Secondary battery, positive electrode active material and power-consuming device

Abstract

The present application relates to a secondary battery, a positive electrode active material, and an electrical device. The secondary battery includes a positive electrode plate, which includes a positive electrode active material. The positive electrode active material includes secondary particles, which are agglomerated particles including multiple primary particles. The primary particles include a positive electrode active material. In any secondary particle, the direction from the center of the secondary particle toward the surface is recorded as the X direction. The X direction passing through the center of any primary particle is recorded as the longitudinal direction. In any primary particle, the longest axis of the primary particle is recorded as the a-axis. The secondary particles include oriented secondary particles. In the oriented secondary particles, the proportion of primary particles in the oriented secondary particles whose a-axis forms an angle α1 with the longitudinal direction is recorded as F1, based on the total number of primary particles in the oriented secondary particles, with 15°≤α1≤45° and F1≥60%. The secondary battery has high energy density, good dynamic performance, and long cycle life.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and further to a secondary battery, a positive electrode active material, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, with the advancement of secondary battery technology, lithium-ion batteries, a leading example, have been widely used in a variety of fields, including power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. They are also widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants. Lithium-ion batteries play a key role in new energy vehicles. To meet the demands for longer driving range, improved dynamic performance, and longer service life for new energy vehicles, it is necessary to comprehensively improve the energy density, dynamic performance, and cycle life of lithium-ion batteries. Summary of the Invention

[0004] In view of the above problems, the present application provides a secondary battery, a positive electrode active material and an electrical device. The secondary battery has high energy density, good kinetic performance and long cycle life.

[0005] In a first aspect, the present application provides a secondary battery comprising a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material, wherein the positive electrode active material comprises secondary particles, wherein the secondary particles are aggregates comprising a plurality of primary particles; and wherein the primary particles comprise a positive electrode active material.

[0006] In any of the secondary particles, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any of the primary particles is recorded as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is recorded as the a-axis;

[0007] 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 recorded as F1, wherein 15°≤α1≤45°, and F1≥60%.

[0008] The positive electrode active material includes oriented secondary particles, each of which includes 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 the primary particles forming the aforementioned angle α1 in the oriented secondary particles to be within the aforementioned range, it is beneficial to inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, and to inhibit side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual gram capacity and cycle life of the positive electrode active material. On the other hand, by controlling the angle α1 within the aforementioned range, a shorter active ion deintercalation path can be achieved, which is beneficial for promoting the rapid deintercalation of active ions in the positive electrode active material during the charge and discharge process, thereby improving the actual energy density of the secondary battery and providing the secondary battery with good kinetic performance.

[0009] In some embodiments, the 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 the X direction; the X direction passing through the center of the cross section of the primary particle is the longitudinal direction corresponding to the primary particle; the longest axis in the cross section of the primary particle is recorded as the a-axis; and the angle α1 is obtained based on the angle formed by the a-axis and the corresponding longitudinal direction.

[0010] The parameter α1 can be statistically analyzed using a cross-sectional view passing through the center of the oriented secondary particle.

[0011] In some embodiments, F1 ≥ 64%.

[0012] By regulating the proportion (F1) of primary particles in which the a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles within the aforementioned range, on the one hand, it is beneficial to more effectively inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, thereby more effectively inhibiting the side reactions between the electrolyte and the surface of the positive electrode active material, and better improving the actual gram capacity and cycle life of the positive electrode active material; on the other hand, it is more beneficial to provide a shorter active ion deintercalation path, thereby more beneficial to improving the actual energy density and good kinetic performance of the secondary battery.

[0013] In some embodiments, the proportion of the oriented secondary particles in the secondary particles is recorded as P2, and P2 ≥ 60%.

[0014] In some embodiments, P2 ≥ 75%.

[0015] By regulating the proportion of oriented secondary particles in the secondary particles (P2) within the aforementioned range, it is beneficial to more significantly exert the comprehensive improvement effect of the oriented secondary particles on the high energy density, kinetic performance and long cycle life of secondary batteries.

[0016] In some embodiments, the length of the primary particle along the longitudinal direction is recorded as L, the length of the primary particle perpendicular to the longitudinal direction is recorded as W, and the ratio of L to W in the primary particle is recorded as R. L / W ;

[0017] In the oriented secondary particles, the R L / W Less than or equal to 4.

[0018] 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 direction and the transverse direction (the transverse direction is the direction perpendicular to the longitudinal direction) can be adjusted. L / W , further, by L / W Adjusting within the aforementioned range is beneficial for denser stacking of the primary particles in the radial direction (X direction) of the oriented secondary particles, thereby being more beneficial for improving the energy density of the battery.

[0019] In some embodiments, the L value, the W value, and the R 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 the X direction; the X direction passing through the center of the cross section of the primary particle is the longitudinal direction corresponding to the primary particle; the L value is obtained according to the length value of the primary particle along the corresponding longitudinal direction, the W value is obtained according to the length value of the primary particle along the direction perpendicular to the corresponding longitudinal direction, and the R value is obtained according to the ratio obtained by dividing the L value by the W value. L / W value.

[0020] The above parameters L, W and R can be measured using a cross-sectional view passing through the center of the oriented secondary particle. L / W Perform statistical analysis.

[0021] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics:

[0022] In the oriented secondary particles, the R L / W Satisfy 0 <R L / W ≤4;

[0023] In the oriented secondary particles, the R L / W The average value is 1.5 to 2.5.

[0024] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics:

[0025] In the oriented secondary particles, the R L / W Satisfy 0.95≤R L / W ≤4;

[0026] In the oriented secondary particles, the R L / W The average value is 1.5 to 2.0.

[0027] By adjusting the R of the primary particles in the oriented secondary particles L / W Value range and R L / W When one or two parameters in the average value are within the aforementioned range, the orientation and orientation distribution characteristics of the primary particles can be regulated, which can better balance the inhibitory effect on electrolyte penetration and the reversible deintercalation efficiency of active ions, and is conducive to better balancing high energy density, cycle performance and good kinetic performance.

[0028] In some embodiments, the distance from the center to the surface of the oriented secondary particle is recorded as R; the portion from the center of the oriented secondary particle to a position 2 / 3R from the center is recorded as the inner layer, and the portion from the position 2 / 3R from the center to the surface of the oriented secondary particle is recorded as the outer layer;

[0029] In the oriented secondary particles, the inner layer R L / W The average value is recorded as R MI , the outer layer R L / W The average value is recorded as R MO , where R MI <R MO .

[0030] In the case of the primary particles forming the aforementioned angle α1, by further controlling R MI <R MO This is beneficial for faster deintercalation of active ions located in the outer layer and outer surface of the secondary particles, and is more beneficial for improving the kinetic performance of the positive electrode active material and the battery.

[0031] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0032] In the oriented secondary particles, R MI <1.8, R MO ≥1.8;

[0033] In the oriented secondary particles, the outer layer R L / W Satisfying 1.2≤R L / W ≤4, the inner layer R L / W Satisfy 0.95≤R L / W ≤2.8.

[0034] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0035] In the oriented secondary particles, 1.3≤RMI <1.8, 1.8≤R MO ≤2.3;

[0036] In the oriented secondary particles, at least 80% of the primary particles in the outer layer have R L / W Satisfy 1.4≤R L / W ≤4, at least 80% of the primary particles in the inner layer have an R L / W Satisfy 0.95≤R L / W ≤2.0.

[0037] By controlling the inner layer R L / W Value, inner R L / W Average value (R MI ), outer layer R L / W Value and outer R L / W Average value (R MO ) has the aforementioned combination method, which can better control the orientation distribution changes of the primary particles in the inner and outer layers, which is beneficial to better improve the reversible deintercalation efficiency of the active ions of the outer primary particles, and can also take into account the inhibition of electrolyte infiltration, which is more conducive to taking into account good cycle performance and kinetic performance.

[0038] In some embodiments, in the oriented secondary particles, the R L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0039] By controlling the R L / W Increasing from the center to the surface can better control the orientation distribution changes of the primary particles in the oriented secondary particles, which is beneficial to better improve the reversible deintercalation efficiency of the active ions of the outer primary particles, and can also take into account the inhibition of electrolyte penetration, which is more conducive to taking into account good cycle performance and kinetic performance.

[0040] In some embodiments, the number of primary particles in which the a-axis of the oriented secondary particles forms an angle α1 with the longitudinal direction is counted, and the anisotropic index of the angle α1 is recorded as I α1 , then 0.4≤I α1 ≤2.5;

[0041] In the cross section passing through the center of the oriented secondary particle, the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the clockwise direction is recorded as a positive angle, and the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the counterclockwise direction is recorded as a negative angle. α1 It is the ratio of the number of positive angles to the number of negative angles.

[0042] In some embodiments, 0.5≤I α1 ≤2.0.

[0043] The aforementioned parameter I can be used α1 Further reflect the orientation direction distribution of primary particles with an angle α1 in oriented secondary particles, by α1 By controlling the angle within the aforementioned range, the primary particles forming the angle α1 can have a relatively disordered orientation, which is more conducive to inhibiting the electrolyte from penetrating into the grain boundaries of the secondary particles and is more conducive to improving the actual gram capacity and cycle life of the positive electrode active material.

[0044] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0045] The positive electrode active material D v 50 is 8μm~11μm;

[0046] The diameter of at least 80% of the primary particles in the oriented secondary particles is within the range of 100 nm to 1600 nm, wherein the diameter of the primary particles refers to the maximum length of the primary particles in each direction;

[0047] 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, among which 1.1≤SPAN≤1.4.

[0048] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0049] The positive electrode active material D v 50 is 9μm~10μm;

[0050] At least 80% of the primary particles in the oriented secondary particles have a diameter within the range of 400 nm to 1500 nm;

[0051] The SPAN of the positive electrode active material satisfies: 1.2≤SPAN≤1.3.

[0052] By adjusting the D 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, which is beneficial for suppressing side reactions and having a shorter active ion transmission distance, so that the secondary battery has both good cycle performance and kinetic performance.

[0053] By adjusting the diameter of the primary particles in the oriented secondary particles within the aforementioned range, it is beneficial to control the active crystal surface ratio of the primary particles, so that the lithium ion insertion and extraction kinetics of the primary particles are further improved.

[0054] 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 an appropriate volume ratio, respectively. This allows the positive electrode active material to have both high capacity and high powder compaction density, which helps maximize the volumetric energy density of the positive electrode. By designing a combination of large and small particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material.

[0055] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0056] The positive electrode active material D v 90 satisfies: 15μm≤D v 90≤18μm;

[0057] The positive electrode active material D v 10Satisfies: 4μm≤D v 10≤6μm;

[0058] The positive electrode active material D m 10 satisfied: D n 10≥2μm.

[0059] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0060] The positive electrode active material D v 90 satisfies: 16μm≤D v 90≤17μm;

[0061] The positive electrode active material D v 10: 4.5μm≤D v 10≤5.5μm.

[0062] By controlling the D v 90 is within the aforementioned range, which is beneficial for controlling the volume ratio of large particles in the material, controlling the specific surface area, and inhibiting side reactions.

[0063] By controlling the D v 10 Within the aforementioned range, it is beneficial to control the volume ratio of small particles in the material to be appropriate, which is beneficial to improving the compaction density of the material.

[0064] By controlling the D n10 Within the aforementioned range, the number of small particles in the material can be controlled within a more appropriate range, which is conducive to controlling a more appropriate specific surface area, thereby improving the storage life of the battery.

[0065] In some embodiments, in the aligned secondary particles, the positive electrode active material includes a layered lithium ion active material.

[0066] In some embodiments, in the aligned secondary particles, the positive electrode active material includes a lithium-containing nickel composite oxide.

[0067] By introducing lithium-nickel composite oxide into the positive electrode active material of the oriented secondary particles, the introduction of nickel element is beneficial to improving the energy density of the positive electrode active material, and is also beneficial to improving the power performance of the battery.

[0068] In some embodiments, the molar ratio of nickel to oxygen in the lithium-containing nickel composite oxide is denoted as Q. Ni / O , where 0.3≤Q Ni / O ≤0.5.

[0069] The molar ratio of nickel and oxygen in the lithium-containing nickel composite oxide (Q Ni / O ) is controlled 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.

[0070] In some embodiments, the oriented secondary particles meet one or more of the following characteristics:

[0071] In the oriented secondary particles, 0.4≤Q Ni / O ≤0.5;

[0072] The lithium-containing nickel composite oxide contains at least one of cobalt (Co) and M elements, wherein the M element is at least one of Mn and Al elements;

[0073] The lithium-containing nickel composite oxide includes a doping element, Q Ni / O <0.5, the doping element includes at least one element selected from Zr, Al, B, Sr and Ca;

[0074] 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 of Zr, Al, B, Sr and Ca.

[0075] By putting Q Ni / O When controlled within the aforementioned range, the lithium-nickel composite oxide has a high nickel content, which can significantly improve the energy density of the positive electrode active material.

[0076] Introducing cobalt (Co) into lithium-nickel composite oxides is beneficial for stabilizing the material structure and improving the cycle and rate performance of the positive electrode active material.

[0077] Introducing manganese (Mn) elements into lithium-containing nickel composite oxides is beneficial for reducing costs and improving the structural stability of the material.

[0078] Introducing aluminum (Al) elements into lithium-nickel composite oxides can help improve the cycle stability of the material.

[0079] By modifying the lithium-nickel composite oxide through one or more of the aforementioned doping and coating methods, one or more of the following aspects can be achieved: enhanced material stability, increased material energy density, and improved cycle life. For example, bulk doping can stabilize the structure of the lithium-nickel composite oxide. For example, coating the surface of the lithium-nickel composite oxide with a fast ion conductor can improve the material's energy density and cycle life.

[0080] 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 modified forms of any of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification, the doping element used for the doping modification includes at least one of Zr, Al, B, Sr, and Ca, and the coating element used for the coating modification includes at least one of Zr, Al, B, Sr, and Ca;

[0081] The molar ratio R of nickel and oxygen in the positive electrode active material is Ni / O Satisfying 0.4≤R Ni / O ≤0.5.

[0082] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0083] The positive electrode active material D v 50 is 8μm~11μm, optional is 9μm~10μm;

[0084] The diameter of at least 80% of the primary particles in the oriented secondary particles is within the range of 100 nm to 1600 nm, and can be optionally within the range of 400 nm to 1500 nm;

[0085] 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, wherein 1.1≤SPAN≤1.4, optionally, 1.2≤SPAN≤1.3.

[0086] The positive electrode active material of the oriented secondary particles can be provided with a ternary positive electrode active material with a high nickel content and its modified material. The modified form can include one or more of doping modification and coating modification, which can be used to obtain a ternary positive electrode active material with high energy density and long life. The structure of the ternary positive electrode active material can be stabilized by bulk doping, and the energy density and cycle life of the material can be improved by providing a fast ion conductor coating material on the surface of the ternary positive electrode active material. Combined with the regulation of the angle α1 and F1, the orientation and distribution of the primary particles in the secondary particles of the positive electrode active material can be regulated, and the balance between suppressing the internal penetration of the electrolyte and optimizing the distance of the lithium ion transmission path can be taken into account, thereby improving the mass energy density of the material and the lithium ion diffusion kinetics. Furthermore, by controlling the D v 50. If one or more of the primary particle diameters of the oriented secondary particles and the particle size distribution parameter SPAN of the positive electrode active material are within the aforementioned ranges, 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 proportions, further improving 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 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 material's bulk structure and surface stability, thereby achieving a longer cycle life.

[0087] 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;

[0088] Among them, the length value of the primary particle along the longitudinal direction is recorded as L, and the distance from the center to the surface of the oriented secondary particle is recorded as R; the part from the center of the oriented secondary particle to the position 2 / 3R away from the center is recorded as the inner layer, and the part from the position 2 / 3R away from the center to the surface of the oriented secondary particle is recorded as the outer layer.

[0089] 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.

[0090] For the positive electrode active material in the oriented secondary particles, including the positive electrode active material containing lithium nickel composite oxide, by controlling the L average value of the inner layer and the outer layer in the oriented secondary particles within the aforementioned range, the outer layer can have a faster reversible deintercalation efficiency of the active ions, and the inner layer can have a larger angle to better inhibit the electrolyte from penetrating the grain boundary, which is more conducive to comprehensively improving the actual energy density, cycle performance and kinetic performance of the battery.

[0091] In some embodiments, the secondary battery further includes a negative electrode sheet, a separator, and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet.

[0092] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0093] In a second aspect of the present application, a positive electrode active material is provided.

[0094] In some embodiments, the positive electrode active material includes secondary particles, wherein the secondary particles are aggregates including primary particles; the primary particles include a positive electrode active material;

[0095] In any of the secondary particles, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any of the primary particles is recorded as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is recorded as the a-axis;

[0096] 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 recorded as F1, wherein 15°≤α1≤45°, and F1≥60%.

[0097] Positive electrode sheets prepared using the aforementioned positive electrode active materials can be used to prepare secondary batteries with high energy density, good kinetic performance, and long cycle life. By utilizing the orientation angle and number ratio of the primary particles included in the oriented secondary particles in the positive electrode active material, it is possible to inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, which helps to inhibit side reactions between the electrolyte and the surface of the positive electrode active material, thereby increasing the actual gram capacity and cycle life of the positive electrode active material. Furthermore, a shorter active ion deintercalation path is achieved, which facilitates the rapid deintercalation of active ions during the charge and discharge process, thereby improving the actual energy density of the secondary battery and imparting good kinetic performance to the secondary battery.

[0098] In some embodiments, the positive electrode active material in the secondary battery described in the first aspect of the present application is provided.

[0099] In a third aspect of the present application, an electrical device is provided, which includes the secondary battery described in the first aspect of the present application and at least one of the positive electrode active materials described in the second aspect of the present application.

[0100] The details of one or more embodiments or examples of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] In order to better describe and illustrate the embodiments, examples, or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments, examples, or examples currently described, and any of the best modes currently understood for these applications. In addition, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0102] Figure 1 Schematic diagram of relevant parameters of oriented secondary particles in one embodiment of the present application, wherein only the cross section of a portion of primary particles at the two-dimensional cross section of the oriented secondary particles is shown.

[0103] Figure 2 This is the experimental result of the cross-sectional view of the oriented secondary particles in one embodiment of the present application.

[0104] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of the present application.

[0105] Figure 4 for Figure 3 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0106] Figure 5 This is a schematic diagram of a battery module according to one embodiment of the present application.

[0107] Figure 6 Schematic diagram of a battery pack according to one embodiment of the present application.

[0108] Figure 7 for Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0109] Figure 8 FIG. 1 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0110] Description of reference numerals:

[0111] 52, electrode assembly; 1, battery pack; 2, upper box; 3, lower box; 4, battery module; 5, battery cell; 51, shell; 53, cover; 6, electrical device. DETAILED DESCRIPTION

[0112] Below, some embodiments and examples of the secondary battery, positive electrode active material and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0113] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0114] In this application, references to "plurality," "multiple," "multiple," "several," and the like, unless otherwise specified, refer to a quantity greater than or equal to two. For example, "one or more" refers to one or greater than or equal to (≥, greater than or equal to) two. It is understood that references to "any number" of items refer to any suitable combination of multiple items, i.e., any combination of "any number" of items that is not conflicting and that enables the implementation of this application.

[0115] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0116] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0117] Those skilled in the art will appreciate that, in the methods of each embodiment or embodiment, the order in which each step is written does not mean a strict order of execution and constitutes any limitation to the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present application can be performed in sequence, or can be performed randomly, or can preferably be performed in sequence. For example, method M includes steps (a) and (b), indicating that method M may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For another example, method M may also include step (c), indicating that step (c) can be added to method M in any order, for example, method M may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0118] In this application, in open technical features or technical solutions described with words such as "contain," "include," and "include," unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or not. It can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3", and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0119] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0120] In this application, "optionally," "optional," and "optional" mean optional, that is, they refer to either option selected from the two parallel options of "yes" or "no." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" is independent. Unless otherwise specified, the descriptions "optionally include," "optionally include," etc. in this application, using "optionally include" as an example, mean "may include or not include."

[0121] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more relevant listed items, and also include any and all combinations of the relevant listed items, wherein the arbitrary and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. For example, "A and / or B" means a group consisting of A, B, and "a combination of A and B." Among them, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be appropriately understood according to the sentence in which it is located.

[0122] As used herein, "combination thereof", "any combination thereof", "any combination thereof" and the like include all suitable combinations of any two or more of the listed items.

[0123] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the technical solution that can implement the present application.

[0124] Herein, the terms "preferred," "better," "more preferable," "suitable," "comparatively better," and "preferable" are used solely to describe preferred implementations or examples and should not be construed as limiting the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, each "preferred" term is considered independent unless otherwise specified and there are no contradictions or mutual constraints.

[0125] In this application, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0126] In this application, the terms "first," "second," and "third," etc., in "the first aspect," "the second aspect," "the third aspect," etc., are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, "first," "second," and "third," etc., are only used for non-exhaustive enumeration and description purposes and should be understood not to constitute closed-ended limitations on quantity.

[0127] In this application, the term "room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this application, room temperature refers to 20°C to 30°C.

[0128] In this application, when referring to a data range, if the unit is followed only by the right endpoint, it means that the units of the left and right endpoints are the same. For example, "3~5h" or "3-5h" both mean that the units of the left endpoint "3" and the right endpoint "5" are both hours, and both have the same meaning as "3h~5h". Similarly, descriptions of other parameters such as temperature and size are to be understood in the same manner.

[0129] The weight or mass of the relevant components mentioned in the embodiments or examples of the present application can not only refer to the content of each component, but also represent the proportional relationship of weight or mass between each component. Therefore, as long as the content of the relevant components in accordance with the embodiments or examples of the present application is proportionally enlarged or reduced, it is within the scope described in the present application. Further, the mass involved in the embodiments or examples of the present application can be mass units known to the chemical industry such as micrograms (μg), milligrams (mg), grams (g), kilograms (kg). Unless otherwise specified, the mass ratio is equal to the corresponding weight ratio, such as the mass of substance A is m1 and the weight is W1, the mass of substance B is m2 and the weight is W2, then the mass ratio m1 / m2 of the two is numerically equal to the corresponding weight ratio W1 / W2.

[0130] In this application, unless otherwise specified, wt% represents weight percentage by weight, which is numerically equal to the corresponding mass percentage by mass.

[0131] 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 expressed as ">", and "less than" can be equivalently expressed as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be regarded as providing two solutions of "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be regarded as providing two solutions of "less than" and "equal to".

[0132] In this application, exemplary descriptions such as "in some embodiments (or examples)" and "in one embodiment (or example)" may include 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.

[0133] A common form of positive electrode active material is polycrystalline material, in which case the secondary particles are composed of multiple primary particles. Taking lithium ion active materials as an example, in the secondary particles usually obtained, the longest axis (a-axis) of the primary particle is basically consistent with the direction from the center to the surface of the secondary particle. In this case, the transmission distance of lithium ions can be shortened to improve the dynamics of lithium ion deintercalation of the positive electrode active material. However, due to the overly regular orientation of the primary particles, there are obvious through-channels between the primary particles, making it easy for the electrolyte to penetrate into the secondary particles, causing more serious interfacial side reactions, resulting in reduced cycle performance and actual gram capacity of the positive electrode active material, and thus deteriorating the cycle life of the material.

[0134] In view of this, the present application provides a secondary battery, a positive electrode active material and an electrical device. The secondary battery has high energy density, good kinetic performance and long cycle life.

[0135] In some embodiments, a secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, the positive electrode active material includes secondary particles, and the secondary particles are agglomerates including multiple primary particles; in any primary particle, the longest axis of the primary particle is recorded as the a-axis; the X direction passing through the center of any primary particle is recorded as the longitudinal direction; in any secondary particle, the direction from the center of the secondary particle toward the surface is recorded 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 whose a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles is recorded as F1, 15°≤α1≤45°, and F1≥60%.

[0136] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0137] In the present application, unless otherwise specified, the electrode plate can be a positive electrode plate or a negative electrode plate, and the "active material" in the electrode plate refers to a substance that can reversibly embed and release active ions. Unless otherwise specified, "negative electrode active material" refers to a substance used for the negative electrode plate that can reversibly embed and release active ions; "positive electrode active material" refers to a substance used for the positive electrode plate that can reversibly release and embed active ions. When the battery cell or secondary battery is charged, the active ions are released from the positive electrode and embedded in the negative electrode through the electrolyte; and when the battery cell or secondary battery is discharged, the active ions are released from the negative electrode and embedded in the positive electrode. The active ions are not particularly limited. In some embodiments, the active ions may include lithium ions. Without limitation, the active ions may be lithium ions. In this case, the battery cell is a lithium-ion battery cell and the secondary battery is a lithium-ion secondary battery.

[0138] In this application, “electrode plate” and “electrode 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.

[0139] In this application, unless otherwise specified, an "electrode active material layer" includes at least one of the positive electrode active material layer of a positive electrode sheet and the negative electrode active material layer of a negative electrode sheet. Depending on the specific circumstances, the electrode active material layer may refer to either the positive electrode active material layer or the negative electrode active material layer. It is understood that the positive electrode active material layer contains a positive electrode active substance, and the negative electrode active material layer contains a negative electrode active substance. In this application, an "electrode active material layer" may also be simply referred to as an "active material layer."

[0140] In this application, unless otherwise specified, “separator” and “diaphragm” have the same meaning and can be used interchangeably.

[0141] It can be understood that both “primary particles” and “secondary particles” are particles containing a positive electrode active material.

[0142] In this application, "primary particles" and "secondary particles" are terms well known in the art. "Primary particles" refer to single crystals or quasi-single crystal grains. "Secondary particles" refer to particles in an agglomerated state formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be easily distinguished by experimental means, for example, using scanning electron microscope (SEM) images, but are not limited thereto.

[0143] In a first aspect of the present application, a secondary battery is provided, which includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes oriented secondary particles.

[0144] In some embodiments, a secondary battery is provided, 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 agglomerated particles comprising a plurality of primary particles; the primary particles comprising a positive electrode active material;

[0145] In any secondary particle, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any primary particle is recorded as the longitudinal direction; in any primary particle, the longest axis of the primary particle is recorded as the a-axis;

[0146] 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 recorded as F1, where 15°≤α1≤45°, and F1≥60%.

[0147] In this application, unless otherwise specified, the "X direction" refers to the direction from the center of the secondary particle toward the surface. It should be understood that different locations on the secondary particle surface, directed from the center of the secondary particle, correspond to different X directions; each location on the secondary particle surface corresponds to a corresponding X direction.

[0148] In this application, unless otherwise specified, "longitudinal direction" refers to a direction passing through the center of a secondary particle and the center of a primary particle. It is understood that different primary particles correspond to different longitudinal directions, and each primary particle corresponds to its corresponding longitudinal direction.

[0149] 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. Generally, the longest axis in a two-dimensional cross-section of the primary particle can be used as the test result of the a-axis length.

[0150] In this application, unless otherwise specified, the percentage of primary particles whose a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles is recorded as F1.

[0151] In this application, unless otherwise specified, "oriented secondary particles" refer to a certain number of primary particles having 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 recorded as "α1", which can be called "angle α1". Unless otherwise specified, the proportion of primary particles whose a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles is recorded as "F1". In this application, generally, when the secondary particles satisfy 15°≤α1≤45° and F1≥60%, they are determined to be oriented secondary particles.

[0152] The positive electrode active material includes oriented secondary particles, each of which includes 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 the primary particles forming the aforementioned angle α1 in the oriented secondary particles to be within the aforementioned range, it is beneficial to inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, and to inhibit side reactions between the electrolyte and the surface of the positive electrode active material, thereby improving the actual gram capacity and cycle life of the positive electrode active material. On the other hand, by controlling the angle α1 within the aforementioned range, a shorter active ion deintercalation path can be achieved, which is beneficial for promoting the rapid deintercalation of active ions in the positive electrode active material during the charge and discharge process, thereby improving the actual energy density of the secondary battery and providing the secondary battery with good kinetic performance.

[0153] In some embodiments of the present application, the angle α1 can be obtained as follows: in a cross-section passing through the center of an oriented secondary particle, the direction from the center of the oriented secondary particle toward the surface of the oriented secondary particle is the X direction; the X direction passing through the center of the cross-section of the primary particle is the longitudinal direction corresponding to the primary particle; the longest axis in the cross-section of the primary particle is recorded as the a-axis; and the angle α1 is obtained based on the angle formed by the a-axis and the corresponding longitudinal direction.

[0154] The parameter α1 can be statistically analyzed using a cross-sectional view through the center of the oriented secondary particle. It will be appreciated that a cross-sectional view through the center of the oriented secondary particle can display the cross-section and cross-sectional profile of the oriented secondary particle, as well as the cross-section and cross-sectional profile of the primary particle. Unless otherwise specified, the center of the oriented secondary particle can be determined by determining the intersection of the longest and shortest axes of the cross-section of the oriented secondary particle based on the cross-sectional profile of the oriented secondary particle as the center of the oriented secondary particle.

[0155] The ion polishing cross-sectional morphology analysis method can be used to perform statistical analysis on the parameters related to the primary particles in the oriented secondary particles. Without limitation, the secondary particles can be cut to form a cross section that basically passes through the center of the secondary particles, and a sample with the cut surface is obtained, and further combined with the microscopic morphology observation method, the relevant parameters of the primary particles in the cross-sectional view of the secondary particles are statistically analyzed. Without limitation, instruments or equipment including but not limited to focused electron beam (FIB) electron microscope (non-limiting examples such as FEI Scios 2HiVac equipment, etc.), ion cross-sectional polisher (non-limiting examples such as IB-09010 CP argon ion cross-sectional polisher, IB-19500CP ion cross-sectional polisher, etc. of JEOL, Japan) can be used to obtain a cross section that basically passes through the center of the secondary particles. Microscopic morphology observation methods can employ instruments or equipment including, but not limited to, scanning electron microscopy (SEM) technology, and non-limitingly, a high-resolution field emission scanning electron microscope. Non-limiting examples of SEM instruments include the Sigma 300 scanning electron microscope and the Apreo 2 SEM field emission scanning electron microscope from ZEISS, Germany. In some embodiments, a cross-sectional image through the center of the secondary particle is obtained by combining ion polishing cross-sectional morphology analysis with scanning electron microscopy (SEM).

[0156] The above method can be used to analyze parameters including but not limited to the following: the a-axis of the primary particle, the angle between the a-axis of the primary particle and the corresponding longitudinal direction (angle α1), the proportion F1 of the primary particles with the a-axis and the longitudinal direction forming an angle α1, the deviation direction of the angle α1 relative to the X direction and the anisotropic index I of the angle α1 α1 , the length of the primary particle along the longitudinal direction L, the length of the primary particle perpendicular to the longitudinal direction W, the inner layer R L / W Average value (R MI ), the outer R L / W Average value (R MO ) etc. The determination of some of the above parameters can be found in Figure 1 The test and analysis method can also be used in the following examples. Figure 1 Only the cross section of a portion of the primary particles at the cross section of the oriented secondary particles is shown.

[0157] In some embodiments, the oriented secondary particles are spherical or quasi-spherical. "Quasi-spherical particles" have an aspect ratio close to 1, with non-limiting examples ranging from 0.8 to 1.2. The aspect ratio of a quasi-spherical particle refers to the ratio of its longest axis to its shortest axis. This can be measured and analyzed using methods known in the art and conventional instruments.

[0158] In some embodiments, F1 ≥ 60%, optionally F1 ≥ 64%, or any of the following percentages, or greater than or equal to any of the following percentages, or selected from the interval between any of the following percentages and 100%: 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 80%, 85%, 90%, 95%, etc. Without limitation, F1 may also be any of the following ranges: 60% to 100%, 70% to 100%, 60% to 90%, 70% to 90%, etc.

[0159] By regulating the proportion (F1) of primary particles in which the a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles within the aforementioned range, on the one hand, it is beneficial to more effectively inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, thereby more effectively inhibiting the side reactions between the electrolyte and the surface of the positive electrode active material, and better improving the actual gram capacity and cycle life of the positive electrode active material; on the other hand, it is more beneficial to provide a shorter active ion deintercalation path, thereby more beneficial to improving the actual energy density and good kinetic performance of the secondary battery.

[0160] In this application, unless otherwise specified, the proportion of oriented secondary particles in the secondary particles is recorded as P2.

[0161] In some embodiments, P2 ≥ 60%, optionally P2 ≥ 70%, further optionally P2 ≥ 75%, and may also be any of the following percentages, or be greater than or equal to any of the following percentages, or be selected from the interval consisting of any two of the following percentages, or be selected from the interval consisting of any one 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. Without limitation, P2 may also be any of the following ranges: 60% to 100%, 70% to 100%, 80% to 100%, 90% to 100%, etc.

[0162] By regulating the proportion of oriented secondary particles in the secondary particles (P2) within the aforementioned range, it is beneficial to more significantly exert the comprehensive improvement effect of the oriented secondary particles on the high energy density, kinetic performance and long cycle life of secondary batteries.

[0163] P2 can be obtained using the following method, but is not limited to this: Based on SEM analysis of a randomly selected cross-section of at least ten secondary particles through the center of the secondary particle, determine whether the particle is oriented. When 15° ≤ α1 ≤ 45° and F1 ≥ 60%, count as one oriented secondary particle. When α1 is outside this range or F1 is less than 60%, the particle is not counted as an oriented secondary particle. Based on the counting results, calculate the percentage of oriented secondary particles.

[0164] In this application, unless otherwise specified, the length of a primary particle in the longitudinal direction is recorded as L, the shortest length perpendicular to the longitudinal direction in a primary particle is recorded as W, and the ratio of L to W in a primary particle is recorded as R. L / W .

[0165] In some embodiments, in the oriented secondary particles, the R L / W Less than or equal to 4.

[0166] 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 direction and the transverse direction (the transverse direction is the direction perpendicular to the longitudinal direction) can be adjusted. L / W , further, by L / W Adjusting within the aforementioned range is beneficial for denser stacking of the primary particles in the radial direction (X direction) of the oriented secondary particles, thereby being more beneficial for improving the energy density of the battery.

[0167] In some embodiments, 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 the surface of the oriented secondary particle is the X direction; the X direction passing through the center of the cross section of the primary particle is the longitudinal direction corresponding to the primary particle; the L value is obtained according to the length value of the primary particle along the corresponding longitudinal direction, the W value is obtained according to the length value of the primary particle along the direction perpendicular to the corresponding longitudinal direction, and the R value is obtained according to the ratio obtained by dividing the L value by the W value. L / W value.

[0168] The above parameters L, W and R can be measured using a cross-sectional view passing through the center of the oriented secondary particle. L / W Perform statistical analysis.

[0169] In some embodiments, the positive electrode active material satisfies at least one of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0170] In the oriented secondary particles, the R L / W Satisfy 0 <R L / W ≤4, optionally, 0.95≤RL / W ≤4;

[0171] In oriented secondary particles, the R L / W The average value is 1.5~2.5, and can be selected as 1.5~2.0.

[0172] In some embodiments, in the oriented secondary particles, the R L / W Satisfy 0 <R L / W ≤4, optionally, 0.95≤R L / W ≤4. Without limitation, the R of primary particles L / W The average value of can also be any of the following values, or an interval 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, 3, 3.0, 3.2, 3.4, 3.5, 3.6, 3.7, 3.8, 4.0, 4, etc. For example, the R of the primary particle is 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.

[0173] In some embodiments, in the oriented secondary particles, the R L / W The average value of is 1.5 to 2.5, and can be 1.5 to 2.0. L / W The average value can also be any of the following values, or an interval selected from 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.

[0174] By adjusting the R of the primary particles in the oriented secondary particles L / W Value range and R L / W When one or two parameters in the average value are within the aforementioned range, the orientation and orientation distribution characteristics of the primary particles can be regulated, which can better balance the inhibitory effect on electrolyte penetration and the reversible deintercalation efficiency of active ions, and is conducive to better balancing high energy density, cycle performance and good kinetic performance.

[0175] In this application, unless otherwise specified, the distance from the center to the surface of the oriented secondary particle is recorded as R; the part from the center of the oriented secondary particle to the position 2 / 3R from the center is recorded as the inner layer, and the part from the position 2 / 3R from the center to the surface of the oriented secondary particle is recorded as the outer layer.

[0176] In this application, unless otherwise specified, in the oriented secondary particles, the inner layer R L / W The average value is recorded as R MI , the outer R L / W The average value is recorded as R MO .

[0177] In some embodiments, R MI <R MO .

[0178] In the case of the primary particles forming the aforementioned angle α1, by further controlling R MI <R MO This is beneficial for faster deintercalation of active ions located in the outer layer and outer surface of the secondary particles, and is more beneficial for improving the kinetic performance of the positive electrode active material and the battery.

[0179] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0180] 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);

[0181] In the oriented secondary particles, the outer layer R L / W Satisfying 1.2≤R L / W ≤4, inner layer R L / W Satisfy 0.95≤R L / W ≤2.8.

[0182] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0183] In oriented secondary particles, 1.3≤R MI <1.8, 1.8≤R MO ≤2.3;

[0184] In the oriented secondary particles, at least 80% by number of the primary particles in the outer layer have R L / W Satisfy 1.4≤R L / W ≤4, at least 80% of the primary particles in the inner layer have an R L / W Satisfy 0.95≤R L / W ≤2.0.

[0185] In some embodiments, RMI <1.8, optionally, 1.3≤R MI <1.8, 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 the 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. In a non-limiting manner, R MI You can also select 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.

[0186] In some embodiments, 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 the 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. In a non-limiting manner, R MO You can also select any of the following ranges: 1.8≤R MO ≤2.2、1.9≤R MO ≤2.1、2.0≤R MO ≤2.1, etc.

[0187] In some embodiments, in the oriented secondary particles, the outer layer R L / W Satisfy 1.2≤R L / W ≤4. Without limitation, the outer layer R L / W It can be any of the following values, or an interval 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.

[0188] In some embodiments, in the oriented secondary particles, at least 80% by number of the primary particles in the outer layer have R L / W Satisfy 1.4≤R L / W ≤4. Without limitation, at least 80% of the primary particles in the outer layer have an R L / WIt can be any of the following values, or an interval selected from 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.

[0189] In some embodiments, in the oriented secondary particles, the inner layer R L / W Satisfy 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 an interval 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, etc.

[0190] In some embodiments, in the oriented secondary particles, at least 80% by number of the primary particles in the inner layer have R L / W Satisfy 0.95≤R L / W ≤2.0. Without limitation, 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 an interval 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.

[0191] By controlling the inner layer R L / W Value, inner R L / W Average value (R MI ), outer layer R L / W Value and outer R L / W Average value (R MO ) has the aforementioned combination method, which can better control the orientation distribution changes of the primary particles in the inner and outer layers, which is beneficial to better improve the reversible deintercalation efficiency of the active ions of the outer primary particles, and can also take into account the inhibition of electrolyte infiltration, which is more conducive to taking into account good cycle performance and kinetic performance.

[0192] In some embodiments, in the oriented secondary particles, the R L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0193] By controlling the R L / WIncreasing from the center to the surface can better control the orientation distribution changes of the primary particles in the oriented secondary particles, which is beneficial to better improve the active ion deintercalation efficiency of the outer primary particles, and can also take into account the inhibition of electrolyte penetration, which is more conducive to taking into account good cycle performance and kinetic performance.

[0194] In this application, unless otherwise specified, the number of primary particles in which the a-axis of the oriented secondary particles forms an angle α1 with the longitudinal direction is counted, and the anisotropic index of the angle α1 is recorded as I α1 I can be measured as follows α1 : In the cross section passing through the center of the oriented secondary particle, the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the clockwise direction is recorded as a positive angle, and the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the counterclockwise direction is recorded as a negative angle, I α1 It is the ratio of the number of positive angles to the number of negative angles.

[0195] In some embodiments, 0.4≤I α1 ≤2.5.

[0196] In some embodiments, 0.5≤I α1 ≤2.0.

[0197] Without limitation, I α1 It can be any of the following values, or an interval consisting of 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. In a non-limiting manner, I α1 Can be any of the following ranges: 1≤I α1 ≤2.5、1.5≤I α1 ≤2.0, etc.

[0198] The aforementioned parameter I can be used α1 Further reflect the orientation direction distribution of primary particles with an angle α1 in oriented secondary particles, by α1 By controlling the angle within the aforementioned range, the primary particles forming the angle α1 can have a relatively disordered orientation, which is more conducive to inhibiting the electrolyte from penetrating into the grain boundaries of the secondary particles and is more conducive to improving the actual gram capacity and cycle life of the positive electrode active material.

[0199] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0200] D of positive electrode active material v 50 is 8μm~11μm, optional is 9μm~10μm;

[0201] The diameter of the primary particles in the oriented secondary particles is 100 nm to 1600 nm, and can be optionally 400 nm to 1500 nm;

[0202] 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, wherein 1.1≤SPAN≤1.4; optionally, 1.2≤SPAN≤1.3.

[0203] In some embodiments, the D of the positive electrode active material v 50 is 8 μm to 11 μm, and can be 9 μm to 10 μm. v 50 can also be any of the following values ​​or an interval consisting of any two of the following values: 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, etc.

[0204] By adjusting the D 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, which is beneficial for suppressing side reactions and having a shorter active ion transmission distance, so that the secondary battery has both good cycle performance and kinetic performance.

[0205] In the context of this application, the volume 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, which refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches N%. The particle size is less than or equal to D v The volume percentage of N is N%. v N can be obtained from the volume cumulative distribution curve of the material particle size. If there is no other explanation, the volume cumulative distribution curve starts from zero from the small particle size side. v 90.D v 50. D v 10 is used as an example. In this application, unless otherwise specified, D v 90 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 90%. This parameter indicates that the particle size of 90% of the material volume is less than or equal to D v 90, and the particle size of 10% of the material volume is larger than D v 90. In this application, unless otherwise stated, D v50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%. This parameter indicates that the particle size of 50% of the material volume is less than or equal to D v 50, and 50% of the volume of the material has a particle size larger than D v 50. In this application, unless otherwise specified, D v 10 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 10%.

[0206] D n 10 can be obtained from the number cumulative distribution curve of the material particle size. If there is no other explanation, the number cumulative distribution curve starts from zero from the small particle size side. In this application, if there is no other explanation, D n 10 refers to the particle size corresponding to when the cumulative number distribution percentage of the material reaches 10%.

[0207] Those skilled in the art will understand that v 90.D v 50. D v 10 and D n 10, and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E Laser Particle Size Analyzer or the LS-909 Laser Particle Size Analyzer (Omega), manufactured by Malvern Instruments Ltd., UK, with reference to GB / T 19077-2016 Particle Size Distribution by Laser Diffraction Method. Furthermore, for equipment such as the Malvern 2000 Laser Particle Size Analyzer, testing can be performed in accordance with the standard procedures GB / T 19077-2016 / ISO 13320:2009.

[0208] In some embodiments, the diameter of at least a portion of the primary particles in the oriented secondary particles is within a range of 100 nm to 1600 nm, optionally within a range of 200 nm to 1500 nm, and further optionally within a range of 400 nm to 1500 nm. Without limitation, 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, and the like. Without limitation, the diameter of at least a portion of the primary particles in the oriented secondary particles is within any of the following ranges: 100nm to 500nm, 200nm to 500nm, 400nm to 1600nm, 400nm to 1500nm, 400nm to 1400nm, 400nm to 1350nm, 400nm to 1200nm, 400nm to 1000nm, 450nm to 1600nm, 450nm to 1500nm, 450nm to 1400nm, 450nm to 1350nm, 450nm to 1200nm, 450nm to 1000nm, etc.

[0209] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have a diameter within a range of 100 nm to 1600 nm, optionally within a range of 200 nm to 1500 nm, and further optionally within a range of 400 nm to 1500 nm. Without limitation, 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, and the like. Without limitation, the diameter of at least 80% of the primary particles in the oriented secondary particles is 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, 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. Without limitation, the diameter of the primary particles in the oriented secondary particles may also be any of the following values ​​or an interval 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. Without limitation, 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.

[0211] In the present application, unless otherwise specified, the “diameter of a primary particle in an oriented secondary particle” refers to the maximum length of the primary particle in each direction.

[0212] In the present application, without limitation, the diameter of the primary particles in the oriented secondary particles can be analyzed based on a cross-sectional view passing through the center of the oriented secondary particles. As previously mentioned, the cross-section can be obtained using an ion polishing cross-sectional morphology analysis method and can be statistically analyzed in combination with a microscopic morphology observation method (such as SEM). The diameter of the primary particle can be measured based on the longest axis in the cross section of the primary particle in the cross-sectional view passing through the center of the oriented secondary particle.

[0213] By adjusting the diameter of the primary particles in the oriented secondary particles within the aforementioned range, it is beneficial to control the active crystal surface ratio of the primary particles, so that the lithium ion insertion and extraction kinetics of the primary particles are further improved.

[0214] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have an L value within a range of 400 nm to 1500 nm, optionally within a range of 400 nm to 1500 nm, and further optionally within a range of 400 nm to 1400 nm. Without limitation, 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. Without limitation, at least 80% of the primary particles in the oriented secondary particles have an L value 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.

[0215] In some embodiments, the L value of the primary particles in the oriented secondary particles is within a range of 400 nm to 1500 nm, optionally within a range of 400 nm to 1500 nm, and further optionally within a range of 400 nm to 1400 nm. Without limitation, 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. Without limitation, the L value of the primary particles in the oriented secondary particles is within any of the following ranges: 400nm to 1600nm, 400nm to 1500nm, 400nm to 1400nm, 400nm to 1350nm, 400nm to 1200nm, 400nm to 1000nm, 450nm to 1600nm, 450nm to 1500nm, 450nm to 1400nm, 450nm to 1350nm, 450nm to 1200nm, 450nm to 1000nm, etc.

[0216] In some embodiments, at least 80% of the primary particles in the oriented secondary particles have a W value within a range of 100 nm to 800 nm, optionally within a range of 200 nm to 700 nm, and further optionally within a range of 200 nm to 600 nm. Without limitation, 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 W values ​​within any of the following ranges: 100nm-700nm, 200nm-800nm, 200nm-600nm, 250nm-800nm, 250nm-700nm, 250nm-600nm, etc.

[0217] In some embodiments, the W value of the primary particles in the oriented secondary particles is within the range of 100 nm to 800 nm, optionally within the range of 200 nm to 700 nm, and further optionally within the range of 200 nm to 600 nm. Without limitation, the W value of the primary particles in the oriented secondary particles is within the range 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, the W value of the primary particles in the oriented secondary particles is within any of the following ranges: 100 nm to 700 nm, 200 nm to 800 nm, 200 nm to 600 nm, 250 nm to 800 nm, 250 nm to 700 nm, 250 nm to 600 nm, etc.

[0218] In some embodiments, the particle size distribution parameter SPAN of the positive electrode active material satisfies 1.1≤SPAN≤1.4, optionally, 1.2≤SPAN≤1.3. Without limitation, the particle size distribution parameter SPAN of the positive electrode active material may also be any of the following values ​​or an interval consisting of any two of the following values: 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, etc.

[0219] 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 an appropriate volume ratio, respectively. This allows the positive electrode active material to have both high capacity and high powder compaction density, which helps maximize the volumetric energy density of the positive electrode. By designing a combination of large and small particles, the resulting polycrystalline material can increase the volumetric energy density of the positive electrode material.

[0220] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0221] D of positive electrode active material v 90 satisfies: 15μm≤D v 90≤18μm, optionally, 16μm≤D v 90≤17μm;

[0222] D of positive electrode active material v 10Satisfies: 4μm≤D v 10≤6μm, optionally, 4.5μm≤D v 10≤5.5μm;

[0223] D of positive electrode active material n10 satisfied: D n 10≥2μm.

[0224] 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. Without limitation, the D v 90 can be any of the following values ​​or an interval consisting of any two of the following values: 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, etc.

[0225] By controlling the D v 90 is within the aforementioned range, which is beneficial for controlling the volume ratio of large particles in the material, controlling the specific surface area, and inhibiting side reactions.

[0226] In some embodiments, the D of the positive electrode active material v 10Satisfies: 4μm≤D v 10≤6μm, optionally, 4.5μm≤D v 10≤5.5μm. Without limitation, D v 10 can be any of the following values ​​or a range consisting of any two of the following values: 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc.

[0227] By controlling the D v 10 Within the aforementioned range, it is beneficial to control the volume ratio of small particles in the material to be appropriate, which is beneficial to improving the compaction density of the material.

[0228] In some embodiments, the D of the positive electrode active material n 10 satisfied: D n 10≥2μm

[0229] By controlling the D n 10 Within the aforementioned range, the number of small particles in the material can be controlled within a more appropriate range, which is conducive to controlling a more appropriate specific surface area, thereby improving the storage life of the battery.

[0230] In some embodiments, in the aligned secondary particles, the positive electrode active material includes a layered lithium ion active material.

[0231] When the positive electrode active material in the oriented secondary particles includes a layered lithium ion active material, the positive electrode active material including the oriented secondary particles may be obtained by using, but not limited to, the methods exemplified in the present application.

[0232] Non-limiting examples of the layered lithium ion active material may include layered lithium transition metal oxides. Non-limiting examples of the layered lithium ion active material may include lithium-containing nickel composite oxides, etc.

[0233] In some embodiments, in the aligned secondary particles, the positive electrode active material includes a lithium-containing nickel composite oxide.

[0234] In this application, unless otherwise specified, "lithium transition metal oxide" refers to a lithium ion active material containing a transition metal element.

[0235] In this application, unless otherwise specified, "lithium-containing nickel composite oxide" refers to a lithium-ion active material containing nickel. It is understood that a lithium-containing nickel composite oxide contains at least lithium, nickel, and oxygen, and may or may not contain other transition metal elements, such as Zr, Al, and Sr. The lithium-containing nickel composite oxide may or may not contain non-metallic elements, such as B and C.

[0236] By introducing lithium-nickel composite oxide into the positive electrode active material of the oriented secondary particles, the introduction of nickel element is beneficial to improving the energy density of the positive electrode active material, and is also beneficial to improving the power performance of the battery.

[0237] In this application, unless otherwise specified, the molar ratio of nickel to oxygen (O) in the lithium-containing nickel composite oxide is denoted as Q Ni / O .

[0238] In some embodiments, in the oriented secondary particles, 0.3≤Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5. Without limitation, in oriented secondary particles, Q Ni / O It can be any of the following values ​​or an interval consisting of any two of the following values: 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0239] In this application, unless otherwise specified, the molar ratio of nickel to lithium (Li) in the lithium-containing nickel composite oxide is denoted as Q Ni / Li .

[0240] In some embodiments, in the oriented secondary particles, 0.6≤Q Ni / Li ≤1, optionally 0.8≤Q Ni / Li ≤1. Without limitation, in oriented secondary particles, Q Ni / Li It can be any of the following values ​​or an interval consisting of 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.

[0241] The molar ratio of nickel and oxygen in the lithium-containing nickel composite oxide (Q Ni / O ) and / or the molar ratio of nickel and lithium in the lithium-containing nickel composite oxide (Q Ni / Li ) is controlled 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.

[0242] In some embodiments, the lithium-containing nickel composite oxide comprises at least one of a cobalt (Co) element and an M element, wherein the M element is at least one of an Mn element and an Al element. In some embodiments, the lithium-containing nickel composite oxide comprises Co and Mn elements. In some embodiments, the lithium-containing nickel composite oxide comprises Co and Al elements.

[0243] In some embodiments, the lithium-containing nickel composite oxide is a lithium-containing nickel-cobalt-manganese composite oxide.

[0244] 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 the lithium-containing nickel-cobalt-manganese composite oxide contains at least lithium, nickel, cobalt, manganese, and oxygen, and may or may not contain other transition metal elements, such as Zr, Al, and Sr. The lithium-containing nickel composite oxide may or may not contain non-metallic elements, such as B and C.

[0245] In some embodiments, the lithium-containing nickel composite oxide includes a doping element, Q Ni / O <0.5, the doping element may include but is not limited to at least one of 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. Ni / O It can be but not limited to 0.3≤Q Ni / O <0.5, optionally 0.4≤Q Ni / O <0.5.

[0246] In some embodiments, at least a portion of the primary particles include a particle body and a coating layer located at least partially on the surface of the particle body, the particle body includes a lithium-nickel composite oxide, and the coating layer includes at least one element of Zr, Al, B, Sr and Ca.

[0247] In some embodiments, the 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 of Zr, Al, B, Sr and Ca.

[0248] In some embodiments, the oriented secondary particles satisfy one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0249] In oriented secondary particles, 0.3≤Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5;

[0250] In oriented secondary particles, 0.6≤Q Ni / Li ≤1, optionally 0.8≤Q Ni / Li ≤1;

[0251] The lithium-containing nickel composite oxide contains at least one of a cobalt element and an M element, wherein the M element is at least one of a Mn element and an Al element;

[0252] The lithium nickel composite oxide contains doping elements, Q Ni / O <0.5, the doping element includes at least one element selected from Zr, Al, B, Sr and Ca;

[0253] At least a portion of the primary particles include a particle body and at least a portion of a coating layer located on the surface of the particle body, the particle body includes a lithium-containing nickel composite oxide, and the coating layer includes at least one element selected from Zr, Al, B, Sr, and Ca.

[0254] By putting Q Ni / O and / or Q Ni / Li When controlled within the aforementioned range, the lithium-nickel composite oxide has a high nickel content, which can significantly improve the energy density of the positive electrode active material.

[0255] Introducing cobalt (Co) into lithium-nickel composite oxides is beneficial for stabilizing the material structure and improving the cycle and rate performance of the positive electrode active material.

[0256] Introducing manganese (Mn) elements into lithium-containing nickel composite oxides is beneficial for reducing costs and improving the structural stability of the material.

[0257] Introducing aluminum (Al) elements into lithium-nickel composite oxides can help improve the cycle stability of the material.

[0258] By modifying the lithium-nickel composite oxide through one or more of the aforementioned doping and coating methods, one or more of the following aspects can be achieved: enhanced material stability, increased material energy density, and improved cycle life. For example, bulk doping can stabilize the structure of the lithium-nickel composite oxide. For example, coating the surface of the lithium-nickel composite oxide with a fast ion conductor can improve the material's energy density and cycle life.

[0259] In some embodiments, 0.3≤Q Ni / O ≤0.5, optionally, 0.4≤Q Ni / O ≤0.5, and any appropriate range in the context may also be referred to; 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 foregoing substances, wherein the modified form includes one or more of doping modification and coating modification, the doping element used for doping modification includes at least one of Zr, Al, B, Sr, and Ca, and the coating element used for coating modification includes at least one of Zr, Al, B, Sr, and Ca;

[0260] The molar ratio R of nickel and oxygen in the positive electrode active material Ni / O Satisfying 0.4≤R Ni / O ≤0.5.

[0261] In some embodiments, the positive electrode active material satisfies one or more of the following characteristics:

[0262] D of positive electrode active material v 50 is 8μm~11μm, optional is 9μm~10μm;

[0263] The diameter of at least 80% of the primary particles in the oriented secondary particles is 100 nm to 1600 nm, and can be 400 nm to 1500 nm.

[0264] 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, wherein 1.1≤SPAN≤1.4, optionally, 1.2≤SPAN≤1.3.

[0265] The positive electrode active material of the oriented secondary particles can be provided with a ternary positive electrode active material with a high nickel content and its modified material. The modified form can include one or more of doping modification and coating modification, which can be used to obtain a ternary positive electrode active material with high energy density and long life. The structure of the ternary positive electrode active material can be stabilized by bulk doping, and the energy density and cycle life of the material can be improved by providing a fast ion conductor coating material on the surface of the ternary positive electrode active material. Combined with the regulation of the angle α1 and F1, the orientation and distribution of the primary particles in the secondary particles of the positive electrode active material can be regulated, and the balance between suppressing the internal penetration of the electrolyte and optimizing the distance of the lithium ion transmission path can be taken into account, thereby improving the mass energy density of the material and the lithium ion diffusion kinetics. Furthermore, by controlling the D v50. If one or more of the primary particle diameters of the oriented secondary particles and the particle size distribution parameter SPAN of the positive electrode active material are within the aforementioned ranges, 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 proportions, further improving 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 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 material's bulk structure and surface stability, thereby achieving a longer cycle life.

[0266] In some embodiments, in the oriented secondary particles, the L average value of the inner layer is less than 700 nm (optionally, the L average value of the inner layer is less than 660 nm), and the L average value of the outer layer is greater than or equal to 720 nm (optionally, the L average value of the outer layer is greater than or equal to 750 nm).

[0267] Without limitation, in the oriented secondary particles, the L average value of 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.

[0268] Without limitation, in the oriented secondary particles, the L average value of 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.

[0269] 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.

[0270] For the positive electrode active material in the oriented secondary particles, including the positive electrode active material containing lithium nickel composite oxide, by controlling the L average value of the inner layer and the outer layer in the oriented secondary particles within the aforementioned range, the outer layer can have a faster active ion deintercalation efficiency, and the inner layer can have a larger angle to better inhibit the electrolyte from penetrating into the grain boundary, which is more conducive to comprehensively improving the actual energy density, cycle performance and kinetic performance of the battery.

[0271] In this application, unless otherwise specified, a "secondary battery" includes a battery cell.

[0272] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy. Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0273] In some embodiments, the secondary battery further includes a negative electrode sheet, a separator, and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet.

[0274] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0275] In some embodiments, the secondary battery is a lithium ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt.

[0276] The following are some other descriptions about the positive electrode.

[0277] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material. It is understood that the positive electrode active material includes the aforementioned oriented secondary particles.

[0278] The positive electrode active material includes a positive electrode active substance.

[0279] The positive electrode active material includes secondary particles, which are aggregated particles including a plurality of primary particles; the primary particles include the positive electrode active material.

[0280] The positive electrode active material in the positive electrode active material can refer to the above description, but is not limited thereto.

[0281] 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 further may be greater than or equal to 90 wt %.

[0282] In some embodiments, the positive electrode active material layer may also use layered lithium ion active materials that are known in the art and can be used in batteries.

[0283] In some embodiments, the positive electrode active material layer may also use lithium-containing nickel composite oxides that are well known in the art and can be used in batteries.

[0284] As a non-limiting example, the layered lithium ion active material may include one or more of the following materials: lithium nickel-containing composite oxides and modified compounds thereof. However, the present 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-containing composite oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel-containing composite oxides, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel-containing 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 referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.80 Co 0.15 Al 0.05 O2.

[0285] It is understandable that the battery is accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the Li content in the positive electrode plate is different when the battery is discharged to different states.

[0286] 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 the non-initial state after charge and discharge cycles. The positive electrode active material is applied to the positive electrode plate in the battery system. After charge and discharge cycles, the Li content in the positive electrode active material contained in the positive electrode plate will usually change. Among them, the Li content can be measured using atomic molar content, but is not limited to this. Taking the wet preparation of positive electrode plates 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 the material is added to the positive electrode slurry. It can be understood that new materials or new substances obtained by appropriate modification on the basis of 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 a non-limiting example is coating modification.

[0287] In the exemplary descriptions of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the atomic molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by atomic molar content, but is not limited to this.

[0288] 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 base layer and a metal layer formed on at least one surface of the polymer material base layer. In the positive electrode current collector, the composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In a non-limiting manner, 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), polyethylene (PE), etc.

[0289] 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. Typically, the weight percentage of the binder in the positive electrode active material layer may be 0 to 10 wt%, further 0 to 8 wt%, and further 1 wt% to 5 wt%.

[0290] In some embodiments, the positive electrode active material layer optionally includes a conductive agent. As non-limiting examples, 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 may be 0 to 10 wt %, further 0 to 8 wt %, and even further 0 to 5 wt %.

[0291] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing a positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, in a solvent to form a positive electrode slurry. Furthermore, the positive electrode slurry is coated on at least one surface of a positive electrode current collector. After drying and cold pressing, the positive electrode sheet can be obtained. Cold pressing can be performed using a cold rolling mill. The type of solvent in the positive electrode slurry can include, but is not limited to, any of the aforementioned embodiments, and can include, for example, N-methylpyrrolidone (NMP), and can further be NMP. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode 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 single-side coating amount on the positive electrode current collector, when the positive electrode slurry is coated, the coating unit area density can be 13 mg / cm2 on a dry weight basis (excluding the solvent). 2 ~20 mg / cm 2 The compaction density of the positive electrode can be 3.0 g / cm 3 ~3.6 g / cm 3 , optional 3.3g / cm 3 ~3.5 g / cm 3 .

[0292] The term "compacted density" as used in this application has a well-known meaning in the art and is one of the reference indicators of material energy density. In this application, unless otherwise specified, the compacted density of an electrode plate refers to the ratio of the mass of the electrode active material layer to its volume. The compacted density of a positive electrode plate refers to the ratio of the mass of the positive electrode active material layer to its volume, and the compacted density of a negative electrode plate refers to the ratio of the mass of the negative electrode active material layer to its volume.

[0293] The following is some description about the negative electrode.

[0294] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0295] 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 further may be greater than or equal to 90 wt %.

[0296] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0297] 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 base layer 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 a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. Without limitation, 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), polyethylene (PE), etc.

[0298] In some embodiments, the negative electrode active material may adopt a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials or substances, and other traditional 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.

[0299] In some embodiments, the negative electrode active material includes one or more of a carbon-based material, a silicon-based material, a tin-based material, and lithium titanate, as well as modified forms of any of the foregoing materials, wherein the modified form includes one or more of a doping modification and a coating modification. Both the doping modification method and the coating modification method can adopt 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 but are not limited to one or more of graphite materials, soft carbon, hard carbon, etc. Graphite materials may include one or more of artificial graphite and natural graphite.

[0300] In some embodiments, the negative electrode active material includes a carbon-based material and a silicon-based material. Without limitation, the combined mass of the carbon-based material and the silicon-based material may account for ≥80% of the total mass of the negative electrode active material, optionally ≥90%, further optionally ≥95%, further optionally ≥96%, and further optionally 100%. The combined mass of the graphite material and the silicon-based material may also account for any of the following percentages, or a percentage greater than or equal to any of the following percentages and less than or equal to 100%, or a range consisting of any two of the following percentages: 80%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, and the like. The definition of carbon-based material can be found above. For example, the carbon-based material can be a graphite material. The content of the carbon-based material can also be found in any suitable embodiment described above.

[0301] In some embodiments, the negative electrode active material includes a carbon-based material. Without limitation, the mass percentage of the carbon-based material in the negative electrode active material can be ≥80%, optionally ≥90%, further optionally ≥95%, further optionally ≥96%, etc., further optionally 100%, etc. 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 the interval consisting of 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 materials can be found above. For example, the carbon-based material can be a graphite material.

[0302] In some embodiments, the negative electrode active material layer may optionally include a binder. Without limitation, 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). Without limitation, the weight percentage of the binder in the negative electrode active material layer may be 0 wt % to 20 wt %, further 0 wt % to 10 wt %, further 0 to 5 wt %, further 1 wt % to 5 wt %, and further optionally 1 wt % to 3 wt %.

[0303] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. Without limitation, 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. Without limitation, the weight percentage of the conductive agent in the negative electrode active material layer may be 0 wt% to 15 wt%, further preferably 0 wt% to 10 wt%, and even further preferably 0 wt% to 5 wt%.

[0304] In some embodiments, the negative electrode active material layer may optionally include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)). Without limitation, the weight percentage of the other additives in the negative electrode active material layer may be 0 wt% to 15 wt%, further optionally 0 wt% to 10 wt%, further optionally 0 wt% to 5 wt%, and further optionally 0 wt% to 3 wt%.

[0305] In some embodiments, a negative electrode sheet can be prepared by dispersing the components for preparing 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 the solvent is deionized water) to form a negative electrode slurry. Furthermore, the negative electrode slurry is coated on at least one surface of a negative electrode current collector. After drying and cold pressing, the negative electrode sheet can be obtained. The cold pressing can be performed using a cold rolling mill. The negative electrode current collector surface 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 30 wt% to 70 wt%, optionally 40 wt% to 60 wt%. 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 single-side coating amount on the negative electrode current collector, when the negative electrode slurry is coated, the coating unit area density based on dry weight (excluding solvent) can be 6.5 mg / cm 2 ~13mg / cm 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~2.0g / cm 3 , optional 1.0g / cm 3 ~1.8g / cm 3 .

[0306] The electrolyte is exemplarily described below.

[0307] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode. Unless otherwise specified, the electrolyte includes a liquid electrolyte.

[0308] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0309] In some embodiments, the electrolyte is a non-aqueous electrolyte. The non-aqueous electrolyte may include an electrolyte salt and a solvent.

[0310] The concentration of the electrolyte salt in the electrolyte solution may generally be 0.5 mol / L to 5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, etc., but is not limited thereto.

[0311] In some embodiments, the electrolyte salt includes an electrolyte lithium salt. Without limitation, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0312] In some embodiments, the secondary battery is a lithium ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt.

[0313] In some embodiments, the solvent in the non-aqueous electrolyte may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate One or more of 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.

[0314] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0315] 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), trifluoromethylethylene carbonate (TFPC), and the like.

[0316] In some embodiments, the electrolyte includes a solvent including at least one cyclic carbonate and at least two linear carbonates.

[0317] In some embodiments, in the electrolyte, the solvent includes C 3-6 Cyclic carbonate, C 4-10 The first chain carbonate and C 3-8 The second chain carbonate, wherein the number of carbon atoms of the first chain carbonate is greater than the number of carbon atoms of the second chain carbonate.

[0318] In some embodiments, in the electrolyte, C 3-6 Cyclic carbonates include ethylene carbonate, C 4-10 The first chain carbonate includes diethyl carbonate, C 3-8 The second chain carbonate includes dimethyl carbonate.

[0319] The separator is exemplarily described below.

[0320] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0321] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

[0322] In some embodiments, the thickness of the isolation film is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0323] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0324] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0325] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0326] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0327] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 3 The battery cell 5 is a square structure as an example.

[0328] In some embodiments, reference Figure 4 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0329] In some embodiments, the electrolyte has a filling coefficient greater than or equal to 1.6 g / Ah.

[0330] The secondary battery may be a battery module 4 or a battery pack 1 .

[0331] A battery module includes at least one battery cell. The number of battery cells contained 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.

[0332] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0333] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0334] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0335] Figure 6 and Figure 7 The battery pack 1 is used as an example. Figure 6 and Figure 7The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0336] In a second aspect of the present application, a positive electrode active material is provided, which includes the aforementioned oriented secondary particles.

[0337] In some embodiments, the positive electrode active material includes secondary particles, which are agglomerated particles including primary particles; the primary particles include the positive electrode active material;

[0338] In any secondary particle, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any primary particle is recorded as the longitudinal direction; in any primary particle, the longest axis of the primary particle is recorded as the a-axis;

[0339] 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 recorded as F1, where 15°≤α1≤45°, and F1≥60%.

[0340] Positive electrode sheets prepared using the aforementioned positive electrode active materials can be used to prepare secondary batteries with high energy density, good kinetic performance, and long cycle life. By utilizing the orientation angle and number ratio of the primary particles included in the oriented secondary particles in the positive electrode active material, it is possible to inhibit the electrolyte from penetrating into the grain boundaries of the secondary particles, which helps to inhibit side reactions between the electrolyte and the surface of the positive electrode active material, thereby increasing the actual gram capacity and cycle life of the positive electrode active material. Furthermore, a shorter active ion deintercalation path is achieved, which facilitates the rapid deintercalation of active ions during the charge and discharge process, thereby improving the actual energy density of the secondary battery and imparting good kinetic performance to the secondary battery.

[0341] In some embodiments, a positive electrode active material in a secondary battery described in the first aspect of the present application is provided.

[0342] In yet another aspect of the present application, a method for preparing a positive electrode active material is provided, which can be used to prepare the aforementioned positive electrode active material.

[0343] In some embodiments, a method for preparing a positive electrode active material is provided, comprising the following steps:

[0344] S10: preparing a precursor; and

[0345] S20: sintering a first mixture including a precursor and a lithium source for a first time at a temperature T1 to obtain a first sintered product, and then sintering a second mixture including the first sintered product for a second time at a temperature T2 to obtain a positive electrode active material; wherein T1>T2.

[0346] In step S10 , the type of transition metal element in the precursor may be selected according to the crystal structure required for the positive electrode active material, and then a suitable metal source may be selected.

[0347] In step S10 , the precursor may be prepared by a co-precipitation method, but is not limited thereto.

[0348] In the above embodiment, the temperature T1 is higher than the temperature T2. Therefore, the temperature conditions for the first sintering can be described as "high temperature conditions" and the temperature conditions for the second sintering can be described as "low temperature conditions."

[0349] In some embodiments, the temperature T1 for the first sintering may be 700° C. to 800° C., for example, 700° C., 720° C., 740° C., 750° C., 760° C., 780° C., 800° C., etc., and may also be selected from a range consisting of any two of the aforementioned temperatures. Furthermore, the sintering time for the first sintering may be 15 hours to 30 hours, for example, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 26 hours, 28 hours, 30 hours, etc., and may also be selected from a range consisting of any two of the aforementioned time durations.

[0350] In some embodiments, the temperature T2 for the second sintering may be 200° C. to 500° C., for example, 200° C., 250° C., 300° C., 350° C., 400° C., 450° C., 500° C., etc., and may also be selected from a range consisting of any two of the aforementioned temperatures. Furthermore, the sintering time for the second sintering may be 3 hours to 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., and may also be selected from a range consisting of any two of the aforementioned time durations.

[0351] After step S10, a laser particle size analyzer may be used to perform testing to obtain the particle size and SPAN value of the precursor particles, thereby screening precursors with a suitable particle size range and SPAN value for step S20.

[0352] Unless otherwise specified, at least one of the first sintering and the second sintering is performed in an oxygen-containing atmosphere. In some embodiments, both the first sintering and the second sintering are performed in an oxygen atmosphere.

[0353] In step S20, the molar ratio of the precursor to the lithium source, calculated as OH, can be 1:(1.03-1.07), such as 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, a slight excess of lithium is usually used.

[0354] In step S20, during the first sintering, the first mixture may further include a dopant for introducing a doping element. It is understood that, under normal doping amounts, the introduction of the doping element generally does not affect the crystal structure type of the grains.

[0355] In step S20, when the second sintering is performed, the second mixture may further include a coating agent for introducing a coating element. It is understood that the introduction of the coating element can form a coating layer on at least a portion of the surface of the particles obtained from the first sintering product.

[0356] Without limitation, based on the precursor, doping modification and coating modification can be performed simultaneously.

[0357] Taking the positive electrode active material including a lithium-nickel composite oxide as an example, in some embodiments, a method for preparing a positive electrode active material is provided, including steps S10 and S20, wherein step S10 is S100 and step S20 is S200.

[0358] S100: preparing a nickel-containing precursor.

[0359] A nickel-containing precursor can be prepared using a method comprising the following steps: dissolving a metal source, including a nickel source, in water to prepare a metal solution according to the elemental composition of the target chemical formula of the positive electrode active material, in the desired type and amount; mixing the metal solution, a complexing agent, and a precipitant, performing a coprecipitation reaction under dispersion conditions, performing solid-liquid separation, washing, and drying to obtain the nickel-containing precursor. The nickel-containing precursor is the corresponding metal hydroxide.

[0360] In step S100, by controlling the type of metal source, the grain structure and particle morphology of the positive electrode active material can be regulated by controlling the type of transition metal element in the nickel-containing precursor. For example, using a metal source including a nickel source can be used to prepare a layered lithium-ion active material containing nickel.

[0361] 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 source, cobalt source, and manganese source can be selected based on the Ni:Co:Mn molar ratio in the target chemical formula.

[0362] Typically, a metal source is used to provide the transition metal in the nickel-containing precursor.

[0363] Non-limitingly, the metal source can use a soluble salt of the corresponding metal. Taking lithium-nickel composite oxide as an example, a soluble nickel salt (such as nickel sulfate) can be used to provide a nickel source; taking lithium-nickel-cobalt-manganese composite oxide as an example, a soluble cobalt salt (a non-limiting example of a soluble cobalt salt is cobalt sulfate) and a soluble manganese salt (a non-limiting example of a soluble manganese salt is manganese sulfate) can be used to provide a cobalt source and a manganese source respectively. 0.82 Co 0.12 Mn 0.06 Taking the O2 nickel-containing precursor as an example, nickel sulfate, cobalt sulfate and manganese sulfate with a molar ratio of 82:12:6 can be used as metal sources.

[0364] Non-limiting examples of complexing agents may include aqueous ammonia.

[0365] In some embodiments, the molar ratio of ammonia to the metal element is 1 to 2, with non-limiting examples including 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, and the like, and may also be selected from a range consisting of any two of the aforementioned values. Ammonia may be present in excess to provide sufficient complexation. Adjusting the amount of ammonia used can influence the orientation of the primary particles within the secondary particles and the secondary particle morphology.

[0366] In some embodiments, in the coprecipitation reaction system, the concentration of ammonia 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 can also be selected from the range consisting of any two of the foregoing concentrations.

[0367] In some embodiments, the precipitant is an alkaline agent. Non-limiting examples of precipitants can include alkali metal hydroxides. Non-limiting examples of alkali metal hydroxides can include sodium hydroxide.

[0368] 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., and can also be selected from the range consisting of any two of the aforementioned temperatures.

[0369] 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 a range consisting of any two of the aforementioned pH values. By adjusting the pH of the reaction system, the orientation of the primary particles within the secondary particles and the morphology of the secondary particles can be influenced.

[0370] In some embodiments, the reaction temperature for the coprecipitation reaction may be 40° C. to 60° C., and the pH may be 11.2 to 11.8. The selection of temperature conditions may affect the growth process of the primary particles and may also affect the orientation behavior of the primary particles during growth.

[0371] Without limitation, the dispersion conditions may be stirring. In some embodiments, the stirring rate is 400 rpm to 1000 rpm, and may also be 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, etc., or may be selected from a range consisting of any two of the aforementioned stirring rates. By adjusting the stirring rate, the orientation of the primary particles in the secondary particles and the morphology of the secondary particles can also be affected.

[0372] After step S100, a laser particle size analyzer may be used to perform testing to obtain the particle size and SPAN value of the nickel-containing precursor particles, thereby screening nickel-containing precursors with a suitable particle size range and SPAN value for step S200.

[0373] S200: performing a first sintering and a second sintering to obtain a positive electrode active material including a lithium-containing nickel composite oxide.

[0374] In some embodiments, S200 includes the following steps: in an oxygen-containing atmosphere, sintering a first mixture including a nickel-containing precursor and a lithium source for a first time at a temperature T1 to obtain a first sintered product, and then sintering a second mixture including the first sintered product for a second time at a temperature T2 to obtain a positive electrode active material including a lithium-containing nickel composite oxide; wherein T1 is higher than T2.

[0375] In some embodiments, the lithium source is lithium hydroxide.

[0376] In some embodiments, the molar ratio of the nickel-containing precursor to the lithium source, calculated as OH, can be 1:(1.03-1.07), such as 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, etc., but is not limited thereto. Considering the lithium loss during the sintering process, a slight excess of lithium is usually used.

[0377] In some embodiments, the steps of performing the first sintering and the second sintering include: first performing the first sintering at temperature T1 to obtain a first sintered product, and then performing the second sintering at 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.

[0378] In some embodiments, after the first sintering is completed, the first sintered product is obtained by crushing, washing, and drying.

[0379] In some embodiments, (T2-T1) ≥ 200°C, optionally, 200°C ≤ (T2-T1) ≤ 600°C, further optionally, 200°C ≤ (T2-T1) ≤ 400°C. Without limitation, (T2-T1) may also be any of the following values ​​or an interval consisting of any two of the following values: 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc.

[0380] In some embodiments, the sintering time t1 of the first sintering is greater than the sintering time t2 of the second sintering, t1>t2.

[0381] In some embodiments, T1 may be 700° C. to 800° C., for example, 700° C., 720° C., 740° C., 750° C., 760° C., 780° C., 800° C., etc., and may also be selected from a range consisting of any two of the aforementioned temperatures. Furthermore, the sintering time for the first sintering may be 15 hours to 30 hours, for example, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 26 hours, 28 hours, 30 hours, etc., and may also be selected from a range consisting of any two of the aforementioned time durations.

[0382] In some embodiments, T2 may be 200°C to 500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc., and may also be selected from a range consisting of any two of the aforementioned temperatures. Furthermore, the sintering time for the second sintering may be 3 hours to 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., and may also be selected from a range consisting of any two of the aforementioned time lengths.

[0383] Without limitation, a dopant may be introduced during the first sintering. The first mixture comprising the nickel-containing precursor, the lithium source, and the dopant may be sintered to achieve doping modification and introduce the doping element into the positive electrode active material. Alternatively, no dopant may be introduced. The type of doping element can be found in the examples above.

[0384] Without limitation, a coating agent may be introduced during the second sintering. The second mixture comprising the first sintered product and the coating agent is subjected to a second sintering to achieve coating modification, thereby forming a positive electrode active material with a coating layer. The coating layer includes a coating element provided by the coating agent. Alternatively, no coating agent may be introduced. The type of coating element can be found in the examples above.

[0385] Without limitation, based on the nickel-containing precursor, doping modification and coating modification can be performed simultaneously.

[0386] The elemental structure and elemental composition of the precursor and the positive electrode active material can be determined by the structural and elemental composition analysis methods of the positive electrode active material known in the art. For example, the structure of the particles can be analyzed by ion polishing cross-sectional morphology analysis combined with scanning electron microscopy (SEM) and other methods, such as analyzing the presence or absence of a coating layer. As a non-limiting example, an IB-19500CP ion cross-sectional polisher can be used to polish the pole piece sample to obtain a polished sample with a cut surface; the sample can further be tested using a ZEISS sigma 300 device. For another example, an inductively coupled plasma spectrometer (ICP instrument, such as iCAP 7400 and other models) can be used to analyze the types and proportions of elements to determine the chemical formula of the precursor and the positive electrode active material.

[0387] The particle size and distribution of the cathode active material, as well as the size and orientation of the primary particles within the secondary particles, are influenced by the combined effects of the precursor preparation and sintering processes. The preceding description only describes some of these influences. For example, the choice of sintering temperature can affect the stacking pattern of the primary particles, which in turn influences their orientation and distribution.

[0388] The positive electrode active material including the oriented secondary particles can be obtained by the above method. Taking the preparation of the positive electrode active material including the lithium nickel composite oxide as an example, by adjusting the selection of the transition metal element in the metal source, the coprecipitation reaction temperature, the coprecipitation reaction pH value, the amount of the complexing agent (such as ammonia water), the amount of the precipitant (such as sodium hydroxide), the dispersion speed (dispersion method such as stirring), the particle size and distribution of the precursor (such as the D value of the precursor ... v 50, SPAN value), sintering method (such as temperature gradient design method), sintering temperature and sintering time and other parameters, one or more of which can adjust the growth, accumulation and orientation behavior of the primary particles, thereby affecting the size and morphology of the secondary particles formed and the size, orientation and orientation distribution of the primary particles in the secondary particles. The angle α1 (the angle formed by the a-axis of the primary particle and the longitudinal direction) and F1 (the proportion of the number of primary particles with the a-axis and the longitudinal direction forming an angle α1 in the oriented secondary particles) can be adjusted within the aforementioned range. Please refer to the embodiments below. In addition, the way in which the angle α1 deviates from the corresponding longitudinal direction (for example, it can deviate clockwise or counterclockwise), the anisotropic index I of the 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 above parameters. L / W and its distribution parameters (such as the inner R L / W Average value (R MI ), the outer R L / W Average value (R MO )) and other characteristic parameters). R can be achieved by adjusting the pH value and adding seed crystals. MI <RMO , including R that can achieve primary particles L / W The value increases sequentially from the center of the oriented secondary particle to the surface of the oriented secondary particle.

[0389] In yet another aspect of the present application, a positive electrode plate is provided, comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode active material described in the second aspect of the present application.

[0390] In a third aspect of the present application, an electrical device is provided, which includes the secondary battery described in the first aspect of the present application and at least one of the positive electrode active materials described in the second aspect of the present application.

[0391] In some embodiments, the present application further provides an electrical device, which includes a secondary battery of any embodiment provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, electric tools, etc., but are not limited thereto. The electrical device can also be used in military equipment, aerospace and other fields, and can also be used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations.

[0392] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0393] Figure 8 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0394] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0395] The following describes some embodiments of the present application. The embodiments described are only a portion of the embodiments of the present application, rather than all of the embodiments. The embodiments described below are exemplary and are only used to explain the present application, and should not be understood as limiting the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0396] If the techniques or conditions are not specified in the examples, the methods were carried out according to the description above, or according to the techniques or conditions described in the literature in the field, or according to the product instructions. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially or can be synthesized from commercial products according to conventional methods.

[0397] In the following specific examples, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument testing accuracy or operational accuracy are allowed.

[0398] In the following examples, room temperature refers to 20°C to 30°C.

[0399] The instruments involved in the following test and analysis methods are non-limiting examples, and those skilled in the art may also use other types of equipment or similar methods to perform test and analysis.

[0400] Test analysis methods

[0401] 1. Structural and elemental analysis

[0402] The chemical formula was determined by analysis using an inductively coupled plasma spectrometer (ICP).

[0403] Test instrument: iCAP 7400.

[0404] 2. D v 50. D v 90.D v 10 and D n 10Testing and SPAN analysis.

[0405] Testing instrument: Laser particle size analyzer Mastersizer 3000.

[0406] Method: Weigh an appropriate amount of the sample to be tested into a clean beaker and add 20ml of ethanol to disperse it (maintain a 25%-30% opacity). Ultrasonicate at 250W / 3min to fully disperse the sample. Pour the sample into the injection tower and circulate it with the solution into the test optical system. Irradiated by a laser beam, the particle size distribution is determined by receiving and measuring the energy distribution of the scattered light. This method is based on the GB / T19077-2016 / ISO 13320:2009 standard.

[0407] Draw the particle size volume distribution diagram based on the test data, and get D from the particle size volume distribution diagram v 50. D v 90.D v 10. SPAN=(D v 90-D v 10) / Dv 50. Draw a particle size distribution diagram based on the test data and get D from the particle size distribution diagram. n 10.

[0408] Some test results can be found in Table 3.

[0409] 3. Structural observation and statistical analysis of primary particles in secondary particles.

[0410] A focused ion beam electron microscope or an ion cross-section polisher is used to cut the secondary particles in the positive electrode active material layer of the positive electrode sheet to obtain a cross-sectional view that basically passes through the center of the secondary particles. The primary particle information in the cross-sectional view is further analyzed in combination with the test image of a scanning electron microscope (SEM).

[0411] (1) Focused ion beam electron microscope (FEI Scios 2HiVac equipment) or ion cross-section polisher.

[0412] The secondary particles were cut to expose a cross section that basically passed through the center of the secondary particles, and SEM observation was performed.

[0413] (2) Scanning electron microscopy (SEM)

[0414] Equipment: Apreo 2SEM field emission scanning electron microscope or ZEISS Sigma 300 scanning electron microscope.

[0415] Sample preparation method: Cut a sample of appropriate size (such as 5mm×5mm) and stick it on a sample table with conductive glue.

[0416] The test parameters for the Apreo 2SEM are: accelerating voltage (HV) 2.00kV, detector T1, OptiPlan mode, and probe current 50pA. The working distance, magnification, and horizontal field of view can be selected according to the particle size. Figure 2 The cross-sectional view of the oriented secondary particles shown in FIG. Figure 2 In the test, the working distance (WD) is about 4.16mm, the magnification (Mag) is 6500X, and the horizontal field of view width (HFW) is 19.5μm.

[0417] (3) Analysis of primary particle information in secondary particles.

[0418] refer to Figure 1 The schematic diagram is used to measure the parameters such as α1 of the primary particles, the direction in which α1 deviates from the radial direction of the secondary particles, L, W, etc., and the F1, R L / W 、R MI 、R MO , I α1 Some analysis results can be found in Tables 2 and 3.

[0419] From the SEM test results of the cross-section through the center of the secondary particle, the cross-section showing the outer peripheral outline of the complete secondary particle cross section is selected for the information statistics of the primary particle.

[0420] Select a certain number of primary particles N0 (N0 ≥ 12), outline the outer contour of the primary particle section in the cross-sectional diagram in an elliptical manner, and measure the maximum length value as the test value of the "diameter of the primary particle". The direction of the maximum length is recorded as the a-axis direction, and the straight line line1 passing through the center of the secondary particle and the center of the primary particle is determined. The measured value of the angle between the a-axis and the straight line line1 is recorded as α1; the distance between the two intersection points of the straight line line1 and the outer contour of the primary particle is recorded as L; determine the straight line line2 perpendicular to line1, and the distance between the two intersection points of the straight line line2 and the outer contour of the primary particle is recorded as W. Then R L / W =L / W. See Figure 1 .

[0421] Based on the distance R from the center of the secondary particle to the surface, the area from the center of the secondary particle (i.e., 0R) to 2 / 3R is designated as the "inner layer," and the area from 2 / 3R to the outer contour of the secondary particle (i.e., 1R) is designated 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 designated as the center of the oriented secondary particle.

[0422] The center of the primary particle is counted. If the center of the primary particle falls into the inner layer, it is counted in the inner layer; if the center of the primary particle falls into the outer layer, it is counted in the outer layer; if the center of the primary particle is at the boundary between the inner and outer layers, it is counted in the "inner layer."

[0423] According to the R L / W The statistical information of the inner layer can be calculated L / W Average value (R MI ) and the outer R L / W Average value (R MO ).

[0424] The number of angles of 15°≤α1≤45° is counted and recorded as N1, then F1 = N1 / N0×100%. F1 is the percentage of primary particles in the oriented secondary particles where the a-axis forms an angle of 15°≤α1≤45° with the corresponding longitudinal direction.

[0425] The direction in which α1 deviates from the radial direction of the secondary particles: when α1 deviates from the straight line L in the clockwise direction, it is marked as "+" and the counting result is N1; when α1 deviates from the straight line L in the counterclockwise direction, it is marked as "-" and the counting result is N2; when α1 is not within the range of 15°≤α1≤45°, it is marked as "other". α1 =N1 / N2.

[0426] (4) The proportion of oriented secondary particles in the secondary particles.

[0427] Oriented secondary particles are determined based on SEM analysis of a cross-section of at least ten randomly selected secondary particles, taken through the center of the particle. When 15° ≤ α1 ≤ 45° and F1 ≥ 60%, the particle is counted as an oriented secondary particle. α1 outside this range or F1 < 60% does not qualify as an oriented secondary particle. Based on the counting results, the percentage of oriented secondary particles is calculated and used as the test value for "Percentage of oriented secondary particles in the total secondary particles, P2."

[0428] Some of the results can be found in Table 3.

[0429] 4. Characterization of positive electrode active materials

[0430] (1) Powder compaction density

[0431] The powder compaction density can be determined by conventional methods in the art.

[0432] Testing instrument: electronic pressure testing machine or compaction density meter.

[0433] The test method using an electronic pressure testing machine as an example is as follows: a certain mass of powder m0 is placed in the mold of the electronic pressure testing machine. The bottom area of ​​the mold is recorded as A0. The pressure is adjusted to 4T. After maintaining the pressure for 30 seconds, the height h0 of the resulting powder block is read. According to the formula ρ = m0 / (A0×h0), the powder compaction density ρ at 4T is calculated.

[0434] The test method using the compaction density meter as an example is as follows: a certain mass of powder m0 is placed in a special compaction mold, the bottom area of ​​the mold is recorded as A0, and then the mold is placed on the compaction density meter, a pressure of 4T is applied, the pressure is maintained for 30s, and the thickness h0 of the powder block after pressure relief is recorded. According to the formula ρ = m0 / (A0×h0), the powder compaction density ρ under 4T is calculated.

[0435] Some of the results can be found in Table 3.

[0436] (2) Lithium ion solid phase diffusion coefficient test:

[0437] 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:

[0438] The test temperature was 25°C. The positive electrode active material was ground into a powder microelectrode. This powder microelectrode was connected to an electrochemical workstation and coulometric titration was performed. A GITT curve was obtained using a 20μA pulse current, a 1h titration time, and a 4h rest period (Note: To compare the effects of pulse current and time, a parallel experiment with 10μA and 10min was performed). The lithium ion diffusion coefficient D was calculated using the following formula:

[0439]

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

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

[0442] 5. Battery performance test

[0443] (1) Volume 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 it rest for 5 minutes, and then discharge at 1 / 3C to 2.5V to obtain the capacity C0. The voltage platform is recorded as U.

[0446] Then the volume energy density of the battery VED = C0 × U / V0.

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

[0448] (2) Cyclic performance test

[0449] At 25°C, charge the battery to be tested at a constant current of 1C to a voltage of 4.25V, then charge at a constant voltage of 4.25V to a current of 0.05C, let it sit for 5 minutes, and then discharge at a constant current of 1C to a voltage of 2.8V. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C0 of the battery after the nth cycle.n , then the battery capacity retention rate P after the nth cycle n =C n / C0×100%. The cycle is continued until the cell capacity retention rate decays to 80%.

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

[0451] Example 1.

[0452] 1. Preparation of positive electrode active materials

[0453] Preparation of nickel-containing precursor: According to the target chemical formula (LiNi 0.82 Co 0.12 Mn 0.06 O2), nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate are dissolved in deionized water to prepare a metal solution with a Ni:Co:Mn molar ratio of 82:12:6, and the metal solution, complexing agent ammonia water, and precipitant sodium hydroxide solution are pumped into the reactor for co-precipitation reaction. The entire reaction process is protected by inert gas (nitrogen). The temperature of the reaction system is 40°C to 60°C, the pH is between 11.2 and 11.8, the molar ratio of ammonia to metal elements is between 1 and 2, and the stirring rate is 400rpm to 1000rpm. After the reaction is completed, the precursor is obtained through washing, drying and other processes, which is a metal hydroxide.

[0454] Sintering nickel-containing precursors to prepare lithium-containing nickel composite oxide positive electrode active materials: the prepared nickel-containing precursors and lithium source lithium hydroxide are mixed evenly, and oxygen (O2) is passed through them under high temperature conditions for the first sintering, the high temperature sintering temperature is 700℃~800℃ (T1), and the sintering time is 15h~30h (t1). The prepared material is crushed, washed, dried and other processes to obtain a first sintered product; the first sintered product is subjected to a low temperature second sintering, the low temperature sintering temperature is 200℃~500℃ (T2), and the sintering time is 3h~8h (t2) to obtain a ternary positive electrode active material.

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

[0456] 2. Preparation of secondary batteries

[0457] (1) Preparation of positive electrode sheet

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

[0459] (2) Preparation of negative electrode sheet

[0460] Graphite, styrene 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 evenly to obtain a negative electrode slurry. The negative electrode slurry was coated on both surfaces of the copper foil, dried in a drying oven, cold pressed and cut to obtain a negative electrode sheet. The coating surface density on one side was 0.16g / (1540.25mm 2 ), about 10.39 mg / cm 2 .

[0461] (3) Isolation film

[0462] Choose conventional polypropylene film (PP film).

[0463] (4) Electrolyte

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

[0465] (5) Assembling secondary batteries

[0466] The positive and negative electrodes, along with the two separators, are placed in the order of separator-negative electrode sheet-separator-positive electrode sheet. One end of the positive and negative electrode sheets, along with the two separators, is fixed to the discharge roller, and the other ends are stacked together and fixed to the winding shaft. A motor rotates the winding shaft, winding the positive and negative electrode sheets, along with the two separators, to form a wound battery cell (wound electrode assembly).

[0467] The electrode assembly is placed in an aluminum shell, baked at 80°C to remove water, then the electrolyte is injected and sealed. After the process of standing, hot and cold pressing, formation, shaping, and capacity testing, a secondary battery is obtained.

[0468] Examples 2-5. A positive electrode active material and a secondary battery were prepared using a method substantially the same as that of Example 1. The difference is that the steps for preparing the positive electrode active material are adjusted by mainly adjusting one or more of the following parameters: the pH of the coprecipitation reaction system in the precursor preparation step, the concentration of the complexing agent ammonia water (to control the pH within the range of 11.2 to 11.8, the amount of sodium hydroxide can be adjusted accordingly), the reaction temperature and reaction time of the coprecipitation reaction, and the stirring rate, and the 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 covered in Table 1 can be appropriately adjusted according to the above description.

[0469] Example 6. A positive electrode active material and a secondary battery are prepared by the same method as in Example 1. The difference is that in the step of preparing the positive electrode active material, a nickel-containing precursor is prepared according to LiNi 0.6 Co 0.2 Mn 0.2 O2 adjusts the molar ratio of nickel source, cobalt source and manganese source to 6:2:2.

[0470] Comparative Example 1.

[0471] A positive electrode active material and a secondary battery were prepared using a method substantially similar to that of Example 1. The differences were that the steps for preparing the positive electrode active material were different. Specifically, in the precursor preparation step, the pH was 11.0±0.2, the molar ratio of ammonia to the metal element 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 obtains a positive electrode active material with a relatively low F1; F1 is the ratio of the number of primary particles whose a-axis forms an angle of 15°≤α1≤45° with the corresponding longitudinal direction in the oriented secondary particles.

[0473] Comparative Example 2.

[0474] A positive electrode active material and a secondary battery were prepared using a method substantially similar to that of Example 1. The differences were that the steps for preparing the positive electrode active material were different. In the precursor preparation step, the coprecipitation reaction temperature was 55°C, the pH was 11.2±0.2, the molar ratio of ammonia to the metal element was 1.1, and the stirring rate was 450 rpm. The second sintering was performed before the first sintering.

[0475] Preparation of lithium-nickel composite oxide positive electrode active material: The nickel-containing precursor is sintered at 450°C for 8 hours, crushed, washed, dried and other processes, and then evenly mixed with lithium source lithium hydroxide and sintered at 720°C for 18 hours.

[0476] This comparative example obtained a positive electrode active material in which most of the primary particles in the secondary particles had a small α1. According to statistical results, the α1 was less than 10°, that is, it can be considered that there were basically no oriented secondary particles.

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

[0478] Table 1.

[0479]

[0480] Test analysis results:

[0481] In Example 1-6, positive electrode active materials were prepared using lithium-containing nickel oxide as an example. According to the elemental analysis results, the elemental composition of the positive electrode active material was substantially consistent with the target chemical formula.

[0482] The positive electrode active materials prepared in Examples 1-6 above all meet the following characteristics:

[0483] (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%.

[0484] (2) The proportion of oriented secondary particles in the secondary particles of the positive electrode active material is P2 ≥ 75% (P2 ≥ 70% and P2 ≥ 60% are satisfied at the same time). In most embodiments, P2 ≥ 80% is satisfied, and further P2 ≥ 90% is satisfied. In some embodiments, P2 exceeds 95%;

[0485] (3) According to the statistical results, R L / W All satisfy R L / W ≤4, and all within 0.95≤R L / W ≤4, R L / W The average values ​​of R are all in the range of 1.5 to 2.5. L / W The average value is in the range of 1.5 to 2.0;

[0486] (4) According to the statistical results, all meet R MI <R MO , that is, the inner R L / W The average value is lower than the outer R L / W Average value; each embodiment satisfies R MI <1.8 and R MO ≥1.8, most embodiments meet 1.3≤R MI <1.8 and 1.8≤R MO ≤2.3; each embodiment satisfies the R L / W In the range of 1.2 to 4 and the inner layer RL / W At 0.95≤R L / W ≤2.8; most embodiments meet the R of at least 80% of the primary particles in the outer layer L / W The R of at least 80% of the primary particles in the inner layer is within the range of 1.4 to 4. L / W In the range of 0.95 to 2.0;

[0487] (5) According to the statistical results, the anisotropic index of the angle α1 satisfies 0.4≤I α1 ≤2.5, most embodiments meet 0.5≤I α1 ≤2.0;

[0488] (6) D of positive electrode active material v 50 is 8 μm to 11 μm, 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 the positive electrode active material satisfies 1.1≤SPAN≤1.4; some embodiments satisfy the D v 50 is 9 μm to 11 μm, at least 80% of the primary particles in the oriented secondary particles have diameters within the range of 400 nm to 1500 nm, and the positive electrode active material has a SPAN of 1.2 ≤ 1.3;

[0489] (7) According to statistical results, the positive electrode active material satisfies 15μm≤D v 90≤18μm, 4μm≤D v 10≤6μm, D n 10≥2μm; some embodiments further meet 16μm≤D v 90≤17μm, 4.5μm≤D v 10≤5.5μm.

[0490] Taking Example 1 as an example, according to 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 within the range of 0.95 to 4, R L / W The average value is 1.86, R MI 1.51μm, R MO is 2.05μm, meeting R MI <R MO ; R in the outer layer L / W The number of primary particles in the range of 1.4 to 4 accounts for about 81%, and the R L / W The number of primary particles in the range of 0.95 to 2.0 accounts for about 83%;

[0491] The L average value of the inner layer is less than 700 nm, the L average value of the outer layer is 783.5 nm (satisfying greater than or equal to 720 nm and also satisfying greater than or equal to 750 nm), and the L average value of the inner layer is 649.4 nm (satisfying less than or equal to 700 nm and also satisfying less than or equal to 660 nm). α1 About 1.75.

[0492] Table 2.

[0493]

[0494] 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 angle is not within the range of 15° to 45°.

[0495] The positive electrode active materials prepared in Examples 1-6 all have relatively high compaction densities, as shown in Table 3.

[0496] The lithium ion solid phase diffusion coefficient (25°C) of the positive electrode active materials prepared in Examples 1-6 is within 1×10 -9 cm 2 ·s -1 to 8×10 -9 cm 2 ·s - 1, wherein in Example 1 it is 2.5×10 -9 cm 2 ·s -1 Comparative Example 1 and Comparative Example 2 are both at 1×10 -9 cm 2 ·s -1 Below, where the comparative example 1 is 5.2×10 -10 cm 2 ·s -1 , in Comparative Example 2, it is 1.8×10 -10 cm 2 ·s -1 Please refer to Table 3.

[0497] The secondary batteries prepared in Examples 1-6 all have high energy density, good kinetic performance and long cycle life.

[0498] The positive electrode active material prepared in Comparative Example 1 had a low F1 value. The positive electrode active material prepared in Comparative Example 2 contained almost no oriented secondary particles. The α1 values ​​were all less than 10°, indicating that the primary particles were primarily distributed along the radial direction of the secondary particles. The secondary batteries prepared in Comparative Examples 1 and 2 exhibited varying degrees of decline in kinetic performance, energy density, and cycling performance.

[0499] Some test analysis results of some embodiments are summarized in Table 3.

[0500] Table 3.

[0501]

[0502] In Table 3, the powder compaction density at 4T was tested using an electronic pressure testing machine.

[0503] The above description of the various embodiments and examples tends to emphasize the differences between the various embodiments and examples. The similarities or similarities between them can be referenced and will not be repeated here for the sake of brevity. The various technical features of the above-described embodiments and examples can be combined in any way. To keep the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0504] It should be noted that the present application is not limited to the above-mentioned embodiments and examples. The above-mentioned embodiments and examples are only examples, and the embodiments and examples that have the same structure as the technical idea and play the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. The above-described embodiments and examples only express several embodiments and examples of the present application, and their descriptions are relatively detailed, but they cannot be understood as limiting the scope of the patent. In addition, without departing from the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments or examples, and other methods of constructing by combining some of the constituent elements in the embodiments or examples are also included in the scope of the present application.

Claims

1. A secondary battery, characterized in that: The invention comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material, wherein the positive electrode active material comprises secondary particles, wherein the secondary particles are aggregates comprising a plurality of primary particles; and the primary particles comprise a positive electrode active material. In any of the secondary particles, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any of the primary particles is recorded as the longitudinal direction; in any of the primary particles, the longest axis of the primary particle is recorded 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 recorded as F1, wherein 15°≤α1≤45°, and F1≥60%.

2. The secondary battery according to claim 1, wherein The angle α1 is obtained as follows: in the 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 the X direction; the X direction passing through the center of the cross section of the primary particle is the longitudinal direction corresponding to the primary particle; the longest axis in the cross section of the primary particle is recorded as the a-axis; the angle α1 is obtained based on the angle formed by the a-axis and the corresponding longitudinal direction.

3. The secondary battery according to claim 1, wherein F1≥64%。 4. The secondary battery according to claim 1, wherein The proportion of the oriented secondary particles in the secondary particles is recorded as P2, and P2 ≥ 60%.

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

7. The secondary battery according to claim 6, characterized in that L value, W value and R 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 the X direction; the X direction passing through the center of the cross section of the primary particle is the longitudinal direction corresponding to the primary particle; the L value is obtained according to the length value of the primary particle along the corresponding longitudinal direction, the W value is obtained according to the length value of the primary particle along the direction perpendicular to the corresponding longitudinal direction, and the R value is obtained according to the ratio obtained by dividing the L value by the W value. L / W value.

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

5.

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

0.

10. The secondary battery according to claim 6, wherein The distance from the center to the surface of the oriented secondary particle is recorded as R; the portion from the center of the oriented secondary particle to the position 2 / 3R from the center is recorded as the inner layer, and the portion from the position 2 / 3R from the center to the surface of the oriented secondary particle is recorded as the outer layer; In the oriented secondary particles, the inner layer R L / W The average value is recorded as R MI , the outer layer R L / W The average value is recorded 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 Satisfy 0.95≤R L / W ≤2.

8.

12. 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, 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 R L / W Satisfy 1.4≤R L / W ≤4, at least 80% of the primary particles in the inner layer have an R L / W Satisfy 0.95≤R L / W ≤2.

0.

13. The secondary battery according to claim 6, wherein In the oriented secondary particles, the R 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, characterized in that The number of primary particles in which the a-axis of the oriented secondary particles forms an angle α1 with the longitudinal direction is counted, and the anisotropic index of the angle α1 is recorded as I α1 , then 0.4≤I α1 ≤2.5; In the cross section passing through the center of the oriented secondary particle, the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the clockwise direction is recorded as a positive angle, and the angle α1 that the a-axis deviates from the corresponding longitudinal direction in the counterclockwise direction is recorded 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, characterized in that 0.5≤I α1 ≤2.0。 16. The secondary battery according to any one of claims 1 to 13, characterized in that The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 8μm~11μm; The diameter of at least 80% of the primary particles in the oriented secondary particles is within the range of 100 nm to 1600 nm, wherein the diameter of the primary particles refers to the maximum length of the primary particles 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, among which 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~11μm; At least 80% of the primary particles in the oriented secondary particles have a diameter within a 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 13, characterized in that 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 10Satisfies: 4μm≤D v 10≤6μm; The positive electrode active material D n 10 satisfied: 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: 4.5μm≤D v 10≤5.5μm.

20. The secondary battery according to any one of claims 1 to 13, characterized in that In the oriented secondary particles, the positive electrode active material includes a layered lithium ion active material.

21. The secondary battery according to any one of claims 1 to 13, characterized in that In the oriented secondary particles, the positive electrode active material includes a lithium-containing nickel composite oxide.

22. The secondary battery according to claim 21, wherein The molar ratio of nickel to oxygen in the lithium-containing 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, wherein The oriented secondary particles meet 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 a Co element and an M element, wherein the M element is at least one of a Mn element and an Al element; The lithium-nickel composite oxide contains a doping element, Q Ni / O <0.5, 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 includes a lithium-nickel composite oxide, and the coating layer includes at least one element of Zr, Al, B, Sr and Ca.

24. The secondary battery according to claim 21, 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 foregoing substances, wherein the modified form includes one or more of doping modification and coating modification, the doping element used for the doping modification includes at least one of Zr, Al, B, Sr, and Ca, and the coating element used for the coating modification includes at least one of Zr, Al, B, Sr, and Ca; The molar ratio R of nickel and oxygen in the positive electrode active material is Ni / O Satisfying 0.4≤R Ni / O ≤0.

5.

25. The secondary battery according to claim 24, characterized in that The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 8μm~11μm; At least 80% of the primary particles in the oriented secondary particles have a diameter within 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, among which 1.1≤SPAN≤1.

4.

26. The secondary battery according to claim 25, characterized in that The positive electrode active material satisfies one or more of the following characteristics: The positive electrode active material D v 50 is 9μm~10μm; At least 80% of the primary particles in the oriented secondary particles have a diameter within a 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 claim 24, characterized in that 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; Among them, the length value of the primary particle along the longitudinal direction is recorded as L, and the distance from the center to the surface of the oriented secondary particle is recorded as R; the part from the center of the oriented secondary particle to the position 2 / 3R away from the center is recorded as the inner layer, and the part from the position 2 / 3R away from the center to the surface of the oriented secondary particle is recorded as the outer layer.

28. The secondary battery according to claim 27, characterized in that In the oriented secondary particles, an average L value of the inner layer is less than or equal to 660 nm, and an 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 13, characterized in that The secondary battery further includes a negative electrode sheet, a separator and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet.

30. The secondary battery according to any one of claims 1 to 13, characterized in that The secondary battery is a lithium-ion secondary battery.

31. A positive electrode active material, characterized in that The positive electrode active material includes secondary particles, wherein the secondary particles are aggregates including a plurality of primary particles; the primary particles include a positive electrode active material; In any of the primary particles, the longest axis of the primary particle is recorded as the a-axis; in any of the secondary particles, the direction from the center of the secondary particle toward the surface is recorded as the X direction; the X direction passing through the center of any of the primary particles is recorded 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 whose a-axis forms an angle α1 with the longitudinal direction in the oriented secondary particles is recorded as F1, wherein 15°≤α1≤45°, and F1≥60%.

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

33. An electrical device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 30 and at least one of the positive electrode active materials according to claim 31 or 32.

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