Positive active material, positive pole piece, secondary battery, electric device and preparation method

Abstract

The invention provides a positive active material, a positive pole piece, a secondary battery, an electric device and a preparation method. The positive electrode active material includes polycrystalline particles denoted as first active particles and single-crystal or single-crystal-like particles denoted as second active particles, (Dv90-Dv10) / Dv50 of the first active particles and the second active particles are denoted as X1 and X2, respectively, and X1 / X2 satisfies 0.2 < = X1 / X2 < = 0.7.

Description

[0001] Related applications

[0002] This application is a divisional application of Chinese patent application filed on March 1, 2023, with application number CN2023800543236, entitled "Positive electrode active material, positive electrode sheet, secondary battery, power supply device and preparation method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of lithium-ion battery technology, and in particular to a positive electrode active material, a positive electrode sheet, a secondary battery, an electrical device, and a preparation method. Background Technology

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

[0005] With the widespread application of lithium-ion battery technology, the accelerated pace of life, and the development of various electronic products such as smartphones, tablets, smart wearables, power tools, and electric vehicles, the comprehensive performance requirements for positive electrode active materials are constantly increasing to meet the battery's comprehensive performance demands for high energy density and long storage life. Currently, improvements in battery storage life often result in a loss of energy density, making it difficult to achieve both performance goals simultaneously.

[0006] Therefore, there is an urgent need to develop lithium-ion batteries that can meet the combined requirements of energy density and long storage life. Summary of the Invention

[0007] In view of the above problems, this application provides a positive electrode active material, a positive electrode sheet, a secondary battery, an electrical device, and a preparation method. By using this positive electrode active material, storage life can be improved while maintaining energy density with minimal loss.

[0008] In a first aspect, this application provides a positive electrode active material, comprising a first active particle and a second active particle; wherein the first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X1; the second active particle is a single crystal or near-single crystal particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X2;

[0009] X1 / X2 satisfies 0.2≤X1 / X2≤0.7;

[0010] Among them, D v 90. Dv 50 and D v 10 represents the particle size corresponding to the cumulative volume distribution percentage of the multi-particle combination reaching 90%, 50%, and 10%, respectively.

[0011] This positive electrode active material employs a combination of polycrystalline active particles with unique particle size distribution characteristics and single-crystal or near-single-crystal active particles. The polycrystalline active particles have a (D) v 90-D v 10) / D v 50 with single-crystal or near-single-crystal active particles (D v 90-D v 10) / D v The lower 50 ratio (denoted as X1 / X2) allows for a reasonable matching of active particle sizes, which can significantly improve battery storage life while maintaining minimal loss of energy density. The inventors of this application speculate that this is because the content of small-sized polycrystalline particles is reduced, thereby reducing the active surface area, reducing the side reactions between the electrolyte and the cathode material during storage, and thus improving the chemical stability of the cell and extending the battery's storage life.

[0012] In some embodiments, a positive electrode active material is provided, comprising a first active particle and a second active particle; wherein the first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X1; the second active particle is a single crystal or near-single crystal particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X2;

[0013] X1 / X2 satisfies 0.2≤X1 / X2≤0.7;

[0014] The particle size of the first active particle is larger than that of the second active particle; in the particle size distribution curve of the positive electrode active material, the first active particle and the second active particle correspond to two discontinuous independent peaks respectively.

[0015] The D of the first active particle v 50 satisfies 7 μm≤D v 50≤15 μm, or, the D of the second active particle v 50 satisfies 1 μm ≤ D v 50≤6 μm;

[0016] Among them, D v 90. D v 50 and D v10 represents the particle size corresponding to the cumulative volume distribution percentage of the multi-particle combination reaching 90%, 50%, and 10%, respectively.

[0017] In some embodiments, in the particle size distribution curve of the positive electrode active material, the first active particle and the second active particle each correspond to two discontinuous independent peaks.

[0018] By controlling the particle size and distribution of polycrystalline particles and single-crystal or near-single-crystal particles, two discontinuous independent peaks can be generated for each type of particle on the particle size distribution curve of the positive electrode active material. At this point, the D values ​​of the two types of particles... v 90. D v 50 and D v 10 can be obtained by fitting and analyzing their respective particle size distribution peaks.

[0019] In some implementations, X1 / X2 satisfies 0.25≤X1 / X2≤0.55.

[0020] In some embodiments, the first active particle satisfies 0.3 ≤ X1 ≤ 1.0. Optionally, the first active particle satisfies 0.4 ≤ X1 ≤ 0.8.

[0021] In some embodiments, the second active particle satisfies 0.7 ≤ x2 ≤ 2.5. Optionally, the second active particle satisfies 0.7 ≤ x2 ≤ 2; further optionally, the second active particle satisfies 0.8 ≤ x2 ≤ 1.6.

[0022] By further adjusting the range of X1 / X2 values, or by further adjusting the X1 value of polycrystalline active particles or selecting the X2 value of monocrystalline or near-monocrystalline active particles to control the values ​​of X1 / X2, the matching of the active surface areas of the two particle sizes can be better coordinated, thereby better balancing the dual requirements of high energy density and long storage life, and improving battery storage life while maintaining good energy density.

[0023] In some embodiments, the D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2≤R Dv50 ≤4. Optionally, the D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2.3≤R Dv50 ≤4.0.

[0024] In some embodiments, the D of the first active particle v 50 satisfies 7 μm≤Dv 50≤ 15 μm. Optionally, the first active particles have a D v 50that satisfies 7 μm≤ D v 50≤ 14 μm.

[0025] In some embodiments, the second active particles have a D v 50that satisfies 1 μm≤ D v 50≤ 6 μm. Further optionally, the second active particles have a D v 50that satisfies 2 μm≤ D v 50≤ 4 μm.

[0026] By respectively regulating the D v 50range of the polycrystalline active particles and the single-crystal or single-crystal-like active particles in the positive active material, or by the D v 50ratio of the two, the active surface area of different active particles can be synergistically controlled, so as to better reduce the side reaction between the electrolyte and the positive material during storage, and thus better improve the chemical stability of the battery cell and further prolong the storage life of the battery.

[0027] In some embodiments, the ratio R W of the weight of the first active particles to the sum of the weights of the first active particles and the second active particles satisfies 0.5≤ R W ≤ 0.9. Optionally, the ratio R W of the weight of the first active particles to the sum of the weights of the first active particles and the second active particles satisfies 0.7≤ R W ≤ 0.9.

[0028] By adjusting the weight ratio of the polycrystalline active particles in the positive active material to be within a certain range, for example, by regulating the ratio R W of the weight of the first active particles to the sum of the weights of the first active particles (the first active particles being the polycrystalline active particles in the positive active material) and the second active particles (the second active particles being the single-crystal or single-crystal-like active particles in the positive active material) to be within a certain range, such as 0.5≤ R W ≤ 0.9, etc., the active surface area can be more favorably reduced, the side reaction between the electrolyte and the positive material during storage can be reduced, and thus the chemical stability of the battery cell can be improved and the storage life of the battery can be prolonged.

[0029] In some embodiments, the first active particles and the second active particles are each independently an oxide material containing lithium and nickel elements.

[0030] Optionally, the nickel-lithium element number ratio R Ni / Liand the nickel-lithium element number ratio R in the second active particles Ni / Li each independently satisfies ≥0.65.

[0031] Further optionally, the nickel-lithium element number ratio R in the first active particles Ni / Li and the nickel-lithium element number ratio R in the second active particles Ni / Li each independently satisfies 0.8≤R Ni / Li ≤1.0.

[0032] In some embodiments, the first active particles and the second active particles are each independently ternary materials or ternary materials containing doping and / or coating elements.

[0033] Optionally, the first active particles and the second active particles are each independently NCM ternary materials, NCA ternary materials, NCM ternary materials containing doping and / or coating elements, or NCA ternary materials containing doping and / or coating elements.

[0034] Optionally, the first active particles and the second active particles each independently comprise a chemical composition having an element molar ratio of Li x (Ni a Co b M c M’ d )O2, wherein 0.9≤x≤1.2, 0.8≤a<1, 0

[0035] The higher the nickel content in the positive electrode active material, the more significant the deterioration of small-size particles (i.e., small-size polycrystalline active particles) in the polycrystalline active particles to the battery storage performance, and the more difficult it is to balance high energy density and long storage life. By using the positive electrode active material provided in the present application, the battery storage life can be significantly improved without substantially losing the energy density in a high-nickel system.

[0036] In some embodiments, the nickel-lithium element number ratio R in the first active particles Ni / Li is less than the nickel-lithium element number ratio R in the second active particles Ni / Li .

[0037] Optionally, the difference ΔR Ni / Li between the nickel-lithium element number ratio R in the second active particles and the nickel-lithium element number ratio R in the first active particles Ni / Li satisfies 0<ΔR Ni / Li ≤0.05.

[0038] Further, optionally, 0.01 < ΔR Ni / Li ≤0.05.

[0039] By adjusting the ratio of nickel to lithium elements R between polycrystalline particles and single-crystal or near-single-crystal particles Ni / Li The relative size of the polycrystalline grains makes the R Ni / Li R below single crystal or near-single crystal particles Ni / Li It can provide a higher available capacity of positive electrode active material, while also helping to improve the thermal stability of positive electrode active material and improve the high-temperature storage performance of battery.

[0040] Secondly, this application provides a positive electrode sheet comprising a positive active material layer, wherein the positive active material layer comprises the positive active material described in the first aspect of this application. In this case, using this positive electrode sheet can impart superior storage performance to the secondary battery while simultaneously maintaining good energy density.

[0041] In some embodiments, the compaction density of the positive electrode sheet is 3.2~3.8 g / cm³. 3 Optionally, the compaction density of the positive electrode sheet is 3.4~3.7 g / cm³. 3 When the compaction density of the positive electrode sheet is within the above range, it is beneficial to obtain a higher energy density while taking into account both battery energy density and storage performance.

[0042] Thirdly, this application provides a secondary battery, which includes the positive electrode sheet described in the second aspect of this application, and further includes a negative electrode sheet and a separator; wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet.

[0043] In the positive electrode of this secondary battery, the polycrystalline active particles and the single-crystal or near-single-crystal active particles have unique particle size distribution characteristics, which have excellent storage performance and can also maintain good energy density.

[0044] Fourthly, this application provides an electrical device comprising at least one of the positive electrode sheet described in the second aspect of this application and the secondary battery described in the third aspect of this application.

[0045] Fifthly, this application provides a method for preparing a positive electrode active material, which includes the following steps:

[0046] First active particles and second active particles were prepared separately.

[0047] The first active particle and the second active particle are mixed to obtain the positive electrode active material described in the first aspect of this application;

[0048] The first active particle is prepared by a method comprising the following steps: sintering precursor materials in accordance with element stoichiometric ratio, sintering temperature is 600-900℃, sintering time is 8-15h.

[0049] The second active particle is prepared by a method comprising the following steps: sintering precursor materials in accordance with element stoichiometric ratio, sintering temperature is 700-1000℃, sintering time is 8-15h.

[0050] By controlling the sintering parameters of the positive active material, the unique particle size distribution characteristics of the polycrystalline active particles and the single crystal or single crystal-like active particles can be controlled.

[0051] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0052] To better describe and illustrate the embodiments or examples of the application disclosed herein, reference can be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments or examples, and the best mode presently understood of these applications. Moreover, in all the drawings, the same reference numbers are used to represent the same components. In the drawings:

[0053] Figure 1 is a particle size distribution curve of the positive active material in an embodiment of the application;

[0054] Figure 2 is a schematic diagram of a secondary battery in an embodiment of the application;

[0055] Figure 3 is a schematic diagram of a secondary battery in an embodiment of the application; Figure 2 is an exploded view of a secondary battery in an embodiment of the application shown in FIG. 5;

[0056] Figure 4 is a schematic diagram of a power consuming device using a secondary battery in an embodiment of the application as a power source.

[0057] REFERENCE SIGNS:

[0058] 5, secondary battery; 51, shell; 52, electrode assembly; 53, cover plate; 6, power consuming device. DETAILED DESCRIPTION

[0059] Hereinafter, some embodiments of the positive electrode active material, the positive electrode sheet, the secondary battery, the power using device, and the production method of the present application will be explained in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed explanation is omitted. For example, there will be cases where detailed explanation of matters known well, repeated explanation of substantially identical structures are omitted. This is to avoid the following explanation from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application, and are not intended to define the subject matter of the claims.

[0060] The numerical ranges recited in this application are inclusive of the endpoints, unless specifically indicated otherwise. Ranges of values are presented as shorthand for describing a group of values. Any value within the range can be selected as the terminus of either the lower or the upper limit of the range. Any selected value can be combined with any other selected value, as long as the result is a numerical range. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" is intended to mean any and all subcombinations of the values between a and b, in which a and b are both real numbers. For example, the numerical range "0-5" is intended to mean that all real numbers between 0 and 5 have been listed herein, and "0-5" is merely a shorthand for listing all of those values. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is stated to be an integer selected from "2-10", it is equivalent to list the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0061] All embodiments of the present application and optional embodiments can be combined with each other to form new technical solutions, if not otherwise specified.

[0062] If not specified otherwise, all steps of the present application can be performed in sequence or randomly, and can be preferably performed in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method further comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0063] If not specified otherwise, "having", "including", "containing", and "comprising" mentioned in the present application can each independently mean open or closed. For example, "including" and "comprising" can mean that other members or timing features not listed can also be included or contained, or can mean that only the listed members or timing features are included or contained. Members are, for example, materials or components, structures, elements, instruments, etc. Non-limiting examples of timing features are actions, conditions for actions, timing, states, etc.

[0064] If not specified otherwise, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". Further, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0065] In the present application, A (such as B) means that B is one non-limiting example of A, and it can be understood that A is not limited to B.

[0066] In the present application, "and / or" corresponds to features or solutions including any one of two or more related listed items, and also including any and all combinations of the related listed items, including any two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" means a group consisting of A, B, and a combination of A and B. Wherein, "including A and / or B" can mean "including A, including B, and including a combination of A and B", and can also mean "including A, including B, or including a combination of A and B", which can be understood appropriately according to the sentence.

[0067] In the present application, "a plurality of", "a plurality of kinds", etc. refer to greater than or equal to 2 in number, if not specified otherwise. For example, "one or more" means one or greater than or equal to two.

[0068] In the present document, "preferably", "more preferably", "particularly preferably" and the like are used merely for the purpose of description and do not constitute limitations on the present application. If multiple "preferably"s occur in a technical solution, each "preferably" is independent of each other unless specifically stated otherwise or there is a contradictory or restrictive relationship.

[0069] In the present document, "further", "even further", "in particular" and the like are used for the purpose of description and do not constitute limitations on the present application.

[0070] In the present document, the terms "first", "second", "third", "fourth" and the like in "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are used only for the purpose of description and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the technical features indicated. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0071] In the present document, the units related to the data range, if only the right end point has a unit, it means that the units of the left end point and the right end point are the same. For example, 3~5 h or 3-5 h both mean that the units of the left end point "3" and the right end point "5" are h (hour).

[0072] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Further, the weight described in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0073] With the popularization and application of lithium ion battery technology, the comprehensive performance requirements of positive active materials are also increasing to meet the comprehensive performance requirements of high energy density and long storage life of batteries. In order to obtain a higher compaction density, the particle size distribution of active particles in the positive electrode sheet in the traditional technology is usually wide, for example, the (D v 90-D v 10) / D v 50 is mostly above 1.2 (≥1.2). When the positive active material has such a wide particle size distribution, it often includes a large number of small-size polycrystalline particles. However, the small-size particles in the polycrystalline particles will cause the deterioration of the storage performance of the battery, and if the (D v 90-D v 10) / D vA value of 50 would lead to a loss of compaction density, making it difficult to achieve both improved battery lifespan and low energy density loss.

[0074] In response to the above situation, in a first aspect, this application provides a positive electrode active material, which includes a first active particle and a second active particle; wherein, the first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X1; the second active particle is a single crystal or near-single crystal particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X2;

[0075] X1 / X2 satisfies 0.2≤X1 / X2≤0.7;

[0076] Among them, D v 90. D v 50 and D v 10 represents the particle size corresponding to the cumulative volume distribution percentage of the multi-particle combination reaching 90%, 50%, and 10%, respectively.

[0077] The positive electrode active material provided in this application includes polycrystalline particles referred to as the first active particle and single-crystal or near-single-crystal particles referred to as the second active particle, and the first active particle and the second active particle are further distinguished by (D v 90-D v 10) / D v Let 50 be denoted as X1 and X2 respectively. Then X1 / X2 satisfies 0.2≤X1 / X2≤0.7.

[0078] In this application, unless otherwise specified, the electrode sheet can be a positive electrode sheet or a negative electrode sheet. The "active material" in the electrode sheet refers to a material capable of reversibly inserting and extracting active ions. Unless otherwise specified, "negative electrode active material" refers to a material used in the negative electrode sheet capable of reversibly inserting and extracting active ions; "positive electrode active material" refers to a material used in the positive electrode sheet capable of reversibly extracting and inserting active ions. During charging of the secondary battery, active ions are extracted from the positive electrode and inserted into the negative electrode via the electrolyte; conversely, during discharging, active ions are extracted from the negative electrode and inserted into the positive electrode. The active ion is not particularly limited and can be lithium ions, in which case it corresponds to a lithium-ion secondary battery.

[0079] In the present application, "active material" and "active substance" have the same meaning and can be used interchangeably; "positive active material" and "positive active material" have the same meaning and can be used interchangeably; "negative active material" and "negative active material" have the same meaning and can be used interchangeably.

[0080] In the present application, unless otherwise specified, "active material layer" includes positive active material layer of positive electrode sheet and negative active material layer of negative electrode sheet, and according to the detailed circumstances, it can refer to positive active material layer or negative active material layer. It can be understood that the positive active material layer contains positive active material, and the negative active material layer contains negative active material.

[0081] In the present application, "polycrystal" is also called secondary particle, which refers to agglomerated particles formed by two or more primary particles. In the present application, the particle size of the primary particles constituting the polycrystal particles is generally controlled between 100 nm and 800 nm. If the particle size of the primary particles is too small, it may exacerbate the side reaction with the electrolyte, and if the particle size of the primary particles is too large, it may lead to deterioration of the battery dynamics.

[0082] In the present application, "single crystal" particle is also called primary particle, which refers to a single crystal grain; the micro-morphology of single crystal is a particle that is not substantially agglomerated, and the particle is dispersed. Single crystal can be an irregularly shaped particle. A single particle with a size greater than 1 μm and no obvious agglomeration is generally determined as a single crystal particle.

[0083] In the present application, "primary particle" and "secondary particle" are terms well known in the art.

[0084] In the present application, "single crystal-like" generally refers to a particle that has some agglomeration of primary particles, but has a size and properties similar to single crystal.

[0085] In the present application, the "size" or "particle size" of polycrystal particles and single crystal or single crystal-like particles, unless otherwise specified, refers to D v 50.

[0086] Polycrystal particles and single crystal or single crystal-like particles can be easily distinguished by taking SEM images using a scanning electron microscope.

[0087] In the context of the present application, the volume cumulative distribution particle size D v N (wherein N represents any numerical value selected from 0 to 100) can be used to characterize the particle size of the material, which refers to the particle size corresponding to the cumulative volume distribution percentage of N% of the material, and the volume percentage of the particle size less than or equal to D v N is N%. D v N can be obtained from the volume cumulative distribution curve of the material particle size, and unless otherwise specified, the volume cumulative distribution curve is accumulated from zero on the small particle size side.v 90, D v 50, D v 10, D v 90 refers to the particle size corresponding to the cumulative volume distribution percentage of 90% of the material, D v 50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50% of the material, D v 10 refers to the particle size corresponding to the cumulative volume distribution percentage of 10% of the material. D v 50, for example, indicates that 50% of the volume of the material is composed of particles with a particle size less than or equal to D v 50, and 50% of the volume of the material is composed of particles with a particle size greater than D v 50. D v 90, for example, indicates that 90% of the volume of the material is composed of particles with a particle size less than or equal to D v 90, and 10% of the volume of the material is composed of particles with a particle size greater than D v 90. D v 10, for example, indicates that 10% of the volume of the material is composed of particles with a particle size less than or equal to D v 10, and 90% of the volume of the material is composed of particles with a particle size greater than D v 10. Those skilled in the art can understand the meaning of D v 90, D v 50, D v 10, and can determine them using instruments and methods known in the art. For example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method can be referred to, and a laser particle size analyzer can be conveniently used for determination, such as Mastersizer 2000E laser particle size analyzer of Malvern Instruments Limited, UK, and LS-909 laser particle size analyzer (Omicron, Europe and America).

[0088] For a mixed system composed of multiple particles, the particle size parameter (D v 90-D v 10) / D v 50 can reflect the distribution characteristics of the particles, and thus is also a particle size distribution parameter. Generally, the larger the value of (D v 90-D v 10) / D v 50, the wider the particle size distribution, and conversely, the smaller the value, the narrower the particle size distribution.

[0089] Small-sized particles in polycrystalline particles can cause deterioration of the storage performance of the battery. This can be due to the large specific surface area of small-sized polycrystalline particles, which can easily cause particle breakage, leading to dissolution of transition metals in the positive electrode material, and thus deterioration of the storage performance. However, if (D v 90-D v10) / D v 50, which will result in a loss of the compacted density.

[0090] The positive electrode active material provided in the present application adopts a combination of polycrystalline active particles and single-crystal or single-crystal-like active particles with special particle size distribution characteristics, the D v 90-D v 10) / D v 50, and the D v 90-D v 10) / D v 50 ratio (denoted as X1 / X2) is low, so that the active particle size is reasonably matched, and the battery storage life can be significantly improved under the premise of basically no loss of energy density. The inventors of the present application speculate that this is because the content of small-size polycrystalline particles is reduced, thereby reducing the active surface area, reducing the side reaction between the electrolyte and the positive electrode material during storage, and thereby improving the chemical stability of the battery and prolonging the storage life of the battery.

[0091] In the positive electrode active material provided in the present application, by adjusting the value of X1 / X2, the particle size and particle size distribution between the polycrystalline active particles and the single-crystal or single-crystal-like active particles are finely matched, so that the balance between the content of small-size polycrystalline active particles and the compacted density of the positive electrode sheet can be better coordinated, thereby better meeting the dual requirements of battery storage performance and energy density.

[0092] In some embodiments, in the particle size distribution curve of the positive electrode active material, the first active particles and the second active particles correspond to two discontinuous independent peaks, respectively.

[0093] In the present application, unless otherwise specified, the particle size distribution curve can be measured by instruments commonly known in the art, such as the particle size distribution curve obtained by using a laser particle size analyzer. Further, a laser particle size analyzer such as Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK, or LS-909 laser particle size analyzer (EUKER) can be used.

[0094] By controlling the particle size and distribution of the polycrystalline particles and the single-crystal or single-crystal-like particles, in the particle size distribution curve of the positive electrode active material, the two kinds of particles can correspond to two discontinuous independent peaks, respectively, at this time, the D v 90, D v 50, and D v 10 can be obtained by fitting analysis according to the particle size distribution peaks of each, respectively.

[0095] Figure 1The shown particle size distribution curve is a particle size distribution curve obtained by testing the positive electrode active material in an embodiment of the present application using a laser particle size analyzer. The curve is a bimodal distribution, and has two independent peaks, respectively corresponding to the first active particles (large particles) and the second active particles (small particles) in the present application.

[0096] In the particle size distribution curve, the two peaks corresponding to the first active particles and the second active particles are discontinuous, meaning that the particle size ranges of the two active particles do not overlap, and the two particles can be easily separated from a mixture of the two particles, and then the two active particles of different sizes can be independently tested, such as, but not limited to, composition testing, specific surface area testing, etc.

[0097] In some embodiments, the particle size distribution curve of the positive electrode active material has and only has two peaks, and the two peaks are discontinuous independent peaks, and the two peaks respectively correspond to the particle size distribution of the first active particles and the second active particles.

[0098] In some embodiments, the X1 / X2 satisfies 0.2≤X1 / X2≤0.7. The X1 / X2 can be selected from any one of the following values: 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, etc., and can also be selected from an interval formed by any two of the above values, and a non-limiting example can include 0.25≤X1 / X2≤0.55.

[0099] In some embodiments, the first active particles satisfy 0.3≤X1≤1.0. The X1 of the first active particles can be selected from any one of the following values: 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc., and can also be selected from an interval formed by any two of the above values, and a non-limiting example can include 0.4≤X1≤0.8.

[0100] In some embodiments, the second active particle satisfies 0.7 ≤ X2 ≤ 2.5. X2 of the second active particle can be selected from any of the following values: 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2 (e.g., 2.0), 2.1, 2.2, 2.3, 2.4, 2.45, etc., or can be selected from any range of two of the above values. Non-limiting examples may include: 1.5 ≤ X2 ≤ 2.5, 0.7 ≤ X2 ≤ 2, 0.7 ≤ X2 ≤ 1.6, 0.8 ≤ X2 ≤ 1.6, 0.7 ≤ X2 ≤ 1.5, 0.8 ≤ X2 ≤ 1.5.

[0101] By further adjusting the range of X1 / X2 values, or by further adjusting the X1 value of polycrystalline active particles or selecting the X2 value of monocrystalline or near-monocrystalline active particles to control the values ​​of X1 / X2, the matching of the active surface areas of the two particle sizes can be better coordinated, thereby better balancing the dual requirements of high energy density and long storage life, and improving battery storage life while maintaining good energy density.

[0102] In some embodiments, the D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2≤R Dv50 ≤4. The D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 The value can be selected from any of the following: 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 (e.g., 4.0), etc., or from any interval consisting of any two of the above values. Non-restrictive examples may include: 2.3 ≤ R. Dv50 ≤4.0.

[0103] In some embodiments, the D of the first active particle v 50 satisfies 7 μm≤D v 50≤15 μm. The D of the first active particle v 50 can be selected from any of the following sizes: 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or it can be selected from any range consisting of any two of the above sizes. Non-limiting examples may include: 7 μm ≤ Dv 50≤ 14 μm.

[0104] In some embodiments, the second active particles have a D50 v 50≤ 14 μm. v 50≤ 6 μm. The second active particles have a D50 v 50may be selected from any one of the following sizes: 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc., and from an interval defined by any two of the above sizes, non-limiting examples of which can include: 2 μm≤ D50≤ 6 μm, 1 μm≤ D50≤ 4 μm, 2 μm≤ D50≤ 4 μm, 3.5 μm≤ D50≤ 6 μm, etc. v 50≤ 6 μm, 1 μm≤ D50≤ 4 μm. v 50≤ 4 μm, 2 μm≤ D50≤ 4 μm. v 50≤ 4 μm, 3.5 μm≤ D50≤ 6 μm. v 50≤ 6 μm.

[0105] In some embodiments, the first active particles have a specific surface area of 0.35-0.65 m2 / g; the specific surface area of the first active particles can be selected from any one of the following values: 0.35 m2 / g, 0.4 m2 / g, 0.45 m2 / g, 0.5 m2 / g, 0.55 m2 / g, 0.6 m2 / g, 0.65 m2 / g, etc., and from an interval defined by any two of the above values, non-limiting examples of which can include: 0.35-0.55 m2 / g. 2 2 2 2 2 2 2 2 2

[0106] In some embodiments, the second active particles have a specific surface area of 0.70-0.90 m2 / g; the specific surface area of the second active particles can be selected from any one of the following values: 0.7 m2 / g, 0.72 m2 / g, 0.74 m2 / g, 0.75 m2 / g, 0.76 m2 / g, 0.78 m2 / g, 0.8 m2 / g, 0.82 m2 / g, 0.84 m2 / g, 0.85 m2 / g, 0.86 m2 / g, etc., and from an interval defined by any two of the above values, non-limiting examples of which can include: 0.70-0.85 m2 / g. 2 2 2 2 2 2 2 2 2 2 2 2 ​​​​​​​​​​​​​​​​​​​​ / g, 0.88 m 2 / g, 0.9 m 2 / g, etc., can also be selected from an interval formed by any two of the above values, and non-limiting examples can include 0.70-0.85 m 2 / g.

[0107] In the present application, the specific surface area of the particulate matter refers to the ratio of the surface area of the particulate matter to the weight, which can be measured by using instruments and methods known in the art, for example, by using the nitrogen adsorption specific surface area analysis test method.

[0108] By respectively regulating the D v 50 of the polycrystalline active particles and the D v 50 of the single-crystal or single-crystal-like active particles in the positive electrode active material, or by regulating the ratio of the D

[0109] In the present application, the specific surface area (BET) of the positive electrode active material can be obtained by testing using the following method: testing by using the nitrogen adsorption specific surface area analysis test method and calculating by using the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by using the Tri Star II specific surface and pore analyzer of the Micromeritics company in the United States, and the testing steps can refer to GB / T 19587-2004. The sample to be tested: the prepared positive electrode active material; or the positive electrode active material sampled from the positive electrode active material layer of the positive electrode sheet. The testing and analysis method is as follows: drying the sample to be tested in a vacuum drying box at 200°C for 2 hours; then using argon as the adsorption gas, measuring the adsorption-desorption curve of the relative pressure P / P0 of 0-0.99 by using the specific surface and pore analyzer, P is the equilibrium adsorption pressure, P0 is the saturated vapor pressure, and the specific surface area of the positive electrode active material is calculated by using the BET method.

[0110] In some embodiments, the ratio R W satisfies 0.5≤R W ≤0.9. The ratio R WThe values ​​can be selected from any of the following: 0.5, 0.52, 0.54, 0.55, 0.56, 0.58, 0.6, 0.62, 0.63, 0.64, 0.65, 0.66, 0.68, 0.69, 0.7, 0.72, 0.74, 0.75, 0.76, 0.78, 0.8, 0.82, 0.84, 0.85, 0.86, 0.88, 0.9, etc., or from any interval consisting of any two of the above values. Non-restrictive examples may include: 0.7 ≤ R. W ≤0.9.

[0111] By adjusting the weight ratio of polycrystalline active particles in the positive electrode active particles within a certain range, for example, by controlling the ratio R of the weight of the first active particle to the sum of the weights of the first active particle (i.e., the polycrystalline active particle in the positive electrode active material) and the second active particle (i.e., the single-crystal or near-single-crystal active particle in the positive electrode active material). W Within a certain range, such as 0.5≤R W A value of ≤0.9 can help reduce the active surface area, decrease side reactions between the electrolyte and the cathode material during storage, thereby improving the chemical stability of the cell and extending the battery's storage life.

[0112] Furthermore, the higher the nickel content in the positive electrode active material, the more significant the deterioration of battery storage performance caused by small-sized polycrystalline active particles (i.e., small-sized polycrystalline active particles) becomes, making it more difficult to balance high energy density and long storage life. Using the positive electrode active material provided in this application can significantly improve battery storage life in high-nickel battery systems without substantially losing energy density.

[0113] In the application, "high nickel" is a general term used by those skilled in the art to refer to materials in lithium transition metal oxides with a high molar proportion of nickel. Typically, one mole of lithium transition metal oxide contains a nickel molar ratio of 0.8 or higher. Taking NCM811 ternary cathode material as an example, the molar ratio of nickel, cobalt, and manganese is 80:10:10. Increasing the nickel content in the cathode active material is beneficial for improving energy density and thus battery capacity.

[0114] In the lithium-ion battery system of this application, the nickel content can be characterized by the ratio of nickel to lithium elements for the positive electrode active material and the positive electrode sheet. This ratio can be called the nickel-lithium molar ratio, and can be denoted as R. Ni / Li Numerically, this can be equal to the molar ratio of nickel to lithium. In this application, R Ni / Li Each occurrence can independently be greater than or equal to 0.65, further can be independently greater than or equal to 0.7, and even further can be independently greater than or equal to 0.8. In some embodiments of this application, the nickel-lithium molar ratio R... Ni / Limay be selected from any one of the following numerical values or interval formed by any two of the following numerical values: 0.65, 0.7, 0.75, 0.8, 0.82, 0.85, 0.9, 0.95, 1, etc. In some embodiments of the present application, the nickel-lithium molar ratio R Ni / Li may be selected from any one of the following numerical intervals (wherein any numerical end point can be independently included or excluded): 0.65-1.0, 0.7-1.0, 0.8-1.0, 0.8-0.95, etc.

[0115] In some embodiments, the first active particles and the second active particles are each independently an oxide material containing lithium element and nickel element.

[0116] In the present application, the “oxide containing lithium element and nickel element” can be referred to as lithium nickel transition metal oxide. Non-limiting examples of the lithium nickel transition metal oxide can include, but are not limited to, one or more of lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, modified compounds thereof, etc. Among them, non-limiting examples of the lithium nickel oxide can include LiNiO2, etc. Non-limiting examples of the lithium nickel cobalt manganese oxide can include LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to as NCM 811 ), etc. Non-limiting examples of the lithium nickel cobalt aluminum oxide can include LiNi 0.85 Co 0.15 Al 0.05 O2, etc.

[0117] In some embodiments, the nickel-lithium element number ratio R Ni / Li and the nickel-lithium element number ratio R Ni / Li may each independently meet the definition of any one of the preceding embodiments, for example, ≥0.65. The R Ni / Li may each independently be selected from any one of the following numerical values: 0.65, 0.66, 2 / 3 (i.e., two-thirds), 0.67, 0.68, 0.7, 0.71, 0.75, 0.8, 0.85, 0.88, 0.89, 8 / 9 (i.e., eight-ninths), 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc., and can each independently be selected from an interval formed by any two of the above-mentioned numerical values. In some embodiments, the first active particles and the second active particles each independently satisfy any one of the following ranges: 0.65≤R Ni / Li≤ 1.1, 0.8≤ R Ni / Li ≤ 1.0, 0.8≤ R Ni / Li ≤ 0.95, 2 / 3≤ R Ni / Li ≤ 8 / 9, 0.66≤ R Ni / Li ≤ 0.89, 0.67≤ R Ni / Li ≤ 0.88, 0.70≤ R Ni / Li ≤ 1.07, 0.71≤ R Ni / Li ≤ 1.06, ≥ 0.7, ≥ 0.8, ≥ 0.85, ≥ 0.9, etc.

[0118] In some embodiments, the positive electrode active material of the first aspect of the present application further contains a doping element. Unless otherwise specified, the doping element in any of the positive electrode active materials in the present application (including but not limited to the positive electrode active material provided in the first aspect) can independently include one or more of transition metal elements and non-transition metal elements. Suitable doping elements and their contents can be selected according to functional requirements. The doping element can include but is not limited to one or more of Sb, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P, and C, etc. For lithium-ion batteries, the doping element can include but is not limited to one or more of Na, Sb, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P, and C, etc.

[0119] In some embodiments, the first active particles and the second active particles are each independently a ternary material or a ternary material containing a doping and / or coating element.

[0120] As used herein, “ternary material” has the commonly known meaning in the field of secondary battery technology, which means that in addition to including the corresponding element of active ions (such as lithium element) in the positive electrode active material, it can also include nickel (Ni) element and cobalt (Co) element, and can also include X element, which can be but is not limited to manganese (Mn) element or aluminum (Al) element. When the X element is Mn element, the ternary material can be denoted as NCM ternary material, non-limiting examples of which can include NCM 811 , etc.; when the X element is Al element, the ternary material can be denoted as NCA ternary material, non-limiting examples of which can include LiNi 0.85 Co 0.15 Al 0.05 O2, etc.

[0121] In the present application, unless otherwise specified, “ternary material containing a doping and / or coating element” means a ternary material containing a doping original ternary material, a ternary material containing a coating element, or a ternary material containing both a doping element and a coating element.

[0122] In some embodiments, the first active particles and the second active particles are each independently NCM ternary materials, NCA ternary materials, NCM ternary materials containing doping and / or coating elements, or NCA ternary materials containing doping and / or coating elements.

[0123] In the present application, unless otherwise specified, "NCM ternary materials containing doping and / or coating elements" means NCM ternary materials containing doping original NCM ternary materials, NCM ternary materials containing coating elements, or NCM ternary materials containing both doping elements and coating elements. Unless otherwise specified, "NCA ternary materials containing doping and / or coating elements" means NCA ternary materials containing doping original NCA ternary materials, NCA ternary materials containing coating elements, or NCA ternary materials containing both doping elements and coating elements.

[0124] In the present application, when the positive electrode active material contains coating elements, it means that the positive electrode active material has a coating layer located outside the bulk structure, which is composed of coating elements.

[0125] In some embodiments, the first active particles and the second active particles are each independently composed of a chemical composition having the following molar ratio of elements: Li x (Ni a Co b M c M’ d )O2, wherein 0.9≤x≤1.2, 0.8≤a<1, 0 Ni / Li In some embodiments, R Ni / Li is selected from (2 / 3)~(8 / 9). In other embodiments, R Ni / Li is selected from 0.67~0.88.

[0126] In some embodiments, the first active particles and the second active particles are each independently composed of one or more of the following elements: Na, K, Ca, Ba, Sb, Ti, Zr, W, Sr, Nb, Mo, Si, Mg, B, Cr, and Ta. The content of these elements can be flexibly adjusted according to the needs of improving the performance of the positive electrode active material, the positive electrode plate, or the secondary battery. For example, doping elements such as Mo, W, Zr, Nb, etc. in the positive electrode active material can control the crystal morphology and improve the interface performance of the electrolyte and the cathode material.

[0127] It should be noted that in the chemical composition formula of the first active particles and the second active particles described above, the molar equivalent of oxygen element is recorded as 2 for the sake of convenience, but there can be a certain non-integer case. In addition, x in the above composition formula can also be the molar equivalent of the raw material at the manufacturing stage of the ternary positive electrode material. Generally, the positive electrode material in the battery on the market has undergone formation aging process and can have undergone a certain number of charge and discharge cycles. Therefore, with the charge and discharge, the amount of Li in the positive electrode is sometimes lost. At this time, in the composition analysis, when discharged to the lower limit cut-off voltage of the battery, the lithium content x can be between 0.65 and 1.2.

[0128] In some embodiments, the nickel-lithium element number ratio R Ni / Li in the first active particles is less than the nickel-lithium element number ratio R Ni / Li in the second active particles. The nickel-lithium element number ratio R Ni / Li in the first active particles can be denoted as R1, and the nickel-lithium element number ratio R Ni / Li in the second active particles can be denoted as R2.

[0129] In some embodiments, the difference ΔR Ni / Li of the nickel-lithium element number ratio R Ni / Li in the second active particles relative to the nickel-lithium element number ratio R Ni / Li in the first active particles satisfies 0<ΔR Ni / Li ≤0.05. Wherein, ΔR Ni / Li =R2-R1.

[0130] In some embodiments, non-limiting examples of ΔR Ni / Li may include 0.01, 0.02, 0.03, 0.04, 0.05, and can also be an interval composed of any two of the foregoing, such as 0.01≤ΔR Ni / Li ≤0.05, 0.02≤ΔR Ni / Li ≤0.05, 0.02≤ΔR Ni / Li ≤0.04.

[0131] By adjusting the relative size of the nickel-lithium element number ratio R Ni / Li of the polycrystalline particles and the single crystal or single crystal-like particles, the R Ni / Li of the polycrystalline particles is lower than the R Ni / Li of the single crystal or single crystal-like particles, which can help to improve the thermal stability of the positive electrode active material and improve the high-temperature storage performance of the battery while providing a higher available capacity of the positive electrode active material.

[0132] In the present application, any one of the positive electrode active particles (may be but not limited to the first active particle or the second active particle) at least includes a positive electrode active particle body, and can further include or not include a coating layer; when including a coating layer, the coating layer is arranged on at least part of the surface of the positive electrode active particle body. By introducing a coating layer in the positive electrode active particle, the effect of reducing the cathode interface side reaction can be achieved.

[0133] In some embodiments, the first active particle includes an active particle body, and further includes or not includes a coating layer.

[0134] In some embodiments, the second active particle includes an active particle body, and further includes or not includes a coating layer.

[0135] In some embodiments, at least one of the first active particle and the second active particle includes a coating layer.

[0136] In some embodiments, the first active particle includes a coating layer, and the composition of the body and the coating layer of the first active particle can be the same or different.

[0137] In some embodiments, the second active particle includes a coating layer, and the composition of the body and the coating layer of the second active particle can be the same or different.

[0138] In some embodiments, the first active particle and the second active particle can each independently include a coating layer or not include a coating layer.

[0139] When a coating layer is arranged on the surface of the positive electrode active particle (may be but not limited to the first active particle or the second active particle), one or more of the aforementioned doping elements can be introduced in the coating layer. For example, introducing metal oxide in the coating layer can play the role of improving the stability of the electrode / electrolyte interface. For example, introducing fluoride in the coating layer can play the role of reducing electrolyte side reactions, reducing polarization, and improving the cycle stability of the positive electrode material under high current and high voltage. For example, introducing lithium in the coating layer can play the role of improving the structural stability of the positive electrode material. The thickness of the coating layer can be flexibly adjusted according to the performance improvement needs of the positive electrode active particle, the positive electrode sheet or the secondary battery. In some embodiments, the thickness of the coating layer is 1 nm to 50 nm, which can be optionally 1 nm to 10 nm. The thickness of the coating layer can be measured by a morphology observation method such as transmission electron microscopy. The mass and the elemental composition and content of the coating layer can be measured by an elemental analysis method such as inductively coupled plasma emission spectrometry.

[0140] In a second aspect, the present application provides a positive electrode sheet, which comprises a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode active material according to the first aspect of the present application. In this case, the use of the positive electrode sheet can impart superior storage performance to the secondary battery, while maintaining good energy density.

[0141] In some embodiments, the positive electrode sheet has a compacted density of 3.2-3.8 g / cm 3 The positive electrode sheet can have a compacted density selected from any one of the following densities: 3.2 g / cm 3 , 3.25 g / cm 3 , 3.3 g / cm 3 , 3.35 g / cm 3 , 3.4 g / cm 3 , 3.45 g / cm 3 , 3.5 g / cm 3 , 3.55 g / cm 3 , 3.6 g / cm 3 , 3.65 g / cm 3 , 3.7 g / cm 3 , 3.75 g / cm 3 , 3.8 g / cm 3 , and the like, or a range formed by any two of the above values. In some embodiments, the positive electrode sheet has a compacted density of 3.4-3.7 g / cm 3 When the compacted density of the positive electrode sheet is within the above range, it is beneficial to achieve higher energy density while taking into account the energy density and storage performance of the battery.

[0142] As used herein, "compacted density" has the meaning commonly understood in the art and is one of the reference indicators of the energy density of a material. In the present application, unless otherwise specified, the compacted density of the positive electrode sheet refers to the ratio of the mass of the positive electrode active material layer to its volume.

[0143] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein at least one of the positive electrode film layers comprises a positive electrode active material layer, and any one of the positive electrode active material layers independently contains a positive electrode active material. At least one of the positive electrode active material layers contains the positive electrode active material according to the first aspect of the present application.

[0144] By way of non-limiting example, the positive electrode current collector has two opposite surfaces in the thickness direction of the positive electrode current collector, and further, the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0145] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base material. Non-limiting examples of the metal material in the positive current collector can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. Non-limiting examples of the polymer material base material in the positive current collector can include one or more of a polypropylene (PP), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polystyrene (PS), a polyethylene (PE), and the like.

[0146] In some embodiments, the positive electrode film layer can further optionally include a binder. As non-limiting examples, the binder can include one or more of a polyvinylidene fluoride (PVDF), a polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0147] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0148] In some embodiments, the positive electrode tab can be prepared by dispersing the components described above for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive current collector; and drying, compacting (which can employ cold pressing), and the like, to obtain the positive electrode tab. The type of the solvent can be selected from, but is not limited to, any of the types described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The positive current collector surface on which the positive electrode slurry is coated can be a single surface of the positive current collector or both surfaces of the positive current collector.

[0149] In a third aspect, the present application provides a secondary battery including the positive electrode tab of the second aspect of the present application, and further including a negative electrode tab and a separator; wherein the separator is disposed between the positive electrode tab and the negative electrode tab.

[0150] The positive electrode tab of the secondary battery has a unique particle size distribution characteristic of the polycrystalline active particles and the single-crystal or single-crystal-like active particles, has superior storage performance, and can also maintain a good energy density.

[0151] In the present application, the secondary battery includes a positive electrode sheet (the positive electrode sheet provided in the second aspect of the present application), a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are inserted and de-inserted between the positive electrode sheet and the negative electrode sheet. The electrolyte has the function of conducting active 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 short circuit of the positive and negative electrodes, and at the same time, to allow the active ions to pass through.

[0152] The positive electrode sheet

[0153] The positive electrode sheet in the third aspect and the fourth aspect of the present application includes the positive electrode sheet provided in the second aspect of the present application.

[0154] In some embodiments of the present application, the secondary battery is a lithium ion secondary battery. The lithium ion secondary battery and the use of lithium ions realize the charging and discharging process through the insertion and de-insertion of the electrode and the transmission in the electrolyte. Generally, the active ion in the lithium ion secondary battery is lithium ion, but is not limited thereto.

[0155] The negative electrode sheet

[0156] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0157] As a non-limiting example, the negative electrode current collector has two opposite surfaces in the thickness direction of itself, and the negative electrode film layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector.

[0158] In some embodiments, the negative electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be obtained by forming a metal material on the polymer material base material. In the negative electrode current collector, non-limiting examples of the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the like. In the negative electrode current collector, non-limiting examples of the polymer material base material can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0159] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As non-limiting examples, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can be selected from elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0160] In some embodiments, the negative electrode film layer can also optionally include a binder. The binder can 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).

[0161] In some embodiments, the negative electrode film layer can also optionally include a conductive agent. The conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0162] In some embodiments, the negative electrode film layer can also optionally include other auxiliary agents, such as thickening agents, etc. Non-limiting examples of the thickening agent can include sodium carboxymethyl cellulose (CMC-Na), etc.

[0163] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (non-limiting examples of the solvent include deionized water), to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector (the surface coated with the negative electrode slurry can be a single surface or both surfaces), and then drying, compacting (the compacting can employ cold pressing), etc., to obtain the negative electrode sheet.

[0164] Electrolyte

[0165] The electrolyte has the function of conducting active ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a particular limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0166] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent. In a lithium ion secondary battery, the electrolyte salt can include an electrolyte lithium salt.

[0167] In some embodiments, the electrolyte lithium salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiCIO4), lithium hexafluoroarsenate, lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0168] In some embodiments, the solvent is an organic solvent.

[0169] In some embodiments, the organic solvent is an ester or an ether. In some of these embodiments, the organic solvent is an ester. Such ester solvents can include one or more of carbonates and halogenated carbonates, such as, by way of non-limiting example, one or more of 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), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), and a fluorinated version of any of the foregoing.

[0170] In some embodiments, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, 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.

[0171] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive that improves certain properties of the battery, such as an additive that improves overcharge performance of the battery, an additive that improves high or low temperature performance of the battery, and the like.

[0172] In some embodiments, the additive can include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), methylene methanedisulfonate (MMDS), 1-propene-1,3-sultone (PST), ethylene sulfite (ES), propylene sulfite (PS), vinyl sulfate (DTD), succinonitrile (SN), adiponitrile (AND), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)borate (TMSB), and anisole.

[0173] Separator film

[0174] In some embodiments, the secondary battery further includes a separator film. The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be used.

[0175] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0176] Electrode assembly, electrochemical energy storage device, secondary battery, and electric device

[0177] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly through a rolling process or a stacking process.

[0178] In some embodiments, the electrochemical energy storage device can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

[0179] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

[0180] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0181] The shape of the secondary battery is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 2 is a square structure secondary battery 5 as an example.

[0182] In some embodiments, referring to Figure 3 The outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by a person skilled in the art according to actual needs.

[0183] In a fourth aspect, the present application provides a power consuming device, which includes at least one of the positive electrode tab of the second aspect of the present application and the secondary battery of the third aspect of the present application.

[0184] The secondary battery can be used as a power source of the power consuming device, or as an energy storage unit of the power consuming device. The power consuming device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. The mobile device can be a mobile phone, a notebook computer, etc., for example; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0185] As the power consuming device, the secondary battery can be selected according to the use requirements thereof.

[0186] Figure 4 The power consuming device 6 is an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the power consuming device, a battery pack or a battery module can be used.

[0187] Another example of the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a secondary battery can be used as a power source.

[0188] In a fifth aspect, the present application provides a preparation method of a positive electrode active material, which can be used to prepare the positive electrode active material of the first aspect of the present application.

[0189] In some embodiments, a preparation method of a positive electrode active material is provided, which includes the following steps:

[0190] Preparation of first active particles and second active particles, respectively;

[0191] The first active particles and the second active particles are mixed to obtain the positive electrode active material of the first aspect of the present application.

[0192] In some embodiments, the first active particles are prepared by a method comprising the step of sintering precursor materials in accordance with the stoichiometric ratio of elements, the sintering temperature being 600-900℃, and further, the sintering time can be 8-15h, such as any one of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., and can also be selected from an interval formed by any two of the above-mentioned time lengths. The sintering temperature for preparing the first active particles (polycrystalline particles) can be 600-900℃, and can also be selected from any one of the following temperatures: 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, etc., and can also be selected from a temperature interval formed by any two of the foregoing temperatures, such as 750-850℃.

[0193] In some embodiments, the second active particles are prepared by a method comprising the step of sintering precursor materials in accordance with the stoichiometric ratio of elements, the sintering temperature being 700-1000℃, and further, the sintering time can be 8-15h, such as any one of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., and can also be selected from an interval formed by any two of the above-mentioned time lengths. The sintering temperature for preparing the second active particles (single-crystalline or single-crystalline-like particles) can be 700-1000℃, and can also be selected from any one of the following temperatures: 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, etc., and can also be selected from a temperature interval formed by any two of the foregoing temperatures, such as 650-800℃.

[0194] For those skilled in the art, according to the component design of the target element composition and content of the positive electrode active particles, targeted adjustments can be made on the basis of the conventional method for preparing active particle precursors in the art, so as to realize the component regulation of the precursors and the active particles prepared therefrom. In addition, by adjusting the element composition in the precursor solution and controlling the sintering temperature, the size of the active particles can be regulated to a certain extent, such as the regulation of D v 90、D v 50、D v 10, etc. particle size distribution parameters.

[0195] By controlling the sintering parameters of the positive electrode active material, the unique particle size distribution characteristics of the polycrystalline active particles and the single-crystalline or single-crystalline-like active particles can be regulated.

[0196] When the positive active particles are provided with the coating layer on at least a part of the surface of the active particle body, the positive active particles with the coating layer can be prepared by a step sintering method. The body precursor material can be first sintered to obtain the body of the positive active particles, and then the coating layer precursor material is coated on at least a part of the surface of the body, and then sintered for the second time, so as to obtain the positive active particles with the coating layer. It is easy for those skilled in the art to obtain or screen the positive active particles with the target structure by adjusting the preparation parameters.

[0197] In a sixth aspect, the present application provides a preparation method of a positive electrode slurry, comprising the following steps: mixing the positive active material according to the first aspect of the present application and a solvent to prepare a positive electrode slurry; wherein the positive electrode slurry is added with or without an auxiliary agent;

[0198] The first active particles can be prepared by the method described in the fifth aspect of the present application.

[0199] The second active particles can be prepared by the method described in the fifth aspect of the present application.

[0200] The auxiliary agent includes one or more of a conductive agent and a binder.

[0201] Hereinafter, some embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the technology or condition is not specified in the embodiments, it is performed according to the description in the foregoing, or according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by market purchase, or can be synthesized by market products according to the conventional method.

[0202] Preparation method of positive active material

[0203] 1. Preparation of first active particles (polycrystalline active particles)

[0204] At 50°C to 55°C, nickel sulfate, manganese sulfate and cobalt sulfate are prepared into a 1 mol / L solution according to the molar ratio, the solvent is deionized water, and ammonia water, sodium hydroxide and other hydroxides are added for co-precipitation technology to prepare polycrystalline precursors, and particle size testing is performed to confirm whether the preset requirements are met; during the preparation of the polycrystalline precursor, the particle size of the precursor can be controlled by controlling the reaction time, the pH value during co-precipitation and the ammonia concentration.

[0205] The polycrystalline precursor Ni 0.9 Co 0.02 Mn 0.08Ni(OH)2, Co(OH)2, Mn(OH)2, LiOH H2O are mixed in a suitable molar ratio (1:1.08), and then sintered in an atmosphere furnace at 650-800°C (800°C in this example) for 8-15 h in an oxygen atmosphere. After cooling, the polycrystalline active particles, i.e. the first active particles, are obtained by mechanical grinding.

[0206] 2. Preparation of the second active particles (single-crystal active particles in this example)

[0207] At 50-55°C, a 1 mol / L solution of NiSO4, MnSO4 and CoSO4 is prepared in deionized water in a molar ratio, and ammonia, sodium hydroxide and other hydroxides are added for co-precipitation to obtain single-crystal precursors. The particle size of the single-crystal precursors is determined by controlling the reaction time, pH value and ammonia concentration during co-precipitation.

[0208] The single-crystal precursor Ni 0.9 Co 0.02 Mn 0.08 (OH)2, LiOH H2O are mixed in a suitable molar ratio, and then sintered in an atmosphere furnace at 750-850°C (850°C in this example) for 8-15 h in an oxygen atmosphere. After cooling, the single-crystal active particles, i.e. the second active particles, are obtained by mechanical grinding.

[0209] After sintering, the particle size of the active particles obtained by the conversion of the precursor particles increases slightly. Therefore, the particle size of the precursor is slightly smaller than that of the corresponding active particles after sintering.

[0210] When at least part of the surface of the polycrystalline active particles or single-crystal active particles is provided with a coating layer, the precursor material can be first sintered to obtain the positive active particle body, and then mixed uniformly with the coating layer raw material, and then sintered in a suitable gas atmosphere to form the coating layer on at least part of the surface of the active particle body.

[0211] 3. Preparation of the positive active material

[0212] The polycrystalline active particles (first active particles) and single-crystal active particles (second active particles) prepared as described above are mixed in a certain weight ratio to obtain the positive active material.

[0213] The following Example 1 is taken as an example, in which the polycrystalline particles D v 50 are 9 μm, the (D v 90-D v 10) / D v 50 is 0.4, and the single-crystal particle Dv 50 is 3.3 pm, single crystal particles (D v 90-D v 10) / D v 50 is 1.6. That is, X1 / X2 can be calculated as 0.25. Please refer to Table 1.

[0214] Test analysis method

[0215] 1. Test analysis of particle size

[0216] (1) Particle size test

[0217] Sample preparation: prepared positive electrode active material; can also be the positive electrode active material in the positive electrode active material layer of the positive electrode sheet. In order to avoid the influence of agglomeration in the drying process on the test of particle size, the wet sample after washing is taken for dispersion test.

[0218] Particle size type: D v 10, D v 50 and D v 90 test.

[0219] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009.

[0220] Test procedure: take the appropriate amount of sample to be tested (the sample concentration can be guaranteed to 8%~12% obscuration), add 20 mL of anhydrous ethanol, ultrasonic treatment for 5 min (53KHz / 120W), ensure that the sample is completely dispersed, and then determine the sample according to GB / T19077-2016 / ISO13320:2009 standard.

[0221] (2) X1 / X2

[0222] As known from the foregoing, in the present application, the polycrystalline active particles in the positive electrode active material are referred to as first active particles, and the single crystal or single crystal-like active particles in the positive electrode active material are referred to as second active particles. Among them, the particle size parameter (D v 90-D v 10) / D v 50 of the first active particles is X1, and the particle size parameter (D v 90-D v 10) / D v 50 of the second active particles is X2.

[0223] 2. Test method of electrode sheet compaction density

[0224] The pole piece is cut into a 1000 mm long film piece; the positive pole piece is rolled under appropriate pressure, and since the aluminum foil has ductility, the film piece length is 1006 mm (the ductility is 0.6%); a 1540.25 mm 2 small disc (the area is denoted as A) is punched out, the weight W and the thickness d of the small disc are measured, the weight W1 and the thickness d1 of the positive current collector in the small disc are deducted, the weight W2 and the thickness d2 of the positive active material layer are obtained, and the pole piece compaction density is calculated according to the ratio W2 / (A·d2).

[0225] The test results can be seen in Table 3.

[0226] 3. Performance of the battery cell or battery

[0227] (1) Test method of battery capacity

[0228] The lithium ion battery is placed in a constant temperature environment at 25℃ for 2h, then charged at 0.33C to 4.2V, then charged at 4.2V until the current is less than or equal to 0.05C, and then discharged at 0.33C to 2.8V, and the initial capacity C0 of the lithium ion battery is recorded.

[0229] The test results can be seen in Table 3.

[0230] (2) Test method of high-temperature storage performance of the battery

[0231] The battery is placed in a constant temperature oven at 60℃ for 100 days, then discharged at 0.33C to 2.8V at 25℃, then charged at 0.33C to 4.2V, then charged at 4.2V until the current is less than or equal to 0.05C, and then discharged at 0.33C to 2.8V, and the capacity C1 of the lithium ion battery is recorded. The capacity retention rate of the battery (%) = C1 / C0 x 100%.

[0232] The test results can be seen in Table 3.

[0233] Example 1.

[0234] 1. Preparation of the positive active material

[0235] According to the preparation parameters shown in Table 1 and Table 2, the first active particle and the second active particle are prepared in sequence by using the preparation method of the positive active material.

[0236] The first active particle and the second active particle are mixed to obtain the positive active material of this example.

[0237] 2. Preparation of the positive pole piece

[0238] The positive electrode active material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:2:1 and added into a solvent N-methyl pyrrolidone (NMP) to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on both sides of a positive electrode current collector aluminum foil, dried at 85°C, cold-pressed, and then subjected to die cutting and slitting to prepare a lithium ion battery positive electrode sheet.

[0239] 3. Preparation of the negative electrode sheet

[0240] The negative electrode active material graphite, silicon oxide, the conductive agent acetylene black, the thickening agent sodium hydroxymethyl cellulose (CMC-Na), and the binder styrene butadiene rubber (SBR) are added into a solvent water in a mass ratio of 72:24:2:1:1 and mixed uniformly to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on both sides of a negative electrode current collector copper foil, dried at 85°C, and then cold-pressed to prepare a lithium ion battery negative electrode sheet.

[0241] 4. Preparation of the separator

[0242] The polyethylene microporous film is used as a porous separator film substrate, inorganic aluminum oxide powder and polyvinylpyrrolidone acetone solvent are mixed uniformly in a weight ratio of 3:1.5:5.5 to prepare a slurry, which is coated on one side of the substrate and dried to obtain a separator film.

[0243] 5. Preparation of the electrolyte

[0244] Lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate is 1:2:1) to obtain a lithium ion battery electrolyte.

[0245] 6. Preparation of the battery

[0246] The above-mentioned positive electrode sheet, negative electrode sheet, and separator film are wound to obtain a bare cell, and then the bare cell is subjected to packaging, liquid injection, formation, and exhaust processes to obtain a secondary battery of Example 1, which is a lithium ion battery.

[0247] Examples 2-10. The preparation methods of the first active particles, the second active particles, the positive electrode active material, the positive electrode sheet, and the secondary battery are basically the same as those of Example 1, and the chemical composition, particle size and distribution, and active particle content of the active particles can be controlled according to Table 1 and Table 2, and the preparation parameters of the active particles can be appropriately adjusted according to the parameters in Table 1.

[0248] Comparative Example 1-2. The preparation method of the first active particle, the second active particle, the positive active material, the positive electrode sheet, and the secondary battery is basically the same as in Example 1, and the chemical composition, particle size and distribution, and active particle content of the active particle can be controlled according to Tables 1 and 2, and the preparation parameters of the active particle can be appropriately adjusted according to the parameters in Table 1.

[0249] Table 1.

[0250]

[0251] Table 2.

[0252]

[0253] In Table 2:

[0254] (1) R W is the percentage of the weight of the first active particle relative to the sum of the weights of the first active particle and the second active particle;

[0255] (2) R Dv50 is the D v 50 ratio of the first active particle to the second active particle;

[0256] (3) X1 is the (D v 90-D v 10) / D v 50 of the first active particle, and X2 is the (D v 90-D v 10) / D v 50 of the second active particle.

[0257] Test results and analysis

[0258] The parameters and performance test results of the above examples and comparative examples can be referred to Table 3.

[0259] Examples 1-10 all have excellent high-temperature storage performance, with a capacity retention rate of more than 93% after 100 days of storage at 60°C, a long high-temperature storage life, and also maintain good compaction density and battery capacity, meaning good energy density.

[0260] The X1 / X2 of Comparative Example 1 is too high, and the X1 / X2 of Comparative Example 2 is too low, both of which result in the inability to balance the high-temperature storage performance, compaction density, and initial capacity, i.e., the inability to balance the dual requirements of battery storage life and energy density. The high-temperature storage performance in Comparative Example 1 deteriorates; the improvement of the high-temperature storage performance in Comparative Example 2 is at the expense of a serious decline in energy density, with a serious decline in compaction density.

[0261] Table 3.

[0262]

[0263] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, but it is understood that any combination of the technical features is within the scope of the present disclosure as long as the combination does not result in a contradiction.

[0264] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and exerting the same effects as the technical idea of the present application are included in the technical scope of the present application. The above-described embodiments merely express several embodiments of the present application, and the description is relatively detailed, but the present application should not be construed as being limited to the scope of the patent. Furthermore, within the scope of the present application, various modifications that can be thought of by those skilled in the art, other modes of implementation obtained by combining some of the constituent elements of the embodiments, and the like are also included in the scope of the present application. Note that it should be noted that several modifications and improvements that can be thought of by those skilled in the art without departing from the concept of the present application are included in the scope of the present application. Therefore, the scope of the present application should be determined based on the claims, and the description and drawings are used to interpret the claims.

Claims

1. A positive electrode active material, comprising a first active particle and a second active particle; wherein, The first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X1; the second active particle is a single crystal or near-single crystal particle in the positive electrode active material, and its particle size parameter (D) v 90-D v 10) / D v 50 is denoted as X2; X1 / X2 satisfies 0.2≤X1 / X2≤0.7; The particle size of the first active particle is larger than that of the second active particle; in the particle size distribution curve of the positive electrode active material, the first active particle and the second active particle correspond to two discontinuous independent peaks respectively. The D of the first active particle v 50 satisfies 7 μm≤D v 50≤15 μm, or, the D of the second active particle v 50 satisfies 1 μm ≤ D v 50≤6 μm; where, D v 90. D v 50 and D v 10 represents the particle size corresponding to the cumulative volume distribution percentage of the multi-particle combination reaching 90%, 50%, and 10%, respectively.

2. The positive electrode active material according to claim 1, wherein, The particle size distribution curve of the positive electrode active material has exactly two peaks.

3. The positive electrode active material according to claim 1 or 2, wherein, The D of the first active particle v 50 satisfies 7 μm≤D v 50≤10 μm; Optionally, the D of the first active particle v 50 satisfies 7 μm≤D v 50 < 10 μm; Optionally, the D of the first active particle v 50 satisfies 8 μm≤D v 50≤10 μm.

4. The positive electrode active material according to claim 3, wherein, The D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2≤R Dv50 ≤4.

5. The positive electrode active material according to claim 3, wherein, The second active particle's D v 50 satisfies 1 μm ≤ D v 50≤5 μm; Optionally, the D of the second active particle v 50 satisfies 1 μm ≤ D v 50≤4 μm; Optionally, the D of the second active particle v 50 satisfies 2 μm≤D v 50≤3.5 μm; Optionally, the D of the second active particle v 50 satisfies 2.5 μm ≤ D v 50≤3.5 μm.

6. The positive electrode active material according to any one of claims 1 to 5, wherein, The ratio X1 / X2 satisfies 0.2 ≤ X1 / X2 ≤ 0.6; Optionally, X1 / X2 satisfies 0.2≤X1 / X2≤0.55; Optionally, X1 / X2 satisfies 0.25≤X1 / X2≤0.

55.

7. The positive electrode active material according to any one of claims 1 to 6, wherein, The first active particle satisfies 0.3 ≤ X1 ≤ 1.0; Optionally, the first active particle satisfies 0.4 ≤ X1 ≤ 0.8; Further optionally, the first active particle satisfies 0.3≤X1≤0.

45.

8. The positive electrode active material according to any one of claims 1 to 7, wherein, The second active particle satisfies 0.7 ≤ X2 ≤ 2.5; Optionally, the second active particle satisfies 0.7≤X2≤2, and more preferably, 0.7≤X2≤1.5; Further optionally, the second active particle satisfies 0.8 ≤ X2 ≤ 1.

6.

9. The positive electrode active material according to any one of claims 1 to 8, wherein, The D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2.2≤R Dv50 ≤4; Optionally, the D of the first active particle v 50 and the D of the second active particle v The ratio R of 50 Dv50 Satisfying 2.3≤R Dv50 ≤4.0; Alternatively, 2.5 ≤ R Dv50 ≤3.0; further alternatively, 2.5≤R Dv50 ≤2.

8.

10. The positive electrode active material according to any one of claims 1 to 9, wherein, The primary particles constituting the polycrystalline particles have a particle size of 100nm to 800nm.

11. The positive electrode active material according to any one of claims 1 to 10, wherein, The ratio R of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle. W Satisfying 0.5≤R W ≤0.9; Optionally, the ratio R of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle is... W Satisfying 0.5≤R W ≤0.8; Alternatively, 0.6 ≤ R W ≤0.

8.

12. The positive electrode active material according to any one of claims 1 to 11, wherein, The first active particle and the second active particle are each independently an oxide material containing lithium and nickel. Optionally, the amount of nickel and lithium in the first active particle is higher than that in R. Ni / Li The ratio of nickel to lithium in the second active particle R Ni / Li Each independently ≥0.65; Further optionally, the amount of nickel and lithium elements in the first active particle is higher than that in R. Ni / Li The ratio of nickel to lithium in the second active particle R Ni / Li Each independently satisfies 0.65≤R Ni / Li ≤1.1; Alternatively, the amount of nickel and lithium elements in the first active particle is greater than that in R. Ni / Li The ratio of nickel to lithium in the second active particle R Ni / Li Each independently satisfies 0.8≤R Ni / Li ≤1.0; Alternatively, the amount of nickel and lithium elements in the first active particle is greater than that in R. Ni / Li The ratio of nickel to lithium in the second active particle R Ni / Li Each independently satisfies 0.8≤R Ni / Li ≤0.

95.

13. The positive electrode active material according to any one of claims 1 to 12, wherein, The first active particle and the second active particle are each independently a ternary material or a ternary material containing doped and / or coated elements; Optionally, the first active particle and the second active particle are each independently an NCM ternary material, an NCA ternary material, an NCM ternary material containing doped and / or coated elements, or an NCA ternary material containing doped and / or coated elements. Optionally, the first active particle and the second active particle each independently comprise the following element combination Li x (Ni a Co b M c M' d O2, wherein 0.9≤x≤1.2, 0.8≤a<1, 0<b<1, 0<c<1, a+b+c+d=1, M includes at least one of Mn and Al, and M' includes one or more of Na, K, Ca, Ba, Sb, Ti, Zr, W, Sr, Nb, Mo, Si, Mg, B, Cr and Ta.

14. The positive electrode active material according to claim 12 or 13, wherein, The ratio of nickel to lithium in the first active particle to R Ni / Li The ratio of nickel to lithium in the second active particle is less than R. Ni / Li ; Optionally, the ratio of the amount of nickel and lithium elements in the second active particle to that in the first active particle is R Ni / Li The difference ΔR Ni / Li Satisfying 0 < ΔR Ni / Li ≤0.05; Further, optionally, 0.01 < ΔR Ni / Li ≤0.

05.

15. A positive electrode sheet comprising a positive active material layer, said positive active material layer comprising the positive active material according to any one of claims 1 to 14.

16. The positive electrode sheet according to claim 15, wherein, The compaction density of the positive electrode sheet is 3.2~3.8 g / cm³. 3 ; Optionally, the compaction density of the positive electrode sheet is 3.4~3.7 g / cm³. 3 .

17. A secondary battery comprising the positive electrode sheet as described in claim 15 or 16, further comprising a negative electrode sheet and a separator; wherein, The separator is disposed between the positive electrode and the negative electrode.

18. An electrical device comprising at least one of the positive electrode sheet of claim 15 or 16 and the secondary battery of claim 17.

19. A method for preparing a positive electrode active material, comprising the following steps: First active particles and second active particles were prepared separately. The first active particle and the second active particle are mixed to obtain the positive electrode active material according to any one of claims 1 to 14; in, The first active particles are prepared by a method including the following steps: sintering precursor materials that meet the elemental stoichiometric ratio at a sintering temperature of 600~900℃ and a sintering time of 8~15h. The second active particles are prepared by a method including the following steps: sintering precursor materials that meet the elemental stoichiometric ratio at a sintering temperature of 700~1000℃ and a sintering time of 8~15h.

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