Positive electrode sheet with built-in magnetic field, its preparation method and application

Abstract

This invention discloses a positive electrode sheet with a built-in magnetic field, its preparation method, and its application, belonging to the field of lithium-ion battery technology. The positive electrode material in this positive electrode sheet is a coated lithium-rich manganese-based material with a magnetite (Fe3O4) coating layer on its surface. Utilizing the ferrimagnetism of Fe3O4, a magnetic field is applied during the coating process, causing magnetic particles to rotate freely in the liquid medium and align along the magnetic field direction. Subsequently, drying is used to fix this ordered structure, thus constructing an ordered and stable built-in magnetic field within the electrode sheet. This built-in magnetic field can generate magnetohydrodynamic effects or spin polarization effects on the migration of lithium ions, promoting rapid lithium ion transport along the electrode thickness direction, thereby significantly improving the rate performance of the material. Lithium-ion batteries prepared with this electrode sheet exhibit excellent rate performance and cycle stability, and the built-in magnetic field can significantly suppress voltage decay during cycling, showing promising application prospects in the field of lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion batteries, and particularly to a positive electrode sheet with a built - in magnetic field, its preparation method and application. Background Art

[0002] As the most mainstream electrochemical energy storage device at present, lithium - ion batteries have been widely used in fields such as portable electronic devices, electric vehicles and large - scale energy storage. With the continuous increase in the market demand for the energy density of lithium - ion batteries, the development of high - capacity and high - voltage cathode materials has become the core direction to improve the energy density of lithium - ion batteries. The chemical general formula of the lithium - rich manganese - based material is xLi2MnO3·(1 - x)LiMO2, where M is at least one of Ni, Co, Mn, and 0 < x < 1. Due to its unique anion redox mechanism, it can achieve a reversible specific capacity of more than 250 mAh / g, which is much higher than that of traditional layered oxide cathode materials. It is regarded as one of the most promising cathode materials for next - generation high - energy - density lithium - ion batteries. However, this material faces many challenges in practical applications, such as large first - cycle irreversible capacity loss, poor rate performance, and serious voltage decay during cycling.

[0003] To overcome the above problems, surface coating is one of the widely adopted modification strategies at present. By constructing a coating layer on the surface of the lithium - rich manganese - based material, the direct contact between the electrolyte and the active material can be effectively blocked, and side reactions and the dissolution of transition metals can be inhibited, thereby improving the cycle stability. However, traditional coating layers usually do not have electrochemical activity. While improving the interface stability, they often sacrifice part of the capacity and rate performance. How to further enhance the lithium - ion transport kinetics inside the electrode while stabilizing the material surface is still a difficult point in current research.

[0004] In recent years, the magnetic - field effect has received extensive attention in the field of electrochemical energy storage. Research shows that an external magnetic field can significantly affect electrode reaction kinetics, ion migration behavior and interfacial charge - transfer processes through magnetohydrodynamic effects, spin - polarization effects or the directional arrangement of magnetic species. Some researchers have tried to introduce magnetic materials into the electrode and apply an external magnetic field during battery operation to improve the electrochemical performance. However, the introduction of an external magnetic field increases the complexity and volume of the battery system, which is not conducive to practical applications; at the same time, the regulation effect of randomly distributed magnetic particles in the electrode on the electrochemical performance is very limited. If an orderly and stable built - in magnetic field can be synchronously constructed inside the material during coating by appropriate means, synergistically improving the material interface stability and optimizing ion - transport kinetics, thereby improving the rate performance and cycle life of the material, it has important significance for the design and preparation of high - performance lithium - rich manganese - based cathode materials. Summary of the Invention

[0005] Aiming at the problems in the prior art, the present invention aims to provide a positive electrode plate with a built-in magnetic field, a preparation method thereof, and an application thereof. The present invention constructs a positive electrode material with a built-in magnetic field by coating with magnetic materials and combining magnetic field orientation treatment. Through the synergistic effect of surface magnetic coating and magnetic field orientation treatment, an ordered built-in magnetic field is constructed inside the lithium-rich manganese-based material, in order to enhance the lithium ion transport kinetics inside the electrode while stabilizing the material interface and suppressing side reactions, thereby synergistically improving the rate performance and cycle stability of the lithium-rich manganese-based material.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: The first aspect of the present invention is to provide a preparation method of a positive electrode plate with a built-in magnetic field, including the following steps: Prepare a lithium-rich manganese-based material; the chemical general formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiMO2, where: M is a transition metal, which is at least one of Ni, Co, and Mn, and 0 < x < 1; the specific method is: dissolve the acetate of the transition metal in a mixed solution of deionized water and glycerol according to the stoichiometric ratio of the target product, add an appropriate amount of cetyltrimethylammonium bromide (CTAB) and urea, stir and dissolve, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours; after natural cooling, the product is washed alternately with deionized water and ethanol, dried, and calcined in air at 500 °C for 5 hours to obtain a transition metal oxide; mix and grind the oxide with 5 mol% excess lithium hydroxide (LiOH·H2O), and calcine in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0007] S2. Disperse the lithium-rich manganese-based material in water, add an appropriate amount of organic iron source, mix evenly and then evaporate the water to obtain a precursor powder. Sinter the precursor powder in an inert atmosphere to form a magnetite coating layer on the surface of the lithium-rich manganese-based material, and obtain a coated lithium-rich manganese-based material; S3. Mix the coated lithium-rich manganese-based material with a conductive agent, a binder, and a solvent to prepare a positive electrode slurry; S4. Coat the positive electrode slurry on an aluminum foil current collector, apply a magnetic field for magnetization treatment during the coating process, and after vacuum drying and rolling treatment, obtain a lithium-rich manganese-based positive electrode plate with a built-in magnetic field.

[0008] Preferably, the organic iron source is iron acetylacetonate, ferrocene, iron oleate, etc., and these iron-containing organic substances can form magnetite after sintering in an inert atmosphere.

[0009] Preferably, the amount of organic iron source added is 0.5% to 10% of the mass of the lithium-rich manganese-based material. When the amount added is less than 0.5%, the iron content is too low to effectively modify the surface or bulk phase of the material; when it is more than 10%, excessive iron can easily block lithium-ion transport channels and degrade electrochemical performance.

[0010] Preferably, the sintering temperature is 300~600℃, the sintering time is 2~10 hours, and the inert atmosphere is argon or the like. When the sintering temperature is below 300℃, the organic iron source decomposes incompletely, the product has poor crystallinity and residual organic impurities; when the temperature is above 600℃, the iron component is over-oxidized to form non-magnetic ferric oxide (Fe2O3), instead of the target magnetic magnetite (Fe3O4).

[0011] Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes, and graphene, and the binder is polyvinylidene fluoride, etc.

[0012] Preferably, the strength of the magnetic field is 0.1 to 1.5 Tesla, and the magnetization treatment time is 1 to 30 minutes.

[0013] Preferably, the direction of the magnetic field is parallel or perpendicular to the coating direction, so as to utilize the magnetic anisotropy of the material to precisely control the orientation of the coating particles, thereby obtaining consistent and controllable electrode performance.

[0014] A second aspect of the present invention is to provide a positive electrode having a built-in magnetic field, the positive electrode being prepared by the preparation method described in the first aspect above.

[0015] The present invention also provides the application of the above-mentioned positive electrode with built-in magnetic field in lithium-ion batteries.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention uses iron-containing organic materials as the iron source to generate a uniform and stable magnetite coating layer in situ on the surface of lithium-rich manganese-based materials through high-temperature sintering. This coating layer acts as a physical barrier, effectively preventing direct contact between the electrolyte and the active material, suppressing side reactions and transition metal dissolution, and significantly improving the material's cycle stability. Furthermore, utilizing the ferrimagnetism of magnetite, a magnetic field is applied during the coating process, before the slurry has dried and solidified. This causes the magnetic particles to rotate freely in the liquid medium and align along the magnetic field direction. Drying then fixes this ordered structure, creating an ordered and stable built-in magnetic field within the electrode. This built-in magnetic field can induce magnetohydrodynamic or spin polarization effects on lithium ion migration, promoting rapid lithium ion transport along the electrode thickness, thereby significantly improving the material's rate performance. If a magnetic field is applied after battery assembly or during testing, the magnetic particles are already sealed inside the electrode by the binder, losing the physical conditions for directional movement and failing to achieve the ordered alignment effect of this invention. This invention does not require additional complex equipment or processes, avoids the problems of increased system complexity and volume caused by the introduction of external magnetic fields, has good compatibility with existing lithium-ion battery electrode fabrication processes, and has significant practical application advantages. Attached Figure Description

[0017] Figure 1 This is a transmission electron microscope image of the iron oxide-coated lithium-rich manganese-based material obtained in Example 1; Figure 2 X-ray diffraction patterns of lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1; Figure 3 The charge-discharge curves of batteries made from lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1 are shown. Figure 4 The cycling performance diagram shows the batteries made from the lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1. Figure 5 The rate performance diagram shows the batteries made from the lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1. Detailed Implementation

[0018] The technical solution of the present invention will now be described in detail through specific embodiments. This is to enable those skilled in the art to better understand and implement the present invention, but the embodiments are not intended to limit the present invention. Furthermore, unless otherwise specified, the preparation processes in the following embodiments are conventional methods in the prior art.

[0019] Example 1 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. Dissolve 0.8823 g Mn(CH3COO)2·4H2O, 0.2986 g Ni(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, transfer the solution to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours. After natural cooling, wash and dry the product alternately with deionized water and ethanol, and calcine it in air at 500 °C for 5 hours to obtain a transition metal oxide. Mix the oxide thoroughly with an excess of 5 mol% lithium hydroxide and grind it. Calcine it in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0020] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.05 g of acetylacetone iron, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 0.5 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 10 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0021] Example 2 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. 0.7941 g Mn(CH3COO)2·4H2O, 0.1941 g Ni(CH3COO)2·4H2O, 0.1943 g Co(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea were dissolved in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 180 °C for 10 hours. After natural cooling, the product was washed and dried alternately with deionized water and ethanol, and calcined in air at 500 °C for 5 hours to obtain a transition metal oxide. The oxide was thoroughly mixed and ground with an excess of 5 mol% lithium hydroxide, and calcined in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0022] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.05 g of acetylacetone iron, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 0.5 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 10 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0023] Example 3 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. Dissolve 0.8823 g Mn(CH3COO)2·4H2O, 0.2986 g Ni(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, transfer the solution to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours. After natural cooling, wash and dry the product alternately with deionized water and ethanol, and calcine it in air at 500 °C for 5 hours to obtain a transition metal oxide. Mix the oxide thoroughly with an excess of 5 mol% lithium hydroxide and grind it. Calcine it in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0024] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.05 g of ferrocene, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 0.5 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 10 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0025] Example 4 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. Dissolve 0.8823 g Mn(CH3COO)2·4H2O, 0.2986 g Ni(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, transfer the solution to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours. After natural cooling, wash and dry the product alternately with deionized water and ethanol, and calcine it in air at 500 °C for 5 hours to obtain a transition metal oxide. Mix the oxide thoroughly with an excess of 5 mol% lithium hydroxide and grind it. Calcine it in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0026] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.1 g of acetylacetone iron, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 0.5 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 10 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0027] Example 5 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. Dissolve 0.8823 g Mn(CH3COO)2·4H2O, 0.2986 g Ni(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, transfer the solution to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours. After natural cooling, wash and dry the product alternately with deionized water and ethanol, and calcine it in air at 500 °C for 5 hours to obtain a transition metal oxide. Mix the oxide thoroughly with an excess of 5 mol% lithium hydroxide and grind it. Calcine it in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0028] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.05 g of acetylacetone iron, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 1 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 10 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0029] Example 6 A method for preparing a positive electrode sheet with a built-in magnetic field includes the following steps: S1. Dissolve 0.8823 g Mn(CH3COO)2·4H2O, 0.2986 g Ni(CH3COO)2·4H2O, 0.2 g CTAB and 1 g urea in deionized water and glycerol (volume ratio 2:1). After stirring and dissolving, transfer the solution to a polytetrafluoroethylene-lined autoclave and react at 180 °C for 10 hours. After natural cooling, wash and dry the product alternately with deionized water and ethanol, and calcine it in air at 500 °C for 5 hours to obtain a transition metal oxide. Mix the oxide thoroughly with an excess of 5 mol% lithium hydroxide and grind it. Calcine it in air at 850 °C for 12 hours to obtain a lithium-rich manganese-based material.

[0030] S2. Disperse 1 g of lithium-rich manganese-based material in 20 mL of deionized water, add 0.05 g of acetylacetone iron, mix evenly, evaporate the solvent to obtain precursor powder, place the precursor powder in argon gas and sinter at 300 °C for 2 h to obtain iron oxide-coated lithium-rich manganese-based material. S3. The coated lithium-rich manganese-based material is mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added as a solvent to prepare a positive electrode slurry. S4. The positive electrode slurry is coated onto an aluminum foil current collector. During the coating process, a 0.5 T magnetic field is applied parallel to the aluminum foil for magnetization treatment for 30 min. After coating, the electrode is vacuum dried and rolled to obtain a lithium-rich manganese-based positive electrode sheet.

[0031] Comparative Example 1 Compared with Example 1, the difference in this comparative example lies in the process in step S4. In this comparative example, no magnetic field is applied during the coating process, i.e., the magnetization treatment is omitted; the other processes are the same as in Example 1. When the battery assembled from the positive electrode sheet obtained in this comparative example is subjected to performance testing, a 0.5 T magnetic field is applied for magnetization treatment for 10 min before the test.

[0032] Using the products prepared in the above embodiments or comparative examples as the positive electrode, lithium metal sheets as the negative electrode, a solution of 1.0 mol / L LiPF6 dissolved in ethylene carbonate (EC) / dimethyl carbonate (DMC) as the electrolyte, and a Celgard 2400 polypropylene microporous membrane as the separator, a CR2032 coin cell was assembled in an argon-filled glove box.

[0033] Reference Figure 1 , Figure 1 The image shows a transmission electron microscope (TEM) image of the iron oxide-coated lithium-rich manganese-based material obtained in Example 1. The image shows a uniform iron oxide nanolayer with a thickness of approximately 5-10 nm coated on the particle surface. The main body of the sample maintains a layered structure, with an interlayer spacing of approximately 0.245 nm on the surface, corresponding to the (311) crystal plane of the spinel phase Fe3O4. This surface coating effectively isolates the electrolyte from direct contact with the lithium-rich material, suppressing side reactions and the dissolution of transition metal ions during cycling. Simultaneously, the iron oxide layer exhibits good electronic conductivity, which helps reduce interfacial impedance.

[0034] Reference Figure 2 , Figure 2 The X-ray diffraction patterns of the lithium-rich manganese-based cathode sheets obtained in Example 1 and Comparative Example 1 are shown. The figures reveal that both exhibit a typical α-NaFeO2 layered structure with sharp and symmetrical diffraction peaks, indicating good crystallinity. A distinct superlattice diffraction peak appears between 20° and 25°, belonging to the C / 2m structure of the Li2MnO3 phase. Compared to Comparative Example 1, the intensity ratio of the (003) peak to the (104) peak in Example 1 is significantly enhanced, indicating that the built-in magnetic field promotes preferential crystal orientation along the (003) crystal plane, which is beneficial to the ion transport dynamics of the lithium-rich manganese-based material.

[0035] Reference Figure 3 , Figure 3 The first charge-discharge curves of the batteries fabricated from the lithium-rich manganese-based cathode sheets obtained in Example 1 and Comparative Example 1 are shown at a 0.1 C rate. Below 4.5 V, there is a sloping region corresponding to the oxidation reaction of the transition metal elements; a long plateau appears around 4.5 V, attributed to the activation of the Li₂MnO₃ component and the redox reaction of lattice oxygen. The discharge specific capacity of Example 1 is 278.2 mAh g⁻¹. -1 The initial Coulomb efficiency was 75.3%.

[0036] Reference Figure 4 , Figure 4 The graph shows the cycle performance of the batteries made from the lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1. As can be seen from the graph, Example 1 has a capacity retention rate of up to 85.7% after 200 cycles at a current density of 2 C.

[0037] Reference Figure 5 , Figure 5 The graph shows the rate performance of batteries made from lithium-rich manganese-based positive electrode sheets obtained in Example 1 and Comparative Example 1. The discharge specific capacities of Example 1 at current densities of 0.1, 0.5, 1, 2, 5, and 10 C are 277.8, 246.1, 220.4, 194.9, 161.7, and 132.6 mAh g, respectively. -1 When the rate of change returns to 0.1 C, the capacity recovers to 276.9 mAh g. -1 The ferric oxide coating helps suppress polarization and irreversible capacity loss at high magnification.

[0038] Example 1 above The charge-discharge performance of the coin cells assembled with Comparative Example 6 and Comparative Example 1 at a current density of 0.1 C is shown in Table 1.

[0039] Table 1 shows the charge-discharge performance of batteries prepared from the electrodes obtained in the examples and comparative examples.

[0040] As can be seen from Table 1, the battery assembled from the materials prepared in the embodiments of the present invention exhibits better performance compared to Comparative Example 1. This demonstrates that the preparation method of the present invention can significantly improve battery performance.

[0041] It should be noted that in other embodiments, the objective of this invention can be achieved when the experimental process meets the following conditions: Regarding the amount of organic iron source used, based on the mass of lithium-rich manganese-based material, the preferred amount is 0.5% to 10%, specifically 0.5%, 3%, 5%, 8%, or 10%, etc. The preferred sintering temperature is 300~600℃, specifically 300℃, 400℃, 500℃ or 600℃, etc.; the preferred sintering time is 2~10h, specifically 2h, 4h, 6h, 8h or 10h, etc. The magnetic field strength is preferably 0.1 to 1.5 Tesla, specifically 0.1 T, 0.5 T, 1 T, or 1.5 T, etc. The preferred magnetization time is 1 to 30 minutes, specifically 1 minute, 5 minutes, 15 minutes, or 30 minutes, etc. Those skilled in the art can make appropriate selections of the above process parameters according to actual needs, and all of them can achieve the purpose of this invention.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode sheet with a built-in magnetic field, characterized in that: It includes the following steps: Prepare a lithium-rich manganese-based material; Mix the lithium-rich manganese-based material and an organic iron source evenly to obtain a precursor powder; Place the precursor powder in an inert atmosphere for sintering to form a magnetite coating layer on the surface of the lithium-rich manganese-based material, and obtain a coated lithium-rich manganese-based material; Mix the coated lithium-rich manganese-based material, a conductive agent, a binder, and a solvent evenly to prepare a positive electrode slurry; Coat the positive electrode slurry on a current collector, apply a magnetic field for magnetization treatment during the coating process, and obtain the target product after drying and rolling treatments.

2. The preparation method according to claim 1, characterized in that: The chemical general formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiMO2, where: M is a transition metal, which is at least one of Ni, Co, and Mn, and 0 < x < 1; the preparation method of the lithium-rich manganese-based material is: mix the acetate of the transition metal, cetyltrimethylammonium bromide, and urea evenly in a dispersant, react in a heating environment, and obtain a transition metal oxide after calcination; mix and grind the transition metal oxide with lithium hydroxide, and obtain the lithium-rich manganese-based material after calcination again.

3. The preparation method according to claim 1, characterized in that: The organic iron source is at least one of iron acetylacetonate, ferrocene, and iron oleate.

4. The preparation method according to claim 1, characterized in that: [[ID=⑧]]The mass of the organic iron source is ⑩.⑪% to ⑫% of the mass of the lithium-rich manganese-based material.

5. The preparation method according to claim 1, characterized in that: [[ID=⑨]]The sintering temperature is ⑬ to ⑭ °C, and the sintering time is ⑮ to ⑯ hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that: [[ID=⑩]]The conductive agent is one or more of conductive carbon black, carbon nanotubes, and graphene, and the binder is polyvinylidene fluoride.

7. The preparation method according to any one of claims 1 to 5, characterized in that: [[ID=⑪]]The direction of the applied magnetic field is parallel or perpendicular to the coating direction.

8. The preparation method according to claim 7, characterized in that: [[ID=⑫]]The intensity of the magnetic field is ⑰ to ⑱ tesla, and the magnetization treatment time is ⑲ to ⑳ minutes.

9. A positive electrode plate with a built-in magnetic field, characterized in that: [[ID=⑬]]It is prepared by using the preparation method described in any one of claims ① to ⑧.

10. A lithium-ion battery, characterized in that: [[ID=⑭]]It includes a positive electrode plate as described in claim ⑨.

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