Secondary battery, positive electrode active material, and electric device

Abstract

A secondary battery, a positive electrode active material, and an electric device. The secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises secondary particles. The secondary particles are agglomerated particles comprising a plurality of primary particles, wherein the primary particles comprise a positive electrode active substance. The secondary particles comprise oriented secondary particles. In the oriented secondary particles, on the basis of the total number of primary particles in the oriented secondary particles, the ratio of the number of primary particles, the a-axis and the longitudinal direction of which form an included angle α1, is denoted as F1, where 15°≤α1≤45°, and F1≥60%.

Description

Secondary batteries, positive electrode active materials and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. CN2024109275446, filed on July 11, 2024, entitled "Secondary Battery, Positive Electrode Active Material and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and further to a secondary battery, a positive electrode active material, and an electrical device. Background Technology

[0004] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0005] In recent years, with the technological development of rechargeable batteries, lithium-ion batteries, as a representative of rechargeable batteries, have been widely used in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. They are also widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants. Among these, lithium-ion batteries occupy an important position in new energy vehicles. In order to meet the requirements of new energy vehicles in terms of driving range, dynamic performance, and lifespan, it is necessary to comprehensively improve the energy density, dynamic performance, and cycle life of lithium-ion batteries. Summary of the Invention

[0006] In view of the above problems, this application provides a secondary battery, a positive electrode active material, and an electrical device. This secondary battery combines high energy density, good kinetic performance, and long cycle life.

[0007] In a first aspect, this application provides a secondary battery, which includes a positive electrode sheet, the positive electrode sheet including a positive electrode active material, the positive electrode active material including secondary particles, the secondary particles being an aggregate comprising multiple primary particles; the primary particles including a positive electrode active material.

[0008] In any of the secondary particles, the direction from the center of the secondary particle toward the surface is denoted as the X direction; the X direction passing through the center of any of the primary particles is denoted as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is denoted as the a-axis.

[0009] The secondary particles include oriented secondary particles; in the oriented secondary particles, based on the total number of primary particles in the oriented secondary particles, the proportion of primary particles in the oriented secondary particles that form an angle α1 between the a-axis and the longitudinal direction is denoted as F1, where 15°≤α1≤45°, F1≥60%.

[0010] The positive electrode active material includes oriented secondary particles, which in turn include a certain number of primary particles whose a-axis forms a certain angle α1 with the corresponding longitudinal direction. On the one hand, by controlling the proportion F1 of primary particles with the aforementioned angle α1 in the oriented secondary particles to be within the aforementioned range, it is beneficial to suppress the penetration of electrolyte into the grain boundaries of the secondary particles and to suppress side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual specific capacity and cycle life of the positive electrode active material. On the other hand, by controlling the angle α1 within the aforementioned angle range, a shorter active ion insertion / extraction path can also be achieved, which is beneficial to promote the rapid insertion / extraction of active ions in the positive electrode active material during charge and discharge, thereby improving the actual energy density of the secondary battery and enabling the secondary battery to have good kinetic performance.

[0011] In some embodiments, the included angle α1 is obtained as follows: in a cross section passing through the center of the oriented secondary particle, the direction from the center of the oriented secondary particle toward the surface of the oriented secondary particle is taken as the X direction; the X direction passing through the center of the cross section of the primary particle is taken as the longitudinal direction corresponding to the primary particle; the longest axis in the cross section of the primary particle is denoted as the a-axis; and the included angle α1 is obtained according to the angle formed by the a-axis and the corresponding longitudinal direction.

[0012] The parameter α1 can be statistically analyzed using a cross-sectional view passing through the center of the oriented secondary particle.

[0013] In some implementations, F1 ≥ 64%.

[0014] By controlling the proportion (F1) of primary particles forming an angle α1 between the a-axis and the longitudinal direction in the oriented secondary particles within the aforementioned range, on the one hand, it is beneficial to more effectively suppress the infiltration of electrolyte into the grain boundaries of secondary particles, thereby more effectively suppressing the side reactions between the electrolyte and the surface of the positive electrode active material, and better improving the actual specific capacity and cycle life of the positive electrode active material; on the other hand, it is more beneficial to provide a shorter active ion insertion / extraction path, thereby more beneficial to improving the actual energy density and good kinetic performance of the secondary battery.

[0015] In some embodiments, the proportion of the oriented secondary particles in the secondary particles is denoted as P2, which satisfies P2≥60%.

[0016] In some implementations, P2 ≥ 75%.

[0017] By controlling the proportion (P2) of oriented secondary particles in secondary particles within the aforementioned range, it is beneficial to more significantly leverage the comprehensive improvement effect of oriented secondary particles on the high energy density, kinetic performance, and long cycle life of secondary batteries.

[0018] In some embodiments, the length of the primary particle along the longitudinal direction is denoted as L, the length of the primary particle perpendicular to the longitudinal direction is denoted as W, and the ratio of L to W in the primary particle is denoted as R. L / W ;

[0019] In the oriented secondary particles, the R of the primary particles L / W Less than or equal to 4.

[0020] By adjusting the angle α1 between the a-axis of the primary particle and the corresponding longitudinal direction, the length ratio R of the primary particle in the longitudinal and transverse directions (the transverse direction being the direction perpendicular to the longitudinal direction) can be adjusted. L / W Furthermore, by using R L / W Adjusting the arrangement within the aforementioned range is beneficial for the primary particles to be more densely packed in the radial (X direction) direction of the oriented secondary particles, thereby improving the energy density of the battery.

[0021] In some implementations, the L value, the W value, and the R value L / W The value is obtained as follows: In a cross-section passing through the center of the oriented secondary particle, the direction from the center of the oriented secondary particle toward the surface of the oriented secondary particle is taken as the X direction; the X direction passing through the center of the cross-section of the primary particle is taken as the longitudinal direction corresponding to that primary particle; the L value is obtained based on the length value of the primary particle along the corresponding longitudinal direction; the W value is obtained based on the length value of the primary particle along the direction perpendicular to the corresponding longitudinal direction; and the R value is obtained based on the ratio obtained by dividing the L value by the W value. L / W value.

[0022] The parameters L, W, and R can be analyzed using a cross-sectional view passing through the center of the oriented secondary particle. L / W Perform statistical analysis.

[0023] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics:

[0024] In the oriented secondary particles, the R of the primary particles L / W Satisfy 0 <R L / W ≤4;

[0025] In the oriented secondary particles, the R of the primary particles L / W The average value is 1.5 to 2.5.

[0026] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics:

[0027] In the oriented secondary particles, the R of the primary particles L / W Satisfying 0.95≤R L / W ≤4;

[0028] In the oriented secondary particles, the R of the primary particles L / W The average value is 1.5 to 2.0.

[0029] By adjusting the R of the primary particles in the oriented secondary particles L / W Range of values ​​and R L / W If one or two parameters of the average value are within the aforementioned range, the orientation and orientation distribution characteristics of the primary particles can be controlled, which can better balance the inhibition of electrolyte penetration and the reversible insertion / extraction efficiency of active ions, and is conducive to better balancing high energy density, cycle performance and good kinetic performance.

[0030] In some embodiments, the distance from the center to the surface of the oriented secondary particle is denoted as R; the portion from the center of the oriented secondary particle to a position 2 / 3R from the center is denoted as the inner layer, and the portion from a position 2 / 3R from the center to the surface of the oriented secondary particle is denoted as the outer layer.

[0031] In the oriented secondary particles, the inner layer R L / W The average value is denoted as R. MI The outer R L / W The average value is denoted as R. MO , where R MI <R MO .

[0032] In the case where a single particle forms the aforementioned included angle α1, further control of R... MI <R MO This facilitates the faster insertion and extraction of active ions located on the outer layer and surface of secondary particles, and is more conducive to improving the dynamic performance of positive electrode active materials and batteries.

[0033] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0034] In the oriented secondary particles, R MI <1.8, R MO ≥1.8;

[0035] In the oriented secondary particles, the outer layer R L / W Satisfying 1.2≤R L / W ≤4, the inner layer R L / W Satisfying 0.95≤R L / W ≤2.8.

[0036] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0037] In the oriented secondary particles, 1.3 ≤ R MI <1.8, 1.8≤R MO ≤2.3;

[0038] In the oriented secondary particles, at least 80% of the primary particles in the outer layer have an R... L / W Satisfying 1.4≤R L / W ≤4, R of at least 80% of the primary particles in the inner layer L / W Satisfying 0.95≤R L / W ≤2.0.

[0039] By controlling the inner layer R in oriented secondary particles L / W Values, Inner R L / W Mean (R) MI ), outer R L / W Values ​​and outer R L / W Mean (R) MO With the aforementioned combination, the orientation distribution of primary particles in the inner and outer layers can be better controlled, which is conducive to improving the reversible insertion and extraction efficiency of active ions in the outer primary particles, while also inhibiting electrolyte penetration, and is more conducive to achieving good cycle performance and kinetic performance.

[0040] In some embodiments, in the oriented secondary particles, the R of the primary particles L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0041] By controlling the R of the primary particles in the oriented secondary particles L / W The arrangement of particles from the center to the surface allows for better control over the orientation distribution of primary particles within the oriented secondary particles. This is beneficial for improving the reversible insertion / extraction efficiency of active ions in the outer primary particles, while also inhibiting electrolyte penetration. Furthermore, it helps to achieve both good cycle performance and kinetic performance.

[0042] In some embodiments, the anisotropy index of the angle α1 is denoted as I, based on the number of primary particles in the oriented secondary particles whose a-axis forms an angle α1 with the longitudinal direction. α1 Then 0.4≤I α1 ≤2.5;

[0043] In the cross-section passing through the center of the oriented secondary particle, the angle α1 by which the a-axis deviates clockwise from the corresponding longitudinal direction is denoted as a positive angle, and the angle α1 by which the a-axis deviates counterclockwise from the corresponding longitudinal direction is denoted as a negative angle. α1 It is the ratio of the number of positive angles to the number of negative angles.

[0044] In some implementations, 0.5 ≤ Iα1 ≤2.0.

[0045] The aforementioned parameter I can be used α1 To further reflect the orientation direction distribution of primary particles forming an angle α1 in the oriented secondary particles, by using I α1 By controlling the process within the aforementioned range, the primary particles at an angle α1 can have a relatively disordered orientation, which is more conducive to suppressing the penetration of electrolyte into the grain boundaries of secondary particles and is more conducive to improving the actual specific capacity and cycle life of the positive electrode active material.

[0046] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0047] The positive electrode active material D v 50 is 8μm to 11μm;

[0048] At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100 nm to 1600 nm, wherein the diameter of the primary particle refers to the maximum length of the primary particle in each direction.

[0049] The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / D v 50, where 1.1≤SPAN≤1.4.

[0050] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0051] The positive electrode active material D v 50 is 9μm to 10μm;

[0052] At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 400 nm to 1500 nm.

[0053] The SPAN of the positive electrode active material satisfies: 1.2≤SPAN≤1.3.

[0054] By adjusting the D of the positive electrode active material v Within the aforementioned range, the particles in the positive electrode active material can have a more suitable particle size distribution, thereby having a more suitable specific surface area. This is beneficial for both suppressing side reactions and having a shorter active ion transport distance, thus enabling the secondary battery to have both good cycle performance and kinetic performance.

[0055] By adjusting the diameter of the primary particles in the oriented secondary particles within the aforementioned range, it is beneficial to control the proportion of active crystal faces of the primary particles, thereby further improving the lithium-ion insertion / extraction kinetics of the primary particles.

[0056] By adjusting the particle size distribution parameter SPAN of the positive electrode active material within the aforementioned range, it is beneficial to ensure that large and small particles in the positive electrode active material have appropriate volume ratios, resulting in a positive electrode active material with both high capacity and high powder compaction density, which is conducive to maximizing the volumetric energy density on the positive electrode side. By designing a combination of large and small particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material.

[0057] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0058] The positive electrode active material D v 90 satisfies: 15μm≤D v 90≤18μm;

[0059] The positive electrode active material D v 10 satisfies: 4μm≤D v 10≤6μm;

[0060] The positive electrode active material D m 10 satisfies: D n 10≥2μm.

[0061] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0062] The positive electrode active material D v 90 satisfies: 16μm≤D v 90≤17μm;

[0063] The positive electrode active material D v 10 satisfies: 4.5μm≤D v 10≤5.5μm.

[0064] By controlling the D of the positive electrode active material v Within the aforementioned range, 90% is beneficial for controlling the appropriate volume ratio of large particles in the material, which is beneficial for controlling the specific surface area and suppressing side reactions.

[0065] By controlling the D of the positive electrode active material v 10 Within the aforementioned range, it is beneficial to control the small particles in the material to have a suitable volume ratio, which is beneficial to improving the compaction density of the material.

[0066] By controlling the D of the positive electrode active material n10 Within the aforementioned range, the number of small particles in the material can be controlled within a more suitable range, which is beneficial for controlling a more suitable specific surface area, thereby improving the battery's storage life.

[0067] In some embodiments, the positive electrode active material in the oriented secondary particles includes a layered lithium-ion active material.

[0068] In some embodiments, the positive electrode active material in the oriented secondary particles includes a lithium-nickel composite oxide.

[0069] By introducing lithium-nickel composite oxide into the positive electrode active material of oriented secondary particles, the introduction of nickel element is beneficial to improving the energy density of the positive electrode active material. In addition, it is also beneficial to improve the power performance of the battery.

[0070] In some embodiments, the molar ratio of nickel to oxygen in the lithium-nickel composite oxide is denoted as Q. Ni / O Where 0.3≤Q Ni / O ≤0.5.

[0071] By adjusting the molar ratio (Q) of nickel to oxygen in lithium-containing nickel composite oxides Ni / O By controlling the content within the aforementioned range, the positive electrode active material can have a high nickel content, which is more conducive to improving the energy density of the positive electrode active material.

[0072] In some embodiments, the oriented secondary particles satisfy one or more of the following characteristics:

[0073] In the oriented secondary particles, 0.4 ≤ Q Ni / O ≤0.5;

[0074] The lithium-containing nickel composite oxide contains at least one of cobalt (Co) and M, wherein the M element is at least one of Mn and Al.

[0075] The lithium-nickel composite oxide contains a doping element, Q. Ni / O <0.5, wherein the doping element includes at least one element selected from Zr, Al, B, Sr and Ca;

[0076] At least a portion of the primary particles include a particle body and a coating layer located on at least a portion of the surface of the particle body, the particle body comprising a lithium-nickel composite oxide, and the coating layer comprising at least one element selected from Zr, Al, B, Sr, and Ca.

[0077] By Q Ni / O Within the aforementioned range, lithium-nickel composite oxides, with their high nickel content, can significantly improve the energy density of positive electrode active materials.

[0078] Introducing cobalt (Co) into lithium-nickel composite oxides helps stabilize the material structure and improves the cycle and rate performance of the positive electrode active material.

[0079] Introducing manganese (Mn) into lithium-nickel composite oxides can help reduce costs and improve the structural stability of the material.

[0080] Introducing aluminum (Al) into lithium-nickel composite oxides can improve the cycling stability of the material.

[0081] By modifying lithium-nickel composite oxides through one or more of the aforementioned doping and coating methods, it is possible to enhance the material's stability, increase its energy density, and improve its cycle life. For example, bulk doping can stabilize the structure of lithium-nickel composite oxides. For example, by depositing fast-ion conductor coatings on the surface of lithium-nickel composite oxides, the material's energy density and cycle life can be improved.

[0082] In some embodiments, in the oriented secondary particles, 0.3 ≤ Q Ni / O ≤0.5; Further, in the oriented secondary particles, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and any of the aforementioned modified forms, wherein the modified forms include one or more of doping modification and coating modification, the doping element used for the doping modification includes at least one element selected from Zr, Al, B, Sr, and Ca, and the coating element used for the coating modification includes at least one element selected from Zr, Al, B, Sr, and Ca;

[0083] The molar ratio R of nickel and oxygen in the positive electrode active material Ni / O Satisfying 0.4≤R Ni / O ≤0.5.

[0084] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0085] The positive electrode active material D v 50 is 8μm to 11μm, and can be selected as 9μm to 10μm;

[0086] At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100 nm to 1600 nm, and may be selected in the range of 400 nm to 1500 nm.

[0087] The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / Dv 50, where 1.1≤SPAN≤1.4, and optionally, 1.2≤SPAN≤1.3.

[0088] Oriented secondary particles can incorporate ternary cathode active materials with high nickel content and their modified forms. Modification methods can include one or more of doping and coating modifications. This allows for the production of high-energy-density, long-life ternary cathode active materials. Bulk doping can stabilize the structure of the ternary cathode active material, while coating the surface of the ternary cathode active material with fast-ion conductors can improve the material's energy density and cycle life. By controlling the included angles α1 and F1, the orientation and distribution of primary particles in the secondary particles of the cathode active material can be controlled, achieving a balance between suppressing electrolyte penetration and optimizing lithium-ion transport path distance, thereby improving the material's mass energy density and lithium-ion diffusion kinetics. Furthermore, by controlling the D... v 50. If the diameter of the primary particles in the oriented secondary particles and one or more parameters of the particle size distribution parameter SPAN of the positive electrode active material are within the aforementioned range, the aforementioned advantages can be further combined. For example, by adjusting the particle size distribution parameter SPAN of the positive electrode active material within the aforementioned range, it is beneficial to ensure that large and small particles in the positive electrode active material have appropriate volume ratios, which can further improve the powder compaction density of the material and the volumetric energy density of the positive electrode sheet. By designing a combination of large and small particles in the secondary particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material. Furthermore, doping and coating modification methods can be combined to improve the bulk structure and surface stability of the material, thereby achieving a longer cycle life.

[0089] In some embodiments, in the oriented secondary particles, the average L value of the inner layer is less than 700 nm, and the average L value of the outer layer is greater than or equal to 720 nm.

[0090] Wherein, the length value of the primary particle along the longitudinal direction is denoted as L, and the distance from the center to the surface of the oriented secondary particle is denoted as R; the portion from the center of the oriented secondary particle to a position 2 / 3R away from the center is denoted as the inner layer, and the portion from a position 2 / 3R away from the center to the surface of the oriented secondary particle is denoted as the outer layer.

[0091] In some embodiments, in the oriented secondary particles, the average L value of the inner layer is less than or equal to 660 nm, and the average L value of the outer layer is greater than or equal to 750 nm.

[0092] For positive electrode active materials in oriented secondary particles, including positive electrode active materials containing lithium nickel composite oxides, by controlling the average L value of the inner and outer layers in the oriented secondary particles within the aforementioned range, the outer layer can have a faster reversible insertion / extraction efficiency of active ions, and the inner layer can have a larger angle to better suppress electrolyte penetration into the grain boundaries, thus making it more conducive to comprehensively improving the actual energy density, cycle performance and kinetic performance of the battery.

[0093] In some embodiments, the secondary battery further includes a negative electrode, a separator, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode.

[0094] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0095] In a second aspect of this application, a positive electrode active material is provided.

[0096] In some embodiments, the positive electrode active material includes secondary particles, which are aggregates comprising primary particles; the primary particles include a positive electrode active substance.

[0097] In any of the secondary particles, the direction from the center of the secondary particle toward the surface is denoted as the X direction; the X direction passing through the center of any of the primary particles is denoted as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is denoted as the a-axis.

[0098] The secondary particles include oriented secondary particles; in the oriented secondary particles, based on the total number of primary particles in the oriented secondary particles, the proportion of primary particles in the oriented secondary particles that form an angle α1 between the a-axis and the longitudinal direction is denoted as F1, where 15°≤α1≤45°, F1≥60%.

[0099] The positive electrode sheet prepared using the aforementioned positive electrode active material can be used to prepare secondary batteries with high energy density, good kinetic performance, and long cycle life. By utilizing the orientation angle and the proportion of primary particles included in the oriented secondary particles in the positive electrode active material, it is possible to suppress the penetration of electrolyte into the grain boundaries of the secondary particles, which is beneficial for suppressing side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual specific capacity and cycle life of the positive electrode active material. Furthermore, it is possible to achieve a shorter active ion insertion / extraction path, which is beneficial for promoting the rapid insertion / extraction of active ions during charge and discharge, thereby improving the actual energy density of the secondary battery and enabling the secondary battery to have good kinetic performance.

[0100] In some embodiments, the positive electrode active material described in the first aspect of this application is provided.

[0101] In a third aspect of this application, an electrical device is provided, comprising at least one of the secondary battery described in the first aspect of this application and the positive electrode active material described in the second aspect of this application.

[0102] Details of one or more embodiments or examples of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0103] To better describe and illustrate the embodiments, examples, or models provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments, examples, or models, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0104] Figure 1 is a schematic diagram of the relevant parameters of the oriented secondary particles in one embodiment of this application, which shows only the cross-section of a portion of the primary particles at the two-dimensional cross-section of the oriented secondary particles.

[0105] Figure 2 shows the experimental results of a cross-sectional view of oriented secondary particles in one embodiment of this application.

[0106] Figure 3 is a schematic diagram of a battery cell according to one embodiment of this application.

[0107] Figure 4 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 3.

[0108] Figure 5 is a schematic diagram of a battery module according to one embodiment of this application.

[0109] Figure 6 is a schematic diagram of a battery pack according to one embodiment of this application.

[0110] Figure 7 is an exploded view of the battery pack of one embodiment of this application shown in Figure 6.

[0111] Figure 8 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0112] Explanation of reference numerals in the attached drawings: 52, electrode assembly; 1, battery pack; 2, upper casing; 3, lower casing; 4, battery module; 5, individual battery cell; 51, housing; 53, cover plate; 6, electrical device. Detailed Implementation

[0113] The following describes in detail some embodiments and examples of the secondary battery, positive electrode active material, and electrical device of this application, with appropriate reference to the accompanying drawings. However, some unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0114] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently and can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0115] In this application, the terms "multiple," "various," "multiple items," "several," etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more (≥, greater than or equal to) two. It can be understood that when "any number of" items are involved, it refers to any suitable combination of multiple items, that is, a combination of "any number of" items in a manner that does not conflict and enables the implementation of this application.

[0116] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0117] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0118] Those skilled in the art will understand that the order in which the steps are written in the various implementations or embodiments does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application may be performed sequentially or randomly, but are preferably performed sequentially. For example, if method M includes steps (a) and (b), it means that method M may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. As another example, method M may also include step (c), meaning that step (c) can be added to method M in any order. For example, method M may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0119] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both features or solutions where "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3," and features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0120] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0121] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. Unless otherwise specified, the descriptions such as "optionally include" and "optionally contain" in this application, taking "optionally include" as an example, mean "may include or not include."

[0122] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0123] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0124] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that enables the implementation of this application.

[0125] In this document, terms such as "preferred," "better," "more suitable," "ideal," "good," and "superior" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0126] In this application, terms such as "further," "even more," "especially," "for example," "as," "example," and "exemplary" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0127] In this application, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0128] In this application, the term "room temperature" generally refers to 4℃ to 35℃, and may refer to 20℃ ± 5℃. In some embodiments of this application, room temperature refers to 20℃ to 30℃.

[0129] In this application, if the unit for a data range is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 3~5h or 3-5h both mean that the unit for the left endpoint "3" and the right endpoint "5" is h (hours), and both have the same meaning as 3h~5h. Furthermore, similar descriptions of other parameters such as temperature and size are interpreted in the same way.

[0130] The weight or mass of the relevant components mentioned in the embodiments or examples of this application can refer not only to the content of each component, but also to the proportional relationship of weight or mass between the components. Therefore, as long as the content of the relevant components is scaled up or down proportionally according to the embodiments or examples of this application, it is within the scope described in this application. Furthermore, the mass involved in the embodiments or examples of this application can be a mass unit known in the chemical industry, such as microgram (μg), milligram (mg), gram (g), kilogram (kg). Unless otherwise specified, the mass ratio is equal to the corresponding weight ratio. For example, if the mass of substance A is m1 and the weight is W1, and the mass of substance B is m2 and the weight is W2, then the mass ratio m1 / m2 is numerically equal to the corresponding weight ratio W1 / W2.

[0131] In this application, unless otherwise specified, wt% means weight percentage, which is numerically equal to the corresponding mass percentage.

[0132] In this application, "greater than or equal to", "greater than or equal to", and "≥" have the same meaning and can be used interchangeably; "less than or equal to", "less than or equal to", and "≤" have the same meaning and can be used interchangeably; "greater than" can be equivalently represented as ">", and "less than" can be equivalently represented as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be considered as providing two additional solutions: "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be considered as providing two additional solutions: "less than" and "equal to".

[0133] In this application, the exemplary descriptions such as "in some implementations (or embodiments)" and "in one implementation (or embodiment)" may cover, but are not limited to, the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0134] A common approach to cathode active materials is through polycrystalline materials, where secondary particles consist of multiple primary particles. Taking lithium-ion active materials as an example, the longest axis (a-axis) of the primary particles in the obtained secondary particles is typically aligned with the direction from the center to the surface of the secondary particle. This can improve the kinetics of lithium-ion insertion / extraction by shortening the lithium-ion transport distance. However, due to the overly regular orientation of the primary particles, significant through-channels exist between them, allowing electrolyte to easily penetrate into the secondary particles, causing more severe interfacial side reactions. This reduces the cycle performance and actual specific capacity of the cathode active material, ultimately degrading its cycle life.

[0135] In view of this, this application provides a secondary battery, a positive electrode active material, and an electrical device. This secondary battery combines high energy density, good kinetic performance, and long cycle life.

[0136] In some embodiments, the secondary battery includes a positive electrode sheet, which includes a positive electrode active material. The positive electrode active material includes secondary particles, which are aggregates of multiple primary particles. In any primary particle, the longest axis of the primary particle is denoted as the a-axis. The X-direction passing through the center of any primary particle is denoted as the longitudinal direction. In any secondary particle, the direction from the center of the secondary particle to the surface is denoted as the X-direction. The secondary particles include oriented secondary particles. In the oriented secondary particles, based on the total number of primary particles in the oriented secondary particles, the proportion of primary particles in the oriented secondary particles that form an angle α1 between the a-axis and the longitudinal direction is denoted as F1, where 15°≤α1≤45° and F1≥60%.

[0137] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0138] In this application, unless otherwise specified, the electrode sheet can be a positive electrode sheet or a negative electrode sheet, and the "active material" in the electrode sheet refers to a material capable of reversibly inserting and extracting active ions. Unless otherwise specified, "negative electrode active material" refers to a material used in the negative electrode sheet that is capable of reversibly inserting and extracting active ions; "positive electrode active material" refers to a material used in the positive electrode sheet that is capable of reversibly extracting and inserting active ions. When the battery cell or secondary battery is charged, active ions are extracted from the positive electrode and inserted into the negative electrode through the electrolyte; while when the battery cell or secondary battery is discharged, active ions are extracted from the negative electrode and inserted into the positive electrode. The active ions are not particularly limited. In some embodiments, the active ions may include lithium ions. Non-limitingly, the active ions may be lithium ions, in which case the battery cell is a lithium-ion battery cell and the secondary battery is a lithium-ion secondary battery.

[0139] In this application, "electrode sheet" and "electrode plate" have the same meaning and can be used interchangeably; "electrode active material" and "active material" have the same meaning and can be used interchangeably.

[0140] In this application, unless otherwise specified, "electrode active material layer" includes at least one of the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet. Depending on the specific circumstances, the electrode active material layer may refer to either the positive active material layer or the negative active material layer. It is understood that the positive active material layer contains a positive active substance, and the negative active material layer contains a negative active substance. In this application, "electrode active material layer" may also be abbreviated as "active material layer".

[0141] In this application, unless otherwise specified, "separation membrane" and "diaphragm" have the same meaning and can be used interchangeably.

[0142] It is understandable that both "primary particles" and "secondary particles" are particles that include positive electrode active materials.

[0143] In this application, "primary particle" and "secondary particle" are terms well known in the art. "Primary particle" refers to a single crystal or near-single crystal grain. "Secondary particle" refers to an aggregated particle composed of two or more primary particles. Primary particles and secondary particles can be easily distinguished experimentally, for example, by using SEM images taken with a scanning electron microscope (SEM), but are not limited thereto.

[0144] In a first aspect of this application, a secondary battery is provided, which includes a positive electrode sheet, the positive electrode sheet including a positive electrode active material, and the positive electrode active material including oriented secondary particles.

[0145] In some embodiments, a secondary battery is provided, which includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, the positive electrode active material includes secondary particles, the secondary particles are aggregated particles including a plurality of primary particles; the primary particles include a positive electrode active material;

[0146] In any secondary particle, the direction from the center of the secondary particle toward the surface is denoted as the X direction; the X direction passing through the center of any primary particle is denoted as the longitudinal direction; in any primary particle, the longest axis of the primary particle is denoted as the a-axis.

[0147] Secondary particles include oriented secondary particles; in oriented secondary particles, based on the total number of primary particles in oriented secondary particles, the proportion of primary particles that form an angle α1 between the a-axis and the longitudinal direction in oriented secondary particles is denoted as F1, where 15°≤α1≤45° and F1≥60%.

[0148] In this application, unless otherwise specified, "X direction" refers to the direction from the center of the secondary particle toward the surface. It can be understood that different positions from the center of the secondary particle toward the surface of the secondary particle correspond to different X directions; each position on the surface of the secondary particle corresponds to its respective X direction.

[0149] In this application, unless otherwise specified, "longitudinal" refers to the direction that passes through both the center of a secondary particle and the center of a primary particle. It can be understood that different primary particles correspond to different longitudinal directions, and each primary particle corresponds to its own specific longitudinal direction.

[0150] In this application, unless otherwise specified, the "a-axis" of a primary particle refers to the longest axis of the primary particle in all directions. Typically, the longest axis in a two-dimensional cross-section of the primary particle can be used as the test result for the length of the a-axis.

[0151] In this application, unless otherwise specified, the proportion of primary particles forming an angle α1 between the a-axis and the longitudinal direction in the oriented secondary particles is denoted as F1.

[0152] In this application, unless otherwise specified, "oriented secondary particles" refers to a certain number of primary particles possessing the following characteristics: the a-axis of the primary particle forms a certain angle with the corresponding longitudinal direction. Unless otherwise specified, the angle formed by the a-axis of the primary particle and the corresponding longitudinal direction is denoted as "α1", and can be referred to as "angle α1". Unless otherwise specified, the proportion of primary particles whose a-axis forms angle α1 with the longitudinal direction in the oriented secondary particles is denoted as "F1". In this application, generally, when secondary particles satisfy 15°≤α1≤45° and F1≥60%, they are determined to be oriented secondary particles.

[0153] The positive electrode active material includes oriented secondary particles, which in turn include a certain number of primary particles whose a-axis forms a certain angle α1 with the corresponding longitudinal direction. On the one hand, by controlling the proportion F1 of primary particles with the aforementioned angle α1 in the oriented secondary particles to be within the aforementioned range, it is beneficial to suppress the penetration of electrolyte into the grain boundaries of the secondary particles and to suppress side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual specific capacity and cycle life of the positive electrode active material. On the other hand, by controlling the angle α1 within the aforementioned angle range, a shorter active ion insertion / extraction path can also be achieved, which is beneficial to promote the rapid insertion / extraction of active ions in the positive electrode active material during charge and discharge, thereby improving the actual energy density of the secondary battery and enabling the secondary battery to have good kinetic performance.

[0154] In some embodiments of this application, the included angle α1 can be obtained as follows: in a cross section passing through the center of the orientation secondary particle, the direction from the center of the orientation secondary particle toward the surface of the orientation secondary particle is taken as the X direction; the X direction passing through the center of the cross section of the primary particle is taken as the longitudinal direction corresponding to the primary particle; the longest axis in the cross section of the primary particle is denoted as the a axis; and the included angle α1 is obtained according to the included angle formed by the a axis and the corresponding longitudinal direction.

[0155] The parameter α1 can be statistically analyzed using a cross-sectional view passing through the center of the oriented secondary particle. It is understood that the cross-sectional view passing through the center of the oriented secondary particle can display the cross-section and profile of both the oriented secondary particle and the primary particle. Unless otherwise specified, the center of the oriented secondary particle can be determined as follows: based on the cross-sectional profile of the oriented secondary particle, the intersection of the longest and shortest axes in the cross-section is taken as the center of the oriented secondary particle.

[0156] Statistical analysis of primary particle parameters in oriented secondary particles can be performed using ion polishing cross-sectional morphology analysis. Non-limitingly, the secondary particles can be cut to form a cross-section essentially penetrating the center of the secondary particle, obtaining a sample with this cut surface. Further statistical analysis of primary particle parameters in the cross-sectional image of the secondary particle can then be performed using microscopic morphology observation methods. Non-limitingly, instruments or equipment including, but not limited to, focused electron beam (FIB) microscopy (non-limiting examples such as the FEI Scios 2HiVac device), and ion cross-section polishing instruments (non-limiting examples such as the JEOL IB-09010CP argon ion cross-section polishing instrument and the IB-19500CP ion cross-section polishing instrument) can be used to obtain the cross-section essentially penetrating the center of the secondary particle. Microscopic morphology observation methods can employ instruments or equipment including, but not limited to, scanning electron microscopy (SEM) technology. Non-limiting examples of SEM instruments include the ZEISS Sigma 300 scanning electron microscope and the Apreo 2SEM field emission scanning electron microscope. In some implementations, a cross-sectional image passing through the center of a secondary particle is obtained by combining ion polishing cross-sectional morphology analysis with scanning electron microscopy (SEM).

[0157] The above method can be used to analyze parameters including but not limited to: the a-axis of a primary particle, the angle between the a-axis of a primary particle and the corresponding longitudinal direction (angle α1), the proportion F1 of primary particles forming angle α1 between the a-axis and the longitudinal direction, the deviation direction of angle α1 relative to the X direction, and the anisotropy index I of angle α1. α1 The length L of the primary particle along the longitudinal direction, the length W of the primary particle perpendicular to the longitudinal direction, and the inner layer R L / W Mean (R) MI ), outer R L / W Mean (R) MO The determination methods for some of the above parameters can be found in Figure 1. The testing and analysis methods can also be described in the embodiments section below. It should be noted that Figure 1 only shows a portion of the primary particle cross-section at the orientation-type secondary particle cross-section.

[0158] In some embodiments, the oriented secondary particles are spherical or near-spherical. The aspect ratio of the "near-spherical particles" is close to 1, with non-limiting examples ranging from 0.8 to 1.2. The aspect ratio of near-spherical particles refers to the ratio of their longest axis to their shortest axis. It can be tested and analyzed using methods and conventional instruments known in the art.

[0159] In some implementations, F1 ≥ 60%, which can be F1 ≥ 64%, or any of the following percentages, or greater than or equal to any of the following percentages, or selected from the range formed by any of the following percentages and 100%: 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 80%, 85%, 90%, 95%, etc. Non-limitingly, F1 can also be any of the following ranges: 60%–100%, 70%–100%, 60%–90%, 70%–90%, etc.

[0160] By controlling the proportion (F1) of primary particles forming an angle α1 between the a-axis and the longitudinal direction in the oriented secondary particles within the aforementioned range, on the one hand, it is beneficial to more effectively suppress the infiltration of electrolyte into the grain boundaries of secondary particles, thereby more effectively suppressing the side reactions between the electrolyte and the surface of the positive electrode active material, and better improving the actual specific capacity and cycle life of the positive electrode active material; on the other hand, it is more beneficial to provide a shorter active ion insertion / extraction path, thereby more beneficial to improving the actual energy density and good kinetic performance of the secondary battery.

[0161] In this application, unless otherwise specified, the proportion of oriented secondary particles in the secondary particles is denoted as P2.

[0162] In some embodiments, P2 ≥ 60%, optionally P2 ≥ 70%, further optionally P2 ≥ 75%, and may also be any of the following percentages, or greater than or equal to any of the following percentages, or selected from any two of the following percentages, or selected from any of the following percentages and 100%: 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 72%, 75%, 80%, 85%, 90%, 95%, 99%, etc. Non-limitingly, P2 may also be any of the following ranges: 60%–100%, 70%–100%, 80%–100%, 90%–100%, etc.

[0163] By controlling the proportion (P2) of oriented secondary particles in secondary particles within the aforementioned range, it is beneficial to more significantly leverage the comprehensive improvement effect of oriented secondary particles on the high energy density, kinetic performance, and long cycle life of secondary batteries.

[0164] P2 can be obtained using the following method, but is not limited to: Based on a randomly selected cross-sectional image including at least 10 secondary particles, determine whether it is an oriented secondary particle based on the SEM analysis results of the cross-sectional image passing through the center of the secondary particle. When 15°≤α1≤45° and F1≥60%, it is counted as one oriented secondary particle; if α1 is not within the above range or F1<60%, it is not counted as an oriented secondary particle. Calculate the percentage of oriented secondary particles based on the counting results.

[0165] In this application, unless otherwise specified, the length of a primary particle along its longitudinal direction is denoted as L, the shortest length of a primary particle perpendicular to its longitudinal direction is denoted as W, and the ratio of L to W in a primary particle is denoted as R. L / W .

[0166] In some embodiments, in oriented secondary particles, the R of the primary particles L / W Less than or equal to 4.

[0167] By adjusting the angle α1 between the a-axis of the primary particle and the corresponding longitudinal direction, the length ratio R of the primary particle in the longitudinal and transverse directions (the transverse direction being the direction perpendicular to the longitudinal direction) can be adjusted. L / W Furthermore, by using R L / W Adjusting the arrangement within the aforementioned range is beneficial for the primary particles to be more densely packed in the radial (X direction) direction of the oriented secondary particles, thereby improving the energy density of the battery.

[0168] In some implementations, the L value, W value, and R... L / W The value can be obtained as follows: In a cross-section passing through the center of the oriented secondary particle, the direction from the center of the oriented secondary particle toward its surface is taken as the X direction; the X direction passing through the center of the cross-section of the primary particle is taken as the longitudinal direction corresponding to that primary particle; the L value is obtained based on the length of the primary particle along the corresponding longitudinal direction; the W value is obtained based on the length of the primary particle along the direction perpendicular to the corresponding longitudinal direction; and the R value is obtained based on the ratio of the L value to the W value. L / W value.

[0169] The parameters L, W, and R can be analyzed using a cross-sectional view passing through the center of the oriented secondary particle. L / W Perform statistical analysis.

[0170] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0171] In oriented secondary particles, the R of the primary particles L / W Satisfy 0 <R L / W ≤4, optionally, 0.95≤RL / W ≤4;

[0172] In oriented secondary particles, the R of the primary particles L / W The average value is 1.5 to 2.5, and can be selected as 1.5 to 2.0.

[0173] In some embodiments, in oriented secondary particles, the R of the primary particles L / W Satisfy 0 <R L / W ≤4, optionally, 0.95≤R L / W ≤4. Non-restrictive, R of primary particles L / W The average value can also be any of the following values, or a range selected from any two of the following values: 0.95, 0.96, 0.98, 1, 1.0, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.0, 2.1, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.0, 3.2, 3.4, 3.5, 3.6, 3.7, 3.8, 4.0, 4, etc. For example, the R of a primary particle... L / W The average value can also be selected from any of the following ranges: 0.95 ≤ R L / W ≤3.8, 0.95≤R L / W ≤3.7, 0.98≤R L / W ≤3.67, etc.

[0174] In some embodiments, in oriented secondary particles, the R of the primary particles L / W The average value is 1.5–2.5, and can be optionally 1.5–2.0. Non-limitingly, the R of primary particles... L / W The average value can also be any of the following values, or a range consisting of any two of the following values: 1.5, 1.6, 1.7, 1.8, 1.85, 1.86, 1.9, 2, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, etc.

[0175] By adjusting the R of the primary particles in the oriented secondary particles L / W Range of values ​​and R L / W If one or two parameters of the average value are within the aforementioned range, the orientation and orientation distribution characteristics of the primary particles can be controlled, which can better balance the inhibition of electrolyte penetration and the reversible insertion / extraction efficiency of active ions, and is conducive to better balancing high energy density, cycle performance and good kinetic performance.

[0176] In this application, unless otherwise specified, the distance from the center to the surface of the orientation secondary particle is denoted as R; the portion from the center of the orientation secondary particle to a position 2 / 3R from the center is denoted as the inner layer, and the portion from a position 2 / 3R from the center to the surface of the orientation secondary particle is denoted as the outer layer.

[0177] In this application, unless otherwise stated, in oriented secondary particles, the inner layer R L / W The average value is denoted as R. MI The outer R L / W The average value is denoted as R. MO .

[0178] In some implementations, R MI <R MO .

[0179] In the case where a single particle forms the aforementioned included angle α1, further control of R... MI <R MO This facilitates the faster insertion and extraction of active ions located on the outer layer and surface of secondary particles, and is more conducive to improving the dynamic performance of positive electrode active materials and batteries.

[0180] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0181] In oriented secondary particles, R MI <1.8 (optional: 1.3≤R) MI <1.8), R MO ≥1.8 (optional: 1.8≤R) MO ≤2.3);

[0182] In oriented secondary particles, the outer R L / W Satisfying 1.2≤R L / W ≤4, inner layer R L / W Satisfying 0.95≤R L / W ≤2.8.

[0183] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0184] In oriented secondary particles, 1.3 ≤ R MI <1.8, 1.8≤R MO ≤2.3;

[0185] In oriented secondary particles, at least 80% of the primary particles in the outer layer have R L / W Satisfying 1.4≤R L / W ≤4, R of at least 80% of the primary particles in the inner layer L / W Satisfying 0.95≤R L / W ≤2.0.

[0186] In some implementations, RMI <1.8, optionally, 1.3≤R MI <1.8, and further optionally, 1.3≤R MI ≤1.75. Without limitation, R MI It can also be any of the following values, or greater than or equal to any of the following values ​​and less than 1.8, or selected from an interval consisting of any two of the following values: 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, etc. Non-restrictively, R MI It can also be selected from any of the following ranges: 1.4≤R MI <1.8, 1.4≤R MI ≤1.75, 1.4≤R MI ≤1.6, 1.45≤R MI ≤1.55, etc.

[0187] In some implementations, R MO ≥1.8, optionally, 1.8≤R MO ≤2.3. Without limitation, R MO It can also be any of the following values, or greater than or equal to 1.8 and less than or equal to any of the following values, or selected from an interval consisting of any two of the following values: 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, etc. Non-restrictively, R... MO It can also be selected from any of the following ranges: 1.8≤R MO ≤2.2, 1.9≤R MO ≤2.1, 2.0≤R MO ≤2.1 etc.

[0188] In some embodiments, in oriented secondary particles, the outer R L / W Satisfying 1.2≤R L / W ≤4. Non-restrictively, the outer R... L / W It can be any of the following values, or a range consisting of any two of the following values: 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.5, 3, 3.0, 3.2, 3.4, 3.5, 3.6, 3.7, 3.8, 4, 4.0, etc.

[0189] In some embodiments, in oriented secondary particles, at least 80% of the primary particles in the outer layer have an R... L / W Satisfying 1.4≤R L / W ≤4. Non-limitingly, at least 80% of the primary particles in the outer layer have an R... L / WIt can be any of the following values, or a range consisting of any two of the following values: 1.4, 1.5, 1.6, 1.8, 2.0, 2.5, 3, 3.0, 3.2, 3.4, 3.5, 3.6, 3.7, 3.8, 4, 4.0, etc.

[0190] In some embodiments, in oriented secondary particles, the inner layer R L / W Satisfying 0.95≤R L / W ≤2.8. Without limitation, the inner layer's R... L / W It can be any of the following values, or a range consisting of any two of the following values: 0.95, 0.96, 0.98, 1, 1.0, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.0, 2.1, 2.2, 2.4, 2.5, 2.6, 2.8, etc.

[0191] In some embodiments, in oriented secondary particles, at least 80% of the primary particles in the inner layer have an R... L / W Satisfying 0.95≤R L / W ≤2.0. Non-limitingly, at least 80% of the primary particles in the inner layer have an R... L / W It can be any of the following values, or a range consisting of any two of the following values: 0.95, 0.96, 0.98, 1, 1.0, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.0, etc.

[0192] By controlling the inner layer R in oriented secondary particles L / W Values, Inner R L / W Mean (R) MI ), outer R L / W Values ​​and outer R L / W Mean (R) MO With the aforementioned combination, the orientation distribution of primary particles in the inner and outer layers can be better controlled, which is conducive to improving the reversible insertion and extraction efficiency of active ions in the outer primary particles, while also inhibiting electrolyte penetration, and is more conducive to achieving good cycle performance and kinetic performance.

[0193] In some embodiments, in oriented secondary particles, the R of the primary particles L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0194] By controlling the R of the primary particles in the oriented secondary particles L / WThe arrangement of particles from the center to the surface allows for better control over the orientation distribution of primary particles within the oriented secondary particles. This is beneficial for improving the active ion insertion / extraction efficiency of the outer primary particles, while also inhibiting electrolyte penetration, and further enhancing both cycling and kinetic performance.

[0195] In this application, unless otherwise specified, the anisotropy index of the angle α1 is denoted as I, based on the number of primary particles in the oriented secondary particles where the a-axis forms an angle α1 with the longitudinal direction. α1 I can be measured using the following method. α1 In a cross-section passing through the center of an oriented secondary particle, the angle α1 by which the a-axis deviates clockwise from the corresponding longitudinal direction is denoted as a positive angle, and the angle α1 by which the a-axis deviates counterclockwise from the corresponding longitudinal direction is denoted as a negative angle. α1 It is the ratio of the number of positive angles to the number of negative angles.

[0196] In some implementations, 0.4 ≤ I α1 ≤2.5.

[0197] In some implementations, 0.5 ≤ I α1 ≤2.0.

[0198] Without limitation, I α1 It can be any of the following values, or an interval selected from any two of the following values: 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1, 1.2, 1.4, 1.6, 1.7, 1.75, 1.8, 2.0, 2, 2.2, 2.4, 2.5, etc. Non-limitingly, I α1 It can be any of the following ranges: 1≤I α1 ≤2.5, 1.5≤I α1 ≤2.0, etc.

[0199] The aforementioned parameter I can be used α1 To further reflect the orientation direction distribution of primary particles forming an angle α1 in the oriented secondary particles, by using I α1 By controlling the process within the aforementioned range, the primary particles at an angle α1 can have a relatively disordered orientation, which is more conducive to suppressing the penetration of electrolyte into the grain boundaries of secondary particles and is more conducive to improving the actual specific capacity and cycle life of the positive electrode active material.

[0200] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0201] D of positive electrode active material v 50 is 8μm to 11μm, and can be selected as 9μm to 10μm;

[0202] The diameter of the primary particles in the oriented secondary particles is 100nm to 1600nm, and can be selected as 400nm to 1500nm;

[0203] The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / D v 50, where 1.1≤SPAN≤1.4; optionally, 1.2≤SPAN≤1.3.

[0204] In some embodiments, the D of the positive electrode active material v The diameter of the positive electrode active material is 8μm to 11μm, and can be selected as 9μm to 10μm. Non-limitingly, the D of the positive electrode active material... v 50 can also be any of the following values ​​or an interval selected from any two of the following values: 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, etc.

[0205] By adjusting the D of the positive electrode active material v Within the aforementioned range, the particles in the positive electrode active material can have a more suitable particle size distribution, thereby having a more suitable specific surface area. This is beneficial for both suppressing side reactions and having a shorter active ion transport distance, thus enabling the secondary battery to have both good cycle performance and kinetic performance.

[0206] In the context of this application, the volumetric cumulative distribution particle size D can be used. v N (where N represents any value selected from 0 to 100) is used to characterize the particle size of the material, referring to the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, and the particle size is less than or equal to D. v N's volume percentage is N%. D v N can be obtained from the volumetric cumulative distribution curve of the material particles. Unless otherwise specified, the volumetric cumulative distribution curve is accumulated from zero on the smaller particle size side. Let D... v 90. D v 50. D v Example 10 will be used for illustration. Unless otherwise stated in this application, D v 90 refers to the particle size corresponding to a cumulative volume distribution percentage of 90% for a material. This parameter indicates that the particle size of 90% of the material's volume is less than or equal to D. v 90, and particles accounting for 10% of the material volume have a particle size greater than D. v 90. Unless otherwise stated in this application, D v50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50% in the material. This parameter indicates that the particle size of 50% of the material's volume is less than or equal to D. v 50, and particles accounting for 50% of the material volume have a particle size greater than D. v 50. Unless otherwise stated in this application, D v 10 refers to the particle size corresponding to a cumulative volume distribution percentage of 10% for the material.

[0207] D n 10 can be obtained from the cumulative number distribution curve of the material particle size, which, unless otherwise specified, accumulates from zero on the smaller particle size side. In this application, unless otherwise specified, D n 10 refers to the particle size corresponding to a cumulative quantity distribution percentage of 10% for the material.

[0208] Those skilled in the art can understand D v 90. D v 50. D v 10 and D n The meaning of 10 can be determined using instruments and methods known in the field. For example, particle size distribution can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer or the LS-909 laser particle size analyzer from Malvern Instruments Ltd. (UK). Furthermore, for equipment models such as the Malvern 2000 laser particle size analyzer, the standard procedure GB / T19077-2016 / ISO 13320:2009 can be referenced for testing.

[0209] In some embodiments, the diameter of at least a portion of the primary particles in the oriented secondary particles is in the range of 100 nm to 1600 nm, optionally in the range of 200 nm to 1500 nm, and further optionally in the range of 400 nm to 1500 nm. Non-limitingly, the diameter of at least a portion of the primary particles in the oriented secondary particles is within a range consisting of any two of the following values: 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, etc. Non-limiting, at least a portion of the primary particles in the oriented secondary particles have diameters within any of the following ranges: 100nm–500nm, 200nm–500nm, 400nm–1600nm, 400nm–1500nm, 400nm–1400nm, 400nm–1350nm, 400nm–1200nm, 400nm–1000nm, 450nm–1600nm, 450nm–1500nm, 450nm–1400nm, 450nm–1350nm, 450nm–1200nm, 450nm–1000nm, etc.

[0210] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100 nm to 1600 nm, optionally in the range of 200 nm to 1500 nm, and further optionally in the range of 400 nm to 1500 nm. Non-limitingly, at least 80% of the primary particles in the oriented secondary particles have a diameter within a range consisting of any two of the following values: 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, etc. Non-limitingly, at least 80% of the primary particles in the oriented secondary particles have diameters within any of the following ranges: 100nm–500nm, 200nm–500nm, 400nm–1600nm, 400nm–1500nm, 400nm–1400nm, 400nm–1350nm, 400nm–1200nm, 400nm–1000nm, 450nm–1600nm, 450nm–1500nm, 450nm–1400nm, 450nm–1350nm, 450nm–1200nm, 450nm–1000nm, etc.

[0211] In some embodiments, the diameter of the primary particles in the oriented secondary particles is 100 nm to 1600 nm, optionally 200 nm to 1500 nm, and further optionally 400 nm to 1500 nm. Non-limitingly, the diameter of the primary particles in the oriented secondary particles can also be any of the following values ​​or a range selected from any two of the following values: 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, etc. Non-limitingly, the diameter of the primary particles in the oriented secondary particles can also be any of the following ranges: 100nm~500nm, 200nm~500nm, 400nm~1600nm, 400nm~1500nm, 400nm~1400nm, 400nm~1350nm, 400nm~1200nm, 400nm~1000nm, 450nm~1600nm, 450nm~1500nm, 450nm~1400nm, 450nm~1350nm, 450nm~1200nm, 450nm~1000nm, etc.

[0212] In this application, unless otherwise stated, "the diameter of the primary particle in the oriented secondary particle" refers to the maximum length of the primary particle in all directions.

[0213] In this application, without limitation, the diameter of the primary particle in the oriented secondary particle can be analyzed based on a cross-sectional view passing through the center of the oriented secondary particle. As previously mentioned, this cross-section can be obtained using ion polishing cross-sectional morphology analysis methods and can be combined with statistical analysis using microscopic morphology observation methods (such as SEM). The diameter of the primary particle can be measured based on the longest axis of the primary particle profile in the cross-sectional view passing through the center of the oriented secondary particle.

[0214] By adjusting the diameter of the primary particles in the oriented secondary particles within the aforementioned range, it is beneficial to control the proportion of active crystal faces of the primary particles, thereby further improving the lithium-ion insertion / extraction kinetics of the primary particles.

[0215] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have an L value in the range of 400 nm to 1500 nm, optionally in the range of 400 nm to 1500 nm, and further optionally in the range of 400 nm to 1400 nm. Non-limitingly, at least 80% of the primary particles in the oriented secondary particles have an L value within a range consisting of any two of the following values: 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, etc. Non-limitingly, at least 80% of the primary particles in the oriented secondary particles have an L value in any of the following ranges: 400nm–1600nm, 400nm–1500nm, 400nm–1400nm, 400nm–1350nm, 400nm–1200nm, 400nm–1000nm, 450nm–1600nm, 450nm–1500nm, 450nm–1400nm, 450nm–1350nm, 450nm–1200nm, 450nm–1000nm, etc.

[0216] In some embodiments, the L-value of the primary particles in the oriented secondary particles is in the range of 400 nm to 1500 nm, optionally in the range of 400 nm to 1500 nm, and further optionally in the range of 400 nm to 1400 nm. Non-limitingly, the L-value of the primary particles in the oriented secondary particles is within a range consisting of any two of the following values: 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, etc. Non-limitingly, the L value of the primary particles in the oriented secondary particles is within any of the following ranges: 400nm~1600nm, 400nm~1500nm, 400nm~1400nm, 400nm~1350nm, 400nm~1200nm, 400nm~1000nm, 450nm~1600nm, 450nm~1500nm, 450nm~1400nm, 450nm~1350nm, 450nm~1200nm, 450nm~1000nm, etc.

[0217] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have a W value in the range of 100 nm to 800 nm, optionally in the range of 200 nm to 700 nm, and further optionally in the range of 200 nm to 600 nm. Non-limitingly, at least 80% of the primary particles in the oriented secondary particles have a W value within a range consisting of any two of the following values: 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, etc. Without limitation, at least 80% of the primary particles in the oriented secondary particles have a W value in any of the following ranges: 100nm–700nm, 200nm–800nm, 200nm–600nm, 250nm–800nm, 250nm–700nm, 250nm–600nm, etc.

[0218] In some embodiments, the W value of the primary particles in the orientation-type secondary particles is in the range of 100nm to 800nm, optionally in the range of 200nm to 700nm, and further optionally in the range of 200nm to 600nm. Non-limitingly, the W value of the primary particles in the orientation-type secondary particles is within a range consisting of any two of the following values: 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc. Non-limitingly, the W value of the primary particles in the orientation-type secondary particles is within any of the following ranges: 100nm to 700nm, 200nm to 800nm, 200nm to 600nm, 250nm to 800nm, 250nm to 700nm, 250nm to 600nm, etc.

[0219] In some embodiments, the particle size distribution parameter SPAN of the positive electrode active material satisfies 1.1 ≤ SPAN ≤ 1.4, and optionally, 1.2 ≤ SPAN ≤ 1.3. Non-limitingly, the particle size distribution parameter SPAN of the positive electrode active material may also be any of the following values ​​or an interval selected from any two of the following values: 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, etc.

[0220] By adjusting the particle size distribution parameter SPAN of the positive electrode active material within the aforementioned range, it is beneficial to ensure that large and small particles in the positive electrode active material have appropriate volume ratios, resulting in a positive electrode active material with both high capacity and high powder compaction density, which is conducive to maximizing the volumetric energy density on the positive electrode side. By designing a combination of large and small particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material.

[0221] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0222] D of positive electrode active material v 90 satisfies: 15μm≤D v 90≤18μm, optionally, 16μm≤D v 90≤17μm;

[0223] D of positive electrode active material v 10 satisfies: 4μm≤D v 10 ≤ 6 μm, optionally, 4.5 μm ≤ D v 10≤5.5μm;

[0224] D of positive electrode active material n 10 satisfies: D n 10≥2μm.

[0225] In some embodiments, the D of the positive electrode active material v 90 satisfies: 15μm≤D v 90≤18μm, optionally, 16μm≤D v 90≤17μm. Non-limitingly, the D of the positive electrode active material... v 90 can be any of the following values ​​or a range consisting of any two of the following values: 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, etc.

[0226] By controlling the D of the positive electrode active material v Within the aforementioned range, 90% is beneficial for controlling the appropriate volume ratio of large particles in the material, which is beneficial for controlling the specific surface area and suppressing side reactions.

[0227] In some embodiments, the D of the positive electrode active material v 10 satisfies: 4μm≤D v 10 ≤ 6 μm, optionally, 4.5 μm ≤ D v 10≤5.5μm. Non-limitingly, the D of the positive electrode active material... v 10 can be any of the following values ​​or an interval selected from any two of the following values: 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc.

[0228] By controlling the D of the positive electrode active material v 10 Within the aforementioned range, it is beneficial to control the small particles in the material to have a suitable volume ratio, which is beneficial to improving the compaction density of the material.

[0229] In some embodiments, the D of the positive electrode active material n 10 satisfies: D n 10≥2μm.

[0230] By controlling the D of the positive electrode active material n 10 Within the aforementioned range, the number of small particles in the material can be controlled within a more suitable range, which is beneficial for controlling a more suitable specific surface area, thereby improving the battery's storage life.

[0231] In some embodiments, the positive electrode active material in the oriented secondary particles includes layered lithium-ion active material.

[0232] When the positive electrode active material in the oriented secondary particles includes layered lithium-ion active material, the positive electrode active material including the oriented secondary particles can be obtained by methods not limited to those exemplified in this application.

[0233] Non-limiting examples of layered lithium-ion active materials may include layered lithium transition metal oxides. Non-limiting examples of layered lithium-ion active materials may include lithium-nickel composite oxides, etc.

[0234] In some embodiments, the positive electrode active material in the oriented secondary particles includes a lithium-nickel composite oxide.

[0235] In this application, unless otherwise specified, “lithium transition metal oxide” refers to lithium-ion active materials containing transition metal elements.

[0236] In this application, unless otherwise specified, "lithium-nickel composite oxide" refers to a lithium-ion active material containing nickel. It is understood that lithium-nickel composite oxides contain at least lithium, nickel, and oxygen, and may further contain or exclude other types of transition metal elements, such as Zr, Al, and Sr. Lithium-nickel composite oxides may also contain or exclude non-metallic elements, such as B and C.

[0237] By introducing lithium-nickel composite oxide into the positive electrode active material of oriented secondary particles, the introduction of nickel element is beneficial to improving the energy density of the positive electrode active material. In addition, it is also beneficial to improve the power performance of the battery.

[0238] In this application, unless otherwise specified, the molar ratio of nickel to oxygen (O) in lithium-nickel composite oxides is denoted as Q. Ni / O .

[0239] In some implementations, in oriented secondary particles, 0.3 ≤ Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5. Non-limitingly, in oriented secondary particles, QNi / O It can be any of the following values ​​or an interval selected from any two of the following values: 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0240] In this application, unless otherwise specified, the molar ratio of nickel to lithium (Li) in lithium-nickel composite oxides is denoted as Q. Ni / Li .

[0241] In some implementations, in oriented secondary particles, 0.6 ≤ Q Ni / Li ≤1, optionally 0.8≤Q Ni / Li ≤1. Non-restrictively, in oriented secondary particles, Q Ni / Li It can be any of the following values ​​or an interval selected from any two of the following values: 0.6, 0.65, 0.66, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0242] By adjusting the molar ratio (Q) of nickel to oxygen in lithium-containing nickel composite oxides Ni / O ) and / or the molar ratio of nickel to lithium in lithium-containing nickel composite oxides (Q Ni / Li By controlling the content within the aforementioned range, the positive electrode active material can have a high nickel content, which is more conducive to improving the energy density of the positive electrode active material.

[0243] In some embodiments, the lithium-nickel composite oxide contains at least one element selected from cobalt (Co) and element M, wherein element M is at least one element selected from Mn and element Al. In some embodiments, the lithium-nickel composite oxide contains both Co and Mn. In some embodiments, the lithium-nickel composite oxide contains both Co and Al.

[0244] In some embodiments, the lithium-containing nickel composite oxide is a lithium-containing nickel-cobalt-manganese composite oxide.

[0245] In this application, unless otherwise specified, "lithium-containing nickel-cobalt-manganese composite oxide" refers to a lithium-ion active material containing nickel, cobalt, and manganese. It is understood that lithium-containing nickel-cobalt-manganese composite oxides contain at least lithium, nickel, cobalt, manganese, and oxygen, and may further contain or exclude other types of transition metal elements, such as Zr, Al, and Sr. Lithium-containing nickel composite oxides may also contain or exclude non-metallic elements, such as B and C.

[0246] In some embodiments, the lithium-nickel composite oxide contains a dopant element, Q. Ni / O<0.5, the doping element can be, but is not limited to, at least one element selected from Zr, Al, B, Sr, and Ca. In some embodiments, the doping element is selected from one or more of Zr, Al, B, Sr, and C. In some embodiments, the doping element is a combination of Zr, Al, B, Sr, and C. Q Ni / O It can be, but is not limited to, 0.3 ≤ Q. Ni / O <0.5, optionally 0.4≤Q Ni / O <0.5.

[0247] In some embodiments, at least a portion of the primary particles include a particle body and a coating layer located on at least a portion of the surface of the particle body. The particle body includes a lithium-nickel composite oxide, and the coating layer includes at least one element selected from Zr, Al, B, Sr, and Ca.

[0248] In some embodiments, a primary particle includes a particle body and a coating layer located on at least a portion of the surface of the particle body. The particle body includes a lithium-nickel composite oxide, and the coating layer may include, but is not limited to, one or more elements selected from Zr, Al, B, Sr, and Ca.

[0249] In some implementations, the oriented secondary particles satisfy one or more of the following characteristics (any numerical parameter of the following characteristics may also be selected from any suitable value or range in the context):

[0250] In oriented secondary particles, 0.3 ≤ Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5;

[0251] In oriented secondary particles, 0.6 ≤ Q Ni / Li ≤1, optionally 0.8≤Q Ni / Li ≤1;

[0252] The lithium-containing nickel composite oxide contains at least one of cobalt and M, wherein M is at least one of Mn and Al.

[0253] Lithium-nickel composite oxides contain doped elements, Q Ni / O <0.5, the doping element includes at least one element selected from Zr, Al, B, Sr and Ca;

[0254] At least a portion of the primary particles include a particle body and a coating layer located on at least a portion of the surface of the particle body. The particle body includes a lithium-nickel composite oxide, and the coating layer includes at least one element selected from Zr, Al, B, Sr, and Ca.

[0255] By Q Ni / O and / or Q Ni / LiWithin the aforementioned range, lithium-nickel composite oxides, with their high nickel content, can significantly improve the energy density of positive electrode active materials.

[0256] Introducing cobalt (Co) into lithium-nickel composite oxides helps stabilize the material structure and improves the cycle and rate performance of the positive electrode active material.

[0257] Introducing manganese (Mn) into lithium-nickel composite oxides can help reduce costs and improve the structural stability of the material.

[0258] Introducing aluminum (Al) into lithium-nickel composite oxides can improve the cycling stability of the material.

[0259] By modifying lithium-nickel composite oxides through one or more of the aforementioned doping and coating methods, it is possible to enhance the material's stability, increase its energy density, and improve its cycle life. For example, bulk doping can stabilize the structure of lithium-nickel composite oxides. For example, by depositing fast-ion conductor coatings on the surface of lithium-nickel composite oxides, the material's energy density and cycle life can be improved.

[0260] In some implementations, 0.3 ≤ Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5, and may refer to any appropriate range in the context; in oriented secondary particles, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and any of the aforementioned modified forms, wherein the modification forms include one or more of doping modification and coating modification, the doping element used for doping modification includes at least one element of Zr, Al, B, Sr and Ca, and the coating element used for coating modification includes at least one element of Zr, Al, B, Sr and Ca;

[0261] The molar ratio R of nickel and oxygen in the positive electrode active material Ni / O Satisfying 0.4≤R Ni / O ≤0.5.

[0262] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0263] D of positive electrode active material v 50 is 8μm to 11μm, and can be selected as 9μm to 10μm;

[0264] In the oriented secondary particles, at least 80% of the primary particles have a diameter of 100 nm to 1600 nm, and optionally 400 nm to 1500 nm.

[0265] The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / D v 50, where 1.1≤SPAN≤1.4, and optionally, 1.2≤SPAN≤1.3.

[0266] Oriented secondary particles can incorporate ternary cathode active materials with high nickel content and their modified forms. Modification methods can include one or more of doping and coating modifications. This allows for the production of high-energy-density, long-life ternary cathode active materials. Bulk doping can stabilize the structure of the ternary cathode active material, while coating the surface of the ternary cathode active material with fast-ion conductors can improve the material's energy density and cycle life. By controlling the included angles α1 and F1, the orientation and distribution of primary particles in the secondary particles of the cathode active material can be controlled, achieving a balance between suppressing electrolyte penetration and optimizing lithium-ion transport path distance, thereby improving the material's mass energy density and lithium-ion diffusion kinetics. Furthermore, by controlling the D... v 50. If the diameter of the primary particles in the oriented secondary particles and one or more parameters of the particle size distribution parameter SPAN of the positive electrode active material are within the aforementioned range, the aforementioned advantages can be further combined. For example, by adjusting the particle size distribution parameter SPAN of the positive electrode active material within the aforementioned range, it is beneficial to ensure that large and small particles in the positive electrode active material have appropriate volume ratios, which can further improve the powder compaction density of the material and the volumetric energy density of the positive electrode sheet. By designing a combination of large and small particles in the secondary particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material. Furthermore, doping and coating modification methods can be combined to improve the bulk structure and surface stability of the material, thereby achieving a longer cycle life.

[0267] In some embodiments, in the oriented secondary particles, the average L value of the inner layer is less than 700 nm (optionally, the average L value of the inner layer is less than 660 nm), and the average L value of the outer layer is greater than or equal to 720 nm (optionally, the average L value of the outer layer is greater than or equal to 750 nm).

[0268] In a non-limiting sense, in oriented secondary particles, the average value of L in the inner layer can be any of the following values, or less than or equal to any of the following values, or less than any of the following values: 690nm, 680nm, 670nm, 660nm, 650nm, etc.

[0269] In a non-limiting sense, in oriented secondary particles, the average value of L in the outer layer can be any of the following values, or greater than or equal to any of the following values, or greater than any of the following values: 720nm, 730nm, 740nm, 750nm, 760nm, 770nm, 780nm, etc.

[0270] In some embodiments, in the oriented secondary particles, the average L value of the inner layer is less than 660 nm, and the average L value of the outer layer is greater than or equal to 750 nm.

[0271] For positive electrode active materials in oriented secondary particles, including positive electrode active materials containing lithium nickel composite oxides, by controlling the average L value of the inner and outer layers in the oriented secondary particles within the aforementioned range, the outer layer can have a faster active ion insertion / extraction efficiency, and the inner layer can have a larger angle to better suppress electrolyte penetration into the grain boundary, which is more conducive to comprehensively improving the actual energy density, cycle performance and kinetic performance of the battery.

[0272] Unless otherwise stated in this application, "secondary battery" includes individual battery cells.

[0273] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy. Typically, a cell battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the electrodes while allowing ions to pass through.

[0274] In some embodiments, the secondary battery also includes a negative electrode, a separator, and an electrolyte, with the separator located between the positive and negative electrodes.

[0275] In some implementations, the secondary battery is a lithium-ion secondary battery.

[0276] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt.

[0277] The following are some other descriptions of the positive electrode sheet.

[0278] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive active material. It can be understood that the positive active material includes the aforementioned oriented secondary particles.

[0279] Positive electrode active materials include positive electrode active substances.

[0280] The positive electrode active material includes secondary particles, which are aggregated particles comprising multiple primary particles; the primary particles include the positive electrode active material.

[0281] The positive electrode active materials can be found in the description above, but are not limited to it.

[0282] Without limitation, the weight percentage of the positive electrode active material in the positive electrode active material layer may be greater than or equal to 80 wt%, and may further be greater than or equal to 90 wt%.

[0283] In some embodiments, the positive electrode active material layer may also employ layered lithium-ion active materials known in the art for use in batteries.

[0284] In some embodiments, the positive electrode active material layer may also employ lithium-nickel composite oxides known in the art for use in batteries.

[0285] As a non-limiting example, layered lithium-ion active materials may include one or more of the following materials: lithium-nickel composite oxides and their modified compounds. However, this application is not limited to these materials. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium-nickel composite oxides include, but are not limited to, one or more of lithium cobalt oxides, lithium-nickel composite oxides, lithium manganese oxides, lithium nickel-cobalt oxides, lithium manganese-cobalt oxides, lithium nickel-manganese oxides, lithium nickel-cobalt-manganese oxides, lithium nickel-cobalt-aluminum oxides, and their modified compounds. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium-nickel composite oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel-cobalt-manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.80 Co 0.15 Al 0.05 O2.

[0286] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies when the battery is discharged to different states.

[0287] In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the Li content can be the initial state of the material or a non-initial state after charge-discharge cycles. When the positive electrode active material is applied to the positive electrode sheet in a battery system, the Li content in the positive electrode active material contained in the positive electrode sheet will usually change after charge-discharge cycles. The Li content can be measured in atomic molar content, but is not limited to this. Taking the wet preparation of the positive electrode sheet as an example, regarding "the Li content is the initial state of the material," the initial state of the material refers to the state before it is added to the positive electrode slurry. It is understood that new materials or substances obtained by appropriate modification based on the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive electrode active material, and non-limiting examples include coating modification.

[0288] In the exemplary description of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the atomic molar content of oxygen, and the actual O content will fluctuate. The O content can be measured using atomic molar content, but is not limited to this.

[0289] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. In the positive electrode current collector, the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. In the positive electrode current collector, the composite current collector may be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Non-limitingly, in the positive electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0290] In some embodiments, the positive electrode active material layer optionally includes a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. Typically, the binder may constitute 0–10 wt% of the weight of the positive electrode active material layer, more commonly 0–8 wt%, and even more commonly 1 wt%–5 wt%.

[0291] In some embodiments, the positive electrode active material layer optionally includes a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Typically, the weight percentage of the conductive agent in the positive electrode active material layer can be 0–10 wt%, more commonly 0–8 wt%, and even more commonly 0–5 wt%.

[0292] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry. Further, the positive electrode slurry is coated onto at least one surface of the positive current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The solvent in the positive electrode slurry can be, but is not limited to, any of the solvents described in the foregoing embodiments, for example, it can include N-methylpyrrolidone (NMP), and more specifically, NMP. The surface of the positive current collector coated with the positive electrode slurry can be a single surface of the positive current collector or both surfaces of the positive current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. Based on the coating amount on one side of the positive electrode current collector, the areal density per unit area of ​​the coating (after deducting solvent) when coating the positive electrode slurry can be 13 mg / cm³ (dry weight). 2 ~20mg / cm 2 The compaction density of the positive electrode sheet can be 3.0 g / cm³. 3 ~3.6g / cm 3 3.3g / cm³ is an option. 3 ~3.5g / cm 3 .

[0293] The term "compacted density" as used in this application has a meaning well-known in the art and is one of the reference indicators for material energy density. In this application, unless otherwise specified, the compacted density of an electrode sheet refers to the ratio of the mass of the electrode active material layer to its volume. The compacted density of a positive electrode sheet refers to the ratio of the mass of the positive active material layer to its volume, and the compacted density of a negative electrode sheet refers to the ratio of the mass of the negative active material layer to its volume.

[0294] The following is a description of the negative electrode plate.

[0295] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer including a negative active substance.

[0296] Without limitation, the weight percentage of the negative electrode active material in the negative electrode active material layer may be greater than or equal to 80 wt%, and may further be greater than or equal to 90 wt%.

[0297] As a non-limiting example, the negative electrode current collector has two surfaces that are opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0298] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. In the negative electrode current collector, the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. In the negative electrode current collector, the composite current collector may be formed by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limitingly, in the negative electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0299] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials or substances, and other conventional substances that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0300] In some embodiments, the negative electrode active material includes one or more of carbon-based materials, silicon-based materials, tin-based materials, and lithium titanate, as well as modified forms of any of the foregoing, wherein the modification forms include one or more of doping modification and coating modification. Both doping and coating modification methods can employ or refer to existing modification methods in the art, including but not limited to the selection of element types and doping amounts. Carbon-based materials may include one or more of graphite materials, soft carbon, and hard carbon. Graphite materials may include one or more of artificial graphite and natural graphite.

[0301] In some embodiments, the negative electrode active material includes carbon-based materials and silicon-based materials. Non-limitingly, the total mass of carbon-based and silicon-based materials may constitute ≥80%, optionally ≥90%, further optionally ≥95%, even more optionally ≥96%, and even more optionally 100% of the total mass of the negative electrode active material. The total mass of graphite and silicon-based materials may also constitute any of the following percentages, or greater than or equal to any of the following percentages and less than or equal to 100%, or a range selected from any two of the following percentages: 80%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definition of carbon-based material can be found above; for example, carbon-based material can be graphite material. The content of carbon-based material can also be found in any suitable embodiment within the context.

[0302] In some embodiments, the negative electrode active material includes a carbon-based material. Non-limitingly, the mass percentage of the carbon-based material in the negative electrode active material can be ≥80%, optionally ≥90%, further optionally ≥95%, even more optionally ≥96%, and even more optionally 100%. The mass percentage of the carbon-based material in the negative electrode active material can also be any of the following percentages, or greater than or equal to any of the following percentages and less than or equal to 100%, or selected from any two of the following percentage ranges: 80%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definition of carbon-based material can be found above; for example, the carbon-based material can be graphite.

[0303] In some embodiments, the negative electrode active material layer optionally includes a binder. Non-limitingly, the binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Non-limitingly, the weight percentage of the binder in the negative electrode active material layer may be 0 wt% to 20 wt%, more further 0 wt% to 10 wt%, even further 0 to 5 wt%, even further 1 wt% to 5 wt%, and even more preferably 1 wt% to 3 wt%.

[0304] In some embodiments, the negative electrode active material layer optionally includes a conductive agent. Non-limitingly, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Non-limitingly, the weight percentage of the conductive agent in the negative electrode active material layer may be 0 wt% to 15 wt%, more preferably 0 wt% to 10 wt%, and even more preferably 0 wt% to 5 wt%.

[0305] In some embodiments, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). Non-limitingly, the weight percentage of other additives in the negative electrode active material layer may be 0 wt% to 15 wt%, more preferably 0 wt% to 10 wt%, even more preferably 0 wt% to 5 wt%, and even more preferably 0 wt% to 3 wt%.

[0306] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry. Further, the negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 30wt% to 70wt%, optionally 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s, optionally 3000 mPa·s to 10000 mPa·s. Based on the coating amount on one side of the negative electrode current collector, the areal density per unit area of ​​the coating (after deducting solvent) when coating the negative electrode slurry can be 6.5 mg / cm³ (dry weight). 2 ~13mg / cm 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~2.0g / cm 3 1.0g / cm can be selected. 3 ~1.8g / cm 3 .

[0307] The electrolyte is described below as an example.

[0308] Electrolytes serve to conduct ions between the positive and negative electrodes. Unless otherwise specified, electrolytes include liquid electrolytes.

[0309] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0310] In some embodiments, the electrolyte is a non-aqueous electrolyte. A non-aqueous electrolyte may include an electrolyte salt and a solvent.

[0311] The concentration of electrolyte salts in the electrolyte solution can typically be between 0.5 mol / L and 5 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, etc., but is not limited to these values.

[0312] In some embodiments, the electrolyte salt includes an electrolyte lithium salt. Non-limitingly, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0313] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt.

[0314] In some embodiments, the solvent in the non-aqueous electrolyte may include ethylene carbonate (EC). ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), One or more of the following: fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0315] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0316] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0317] In some embodiments, the electrolyte includes a solvent comprising at least one cyclic carbonate and at least two chain carbonates.

[0318] In some embodiments, the solvent in the electrolyte comprises C in a volume ratio of 1:(0.9–1.1):(0.9–1.1). 3-6 Cyclic carbonates, C 4-10 First-chain carbonates and C 3-8The second chain carbonate, wherein the number of carbon atoms in the first chain carbonate is greater than the number of carbon atoms in the second chain carbonate.

[0319] In some embodiments, C in the electrolyte 3-6 Cyclic carbonates include ethylene carbonate, C 4-10 The first-chain carbonates include diethyl carbonate, C 3-8 Second-chain carbonates include dimethyl carbonate.

[0320] The following is an exemplary description of the separator membrane.

[0321] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0322] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0323] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0324] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0325] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0326] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0327] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0328] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 shows a square battery cell 5 as an example.

[0329] In some embodiments, referring to FIG4, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0330] In some implementations, the electrolyte injection coefficient is greater than or equal to 1.6 g / Ah.

[0331] The secondary battery can be either battery module 4 or battery pack 1.

[0332] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0333] Figure 5 shows a battery module 4 as an example. Referring to Figure 5, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0334] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0335] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the battery pack may contain one or more battery modules. Those skilled in the art can select an appropriate number based on the application and capacity of the battery pack.

[0336] Figures 6 and 7 illustrate a battery pack 1 as an example. Referring to Figures 6 and 7, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0337] In a second aspect of this application, a positive electrode active material is provided, which includes the aforementioned oriented secondary particles.

[0338] In some embodiments, the positive electrode active material includes secondary particles, which are aggregated particles comprising primary particles; the primary particles include the positive electrode active substance.

[0339] In any secondary particle, the direction from the center of the secondary particle toward the surface is denoted as the X direction; the X direction passing through the center of any primary particle is denoted as the longitudinal direction; in any primary particle, the longest axis of the primary particle is denoted as the a-axis.

[0340] Secondary particles include oriented secondary particles; in oriented secondary particles, based on the total number of primary particles in oriented secondary particles, the proportion of primary particles that form an angle α1 between the a-axis and the longitudinal direction in oriented secondary particles is denoted as F1, where 15°≤α1≤45° and F1≥60%.

[0341] The positive electrode sheet prepared using the aforementioned positive electrode active material can be used to prepare secondary batteries with high energy density, good kinetic performance, and long cycle life. By utilizing the orientation angle and the proportion of primary particles included in the oriented secondary particles in the positive electrode active material, it is possible to suppress the penetration of electrolyte into the grain boundaries of the secondary particles, which is beneficial for suppressing side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual specific capacity and cycle life of the positive electrode active material. Furthermore, it is possible to achieve a shorter active ion insertion / extraction path, which is beneficial for promoting the rapid insertion / extraction of active ions during charge and discharge, thereby improving the actual energy density of the secondary battery and enabling the secondary battery to have good kinetic performance.

[0342] In some embodiments, a positive electrode active material is provided in the secondary battery described in the first aspect of this application.

[0343] In another aspect of this application, a method for preparing a positive electrode active material is provided, which can be used to prepare the aforementioned positive electrode active material.

[0344] In some embodiments, a method for preparing a positive electrode active material is provided, comprising the following steps:

[0345] S10: Preparation of precursors; and

[0346] S20: A first mixture including a precursor and a lithium source is sintered for the first time at temperature T1 to obtain a first sintered product, and then a second mixture including the first sintered product is sintered for the second time at temperature T2 to obtain a positive electrode active material; wherein, T1>T2.

[0347] In step S10, the type of transition metal element in the precursor can be selected according to the crystal structure required for the positive electrode active material, and then a suitable metal source can be selected.

[0348] Step S10 can be performed using a co-precipitation method to prepare the precursor, but is not limited to that method.

[0349] In the aforementioned embodiment, temperature T1 is higher than temperature T2. Therefore, the temperature conditions for the first sintering can be referred to as "high temperature conditions" and the temperature conditions for the second sintering can be referred to as "low temperature conditions".

[0350] In some embodiments, the temperature T1 for the first sintering can be 700℃ to 800℃, such as 700℃, 720℃, 740℃, 750℃, 760℃, 780℃, 800℃, etc., or it can be selected from any of the aforementioned temperature ranges. Furthermore, the sintering time for the first sintering can be 15h to 30h, such as 15h, 16h, 18h, 20h, 22h, 24h, 25h, 26h, 28h, 30h, etc., or it can be selected from any of the aforementioned time ranges.

[0351] In some embodiments, the temperature T2 for the second sintering can be between 200°C and 500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc., or it can be selected from any of the aforementioned temperature ranges. Furthermore, the sintering time for the second sintering can be between 3 hours and 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., or it can be selected from any of the aforementioned durations.

[0352] After step S10, a laser particle size analyzer can be used to test and obtain the particle size and SPAN value of the precursor particles, thereby screening precursors with suitable particle size range and SPAN value for step S20.

[0353] Unless otherwise specified, at least one of the first and second sintering processes is carried out in an oxygen-containing atmosphere. In some embodiments, both the first and second sintering processes are carried out in an oxygen atmosphere.

[0354] In step S20, the molar ratio of the precursor to the lithium source, expressed as OH, can be 1:(1.03–1.07), for example, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, etc., but is not limited thereto. Considering lithium loss during the sintering process, lithium is usually added in slight excess.

[0355] In step S20, during the first sintering, the first mixture may also include a dopant to introduce dopant elements. It is understood that, under typical doping levels, the introduction of dopant elements generally does not affect the crystal structure type of the grains.

[0356] In step S20, during the second sintering, the second mixture may further include a coating agent for introducing coating elements. It is understood that the introduction of coating elements can form a coating layer on at least a portion of the surface of the particles obtained from the first sintering product.

[0357] Without limitation, based on the precursor, both doping modification and coating modification can be performed simultaneously.

[0358] Taking the positive electrode active material including lithium nickel composite oxide as an example, in some embodiments, a method for preparing the positive electrode active material is provided, including steps S10 and S20, wherein step S10 is S100 and step S20 is S200.

[0359] S100: Preparation of nickel-containing precursors.

[0360] A nickel-containing precursor can be prepared by a method comprising the following steps: Based on the elemental composition of the target chemical formula of the positive electrode active material, a metal source including a nickel source is dissolved in water according to the required type and amount to prepare a metal solution; the metal solution, complexing agent, and precipitant are mixed and subjected to a co-precipitation reaction under dispersion conditions; solid-liquid separation is performed, followed by washing and drying to obtain the nickel-containing precursor. This nickel-containing precursor is the corresponding metal hydroxide.

[0361] In step S100, by controlling the type of metal source, the grain structure and particle morphology of the cathode active material can be controlled by controlling the type of transition metal element in the nickel-containing precursor. For example, a metal source including a nickel source can be used to prepare layered lithium-ion active materials containing nickel.

[0362] In some embodiments, the lithium-containing nickel composite oxide is a lithium-containing nickel-cobalt-manganese composite oxide. In this case, the metal source may include a nickel source, a cobalt source, and a manganese source. The appropriate ratio of the nickel, cobalt, and manganese sources can be selected based on the Ni:Co:Mn molar ratio in the target chemical formula.

[0363] Typically, metal sources are used to provide transition metals in nickel-containing precursors.

[0364] Non-limitingly, the metal source can be a soluble salt of the corresponding metal. For example, in lithium-containing nickel composite oxides, a soluble nickel salt (such as nickel sulfate) can be used as the nickel source; in lithium-containing nickel-cobalt-manganese composite oxides, a soluble cobalt salt (non-limiting examples of soluble cobalt salts include cobalt sulfate) and a soluble manganese salt (non-limiting examples of soluble manganese salts include manganese sulfate) can be used as the cobalt and manganese sources, respectively. (For the preparation of LiNi...) 0.82 Co 0.12 Mn 0.06 Taking the nickel-containing O2 precursor as an example, nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 82:12:6 can be used as metal sources.

[0365] Non-limiting examples of complexing agents may include ammonia.

[0366] In some embodiments, the molar ratio of ammonia to the metal element is 1 to 2, with non-limiting examples such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc., and may also be selected from any range of two of the aforementioned values. A slightly excess of ammonia can be used to provide sufficient complexation. Adjusting the amount of ammonia can affect the orientation of the primary particles within the secondary particles and the morphology of the secondary particles.

[0367] In some embodiments, the concentration of ammonia in the coprecipitation reaction system is 0.3 mol / L to 1 mol / L, with non-limiting examples such as 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc., and may also be selected from any of the aforementioned concentration ranges.

[0368] In some embodiments, the precipitant is a basic reagent. Non-limiting examples of precipitants may include alkali metal hydroxides. Non-limiting examples of alkali metal hydroxides may include sodium hydroxide.

[0369] In some embodiments, the reaction temperature for the coprecipitation reaction can be 40°C to 60°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, etc., or can be selected from any of the aforementioned temperature ranges.

[0370] In some embodiments, the pH of the reaction system for the coprecipitation reaction can be 11.2 to 11.8, for example, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, etc., or can be selected from any of the aforementioned pH ranges. By adjusting the pH of the reaction system, the orientation of primary particles in secondary particles and the morphology of secondary particles can be affected.

[0371] In some embodiments, the reaction temperature for the coprecipitation reaction can be 40°C to 60°C, and the pH can be 11.2 to 11.8. The choice of temperature conditions can affect the primary particle growth process and may also affect the orientation behavior during the primary particle growth process.

[0372] Non-limitingly, dispersion conditions can be achieved by stirring. In some embodiments, the stirring rate is 400 rpm to 1000 rpm, and can also be 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, etc., or can be selected from any range of the aforementioned stirring rates. By adjusting the stirring speed, the orientation of primary particles in secondary particles and the morphology of secondary particles can also be affected.

[0373] After step S100, a laser particle size analyzer can be used to test and obtain the particle size and SPAN value of the nickel-containing precursor particles, thereby screening out nickel-containing precursors with suitable particle size range and SPAN value for step S200.

[0374] S200: Perform the first and second sintering processes to obtain positive electrode active materials including lithium-nickel composite oxides.

[0375] In some embodiments, S200 includes the following steps: in an oxygen-containing atmosphere, a first mixture comprising a nickel-containing precursor and a lithium source is sintered for the first time at a temperature T1 to obtain a first sintered product, and then a second mixture comprising the first sintered product is sintered for the second time at a temperature T2 to obtain a positive electrode active material comprising a lithium-nickel composite oxide; wherein, T1 is higher than T2.

[0376] In some implementations, lithium hydroxide is used as the lithium source.

[0377] In some embodiments, the molar ratio of the nickel-containing precursor to the lithium source, expressed as OH, can be 1:(1.03–1.07), for example, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, etc., but is not limited thereto. Considering lithium loss during the sintering process, lithium is typically used in slight excess.

[0378] In some embodiments, the steps of performing the first sintering and the second sintering include: first performing the first sintering at a temperature T1 to obtain a first sintered product, and then performing the second sintering at a temperature T2; where T1>T2. In this case, the first sintering can be referred to as high-temperature sintering, and the second sintering can be referred to as low-temperature sintering.

[0379] In some embodiments, after the first sintering is completed, the product is crushed, washed, and dried to obtain the first sintered product.

[0380] In some embodiments, (T2-T1)≥200℃; optionally, 200℃≤(T2-T1)≤600℃; and further optionally, 200℃≤(T2-T1)≤400℃. Non-limitingly, (T2-T1) may also be any of the following values ​​or an interval selected from any two of the following values: 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, etc.

[0381] In some implementations, the sintering time t1 for the first sintering is greater than the sintering time t2 for the second sintering, where t1>t2.

[0382] In some embodiments, T1 can be 700℃ to 800℃, such as 700℃, 720℃, 740℃, 750℃, 760℃, 780℃, 800℃, etc., or it can be selected from any of the aforementioned temperature ranges. Furthermore, the sintering time for the first sintering can be 15h to 30h, such as 15h, 16h, 18h, 20h, 22h, 24h, 25h, 26h, 28h, 30h, etc., or it can be selected from any of the aforementioned durations.

[0383] In some embodiments, T2 can be between 200°C and 500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc., or it can be selected from any of the aforementioned temperature ranges. Furthermore, the sintering time for the second sintering can be between 3 hours and 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., or it can be selected from any of the aforementioned durations.

[0384] Non-limitingly, during the first sintering, a dopant may be introduced, and a first mixture comprising a nickel-containing precursor, a lithium source, and a dopant may be sintered to achieve doping modification, introducing a dopant element into the cathode active material. Alternatively, no dopant may be introduced. The types of dopant elements can be seen in the examples in the context.

[0385] Non-limitingly, during the second sintering, a coating agent may be introduced, and a second sintering may be performed on a second mixture comprising the first sintering product and the coating agent to achieve coating modification and form a positive electrode active material with a coating layer comprising coating elements provided by the coating agent. Alternatively, no coating agent may be introduced. The types of coating elements can be seen in the examples in the context.

[0386] Without limitation, based on nickel-containing precursors, both doping modification and coating modification can be performed simultaneously.

[0387] The elemental structure and composition of the precursor and positive electrode active material can be determined using structural and elemental composition analysis methods known in the art. For example, the structure of the particles can be analyzed using methods such as ion polishing cross-sectional morphology analysis combined with scanning electron microscopy (SEM), such as analyzing the presence or absence of a coating layer. As a non-limiting example, the electrode sample can be polished using an IB-19500CP ion cross-section polisher to obtain a polished sample with a cut surface; further, the sample can be tested using a ZEISS Sigma 300 instrument. As another example, inductively coupled plasma spectrometry (ICP instrument, such as the iCAP 7400 model) can be used to analyze the types and proportions of elements to determine the chemical formula of the precursor and positive electrode active material.

[0388] The particle size and distribution in the positive electrode active material, as well as the size and orientation of the primary particles in the secondary particles, are comprehensively affected by the precursor preparation process and the sintering process. The above only describes some of the influence relationships. For example, the choice of sintering temperature can also affect the packing mode of the primary particles, and thus affect the orientation distribution of the primary particles.

[0389] The aforementioned positive electrode active materials, including oriented secondary particles, can be obtained using the aforementioned method. Taking the preparation of positive electrode active materials including lithium-nickel composite oxides as an example, the selection of transition metal elements in the metal source, the co-precipitation reaction temperature, the co-precipitation reaction pH value, the amount of complexing agent (such as ammonia), the amount of precipitant (such as sodium hydroxide), the dispersion rate (dispersion method such as stirring), and the particle size and distribution of the precursor (such as the D of the precursor) can be adjusted. v 50. One or more of the parameters, such as SPAN value, sintering method (e.g., temperature gradient design), sintering temperature, and sintering time, can adjust the growth, stacking, and orientation behavior of primary particles, thereby affecting the size and morphology of the formed secondary particles, as well as the size, orientation, and orientation distribution of primary particles within the secondary particles. The included angle α1 (the angle formed by the a-axis of the primary particle and the longitudinal direction) and F1 (the proportion of primary particles with an included angle α1 between the a-axis and the longitudinal direction in the oriented secondary particles) can be adjusted within the aforementioned ranges. See the embodiments below. Furthermore, the manner in which the included angle α1 deviates from the corresponding longitudinal direction (e.g., clockwise or counterclockwise deviation) and the anisotropy index I of the included angle α1 can also be adjusted by adjusting one or more of the aforementioned parameters. α1 The R of the primary particles can also be adjusted by adjusting one or more of the aforementioned parameters. L / W and its distribution parameters (such as R of the inner layer) L / W Mean (R) MI ), outer R L / W Mean (R) MO Characteristic parameters such as pH value and seed crystals can be used to achieve R. MI <R MO This includes R, which can achieve one-time particle size reduction. L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0390] In another aspect of this application, a positive electrode sheet is provided, which includes a positive electrode active material layer, the positive electrode active material layer including the positive electrode active material described in the second aspect of this application.

[0391] In a third aspect of this application, an electrical device is provided, comprising at least one of the secondary battery described in the first aspect of this application and the positive electrode active material described in the second aspect of this application.

[0392] In some embodiments, this application also provides an electrical device, which includes a secondary battery according to any embodiment provided in this application. The secondary battery can be the power source of the electrical device or the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices may include, for example, mobile phones, laptops, etc.; electric vehicles may include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, power tools, etc., but are not limited to these. This electrical device can also be applied to military equipment, aerospace, and other fields, and can also be applied to energy storage power systems such as hydropower, thermal power, wind power, and solar power plants.

[0393] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0394] Figure 8 shows an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0395] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0396] The following describes some embodiments of this application. The described embodiments are only a part of the embodiments of this application, and not all of them. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application and its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0397] Unless otherwise specified in the examples, the procedures described above, or those described in the literature in this field, or those described in the product instructions, shall be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, or products that can be synthesized using conventional methods from commercially available products.

[0398] In the following examples, the measurement parameters of the raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0399] In the following examples, room temperature refers to 20°C to 30°C.

[0400] The instruments used in the following test and analysis methods are non-limiting examples, and those skilled in the art can also use other types of equipment or similar methods to perform test and analysis.

[0401] Test Analysis Methods

[0402] 1. Structural and elemental analysis

[0403] The chemical formula was determined by analysis using an inductively coupled plasma spectrometer (ICP).

[0404] Test instrument: iCAP 7400.

[0405] 2. D v 50. D v 90. D v 10 and D n 10. Tests and SPAN analysis.

[0406] Testing instrument: Mastersizer 3000 laser particle size analyzer.

[0407] Method: Take a clean beaker, weigh an appropriate amount of the sample to be tested, add 20 ml of ethanol for dispersion (maintaining a light-blocking degree of 25%-30%), and sonicate at 250 W / 3 min to ensure thorough dispersion. Pour the sample into the injection tower, and it circulates with the solution to the test optical path system. Under laser beam irradiation, the particle size distribution characteristics can be determined by receiving and measuring the energy distribution of the scattered light. Refer to GB / T19077-2016 / ISO 13320:2009 standard.

[0408] Particle size distribution map was plotted based on the test data, and D was obtained from the particle size distribution map. v 50. D v 90. D v 10. SPAN = (D v 90-D v 10) / D v 50. Draw a particle size distribution map based on the test data, and obtain D from the particle size distribution map. n 10.

[0409] Some test results can be found in Table 3.

[0410] 3. Structural observation and statistical analysis of primary particles within secondary particles.

[0411] The secondary particles in the positive active material layer of the positive electrode sheet were cut using a focused ion beam electron microscope or an ion cross-section polisher to obtain a cross-sectional image that basically passes through the center of the secondary particles. The information of the primary particles in the cross-sectional image was further analyzed by combining the test image of a scanning electron microscope (SEM).

[0412] (1) Focused ion beam electron microscope (FEI Scios 2HiVac device) or ion section polisher.

[0413] The secondary particles were cut until a cross-section that essentially passed through the center of the secondary particles was exposed, and then observed using SEM.

[0414] (2) Scanning electron microscope (SEM)

[0415] Equipment: Aprio 2 SEM field emission scanning electron microscope or ZEISS Sigma 300 scanning electron microscope.

[0416] Sample preparation method: Cut a sample of appropriate size (e.g., 5mm×5mm) and paste it onto the sample stage with conductive adhesive.

[0417] The test parameters for the Apreo 2 SEM are as follows: accelerating voltage (HV) 2.00kV, detector T1, OptiPlan mode, probe current 50pA. The working distance, magnification, and horizontal field of view (HFW) can be selected according to the particle size. A test example is a cross-sectional view of an oriented secondary particle shown in Figure 2. In the test shown in Figure 2, the working distance (WD) was approximately 4.16mm, the magnification (Mag) was 6500X, and the horizontal field of view (HFW) was 19.5μm.

[0418] (3) Analysis of information on primary particles in secondary particles.

[0419] Referring to the schematic diagram in Figure 1, the parameters such as α1 of the primary particle, the direction of α1's deviation from the radial direction of the secondary particle, L, and W are measured, and F1 and R are obtained through statistical analysis. L / W R MI R MO I α1 Parameters, etc. Some analysis results can be found in Tables 2 and 3.

[0420] From the SEM test results of the cross-sectional view passing through the center of the secondary particle, the cross-sectional view showing the outer contour of the complete secondary particle profile is selected for statistical analysis of primary particle information.

[0421] Select a certain number of primary particles, N0 (N0≥12), and outline the outer periphery of the primary particle cross-section in an elliptical manner. Measure the maximum length as the test value of the "diameter of the primary particle". Denote the direction of the maximum length as the a-axis direction. Determine a straight line, line1, passing through the center of both the secondary and primary particles. The measured angle between the a-axis and line1 is denoted as α1. The distance between the two intersection points of line1 and the outer periphery of the primary particle is denoted as L. Determine a straight line, line2, perpendicular to line1. The distance between the two intersection points of line2 and the outer periphery of the primary particle is denoted as W. Then R... L / W =L / W. See Figure 1.

[0422] Using the distance R from the center of the secondary particle to its surface as a reference, the region from the center of the secondary particle (i.e., 0R) to 2 / 3R is denoted as the "inner layer"; the region from 2 / 3R to the outer periphery of the secondary particle (i.e., 1R) is denoted as the "outer layer". Based on the cross-sectional profile of the oriented secondary particle, the intersection of the longest and shortest axes in the cross-section of the oriented secondary particle is taken as the center of the oriented secondary particle.

[0423] Based on the center of a primary particle, if the center of a primary particle falls into the inner layer region, it is counted as an inner particle; if the center of a primary particle falls into the outer layer region, it is counted as an outer particle; if the center of a primary particle is at the boundary between the inner and outer layers, it is counted as an "inner layer".

[0424] Based on the R of the primary particles in the inner and outer layers L / W The statistical information can be used to calculate the R of the inner layer. L / W Mean (R) MI ) and the outer R L / W Mean (R) MO ).

[0425] The number of angles between 15°≤α1≤45° is counted and denoted as N1. Then F1=N1 / N0×100%. F1 is the proportion of primary particles that form an angle of 15°≤α1≤45° with the a-axis and the corresponding longitudinal direction in the oriented secondary particles.

[0426] The direction of α1's deviation from the radial direction of the secondary particle: When α1 deviates from the straight line L in a clockwise direction, it is marked as "+", and the count result is N1; when α1 deviates from the straight line L in a counterclockwise direction, it is marked as "-", and the count result is N2; when α1 is not within the range of 15°≤α1≤45°, it is marked as "Other". α1 =N1 / N2.

[0427] (4) The proportion of oriented secondary particles in secondary particles.

[0428] Based on a randomly selected cross-sectional image containing at least 10 secondary particles, SEM analysis of the cross-section through the center of each secondary particle determines whether it is an oriented secondary particle. If 15°≤α1≤45° and F1≥60%, it is counted as one oriented secondary particle; if α1 is not within the above range or F1<60%, it is not counted as an oriented secondary particle. Based on the counting results, the percentage of oriented secondary particles is calculated, and this value is used as the test value for "the percentage of oriented secondary particles in the total number of secondary particles, P2".

[0429] Some results can be found in Table 3.

[0430] 4. Characterization of positive electrode active materials

[0431] (1) Powder compaction density

[0432] Powder compaction density can be determined using conventional methods in this field.

[0433] Testing instruments: electronic pressure testing machine or compaction density meter.

[0434] The test method using an electronic pressure testing machine as an example: Take a certain mass m0 of powder and place it in the mold of the electronic pressure testing machine. The bottom area of ​​the mold is recorded as A0. Adjust the pressure to 4T, hold the pressure for 30s, and read the height h0 of the obtained powder block. Calculate the compaction density ρ of the powder at 4T according to the formula ρ=m0 / (A0×h0).

[0435] The test method using a compaction density meter as an example: Take a certain mass m0 of powder and place it in a compaction mold. The bottom area of ​​the mold is recorded as A0. Then place the mold on the compaction density meter, apply a pressure of 4T, hold the pressure for 30s, and record the thickness h0 of the powder block after depressurization. Calculate the powder compaction density ρ under 4T according to the formula ρ=m0 / (A0×h0).

[0436] Some results can be found in Table 3.

[0437] (2) Lithium-ion solid-phase diffusion coefficient test:

[0438] Taking the GITT method as an example, the steps for testing the lithium-ion solid-phase diffusion coefficient of the positive electrode active material are as follows:

[0439] The test temperature was 25℃. The positive electrode active material was ground into a powder microelectrode. This powder microelectrode was connected to an electrochemical workstation for coulometric titration. A pulsed current of 20 μA was used, with a titration time of 1 h and an interval of 4 h (Note: To compare the effect of pulsed current and time, parallel experiments of 10 μA for 10 min can be performed), and the GITT curve was obtained. The lithium-ion diffusion coefficient D was calculated using the following formula:

[0440] Where D is the lithium-ion diffusion coefficient; I0 ​​is the applied pulse current of 20 μA; V m dE / dx is the molar volume of the positive electrode active material; F is the Faraday constant; A is the electrode surface area; n is the lithium ion charge number, where n is 1; dE / dx is the slope of the coulometric titration curve, i.e., the slope of the open-circuit potential versus Li concentration curve at a certain concentration; dE / d(t1 / 2) is the slope of the polarization voltage versus t1 / 2 curve. For more details, please refer to: Xie et al., Solid State Ionics, 2007, 178: 1218–1224; Yang et al., Electrochimica Acta, 2012, 66: 88–93.

[0441] Some results can be found in Table 3.

[0442] 5. Battery performance test

[0443] (1) Volumetric energy density

[0444] The cell volume of the secondary battery is recorded as V0.

[0445] Capacity test: Charge at a constant current of 1 / 3C to 3.65V, then charge at a constant voltage of 3.65V to a current of 0.05C, let stand for 5 minutes, and then discharge at 1 / 3C to 2.5V to obtain the capacity C0. The voltage plateau is recorded as U.

[0446] The volumetric energy density of the battery is VED = C0 × U / V0.

[0447] Some results can be found in Table 3.

[0448] (2) Cyclic performance test

[0449] At 25°C, the battery under test is charged at a constant current of 1C to a voltage of 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C, left to rest for 5 minutes, and then discharged at a constant current of 1C to a voltage of 2.8V. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity C of the battery after the nth cycle is recorded. n Then, the battery capacity retention rate P after the nth cycle n =C n / C0×100%. Continue cycling until the cell capacity retention rate decays to 80%.

[0450] The battery capacity retention rate after 900 cycles can be found in Table 3.

[0451] Example 1.

[0452] 1. Preparation of positive electrode active materials

[0453] Preparation of nickel-containing precursors: Based on the target chemical formula (LiNi) 0.82 Co 0.12 Mn 0.06 A metal solution with a Ni:Co:Mn molar ratio of 82:12:6 was prepared by dissolving nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in deionized water. The metal solution, ammonia water (a complexing agent), and sodium hydroxide solution (a precipitant) were then pumped into a reactor for co-precipitation. The entire reaction was protected by an inert gas (nitrogen). The reaction system temperature was 40℃–60℃, the pH was 11.2–11.8, the molar ratio of ammonia to the metal element was 1–2, and the stirring speed was 400 rpm–1000 rpm. After the reaction, the precursor, a metal hydroxide, was obtained through washing and drying.

[0454] Preparation of lithium-nickel composite oxide cathode active material by sintering nickel-containing precursor: The prepared nickel-containing precursor and lithium hydroxide source are mixed evenly, and oxygen (O2) is introduced for the first sintering under high temperature conditions. The high temperature sintering temperature is 700℃~800℃ (T1), and the sintering time is 15h~30h (t1). After crushing, washing and drying, the obtained material is used to obtain the first sintered product. The first sintered product is then subjected to a low temperature second sintering at a temperature of 200℃~500℃ (T2) and a sintering time of 3h~8h (t2) to obtain the ternary cathode active material.

[0455] In this example, the co-precipitation reaction temperature was 50℃, the pH was controlled at 11.5±0.2, the molar ratio of ammonia to metal element was 1.2, the stirring speed was 600rpm, the nickel-containing precursor and lithium source lithium hydroxide were mixed at a molar ratio of 1:1.05 (calculated as OH), the high-temperature sintering temperature (T1) was 780℃, the high-temperature sintering time (t1) was 20h, the low-temperature sintering temperature (T2) was 400℃, and the high-temperature sintering time (t2) was 4h.

[0456] 2. Preparation of secondary batteries

[0457] (1) Preparation of positive electrode sheet

[0458] The aforementioned prepared positive electrode active material, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.44:1.56:1 and then added to the solvent N-methylpyrrolidone to obtain a positive electrode slurry. The positive electrode slurry was coated onto both surfaces of an aluminum foil and dried in a vacuum oven at 100℃~120℃ for 8h~10h. After cold pressing and cutting, the positive electrode sheet was obtained. The coating surface density on one side was 0.25g / (1540.25mm²). 2 (), approximately 16.23 mg / cm³ 2 .

[0459] (2) Preparation of negative electrode sheet

[0460] Graphite, polystyrene-butadiene rubber, conductive carbon, and sodium carboxymethyl cellulose were added to deionized water in a mass ratio of 96.5:1.8:0.7:1 and mixed thoroughly to obtain a negative electrode slurry. This slurry was then coated onto both surfaces of a copper foil, dried in a drying oven, and subsequently cold-pressed and slit to obtain the negative electrode sheet. The surface density of the coating on one side was 0.16 g / (1540.25 mm²). 2 (), approximately 10.39 mg / cm³ 2 .

[0461] (3) Separating membrane

[0462] Choose a standard polypropylene film (PP film).

[0463] (4) Electrolyte

[0464] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was dissolved in the mixed solvent to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0465] (5) Assemble the secondary battery

[0466] The electrodes are arranged in the order of "separator - negative electrode sheet - separator - positive electrode sheet". One end of the positive electrode sheet, negative electrode sheet, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode sheet, negative electrode sheet, and two separators to obtain a wound cell (wound electrode assembly).

[0467] The electrode assembly is installed in an aluminum shell, baked at 80°C to remove water, then injected with electrolyte and sealed. The secondary battery is obtained by sequentially going through processes such as settling, hot and cold pressing, formation, shaping, and capacity testing.

[0468] Examples 2-5. Positive electrode active materials and secondary batteries were prepared using essentially the same method as in Example 1. The difference lies in adjusting the steps for preparing the positive electrode active material, mainly by adjusting one or more of the following parameters: pH of the coprecipitation reaction system in the precursor preparation step, concentration of the complexing agent ammonia (the amount of sodium hydroxide can be adjusted accordingly to control the pH within the range of 11.2–11.8), reaction temperature and reaction time of the coprecipitation reaction, and stirring rate; and sintering temperature T1 and sintering time t1, sintering temperature T2 and sintering time t2 in the precursor sintering step. The main adjustment parameters can be referred to Table 1. Parameters not mentioned in Table 1 can be appropriately adjusted based on the preceding description.

[0469] Example 6. A positive electrode active material and a secondary battery were prepared using essentially the same method as in Example 1. The difference lies in the preparation of the nickel-containing precursor in the step of preparing the positive electrode active material, based on LiNi... 0.6 Co 0.2 Mn 0.2 O2 adjusts the molar ratio of nickel, cobalt, and manganese sources to 6:2:2.

[0470] Comparative Example 1.

[0471] The positive electrode active material and the secondary battery were prepared using essentially the same method as in Example 1. The difference lies in the steps for preparing the positive electrode active material. Specifically, in the precursor preparation step, the pH was 11.0 ± 0.2, the molar ratio of ammonia to metal was 1.0, the stirring rate was 500 rpm, and the sintering temperature T1 in the precursor sintering step was 750 °C.

[0472] This comparative example yielded a positive electrode active material with a low F1; F1 is the proportion of primary particles with an angle of 15°≤α1≤45° between the a-axis and the corresponding longitudinal direction in the oriented secondary particles.

[0473] Comparative Example 2.

[0474] The positive electrode active material and the secondary battery were prepared using essentially the same method as in Example 1. The difference lies in the steps for preparing the positive electrode active material. In the precursor preparation step, the co-precipitation reaction temperature was 55°C, the pH was 11.2 ± 0.2, the molar ratio of ammonia to metal element was 1.1, and the stirring rate was 450 rpm. A second sintering was performed first, followed by a first sintering.

[0475] Preparation of lithium-nickel composite oxide positive electrode active material: The nickel-containing precursor was sintered at 450℃ for 8 hours. After crushing, washing and drying, it was mixed evenly with lithium source lithium hydroxide and sintered at 720℃ for 18 hours.

[0476] This comparative example yielded a positive electrode active material with a small α1 value in most of the primary particles in the secondary particles. According to the statistical results, α1 is less than 10°, which means that there are basically no oriented secondary particles.

[0477] The parameters for preparing the positive electrode active materials in Examples 2-6 and Comparative Examples 1-2 can also be found in Table 1.

[0478] Table 1.

[0479] Test analysis results:

[0480] Examples 1-6 show the preparation of positive electrode active materials using lithium-containing nickel oxide as an example. According to the elemental analysis results, the elemental composition of the positive electrode active materials is basically consistent with the target chemical formula.

[0481] The positive electrode active materials prepared in Examples 1-6 above all satisfy the following characteristics:

[0482] (1) There are oriented secondary particles with 15°≤α1≤45° and F1≥60%. In some embodiments, the oriented secondary particles satisfy F1≥70%, and in some embodiments, F1 exceeds 80%.

[0483] (2) The proportion of oriented secondary particles in the secondary particles of the positive electrode active material is P2≥75% (satisfying P2≥70% and P2≥60% at the same time). In most embodiments, P2≥80% is satisfied, and further P2≥90% is satisfied. In some embodiments, P2 exceeds 95%.

[0484] (3) According to the statistical results, R in oriented secondary particles L / W All satisfy R L / W ≤4, and all are within 0.95≤R L / W In the range of ≤4, R L / W The average values ​​are all in the range of 1.5 to 2.5, and in some embodiments R L / W The average value is in the range of 1.5 to 2.0;

[0485] (4) According to the statistical results, all satisfy R MI <R MO That is, the inner R L / W The average value is lower than that of the outer layer's R. L / W Average value; each embodiment satisfies R MI <1.8 and R MO ≥1.8, most embodiments satisfy 1.3≤R MI <1.8 and 1.8≤R MO ≤2.3; Each embodiment satisfies the outer layer R L / W Within the range of 1.2 to 4 and the inner layer R L / W In 0.95≤R L / W Within the range of ≤2.8; most embodiments satisfy the requirement that at least 80% of the primary particles in the outer layer have an R... L / W R in the range of 1.4 to 4 and at least 80% of the primary particles in the inner layer L / W Within the range of 0.95 to 2.0;

[0486] (5) According to the statistical results, the anisotropy index of the included angle α1 satisfies 0.4≤I α1 ≤2.5, most embodiments satisfy 0.5≤I α1 ≤2.0;

[0487] (6) D of positive electrode active material v50 has a diameter of 8μm to 11μm, and at least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100nm to 1600nm. The positive electrode active material satisfies 1.1≤SPAN≤1.4; some embodiments satisfy the D of the positive electrode active material. v 50 is 9μm~11μm, and at least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 400nm~1500nm. The positive electrode active material is 1.2≤SPAN≤1.3.

[0488] (7) According to the statistical results, the positive electrode active material satisfies 15μm≤D v 90≤18μm, 4μm≤D v 10≤6μm, D n 10 ≥ 2 μm; some embodiments further satisfy 16 μm ≤ D v 90≤17μm, 4.5μm≤D v 10≤5.5μm.

[0489] Taking Example 1 as an example, based on Figure 2, the statistical results of the L value, W index, and α1 deviation from the corresponding longitudinal direction of the primary particles in the inner and outer layers of one of the oriented secondary particles are shown in Table 2. The following information can be obtained: R L / W All are in the range of 0.95 to 4, R L / W The average value is 1.86, R MI It is 1.51 μm, R MO It is 2.05 μm, which satisfies R MI <R MO ;R in the outer layer L / W The proportion of primary particles in the range of 1.4 to 4 is approximately 81%, and the inner layer contains R... L / W Primary particles in the range of 0.95 to 2.0 account for approximately 83% of the total.

[0490] The average L value of the inner layer is less than 700 nm, the average L value of the outer layer is 783.5 nm (satisfying greater than or equal to 720 nm and also greater than or equal to 750 nm), and the average L value of the inner layer is 649.4 nm (satisfying less than or equal to 700 nm and also less than or equal to 660 nm). α1 It is approximately 1.75.

[0491] Table 2.

[0492] In Table 2, “α1 deviates from the corresponding longitudinal direction column”, “+” corresponds to the clockwise direction, “-” corresponds to the counterclockwise direction, and “other” indicates that the included angle is not within the range of 15° to 45°.

[0493] The positive electrode active materials prepared in Examples 1-6 all have high compaction densities, as shown in Table 3.

[0494] The lithium-ion solid-phase diffusion coefficients (25℃) of the positive electrode active materials prepared in Examples 1-6 are all within 1×10⁻⁶. -9 cm 2 ·s -1 Up to 8×10 -9 cm 2 ·s -1 Within the range, of which 2.5 × 10 in Example 1. -9 cm 2 ·s -1 Comparative Example 1 and Comparative Example 2 are both at 1×10 -9 cm 2 ·s -1 The following is an example, where the value in Comparative Example 1 is 5.2 × 10⁻⁶ -10 cm 2 ·s -1 In Comparative Example 2, it is 1.8 × 10⁻⁶. -10 cm 2 ·s -1 Please refer to Table 3.

[0495] The secondary batteries prepared in Examples 1-6 all exhibit high energy density, good kinetic performance, and long cycle life.

[0496] In the positive electrode active material prepared in Comparative Example 1, F1 was relatively low; in the positive electrode active material prepared in Comparative Example 2, almost no oriented secondary particles were present, and the α1 values ​​were all less than 10° according to the test results, indicating that the primary particles were mainly distributed radially along the secondary particles. The kinetic performance, energy density, and cycle performance of the secondary batteries prepared in Comparative Example 1 and Comparative Example 2 all showed varying degrees of decline.

[0497] Table 3 summarizes some of the test analysis results from some embodiments.

[0498] Table 3.

[0499] In Table 3, the compaction density of powder at 4T was tested using an electronic pressure testing machine.

[0500] The descriptions of the various implementation methods and embodiments above tend to emphasize the differences between them. Similarities or resemblances can be referenced interchangeably, and for the sake of brevity, they will not be repeated here. The technical features of the implementation methods and embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combinations of these technical features do not contradict each other, they should be considered within the scope of this specification.

[0501] It should be noted that this application is not limited to the above-described embodiments and examples. The above-described embodiments and examples are merely examples, and any embodiments and examples that have the same structure and achieve the same effect as the technical concept within the scope of this application are included in the technical scope of this application. The embodiments and examples described above only illustrate several embodiments and examples of this application, and although the descriptions are relatively detailed, they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments or examples, and other ways of constructing embodiments or examples by combining some of the constituent elements of the embodiments or examples, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A secondary battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising secondary particles, the secondary particles being an aggregate comprising a plurality of primary particles; the primary particles comprising a positive electrode active substance; In any of the secondary particles, the direction from the center of the secondary particle toward the surface is denoted as the X direction; the X direction passing through the center of any of the primary particles is denoted as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is denoted as the a-axis. The secondary particles include oriented secondary particles; in the oriented secondary particles, based on the total number of primary particles in the oriented secondary particles, the proportion of primary particles whose a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles is denoted as F1, where... 15°≤α1≤45°，F1≥60％。 2. The secondary battery according to claim 1, wherein, The included angle α1 is obtained as follows: in the cross section passing through the center of the orientation secondary particle, the direction from the center of the orientation secondary particle toward the surface of the orientation secondary particle is taken as the X direction; the X direction passing through the center of the cross section of the primary particle is taken as the longitudinal direction corresponding to the primary particle; the longest axis in the cross section of the primary particle is denoted as the a axis; the included angle α1 is obtained according to the angle formed by the a axis and the corresponding longitudinal direction.

3. The secondary battery according to claim 1 or 2, wherein, F1≥64％。 4. The secondary battery according to any one of claims 1 to 3, wherein, Let P2 be the proportion of the oriented secondary particles in the total secondary particles, and let P2 ≥ 60%.

5. The secondary battery according to claim 4, wherein, P2≥75％。 6. The secondary battery according to any one of claims 1 to 5, wherein, Let L be the length of the primary particle along the longitudinal direction, and W be the length of the primary particle in the direction perpendicular to the longitudinal direction. Let R be the ratio of L to W in the primary particle. L / W ; In the oriented secondary particles, the R of the primary particles L / W Less than or equal to 4.

7. The secondary battery according to claim 6, wherein, The L value, the W value, and the R value L / W The value is obtained as follows: In a cross-section passing through the center of the oriented secondary particle, the direction from the center of the oriented secondary particle toward the surface of the oriented secondary particle is taken as the X direction; the X direction passing through the center of the cross-section of the primary particle is taken as the longitudinal direction corresponding to that primary particle; the L value is obtained based on the length value of the primary particle along the corresponding longitudinal direction; the W value is obtained based on the length value of the primary particle along the direction perpendicular to the corresponding longitudinal direction; and the R value is obtained based on the ratio obtained by dividing the L value by the W value. L / W value.

8. The secondary battery according to claim 6 or 7, wherein, The positive electrode active material satisfies at least one of the following characteristics: In the oriented secondary particles, the R of the primary particles L / W Satisfy 0 <R L / W ≤4; In the oriented secondary particles, the R of the primary particles L / W The average value is 1.5 to 2.

5.

9. The secondary battery according to any one of claims 6 to 8, wherein, The positive electrode active material satisfies at least one of the following characteristics: In the oriented secondary particles, the R of the primary particles L / W Satisfying 0.95≤R L / W ≤4; In the oriented secondary particles, the R of the primary particles L / W The average value is 1.5 to 2.

0.

10. The secondary battery according to any one of claims 6 to 9, wherein, The distance from the center to the surface of the oriented secondary particle is denoted as R; the portion from the center of the oriented secondary particle to a position 2 / 3R from the center is denoted as the inner layer, and the portion from a position 2 / 3R from the center to the surface of the oriented secondary particle is denoted as the outer layer. In the oriented secondary particles, the inner layer R L / W The average value is denoted as R. MI The outer R L / W The average value is denoted as R. MO , where R MI <R MO .

11. The secondary battery according to claim 10, wherein, The positive electrode active material satisfies one or more of the following characteristics: In the oriented secondary particles, R MI <1.8, R MO ≥1.8; In the oriented secondary particles, the outer layer R L / W Satisfying 1.2≤R L / W ≤4, the inner layer R L / W Satisfying 0.95≤R L / W ≤2.

8.

12. The secondary battery according to claim 10 or 11, wherein, The positive electrode active material satisfies one or more of the following characteristics: In the oriented secondary particles, 1.3 ≤ R MI <1.8, 1.8≤R MO ≤2.3; In the oriented secondary particles, at least 80% of the primary particles in the outer layer have an R... L / W Satisfying 1.4≤R L / W ≤4, R of at least 80% of the primary particles in the inner layer L / W Satisfying 0.95≤R L / W ≤2.

0.

13. The secondary battery according to any one of claims 6 to 12, wherein, In the oriented secondary particles, the R of the primary particles L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

14. The secondary battery according to any one of claims 1 to 13, wherein, The anisotropy index of the angle α1 is denoted as I, based on the number of primary particles in the oriented secondary particles whose a-axis forms an angle α1 with the longitudinal direction. α1 Then 0.4≤I α1 ≤2.5; In the cross-section passing through the center of the oriented secondary particle, the angle α1 by which the a-axis deviates clockwise from the corresponding longitudinal direction is denoted as a positive angle, and the angle α1 by which the a-axis deviates counterclockwise from the corresponding longitudinal direction is denoted as a negative angle. α1 It is the ratio of the number of positive angles to the number of negative angles.

15. The secondary battery according to claim 14, wherein, 0.5≤I α1 ≤2.0。 16. The secondary battery according to any one of claims 1 to 14, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 8μm to 11μm; At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100 nm to 1600 nm, wherein the diameter of the primary particle refers to the maximum length of the primary particle in each direction. The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / D v 50, where 1.1≤SPAN≤1.

4.

17. The secondary battery according to claim 16, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 9μm to 11μm; At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 400 nm to 1500 nm. The SPAN of the positive electrode active material satisfies: 1.2≤SPAN≤1.

3.

18. The secondary battery according to any one of claims 1 to 17, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 90 satisfies: 15μm≤D v 90≤18μm; The positive electrode active material D v 10 satisfies: 4μm≤D v 10≤6μm; The positive electrode active material D n 10 satisfies: D n 10≥2μm.

19. The secondary battery according to claim 18, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 90 satisfies: 16μm≤D v 90≤17μm; The positive electrode active material D v 10 satisfies: 4.5μm≤D v 10≤5.5μm.

20. The secondary battery according to any one of claims 1 to 19, wherein, In the oriented secondary particles, the positive electrode active material includes layered lithium-ion active material.

21. The secondary battery according to any one of claims 1 to 20, wherein, In the oriented secondary particles, the positive electrode active material includes a lithium-nickel composite oxide.

22. The secondary battery according to claim 21, wherein, The molar ratio of nickel to oxygen in the lithium-nickel composite oxide is denoted as Q. Ni / O Where 0.3≤Q Ni / O ≤0.

5.

23. The secondary battery according to claim 21 or 22, wherein, The oriented secondary particles satisfy one or more of the following characteristics: In the oriented secondary particles, 0.4 ≤ Q Ni / O ≤0.5; The lithium-containing nickel composite oxide contains at least one of Co and M, wherein the M element is at least one of Mn and Al. The lithium-nickel composite oxide contains a doping element, Q. Ni / O <0.5, wherein the doping element includes at least one element selected from Zr, Al, B, Sr and Ca; At least a portion of the primary particles include a particle body and a coating layer located on at least a portion of the surface of the particle body, the particle body comprising a lithium-nickel composite oxide, and the coating layer comprising at least one element selected from Zr, Al, B, Sr, and Ca.

24. The secondary battery according to any one of claims 21 to 23, wherein, In the oriented secondary particles, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified forms of any of the aforementioned materials, wherein the modified forms include one or more of doping modification and coating modification, the doping element used for the doping modification includes at least one element selected from Zr, Al, B, Sr, and Ca, and the coating element used for the coating modification includes at least one element selected from Zr, Al, B, Sr, and Ca; The molar ratio R of nickel and oxygen in the positive electrode active material Ni / O Satisfying 0.4≤R Ni / O ≤0.

5.

25. The secondary battery according to claim 24, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 8μm to 11μm; At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 100 nm to 1600 nm. The particle size distribution parameter SPAN of the positive electrode active material conforms to the following formula: SPAN=(D v 90-D v 10) / D v 50, where 1.1≤SPAN≤1.

4.

26. The secondary battery according to claim 25, wherein, The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 9μm to 10μm; At least 80% of the primary particles in the oriented secondary particles have a diameter in the range of 400 nm to 1500 nm. The SPAN of the positive electrode active material satisfies: 1.2≤SPAN≤1.

3.

27. The secondary battery according to any one of claims 24 to 26, wherein, The distance from the center to the surface of the oriented secondary particle is denoted as R; the portion from the center of the oriented secondary particle to a position 2 / 3R from the center is denoted as the inner layer, and the portion from a position 2 / 3R from the center to the surface of the oriented secondary particle is denoted as the outer layer. In the oriented secondary particles, the average L value of the inner layer is less than 700 nm, and the average L value of the outer layer is greater than or equal to 720 nm. Wherein, the length value of the primary particle along the longitudinal direction is denoted as L, and the distance from the center to the surface of the oriented secondary particle is denoted as R; the portion from the center of the oriented secondary particle to a position 2 / 3R away from the center is denoted as the inner layer, and the portion from a position 2 / 3R away from the center to the surface of the oriented secondary particle is denoted as the outer layer.

28. The secondary battery according to claim 27, wherein, In the oriented secondary particles, the average L value of the inner layer is less than or equal to 660 nm, and the average L value of the outer layer is greater than or equal to 750 nm.

29. The secondary battery according to any one of claims 1 to 28, wherein, The secondary battery also includes a negative electrode, a separator, and an electrolyte, with the separator located between the positive electrode and the negative electrode.

30. The secondary battery according to any one of claims 1 to 29, wherein, The secondary battery is a lithium-ion secondary battery.

31. A positive electrode active material, wherein, The positive electrode active material includes secondary particles, which are aggregates of multiple primary particles; the primary particles include positive electrode active substances. In any one of the primary particles, the longest axis of the primary particle is denoted as the a-axis; in any one of the secondary particles, the direction from the center of the secondary particle toward the surface is denoted as the X-direction; the X-direction passing through the center of any one of the primary particles is denoted as the longitudinal direction; The secondary particles include oriented secondary particles; in the oriented secondary particles, based on the total number of primary particles in the oriented secondary particles, the proportion of primary particles in the oriented secondary particles that form an angle α1 between the a-axis and the longitudinal direction is denoted as F1, where 15°≤α1≤45°, F1≥60%.

32. The positive electrode active material according to claim 31, wherein it is the positive electrode active material in the secondary battery according to any one of claims 2 to 28.

33. An electrical device comprising at least one of the secondary battery as described in any one of claims 1 to 30 and the positive electrode active material as described in claim 31 or 32.

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