at an appropriate temperature, can generate a suitable oxide layer on the powder surface. By first generating a metal matrix with low oxygen content, it is beneficial to generate a suitable and uniform oxide layer on the subsequent surface. Since nickel-iron is easily oxidized in air, if the initial oxidation process is not controlled, the surface of the nickel-iron powder obtained by atomization will have an uneven oxide layer, and even if it is oxidized again later, a suitable and uniform oxide layer cannot be obtained.

[0071] Furthermore, the present invention provides an application of nickel-iron powder as described in any of the foregoing embodiments, wherein the nickel-iron powder is used to prepare battery cathode materials.

[0072] The features and performance of the present invention will be further described in detail below with reference to the embodiments. The nickel-iron alloy raw materials used in the following embodiments and comparative examples are all derived from the reduction smelting of laterite nickel ore.

[0073] Example 1 This embodiment provides a nickel-iron powder, the preparation method of which includes the following steps: S1: Smelting.

[0074] The nickel-iron alloy raw material is added to the furnace and melted into nickel-iron liquid.

[0075] S2: Mix well.

[0076] The molten nickel-iron is poured into the tundish, and the temperature of the tundish is controlled at 1650℃. The tundish is then magnetically stirred to ensure that the molten nickel-iron is evenly distributed.

[0077] S3: Atomization.

[0078] The molten nickel-iron enters the atomization system from the tundish. The atomization system employs a coaxial double-layer annular slit nozzle. The outermost layer (3 annular slits) is the high-pressure gas outlet, the middle layer (2 annular slits) is the high-pressure water outlet, and the inner hole (1) is the melt outlet. The melt outlet has a diameter of 10 mm, the high-pressure water outlet has a slit diameter of 0.6 mm, and the high-pressure gas outlet has a slit diameter of 1 mm. The gas, water, and melt all form a 15° impact angle. The gas is a mixture of 98% (volume percentage) nitrogen and 2% (volume percentage) hydrogen.

[0079] Start atomization, and control the melt flow rate of the atomization system at 0.8 kg / s, water pressure at 10 MPa, water temperature at 70℃, and water flow rate at 140 m³ / s. 3 / h; gas pressure is 1.0MPa, gas flow rate is 100m / s, and slurry is obtained.

[0080] S4: Drying.

[0081] Under nitrogen protection, a magnetic separator is first used to perform preliminary separation of the powder slurry, and then a filter press is used to dehydrate the wet nickel-iron powder obtained by magnetic separation.

[0082] S5: Oxidation.

[0083] The solid obtained from dehydration is transferred to a rotary kiln, with the loading amount controlled at 12% of the rotary kiln volume and the rotary kiln speed controlled at 3 rpm. It is dried at 100°C for 30 min in a nitrogen atmosphere, and then oxygen at 0.5% (volume percentage) of nitrogen is introduced and treated at 150°C for 15 min. After treatment, the oxygen supply is cut off, and the powder is cooled to room temperature in a nitrogen atmosphere to obtain the nickel-iron powder.

[0084] Example 2 This embodiment provides a nickel-iron powder, the preparation method of which includes the following steps: S1: Smelting.

[0085] The nickel-iron alloy raw material is added to the furnace and melted into nickel-iron liquid.

[0086] S2: Mix well.

[0087] The molten nickel-iron is poured into the tundish, and the temperature of the tundish is controlled at 1700℃. The tundish is then magnetically stirred to ensure that the molten nickel-iron is evenly distributed.

[0088] S3: Atomization.

[0089] The molten nickel-iron enters the atomization system from the tundish. The atomization system employs a coaxial double-layer annular slit nozzle. The outermost layer (3 annular slits) is the high-pressure gas outlet, the middle layer (2 annular slits) is the high-pressure water outlet, and the inner hole (1) is the melt outlet. The melt outlet has a diameter of 15 mm, the high-pressure water outlet has a slit diameter of 0.8 mm, and the high-pressure gas outlet has a slit diameter of 1.5 mm. The gas, water, and melt all form a 25° impact angle. The gas is a mixture of 96.5% (volume percentage) nitrogen and 3.5% (volume percentage) hydrogen.

[0090] Start atomization, and control the melt flow rate of the atomization system at 1.0 kg / s, water pressure at 15 MPa, water temperature at 85℃, and water flow rate at 150 m³ / s. 3 / h; gas pressure is 2.5MPa, gas flow rate is 150m / s, and slurry is obtained.

[0091] S4: Drying.

[0092] Under nitrogen protection, a magnetic separator is first used to perform preliminary separation of the powder slurry, and then a filter press is used to dehydrate the wet nickel-iron powder obtained by magnetic separation.

[0093] S5: Oxidation.

[0094] The solid obtained from dehydration is transferred to a rotary kiln, and the loading amount is controlled to be 10% of the volume of the rotary kiln. The rotation speed of the rotary kiln is controlled to be 5 rpm. The solid is dried at 120°C for 25 min in a nitrogen atmosphere. Then, oxygen accounting for 1% (volume percentage) of the nitrogen atmosphere is introduced and the solid is treated at 250°C for 5 min. After the treatment, the oxygen supply is cut off and the solid is cooled to room temperature in a nitrogen atmosphere to obtain the nickel-iron powder.

[0095] Example 3 This embodiment provides a nickel-iron powder, the preparation method of which includes the following steps: S1: Smelting.

[0096] The nickel-iron alloy raw material is added to the furnace and melted into nickel-iron liquid.

[0097] S2: Mix well.

[0098] The molten nickel-iron is poured into the tundish, and the temperature of the tundish is controlled at 1750℃. The tundish is then magnetically stirred to ensure that the molten nickel-iron is evenly distributed.

[0099] S3: Atomization.

[0100] The molten nickel-iron enters the atomization system from the tundish. The atomization system employs a coaxial double-layer annular slit nozzle. The outermost layer (3 annular slits) is the high-pressure gas outlet, the middle layer (2 annular slits) is the high-pressure water outlet, and the inner hole (1) is the melt outlet. The melt outlet has a diameter of 12mm, the high-pressure water outlet has a slit diameter of 0.5mm, and the high-pressure gas outlet has a slit diameter of 2mm. The gas, water, and melt all form a 30° impact angle. The gas is a mixture of 97.5% (volume percentage) nitrogen and 2.5% (volume percentage) hydrogen.

[0101] Start atomization, controlling the melt flow rate of the atomization system to 0.5 kg / s, water pressure to 8 MPa, water temperature to 75℃, and water flow rate to 160 m³ / s. 3 / h; gas pressure is 1.5MPa, gas flow rate is 120m / s, and slurry is obtained.

[0102] S4: Drying.

[0103] Under nitrogen protection, a magnetic separator is first used to perform preliminary separation of the powder slurry, and then a filter press is used to dehydrate the wet nickel-iron powder obtained by magnetic separation.

[0104] S5: Oxidation.

[0105] The solid obtained from dehydration is transferred to a rotary kiln, with the loading amount controlled at 15% of the rotary kiln volume and the rotary kiln speed controlled at 2 rpm. It is dried at 120°C for 35 min under nitrogen atmosphere, and then oxygen accounting for 0.7% (volume percentage) of nitrogen is introduced and treated at 200°C for 10 min. After treatment, the oxygen supply is cut off, and it is cooled to room temperature under nitrogen atmosphere to obtain the nickel-iron powder.

[0106] Example 4 This embodiment provides a nickel-iron powder, the preparation method of which includes the following steps: S1: Smelting.

[0107] The nickel-iron alloy raw material is added to the furnace and melted into nickel-iron liquid.

[0108] S2: Mix well.

[0109] The molten nickel-iron is poured into the tundish, and the temperature of the tundish is controlled at 1700℃. The tundish is then magnetically stirred to ensure that the molten nickel-iron is evenly distributed.

[0110] S3: Atomization.

[0111] The molten nickel-iron enters the atomization system from the tundish. The atomization system employs a coaxial double-layer annular slit nozzle. The outermost layer (3 annular slits) is the high-pressure gas outlet, the middle layer (2 annular slits) is the high-pressure water outlet, and the inner hole (1) is the melt outlet. The melt outlet has a diameter of 12mm, the high-pressure water outlet has a slit diameter of 0.7mm, and the high-pressure gas outlet has a slit diameter of 1.5mm. The gas, water, and melt all form a 20° impact angle. The gas is a mixture of 97% (volume percentage) nitrogen and 3% (volume percentage) hydrogen.

[0112] Start atomization, controlling the melt flow rate of the atomization system to 0.5 kg / s, water pressure to 12 MPa, water temperature to 80℃, and water flow rate to 160 m³ / s. 3 / h; gas pressure is 2MPa, gas flow rate is 135m / s, and slurry is obtained.

[0113] S4: Drying.

[0114] Under nitrogen protection, a magnetic separator is first used to perform preliminary separation of the powder slurry, and then a filter press is used to dehydrate the wet nickel-iron powder obtained by magnetic separation.

[0115] S5: Oxidation.

[0116] The solid obtained from dehydration is transferred to a rotary kiln, with the loading amount controlled at 12% of the rotary kiln volume and the rotary kiln speed controlled at 6 rpm. It is dried at 120°C for 30 min in a nitrogen atmosphere, and then oxygen at 0.85% (volume percentage) of nitrogen is introduced and treated at 200°C for 8 min. After treatment, the oxygen supply is cut off, and it is cooled to room temperature in a nitrogen atmosphere to obtain the nickel-iron powder.

[0117] Example 5 The only difference between this embodiment and embodiment 1 is that in S3, the water temperature is 65°C.

[0118] Example 6 The only difference between this embodiment and Embodiment 1 is that in S3, the water temperature is 90℃.

[0119] Example 7 The only difference between this embodiment and embodiment 1 is that in S5, the rotary kiln speed is 1 rpm, and oxygen accounting for 0.4% (volume percentage) of nitrogen is introduced.

[0120] Example 8 The only difference between this embodiment and Embodiment 1 is that in S5, oxygen, which accounts for 1.2% (volume percentage) of nitrogen, is introduced.

[0121] Comparative Example 1 The only difference between this comparative example and Example 1 is that in S3, only high-pressure water atomization is used, and there is no high-pressure gas; and step S5 is omitted.

[0122] Comparative Example 2 The only difference between this comparative example and Example 1 is that in S3, only high-pressure 100% nitrogen atomization is used, and high-pressure water is not used; step S5 is not used.

[0123] Comparative Example 3 The only difference between this comparative example and Example 1 is that in S3, the high-pressure gas is 100% nitrogen.

[0124] Comparative Example 4 The only difference between this comparative example and Example 1 is that in S3, the gas and the melt form a 90° impact angle.

[0125] test The nickel-iron powders provided in Examples 1-8 and Comparative Examples 1-4 were tested according to the following methods, and the results are shown in Tables 1 to 4.

[0126] (1) XPS (X-ray photoelectron spectroscopy) testing: Thermo SCIENTIFIC Nexsa instrument was used, and Thermo Avantage v 5,9921 software was employed. The excitation source was Al Kα rays (hv=1486.6eV). After the test, the software was used to perform peak fitting on the test data of nickel and iron elements to obtain the relative percentage content of each valence state in each element. At least 5 different regions were selected for testing in each group of samples. Finally, the sample standard deviation was calculated. In this test example, 5 different regions were tested in each group of samples. The sample standard deviation of the relative percentage content of the target valence state of the element in the sample = , n =5, x i For the measured sample i The relative percentage of the target valence state of elements in each region. The average value of the relative percentage content of the target valence state of the elements in the 5 regions measured is shown in Tables 1 and 2 below; the sample standard deviation of the nickel and iron atomic ratios is calculated directly from the Peak Table data in the test results, and the calculation method is the same as above.

[0127] Taking the nickel-iron powder obtained in Example 1 as an example, its XPS graph is as follows: Figure 3 As shown in the figure, the surface of the nickel-iron powder has nickel and iron in an oxidized state.

[0128] (2) Tap density test: The tap density test was conducted using a BT-302 tap density meter in accordance with GB / T 5162-2006.

[0129] (3) Particle size test: Referring to GB / T1480-2025, the powders obtained from each example and comparative example were subjected to particle size sieving test.

[0130] (4) Water absorption test: Dry the nickel-iron powder sample at 105℃ to constant weight, record it as m0, the unit is g, and then store it at 25℃ and 70% relative humidity for 24h and weigh it, record it as m1, the unit is g; calculate the water absorption rate of the nickel-iron powder sample, water absorption rate = [(m1-m0) / m0]×100%.

[0131] (5) Acid leaching efficiency test: The nickel-iron powder sample after the water absorption test was mixed with sulfuric acid solution at a solid-liquid ratio of 1g:10mL. After reacting for 120min at 50℃ and pH 1.5, the acid leaching efficiency of the nickel-iron powder sample was calculated. Acid leaching efficiency = [(mass of nickel-iron powder before reaction m0g - mass of nickel-iron powder after reaction m2g) / mass of nickel-iron powder before reaction m0g] × 100%. The mass of nickel-iron powder after reaction is the mass of the nickel-iron powder after acid dissolution, after filtration, washing with deionized water and drying to constant weight, and is recorded as m2g.

[0132] Table 1 Test Results

[0133] Table 2 Test Results (Continued)

[0134] Table 3 Test Results (Continued)

[0135] Table 4 Test Results (Continued)

[0136] Based on the results in Tables 1 to 4, it can be seen that the nickel and iron on the surface of nickel-iron powder have oxidation states. The uniformity of the distribution of nickel and iron, and the dispersion of the relative percentage distribution of nickel and iron in oxidation states, affect the water absorption rate and acid leaching efficiency of the nickel-iron powder. The smaller the sample standard deviation, the more uniform the distribution of the relative percentage distribution of nickel and iron in oxidation states, and the lower the water absorption rate. However, if the sample standard deviation is too small, it will affect the acid leaching efficiency of the nickel-iron powder. After absorbing water, the nickel-iron powder will clump together, which will affect the contact between the nickel-iron powder and the acid solution during acid leaching, thus hindering the acid leaching efficiency.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nickel-iron powder, characterized in that, The nickel-iron powder includes +2 valent nickel and +3 valent iron. In XPS testing, the sample standard deviation of the atomic ratio of nickel to iron is 0.01~0.05, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in nickel element does not exceed 10%, and the sample standard deviation s2 of the relative percentage content of +3 valent iron in iron element does not exceed 10%.

2. The nickel-iron powder according to claim 1, characterized in that, In XPS testing, the sample standard deviation s1 of the relative percentage content of +2 valent nickel in nickel element is 0.5%~10%; And / or, the sample standard deviation (s²) of the relative percentage of +3 valent iron in iron is 0.5% to 8%; And / or, the sample standard deviation s3 of the ratio of the relative percentage of +3 valent iron to the relative percentage of +2 valent iron in iron is 0.015 to 0.

2.

3. The nickel-iron powder according to claim 1 or 2, characterized in that, The nickel-iron powder also has at least one of the following characteristics: Feature 1: In XPS testing, the atomic ratio of nickel to iron is 0.3~0.5; Feature 2: In XPS testing, the relative percentage of +2 valent nickel in the nickel element is 40%~95%; Feature 3: In XPS testing, the relative percentage of +3 valent iron in the iron element is 40%~75%; Feature 4: In XPS testing, the relative percentage of +2 valent iron in the iron element is 20%~45%; Feature 5: In XPS testing, the ratio of the relative percentage of +3 valent iron to the relative percentage of +2 valent iron in iron is 1~2.8; Feature 6: The tap density of the nickel-iron powder is 3.3 g / cm³. 3 ~4.5g / cm 3 ; Feature 7: The particle size of the nickel-iron powder is 70μm~200μm; Feature 8: The water absorption rate of nickel-iron powder does not exceed 5.2%; Feature 9: The acid leaching efficiency of nickel-iron powder is not less than 80%.

4. A method for preparing nickel-iron powder as described in any one of claims 1 to 3, characterized in that, Includes the following steps: The nickel-iron alloy is melted to obtain molten nickel-iron; The molten nickel-iron is atomized to obtain a slurry; The slurry is dried and oxidized.

5. The preparation method according to claim 4, characterized in that, Before atomization, the nickel-iron liquid is mixed at 1650℃~1750℃.

6. The preparation method according to claim 4, characterized in that, The atomization uses a coaxial double-layer annular slit nozzle. The outermost annular slit is the high-pressure gas outlet, the middle annular slit is the high-pressure water outlet, and the inner hole is the melt outlet.

7. The preparation method according to claim 6, characterized in that, The coaxial double-layer annular slit nozzle has at least one of the following characteristics: Feature 10: The melt flow outlet diameter is 10mm~15mm; Feature 11: The high-pressure water flow outlet slit is 0.5mm~0.8mm; Feature 12: The high-pressure gas outlet slit is 1mm~2mm; Feature 13: The gas, water, and melt all form an impact angle of 15°~30°; Preferably, the gas is a mixture of inert gas and hydrogen, wherein the inert gas accounts for 96.5% to 98% by volume, and the remainder is hydrogen.

8. The preparation method according to claim 6 or 7, characterized in that, Atomization conditions include at least one of the following characteristics: Feature 14: Melt flow rate is 0.5 kg / s to 1.0 kg / s; feature 15: Water pressure is 8MPa~15MPa; Feature 16: Water temperature is 70℃~85℃; Feature 17: Water flow rate is 140m³ 3 / h~160m 3 / h; Feature 18: Gas pressure is 1.0 MPa to 2.5 MPa; Feature 19: Gas flow rate is 100m / s~150m / s.

9. The preparation method according to claim 4, characterized in that, Oxidation includes: Under a protective atmosphere, first dry at 100℃~120℃ for 25min~35min, then introduce oxygen accounting for 0.5%~1% of the protective gas, and treat at 150℃~250℃ for 5min~15min.

10. An application of the nickel-iron powder as described in any one of claims 1 to 3, characterized in that, The nickel-iron powder is used to prepare the positive electrode material for batteries.

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