Positive electrode sheet, method for manufacturing the same, and battery

Abstract

The application relates to a positive electrode sheet, a preparation method thereof and a battery. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer coated on at least one side of the positive electrode current collector, wherein the positive electrode active layer comprises a positive electrode active material, the positive electrode active material comprises single crystal particles and / or quasi-single crystal secondary particles, the angle between the (003) crystal face of a plurality of primary crystal grains of the single crystal particles and / or quasi-single crystal secondary particles and the plane of the positive electrode current collector is 15-75 DEG, and the positive electrode active material satisfies at least one of the following conditions: the ratio of the diffraction peak intensity of the (003) crystal face to the (104) crystal face in the X-ray diffraction spectrum of the positive electrode active material is greater than or equal to 1.5; the half-peak width of the (003) crystal face diffraction peak is less than or equal to 0.15 DEG; and the texture coefficient of the (003) crystal face is greater than 1.5. The scheme provided by the application can effectively resist mechanical stress transmitted due to the volume change of the negative electrode, inhibit particle breakage and electrode sheet breakage, and thus significantly improve the cycle life of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to positive electrode sheets, their preparation methods, and batteries. Background Technology

[0002] Lithium-ion batteries, with their high energy density and long cycle life, have become core energy storage devices in consumer electronics, electric vehicles, and large-scale energy storage systems. To meet the ever-increasing demand for energy density, silicon-based materials (especially silicon-carbon composites) are considered an important development direction for next-generation anodes due to their extremely high theoretical specific capacity. However, silicon materials undergo approximately 300% volume expansion and contraction during lithium insertion and extraction. This inherent characteristic not only poses a challenge to the structural stability of the anode but also has a profound impact on the long-term cycle reliability of the entire battery system.

[0003] In related technologies, to address the volume change problem of silicon-based anodes, the main technical approaches include nano-sizing of silicon materials to reduce absolute strain, designing porous or hollow structures to reserve expansion space, developing novel elastic binders to buffer volume changes, and constructing robust carbon composite frameworks to limit the expansion of silicon particles. These strategies aim to alleviate the pulverization of anode materials, maintain the integrity of electrical contacts, and stabilize the solid electrolyte interface film, thereby improving the cycle performance of silicon-based anodes to some extent.

[0004] However, most of these studies focus on modifying and strengthening the negative electrode itself, while relatively neglecting the indirect mechanical effects of the drastic volume changes of the silicon-carbon negative electrode on other battery components, especially the positive electrode. During cycling, the periodic large-scale expansion and contraction of the negative electrode is transmitted to the positive electrode through the electrolyte and separator, producing a continuous "tug-of-war effect" on the positive electrode. This causes a sharp increase in battery internal resistance, rapid capacity decay, and ultimately leads to premature termination of battery cycle life.

[0005] Therefore, focusing solely on improving the negative electrode itself is insufficient to solve the failure problem of the entire battery system caused by mechanical interactions. It is necessary to re-examine the issue from a system perspective and seek new solutions. Summary of the Invention

[0006] To solve or partially solve the problems existing in the related technologies, this application provides a positive electrode sheet, a method for preparing the same, and a battery. The positive electrode can effectively resist the mechanical stress transmitted by the volume change of the negative electrode, suppress particle breakage and electrode sheet fracture, thereby significantly improving the cycle life of the battery.

[0007] A first aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive active layer coated on at least one side of the positive current collector. The positive active layer comprises a positive active material, which comprises single-crystal particles and / or quasi-single-crystal secondary particles. The (003) crystal planes of a plurality of primary grains of the single-crystal particles and / or the quasi-single-crystal secondary particles form an angle of 15° to 75° with the plane of the positive current collector, and the positive active material satisfies at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to the intensity of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°. The texture coefficient of the (003) crystal plane of the positive electrode active material is C, where C>1.5.

[0008] As an optional embodiment, the general formula of the single-crystal particles and / or single-crystal-like secondary particles is LiM. （1-x） A x O2, wherein M includes one or more of Ni, Co, and Mn; A is at least one magnetic doping element selected from Fe, Cr, Al, Mg, Zr, Ti, Y, W, Mo, Nb, Ta, and rare earth elements; 0≤x≤0.08.

[0009] As an optional embodiment, the percentage of the atoms of the doped magnetic element in all transition metal sites is 0.1 mol% to 2 mol%.

[0010] As an optional embodiment, the particle size of the single crystal particles and / or quasi-single crystal secondary particles is 8μm~20μm.

[0011] As an optional embodiment, the positive electrode active layer further includes a conductive agent and a binder.

[0012] As an optional embodiment, the conductive agent includes a first conductive agent and a second conductive agent, the first conductive agent including carbon nanotubes, and the second conductive agent including Super P and / or acetylene black; and / or, the adhesive includes a first adhesive and a second adhesive, the first adhesive including polyvinylidene fluoride, and the second adhesive including polyacrylate elastic adhesives and / or styrene-butadiene rubber.

[0013] As an optional embodiment, the first conductive agent accounts for 0.5% to 2% of the mass percentage of the positive electrode active layer, and / or the second conductive agent accounts for 1% to 3% of the mass percentage of the positive electrode active layer, and / or the first adhesive accounts for 1% to 3% of the mass percentage of the positive electrode active layer, and / or the second adhesive accounts for 0.5% to 2.5% of the mass percentage of the positive electrode active layer.

[0014] A second aspect of this application also provides a method for preparing a positive electrode sheet, comprising: A positive electrode slurry is prepared; the positive electrode slurry includes a positive electrode active material, the positive electrode active material includes single crystal particles and / or single crystal-like secondary particles, and the positive electrode active material satisfies at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to the intensity of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°. The texture factor of the (003) crystal plane of the positive electrode active material is C, where C>1.5; The positive electrode slurry is coated onto the positive electrode current collector; Before the positive electrode slurry is dried and cured, an external magnetic field is applied at a preset angle to the plane of the positive electrode current collector, so that the angle between the (003) crystal plane of the single crystal particle and / or the multiple primary crystals of the quasi-single crystal secondary particle and the plane of the positive electrode current collector is 15°~75°. The oriented positive electrode slurry is dried and rolled to obtain the positive electrode sheet.

[0015] As an optional embodiment, the method for preparing the positive electrode active material also includes: A spherical transition metal hydroxide precursor was prepared by reacting a mixed salt solution of nickel, cobalt, and manganese with a precipitant and ammonia. The precursor is mixed with a lithium source; The mixed materials are then sintered in the first stage. The product after the first stage of sintering is subjected to a second stage of heat treatment to obtain the positive electrode active material.

[0016] A third aspect of this application also provides a battery, including the aforementioned positive electrode sheet, or a positive electrode sheet prepared by the aforementioned preparation method.

[0017] The technical solution provided in this application may include the following beneficial results: This application selects (003)-dominant single-crystal particles and / or quasi-single-crystal secondary particles as positive electrode active materials, making it very direct and efficient to control the crystal orientation by controlling the magnetic field. Furthermore, the angle between the (003) crystal planes of multiple primary grains of the single-crystal particles and / or quasi-single-crystal secondary particles and the positive electrode current collector plane is controlled within 15°~75°. When the stress from the expansion of the silicon-carbon negative electrode (mainly manifested as tensile / compressive stress within the electrode sheet) acts on this particle, this orientation helps to transform the harmful stress that would cause particle breakage into relatively harmless slip along the (003) crystal plane direction. This allows for the safe dissipation of mechanical energy through controllable micro-deformation, preventing internal grain boundary cracking (for polycrystalline particles) or overall breakage. This fundamentally solves the mechanical failure problem of positive electrode active materials in silicon-carbon systems, thereby significantly improving the cycle life of the battery. The angle of not less than 15° ensures that the stress has a sufficient component to drive the crystal plane slip, avoiding insufficient slip driving force due to an angle that is too small; while the angle of not more than 75° prevents the particles from becoming unstable or peeling off directly under stress due to an angle that is too large.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0019] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0020] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] In related technologies, to address the volume change problem of silicon-based anodes, the main technical approaches include nano-sizing of silicon materials to reduce absolute strain, designing porous or hollow structures to reserve expansion space, developing novel elastic binders to buffer volume changes, and constructing robust carbon composite frameworks to limit the expansion of silicon particles. These strategies aim to alleviate the pulverization of anode materials, maintain the integrity of electrical contacts, and stabilize the solid electrolyte interface film, thereby improving the cycle performance of silicon-based anodes to some extent. However, most of these studies focus on the modification and strengthening of the anode itself, relatively neglecting the indirect mechanical effects of the drastic volume changes of silicon-carbon anodes on other battery components, especially the cathode. During cycling, the periodic large-scale expansion and contraction of the anode are transmitted to the cathode through the electrolyte and separator, producing a continuous "tug-of-war effect" on the cathode. This causes a sharp increase in battery internal resistance, rapid capacity decay, and ultimately premature termination of battery cycle life. Therefore, focusing solely on improving the anode itself is insufficient to solve the failure problem caused by mechanical interactions in the entire battery system; a systemic re-examination and new solutions are needed.

[0023] To address the aforementioned issues, this application provides a positive electrode sheet and its preparation method, wherein the positive electrode can effectively resist the mechanical stress transmitted by the volume change of the negative electrode, suppress particle breakage and electrode sheet fracture, thereby significantly improving the cycle life of the battery.

[0024] This application provides a positive electrode sheet, including a positive current collector and a positive active layer coated on at least one side of the positive current collector. The positive active layer includes a positive active material, which includes single-crystal particles and / or quasi-single-crystal secondary particles. The (003) crystal planes of the multiple primary grains of the single-crystal particles and / or quasi-single-crystal secondary particles form an angle of 15° to 75° with the plane of the positive current collector, and the positive active material satisfies at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to that of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°; The texture coefficient of the (003) crystal plane of the positive electrode active material is C, where C>1.5.

[0025] In this embodiment, the quasi-single-crystal secondary particle can refer to a large particle composed of countless primary grains (i.e., single-crystal particles) tightly packed along a specific direction (e.g., its c-axis direction), which has a common dominant crystallographic orientation inside, making it exhibit physical properties similar to a single crystal on a macroscopic scale. This design is the basis for achieving controllable orientation of the entire particle.

[0026] The (003) crystal plane of multiple primary grains of single crystal particles and / or quasi-single crystal secondary particles refers to the channel plane of lithium ion layered intercalation and deintercalation.

[0027] In the embodiments of this application, the positive electrode active material satisfies at least one of conditions ①②③: ① The ratio of the intensity of the diffraction peaks of the (003) crystal plane to that of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A ≥ 1.5. For example, under the test conditions of using a Cu-Kα ray source and a scanning speed of 2° / min, the ratio of the intensity of the diffraction peak of the (003) crystal plane to that of the diffraction peak of the (104) crystal plane in the XRD pattern of the positive electrode active material powder or the electrode sheet composed thereof is A, where A ≥ 1.5. For layered oxides, I(003) / I(104) is a classic indicator for measuring cation mixing and preferred orientation of crystal planes. Usually, this ratio is about 1.0~1.3 for randomly oriented NCM materials. A value significantly greater than 1.5 indicates that there is a significant preferred orientation in the normal direction of the (003) plane.

[0028] ② The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°. For example, under test conditions using a Cu-Kα ray source and a scanning speed of 2° / min, the FWHM of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material powder or its constituent electrode sheet is B, where B ≤ 0.15°. The FWHM reflects grain size and crystal integrity. For "quasi-single-crystal" particles with a clearly preferred orientation, the diffraction peaks of their dominant crystal plane are very sharp. This parameter distinguishes them from ordinary polycrystalline materials composed of many randomly oriented small grains.

[0029] ③ The texture coefficient of the (003) crystal plane of the positive electrode active material is C, where C>1.5. For example, by analyzing or calculating the texture coefficient (TC) using a pole figure, the texture coefficient of the (003) crystal plane of the positive electrode active material is C, where C>1.5. This indicates that the positive electrode active material exhibits a clear preferred orientation in the direction of the (003) crystal plane normal, while the texture coefficient is 1 in random orientation.

[0030] When the positive electrode active material satisfies at least one of conditions ①②③, it indicates that the (003) crystal plane of the positive electrode active material is dominant, that is, the large surface area of ​​the plate-like particles is the (003) plane. When the particles are aligned in the slurry under the action of a magnetic field, their macroscopic plane directly represents their microscopic (003) crystal plane. This makes it very direct and efficient to control the crystal plane orientation by controlling the magnetic field. The magnetic field forces the (003) crystal plane to be parallel to the direction of the magnetic field, realizing the basic unity of macroscopic morphology and microscopic crystal orientation.

[0031] Plate-like particles with consistent (003) plane orientation are more likely to undergo crystal plane slip in a coordinated manner when subjected to in-plane stress, thereby releasing stress more effectively. If the particle morphology is irregular, even if the crystal orientation is controlled, the complex geometry of its outer surface may lead to local stress concentration.

[0032] In the embodiments of this application, the positive electrode active material can be selected from unmagnetized or magnetically doped single-crystal high-nickel ternary materials (such as LiNi). 0.8 Co 0.1 Mn 0.1 O2 (NCM811) or high-voltage lithium cobalt oxide (LiCoO2). Under an applied magnetic field, the particles can have the angle between the (003) crystal plane and the electrode plane mainly distributed between about 15° and 75°.

[0033] For example, the preparation method includes: after the slurry is coated, a static magnetic field with an intensity of 1.0T and an angle of 15° to 75° with the electrode plane is applied during the initial drying stage. Due to the magnetic anisotropy of the material (the easy magnetization axis is located in the (003) plane), the particles will rotate under the action of the magnetic field, making their easy magnetization axis parallel to the direction of the magnetic field. This will inevitably cause their c-axis (i.e., the normal of the (003) crystal plane) to be perpendicular to the direction of the magnetic field. By controlling the angle between the magnetic field and the electrode, the c-axis of the particles and the angle of the (003) crystal plane relative to the electrode can be precisely controlled. After the magnetic field stops, the particle orientation is locked by drying and solidification, and finally the angle between the (003) crystal plane of most particles and the electrode plane is precisely controlled within, for example, the range of 15° to 75°.

[0034] In this embodiment, the (003) crystal plane of multiple primary crystal grains of single crystal particles and / or quasi-single crystal secondary particles is set at an angle of 15° to 75° with the positive electrode current collector plane, thereby achieving efficient, precise, and repeatable macroscopic control of the crystal plane orientation of the particles. The oriented electrode has the best stress release resistance.

[0035] Therefore, by selecting single-crystal particles and / or quasi-single-crystal secondary particles with (003) crystal plane dominance as positive electrode active materials, the control of crystal plane orientation by controlling the magnetic field becomes very direct and efficient. Furthermore, by controlling the angle between the (003) crystal plane of multiple primary grains of the single-crystal particles and / or quasi-single-crystal secondary particles and the positive electrode current collector plane within 15°~75°, when the stress from the expansion of the silicon-carbon negative electrode (mainly manifested as tensile / compressive stress within the electrode sheet) acts on this particle, this orientation helps to transform the harmful stress that would cause particle breakage into relatively harmless slip along the (003) crystal plane direction. This allows for the safe dissipation of mechanical energy through controllable micro-deformation, preventing internal grain boundary cracking (for polycrystalline particles) or overall breakage of the particles. This fundamentally solves the mechanical failure problem of positive electrode active materials in the silicon-carbon system, thereby significantly improving the cycle life of the battery. The angle of not less than 15° ensures that the stress has a sufficient component to drive the crystal plane slip, avoiding insufficient slip driving force due to an angle that is too small; while the angle of not more than 75° prevents the particles from becoming unstable or peeling off directly under stress due to an angle that is too large.

[0036] As an optional embodiment, the general formula for single-crystal particles and / or single-crystal-like secondary particles is LiM. （1-x） A x O2, wherein M comprises one or more of Ni, Co, and Mn; A is at least one magnetic dopant selected from Fe, Cr, Al, Mg, Zr, Ti, Y, W, Mo, Nb, Ta, and rare earth elements; 0 ≤ x ≤ 0.08 When X=0, there is no magnetic dopant element; when X>0, there is magnetic dopant element.

[0037] When X=0, the general formula for single-crystal particles and / or single-crystal-like secondary particles is LiMO2, where M includes one or more of Ni, Co, and Mn. The single-crystal particles and / or single-crystal-like secondary particles can be selected from at least one of high-nickel layered oxide materials, high-voltage lithium cobalt oxide, high-voltage / high-capacity manganese-based lithium-rich manganese materials, and lithium nickel manganese oxide spinel materials.

[0038] When X > 0, the general formula for single-crystal particles and / or single-crystal-like secondary particles is LiM. （1-x） A xO2, wherein M comprises one or more of Ni, Co, and Mn; A is at least one magnetic dopant selected from Fe, Cr, Al, Mg, Zr, Ti, Y, W, Mo, Nb, Ta, and rare earth elements, 0 < x ≤ 0.08; rare earth elements may include rare earth elements other than La (such as Nd, Ce, Pr, Sm, etc.). This application further describes the magnetic design of the positive electrode active material particles. Since conventional layered oxide materials (NCM, NCA, LCO) are mostly diamagnetic or weakly paramagnetic, the torque generated in a magnetic field is extremely small, making it difficult to achieve effective, batch-oriented alignment in viscous slurries. By doping with magnetic elements, the responsiveness of the particles to external magnetic fields can be significantly enhanced, providing a material basis for achieving high-precision, high-efficiency magnetic field-oriented alignment.

[0039] This application specifically sets a general formula for the crystal structure of magnetic doped materials. Here, A represents the dopant element itself, which possesses unpaired electrons, thereby introducing ferromagnetism or strong paramagnetism. For example, when A is Fe... 3+ (High spin, 5 unpaired d electrons), Co 2+ Or certain rare earth ions (such as Nd) 3+ When the doping amount x ≤ 0.02, ensuring that the doping is trace, sufficient magnetism can be imparted to the host material without significantly changing its electrochemical properties (such as specific capacity and operating voltage).

[0040] For example, the positive electrode active material is a magnetically doped, single-crystal-like secondary particle. Specifically, it can be: Material 1: High-nickel NCM doped with 1 mol% Fe (such as Li(Ni) 0.83 Co 0.12 Mn 0.05 ) 0.99 Fe 0.01 O2).

[0041] Material 2: High-voltage lithium cobalt oxide doped with 0.5 mol% Nd (neodymium).

[0042] As a preferred embodiment, the percentage of atoms doped with magnetic elements at all transition metal sites is 0.1 mol% to 2 mol%.

[0043] In the embodiments of this application, all transition metal sites are pointers to LiM. （1-x） A x All elements occupying transition metal sites in O2 (i.e., the sum of M and A).

[0044] This application further specifies the concentration range of the doped magnetic element atoms. A concentration of at least 0.1 mol% ensures a sufficient number of introduced magnetic centers to generate a collective effect, enabling the entire particle to obtain an effective magnetic torque sufficient to overcome the viscous resistance of the slurry under a magnetic field, thus achieving orientation. A concentration of at least 2 mol% avoids excessive doping that could lead to excessive main lattice distortion, resulting in material structural instability, decreased electronic / ionic conductivity, or the introduction of electrochemically active impurities.

[0045] In the embodiments of this application, the percentage of atoms of the doped magnetic element in all transition metal sites can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0% or any value within the above-defined range, and this application does not limit it in this regard.

[0046] As an optional embodiment, the particle size of the single crystal particles and / or quasi-single crystal secondary particles is 8μm to 20μm.

[0047] In the embodiments of this application, the particle size of single-crystal particles and / or quasi-single-crystal secondary particles can refer to D50, where D50 is the median particle size or the median of the cumulative distribution. It represents the particle size value corresponding to when the cumulative volume (or mass) in a powder sample reaches 50% of the total sample.

[0048] In this embodiment, the particle size of the single-crystal particles and / or quasi-single-crystal secondary particles is not less than 8 μm. This ensures that the particles have sufficient mass to generate an effective rotational torque in a magnetic field or flow field, and also helps to reduce the specific surface area and minimize side reactions. The particle size of the single-crystal particles and / or quasi-single-crystal secondary particles is not greater than 20 μm. This prevents excessively large particle sizes from causing excessively long lithium-ion solid-phase diffusion paths, which would affect rate performance. It also prevents excessively large particles from being more easily peeled off from the current collector under electrode bending or stress.

[0049] In this application embodiment, the particle size range of single crystal particles and / or quasi-single crystal secondary particles is set to 8μm~20μm, which can meet the high energy density requirements while ensuring good kinetic and structural stability.

[0050] In the embodiments of this application, the particle size range of single crystal particles and / or quasi-single crystal secondary particles can be 8μm, 10μm, 15μm, 20μm or any value within the above-defined range, and this application does not limit it in this regard.

[0051] As an optional embodiment, the positive electrode active layer also includes a conductive agent and a binder.

[0052] In a preferred embodiment, the conductive agent includes a first conductive agent and a second conductive agent, wherein the first conductive agent includes carbon nanotubes and the second conductive agent includes Super P and / or acetylene black.

[0053] This application employs a composite conductive agent, wherein the first conductive agent (carbon nanotubes) serves as a "high aspect ratio conductive agent," and its fibrous structure can build long-range, robust conductive bridges between active particles. More importantly, the high strength and toughness of carbon nanotubes enable them to function similarly to fibers in fiber-reinforced composite materials, bridging microcracks and inhibiting crack initiation and propagation.

[0054] The second conductive agent (Super P / acetylene black), as an elastic spherical conductive agent, provides numerous point contacts through its nano-spherical particles, filling the voids. Under localized stress, these soft carbon black particles can undergo elastic deformation, acting as microscopic buffers and synergistically constructing a stable and elastic three-dimensional conductive network with carbon nanotubes.

[0055] In a preferred embodiment, the adhesive includes a first adhesive and a second adhesive, the first adhesive including polyvinylidene fluoride and the second adhesive including a polyacrylate elastic adhesive and / or styrene-butadiene rubber.

[0056] The embodiments of this application employ a composite adhesive. The first adhesive (PVDF) provides basic, strong bonding strength and excellent adhesion to the aluminum current collector, ensuring the basic integrity of the electrode coating.

[0057] The second binder (polyacrylate elastic binder / styrene-butadiene rubber) is an elastic component whose molecular chains can form a physical entanglement or interpenetrating network structure with PVDF. Under cyclic stress, this elastic component can undergo large deformation, effectively absorbing and dissipating strain energy, and preventing stress concentration from causing adhesive failure or coating cracking.

[0058] In a preferred embodiment, the first conductive agent accounts for 0.5% to 2% of the mass percentage of the positive electrode active layer.

[0059] In this embodiment, the first conductive agent (carbon nanotubes) accounts for 0.5% to 2% of the mass percentage of the positive electrode active layer, which can ensure the formation of an effective long-range conductive network and a reinforcing network; at the same time, it can prevent the slurry from becoming difficult to disperse, the viscosity from surging, or the proportion of active material from decreasing due to excessive amount.

[0060] In the embodiments of this application, the mass percentage of the first conductive agent in the positive electrode active layer can be 0.5%, 1%, 2% or any value within the above-defined range, and this application does not limit it in this regard.

[0061] In a preferred embodiment, the second conductive agent accounts for 1% to 3% of the mass percentage of the positive electrode active layer. In this embodiment, the second conductive agent (spherical carbon black) accounts for 1% to 3% of the mass percentage of the positive electrode active layer, which can ensure sufficient point contact and pore filling; at the same time, it avoids overfilling from affecting ion transport or reducing the effective concentration of the binder.

[0062] In the embodiments of this application, the mass percentage of the second conductive agent in the positive electrode active layer can be 1%, 2%, 3%, or any value within the above-defined range, and this application does not limit it in this regard.

[0063] In a preferred embodiment, the first adhesive accounts for 1% to 3% of the mass percentage of the positive electrode active layer. In this embodiment, the first binder (PVDF) accounts for 1% to 3% of the mass percentage of the positive electrode active layer, which can provide the necessary matrix strength; at the same time, it controls the cost and prevents the excessively thick insulating layer from affecting conductivity.

[0064] In the embodiments of this application, the mass percentage of the first adhesive in the positive electrode active layer can be 1%, 2%, 3% or any value within the above-defined range, and this application does not limit it in this regard.

[0065] In a preferred embodiment, the second adhesive accounts for 0.5% to 2.5% of the mass percentage of the positive electrode active layer.

[0066] In this embodiment, the second binder (elastomer) accounts for 0.5% to 2.5% of the mass percentage of the positive electrode active layer, which can ensure the formation of an effective energy dissipation phase; at the same time, it prevents excessive amount from causing the overall modulus of the electrode to be too low or compatibility issues with PVDF.

[0067] In the embodiments of this application, the mass percentage of the second adhesive in the positive electrode active layer can be 0.5%, 1%, 2% or any value within the above-defined range, and this application does not limit it in this regard.

[0068] Corresponding to the aforementioned application function implementation method embodiments, this application also provides a method for preparing a positive electrode sheet and corresponding embodiments.

[0069] This application also provides a method for preparing a positive electrode sheet, comprising: S10. Prepare a positive electrode slurry, the positive electrode slurry comprising a positive electrode active material, the positive electrode active material comprising single crystal particles and / or single crystal-like secondary particles, and the positive electrode active material satisfying at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to that of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°; The texture coefficient of the (003) crystal plane of the positive electrode active material is C, where C>1.5.

[0070] S20. Coat the positive electrode slurry onto the positive electrode current collector.

[0071] S30. Before the positive electrode slurry is dried and cured, an external magnetic field is applied at a preset angle to the plane of the positive electrode current collector, so that the angle between the (003) crystal plane of multiple primary crystals of single crystal particles and / or quasi-single crystal secondary particles and the plane of the positive electrode current collector is 15°~75°.

[0072] S40. The oriented positive electrode slurry is dried and rolled to obtain a positive electrode sheet.

[0073] In this embodiment, an external magnetic field is applied after the slurry is coated but before it dries and cures. The direction of the external magnetic field is set at a preset angle to the plane of the positive electrode current collector, so as to cause the single crystal particles and / or quasi-single crystal secondary particles in the slurry to rotate and orient, thereby controlling the angle between the (003) crystal plane of the multiple primary grains constituting the particles and the plane of the positive electrode current collector to be within the range of 15° to 75°. The critical time window for applying the magnetic field is after coating but before drying and curing. At this time, the slurry still maintains fluidity, and the particles can rotate freely under the action of magnetic torque; at the same time, the solvent has not completely evaporated, and the slurry system has sufficient deformability to respond to the rotation of the particles.

[0074] This application transforms the inherent magnetic properties of materials into a macroscopic structural advantage (specific crystal orientation) of the electrode through a controllable external field process. By controlling the magnetic field strength, direction, and slurry rheological state, positive electrode sheets with specific stress-resistant orientations can be stably and repeatedly mass-produced, solving the performance dispersion problem caused by random orientation. The magnetic field application device can be integrated into existing coating-drying equipment without completely changing the production line, and the process window is clearly defined (viscosity, magnetic field strength, timing), showing good prospects for large-scale production. This method does not passively enhance electrode strength but actively designs the particle arrangement, giving it an inherent ability to dissipate stress through crystal plane slip, thereby improving the durability of the electrode in the silicon-carbon system from the source.

[0075] As an optional embodiment, the strength of the magnetic field is 0.5T~2T.

[0076] In this embodiment, the magnetic field strength is set to 0.5T~2T: A magnetic field strength of not less than 0.5T provides sufficient magnetic torque to overcome the viscous resistance of the slurry and drive the particles to rotate; a magnetic field strength of not more than 2T ensures the orientation effect while taking into account both equipment cost and process safety.

[0077] As an optional embodiment, in step S1, the viscosity of the slurry is in the range of 3000 mPa·s to 8000 mPa·s.

[0078] Setting the slurry viscosity to be no less than 3000 mPa·s ensures that the slurry has sufficient structural viscosity to "fix" the particles in the subsequent magnetic field orientation step. This prevents the particles from randomly flipping again after orientation due to Brownian motion or gravity caused by an excessively thin slurry, thus maintaining orientation stability. At the same time, a suitable viscosity also helps to obtain a uniform coating.

[0079] Setting the viscosity of the slurry to no more than 8000 mPa·s can prevent the slurry viscosity from being too high, which would cause excessive viscous resistance to the particles when they rotate in the magnetic field, making it difficult to achieve effective orientation within the given magnetic field strength and process time, and even affecting the uniformity of the coating.

[0080] As an optional embodiment, the preparation method of the positive electrode active material includes: S11. A mixed salt solution of nickel, cobalt, and manganese is reacted with a precipitant and ammonia to prepare a spherical transition metal hydroxide precursor.

[0081] The embodiments of this application employ a co-precipitation method to synthesize the precursor, which can prepare spherical transition metal hydroxides (Ni) with uniform chemical composition and concentrated particle size distribution. 0.8 Co 0.1 Mn 0.1 (OH)2 precursor.

[0082] In this embodiment, the salt solution can be prepared as a mixed aqueous solution of nickel, cobalt, and manganese sulfates or nitrates in a target ratio (e.g., 8:1:1), with a concentration of 1.5 mol / L to 2.5 mol / L. The precipitant can be a sodium hydroxide (NaOH) solution of a certain concentration. The complexing agent can be an ammonia solution of a certain concentration. Ammonia can form complexes with metal ions, controlling the precipitation rate and ensuring uniform composition.

[0083] The coprecipitation reaction can be carried out in a continuously stirred reactor (CSTR). The conditions for the coprecipitation reaction are: temperature 50℃~60℃, pH 10.5~11.5 (which can be controlled by automatically adding NaOH and ammonia), and stirring speed 300rpm~500rpm to ensure thorough mixing and mass transfer. The reaction time can be several tens of hours to obtain the desired D50 (e.g., ~10μm) particles.

[0084] For example, a salt solution, an alkaline solution, and ammonia water are simultaneously and continuously pumped into a reactor. Under constant temperature and pH, the metal hydroxide slowly and uniformly precipitates out, growing into spherical secondary particles. The resulting slurry is filtered and washed to remove residual sodium and sulfate ions. It is then dried at 100°C to 120°C for 10 to 15 hours to obtain the precursor powder.

[0085] S21. Mix the precursor with a lithium source.

[0086] In the embodiments of this application, the lithium source can be either lithium hydroxide or lithium carbonate. For high-nickel materials, LiOH is more commonly used.

[0087] The molar ratio of lithium to transition metals can be slightly higher than the stoichiometric ratio, for example, 1.02 to 1.08, to compensate for lithium volatilization at high temperatures. Furthermore, high-speed dry mixing or wet ball milling can ensure thorough and uniform mixing of the lithium source and precursor.

[0088] S31. The mixed materials are sintered in the first stage.

[0089] The first stage of sintering allows the precursor to react with the lithium source to generate layered oxides and controls their grain growth morphology, making the (003) face dominant.

[0090] The conditions for the first stage of sintering can be as follows: The temperature should be between 750℃ and 850℃. If the temperature is too low, the reaction will be incomplete; if the temperature is too high, it will lead to excessive lithium volatilization and excessive grain growth.

[0091] A pure oxygen atmosphere helps to convert Ni 2+ Oxidized to Ni 3+ This reduces cation mixing and forms an ideal layered structure.

[0092] The reaction time is 10-20 hours. A longer holding time is beneficial for the full growth and fusion of grains, forming dense, near-single-crystal large particles.

[0093] The heating / cooling rate can be 2℃ / min to 5℃ / min to avoid particle cracking caused by thermal stress.

[0094] S41. The product after the first stage of sintering is subjected to a second stage of heat treatment to obtain the positive electrode active material.

[0095] The second stage of heat treatment can be used for morphology control and stress relief.

[0096] The conditions for the second-stage heat treatment can be as follows: The temperature can be slightly lower than that of the first stage sintering, for example, 600℃~750℃.

[0097] React for 5 to 15 hours in an oxygen or air atmosphere.

[0098] At slightly lower temperatures, atoms have sufficient mobility for surface diffusion and rearrangement without triggering drastic bulk growth. During this stage, non-(003) surfaces with higher surface energy (such as (101) surfaces) gradually "dissolve" or "transform" into more stable (003) surfaces through atomic rearrangement. This process, known as surface reconstruction or thermal etching, effectively increases the exposed area of ​​the (003) surfaces, making them dominant in the grain morphology.

[0099] The embodiments of this application may also include subsequent processing steps.

[0100] Wash the sintered material with deionized water or weak acid to remove residual lithium salts (such as Li2CO3, LiOH) from the surface.

[0101] Annealing at 400℃~500℃ for a short time (e.g., 3~5 hours) is performed to repair surface structural damage that may be caused during the washing process and to ensure the stability of the material surface.

[0102] Corresponding to the aforementioned application function implementation method embodiments, this application also provides a battery and corresponding embodiments.

[0103] This application does not impose any particular limitation on the specific type of battery; it can be a secondary battery, a power battery, an energy storage battery, etc. The battery casing can be used to encapsulate the battery cell and electrolyte. The battery casing can be a hard casing, such as a hard plastic casing, an aluminum casing, or a steel casing. It can also be a pouch battery, such as a pouch-type pouch. The material of the pouch can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate. This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape.

[0104] The battery cell in this application embodiment can be formed by winding a positive electrode sheet, a negative electrode sheet, and a separator. Specifically, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, the stacked electrode sheets and the separator are wound together to obtain the battery cell.

[0105] The electrolyte in this embodiment includes an organic solvent, a lithium salt, and a first additive. The first additive includes a compound having an unsaturated hydrocarbon group. Using a compound having an unsaturated hydrocarbon group as the first additive can coordinate with lithium ions, promote the dissociation of lithium salt, and enhance the conduction of lithium ions in the polymer electrolyte.

[0106] In one specific embodiment, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, which include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0107] In this embodiment, the positive electrode sheet includes a positive current collector and a positive active material coated on at least one side of the positive current collector.

[0108] This application does not limit the selection of the positive electrode current collector; it can be selected according to actual needs, such as copper foil. In embodiments of this application, the positive electrode active material layer can be coated on at least one side of the positive electrode current collector.

[0109] In this embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material coated on at least one side of the negative electrode current collector.

[0110] This application does not limit the selection of the negative electrode current collector; it can be selected according to actual needs, such as copper foil. The negative electrode active material layer of this application includes a negative electrode active material and a negative electrode binder. The negative electrode active material includes carbon materials and silicon materials. This application does not limit the selection of carbon materials; it can be selected according to actual needs, such as graphite, carbon black, hard carbon, soft carbon, etc. This application does not limit the selection of silicon materials; it can be selected according to actual needs, such as silicon oxide, pre-lithiated silicon oxide, pre-magnesiated silicon oxide materials, silicon-carbon composite materials, elemental silicon, etc. The negative electrode binder of this application includes polypropylene compounds and styrene-butadiene rubber. Polypropylene compounds refer to polypropylene derivatives, such as polyacrylic acid, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, etc.

[0111] The liquid electrolyte in this application embodiment includes an electrolyte salt, an organic solvent, and additives. In this application embodiment, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiODFB), lithium bis(oxalate borate) (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorophosphate (LiPOF2), and the concentration of the electrolyte salt can be from 0.4 mol / L to 2.2 mol / L.

[0112] In the embodiments of this application, the organic solvent includes at least one selected from ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, ethyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0113] In the embodiments of this application, the electrolyte additive also includes other additives, including but not limited to several of the following: vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), succinate (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), propenesulfonate lactone (PST), methylene disulfonate (MMDS), ethylene glycol bis(propionitrile) ether (EGBE), pentafluoroethoxyphosphazene, dicyclohexylcarbonyl, trimethyl imide phosphate, and hexamethylene diisocyanate.

[0114] Corresponding to the aforementioned application function implementation method embodiments, this application also provides an electronic device and corresponding embodiments.

[0115] This application also provides an electronic device, including the aforementioned battery.

[0116] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0117] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0118] Example 1: 1. Preparation of positive electrode sheet S10. Prepare the positive electrode slurry, which includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes a single-crystal LiNi0.8Co0.1Mn0.1O2 material with a D50 of 12μm. Through co-precipitation precursor sintering and subsequent heat treatment processes, the (003) crystal plane is made dominant in the particles (i.e., satisfying at least one of conditions ①②③). Super P is selected as the conductive agent, and Super P accounts for 3% of the mass percentage of the positive electrode slurry. PVDF is selected as the binder, and PVDF accounts for 3% of the mass percentage of the positive electrode slurry.

[0119] S20. Coat the positive electrode slurry onto the positive electrode current collector.

[0120] S30. Before the positive electrode slurry is dried and cured, an external magnetic field at 45° to the plane of the positive electrode current collector is applied so that the (003) crystal plane of multiple primary crystals of single crystal particles and / or quasi-single crystal secondary particles is at an angle of 45° to the plane of the positive electrode current collector.

[0121] S40. The oriented positive electrode slurry is dried and rolled to obtain a positive electrode sheet.

[0122] 2. Preparation of negative electrode sheet The negative electrode active material graphite, silicon particles, conductive agent acetylene black (Super P), thickener CMC and binder SBR are mixed evenly in a mass ratio of 84:10:2:1.2:2.8 and evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of the copper foil current collector, and then baked, rolled, and cut to obtain the negative electrode sheet.

[0123] 3. Preparation of electrolyte Commercially available electrolyte.

[0124] 4. Manufacturing of lithium-ion batteries The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets. After winding and welding the tabs, a bare cell is obtained. The bare cell is then placed in an aluminum-plastic film for electrolyte injection and encapsulation to obtain a lithium-ion battery. Based on the formulations and preparation methods in Table 1, the lithium-ion batteries of each embodiment and comparative example are prepared. In Table 1, "content of magnetic elements" refers to the percentage of atoms of doped magnetic elements among all transition metal sites.

[0125] Table 1. Formulation and Preparation Method

[0126] Note: (003) Crystal plane dominance means that the positive electrode active material meets at least one of conditions ①②③, (003) Crystal plane non-dominance means that the positive electrode active material does not meet any of conditions ①②③.

[0127] II. Performance Testing The performance of each embodiment and comparative example was tested as follows, and the test results are shown in Table 2.

[0128] (1) Cyclic performance At 25°C±2°C, charge at a constant current of 1C to 4.25V, then switch to constant voltage until the current ≤0.05C; let stand for 5 minutes; discharge at a constant current of 1C to 3.0V, cycle 500 times. Record the discharge capacity of the Nth cycle and calculate its retention rate relative to the discharge capacity of the 5th cycle.

[0129] (2) Observe the positive electrode after disassembly 1. Battery disassembly and electrode acquisition: The battery that has completed 500 cycles of performance testing was moved into a glove box filled with argon gas (H2O & O2 < 0.1 ppm) in a discharged state (3.0V).

[0130] Depending on the battery type (pouch / hard case), carefully disassemble the casing using specialized tools to remove the battery cells.

[0131] Immerse the battery cell in sufficient anhydrous dimethyl ether (DME) or dimethyl carbonate (DMC) solvent for 24 hours to fully dissolve and wash away residual electrolyte.

[0132] Separate the positive electrode, separator, and negative electrode inside the glove box. Gently rinse the surface of the positive electrode with DME solvent, and then place it in the vacuum transition chamber inside the glove box.

[0133] 2. Macroscopic morphological observation and sampling: Remove the dried positive electrode from the glove box.

[0134] In a drying room (relative humidity <5%), observe the overall condition of the electrode sheets with the naked eye or with the aid of an optical microscope (50-100x), paying particular attention to: a. Integrity of the active layer: Are there any visible cracks, wrinkles, bulges, or peeling?

[0135] b. Color uniformity: Whether the surface color is uniform, and whether there is any darkening or mottled due to local side reactions or metal dissolution.

[0136] c. Current collector condition: Whether the aluminum foil has corroded, discolored, or broken.

[0137] 3. Microscopic morphology and structural analysis (SEM): Samples approximately 1cm × 1cm in size were cut from both the central and edge regions of each electrode for subsequent microscopic analysis. The positive electrode samples were fixed to the sample stage using conductive adhesive. Observation was performed using a scanning electron microscope (SEM, such as a Hitachi SU8000) in low-vacuum mode. Key focus areas: Ⅰ. Low magnification (500-2000 times): Observe the overall morphology of the active material layer, the uniformity of particle distribution, the bonding between the coating and the current collector, and whether there is a microscopic origin of macroscopic cracks.

[0138] II. High magnification (5000-20000x): Focusing on one or several secondary particles / single crystal particles for detailed observation: a. Particle integrity: Whether the particle surface is smooth, and whether there are cracks (especially through cracks), breakage or pulverization.

[0139] b. Particle state: Whether the network formed by the conductive agent and binder is intact, and whether there is obvious separation or aggregation between particles.

[0140] c. Surface coating: Observe the coverage of the positive electrode electrolyte interface film (CEI film) (whether it is uniform, too thick or locally piled up).

[0141] d. Cross-sectional observation: Partial positive electrode samples were prepared by liquid nitrogen embrittlement or focused ion beam (FIB) cutting. Observation: (a) Coating thickness uniformity and tightness of bonding with the current collector.

[0142] (b) The direction and depth of the cracks determine whether it is cohesive failure of the coating or interfacial delamination between the coating and the current collector.

[0143] Table 2 Test Results

[0144] By comparing Examples 1 to 5 and Comparative Examples 1 to 3 with Tables 1 and 2, it can be seen that when the positive electrode active material includes single crystal particles and / or quasi-single crystal secondary particles, and the (003) crystal plane of the multiple primary grains of the single crystal particles and / or quasi-single crystal secondary particles is dominant, and the angle between the (003) crystal plane of the multiple primary grains of the single crystal particles and / or quasi-single crystal secondary particles and the positive electrode current collector plane is 15° to 75°, the stress from the expansion of the silicon-carbon negative electrode (mainly manifested as tensile / compressive stress within the electrode sheet) can be applied to this particle. This orientation is beneficial to convert the harmful stress that causes particle breakage into relatively harmless slip along the (003) crystal plane direction, thereby safely dissipating mechanical energy with controllable micro-deformation, preventing internal grain boundary cracking (for polycrystalline particles) or overall breakage of the particles, fundamentally solving the mechanical failure problem of positive electrode active materials in silicon-carbon systems, thereby significantly improving the cycle life of the battery. Further comparisons with Examples 1, 2, and 3 show that even if the angle between the (003) crystal plane and the current collector plane of the positive electrode active material is not between 15° and 75°, its structural stability and electrochemical performance cannot be improved. Further comparisons with Examples 1, 8, 6, and 9, and with Examples 9 and 10 show that even if the (003) crystal plane is not dominant in the positive electrode active material, its structural stability and electrochemical performance cannot be improved.

[0145] Comparing Examples 1 and 6 reveals that single-crystal particles and / or quasi-single-crystal secondary particles may or may not be doped with magnetic elements, preferably with magnetic elements. This significantly enhances the particles' response to external magnetic fields, providing a material basis for achieving high-precision and high-efficiency magnetic field orientation. Further, in Example 11, the concentration of the doped magnetic elements is no greater than 2 mol%, which avoids excessive doping leading to excessive distortion of the main lattice, thus preventing negative impacts such as material structural instability, decreased electronic / ionic conductivity, or the introduction of electrochemically active impurities. Further comparison of Comparative Examples 4 and 5 shows that even if the angle between the (003) crystal plane and the positive electrode current collector plane is not between 15° and 75°, the structural stability and electrochemical performance of the positive electrode active material cannot be improved.

[0146] Comparing Examples 1, 7 to 9, it is evident that by employing composite conductive agents and composite binders, a stable and elastic three-dimensional conductive network can be constructed. Furthermore, under cyclic stress, this network effectively absorbs and dissipates strain energy, preventing stress concentration that could lead to bonding failure or coating cracking. Further comparison of Comparative Examples 6 and 7 reveals that even if the angle between the (003) crystal plane and the positive electrode current collector plane of the positive electrode active material is not between 15° and 75°, its structural stability and electrochemical performance cannot be improved.

[0147] By comparing Examples 1, 13 to 16, it can be seen that setting the particle size range of single crystal particles and / or quasi-single crystal secondary particles to 8μm~20μm can not only meet the high energy density requirements, but also ensure good kinetic and structural stability.

[0148] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.

[0149] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.

[0150] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A positive electrode plate, characterized in that, The device includes a positive current collector and a positive active layer coated on at least one side of the positive current collector. The positive active layer includes a positive active material, which includes single-crystal particles and / or single-crystal-like secondary particles. The (003) crystal planes of multiple primary grains of the single-crystal particles and / or the single-crystal-like secondary particles form an angle of 15° to 75° with the plane of the positive current collector. The general formula of the single-crystal particles and / or single-crystal-like secondary particles is LiM. （1-x） A x O2, wherein M comprises one or more of Ni, Co, and Mn; A is at least one magnetic doping element selected from Fe, Cr, Al, Mg, Zr, Ti, W, Mo, Nb, Ta, and rare earth elements; 0 ≤ x ≤ 0.08; and the positive electrode active material satisfies at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to the intensity of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°. The texture coefficient of the (003) crystal plane in the X-ray diffraction pattern of the positive electrode active material is C, where C>1.

5.

2. The positive electrode sheet according to claim 1, characterized in that, The percentage of the atoms of the doped magnetic element in all transition metal sites is 0.1 mol% to 2 mol%.

3. The positive electrode sheet according to claim 1, characterized in that, The particle size of the single crystal particles and / or quasi-single crystal secondary particles is 8μm~20μm.

4. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active layer also includes a conductive agent and a binder.

5. The positive electrode sheet according to claim 4, characterized in that, The conductive agent includes a first conductive agent and a second conductive agent, the first conductive agent including carbon nanotubes, and the second conductive agent including Super P and / or acetylene black; and / or, the adhesive includes a first adhesive and a second adhesive, the first adhesive including polyvinylidene fluoride, and the second adhesive including polyacrylate elastic adhesive and / or styrene-butadiene rubber.

6. The positive electrode sheet according to claim 5, characterized in that, The first conductive agent accounts for 0.5% to 2% of the mass percentage of the positive electrode active layer, and / or the second conductive agent accounts for 1% to 3% of the mass percentage of the positive electrode active layer, and / or the first adhesive accounts for 1% to 3% of the mass percentage of the positive electrode active layer, and / or the second adhesive accounts for 0.5% to 2.5% of the mass percentage of the positive electrode active layer.

7. A method for preparing a positive electrode sheet, characterized in that, include: Prepare a positive electrode slurry; the positive electrode slurry includes a positive electrode active material, the positive electrode active material includes single crystal particles and / or single crystal-like secondary particles, the general formula of the single crystal particles and / or single crystal-like secondary particles is LiM. （1-x） A x O2, wherein M comprises one or more of Ni, Co, and Mn; A is at least one magnetic doping element selected from Fe, Cr, Al, Mg, Zr, Ti, W, Mo, Nb, Ta, and rare earth elements; 0 ≤ x ≤ 0.08; and the positive electrode active material satisfies at least one of the following conditions: The ratio of the intensity of the diffraction peaks of the (003) crystal plane to the intensity of the (104) crystal plane in the X-ray diffraction pattern of the positive electrode active material is A, where A≥1.5; The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak in the X-ray diffraction pattern of the positive electrode active material is B, where B ≤ 0.15°. The texture factor of the (003) crystal plane of the positive electrode active material is C, where C>1.5; The positive electrode slurry is coated onto the positive electrode current collector; Before the positive electrode slurry is dried and cured, an external magnetic field is applied at a preset angle to the plane of the positive electrode current collector, so that the angle between the (003) crystal plane of the single crystal particle and / or the multiple primary crystals of the quasi-single crystal secondary particle and the plane of the positive electrode current collector is 15°~75°. The oriented positive electrode slurry is dried and rolled to obtain the positive electrode sheet.

8. The preparation method according to claim 7, characterized in that, It also includes a method for preparing the positive electrode active material, comprising: A spherical transition metal hydroxide precursor was prepared by reacting a mixed salt solution of nickel, cobalt, and manganese with a precipitant and ammonia. The precursor is mixed with a lithium source; The mixed materials are then sintered in the first stage. The product after the first stage of sintering is subjected to a second stage of heat treatment to obtain the positive electrode active material.

9. A battery, characterized in that, The battery includes a positive electrode sheet as described in any one of claims 1 to 6, or a positive electrode sheet prepared by the preparation method described in claim 7 or 8; the battery also includes a negative electrode sheet.

10. The battery according to claim 9, characterized in that, The negative electrode active material of the negative electrode sheet includes silicon-based materials.

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