Positive electrode active material and method for producing the positive electrode active material, positive electrode strip, battery, and electric device

Abstract

A positive electrode active material, a method for producing the positive electrode active material, a positive electrode sheet, a battery, and an electric device. The positive electrode active material includes a core containing Lia1Nix1My1M’z1Om1Rn1, where 0.9 ≦ a1 ≦ 1.1, 0.6 ≦ x1 < 1, 0 ≦ y1 ≦ 0.4, 0 < z1 ≦ 0.01, 1.9 ≦ m1 ≦ 2.2, 0 ≦ n1 ≦ 0.1, M contains at least one of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, Ce, M’ contains at least one of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti or Ga, R contains at least one of F, Cl or S, a core, an intermediate layer covering at least a part of the outer surface of the core and having a porous structure, and an outer shell layer covering at least a part of the outer surface of the intermediate layer and containing Lia2Nix2My2M’z2Om2Rn2, where 0.9 ≦ a2 ≦ 1.1, 0.6 ≦ x2 < 1, 0 ≦ y2 ≦ 0.4, 0 ≦ z2 ≦ 0.01, 1.9 ≦ m2 ≦ 2.2, 0 ≦ n2 ≦ 0.1.

Description

Technical Field

[0001] This application relates to the field of batteries, and specifically to a positive electrode active material, a method for manufacturing the positive electrode active material, a positive electrode sheet, a battery, and an electrical device.

Background Art

[0002] As an energy storage device, batteries are widely applied in various fields. Taking lithium-ion batteries as an example, they are eco-friendly, have features such as high energy and low carbon, and are not only applicable to energy storage power systems such as hydroelectric power generation, thermal power generation, wind power generation, and solar power generation plants, but also widely applied to many fields such as electric bicycles, electric motorcycles, electric vehicles, ships and other electric transportation means, as well as military equipment and aerospace. With the development of society, people's requirements for batteries are also increasing.

Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application aims to provide a positive electrode active material, improve the volume stability of the positive electrode active material during the charge and discharge process, and improve the cycle performance of the battery.

[0004] To achieve the above object, the first aspect of this application provides a positive electrode active material, which is a core containing Li a1 Ni x1 M y1 M’ z1 O m1 R n1 where 0.9 ≦ a1 ≦ 1.1, 0.6 ≦ x1 < 1, 0 ≦ y1 ≦ 0.4, 0 < z1 ≦ 0.01, 1.9 ≦ m1 ≦ 2.2, 0 ≦ n1 ≦ 0.1, M contains at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, Ce, M’ contains at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti or Ga, and R contains at least one element of F, Cl or S, and an intermediate layer that covers at least a part of the outer surface of the above core and has a porous structure, and The outer surface of at least a part of the intermediate layer is covered with Li a2 Ni x2 M y2 M' z2 O m2 R n2 and an outer shell layer comprising: 0.9≦a2≦1.1, 0.6≦x2<1, 0≦y2≦0.4, 0≦z2≦0.01, 1.9≦m2≦2.2, and 0≦n2≦0.1.

[0005] The positive electrode active material of the present application has the following beneficial effects: high-nickel layered positive electrode active materials are prone to relatively large volume deformation during charge and discharge, which can lead to internal cracks and the risk of these cracks extending to the surface of the positive electrode active material particles. Doping the positive electrode active material located in the core with element M' is beneficial to improving the volume stability of the core of the positive electrode active material during charge and discharge and reducing the risk of internal cracks within the positive electrode active material particles. At the same time, installing an intermediate layer with a porous structure between the core and the outer shell layer buffers the volume deformation and stress accumulation of the core, and is beneficial to inhibit internal cracks within the positive electrode active material particles and their extension to the surface. This reduces the risk of cracks within the positive electrode active material particles during charge and discharge cycles, and improves their volume stability and cycle performance.

[0006] In some embodiments of the present application, the intermediate layer is M'' p O q where 1≦p≦2, 2≦q≦3, and M″ includes at least one element of B, Al, or Si. Satisfying the predetermined condition is advantageous, on the one hand, in reducing the risk that the intermediate layer material may adversely affect the electrochemical performance of the positive electrode active material, and, on the other hand, in reducing the risk that M″ p O q In combination with the formation method of (1), it is advantageous to form an intermediate layer having a porous structure in the positive electrode active material, which is advantageous in achieving both the electrochemical performance and the cycle stability of the positive electrode active material.

[0007] In some embodiments of the present application, the ratio of the number of moles of M″ element to the number of moles of Li element in the positive electrode active material is (0.005-0.02):(0.9-1.1). Controlling the relative amounts of M″ element and Li element used to satisfy a predetermined range is advantageous for further achieving both high specific capacity and cycle stability of the positive electrode active material.

[0008] In some embodiments of the present application, in the positive electrode active material, the ratio of the number of moles of M″ element to the number of moles of Li element is (0.008-0.012):(0.9-1.1).

[0009] In some embodiments of the present application, z2 > 0. It is advantageous for the outer shell layer to satisfy certain conditions to further improve the cycle stability of the positive electrode active material.

[0010] In some embodiments of the present application, the core comprises Li a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 and / or the outer shell layer is Li a2 Ni x2 Co y21 Mn y22 M' z2 O m2 R n2 where 0≦y21≦0.2, 0≦y22≦0.2, and y21 and y22 are not simultaneously 0. Satisfying the predetermined conditions is advantageous for achieving both high specific capacity and good cycle performance of the lithium battery.

[0011] In some embodiments of the present application, 0.002≦z1≦0.008 and / or 0.002≦z2≦0.008. Controlling the values ​​of z1 and z2 to satisfy the predetermined range conditions is also advantageous in reducing the risk that M′ doping may cause a deterioration in the electrochemical performance of the positive electrode active material.

[0012] In some embodiments of the present application, the particle diameter of the positive electrode active material is D1, the distance from the inner surface of the intermediate layer to the center of the core is 0.3D1 or more, and the distance from the outer surface of the intermediate layer to the center of the core is 0.4D1 or less. Satisfying these conditions is not only advantageous for improving the risk of cracking during cycling of the positive electrode active material, but also for reducing adverse effects on ion migration rate and volumetric energy density, and is advantageous for further achieving both cycle performance, rate performance, and energy density of the positive electrode active material.

[0013] In some embodiments of the present application, the particle diameter of the positive electrode active material is D1, and the thickness of the intermediate layer is 0.05D1 to 0.0625D1. Satisfying these conditions is not only advantageous for reducing the risk of cracking of the positive electrode active material during cycling, but also for reducing adverse effects on ion migration rate and volumetric energy density, and is advantageous for further achieving both cycle performance, rate performance, and energy density of the positive electrode active material.

[0014]

number

[0015] In some embodiments of the present application, the volume average particle diameter Dv50 of the positive electrode active material is 6 μm to 18 μm. Meeting the predetermined conditions is not only beneficial to improving the stability of the overall particle structure of the positive electrode active material, but also beneficial to endowing the positive electrode active material with the advantages of a small internal conduction distance and fewer surface side reactions, thereby further improving the electrochemical performance of the positive electrode active material.

[0016] A second aspect of the present application provides a method for producing a positive electrode active material, mixing core raw materials including a nickel source, an M source, and an M' source to obtain a mixed solution, and performing a first precipitation reaction on the obtained mixed solution to obtain first particles; mixing the first particles with a solution formed using the intermediate layer raw material to perform a second precipitation reaction to obtain second particles; Mix the outer shell layer raw materials containing a nickel source and an M source, mix the obtained mixed solution with the above second particles, and perform a third precipitation reaction to obtain precursor particles, mix the above precursor particles with a lithium source and sinter them to obtain a positive electrode active material, The precipitation product formed on the outer surface of the above first particles by the above second precipitation reaction forms a porous structure by the above sintering, The positive electrode active material is, Li a1 Ni x1 M y1 M’ z1 O m1 R n1 a core containing, where 0.9 ≦ a1 ≦ 1.1, 0.6 ≦ x1 < 1, 0 ≦ y1 ≦ 0.4, 0 < z1 ≦ 0.01, 1.9 ≦ m1 ≦ 2.2, 0 ≦ n1 ≦ 0.1, M contains at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, Ce, M’ contains at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti or Ga, and R contains at least one element of F, Cl or S, an intermediate layer covering at least a part of the outer surface of the above core and having a porous structure, an outer shell layer covering at least a part of the outer surface of the above intermediate layer and containing Li a2 Ni x2 M y2 M’ z2 O m2 R n2 where 0.9 ≦ a2 ≦ 1.1, 0.6 ≦ x2 < 1, 0 ≦ y2 ≦ 0.4, 0 ≦ z2 ≦ 0.01, 1.9 ≦ m2 ≦ 2.2, 0 ≦ n2 ≦ 0.1,

[0017] The method for manufacturing the positive electrode active material of the present application has the following beneficial effects: a core containing Li a1 Ni x1 M y1 M’ z1 O m1 R n1 and an outer shell layer containing Li a2 Ni x2 M y2 M’ z2O m2 R n2 and a positive electrode active material in which the intermediate layer has a porous structure, can be produced, and the feasibility of operation is high and the raw material composition and structural parameters of each layer are easy to control.

[0018] In some embodiments of the present application, the intermediate layer source comprises an M'' source including a compound having at least one element of B, Al, or Si.

[0019] A third aspect of the present application provides a positive electrode piece comprising the positive electrode active material of the first aspect of the present application or a positive electrode active material produced using the production method of the second aspect of the present application.

[0020] A fourth aspect of the present application provides a battery including the positive electrode piece of the third aspect of the present application.

[0021] A fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application.

[0022] Additional aspects and advantages of the present application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present application. [Brief explanation of the drawings]

[0023] The above and / or additional aspects and advantages of the present application will become more apparent and understandable from the following detailed description of the embodiments with reference to the accompanying drawings. [Figure 1] FIG. 2 is a schematic diagram of a cross section of a positive electrode active material secondary particle according to an embodiment of the present application. [Figure 2] 2 is a scanning electron microscope image of a cross section of a secondary particle of a positive electrode active material in an active material layer of a positive electrode piece according to Example 1 of the present application. FIG. [Figure 3] FIG. 2 is a scanning electron microscope image of a cross section of a secondary particle of a positive electrode active material in an active material layer of a positive electrode piece according to Comparative Example 2 of the present application. [Figure 4] 1 is a structural schematic diagram of a battery according to an embodiment of the present application; [Figure 5]1 is a structural schematic diagram of a battery module according to an embodiment of the present application; [Figure 6] 1 is a structural schematic diagram of a battery pack according to an embodiment of the present application; [Figure 7] FIG. 1 is an exploded view of a battery pack according to an embodiment of the present application. [Figure 8] 1 is a schematic diagram of an embodiment of an electrical device that uses a battery as a power source in accordance with an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present application will now be further described with reference to specific embodiments, it being understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0025] Hereinafter, with reference to the drawings as appropriate, embodiments of the positive electrode active material and its manufacturing method, positive electrode strip, battery, and electric device specifically disclosed in the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of already well-known matters and repeated description of substantially the same structure may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the scope of the claims.

[0026] The "ranges" disclosed herein may be defined by a lower limit and / or an upper limit; a given range may be defined by selecting one lower limit and / or one upper limit, and the selected lower and / or upper limits define the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of their endpoints, and may be arbitrarily combinable; i.e., any lower limit may be combined with any upper limit to form an open range, and any lower limit may be combined with any other lower limit to form an open range, and similarly, any upper limit may be combined with any other upper limit to form an open range. Furthermore, each point or individual value disclosed individually may itself be combined with any other point or individual value, as a lower or upper limit, to form an explicitly unspecified range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that the ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, when minimum range values ​​1 and 2 are recited and maximum range values ​​3, 4, and 5 are recited, all of the following ranges are contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. Unless otherwise specified, the numerical range "a to b" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are recited in the text, and "0 to 5" is simply a shorthand notation for this combination of numbers. Furthermore, when a parameter is described as an integer ≧2, this is equivalent to disclosing that the parameter is an integer, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0028] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0029] Unless otherwise specified, all steps in the present application may be performed sequentially or randomly, but are preferably performed sequentially. For example, a description of a method including steps S1 and S2 means that the method may include sequential steps S1 and S2, or sequential steps S2 and S1. For example, a description of a method that may further include step S3 means that step S3 can be added to the method in any order. For example, the method may include steps S1, S2, and S3, or steps S1, S3, and S2, or steps S3, S1, and S2, etc.

[0030] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open or closed. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0031] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, 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).

[0032] Unless otherwise specified, the term "and / or" in this application is simply a relational relationship that describes related objects and indicates that three types of relationships can exist. For example, A and / or B can represent three situations: the presence of only A, the simultaneous presence of A and B, and the presence of only B. Furthermore, the symbol " / " in this specification generally indicates that the related objects before and after it are in an "or" relationship.

[0033] As used herein, the terms "plurality" and "multiple species" mean two or more than two.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The terms "comprises" and "includes" and any variations thereof in the specification, claims, and description of the drawings of the present application are intended to cover a non-exclusive inclusion. Unless otherwise specified, terms used herein have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter referred to in the present application can be measured using various test methods commonly used in the art (for example, they can be measured according to the test methods shown in the examples of the present application).

[0035] With the advancement of eco-friendly and environmentally friendly themes, the application of lithium-ion batteries has already penetrated deeply into all aspects of life, including vehicles, electronic devices, and energy storage devices. However, as the application of batteries continues to advance, people's demands for batteries are also increasing. Among them, high-nickel layered positive electrode active materials generally experience serious volume deformation during charge-discharge cycles, which causes a large accumulation of internal stress in the material. If the accumulation of internal stress in the material is too high, cracks will occur inside the material. If the cracks extend to the surface of the positive electrode active material, the electrolyte will penetrate into the positive electrode active material in large quantities, affecting its performance. Currently, porous structures are often used to solve this problem. However, in conventional positive electrode active materials, the pores are usually uniformly distributed within the secondary particles of the material. The large amount of pores exacerbates the erosion of the material by the electrolyte, thereby affecting the cycling performance of the material.

[0036] In the present application, the structure of the positive electrode active material particles is improved to form a multilayer structure having, from the inside to the outside, a core, an intermediate layer, and an outer shell layer, in that order. The nickel-containing positive electrode active material located in the core is doped with an M' element (including at least one of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti, and Ga). This improves the volume stability of the core positive electrode active material during charge and discharge, reducing the risk of cracking inside the positive electrode active material particles. At the same time, a porous structure is formed in the intermediate layer, which can accommodate volume deformation and stress accumulation inside the positive electrode active material particles and prevent cracks inside the positive electrode active material particles from extending to the surface. This improves the volume stability of the positive electrode active material particles, reduces the risk of cracking during charge and discharge cycles, and further improves their cycle performance.

[0037] The cathode active material disclosed in the embodiments of the present application can be applied to secondary batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical devices powered by the batteries and various energy storage systems using the batteries as energy storage elements. The electrical devices include, but are not limited to, mobile phones, tablets, notebook computers, electric toys, power tools, electric scooters, electric vehicles, ships, aircraft, etc. Among them, the electric toys may include stationary or mobile electric toys, such as game machines, electric vehicle toys, electric ship toys, and electric airplane toys, and the aircraft may include airplanes, rockets, space shuttles, spacecraft, etc.

[0038] The first aspect of the present application provides a cathode active material, including a core, an intermediate layer, and an outer shell layer, where the core contains Li a1 Ni x1 M y1 M’ z1 O m1 R n1 and 0.9 ≦ a1 ≦ 1.1, 0.6 ≦ x1 < 1, 0 ≦ y1 ≦ 0.4, 0 < z1 ≦ 0.01, 1.9 ≦ m1 ≦ 2.2, 0 ≦ n1 ≦ 0.1, M contains at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, Ce, M’ contains at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti or Ga, R contains at least one element of F, Cl or S, the intermediate layer covers at least a part of the outer surface of the core and has a porous structure, the outer shell layer covers at least a part of the outer surface of the intermediate layer, and Li a2 Ni x2 M y2 M’ z2 O m2 R n2 and 0.9 ≦ a2 ≦ 1.1, 0.6 ≦ x2 < 1, 0 ≦ y2 ≦ 0.4, 0 ≦ z2 ≦ 0.01, 1.9 ≦ m2 ≦ 2.2, 0 ≦ n*2* ≦ 0.1.

[0039] It should be noted that in the original text, there is a possible error in line where "n2" is likely a miswriting of "n1" as it is not consistent with the previous description. I translated it as "n*2*" to show the potential issue. If this is not an error, please provide more context or clarify.For example, the values ​​of a1 and a2 may each independently be 0.9, 0.95, 1, 1.05, 1.1, etc., or may be any range of the above values. The values ​​of x1 and x2 may each independently be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, etc., or may be any range of the above values. The values ​​of y1 and y2 may each independently be 0, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, etc., or may be any range of the above values. The values ​​of z1 and z2 may each independently be 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, etc., or may be any range of the above values. The values ​​of m1 and m2 may each independently be 1.9, 1.92, 1.95, 1.98, 2, 2.02, 2.05, 2.08, 2.1, 2.12, 2.15, 2.18, 2.2, etc., or may be any range of the above values. The values ​​of n1 and n2 may each independently be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, etc., or may be any range of the above values. Optionally, x1 + y1 + z1 = 1 and / or x2 + y2 + z2 = 1. The values ​​of x1, x2, y1, y2, z1 and z2 satisfy the requirements of a predetermined range, which is advantageous not only for obtaining a high specific capacity but also for obtaining a relatively good cycle performance.

[0040] As can be seen from FIG. 1, the positive electrode active material includes a core 11, an intermediate layer 12, and an outer shell layer 13. The core 11 is Li a1 Ni x1 M y1 M' z1 O m1 R n1 wherein z1>0, the intermediate layer 12 covers at least a part of the outer surface of the core 11, the outer shell layer 13 covers at least a part of the outer surface of the intermediate layer 12, and the outer shell layer is Lia2 Ni x2 M y2 M' z2 O m2 R n2 and z2≧0, i.e., the nickel-containing positive electrode active material located in the outer shell layer may or may not be doped with the M' element, and the intermediate layer 12 has a porous structure. Doping the nickel-containing positive electrode active material located in the core 11 with the M' element is advantageous in improving the volume stability of the core of the positive electrode active material during the charge and discharge process and reducing the risk of cracking inside the positive electrode active material particles. The doped M' element is usually not involved in the electrochemical reaction during the charge and discharge cycle, and the relatively strong M'-O bonding action can restrain the unstable oxygen structure framework caused by the valence change of the Ni element during the charge and discharge process, further improving the stability of the layered structure inside the material and preventing the positive electrode active material from cracking during the cycle process. This reduces the risk of irreversible phase change and inhibits the collapse of the porous structure of the positive electrode active material in the later stages of cycling. At the same time, by placing the intermediate layer 12 with a porous structure between the core 11 and the outer shell layer 13, the intermediate layer can achieve a large porosity, which is advantageous for buffering the volume deformation and stress accumulation of the core, and inhibits cracks inside the positive electrode active material particles and their extension to the surface, thereby inhibiting cracks in the positive electrode active material during cycling, preventing excessive electrolyte penetration, and improving the cycling performance of the positive electrode active material. In the present application, the porous structure of the intermediate layer 12 refers to the core 11 and the outer shell layer 13, and in terms of porosity, it is generally indicated that the porosity of the intermediate layer 12 is greater than that of the core 11 and greater than that of the outer shell layer 13. For example, as a specific example, Figure 2 shows a cross-sectional view of secondary particles of a positive electrode active material observed with a scanning electron microscope after cutting a positive electrode piece made from an embodiment of the positive electrode active material of the present application by ion beam sputtering. As is clear from the figure, when comparing the core 11 and the outer shell layer 13, it can be understood that the intermediate layer 12 has a distinct porous structure.

[0041] In actual operation, the positive electrode active material is cut (for example, by cutting individual positive electrode active materials using ion beam sputtering or other methods, or by first using the positive electrode active material to produce positive electrode pieces and then cutting the positive electrode pieces) to obtain a cross-section of the positive electrode active material. The cross-section is then characterized using a scanning electron microscope (including, but not limited to, a field emission high-resolution scanning electron microscope (FESEM)) and / or a transmission electron microscope (including, but not limited to, a high-resolution transmission electron microscope (HRTEM)) to characterize the micromorphology of the cross-section of the positive electrode active material and the pore structure of the intermediate layer. Furthermore, the crystal structure of the positive electrode active material can be measured using XRD, and the elemental types and contents of the micro-region components in the cross-section of the positive electrode active material can be analyzed using energy dispersive X-ray spectroscopy (EDS) and / or inductively coupled plasma (ICP) elemental analysis to determine the elemental composition and composition ratio of the core and outer shell layers. It should be noted that the method for cutting the positive electrode active material is not particularly limited and can be flexibly selected by those skilled in the art according to actual needs.

[0042] The positive electrode active material of the present application has the following beneficial effects: by doping the positive electrode active material located in the core with element M', it is advantageous to improve the volume stability of the core of the positive electrode active material during the charge-discharge process and reduce the risk of cracking inside the positive electrode active material particles, and at the same time, by providing a soft, porous intermediate layer between the core and the outer shell layer, it is advantageous to buffer the volume deformation and stress accumulation of the core and to prevent cracks inside the positive electrode active material particles and their extension to the surface, thereby reducing the risk of cracking of the positive electrode active material particles during the charge-discharge cycle process and improving their volume stability and cycle performance.

[0043] As an explanation, Li a1 Ni x1 M y1 M' z1 O m1 R n1In the formula, M, M', and R may each independently contain one or more elements. Unless otherwise specified, when one or more of M, M', and R contain two or more elements, the numerical range of the corresponding stoichiometric number in the chemical formula is not only a limitation on the stoichiometric number of each element at that site, but also a limitation on the sum of the stoichiometric numbers of each element at that site. For example, taking M' as an example, when M' is two or more elements, M'1, M'2...M' n If M'1, M'2...M' n The respective stoichiometric numbers z11, z12...z1 n Each of these must fall within the numerical range defined for z1 in this application, and z11, z12... z1 n The sum of M and R must also fall within the range of the numerical value. Similarly, when M and R are two or more elements, the limitations on the numerical range of the stoichiometric numbers of M and R in this application also have the same meaning as above. Similarly, Li a2 Ni x2 M y2 M' z2 O m2 R n2 In the formula, M, M', and R may each independently contain one or more elements, and when M, M', and R are two or more elements, the limitations on the numerical ranges of the stoichiometric numbers of M, M', and R also have the same meanings as above.

[0044] Also, the core is Li a1 Ni x1 M y1 M' z1 O m1 R n1 The outer shell layer includes, but is not limited to, Li a2 Ni x2 M y2 M' z2 O m2 R n2 For example, the core may be Li a1 Ni x1 M y1 M' z1 O m1 R n1 may contain only Li a1 Ni x1 M y1 M'z1 O m1 R n1 and other positive electrode active materials may be included at the same time, among which the specific types of other positive electrode active materials are not particularly limited and can be flexibly selected by those skilled in the art according to actual needs, and the description thereof will be omitted here. a1 Ni x1 M y1 M' z1 O m1 R n1 may include one or more of all positive electrode active materials satisfying the general formula, and Li a2 Ni x2 M y2 M' z2 O m2 R n2 The core may contain one or more of all positive electrode active materials that satisfy the general formula. Furthermore, the compositions of the core and the outer shell layer may be the same or different, and optionally the compositions of the core and the outer shell layer are the same. Also optionally, the core may contain Li a1 Ni x1 M y1 M' z1 O m1 R n1 The outer shell layer may contain only Li a2 Ni x2 M y2 M' z2 O m2 R n2 It may contain only

[0045] It should be noted that in a positive electrode strip, battery, or electrical device, the battery undergoes processes such as chemical formation and cycling, resulting in the consumption of lithium ions, and therefore the measured lithium element contents a1 and / or a2 in the positive electrode active material will be less than 1. Furthermore, if a lithium supplement is used in the positive electrode strip and negative electrode strip, the battery will undergo processes such as chemical formation and cycling, resulting in the measured lithium element contents a1 and / or a2 in the positive electrode active material being greater than 1. Furthermore, the battery undergoes lithium desorption and consumption during charging and discharging, and the molar lithium content will vary when the battery is discharged to different states. In the listing of positive electrode active materials in this application, the molar lithium content is that of the material in its initial state, i.e., before application. When the positive electrode active material is applied to a battery system and undergoes charge and discharge cycles, the molar lithium content will change. Furthermore, during the manufacturing process of a positive electrode active material, differences exist in the oxygen element content in the positive electrode active material due to differences in process control of the oxygen content, etc., or factors such as oxygen release from the crystal lattice. Therefore, in the listing of positive electrode active materials in this application, the molar oxygen content is only a theoretical value and may fluctuate with the actual molar oxygen content.

[0046] Furthermore, in the positive electrode active material of the first aspect of the present application, the performance of the positive electrode active material can be further optimized by further controlling the composition of the intermediate layer and outer shell layer, the type of positive electrode active material, the relative positional relationship of each layer, the volume particle size distribution relationship, etc. In other words, in addition to satisfying the above conditions, one or more of the following conditions may be selectively satisfied.

[0047] In some embodiments of the present application, the intermediate layer 12 is M'' p O q where 1≦p≦2, 2≦q≦3, and M″ may include at least one element of B, Al, or Si.

[0048] For example, the value of p may be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc., or any range of values ​​therein. The value of q may be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc., or any range of values ​​therein. Also, for example, the intermediate layer may include one or more of Al2O3, B2O3, and SiO2. M'' p O q The use of M′ as the intermediate layer material is advantageous in that it reduces the risk of the intermediate layer material adversely affecting the electrochemical performance of the positive electrode active material, and in that in the actual manufacturing process, a specific M′ element or a compound of M′ element can be used to form a unique cross-linked structure (e.g., a gel) in an alkaline environment, and a soft, porous skeletal structure can be obtained after sintering, which is advantageous not only for the intermediate layer to have a relatively large porosity but also for achieving a certain level of supporting strength. For example, core raw materials containing a nickel source, an M source, and an M′ source can be mixed to obtain a mixed liquid, and the mixed liquid can be co-precipitated to obtain first particles. A solution formed from intermediate layer raw materials (e.g., aluminum source, silicon source, boron source, etc.) is mixed with the first particles to undergo a precipitation reaction to obtain second particles. In this case, the intermediate layer raw material may be M″ and / or a compound containing M″, and the precipitation reaction may be carried out in an alkaline environment. During the precipitation process, the precipitated product containing the M″ element can form a unique crosslinked structure layer on the surface of the first particles. A solution formed from outer shell layer raw materials containing a nickel source and an M source (optionally, the outer shell layer raw material may have the same composition as the core raw material) is mixed with the second particles to undergo a precipitation reaction to obtain precursor particles. The precursor particles are mixed with a lithium source and then sintered to obtain a positive electrode active material. Among these, the intermediate layer contains M″. p O qThe presence or absence of M" can be determined by cutting the positive electrode active material, identifying the intermediate layer region in the cross section of the positive electrode active material using a scanning electron microscope and / or a transmission electron microscope, and analyzing the elemental types of the micro-region components in the cross section of the positive electrode active material using a combination of an XRD test and / or an energy dispersive X-ray spectrometer (EDS). Optionally, M" includes Al.

[0049] The intermediate layer meeting the predetermined conditions is advantageous in, on the one hand, reducing the risk that the intermediate layer material may adversely affect the electrochemical performance of the positive electrode active material, and on the other hand, M'' p O q In combination with the formation method of (1), it is advantageous to form an intermediate layer having a porous structure in the positive electrode active material, which is advantageous in achieving both the electrochemical performance and the cycle stability of the positive electrode active material.

[0050] In some embodiments of the present application, in the positive electrode active material, the ratio of the number of moles of M″ element to the number of moles of Li element may be (0.005 to 0.02):(0.9 to 1.1), and optionally may be (0.008 to 0.012):(0.9 to 1.1).

[0051] For example, the ratio of the number of moles of M'' element to the number of moles of Li element in the positive electrode active material is 0.005 / 1.1, 0.005 / 1.05, 0.005 / 1, 0.005 / 0.95, 0.005 / 0.9, 0.008 / 1.1, 0.008 / 1.05, 0.008 / 1, 0.008 / 0.95, 0.008 / 0.9, 0.01 / 1.1, 0.01 / 1.05, 0.01 / 1, 0.01 / 0.95, 0.01 / 0.9 , 0.012 / 1.1, 0.012 / 1.05, 0.012 / 1, 0.012 / 0.95, 0.012 / 0.9, 0.015 / 1.1, 0.015 / 1.05, 0.015 / 1, 0.015 / 0.95, 0.015 / 0.9, 0.02 / 1.1, 0.02 / 1.05, 0.02 / 1, 0.02 / 0.95, 0.02 / 0.9, etc., or may be a range consisting of any of the above values. Optionally, the types of elements M″ and M' are different. ICP elemental analysis can be used to measure the contents of M″ element and Li element in the positive electrode active material, and further, the ratio of the total number of moles of both can be obtained. M″ in the intermediate layer p O q The content of M" can be indirectly explained by the content of M" element. Increasing the content of M" element is beneficial for increasing the thickness of the intermediate layer. Satisfying the content of M" element within a certain condition is beneficial for providing the intermediate layer with an appropriate thickness, improving the buffering capacity of the intermediate layer against volume expansion and stress accumulation in the core, and reducing the risk of cracking of the positive electrode active material particles. At the same time, it is also beneficial for reducing the impact on the volumetric energy density of the positive electrode active material, which is beneficial for further achieving both high specific capacity and cycle stability of the positive electrode active material. Optionally, in the positive electrode active material, the ratio of the number of moles of M" element to the number of moles of Li is (0.008 to 0.012):(0.9 to 1.1). Satisfying this condition is beneficial for further reducing any adverse effects that may be exerted on the volumetric energy density of the positive electrode active material.

[0052] Controlling the relative amounts of the M″ element and the Li element used so as to satisfy a predetermined range is advantageous in further achieving both high specific capacity and cycle stability of the positive electrode active material.

[0053] In some embodiments of the present application, z2>0.

[0054] In a positive electrode active material, doping the positive electrode active material of the outer shell layer with element M' can further improve the cycle stability of the outer shell layer, thereby reducing the risk of cracking of the outer shell layer itself and suppressing the extension of cracks inside the positive electrode active material particles to the surface, which is more advantageous for improving its volume stability and cycle performance. Energy dispersive X-ray spectroscopy (EDS) can be used to determine the type and content of component elements in the micro-regions of the outer shell layer, and / or XRD can be combined to examine the crystal structure of the positive electrode active material. Optionally, the intermediate layer may or may not contain element M'.

[0055] If the outer shell layer satisfies certain conditions, it is advantageous to further improve the cycle stability of the positive electrode active material.

[0056] In some embodiments of the present application, the core 11 is Li a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 and / or the outer shell layer 13 may contain Li a2 Ni x2 Co y21 Mn y22 M' z2 O m2 R n2 , where 0≦y21≦0.2, 0≦y22≦0.2, and y21 and y22 are not 0.

[0057] The core may be a single material and has the general formula Li a1 Ni x1 M y1 M' z1 O m1 R n1Similarly, the outer shell layer may be a single material and may be a mixture containing multiple positive electrode active materials that satisfy the general formula Li a2 Ni x2 M y2 M' z2 O m2 R n2 For example, the core may be a mixture containing multiple positive electrode active materials that satisfy the above condition. a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 , Li a1 Ni x1 Co y11 M' z1 O m1 R n1 , Li a1 Ni x1 Mn y12 M' z1 O m1 R n1 As a specific example, the core may include, but is not limited to, one or more of Li a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 In yet another specific example, the outer shell layer may include Li a2 Ni x2 Co y21 Mn y22 M' z2 O m2 R n2 Among them, Li a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 may be a single material or a mixture containing multiple positive electrode active materials satisfying the general formula, and Li a2 Ni x2 Co y21 Mn y22 M' z2 O m2 Rn2 may be a single material or a mixture containing multiple positive electrode active materials that satisfy the general formula.

[0058] The values ​​of y11 and y12 may each independently be 0, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, etc., or may be any range of the above values. The values ​​of y21 and y22 may each independently be 0, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, etc., or may be any range of the above values. Doping the Ni-containing layered positive electrode active material with Co is advantageous for stabilizing the layered structure, suppressing lithium-nickel mixing, and improving the cycle performance of the positive electrode active material. Doping with manganese is advantageous for improving structural stability and thermal stability. When the values ​​of x1, x2, y11, y12, y21, and y22 satisfy the predetermined ranges, it is advantageous not only to obtain a relatively high specific capacity but also to obtain relatively good cycle performance and Coulombic efficiency. XRD can be combined to examine the crystal structure of the positive electrode active material, and the positive electrode active material can be cut and analyzed by EDS energy dispersive X-ray spectroscopy and / or ICP elemental analysis in combination to analyze the types and contents of component elements in a micro-area of ​​the cross-section of the positive electrode active material.

[0059] The composition of the core and / or outer shell layer satisfies a predetermined range condition, which is advantageous for achieving both high specific capacity and cycle performance of the lithium battery.

[0060] In some embodiments of the present application, 0.002≦z1≦0.008 and / or 0.002≦z2≦0.008.

[0061] For example, the values ​​of z1 and z2 may each independently be 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, etc., or may be within a range of any of the above values. As described above, the values ​​of z1 and z2 can be measured by combining ICP elemental analysis and / or EDS analysis. For example, if the core and shell layers have the same material composition, the values ​​of z1 and z2 will be the same, and ICP elemental analysis can be performed directly on the positive electrode active material particles to obtain the values ​​of z1 and z2. As the values ​​of z1 and z2 increase, the amount of M' doping in the positive electrode active material located in the core and shell layers also increases, further improving the volume stability of the positive electrode active material during cycling and advantageously reducing the risk of cracking. Furthermore, independently controlling the values ​​of z1 and z2 to satisfy a predetermined range is also advantageous in reducing the risk that excessive doping of M' will significantly increase the number of heterophases, further affecting the electrochemical performance of the positive electrode active material.

[0062] Controlling the values ​​of z1 and / or z2 within a predetermined range is advantageous not only for improving the cycle stability of the positive electrode active material, but also for reducing the risk of a decline in the electrochemical performance of the positive electrode active material.

[0063] In some embodiments of the present application, the particle diameter of the positive electrode active material is D1, the distance from the inner surface of the intermediate layer 12 to the center of the core 11 is 0.3D1 or more, and the distance from the outer surface of the intermediate layer 12 to the center of the core 11 is 0.4D1 or less.

[0064] For example, the distance from the inner surface of the intermediate layer to the center of the core may be 0.3D1, 0.305D1, 0.31D1, 0.315D1, 0.32D1, 0.325, 0.33D1, 0.335D1, 0.34D1, 0.345D1, 0.35D1, 0.355D1, 0.36D1, 0.37D1, 0.375D1, 0.38D1, 0.385D1, 0.39D1, 0.395D1, etc., or may be a range consisting of any of the above values. The distance from the outer surface of the intermediate layer to the center of the core may be 0.4D1, 0.395D1, 0.39D1, 0.385D1, 0.38D1, 0.375D1, 0.37D1, 0.365D1, 0.36D1, 0.355D1, 0.35D1, 0.345D1, 0.34D1, 0.335D1, 0.33D1, 0.325, 0.32D1, 0.315D1, 0.31D1, 0.305D1, etc., or may be a range consisting of any of the above values. The distance from the outer surface of the intermediate layer to the center of the core is greater than the distance from the inner surface of the intermediate layer to the center of the core, and both the distance from the outer surface of the intermediate layer to the center of the core and the distance from the inner surface of the intermediate layer to the center of the core are understood to be average distances, the distance from the inner surface of the intermediate layer to the center of the core is understood to be the particle diameter of the core, and the distance from the outer surface of the intermediate layer to the center of the core and the distance from the inner surface of the intermediate layer to the center of the core are understood to be the thickness of the intermediate layer. Among these, the particle diameter of the positive electrode active material is the absolute particle diameter of each positive electrode active material particle, or the volume distribution particle diameter D of the positive electrode active material particles v I understand it as 50, but D vThe "50" refers to the particle size corresponding to the cumulative volume distribution percentage reaching 50% (i.e., the volume content of particles below this particle size and the volume content of particles above this particle size each account for 50% of the total particle volume). This can be measured using a laser particle size analyzer (Malvern Master Size 2000) in accordance with GB / T19077-2016 / ISO 13320:2009. The core particle size also has the same meaning. The specific test procedure includes the following: Take an appropriate amount of sample to be measured (the sample concentration should be 8%-12% opaque), add 20 mL of deionized water, and simultaneously ultrasonicate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion. Then, measure the sample in accordance with GB / T19077-2016 / ISO 13320:2009. The distance from the intermediate layer to the center of the core can be estimated by cutting the cathode active material and using a scanning electron microscope or transmission electron microscope. Controlling the distance from the inner surface and outer surface of the intermediate layer to the center of the core to meet specified conditions is advantageous in that, on the one hand, it is possible to utilize the high porosity structure of the intermediate layer to suppress internal cracking and the extension of cracks to the outer surface of the positive electrode active material, and on the other hand, it is advantageous in improving the buffering ability of the intermediate layer against volumetric deformation and stress accumulation of the core, thereby improving the intermediate layer's effect of suppressing cracking of the positive electrode active material. At the same time, it is advantageous in reducing the risk that cracks in the intermediate layer will quickly extend to the outer surface due to the intermediate layer being too close to the outer shell layer, or that the porosity of the outer shell layer will be too large due to the intermediate layer extending directly to the outer shell layer, causing a large amount of electrolyte to penetrate into the interior of the material and affecting material performance. It can also reduce the risk that the thickness of the intermediate layer will be too large, affecting the ion migration rate and volumetric energy density of the positive electrode active material.

[0065] Controlling the distance from the intermediate layer of the positive electrode active material to the center of the core so as to satisfy predetermined conditions is not only advantageous in improving the risk of cracking of the positive electrode active material during cycling, but also advantageous in reducing adverse effects on the ion migration rate and volumetric energy density, and is advantageous in further achieving a balance between the cycle performance, rate performance, and energy density of the positive electrode active material.

[0066] In some embodiments of the present application, the particle diameter of the particles of the positive electrode active material may be D1, and the thickness of the intermediate layer 12 may be 0.05D1 to 0.0625D1.

[0067] For example, the thickness of the intermediate layer 12 may be 0.05D1, 0.0525D1, 0.055D1, 0.0575D1, 0.06D1, 0.0625D1, etc., or may be within a range of any of the above values. The thickness of the intermediate layer can be estimated by cutting the positive electrode active material and combining it with a scanning electron microscope or a transmission electron microscope. In this application, the thickness of the intermediate layer can be understood as the average thickness of the intermediate layer of the positive electrode active material particles. Controlling the thickness of the intermediate layer to meet certain conditions not only ensures that the intermediate layer has an effective buffering ability against volumetric deformation and stress accumulation of the core, but also helps to prevent cracks from breaking and extending outward in the positive electrode active material, and simultaneously reduces the adverse effects of the thickness of the intermediate layer on the ion migration rate and volumetric energy density of the positive electrode active material.

[0068] Controlling the thickness of the intermediate layer so as to satisfy predetermined conditions is not only advantageous in improving the risk of cracking during the cycling process of the positive electrode active material, but also advantageous in further reducing the adverse effects on the ion migration rate and volumetric energy density, and is advantageous in further achieving a balance between the cycle performance, rate performance, and energy density of the positive electrode active material.

[0069] In some embodiments of the present application, the cross-sectional particle diameter of the positive electrode active material in a cross section passing through the center of its core may be 0.9 to 1.1 times the volume average particle diameter Dv50 of the positive electrode active material, and the cross-sectional area of ​​the intermediate layer 12 may be 5% to 20% of the total cross-sectional area of ​​the positive electrode active material. For example, the cross-sectional area of ​​the intermediate layer 12 may be 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc., of the total cross-sectional area of ​​the positive electrode active material, or may be within a range consisting of any of the above values. Controlling the cross-sectional area of ​​the intermediate layer to satisfy predetermined conditions is advantageous for reducing the risk of cracking of the positive electrode active material during cycling and for reducing adverse effects on ion migration rate and volumetric energy density, thereby advantageously achieving a better balance between the cycle performance, rate performance, and energy density of the positive electrode active material.

[0070]

number

[0071]

number

[0072] Controlling the volumetric particle size distribution of the positive electrode active material to satisfy predetermined conditions is advantageous for improving the volumetric energy density of the battery.

[0073] In some embodiments of the present application, the volume average particle size Dv50 of the positive electrode active material may be 6 μm to 18 μm.

[0074] For example, the volume average particle diameter Dv50 of the positive electrode active material may be 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, etc., or may be within a range of any of the above values, or may optionally be 8 μm to 12 μm. Controlling the volume average particle diameter Dv50 of the positive electrode active material to satisfy predetermined conditions is not only advantageous for improving the stability of the overall particle structure of the positive electrode active material, but also for providing the positive electrode active material with the advantages of a small internal conduction distance and fewer surface side reactions, which is advantageous for further improving the electrochemical performance of the positive electrode active material.

[0075] In some examples of the present application, the pressed density of the positive electrode active material at a pressure of 5 tons is 3.4 g / cm 3 For example, the pressed density of the positive electrode active material at a pressure of 5 tons may be 3.4 g / cm or more. 3 , 3.45g / cm 3 , 3.5g / cm 3 , 3.55g / cm 3 , 3.6g / cm 3 , 3.65g / cm 3 , 3.7g / cm 3 , 3.75g / cm 3 , 3.8g / cm 3 , 3.85g / cm 3 The positive electrode active material's pressed density can be tested in accordance with the national standard GB / T 24533-2009. Controlling the positive electrode active material's pressed density to meet certain conditions is advantageous for further improving the volumetric energy density of the battery.

[0076] Currently, there is a method for producing a porous cathode active material by embedding an organic template in a precursor and then sintering it at high temperature. However, due to the dispersibility of the organic material, it is difficult to control the location and distribution of the porous structure. In addition, the precursor must be produced by a hydrothermal method, which is a complex and expensive process and difficult to implement on a large scale industrial scale.

[0077] In view of this, based on the same inventive concept as the cathode active material of the first aspect of the present application, the second aspect of the present application provides a method for manufacturing a cathode active material, Mixing a core raw material containing a nickel source, an M source, and an M' source to obtain a mixed solution, performing a first precipitation reaction on the obtained mixed solution to obtain first particles, mixing a solution formed using an intermediate layer raw material and the first particles to perform a second precipitation reaction to obtain second particles, mixing a shell layer raw material containing a nickel source and an M source, mixing the obtained mixed solution and the second particles to perform a third precipitation reaction to obtain precursor particles, mixing the precursor particles and a lithium source and sintering to obtain a cathode active material, wherein the precipitation product formed on the outer surface of the first particles by the second precipitation reaction forms a porous structure by sintering, and the cathode active material includes a core, an intermediate layer, and a shell layer, and the core is Li a1 Ni x1 M y1 M’ z1 O m1 R n1 and contains 0.9 ≦ a1 ≦ 1.1, 0.6 ≦ x1 < 1, 0 ≦ y1 ≦ 0.4, 0 < z1 ≦ 0.01, 1.9 ≦ m1 ≦ c2.2, 0 ≦ n1 ≦ 0.1, M contains at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, Ce, M' contains at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti or Ga, R contains at least one element of F, Cl or S, the intermediate layer covers at least a part of the outer surface of the core and has a porous structure, the shell layer covers at least a part of the outer surface of the intermediate layer, Li a2 Ni x2 M y2 M’ z2 O m2 R n2 and contains 0.9 ≦ a2 ≦ 1.1, 0.6 ≦ x2 < 1, 0 ≦ y2 ≦ 0.4, 0 ≦ z2 ≦ 0.01, 1.9 ≦ m2 ≦ 2.2, 0 ≦ n2 ≦ 0.1.

[0078] The method for manufacturing the cathode active material of the present application has the following beneficial effects: Li a1 Ni x1 M y1 M’ z1 Om1 R n1 and a core containing Li a2 Ni x2 M y2 M' z2 O m2 R n2 and a positive electrode active material in which the intermediate layer has a porous structure, the feasibility of operation is high, and structural parameters such as the raw material composition of each layer and the position, thickness, and pore structure of the intermediate layer are easily controlled. It should be noted that the manufacturing method of the second embodiment of the present application is proposed based on the same inventive concept as the positive electrode active material of the first embodiment of the present application, and the features and effects described for the positive electrode active material of the first embodiment of the present application also apply to the manufacturing method of the second embodiment of the present application, and therefore the description thereof will be omitted here.

[0079] In some embodiments of the present application, when the first particles are produced, Li a1 Ni x1 M y1 M' z1 O m1 R n1 According to the stoichiometric ratio, the core raw materials including the nickel source, the M source, and the M' source can be mixed to obtain a mixed solution. When preparing precursor particles, Li a2 Ni x2 M y2 M' z2 O m2 R n2 A mixed solution can be obtained by mixing outer shell layer raw materials including a nickel source and an M source based on the stoichiometric ratio, and as another specific example, x1+y1+z1=1 and / or x2+y2+z2=1.

[0080] In some embodiments of the present application, the intermediate layer material may include an M″ source, and the M″ source may include a compound having at least one element of B, Al, or Si. Optionally, the M″ compound may include an oxide and / or a salt.

[0081] In some embodiments of the present application, the shell layer raw material and the core raw material may be the same or different; for example, the types and compounding ratios of the shell layer raw material and the core raw material may be completely identical, or, for example, the only difference between the shell layer raw material and the core raw material may be that the shell layer raw material does not contain an M' source.

[0082] In some embodiments of the present application, the first precipitation reaction and the third precipitation reaction are co-precipitation reactions, and the second precipitation reaction may optionally be a gelation precipitation reaction. The first precipitation reaction, the second precipitation reaction, and the third precipitation reaction may each independently be selected to include or exclude a precipitating agent and / or a complexing agent.

[0083] In some embodiments of the present application, taking a nickel-cobalt-manganese layered positive electrode active material for use in a lithium battery as an example, a nickel source, a manganese source, a cobalt source, and an M' source are mixed in a predetermined stoichiometric ratio to obtain a mixed solution, and a portion of the mixed solution is subjected to a coprecipitation reaction to produce first particles. When the first particles grow to a first predetermined particle size, the first particles are mixed with a solution formed using an M" source to undergo a precipitation reaction to produce second particles. Here, the solution formed using the M" source may be obtained by mixing an oxide of the M" element with an acidic or alkaline solution, or may be obtained by dissolving an M" salt in an aqueous solvent. When the second particles grow to a second predetermined particle size, the second particles are mixed with the remaining mixed solution to undergo a coprecipitation reaction to produce precursor particles. When the precursor particles grow to a third predetermined particle size, the precursor particles and a lithium salt are mixed in a predetermined ratio and sintered to obtain a positive electrode active material. Optionally, the addition of a precipitating agent and / or a complexing agent can be selected independently for each precipitation reaction.

[0084] In the present application, the specific types of raw material components such as the nickel source, M' source, M" source, and lithium source are not particularly limited, and those skilled in the art can flexibly select them according to actual needs. For example, the M' source includes, but is not limited to, one or more of sulfates, carbonates, nitrates, chlorides, silicates, acetates, oxalates, oxides, hydroxides, etc.; the M" source includes, but is not limited to, one or more of sulfates, nitrates, chlorides, fluorides, oxalates, acetates, etc.; the lithium source includes, but is not limited to, one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, CHClO1, etc.; and it is understood that other raw material components such as the nickel source (e.g., a cobalt source or a manganese source) also each independently include, but are not limited to, one or more of sulfates, nitrates, carbonates, chlorides, fluorides, oxalates, acetates, etc. Furthermore, the process parameters (e.g., pH value, reaction time, reaction temperature, heating rate, sintering atmosphere, etc.) controlled in the first precipitation reaction, the second precipitation reaction, the third precipitation reaction, and the sintering operation are not particularly limited and can be flexibly selected by those skilled in the art according to actual needs. For example, the temperature of each precipitation reaction may independently be 40°C to 80°C, the pH value may be 11 to 14, or optionally 12 to 13, the sintering temperature may be 600°C to 850°C, or optionally 650°C to 750°C, the sintering time may be 8 hours to 18 hours, or optionally 10 hours to 15 hours, the heating rate may be 0.5°C / min to 5°C / min, or optionally 1°C / min to 3°C / min, and the sintering atmosphere may be air, oxygen, or a mixture of oxygen and nitrogen or an inert gas. Furthermore, in the present application, the specific types of precipitating agent and complexing agent are not particularly limited, and those skilled in the art can flexibly select them according to actual needs. For example, the precipitating agent includes, but is not limited to, one or more of sodium hydroxide, sodium carbonate, potassium carbonate, and potassium hydroxide; the complexing agent includes, but is not limited to, one or more of ammonia water, ammonium chloride, ammonium sulfate, urea, citric acid, EDTA, etc.

[0085] As a specific example, the core is Li a1 Ni x1 Co y11 Mn y12 M' z1 O m1 R n1 The outer shell layer contains Li a2 Ni x2 Co y21 Mn y22 M' z2 O m2 R n2 and the middle layer is M'' p O q Specifically, the manufacturing process for a positive electrode active material containing the above compound includes mixing a Ni salt, a Co salt, a Mn salt, and an M' source in a predetermined ratio to form a mixed solution, pumping the mixed solution, a precipitant, and a complexing agent into a reactor at a constant pumping speed, controlling the pH and reaction temperature of the materials in the reactor to carry out a co-precipitation reaction, and monitoring the particle size in the reactor (specifically, periodically discharging a small amount of product from the outlet at the bottom of the reactor to measure the particle size; since the reactor used for the reaction is generally relatively large, discharging a small amount of product has little effect on the reaction conditions and progress), and when the material particles in the reactor have grown to 3 / 5 to 4 / 5 of the volume particle size Dv50 of the target particles (i.e., precursor particles), stopping the pumping of the mixed salt solution, and pumping the solution formed using the M'' source into the reactor, and after the solution formed from the M'' source has been completely pumped out, pumping the remaining mixed solution into the reactor for reaction, and monitoring the particle size in the reactor to obtain precursor particles grown to the volume particle size of the target particles. The resulting precursor particles are mixed with a lithium source and sintered to obtain a positive electrode active material, wherein the sintering temperature is 600°C to 850°C, optionally 650°C to 750°C, the sintering time is 8 hours to 18 hours, optionally 10 hours to 15 hours, the heating rate is 0.5°C / min to 5°C / min, optionally 1°C / min to 3°C / min, and the sintering atmosphere can be air, oxygen, or a mixture of oxygen and nitrogen or an inert gas.

[0086] A third aspect of the present application provides a cathode strip comprising the cathode active material of the first aspect of the present application or the cathode active material produced using the method of the second aspect of the present application.

[0087] In a battery, the positive electrode piece typically includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material disposed on the positive electrode current collector.

[0088] The positive electrode current collector may be a conventional metal foil strip or a composite current collector (a metal material may be deposited on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may include at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, and may optionally be aluminum foil.

[0089] The positive electrode active material layer may optionally further include at least one of an adhesive, a conductive agent, and other optional auxiliary agents. By way of example, the conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. By way of example, the adhesive may include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0090] All of these materials are commercially available.

[0091] A fourth aspect of the present application provides a battery including the positive electrode piece of the third aspect of the present application, whereby the battery may have relatively good cycle stability and a relatively long service life.

[0092] A battery refers to a battery that can be activated and continued to be used by way of charging the active material after discharge.

[0093] The batteries proposed in this application are understood to be lithium batteries, such as lithium ion batteries.

[0094] A typical battery consists of positive and negative electrodes, a separator film, and an electrolyte. During the charge and discharge process, active ions are inserted and removed between the positive and negative electrodes. The separator film is placed between the positive and negative electrodes to provide insulation. The electrolyte conducts ions between the positive and negative electrodes.

[0095] [Negative electrode piece] In a battery, the negative electrode piece typically includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material disposed on the negative electrode current collector. The negative electrode current collector may be a conventional metal foil piece or a composite current collector (e.g., a metal material may be disposed on a polymer substrate to form a composite current collector). For example, the negative electrode current collector may be a copper foil.

[0096] In some embodiments of the present application, the battery of the fourth aspect of the present application may be a lithium-ion battery. In this case, the specific type of negative electrode active material is not limited. Any active material known in the art that can be used for the negative electrode of a lithium-ion battery can be employed, and those skilled in the art can select the material according to their actual needs. For example, the negative electrode active material may include, but is not limited to, at least one of lithium metal, a carbon material, an alloy material, a silicon-based material, a phosphorus-based material, etc. Specifically, the carbon material may include, but is not limited to, at least one of hard carbon, soft carbon, amorphous carbon, and a nanostructured carbon material. The alloy material may include, but is not limited to, an alloy material formed from at least one of Si, Ge, Sn, Pb, and Sb. The silicon-based material may include, but is not limited to, a silicon-carbon material, a silicon oxide, etc. All of these materials are commercially available.

[0097] The negative electrode active material layer typically includes an adhesive for selectively improving the conductivity of the negative electrode active material layer and a conductive agent for firmly adhering the negative electrode active material and the conductive agent to the negative electrode current collector. The types of the conductive agent and adhesive are not particularly limited and can be selected according to actual needs. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. For example, the adhesive may include at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubbers (SBCs), water-based acrylic resins, and carboxymethyl cellulose (CMC).

[0098] The negative electrode active material layer may include a thickener such as carboxymethyl cellulose (CMC), but the present application is not limited thereto, and other materials that can be used as thickeners for negative electrode pieces of lithium ion batteries may also be used.

[0099] In some embodiments of the present application, the battery of the fourth aspect of the present application may be a lithium metal battery, in which case the negative electrode active material includes, but is not limited to, metallic lithium alone. For example, the negative electrode active material may be an alloy formed between metallic lithium and various other metallic or non-metallic elements.

[0100] In some embodiments of the present application, the battery of the fourth aspect of the present application may be a negative electrode-less lithium metal battery, in which the negative electrode is composed only of a metal foil current collector, with no lithium metal present on its surface, and during cycling, only the lithium in the positive electrode is used, and it is deposited and peeled off in the form of lithium metal on the negative electrode side.

[0101] [Electrolyte] The electrolytic solution may include an electrolyte salt and a solvent.

[0102] By way of example, the electrolyte lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bisoxalatoborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonyl)imide.

[0103] By way of example, the solvent may include at least one 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), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), methyl propionate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0104] In some embodiments, the electrolyte solution may further include additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve specific battery properties, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature performance of the battery.

[0105] [Separator film] The separator film is not particularly limited in the present application, and any known separator film having a porous structure and electrochemical and mechanical stability can be selected and used according to actual needs. For example, the separator film may include a single-layer or multi-layer film containing at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0106] In the embodiments of the present application, the shape of the battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Fig. 4 illustrates a battery 1 having a rectangular structure as an example.

[0107] In some embodiments, the battery may include an outer packaging used to enclose the positive electrode strips, the negative electrode strips, and the electrolyte.

[0108] In some embodiments, the outer packaging may include a casing and a cover plate. The casing may include a base plate and a side plate connected to the base plate, and the base plate and the side plate may surround and form a receiving cavity. The casing may have an opening communicating with the receiving cavity, and the cover plate may cover the opening to seal the receiving cavity.

[0109] The positive electrode pieces, negative electrode pieces, and separator film can be wound or stacked to form an electrode assembly. The electrode assembly is enclosed in the receiving cavity. The number of electrode assemblies included in the battery can be one or more, and can be adjusted according to needs.

[0110] In some embodiments, the battery's exterior packaging may include a rigid casing, such as a hard plastic casing, an aluminum casing, a steel casing, or the like.

[0111] The exterior packaging of the battery may also be a pouch, such as a bag-type pouch, etc. The material of the pouch may be a plastic including at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0112] In some embodiments, the battery may be a battery cell, or a battery module or battery pack assembled from battery cells. The battery module or battery pack may include multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0113] FIG. 5 shows an example of a battery module 2. Referring to FIG. 5, in the battery module 2, the plurality of batteries 1 may be arranged in order along the length of the battery module 2. Of course, they may be arranged in any other manner. Furthermore, the plurality of batteries 1 may be fixed with fastening members.

[0114] The battery module 2 may further include an outer shell having a storage space for storing a plurality of batteries 1. In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0115] 6 and 7 show an example of a battery pack 3. Referring to FIGS. 6 and 7, the battery pack 3 may include a battery box and a plurality of battery modules 2 installed in the battery box. The battery box includes an upper case 4 and a lower case 5, and the upper case 4 is attached to the lower case 5 as a lid, forming a sealed space for accommodating the battery modules 2. The plurality of battery modules 2 may be arranged in the battery box in any manner.

[0116] A fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application.

[0117] Specifically, the battery may be a power source for the electric device or an energy storage unit for the electric device, which may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, energy storage systems, etc.

[0118] FIG. 8 shows an example of an electric device. The electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Other examples of electric devices may include a mobile phone, a tablet, or a laptop. The electric device is typically required to be thin and lightweight, and may employ a battery as a power source.

[0119] The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present application. Unless specific techniques or conditions are described in the examples, they may be performed in accordance with techniques or conditions described in literature in the field or in accordance with the product instructions. The reagents or equipment used may be ordinary commercially available products without specifying the manufacturer.

[0120] Example 1 (1) Manufacturing of positive electrode active materials S1:LiNi 0.928 Mn 0.07 Zr 0.002Based on the stoichiometric ratio of O2, nickel sulfate, manganese sulfate, and zirconium sulfate were mixed so that the molar ratio of nickel element in nickel sulfate, manganese element in manganese sulfate, and zirconium element in zirconium sulfate was 0.928:0.07:0.002, and a mixed salt solution was prepared. Sodium hydroxide solution was used as a precipitant, and ammonia water was used as a complexing agent. Pure water and the precipitant were fed into the reactor, and stirring was started. The temperature was maintained at 60°C, and stirring was started. The mixed solution, the precipitant solution, and the complexing agent solution were fed into the reactor, and the mixed solution, the precipitant solution, and the complexing agent solution were fed into the reactor. During the precipitation reaction, the concentration and pH of the ammonia water in the reactor were kept constant, and a small amount of reaction product was periodically discharged from the bottom of the reactor to measure the Dv50 particle size, thereby monitoring the change in particle size of the material particles in the reactor. The volumetric particle size Dv50 of the resulting precursor particles was designed to be 12 μm, and when the particle size of the material particles in the reactor reached 3 / 5 of the Dv50 particle size, i.e., 7.2 μm, the supply of the mixed salt solution to the reactor was stopped. At this point, the pH value in the reactor was 11, and the concentration of ammonia water was 0.5 mol / L.

[0121] S2: A fixed amount of aluminum nitrate solution was continuously fed into the reactor to continue the precipitation reaction until the aluminum nitrate solution was completely added.

[0122] S3: The mixed salt solution prepared in step S1 was continuously supplied to the reactor, and the coprecipitation reaction was continued until the particle diameter of the material particles Dv50 in the reactor reached 12 μm. The reaction slurry was then centrifuged, washed, filtered, and dried to obtain precursor particles.

[0123] S4:LiNi 0.928 Mn 0.07 Zr 0.002Based on the stoichiometric ratio of O2, the precursor particles and lithium hydroxide were mixed in a suitable ratio and then sintered to obtain a positive electrode active material, where the sintering temperature was 700°C, the sintering time was 15 hours, the heating rate was 5°C / min, the sintering atmosphere was oxygen, and the molar ratio of aluminum element in aluminum nitrate S2 to the total amount of nickel, manganese, and zirconium elements in the mixed salt S3 to lithium element in lithium hydroxide was 0.005:1:1.

[0124] (2) Battery manufacturing (1) Manufacturing of positive electrode pieces The prepared positive electrode active material, conductive agent acetylene black, and adhesive polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of solvent NMP at a mass ratio of 94:3:3 by stirring thoroughly, and then coated evenly on both sides of a 13 μm thick aluminum foil, dried, and cold pressed to a thickness of 0.02 g / cm on one side. 2 A positive electrode piece having the following formula was obtained.

[0125] (2) Manufacturing of negative electrode pieces The negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, adhesive styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were mixed in a weight ratio of 90:5:2:2:1 in a deionized water solvent system by thorough stirring and then uniformly mixed. The mixture was then applied to a 6 μm thick copper foil with equal thickness on both sides, dried, and cold pressed to a surface density of 0.012 g / cm on one side. 2 A negative electrode piece having the following formula was obtained.

[0126] (3) Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in equal volumes to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0127] (4) Separator film: A porous polyethylene film was used as the separator film.

[0128] (5) Battery manufacturing The positive electrode, separator film, and negative electrode were stacked in this order, with the separator film between the positive and negative electrodes to act as insulators, and then rolled up to obtain a bare cell. The bare cell was then placed in an outer package, and the formulated base electrolyte was injected and sealed to obtain a complete battery.

[0129] Example 2 The difference from Example 1 is that in step S3, LiNi 0.93 Mn 0.07 Based on the stoichiometric ratio of O2, the nickel element in nickel sulfate and the manganese element in manganese sulfate are mixed in a molar ratio of 0.93:0.07 to form a mixed salt solution, and the mixed mixed salt solution is fed into a reactor. The co-precipitation reaction is continued until the particle size of the material particles Dv50 in the reactor reaches 12 μm, and the reaction slurry is centrifuged, washed, filtered, and dried to obtain precursor particles.

[0130] Comparative Example 1 The difference from Example 2 is that in steps S1 and S3, LiNi 0.93 Mn 0.07 Based on the stoichiometric ratio of O2, the nickel element in nickel sulfate and the manganese element in manganese sulfate are mixed in a molar ratio of 0.93:0.07 to prepare a mixed salt solution, the details of which are shown in Table 1.

[0131] Comparative Example 2 The difference from the second embodiment is that step S2 is not performed.

[0132] Comparative Example 3 The difference from Example 2 is that steps S2 and S3 are not performed, and in step S1, LiNi 0.93 Mn 0.07According to the stoichiometric ratio of O2, nickel element from nickel sulfate and manganese element from manganese sulfate are mixed in a molar ratio of 0.93:0.07, and a mixed salt solution is prepared. Sodium hydroxide solution is used as a precipitant and ammonia water is used as a complexing agent. Pure water and precipitant are supplied to the reactor, and stirring is started. The temperature is kept constant at 60°C, and stirring is started. While controlling the concentration and pH of the ammonia water in the reactor to be constant, the mixed salt solution, precipitant solution and complexing agent solution are supplied to the reactor at a constant flow rate to carry out a co-precipitation reaction. The particle size change of the material particles in the reactor is monitored until the particle size Dv50 grows to 12 μm. The pH value in the reactor is 11, and the concentration of the ammonia water is 0.5 mol / L.

[0133] Example 3 The difference from Example 1 is that step S1 is to mix the mixed salt solution according to the core materials shown in Table 1.

[0134] Example 4 The difference from Example 3 is that in step S3, a mixed salt solution is formulated according to the outer shell layer materials shown in Table 1.

[0135] Comparative Example 4 The difference from Example 4 is that in step S1, a mixed salt solution is formulated according to the core material shown in Table 1, and in step S3, a mixed salt solution is formulated according to the outer shell layer material shown in Table 1.

[0136] Comparative Example 5 The difference from the fourth embodiment is that step S2 is not performed.

[0137] Comparative Example 6 The difference from Example 4 is that steps S2 and S3 are not performed, and in step S1, LiNi 0.91 Co 0.07 Mn 0.02According to the stoichiometric ratio of O2, nickel sulfate, manganese sulfate, and cobalt sulfate are mixed in a predetermined stoichiometric ratio to prepare a mixed salt solution, sodium hydroxide solution is used as a precipitant, and ammonia water is used as a complexing agent. Pure water and precipitant are fed into the reactor, and stirring is started. The temperature is kept constant at 60°C, and stirring is started. While controlling the concentration and pH of the ammonia water in the reactor to be constant, the mixed solution, precipitant solution, and complexing agent solution are fed into the reactor at a certain flow rate to carry out co-precipitation reaction. The change in particle size of the material particles in the reactor is monitored until the particle volume particle size Dv50 grows to 12 μm. Here, the pH value of the reactor is 11, and the concentration of the ammonia water is 0.5 mol / L.

[0138] Examples 5 to 34 The difference between Examples 5 to 8 and Example 3 is that the core material and outer shell material used to blend the mixed salt solution in steps S1 and S3 are different.

[0139] The difference between Examples 9 to 11 and Example 3 is that the amount of aluminum nitrate used in step S2 is different, and the ratio of the total number of moles of Al and Li in the produced positive electrode active material is different. Details are shown in Table 1.

[0140] The differences between Example 12 and Example 3 are that the core material and shell layer material used to formulate the mixed salt solution in steps S1 and S3 are different, and the amount of aluminum nitrate used in step S2 is different, details of which are shown in Table 1.

[0141] The difference between Example 13 and Example 12 is that silicic acid (H2SiO3) is used to replace aluminum nitrate in step S2, that is, M'' is Si. The details of the intermediate layer material and the amount of Si used are shown in Table 1.

[0142] The difference between Example 14 and Example 12 is that boric acid (H3BO3) is used to replace aluminum nitrate in step S2, that is, M'' is B. The details of the intermediate layer material and the amount of Si used are shown in Table 1.

[0143] The difference between Examples 15 to 24 and Example 12 is that the core material and outer shell material used to blend the mixed salt solution in steps S1 and S3 are different.

[0144] Examples 25 to 29 differ from Example 12 in that the amount of aluminum nitrate used in step S2 is different, and the upper and / or lower limits of the distance from the intermediate layer to the center of the core are different.

[0145]

number

[0146] The difference between Examples 32 to 34 and Example 12 is that the core material and outer shell material used to blend the mixed salt solution in steps S1 and S3 are different.

[0147] Test Method: (a) Inductively coupled plasma optical emission spectroscopy testing of the elemental composition of the positive electrode active material The equipment standard is EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectroscopy." A sample of the positive electrode active material was chemically treated to decompose it into a solution, which was then atomized and introduced into plasma to excite the characteristic spectral lines of the elements. The element contents were qualitatively and quantitatively analyzed based on the wavelength and intensity (proportional to the concentration) of the spectral lines, and the relative molar ratios of Li and M" in the positive electrode active materials prepared in each example and comparative example were obtained. The specific operation steps are as follows: 0.4 g (accurate to 0.0001 g) of dry cathode active material sample is placed in a 30 mL digestion tank, one digestion tank without sample is left as a blank sample, the digestion tank containing the sample is placed in a fume hood and 12 mL of reverse aqua regia is added, the reverse aqua regia is added along the inner wall of the digestion tank, and the sample remaining on the inner wall is allowed to flow to the bottom of the tank, then the top cover, insulating sleeve, gasket, microwave digester, and nut are installed in that order, and the nut is tightened with a wrench before starting the microwave digester, the optical fiber sensor in the microwave digester is inserted into the bottom of the digestion tank filled with the pre-assembled sample, the digestion tank is placed in equilibrium with the microwave digester, and the digestion begins (the digestion program is The temperature was raised to 120°C in 6 minutes and held for 8 minutes, then raised to 160°C in 5 minutes and held for 8 minutes, then raised to 180°C in 5 minutes and held for 5 minutes. After cooling to room temperature, the decomposition tank was removed and placed in a fume hood. The nuts were slowly loosened to degas the tank. The previous components were removed one by one. The solution in the decomposition tank was transferred to a 100mL measuring flask through a funnel (which should be lined with filter paper). The decomposition tank was then washed with ultrapure water, and the washings were also transferred to a measuring flask. 10mL of ultrapure water was used for each wash. The solution in the 100mL measuring flask was shaken evenly, and 1mL of the shaken solution was pipetted into another 100mL measuring flask, and then ultrapure water was added to the final volume (the solution reached a total of 100mL). Finally, the sample solution was tested using an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer).Among them, the inverse aqua regia was prepared by mixing ultrapure water, concentrated nitric acid, and concentrated hydrochloric acid in a volume ratio of 4:3:1, and the mass concentrations of the concentrated nitric acid and concentrated sulfuric acid were both 68%, and was obtained by purchasing a commercially available product.

[0148] (b) Testing particle size, thickness and location of the intermediate layer With reference to the standard GB / T 19077-2016 / ISO 13320:2009, the volume particle size distribution: (Dv90-Dv10) / Dv50 was calculated using a laser particle size analyzer for the Dv50, Dv90, and Dv10 of the positive electrode active materials produced in each example and comparative example.

[0149] The thickness of the intermediate layer and the distance from the intermediate layer to the center of the core are determined by the following method: Taking Example 1 as an example, the reaction slurries produced in steps S1, S2, and S3, respectively, are centrifuged, washed, filtered, and dried to obtain particles, which are referred to as first particles, second particles, and precursor particles, respectively. Lithium hydroxide is mixed with the particles produced in steps S1, S2, and S3, respectively, and sintered under the same conditions and with the same Li:Ni molar ratio and sintering conditions as in step S4. After cooling, the volumetric particle diameters Dv50 of the first particles, second particles, and precursor particles after sintering with lithium hydroxide are tested using a laser particle size analyzer, respectively, in accordance with standard GB / T 19077-2016 / ISO 13320:2009. Among them, half of the volume particle diameter Dv50 of the first particles and lithium hydroxide after sintering corresponds to the distance from the inner surface of the intermediate layer to the center of the core, half of the volume particle diameter Dv50 of the second particles and lithium hydroxide after sintering corresponds to the distance from the outer surface of the intermediate layer to the center of the core, and half of the difference between the volume particle diameter Dv50 of the second particles and lithium hydroxide after sintering and the volume particle diameter Dv50 of the first particles and lithium hydroxide after sintering corresponds to the thickness of the intermediate layer. The volume particle diameter Dv50 of the precursor particles and lithium hydroxide after sintering (referred to as D1) was used as the basis to evaluate the distance from the inner and outer surfaces of the intermediate layer to the center of the core and the thickness of the intermediate layer. In the remaining examples and comparative examples, the method for evaluating the thickness of the intermediate layer and the positional relationship of the intermediate layer was adapted and adjusted with reference to Example 1.

[0150] (c) Characterization of the cross-sectional microstructure of the positive electrode active material The resulting positive electrode piece was cut by ion beam sputtering to obtain a cross section of the positive electrode piece. The cross section of the positive electrode piece was observed with a scanning electron microscope to observe the cross-sectional morphology of the positive electrode active material particles cut in the cross section region.

[0151] (d) Initial Gram Capacity and Cycle Capacity Retention Test: In a constant temperature environment of 25°C, the battery was left standing for 5 minutes, discharged at 0.33C to 2.8V, left standing for 5 minutes, charged at 0.33C to 4.25V, then charged at a constant voltage at 4.25V until the current was ≦0.05mA, left standing for 5 minutes, and then discharged at 0.33C to 2.8V. The discharge capacity at this time was the initial capacity and was recorded as D0. Then, the battery was charged at 1C to 4.25V, then charged at a constant voltage at 4.25V until the current was ≦0.05mA, left standing for 5 minutes, and then discharged at 1C to 2.8V. The capacity was recorded as D0. n (n=1, 2...) and repeat the previous process to perform charge-discharge cycles. The discharge specific capacity at the 100th cycle is D 100 The 100-cycle discharge capacity retention rate = D 100 / D0×100%.

[0152] (e) Testing the surface of positive electrode active material particles Scanning electron microscopy was used to characterize the initial surface condition of the positive electrode active material and the surface cracking condition after 100 charge-discharge cycles. After 100 charge-discharge cycles, the entire battery was disassembled to obtain the positive electrode pieces. The positive electrode pieces were washed to remove residual electrolyte from their surfaces, immersed in N-methylpyrrolidone (NMP) until the adhesive was completely removed, and then dried to obtain a powder mixture of conductive agent and positive electrode active material particles. The powder mixture was then sieved or directly characterized (there was a significant difference between the particle sizes of the positive electrode active material and the conductive agent). The surface microstructure of the positive electrode active material particles was observed to evaluate the cracking condition, where " / " indicates almost no cracking, "+" indicates minor cracking, "++" indicates partial cracking, and "+++" indicates severe cracking.

[0153] (f) Battery volumetric energy density test The resulting battery was subjected to a 0.33C charge-discharge test using a charge-discharge tester. After charging at a 0.33C rate to 4.35V, it was subjected to a constant voltage test until the current reached 0.05C. The battery was then discharged at 0.33C until it reached 2.8V, and the discharge capacity C1 (unit: Ah) and discharge voltage V1 (unit: V) were recorded. The total volume of the battery was measured to obtain v1 (unit: L). The volumetric energy density of the battery = C1 × V1 / v1.

[0154] Related tests were carried out for Examples 1 to 34 and Comparative Examples 1 to 6, and the details of the test results are shown in Tables 1 and 2.

[0155] Table 1 Differences between Examples 1 to 34 and Comparative Examples 1 to 6 and test results

[0156] [Table 1-1]

[0157] [Table 1-2]

[0158] [Table 1-3]

[0159] [Table 1-4]

[0160] [Table 1-5]

[0161] Table 2 Differences between Examples 9-12 and 30-31 and test results

[0162] [Table 2]

[0163] Results and conclusions: Taking the data from Examples 1 to 34, Comparative Examples 1 to 6, and Table 1 together, it can be seen that the proposed methods of the present invention can improve the cracking of the positive electrode active material during charge-discharge cycling and improve the capacity retention rate during charge-discharge cycling. Furthermore, when the cross-sections of the positive electrode pieces prepared in Examples 1 to 34 were characterized using a scanning electron microscope, it was found that the cut positive electrode active material particles had a distinct porous structure between their interior and outer surface layers in the cross-sectional area (taking Example 1 and Comparative Example 2 as examples, Figures 2 and 3 show cross-sectional views of individual positive electrode active material particles in the cross-section of a positive electrode piece, respectively; comparing Figures 2 and 3 reveals that the positive electrode active material of Example 1 has a porous intermediate layer). This further explains the presence of a porous intermediate layer in the positive electrode active materials prepared using the methods of the present invention. Combining Examples 1 to 4 and Comparative Examples 1 to 6, it can be seen that, compared to doping the core with the M' element alone or forming the intermediate layer alone, combining the two methods can achieve a synergistic effect and further improve the cracking of the positive electrode active material during charge-discharge cycling. Combining Examples 1 to 34 also shows that the methods of the above-mentioned Examples of the present application can be applied to different layered positive electrode active materials containing Ni. Combining Examples 3 to 4 and 12 to 24 also shows that changing the type of M' element and the M" source used to form the intermediate layer can improve the cracking of the positive electrode active material during charge-discharge cycling and also improve the capacity retention rate during the charge-discharge cycle. Combining Examples 3 to 11 also shows that controlling the doping amount of M' and the amount of the M" source used to form the intermediate layer relative to lithium within a predetermined range is advantageous for further improving the cycle capacity retention rate of the positive electrode active material and achieving high energy density. Furthermore, combining Examples 25 to 28, it can be seen that controlling the distance from the inner and outer surfaces of the intermediate layer to the center of the core and the thickness distribution of the intermediate layer within a predetermined range is advantageous for further improving the cycle capacity retention rate of the positive electrode active material.Furthermore, combining Examples 12 and 30 to 31, it can be seen that increasing the distribution width of the volume particle size of the positive electrode active material is advantageous for obtaining a relatively high energy density.

[0164] Finally, it should be noted that the above embodiments are used only to explain the technical solutions of the present application and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some or all of the technical features with equivalents. Such modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of the claims and description of the present application. In particular, as long as there is no structural contradiction, the technical features mentioned in the embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions included within the scope of the claims. [Explanation of symbols]

[0165] 11: Core, 12: Intermediate layer, 13: Outer shell layer, 1: Battery, 2: Battery module, 3: Battery pack, 4: Upper case, 5: Lower case.

Claims

1. A positive electrode active material, Li ａ１ Ni ｘ１ M ｙ１ M' ｚ１ O ｍ１ R ｎ１ wherein 0.9≦a1≦1.1, 0.6≦x1<1, 0≦y1≦0.4, 0<z1≦0.01, 1.9≦m1≦2.2, 0≦n1≦0.1, M includes at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, and Ce, M′ includes at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti, or Ga, and R includes at least one element of F, Cl, or S; a mid layer covering at least a portion of the outer surface of the core and having a porous structure; a coating layer having at least a portion of an outer surface of the intermediate layer; ａ２ Ni ｘ２ M ｙ２ M' ｚ２ O ｍ２ R ｎ２ and an outer shell layer comprising: 0.9≦a2≦1.1, 0.6≦x2<1, 0≦y2≦0.4, 0≦z2≦0.01, 1.9≦m2≦2.2, and 0≦n2≦0.1; Positive electrode active material.

2. The intermediate layer is M'' ｐ O ｑ wherein 1≦p≦2, 2≦q≦3, and M″ comprises at least one element of B, Al, or Si; The positive electrode active material of claim 1 .

3. In the positive electrode active material, the ratio of the number of moles of M″ element to the number of moles of Li element is (0.005 to 0.02):(0.9 to 1.1). The positive electrode active material of claim 2 .

4. In the positive electrode active material, the ratio of the number of moles of M″ element to the number of moles of Li element is (0.008 to 0.012):(0.9 to 1.1). The positive electrode active material according to claim 2 or 3.

5. The positive electrode active material according to any one of claims 1 to 4, wherein z2>0.

6. The core is Li ａ１ Ni ｘ１ Co ｙ１１ Mn ｙ１２ M' ｚ１ O ｍ１ R ｎ１ and / or, wherein 0≦y11≦0.2, 0≦y12≦0.2, and y11 and y12 are not 0 at the same time; The outer shell layer is Li ａ２ Ni ｘ２ Co ｙ２１ Mn ｙ２２ M' ｚ２ O ｍ２ R ｎ２ y21≦y21≦0.2, 0≦y22≦0.2, and y21 and y22 are not 0 at the same time; The positive electrode active material according to any one of claims 1 to 5.

7. 0.002≦z1≦0.008, and / or 0.002≦z2≦0.008; The positive electrode active material according to any one of claims 1 to 6.

8. The particle diameter of the positive electrode active material is D １ and the distance from the inner surface of the mid layer to the center of the core is 0.3D １ or more, and the distance from the outer surface of the mid layer to the center of the core is 0.4D １ and / or The thickness of the intermediate layer is 0.05D １ ~0.0625D １ That is, The positive electrode active material according to any one of claims 1 to 7. [Request Item 9] [Number 1]

10. 1. A method for producing a positive electrode active material, comprising: mixing core raw materials including a nickel source, an M source, and an M' source to obtain a mixed solution, and performing a first precipitation reaction on the obtained mixed solution to obtain first particles; mixing a solution formed using an intermediate layer raw material with the first particles to perform a second precipitation reaction to obtain second particles; mixing an outer shell layer raw material containing a nickel source and an M source, mixing the resulting mixture with the second particles, and performing a third precipitation reaction to obtain precursor particles; mixing the precursor particles with a lithium source and sintering the mixture to obtain a positive electrode active material; the precipitation product formed on the outer surface of the first particle by the second precipitation reaction forms a porous structure by the sintering; The positive electrode active material is Li ａ１ Ni ｘ１ M ｙ１ M' ｚ１ O ｍ１ R ｎ１ wherein 0.9≦a1≦1.1, 0.6≦x1<1, 0≦y1≦0.4, 0<z1≦0.01, 1.9≦m1≦2.2, 0≦n1≦0.1, M includes at least one element of Co, Mn, Al, Ta, Mg, Mo, Ga, Sn, Ge, Te, La, and Ce, M′ includes at least one element of Y, La, Mo, Zr, W, Sb, Nb, Te, Sr, Ti, or Ga, and R includes at least one element of F, Cl, or S; a mid layer covering at least a portion of the outer surface of the core and having a porous structure; a coating layer having at least a portion of an outer surface of the intermediate layer; ａ２ Ni ｘ２ M ｙ２ M' ｚ２ O ｍ２ R ｎ２ and an outer shell layer comprising: 0.9≦a2≦1.1, 0.6≦x2<1, 0≦y2≦0.4, 0≦z2≦0.01, 1.9≦m2≦2.2, and 0≦n2≦0.1; A method for producing a positive electrode active material.

11. the intermediate layer raw material includes an M″ source including a compound having at least one element of B, Al, or Si; 11. A method for producing the positive electrode active material of claim 10.

12. The positive electrode active material according to any one of claims 1 to 9, or the positive electrode active material produced by the method for producing the positive electrode active material according to claim 10 or 11, Positive electrode piece.

13. A battery comprising the positive electrode piece of claim 12.

14. An electrical device comprising the battery of claim 13.

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