Lithium-rich lithium ferrite lithium supplement agent, preparation method thereof, battery and power utilization device

Abstract

The invention relates to the technical field of batteries, in particular to a lithium-rich lithium ferrite lithium supplement agent, a preparation method thereof, a battery and an electric device. The lithium supplement agent disclosed by the invention is prepared by the following steps: mixing and grinding an iron source and a lithium source, carrying out first drying to obtain a precursor, and activating the precursor to form Li5FeO4; li5FeO4 is divided into first particles and second particles, Dv50 of the first particles is x, Dv50 of the second particles is y, and x is larger than y; mixing the first particles, a first carbon source, first carbon nanotubes, a first dispersing agent and a first solvent to form first slurry, and performing second drying and first sintering on the first slurry to obtain large particles; mixing the second particles, a second carbon source, a second carbon nanotube, a second dispersant and a second solvent to form second slurry, and performing third drying and second sintering on the second slurry to obtain small particles; and mixing the large particles and the small particles to obtain the lithium-rich lithium ferrite lithium supplement agent. The lithium supplementing agent has relatively high tap density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and more particularly to a lithium-rich lithium iron phosphate lithium supplement, a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] Lithium iron phosphate battery (LFP) has become one of the mainstream choices of long-life batteries due to its high safety and low cost. Improving the cycle life by supplementing lithium at the positive electrode is an effective means at present. Lithium-rich lithium iron phosphate (Li5FeO4) is widely used due to its high capacity. The disadvantage of Li5FeO4 is that the material without coating treatment has poor stability in air environment and poor intrinsic conductivity, only 10 -8 S / cm, and the tap density of Li5FeO4 (hereinafter referred to as LFC) is low, which is not conducive to the improvement of the energy density of the battery.

[0003] At present, it is of great significance to obtain high-performance modified Li5FeO4 and further improve the energy density of the battery. SUMMARY

[0004] Therefore, the present application provides a lithium-rich lithium iron phosphate lithium supplement, a preparation method thereof, a battery and an electric device. By performing graded carbon coating on Li5FeO4 with different particle sizes and containing carbon nanotubes in the carbon coating layer, the obtained lithium-rich lithium iron phosphate lithium supplement has high tap density, thereby effectively improving the energy density of the battery.

[0005] To solve the above technical problems, the present application is implemented as follows: According to one aspect of the present application, the present application provides a preparation method of a lithium-rich lithium iron phosphate lithium supplement, comprising the following steps: mixing and grinding an iron source and a lithium source, obtaining a precursor after first drying, and forming Li5FeO4 by activating the precursor; dividing the Li5FeO4 into first particles and second particles, wherein the median particle size D v50 is x, the median particle size D v50 of the second particles is y, and x>y; mixing the first particles, a first carbon source, a first carbon nanotube, a first dispersant and a first solvent to form a first slurry, performing second drying on the first slurry, and obtaining large particles after first sintering; mixing the second particles, a second carbon source, a second carbon nanotube, a second dispersant and a second solvent to form a second slurry, performing third drying on the second slurry, and obtaining small particles after second sintering; The large particles and the small particles are mixed to obtain a lithium-rich lithium ferrite supplement.

[0006] In some of these implementations, x satisfies: 20μm≤x≤30μm.

[0007] In some of these implementations, y satisfies: 3μm≤y≤10μm.

[0008] In some embodiments, the first carbon nanotube comprises: an aspect ratio of 10 3 ~10 4 Multi-walled carbon nanotubes with an aspect ratio greater than 10 4 At least one of the single-walled carbon nanotubes, preferably, the first carbon nanotube comprises an aspect ratio greater than 10. 4 Single-walled carbon nanotubes.

[0009] In some embodiments, the second carbon nanotube comprises: an aspect ratio of 10 3 ~10 4 Multi-walled carbon nanotubes.

[0010] In some of these embodiments, the mass ratio of the large particles to the small particles is 1:(1~2).

[0011] In some embodiments, the molar ratio of the first particle, the first carbon source, the first carbon nanotube, and the first dispersant is 100:(0.5~1.5):(0.5~2):0.8.

[0012] In some embodiments, the molar ratio of the second particle, the second carbon source, the second carbon nanotube, and the second dispersant is 100:(2~5):(0.5~2):0.8.

[0013] In some embodiments, the iron source includes at least one of ferric nitrate and ferric oxide.

[0014] In some embodiments, the lithium source includes at least one of lithium hydroxide and lithium carbonate.

[0015] In some of these embodiments, the first carbon source includes at least one of sucrose, glucose, and starch.

[0016] In some embodiments, the first dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol.

[0017] In some of these embodiments, the first solvent includes at least one of anhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

[0018] In some of these embodiments, the second carbon source includes at least one of sucrose, glucose, and starch.

[0019] In some embodiments, the second dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol.

[0020] In some of these embodiments, the second solvent includes at least one of polyanhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

[0021] In some of these embodiments, the activation process includes: The precursor was added to the radio frequency plasma reactor for activation; The radio frequency plasma reactor has a frequency of 13MHz~16MHz, a power of 300W~500W, a pressure of 40Pa~90Pa, and is in an inert gas atmosphere. The activation temperature is 200℃~300℃, and the activation time is 10min~15min.

[0022] In some embodiments, the solid content of the first slurry is 20% to 30%, preferably 25%.

[0023] In some embodiments, the solid content of the second slurry is 20% to 30%, preferably 25%.

[0024] In some embodiments, the first drying is carried out by spray drying, wherein the inlet temperature is 160°C to 165°C and the outlet temperature is 90°C to 95°C.

[0025] In some embodiments, the second drying is carried out by spray drying, wherein the inlet temperature is 170°C to 180°C and the outlet temperature is 80°C to 85°C.

[0026] In some embodiments, the third drying is performed by spray drying, wherein the inlet temperature is 170°C to 180°C and the outlet temperature is 80°C to 85°C.

[0027] In some of these embodiments, the temperature of the first sintering is 700°C to 900°C.

[0028] In some of these embodiments, the second sintering temperature is 950°C to 1100°C.

[0029] In some embodiments, the Li5FeO4 is divided into first particles and second particles, and the first particles and second particles are separated by a high-speed centrifuge; preferably, the centrifugal force of the high-speed centrifuge is 8000g~10000g.

[0030] In some embodiments, the mixing of the large and small particles is carried out using a fixed-bed apparatus, wherein the mixing is conducted in an inert gas atmosphere at a flow rate of 60 m / s. 3 / h~90m 3 / h, the mixing time is 1h~2h.

[0031] According to another aspect of the present invention, the present invention provides a lithium-rich lithium ferrite supplement agent, comprising: a lithium-rich lithium ferrite supplement agent prepared by the preparation method described in any of the above-described embodiments; The lithium-rich lithium iron phosphate supplement comprises Li5FeO4, which includes first particles and second particles, wherein the median particle size D of the first particles is... v50 Let x be the median particle size D of the second particle. v50 Let y be a given value, and x > y; The first particle has at least a portion of its surface coated with a first carbon coating layer, the first carbon coating layer including a first carbon nanotube; the second particle has at least a portion of its surface coated with a second carbon coating layer, the second carbon coating layer including a second carbon nanotube.

[0032] In some of these embodiments, the thickness of the first carbon coating layer is 5 nm to 10 nm.

[0033] In some of these embodiments, the thickness of the second carbon coating layer is 20 nm to 30 nm.

[0034] In some of these embodiments, the mass percentage of the first carbon nanotube is 0.4 wt% to 2 wt% based on the mass of the large particles.

[0035] In some of these embodiments, the mass percentage of the second carbon nanotube is 0.4 wt% to 2 wt% based on the mass of the small particles.

[0036] According to another aspect of the present invention, the present invention provides a battery comprising: a lithium-rich lithium iron phosphate supplement prepared by the preparation method described in any of the above-described embodiments.

[0037] The lithium-rich lithium iron ferrite supplement agent described in any of the above technical solutions.

[0038] According to another aspect of the present invention, an electrical device is provided, comprising: a battery as described in any of the above-described embodiments.

[0039] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. In this invention, the prepared Li5FeO4 is divided into first particles and second particles with different particle sizes. Then, the first and second particles are subjected to hierarchical carbon coating, causing the first particles to form large particles and the second particles to form small particles. Since the large particles have poor kinetic properties, the hierarchical coating method reduces the carbon layer content and increases the carbon nanotube content, thereby maximizing the improvement of the kinetic properties of the large particles. The small particles are coated with carbon nanotubes to form a spherical shape, which increases the tap density of the material and thus improves the energy density of the battery.

[0040] 2. In a preferred embodiment of the present invention, adding carbon nanotubes with a certain aspect ratio to the carbon coating layer of particles of different sizes can form a highly conductive network on the surface of the particles, thereby improving the release efficiency of lithium-rich lithium iron ferrite supplement and achieving efficient utilization of the supplement.

[0041] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0043] Figure 1 This is a SEM image of the lithium-rich lithium iron ferrite supplement provided in Example 6 of the present invention.

[0044] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0045] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0046] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0047] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0048] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] Currently, lithium iron phosphate (LFP) batteries have become one of the mainstream choices for long-life batteries due to their advantages such as high safety and low cost. Further improving the cycle life of LFP batteries has become a key research focus. One approach is to improve cycle life by adding lithium to the cathode, and lithium-rich lithium iron phosphate (Li5FeO4) is widely used due to its high specific capacity. However, Li5FeO4 has drawbacks, including poor stability in air and poor intrinsic conductivity (only 10⁻⁻¹). 8 S / cm; and the tap density of Li5FeO4 (abbreviated as LFC, LFC in the following text refers to this substance) is low, which is not conducive to improving the energy density of the battery.

[0054] In view of the technical problems existing in the prior art, the present invention provides a lithium-rich lithium iron ferrite supplement agent, its preparation method, battery and power device. By performing graded carbon coating on Li5FeO4 with different particle sizes and containing carbon nanotubes in the carbon coating layer, the resulting lithium-rich lithium iron ferrite supplement agent has a high tap density, which can effectively improve the energy density of the battery.

[0055] According to one aspect of the present invention, a method for preparing a lithium-rich lithium iron phosphate supplement includes the following steps: S1. Iron source and lithium source are mixed and ground, and after the first drying, a precursor is obtained. The precursor is then activated to form Li5FeO4.

[0056] As an example, the iron source includes, but is not limited to, one or more of ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), ferric nitrate (Fe(NO3)3·9H2O), and ferric acetate (Fe(CH3COO)3·H2O). The lithium source includes, but is not limited to, one or more of lithium hydroxide (LiOH·H2O), lithium carbonate (Li2CO3), and lithium acetate (CH3COOLi). After the iron and lithium sources are mixed evenly, they are ground. The grinding method can be mortar and pestle grinding or ball mill grinding. The first drying method can be freeze drying or oven drying. The specific methods of grinding and the first drying are not specifically limited in this embodiment. The activation treatment of the precursor can be carried out using a radio frequency plasma reactor or other activation methods commonly used in the art.

[0057] S2. Divide Li5FeO4 into first particles and second particles, wherein the median particle size D of the first particles is... v50 Let x be the median particle size D of the second particle. v50 Let y be the integer part of the integer part, and x > y.

[0058] The Li5FeO4 obtained in step S1 is separated into first particles and second particles based on particle size. This separation can be achieved using a centrifuge. For example, Li5FeO4 can be added to a high-speed centrifuge, and an appropriate centrifugal force can be selected to separate the Li5FeO4 into first and second particles of different sizes. It is understood that the median particle size of the separated first particles is larger than that of the second particles.

[0059] S3. Mix the first particle, the first carbon source, the first carbon nanotube, the first dispersant and the first solvent to form a first slurry, perform a second drying on the first slurry, and obtain large particles after a first sintering; mix the second particle, the second carbon source, the second carbon nanotube, the second dispersant and the second solvent to form a second slurry, perform a third drying on the second slurry, and obtain small particles after a second sintering.

[0060] The first carbon source includes, but is not limited to, glucose, sucrose, starch, maltose, cellulose, etc.; the second carbon source includes, but is not limited to, glucose, sucrose, starch, maltose, cellulose, etc. It is understood that the first carbon source can be the same as or different from the second carbon source. The first dispersant includes, but is not limited to, polyethylene glycol, sodium carboxymethyl cellulose, Tween-type dispersants, etc.; the second dispersant includes, but is not limited to, polyethylene glycol, sodium carboxymethyl cellulose, Tween-type dispersants, etc.; of course, the first dispersant can be the same as or different from the second dispersant. The first solvent includes, but is not limited to, anhydrous ethanol, anhydrous methanol, N-methylpyrrolidone, ethyl acetate, etc.; the second solvent includes, but is not limited to, anhydrous ethanol, anhydrous methanol, N-methylpyrrolidone, ethyl acetate, etc. Similarly, the first solvent can be the same as or different from the second solvent. The first and second carbon nanotubes can be carbon nanotubes (CNTs) with the same or different aspect ratios, or carbon nanotubes with different diameter ratios.

[0061] The first slurry is then subjected to a second drying process, which can be freeze-drying or spray drying. After the first sintering, large particles are obtained. The second slurry is then subjected to a third drying process, which can be oven drying, spray drying, or freeze drying. The second and third drying processes can be the same or different. The first and second sintering processes can use the same or different sintering methods, such as the sintering atmosphere and sintering temperature.

[0062] S4. After mixing large and small particles, lithium-rich lithium ferrite supplement is obtained.

[0063] The large and small particles obtained in step S3 can be mixed in any mass ratio as needed. The mixing method can be a fixed bed device, in which the large and small particles are loaded into the fixed bed pipeline according to the ratio. In order to prevent side reactions from occurring during the mixing process of large and small particles and affecting their overall performance, inert gases such as nitrogen or helium can also be introduced to mix the large and small particles evenly and obtain lithium-rich lithium iron ferrite supplement.

[0064] In this invention, Li5FeO4 is differentiated according to particle size and then subjected to graded carbon coating, with the carbon coating layer including carbon nanotubes. This graded coating, using different particle sizes, is primarily because larger particles have slightly worse kinetics than smaller particles. A single coating method would not be conducive to improving the kinetics of larger particles. Therefore, a near-original morphology coating method is used for larger particles, reducing the carbon coating content and increasing the carbon nanotube content, which maximizes their kinetic performance. Simultaneously, smaller particles inherently have superior kinetic performance, and a thicker carbon coating layer will not significantly degrade kinetic performance. Therefore, a thicker carbon coating layer on the surface of smaller particles increases the material's tap density, thereby improving the battery's energy density. High-performance carbon nanotubes can effectively form a highly conductive network, significantly improving the lithium replenishment release efficiency compared to ordinary carbon coating, achieving efficient utilization of the lithium replenishment agent.

[0065] In a specific embodiment of the present invention, x satisfies: 20μm≤x≤30μm.

[0066] As an example, the median particle size D of the first particle v50 That is, x can be any one of 20μm, 20.5μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, or 30μm, or any point value between any two. By limiting the median particle size of the first particle, its kinetic performance can be effectively controlled, so that the kinetic performance of the first particle is not too poor. Then, by coating it with a carbon coating layer containing carbon nanotubes, the kinetic performance of the first particle can be improved, thereby improving the energy density of the battery. If it exceeds the above range, the kinetic performance of the first particle may be too poor due to its large particle size, and its kinetic performance cannot be improved by carbon coating. At the same time, it may also affect the compaction density of the electrode, thus affecting the performance of the battery.

[0067] In a specific embodiment of the present invention, y satisfies: 3μm≤y≤10μm.

[0068] As an example, the median particle size D of the second particle v50That is, y can be any one of 3μm, 3.5μm, 4μm, 5μm, 6μm, 6.4μm, 7μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm or any point value between any two; similarly, by limiting the range of the median particle size of the second particle, small particles are obtained through carbon coating, which effectively improves the tap density of the material and enables the battery to have good energy density.

[0069] In a specific embodiment of the present invention, the first carbon nanotube comprises: an aspect ratio of 10. 3 ~10 4 Multi-walled carbon nanotubes with an aspect ratio greater than 10 4 At least one of the single-walled carbon nanotubes, preferably, the first carbon nanotube comprises an aspect ratio greater than 10. 4 Single-walled carbon nanotubes.

[0070] As an example, the first carbon nanotube includes, but is not limited to, having an aspect ratio of 10. 3 Multi-walled carbon nanotubes with an aspect ratio of 10 4 Multi-walled carbon nanotubes with an aspect ratio of 10 5 One or more of the single-walled carbon nanotubes; by limiting the type of the first carbon nanotube, it is possible to effectively enable large particles to form a highly conductive network and effectively improve the dynamic performance of large particles, thereby improving the energy density of the battery.

[0071] In a specific embodiment of the present invention, the second carbon nanotube comprises: an aspect ratio of 10. 3 ~10 4 Multi-walled carbon nanotubes.

[0072] As an example, the second carbon nanotube includes, but is not limited to, having an aspect ratio of 10. 3 Multi-walled carbon nanotubes with an aspect ratio of 10 4 One or more of the multi-walled carbon nanotubes.

[0073] In a specific embodiment of the present invention, the mass ratio of large particles to small particles is 1:(1~2).

[0074] As an example, the mass ratio of large particles to small particles can be any one of 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.5, 1:1.8, or 1:2, or any ratio between any two of them. By limiting the above range of the mass ratio of large particles to small particles, the compaction density of the electrode can be well controlled. For example, if there are too many small particles, the compaction density of the material may be reduced, which will affect the energy density of the battery.

[0075] In a specific embodiment of the present invention, the molar ratio of the first particle, the first carbon source, the first carbon nanotube and the first dispersant is 100:(0.5~1.5):(0.5~2):0.8.

[0076] As an example, the molar ratio of the first particle, the first carbon source, the first carbon nanotube, and the first dispersant can be any one of 100:0.5:0.5:0.8, 100:0.8:1:0.8, 100:1.2:1.5:0.8, or 100:1.5:2:0.8, or any ratio between any two of these. By limiting the range of the molar ratios of the above components, the thickness of the carbon coating layer on the surface of the large particles and the content of carbon nanotubes in the carbon coating layer can be effectively controlled. This can effectively control the kinetic performance of the large particles, thereby enabling the battery to have good energy density.

[0077] In a specific embodiment of the present invention, the molar ratio of the second particle, the second carbon source, the second carbon nanotube, and the second dispersant is 100:(2~5):(0.5~2):0.8.

[0078] As an example, the molar ratio of the second particle, the second carbon source, the second carbon nanotube, and the second dispersant can be any one of 100:2:0.5:0.8, 100:3:1:0.8, 100:4:1.5:0.8, or 100:5:2:0.8, or any ratio between any two of them. Similarly, by limiting the range of the molar ratio of the above components, the spherical carbon coating on the surface of the small particles can be effectively controlled, thereby improving the tap density of the material and enabling the battery to have good energy density.

[0079] In specific embodiments of the present invention, the iron source includes, but is not limited to, one or more of ferric nitrate and ferric oxide.

[0080] In a specific embodiment of the present invention, the lithium source includes at least one of lithium hydroxide and lithium carbonate. Exemplarily, the lithium source includes, but is not limited to, one or more of lithium hydroxide and lithium carbonate.

[0081] In a specific embodiment of the present invention, the first carbon source includes at least one of sucrose, glucose, and starch. Exemplarily, the first carbon source includes, but is not limited to, one or more of sucrose, glucose, starch, and cellulose.

[0082] In a specific embodiment of the present invention, the first dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol. Exemplarily, the first dispersant includes, but is not limited to, one or more of polyvinylpyrrolidone and polyethylene glycol.

[0083] In a specific embodiment of the present invention, the first solvent includes at least one of anhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate. Exemplarily, the first solvent includes, but is not limited to, one or more of anhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

[0084] In a specific embodiment of the present invention, the second carbon source includes at least one of sucrose, glucose, and starch. Exemplarily, the second carbon source includes, but is not limited to, one or more of sucrose, glucose, starch, and cellulose.

[0085] In a specific embodiment of the present invention, the second dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol. Exemplarily, the second dispersant includes, but is not limited to, one or more of polyvinylpyrrolidone and polyethylene glycol.

[0086] In a specific embodiment of the present invention, the second solvent includes at least one of polyanhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

[0087] For example, the second solvent includes, but is not limited to, one or more of anhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

[0088] In a specific embodiment of the present invention, the activation process includes: adding the precursor into a radio frequency plasma reactor for activation. The radio frequency plasma reactor has a frequency of 13MHz to 16MHz, a power of 300W to 500W, a pressure of 40Pa to 90Pa, is in an inert gas atmosphere, an activation temperature of 200℃ to 300℃, and an activation time of 10min to 15min.

[0089] As an example, when using a radio frequency plasma reactor to activate precursors, the frequency of the radio frequency plasma reactor can be any one of 13MHz, 14MHz, 15MHz, or 16MHz; the power can be any one of 300W, 400W, or 500W; the pressure can be any one of 40Pa, 50Pa, 60Pa, 80Pa, or 90Pa; the inert gas can be nitrogen, helium, or argon, etc.; the activation temperature can be 200℃, 220℃, 250℃, or 300℃; and the activation time can be 10min, 12min, or 15min.

[0090] In a specific embodiment of the present invention, the solid content of the first slurry is 20% to 30%, preferably 25%. Exemplarily, the solid content of the first slurry can be any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or any ratio between any two of them.

[0091] In a specific embodiment of the present invention, the solid content of the second slurry is 20% to 30%, preferably 25%. Exemplarily, the solid content of the second slurry can be any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or any ratio between any two of these values. By limiting the solid content of the first slurry and the second slurry respectively, the thickness of the carbon coating layer on the surface of large and small particles, as well as the content of carbon nanotubes in the carbon coating layer, can be well controlled, so that the large particles have good kinetic properties, thereby giving the electrode formed by the large and small particles excellent compaction density.

[0092] In a specific embodiment of the present invention, the first drying method employs spray drying, wherein the inlet temperature is 160℃~165℃ and the outlet temperature is 90℃~95℃. Exemplarily, the first drying method employs spray drying, and the inlet temperature of the spray drying can be any one of 160℃, 162℃, 164℃, or 165℃, or any ratio between any two; the outlet temperature can be any one of 90℃, 92℃, 93℃, or 95℃, or any ratio between any two. The first drying method can effectively form a precursor, giving the precursor good dispersibility, and thus allowing for effective separation into first particles and second particles of different particle sizes in subsequent processes.

[0093] In a specific embodiment of the present invention, the second drying method employs spray drying, wherein the inlet temperature is 170℃~180℃ and the outlet temperature is 80℃~85℃. Exemplarily, the second drying method employs spray drying, and the inlet temperature of the spray drying can be any one of 170℃, 172℃, 175℃, or 180℃, or any ratio between any two; the outlet temperature can be any one of 80℃, 82℃, 83℃, or 85℃, or any ratio between any two. The second drying process dries the first slurry to form first particles with good dispersibility.

[0094] In a specific embodiment of the present invention, the third drying method employs spray drying, wherein the inlet temperature is 170°C to 180°C and the outlet temperature is 80°C to 85°C. Exemplarily, the third drying method employs spray drying, where the inlet temperature can be any one of 170°C, 172°C, 175°C, or 180°C, or any ratio between any two; the outlet temperature can be any one of 80°C, 82°C, 83°C, or 85°C, or any ratio between any two; the third drying method dries the second slurry to form well-dispersed second particles.

[0095] In a specific embodiment of the present invention, the temperature of the first sintering is 700°C to 900°C. Exemplarily, the temperature of the first sintering can be any one of 700°C, 750°C, 800°C, 850°C, or 900°C, or any ratio between any two of them; the first sintering will cause the first particles to form Li5FeO4 with at least a partial surface coating of carbon containing CNTs.

[0096] In a specific embodiment of the present invention, the second sintering temperature is 950°C to 1100°C. Exemplarily, the first sintering temperature can be any one of 950°C, 1000°C, 1050°C, or 1100°C, or any ratio between any two of them; the second sintering will cause the second particles to form spherical Li5FeO4 with a carbon coating layer containing CNTs.

[0097] In a specific embodiment of the present invention, Li5FeO4 is divided into first particles and second particles, and the first particles and second particles are separated by a high-speed centrifuge; preferably, the centrifugal force of the high-speed centrifuge is 8000g~10000g.

[0098] As an example, a high-speed centrifuge is used to separate Li5FeO4 into first and second particles with different median particle sizes. In a preferred embodiment, the centrifugal force of the high-speed centrifuge can be any one of 8000g (g is the acceleration due to gravity), 9000g, or 10000g, or any ratio between any two. This allows for the graded coating of particles of different sizes in subsequent processes.

[0099] In a specific embodiment of the present invention, large and small particles are mixed using a fixed-bed mixing device, wherein the mixing is carried out in an inert gas atmosphere with a flow rate of 60 m / s. 3 / h~90m 3 / h, the mixing time is 1h~2h.

[0100] As an example, a fixed-bed apparatus is used to mix particles of different sizes. The mixing process can be carried out in an environment with nitrogen, helium, or argon, and the flow rate of the inert gas can be 60 m / s. 3 / h、65m 3 / h、70m 3 / h、75m 3 / h、80m 3 / h、85m 3 / h, or 90m 3Any ratio of one or both of the above values ​​in / h; by limiting the above gas flow rate, it is possible to ensure that the particles of different sizes are evenly dispersed, thereby achieving a better compaction density and giving the battery excellent capacity density. If it is less than the above range, the particles of different sizes will not be completely dispersed; if it is greater than the above range, the flow rate of the particles of different sizes will be too fast, the friction between the particles will be greater, and it will be easy to damage the carbon coating layer on the surface of the particles, thus affecting the performance of the battery.

[0101] According to another aspect of the present invention, the present invention provides a lithium-rich lithium iron ferrite lithium supplement, comprising: a lithium-rich lithium iron ferrite lithium supplement prepared by the preparation method of the lithium-rich lithium iron ferrite lithium supplement in any of the above embodiments; the lithium-rich lithium iron ferrite lithium supplement comprises Li5FeO4, wherein Li5FeO4 comprises first particles and second particles, wherein the median particle size D of the first particles is... v50 Let x be the median particle size D of the second particle. v50 Let y be the integer part of the integer part, and x > y.

[0102] The first particle has at least a portion of its surface coated with a first carbon coating layer, the first carbon coating layer including a first carbon nanotube; the second particle has at least a portion of its surface coated with a second carbon coating layer, the second carbon coating layer including a second carbon nanotube.

[0103] As an example, the lithium-rich lithium iron ferrite supplement is prepared through any of the above embodiments. The prepared lithium-rich lithium iron ferrite supplement also has the effects and advantages of any of the above embodiments, which will not be repeated here. This lithium-rich lithium iron ferrite supplement includes Li5FeO4 particles of different sizes, namely first particles and second particles. At least a portion of the surface of the first particle is coated with a first carbon coating layer, which contains first carbon nanotubes. It is understood that the first carbon nanotubes include, but are not limited to, those with an aspect ratio of 10. 3 Multi-walled carbon nanotubes with an aspect ratio of 10 4 Multi-walled carbon nanotubes with an aspect ratio of 10 5 The second particle contains one or more of the single-walled carbon nanotubes; the first carbon coating layer contains the first carbon nanotubes, which can effectively enable large particles to form a highly conductive network and effectively improve the dynamic performance of large particles, thereby improving the energy density of the battery. At least a portion of the surface of the second particle is coated with a second carbon coating layer containing the second carbon nanotubes. In a preferred embodiment, the surface of the second particle is formed with a spherical second carbon coating layer; the second carbon coating layer contains the second carbon nanotubes, which can be understood to include, but is not limited to, those with an aspect ratio of 10. 3 Multi-walled carbon nanotubes with an aspect ratio of 10 4 One or more of the multi-walled carbon nanotubes.

[0104] In a specific embodiment of the present invention, the thickness of the first carbon coating layer is 5 nm to 10 nm. For example, the thickness of the first carbon coating layer can be any one of 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm, or any ratio between any two. By limiting the thickness of the first carbon coating layer, good ion transport performance of the large particles can be ensured. Exceeding the above range may affect ion transport; if it is less than the above range, it may affect the embedding of the first carbon nanotubes, thereby affecting the battery capacity.

[0105] In a specific embodiment of the present invention, the thickness of the second carbon coating layer is 20 nm to 30 nm. Exemplarily, the thickness of the second carbon coating layer can be any one of 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, or 30 nm, or any ratio between any two. A thickness within the above range allows the small particles to possess good ion transport performance, while also effectively embedding the second carbon nanotubes into the second carbon coating layer.

[0106] In a specific embodiment of the present invention, the mass percentage of the first carbon nanotube is 0.4wt% to 2wt% based on the mass of the large particles. For example, the mass percentage of the first carbon nanotube can be any one of 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2.0wt%, or any ratio between any two of these values.

[0107] In a specific embodiment of the present invention, the mass percentage of the second carbon nanotube is 0.4wt% to 2wt% based on the mass of the small particles. For example, the mass percentage of the second carbon nanotube can be any one of 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2.0wt%, or any ratio between any two of these values. By limiting the content of the first carbon nanotube in the large particles and the content of the second carbon nanotube in the small particles, the particles of both sizes can have good kinetic properties, and a highly conductive network can be effectively formed on both particles, thereby improving the release efficiency of the lithium replenishment agent.

[0108] According to another aspect of the present invention, the present invention provides a battery comprising: a lithium-rich lithium ferrite supplement prepared by the method for preparing the lithium-rich lithium ferrite supplement in any of the above embodiments.

[0109] In specific embodiments of the present invention, the lithium-rich lithium iron ferrite supplement agent in any of the above embodiments.

[0110] Optionally, the battery may include an outer packaging that can be used to encapsulate the aforementioned electrode assembly and electrolyte. The outer packaging of the battery can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. Specifically, the rigid shell may include a housing and a cover plate, wherein the housing may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity, the housing having an opening communicating with the receiving cavity, and the cover plate being able to cover the opening to close the receiving cavity, the electrode assembly being encapsulated in the aforementioned receiving cavity, and the electrolyte being immersed in the electrode assembly; it can also be a soft pack, such as a pouch soft pack; the material of the soft pack can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0111] The present invention does not impose any particular restrictions on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape, and those skilled in the art can choose according to specific practical needs.

[0112] According to another aspect of the present invention, an electrical device is also provided, comprising: the battery in any of the above embodiments. Thus, the electrical device possesses all the features and advantages of the battery in the above-described technical solutions, which will not be repeated here. Specifically, the battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0113] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0114] Example 1 Preparation of S11 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s. The inlet temperature was 165℃, the outlet temperature was 90℃, and the atomizing disc speed was 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min to obtain Li5FeO4.

[0115] S12. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 9000g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0116] S13, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The mixture (25 μm) of sucrose and CNTs was prepared, with a small amount of PVP (polyvinylpyrrolidone) added for dispersion. The molar ratio of the first particle to sucrose to CNTs to PVP was 100:0.5:1:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then subjected to a second drying process in a spray dryer with an inlet temperature of 170°C, an outlet temperature of 80°C, and a spray disc rotation speed of 14000 rpm. The outlet was then connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress the high-temperature decomposition of LFCs. The temperature was instantly raised to 800°C, resulting in graphitization of the carbon shell and embedding of CNTs, with a CNT content of 0.98 wt%, yielding large particles.

[0117] S14, Small particle coating: The separated second particle (D) is coated with small particles. v50 Li₅FeO₄ (7μm), sucrose, and CNTs were mixed, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:2:1:0.8. The mixture was ultrasonically mixed to achieve a solid content of 25%. The solution was then fed into a spray dryer for third drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, where a N₂ / Ar mixed gas (5mol% H₂) was introduced to suppress the high-temperature decomposition of LFCs. The temperature was instantly raised to 1000℃, causing the carbon shell to graphitize and embed CNTs, achieving spherical coating with a CNT content of 0.96wt%, resulting in small particles.

[0118] S15. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed equipment. The large and small particles are loaded into a fixed bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0119] Example 2 Preparation of S21 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 11:1. The milling speed was 600 rpm for 3 hours. After ball milling, the mixture was first dried using a spray dryer for 30 seconds at an inlet temperature of 165℃, an outlet temperature of 90℃, and a spray disc speed of 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 15 minutes to obtain Li5FeO4.

[0120] S22. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 10000g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0121] S23, Large particle coating: The first separated Li5FeO4 (D) particles are coated with large particles. v50 The first particle (30 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNTs to PVP was 100:1:1:0.8. The mixture was ultrasonically mixed until homogeneous, and the solid content of the solution was 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170°C and atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress the high-temperature decomposition of LFCs. The temperature was then instantaneously raised to 800°C (0.5 s), resulting in graphitization of the carbon shell and embedding of CNTs, with a CNT content of 0.97 wt%, thus obtaining large particles.

[0122] S24, Small particle coating: The separated second particle Li5FeO4 (D v50A mixture of 9μm particles, sucrose, and CNTs was prepared, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:1:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5mol% H2) was introduced to suppress the high-temperature decomposition of LFCs, and the temperature was instantaneously raised to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, resulting in small particles with a CNT content of 0.95wt%.

[0123] S25. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0124] Example 3 Preparation of S31 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 8:1. The milling speed was 300 rpm for 2 hours. After ball milling, the mixture was first dried using a spray dryer for 10 seconds at an inlet temperature of 165℃, an outlet temperature of 90℃, and a spray disc speed of 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 10 minutes to obtain Li5FeO4.

[0125] S32. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 8000g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0126] S33, Large particle coating: The first separated Li5FeO4 (D v50The carbon shell (20 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNTs to PVP was 100:1.5:1:0.8. The mixture was ultrasonically mixed until homogeneous, and the solid content of the solution was 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170°C and atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress the high-temperature decomposition of LFCs. The temperature was then instantaneously raised to 800°C (0.5 s), resulting in graphitization of the carbon shell and embedding of CNTs, with a CNT content of 0.96 wt%, thus obtaining large particles.

[0127] S34, Small particle coating: The separated second particle Li5FeO4 (D v50 A mixture of 5μm particles, sucrose, and CNTs was prepared, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:5:1:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5mol% H2) was introduced to suppress the high-temperature decomposition of LFCs, and the temperature was instantaneously raised to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, resulting in a CNT content of 0.93wt%, yielding small particles.

[0128] S35. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0129] Example 4 Preparation of S41 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 10:1. The milling speed was 400 rpm for 2.3 h. After ball milling, the mixture was first dried using a spray dryer for 15 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 12 min to obtain Li5FeO4.

[0130] S42. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 8500g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0131] S43, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The carbon shell (27 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNTs to PVP was 100:1:0.5:0.8. The mixture was ultrasonically mixed until homogeneous, and the solid content of the solution was 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170°C and atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress the high-temperature decomposition of LFCs. The temperature was then instantaneously raised to 800°C (0.5 s), resulting in graphitization of the carbon shell and embedding of CNTs, with a CNT content of 0.48 wt%, thus obtaining large particles.

[0132] S44, Small particle coating: The separated second particle Li5FeO4 (D v50 A mixture of 5μm particles, sucrose, and CNTs was prepared, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:0.5:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, where a N2 / Ar mixed gas (5mol% H2) was introduced to suppress the high-temperature decomposition of LFCs, and the temperature was instantaneously raised to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, resulting in a CNT content of 0.47wt%, yielding small particles.

[0133] S45. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed-bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0134] Example 5 Preparation of S51 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min to obtain Li5FeO4.

[0135] S52. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 8300g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0136] S53, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The solution (24 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNT to PVP was 100:1:1.5:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation followed by instantaneous heating to 800℃ (0.5s) graphitizes the carbon shell and embeds CNTs, with a CNT content of 0.97wt%, resulting in large particles.

[0137] S54, Small particle coating: The separated second particle Li5FeO4 (D v50The mixture (6μm particle size) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:1.5:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 0.95wt%, resulting in small particles.

[0138] S55. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0139] Example 6 Preparation of S61 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s. The inlet temperature was 165℃, the outlet temperature was 90℃, and the atomizing disc speed was 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min to obtain Li5FeO4.

[0140] S62. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 8800g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0141] S63, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50The first particle (28 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNT to PVP was 100:1.5:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation followed by instantaneous heating to 800℃ (0.5s) graphitizes the carbon shell and embeds CNTs, with a CNT content of 1.8wt%; resulting in large particles.

[0142] S64, Small particle coating: The separated second particle Li5FeO4 (D v50 The mixture (5μm particles) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 1.8wt%; small particles were obtained.

[0143] S65. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0144] The SEM image of the lithium-rich lithium iron phosphate supplement provided in Example 6 is shown in the attached image. Figure 1 As shown, by Figure 1 It can be seen that the outer surface of the Li5FeO4 material is completely covered with carbon nanotubes. The large particles are basically covered according to their morphology, while the medium and small particles exhibit a near-spherical structure, thus achieving the design objective.

[0145] Example 7 Preparation of S71 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min to obtain Li5FeO4.

[0146] S72. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 9500g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0147] S73, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The first particle (25 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNT to PVP was 100:1.5:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation followed by instantaneous heating to 800℃ (0.5s) graphitizes the carbon shell and embeds CNTs, with a CNT content of 1.8wt%; resulting in large particles.

[0148] S74, Small particle coating: The separated second particle Li5FeO4 (D v50 The mixture (7μm particle size) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 1.8wt%; small particles were obtained.

[0149] S75. Particle Mixing: The coated particles are mixed in a 1:1 ratio of large particles to small particles on a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio. Nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0150] Example 8 Preparation of S81 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min, yielding Li5FeO4.

[0151] S82. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 9000g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0152] S83, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The first particle (25 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNT to PVP was 100:1.5:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation followed by instantaneous heating to 800℃ (0.5s) graphitizes the carbon shell and embeds CNTs, with a CNT content of 1.8wt%; resulting in large particles.

[0153] S84, Small particle coating: The separated second particle Li5FeO4 (D v50The mixture (7μm particle size) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:3:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 1.8wt%; small particles were obtained.

[0154] S85. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:2 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed-bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0155] Example 9 Preparation of S91 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min, yielding Li5FeO4.

[0156] S92. Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 10000g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0157] S93, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50The first particle (28 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle to sucrose to CNT to PVP was 100:0.5:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation, followed by instantaneous heating to 800℃ (0.5s), graphitizes the carbon shell and embeds CNTs, with a CNT content of 2wt%; resulting in large particles.

[0158] S94, Small particle coating: The separated second particle Li5FeO4 (D v50 The mixture (4μm) of sucrose and CNTs was prepared, with a small amount of PVP added for dispersion. The molar ratio of the second particle to sucrose to CNTs to PVP was 100:2:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 2wt%; small particles were obtained.

[0159] S95. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed-bed pipeline according to the above ratio, and nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0160] Example 10 Preparation of S101 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min, yielding Li5FeO4.

[0161] S102, Separation of the first and second particles: Li5FeO4 is separated into the first and second particles using a high-speed centrifuge. The centrifugal force is 9300g to separate the first particle. The separation is carried out under a nitrogen atmosphere.

[0162] S103, Large Particle Coating: The first separated Li5FeO4 (D) particles are coated... v50 The solution (25 μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the first particle: glucose: CNT: PVP was 100:1.5:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for secondary drying at an inlet temperature of 170℃ and an atomizing disc speed of 14000 rpm. The outlet was connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5 mol% H2) was introduced to suppress Fe. 2+ Oxidation followed by instantaneous heating to 800℃ (0.5s) graphitizes the carbon shell and embeds CNTs, with a CNT content of 1.8wt%; resulting in large particles.

[0163] S104, Small particle coating: The separated second particle Li5FeO4 (D v50 The solution (7μm) was mixed with sucrose and CNTs, with a small amount of PVP added for dispersion. The molar ratio of the second particle to glucose to CNTs to PVP was 100:3:2:0.8. The mixture was ultrasonically mixed until homogeneous, resulting in a solution with a solid content of 25%. The solution was then fed into a spray dryer for third-stage drying, with an inlet temperature of 170℃, an outlet temperature of 80℃, and a spray disc rotation speed of 16000 rpm. The outlet was then connected to a Joule heating sintering device, through which a N2 / Ar mixed gas (5mol% H2) was introduced to suppress Fe. 2+ Oxidation was performed, followed by a rapid heating to 1000℃ (0.1s). The carbon shell was graphitized and embedded with CNTs, with a CNT content of 1.8wt%; small particles were obtained.

[0164] S105. Particle Mixing: The coated particles are mixed at a ratio of large particles to small particles of 1:1.5 in a gas fluidized bed apparatus. Large and small particles are loaded into a fixed bed pipeline according to the above ratio. Nitrogen gas is introduced into the pipeline to cause the large and small particles to flow and mix. The nitrogen flow rate is 70 m / s. 3 / h (to reduce contact between particles and between particles and equipment, and to retain the original coating layer to the greatest extent), the mixing time is 2h to obtain lithium-rich lithium iron ferrite supplement.

[0165] Comparative Example 1 (without CNTs added and without graded coating) Preparation of S111 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s. The inlet temperature was 165℃, the outlet temperature was 90℃, and the atomizing disc speed was 18000 rpm to obtain the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min to obtain Li5FeO4.

[0166] S112. Mix Li5FeO4 powder, sucrose, and CNT, and add a small amount of PVP for dispersion. The molar ratio of Li5FeO4:sucrose:CNT:PVP (polyvinylpyrrolidone) is 100:1:1:0.8. Mix the mixture evenly by ultrasonication. The solid content of the solution is 25%.

[0167] S113. The solution is added to a spray dryer for drying, with an inlet temperature of 170℃ and an atomizing disc rotation speed of 14000 rpm. The outlet is connected to a Joule heating sintering device, and a N2 / Ar mixed gas (5mol% H2) is introduced to suppress the high-temperature decomposition of LFC. The temperature is instantly raised to 800℃ (0.5s), resulting in graphitization of the carbon shell and embedding of CNTs, with a CNT content of 0.97wt%.

[0168] Comparative Example 2 (CNTs added, no graded encapsulation) Preparation of S121 and Li5FeO4: 5.2 mmol of Fe(NO3)3·9H2O was used as the iron source, and 1 mmol of LiOH·H2O was used as the lithium source. The two were mixed in a ball mill with anhydrous ethanol as the solvent. The mass ratio of anhydrous ethanol to solids was 9:1. The milling speed was 450 rpm, and the time was 1.5 h. After ball milling, the mixture was first dried using a spray dryer for 20 s at an inlet temperature of 165℃ and an outlet temperature of 90℃. The atomizing disc speed was 18000 rpm, yielding the precursor. The precursor powder was then added to a radio frequency plasma reactor for activation treatment. The reactor frequency was 14 MHz, the power was 450 W, and the reaction was carried out in an Ar / H2 (9:1) mixed atmosphere at a pressure of 60 Pa for 13 min, yielding Li5FeO4.

[0169] S122. Mix the unseparated Li5FeO4 powder, sucrose, and CNTs, and add a small amount of PVP for dispersion. The molar ratio of Li5FeO4:sucrose:CNT:PVP is 100:1:1:0.8. Mix the mixture evenly by ultrasonication. The solid content of the solution is 25%.

[0170] S123. The solution is added to a spray dryer for drying, with an inlet temperature of 170℃ and an atomizing disc rotation speed of 16000 rpm. The outlet is connected to a Joule heating sintering device, and an N2 / Ar mixed gas (5mol% H2) is introduced to suppress the high-temperature decomposition of LFC. The temperature is instantly raised to 1000℃ (0.1s), the carbon shell is graphitized and CNTs are embedded, and the CNT content is 0.98wt%, thus obtaining a lithium supplement.

[0171] Test method: The prepared LFC lithium supplement, conductive agent SP, and binder PVDF were mixed into a slurry according to the following mass ratio: LFC:SP:PVDF = 97.5%:1%:1.5%. After mixing, the slurry was coated and compacted, and the compaction of different lithium supplement types was tested under the same pressure.

[0172] The specific procedure for the compaction test is as follows: The coated electrode sheet is rolled under gradient pressure. The initial rolling pressure is set to 10t, and the roller gap is set to 30μm. The pressure is increased by 2t each time until the electrode sheet reaches maximum compaction. The condition for maximum compaction is whether the electrode sheet is translucent after being folded three times. The compaction corresponding to the thickness of the previous rolling after the translucent state is reached is taken as the maximum compaction of the electrode sheet.

[0173] Compacted density = Areal density / (Electrode thickness - Foil thickness).

[0174] The performance of the lithium replenishment agent was tested using a coin cell method, with the lithium replenishment agent electrode as the positive electrode and the lithium electrode as the negative electrode. The electrolyte used was EC (ethylene carbonate) / EMC (ethyl methyl carbonate) / DMC (dimethyl carbonate) = 1:1:1, and 1 mol / L LiPF6 was used as the lithium salt. The test rate was 0.05C, and the voltage range was 2.0V~4.5V.

[0175] Specific procedures for electrical performance testing: The specific capacity of the lithium replenishment agent was tested using the Blue Battery testing system. Test temperature is 25℃: 1. Stand still for 2 hours; 2. Charge at 0.05C to 4.2V, charging capacity is C1; 3. Stand still for 10 minutes; 4. Discharge at 0.05C to 2.0V, discharging capacity is C2.

[0176] First charge specific capacity = C1 / (m 极片粉料 ×wt 补锂剂 ); First discharge specific capacity = C2 / (m 极片粉料 ×wt 补锂剂 ); First-time efficiency = First discharge specific capacity / First charge specific capacity × 100%.

[0177] The test results are shown in Table 1 below.

[0178] Table 1 As shown in Table 1, compared to the comparative example, the specific capacity of the examples showed improvements in both compaction and charging, indicating that graded coating can significantly improve the performance of the lithium replenisher. This is mainly because graded coating allows for more precise coating and improves the coating interface. In Examples 1-3, the specific capacity showed a trend of first increasing and then decreasing as the carbon layer thickness increased. This is because when the carbon layer content was low, the carbon layer could not completely coat the LFC, resulting in slightly poorer carbon nanotube insertion into the carbon layer, slightly lower conductivity, and slightly lower charging specific capacity. When the carbon layer content was too high, the coating thickness was too large, which was not conducive to lithium-ion insertion and extraction, also leading to a decrease in specific capacity. In Examples 2, 4-6, and 9, the charging specific capacity gradually increased with the increase in carbon nanotube content, indicating that increasing the carbon nanotube content also improved conductivity and promoted the performance of the lithium replenisher. The compaction showed a trend of first increasing and then decreasing, mainly because excessively high carbon content would also reduce the compaction density, leading to a decreasing trend in compaction. In Examples 1, 7, and 8, the compaction first increased and then decreased as the number of small particles increased. This is mainly because, with a fixed particle size, increasing the number of small particles within a certain range is beneficial for filling gaps. Once the gaps are filled, continuing to increase the number of small particles will worsen the compaction.

[0179] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0180] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0181] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0182] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a lithium-rich lithium iron ferrite lithium supplement, characterized in that, Includes the following steps: Iron source and lithium source are mixed and ground, and after the first drying, a precursor is obtained. The precursor is then activated to form Li5FeO4. The Li5FeO4 is divided into first particles and second particles, wherein the median particle size D of the first particles is... v50 Let x be the median particle size D of the second particle. v50 Let y be a given value, and x > y; The first particle, the first carbon source, the first carbon nanotube, the first dispersant and the first solvent are mixed to form a first slurry. The first slurry is then subjected to a second drying and a first sintering to obtain large particles. The second particle, the second carbon source, the second carbon nanotube, the second dispersant, and the second solvent are mixed to form a second slurry. The second slurry is then dried in a third process and sintered in a second process to obtain small particles. The large particles and the small particles are mixed to obtain a lithium-rich lithium ferrite supplement.

2. The preparation method of the lithium-rich lithium iron ferrite supplement agent according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (5): (1) The x satisfies: 20μm≤x≤30μm; (2) The y satisfies: 3μm≤y≤10μm; (3) The first carbon nanotube comprises: an aspect ratio of 10 3 ~10 4 Multi-walled carbon nanotubes with an aspect ratio greater than 10 4 At least one of the single-walled carbon nanotubes, preferably, the first carbon nanotube comprises an aspect ratio greater than 10. 4 Single-walled carbon nanotubes; (4) The second carbon nanotube comprises: an aspect ratio of 10 3 ~10 4 Multi-walled carbon nanotubes; (5) The mass ratio of the large particles to the small particles is 1:(1~2).

3. The preparation method of the lithium-rich lithium iron ferrite supplement agent according to claim 1, characterized in that, The molar ratio of the first particle, the first carbon source, the first carbon nanotube, and the first dispersant is 100:(0.5~1.5):(0.5~2):0.8; And / or, the molar ratio of the second particle, the second carbon source, the second carbon nanotube, and the second dispersant is 100:(2~5):(0.5~2):0.

8.

4. The preparation method of the lithium-rich lithium iron ferrite supplement agent according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (8): (1) The iron source includes at least one of ferric nitrate and ferric oxide; (2) The lithium source includes at least one of lithium hydroxide and lithium carbonate; (3) The first carbon source includes at least one of sucrose, glucose, and starch; (4) The first dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol; (5) The first solvent includes at least one of anhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate; (6) The second carbon source includes at least one of sucrose, glucose, and starch; (7) The second dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol; (8) The second solvent includes at least one of polyanhydrous ethanol, N-methylpyrrolidone, ethylene carbonate, and dimethyl carbonate.

5. The preparation method of the lithium-rich lithium iron ferrite supplement agent according to claim 1, characterized in that, The activation process includes: The precursor was added to the radio frequency plasma reactor for activation; The radio frequency plasma reactor has a frequency of 13MHz~16MHz, a power of 300W~500W, a pressure of 40Pa~90Pa, and is in an inert gas atmosphere. The activation temperature is 200℃~300℃, and the activation time is 10min~15min.

6. The method for preparing lithium-rich lithium iron ferrite supplementary agent according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (9): (1) The solid content of the first slurry is 20%~30%, preferably, the solid content of the first slurry is 25%; (2) The solid content of the second slurry is 20%~30%, preferably 25%; (3) The first drying is spray drying, wherein the inlet temperature is 160℃~165℃ and the outlet temperature is 90℃~95℃; (4) The second drying is spray drying, wherein the inlet temperature is 170℃~180℃ and the outlet temperature is 80℃~85℃; (5) The third drying is spray drying, wherein the inlet temperature is 170℃~180℃ and the outlet temperature is 80℃~85℃; (6) The temperature of the first sintering is 700℃~900℃; (7) The second sintering temperature is 950℃~1100℃; (8) The first particle and the second particle are separated by a high-speed centrifuge; preferably, the centrifugal force in the high-speed centrifuge is 8000g~10000g. (9) The mixing of the large particles and the small particles is carried out using a fixed-bed equipment, wherein the mixing is performed in an inert gas atmosphere at a flow rate of 60 m / s. 3 / h~90m 3 / h, the mixing time is 1h~2h.

7. A lithium-rich lithium iron phosphate lithium supplement, characterized in that, This includes lithium-rich lithium iron ferrite supplements prepared by the preparation method according to any one of claims 1 to 6; The lithium-rich lithium iron phosphate supplement comprises Li5FeO4, which includes first particles and second particles, wherein the median particle size D of the first particles is... v50 Let x be the median particle size D of the second particle. v50 Let y be a given value, and x > y; The first particle has at least a portion of its surface coated with a first carbon coating layer, the first carbon coating layer including a first carbon nanotube; the second particle has at least a portion of its surface coated with a second carbon coating layer, the second carbon coating layer including a second carbon nanotube.

8. The lithium-rich lithium iron phosphate supplement agent according to claim 7, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) The thickness of the first carbon coating layer is 5 nm to 10 nm; (2) The thickness of the second carbon coating layer is 20 nm to 30 nm; (3) Based on the mass of the large particles, the mass percentage of the first carbon nanotube is 0.4wt%~2wt%; (4) Based on the mass of the small particles, the mass percentage of the second carbon nanotube is 0.4wt%~2wt%.

9. A battery, characterized in that, include: The lithium-rich lithium iron ferrite supplement prepared by the preparation method according to any one of claims 1 to 6; And / or, the lithium-rich lithium iron ferrite supplement agent according to any one of claims 7 to 8.

10. An electrical device, characterized in that, include: The battery according to claim 9.

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