Lithium-ion secondary batteries and electrical devices

Abstract

This application provides a lithium-ion secondary battery and an electrical device. The lithium-ion secondary battery includes a positive electrode sheet, which includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer has Dv10 and Dv90 satisfying the following conditions: Dv10 is 1.8 μm to 3 μm, and Dv10 / Dv90 is 0.14 to 0.17. By designing the positive active material, the energy density of the lithium-ion secondary battery can be effectively improved.

Description

[0001] Related applications

[0002] This application claims priority to patent application No. PCT / CN2025 / 104475, filed on June 27, 2025, entitled “Lithium-ion Secondary Battery and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and more particularly to lithium-ion secondary batteries and electrical devices. Background Technology

[0004] In recent years, lithium-ion rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. With the continuous expansion of the application scope of lithium-ion rechargeable batteries, correspondingly higher requirements are being placed on battery performance.

[0005] For example, the energy density of lithium-ion rechargeable batteries is an important indicator for measuring battery performance. However, the energy density of traditional lithium-ion rechargeable batteries needs further improvement. Summary of the Invention

[0006] The first aspect of this application provides a lithium-ion secondary battery, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer located on at least one surface of the positive current collector, wherein the positive active material of the positive active layer has Dv10 and Dv90 satisfying the following: Dv10 is 1.8μm~3μm, and Dv10 / Dv90 is 0.14~0.17.

[0007] In lithium-ion secondary batteries, the compaction density of the positive electrode sheet has a significant impact on the battery's energy density, and increasing the compaction density of the positive electrode sheet is expected to improve the battery's energy density. During the processing of the positive electrode sheet, increasing the cold pressing pressure can increase the compaction density, but this also increases the risk of current collector breakage. In the lithium-ion secondary battery of the first aspect of this application, by adjusting the ratio of positive electrode active materials Dv10 and Dv90, smaller particles can be effectively encouraged to fill the gaps between larger particles. This allows for an increase in the compaction density of the positive electrode sheet without increasing the cold pressing pressure or preventing current collector breakage, thereby improving the battery's energy density.

[0008] In some embodiments, the Dv90 of the positive electrode active material is 13 μm to 18 μm. Within this range, Dv90 allows for better adaptation between larger and smaller particles, further promoting the filling of gaps between smaller particles and thus further facilitating a balance between battery energy density and kinetic performance.

[0009] In some embodiments, the Dv50 of the positive electrode active material is 6 μm to 8 μm. This allows for better filling and contact between the particles of the positive electrode active material, further improving the energy density and kinetic performance of the battery.

[0010] In some embodiments, the positive electrode active material includes monocrystalline particles and polycrystalline particles. Monocrystalline particles can maintain good integrity and stability. Polycrystalline particles have better compaction properties, which is beneficial for improving the compaction density of the positive electrode. The combination of polycrystalline and monocrystalline particles allows the positive electrode sheet to achieve both high compaction density and good stability, thereby enabling the battery to better balance high energy density and good kinetic performance. Optionally, the mass ratio of the monocrystalline particles to the polycrystalline particles is 6:4 to 8:2.

[0011] In some embodiments, the positive electrode active material comprises a layered lithium-containing transition metal oxide. Optionally, the layered lithium-containing transition metal oxide has the chemical formula Li. x (Ni a Co b Mn c ) 1-d M d O 2-y A y Wherein, 0.2≤x≤1.2, 0.8≤a≤1, 0≤b≤1, 0≤c≤1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

[0012] In some embodiments, the layered lithium-containing transition metal oxide accounts for 90% to 100% of the mass percentage of the positive electrode active material.

[0013] In some embodiments, the positive electrode active material comprises a lithium phosphate with an olivine structure.

[0014] In some embodiments, the positive electrode active material comprises a layered lithium-containing transition metal oxide and a lithium-containing phosphate with an olivine structure, wherein the lithium-containing phosphate with an olivine structure accounts for less than or equal to 10% by mass of the positive electrode active material.

[0015] In some embodiments, the positive electrode active material includes a first particle, a second particle, a third particle, a fourth particle, and a fifth particle. The average particle size ratio of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle is 1:(0.4~0.5):(0.2~0.3):(0.1~0.2):(0.1~0.15), and the mass ratio of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle is 1:(0.8~1.2):(1.5~2.5):(6~10):(6~10). This gradation of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle allows smaller particles to better fill the pores between larger particles, further improving the compaction density of the positive electrode sheet.

[0016] In some embodiments, the average particle size of the first particle is 10 μm to 20 μm.

[0017] In some embodiments, the average particle size of the second particle is 5 μm to 10 μm.

[0018] In some embodiments, the average particle size of the third particle is 3 μm to 5 μm.

[0019] In some embodiments, the average particle size of the fourth particle is 2 μm to 3 μm.

[0020] In some embodiments, the average particle size of the fifth particle is 1 μm to 2 μm.

[0021] In some embodiments, the first particle accounts for 5% to 10% of the mass percentage of the positive electrode active material.

[0022] In some embodiments, the second particle accounts for 5% to 10% of the mass percentage of the positive electrode active material.

[0023] In some embodiments, the third particle accounts for 15% to 20% of the mass percentage of the positive electrode active material.

[0024] In some embodiments, the fourth particle accounts for 30% to 35% of the mass percentage of the positive electrode active material.

[0025] In some embodiments, the fifth particle accounts for 30% to 35% of the mass percentage of the positive electrode active material.

[0026] In some embodiments, the first particle comprises a polycrystalline particle.

[0027] In some embodiments, the second particle comprises a polycrystalline particle.

[0028] In some embodiments, the third particle includes one or more of monocrystalline and polycrystalline particles.

[0029] In some embodiments, the fourth particle includes one or more of monocrystalline and polycrystalline particles.

[0030] In some embodiments, the fifth particle includes one or more of single-crystal particles and polycrystalline particles.

[0031] In some embodiments, the first particle comprises a layered lithium-containing transition metal oxide, the second particle comprises one or more of a layered lithium-containing transition metal oxide and an olivine-structured lithium-containing phosphate, the third particle comprises a layered lithium-containing transition metal oxide, the fourth particle comprises a layered lithium-containing transition metal oxide, and the fifth particle comprises a layered lithium-containing transition metal oxide. Optionally, the layered lithium-containing transition metal oxide accounts for 90% to 100% of the mass percentage of the positive electrode active material; the olivine-structured lithium-containing phosphate accounts for less than or equal to 10% of the mass percentage of the positive electrode active material.

[0032] In some embodiments, the compaction density of the positive electrode sheet is 3.5 g / cm³. 3 ~4.0g / cm 3 By designing the positive electrode active material, the positive electrode sheet can have a high compaction density.

[0033] A second aspect of this application provides an electrical device. The electrical device includes the lithium-ion secondary battery described in the first aspect. Attached Figure Description

[0034] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 This is a schematic diagram of a lithium-ion secondary battery according to one embodiment of this application.

[0036] Figure 2 for Figure 1 An exploded view of a lithium-ion secondary battery according to an embodiment of this application is shown.

[0037] Figure 3 This is a schematic diagram of an electrical device that uses a lithium-ion secondary battery as a power source according to an embodiment of this application.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1. Lithium-ion secondary battery; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0040] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0043] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0046] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] In this application, unless otherwise stated, “A, such as B” means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0048] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0049] In this application, unless otherwise specified, "lithium-ion secondary battery" refers to a basic unit capable of converting chemical energy into electrical energy, and more generally includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, lithium ions repeatedly insert and extract between the positive and negative electrode.

[0050] During the processing of positive electrode sheets, increasing the cold pressing pressure can increase the compaction density of the positive electrode sheets, but increasing the cold pressing pressure will increase the risk of breakage of the positive current collector.

[0051] One embodiment of this application provides a lithium-ion secondary battery, including a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer has Dv10 and Dv90 satisfying the following conditions: Dv10 is 1.8 μm to 3 μm, and Dv10 / Dv90 is 0.14 to 0.17. Dv10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the positive active material. Dv90 represents the particle size corresponding to a cumulative volume distribution percentage of 90% for the positive active material. In this embodiment, by adjusting the ratio of positive active materials Dv10 and Dv90, smaller particles can be effectively encouraged to fill the gaps between larger particles. This improves the compaction density of the positive electrode sheet without increasing the cold pressing pressure or interrupting the flow of the positive current collector, thereby increasing the energy density of the battery.

[0052] Furthermore, in some embodiments of this application, since it is not necessary to increase the cold pressing pressure, the risk of cracks or even breakage of the positive electrode active material particles can be effectively reduced, thereby reducing the side reactions at the positive electrode interface, reducing the consumption of active lithium ions, and improving the cycle performance of the battery.

[0053] Furthermore, the Dv10 of the positive electrode active material, within the range of 1.8 μm to 3 μm, allows for good contact between smaller and larger particles, which helps to shorten the lithium-ion transport path, reduce lithium-ion transport resistance, and thus improve the battery's kinetic performance. Therefore, in this application, through the design of the positive electrode active material, a lithium-ion secondary battery can achieve both high energy density and good kinetic performance.

[0054] In this application, Dv10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the positive electrode active material. Dv90 represents the particle size corresponding to a cumulative volume distribution percentage of 90% for the positive electrode active material. It is understood that the testing of Dv10 and Dv90 can refer to GB / T 19077-2016, using a laser particle size analyzer, such as a Malvern Master Size 3000.

[0055] Optionally, the Dv10 / Dv90 of the positive electrode active material can be 0.14, 0.15, 0.16, 0.17, or any value within the range of any two of the above values. More preferably, Dv10 / Dv90 is 0.15 to 0.16.

[0056] Optionally, the Dv10 of the positive electrode active material can be 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, or any value within the range of any two of the above values. When the Dv10 of the positive electrode active material is less than 1.8 μm, smaller particles tend to agglomerate, blocking the gaps between larger particles. This makes it difficult for smaller particles to fully fill the spaces between larger particles, resulting in poorer contact between larger and smaller particles and prolonging the lithium-ion transport path. When the Dv10 of the positive electrode active material is greater than 3 μm, smaller particles also have difficulty fully filling the spaces between larger particles, leading to poorer contact between larger and smaller particles and prolonging the lithium-ion transport path. Therefore, in this application, when the Dv10 is between 1.8 μm and 3 μm, smaller particles can fully fill the gaps between larger particles, maintaining good contact between smaller and larger particles. This helps to shorten the lithium-ion transport path, reduce lithium-ion transport resistance, and thus improve the kinetic performance of the battery. Alternatively, Dv10 can be 2.2 μm to 2.4 μm.

[0057] In some embodiments, the Dv90 of the positive electrode active material is 13 μm to 18 μm. Within this range, Dv90 allows for better adaptation between larger and smaller particles, further promoting the filling of gaps between smaller particles and thus further improving the balance between battery energy density and kinetic performance. Optionally, the Dv90 of the positive electrode active material can be 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or any value within the range of any two of the above values.

[0058] In some embodiments, the Dv50 of the positive electrode active material is 6 μm to 8 μm. This allows for better filling and contact between the particles of the positive electrode active material, further improving the energy density and kinetic performance of the battery. Optionally, the Dv50 of the positive electrode active material can be 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, 7.2 μm, 7.5 μm, 7.8 μm, 8 μm, or any value within the range of any two of the above values.

[0059] It is understandable that Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the positive electrode active material. Dv50 testing can be performed according to GB / T 19077-2016 using a laser particle size analyzer, such as a Malvern Master Size 3000.

[0060] In some embodiments, the positive electrode active material includes monocrystalline particles and polycrystalline particles. Monocrystalline particles typically refer to a single particle composed of one or no more than five primary particles. Due to the smaller number of primary particles and grain boundaries in monocrystalline particles, they can maintain better integrity and stability when affected by external forces, temperature changes, and other factors. Polycrystalline particles have better compaction properties, which is beneficial for improving the compaction density of the positive electrode. The combination of polycrystalline and monocrystalline particles allows the positive electrode sheet to achieve both high compaction density and good stability, thereby enabling the battery to better balance high energy density and good kinetic performance.

[0061] Optionally, the mass ratio of single-crystal particles to polycrystalline particles is 6:4 to 8:2. For example, the mass ratio of single-crystal particles to polycrystalline particles is 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, or any value within the range of any two of the above values.

[0062] In this application, the mass ratio of single-crystal particles to polycrystalline particles can be obtained using testing methods known in the art. As an example, the mass ratio of single-crystal particles to polycrystalline particles can be tested as follows: The positive electrode active layer is sliced ​​along its thickness direction, and the crystal structure of the particles in the resulting cross-section is observed to determine the number of single-crystal and polycrystalline particles. Then, the volumes of the single-crystal and polycrystalline particles are calculated based on their dimensions in the cross-section. Since the density of single-crystal and polycrystalline particles is equal, their mass ratio can be determined by the volume ratio of the single-crystal and polycrystalline particles.

[0063] In some embodiments, the positive electrode active material comprises a layered lithium-containing transition metal oxide. Optionally, the layered lithium-containing transition metal oxide has the chemical formula Li. x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where 0.2≤x≤1.2, 0.8≤a≤1, 0≤b≤1, 0≤c≤1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy, and Te, and A includes one or more of N, P, S, and halogen elements. The chemical formula is Li. x (Ni a Co b Mn c ) 1-d M d O 2-y A yLayered lithium-containing transition metal oxides have high specific capacity, which can further improve the energy density of lithium-ion secondary batteries.

[0064] Understandably, 'a' is typically used to represent the nickel content in layered lithium-containing transition metal oxides. A larger 'a' indicates a higher nickel content, while a smaller 'a' indicates a lower nickel content. As some possible examples of 'a', 'a' can be 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, 1, or any value within the range of any two of the above values.

[0065] Understandably, 'b' is typically used to represent the cobalt content in layered lithium-containing transition metal oxides. A larger 'b' indicates a higher cobalt content, while a smaller 'b' indicates a lower cobalt content. As some possible examples of 'b', it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value within the range of any two of the above values.

[0066] Understandably, 'c' is typically used to represent the manganese content in layered lithium-containing transition metal oxides. A larger 'c' indicates a higher manganese content, while a smaller 'c' indicates a lower manganese content. As some possible examples of 'c', it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value within the range of any two of the above values.

[0067] Understandably, d is typically used to represent the content of element M in layered lithium-containing transition metal oxides. A larger d indicates a higher content of element M, while a smaller d indicates a lower content of element M. As some possible examples of d, d can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and any value within the range of any two of the above values. Optionally, 0 ≤ d ≤ 0.05.

[0068] Understandably, x is typically used to represent the lithium content in layered lithium-containing transition metal oxides. A larger x indicates a higher lithium content, while a smaller x indicates a lower lithium content. As some possible examples of x, x can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, and any value within the range of any two of the above values.

[0069] Understandably, y is typically used to represent the content of element A in layered lithium-containing transition metal oxides. A larger y indicates a higher content of element A, while a smaller y indicates a lower content of element A. As some possible examples of y, y can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, and any value within the range of any two of the above values. Optionally, 0 ≤ y ≤ 0.05.

[0070] It is understandable that A includes one or more of N, P, S and halogen elements, where halogen elements can be F, Cl, Br, etc.

[0071] Optionally, the lithium-containing transition metal oxide includes LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.9 Co 0.09 Mn 0.01 O2, LiNi 0.92 Co 0.05 Mn 0.03 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, etc.

[0072] Optionally, the chemical formula is Li x (Ni a Co b Mn c ) 1-d M d O 2-y A yLayered lithium-containing transition metal oxides account for 90% to 100% of the mass of the positive electrode active material. For example, Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y The mass percentage of layered lithium-containing transition metal oxides in the positive electrode active material is 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, and any value within the range of any two of the above values.

[0073] Optionally, the chemical formula is Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y The layered lithium-containing transition metal oxide accounts for 95% to 98.5% of the mass percentage of the positive electrode active layer. For example, the chemical formula Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y The mass percentage of the layered lithium-containing transition metal oxide in the positive electrode active layer is 95%, 96%, 97%, 98%, 98.5%, or any value within the range of any two of the above values.

[0074] In some embodiments, the positive electrode active material may further include one or more of the following materials: lithium cobalt oxide, lithium manganese oxide, lithium manganese cobalt oxide, and modified compounds thereof. Non-limiting examples of lithium cobalt oxide may include LiCoO2. Non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.

[0075] In some embodiments, the positive electrode active material includes a lithium phosphate with an olivine structure. The lithium phosphate with an olivine structure exhibits good cycle stability, which is beneficial for improving battery cycle performance.

[0076] Optionally, lithium-containing phosphates may include at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Lithium-containing phosphates may also include one or more of lithium manganese phosphate and lithium manganese phosphate and carbon composites.

[0077] Optionally, the positive electrode active material includes layered lithium-containing transition metal oxides and olivine-structured lithium-containing phosphates. Optionally, the layered lithium-containing transition metal oxides account for more than or equal to 90% of the mass of the positive electrode active material. The olivine-structured lithium-containing phosphates account for less than or equal to 10% of the mass of the positive electrode active material. For example, the olivine-structured lithium-containing phosphates account for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0078] Optionally, the lithium phosphate with an olivine structure accounts for less than or equal to 5% of the mass percentage of the positive electrode active layer. For example, the lithium phosphate with an olivine structure accounts for 1%, 2%, 3%, 4%, 5% of the mass percentage of the positive electrode active layer, or any value within the range of any two of the above values.

[0079] In some embodiments, the positive electrode active material includes a first particle, a second particle, a third particle, a fourth particle, and a fifth particle. The average particle size ratio of the first, second, third, fourth, and fifth particles is 1:(0.4~0.5):(0.2~0.3):(0.1~0.2):(0.1~0.15), and the mass ratio of the first, second, third, fourth, and fifth particles is 1:(0.8~1.2):(1.5~2.5):(6~10):(6~10). This gradation of the first, second, third, fourth, and fifth particles allows smaller particles to better fill the pores between larger particles, further improving the compaction density of the positive electrode sheet.

[0080] Optionally, the ratio of the average particle size of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle can be 1:0.4:0.2:0.1:0.1, 1:0.414:0.225:0.177:0.116, 1:0.45:0.25:0.2:0.15, 1:0.5:0.3:0.2:0.15, or any value within the range of ratios formed by any of the above values.

[0081] Optionally, the mass ratio of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle can be 1:0.8:1.5:6:6, 1:1:2:8:8, 1:1.2:2.5:10:10, or any value within the range of the above ratios.

[0082] In some embodiments, the average particle size of the first particle is 10 μm to 20 μm. For example, the average particle size of the first particle can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any value within the range of any two of the above values. The first particle accounts for 5% to 10% of the mass of the positive electrode active material. For example, the first particle accounts for 5%, 6%, 7%, 8%, 9%, 10% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0083] The average particle size of the second particle is 5μm to 10μm. For example, the average particle size of the second particle can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or any value within the range of any two of the above values. The second particle accounts for 5% to 10% of the mass of the positive electrode active material. For example, the second particle accounts for 5%, 6%, 7%, 8%, 9%, 10% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0084] The average particle size of the third particle is 3μm to 5μm. For example, the average particle size of the third particle can be 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or any value within the range of any two of the above values. The third particle accounts for 15% to 20% of the mass of the positive electrode active material. For example, the third particle accounts for 15%, 16%, 17%, 18%, 19%, 20% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0085] The average particle size of the fourth particle is 2μm to 3μm. For example, the average particle size of the fourth particle can be 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, or any value within the range of any two of the above values. The fourth particle accounts for 30% to 35% of the mass of the positive electrode active material. For example, the fourth particle accounts for 30%, 31%, 32%, 33%, 34%, 35% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0086] The average particle size of the fifth particle is 1 μm to 2 μm. For example, the average particle size of the fifth particle can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, or any value within the range of any two of the above values. The fifth particle accounts for 30% to 35% of the mass of the positive electrode active material. For example, the fifth particle accounts for 30%, 31%, 32%, 33%, 34%, 35% of the mass of the positive electrode active material, or any value within the range of any two of the above values.

[0087] In this application, the average particle size can be measured by a laser particle size analyzer.

[0088] In this application, the mass percentage of particles in the active material can be tested by the following methods: elemental mass can be obtained by ICP testing, and molecular formula can be obtained by analyzing the elemental composition of individual particles by EDX analysis; the mass percentage of particles in the active material can be calculated based on the molecular formula and the elemental percentage in ICP.

[0089] In some embodiments, the first particle comprises a polycrystalline particle. The second particle comprises a polycrystalline particle. The third particle comprises one or more of a monocrystalline particle and a polycrystalline particle. The fourth particle comprises one or more of a monocrystalline particle and a polycrystalline particle. The fifth particle comprises one or more of a monocrystalline particle and a polycrystalline particle.

[0090] In some embodiments, the first particle comprises a layered lithium-containing transition metal oxide, the second particle comprises one or more of a layered lithium-containing transition metal oxide and an olivine-structured lithium phosphate, the third particle comprises a layered lithium-containing transition metal oxide, the fourth particle comprises a layered lithium-containing transition metal oxide, and the fifth particle comprises a layered lithium-containing transition metal oxide. When the first, second, third, fourth, and fifth particles all comprise layered lithium-containing transition metal oxides, the energy density of the battery can be further improved due to the higher specific capacity of the layered lithium-containing transition metal oxides. When the second particle comprises an olivine-structured lithium phosphate, the discharge performance of the battery can be improved because the olivine-structured lithium phosphate has better discharge capability at low temperatures and low voltage conditions. Furthermore, the second particle comprising an olivine-structured lithium phosphate, where the olivine-structured lithium phosphate falls within the average particle size range and the mass percentage range, can further improve the kinetic performance of the battery. It is understood that the layered lithium-containing transition metal oxide and the olivine-structured lithium phosphate can be selected correspondingly as described above, and will not be elaborated further here.

[0091] Optionally, the layered lithium-containing transition metal oxide accounts for 90% to 100% of the mass of the positive electrode active material; the lithium-containing phosphate with olivine structure accounts for less than or equal to 10% of the mass of the positive electrode active material.

[0092] In some embodiments, the compaction density of the positive electrode sheet is 3.5 g / cm³. 3 ~4g / cm 3 This application utilizes a design to achieve a high compaction density in the positive electrode material. For example, the compaction density of the positive electrode can be 3.5 g / cm³. 3 3.6g / cm 3 3.7g / cm3 3.8g / cm 3 3.9g / cm 3 4g / cm 3 And any value within the range consisting of any two of the above values.

[0093] The compaction density of the electrode sheet in this application can be tested using the following method: Disassemble the battery, take the electrode sheet, punch it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1; measure the thickness of the active layer and record it as T; then wipe off the weighed active layer, weigh the remaining electrode sheet, and record it as M0. The compaction density of the active layer PD = (M1 - M0) / (S1 × T). It can be understood that when the electrode sheet is a positive electrode sheet, the compaction density of the positive electrode active layer can be tested. When the electrode sheet is a negative electrode sheet, the compaction density of the negative electrode active layer can be tested.

[0094] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. Optionally, the binder accounts for 0.7% to 3% of the mass percentage of the positive electrode active layer. For example, the binder percentage of the positive electrode active layer may be 0.7%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any value within the range of any two of the above values.

[0095] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the conductive agent accounts for 0.8% to 2% of the mass percentage of the positive electrode active layer. For example, the mass percentage of the conductive agent in the positive electrode active layer may be 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any value within the range of any two of the above values.

[0096] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on a polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0097] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector.

[0098] It is understandable that lithium-ion secondary batteries also include a negative electrode. The negative electrode includes a negative current collector and a negative active layer located on at least one surface of the negative current collector.

[0099] In some embodiments, the negative electrode active material of the negative electrode active layer may include negative electrode active materials known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Optionally, graphite includes one or more of artificial graphite and natural graphite. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, and silicon-carbon composites. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0100] Optionally, the negative electrode active material accounts for 91% to 98% of the mass of the negative electrode active layer. For example, the mass percentage of the negative electrode active material in the negative electrode active layer can be 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any value within the range of any two of the above values.

[0101] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Optionally, the binder accounts for 1% to 5% of the mass percentage of the negative electrode active layer. Optionally, the binder's mass percentage of the negative electrode active layer may be 1%, 2%, 3%, 4%, 5%, or any value within the range of any two of the above values.

[0102] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the conductive agent accounts for 0.2% to 2% of the mass percentage of the negative electrode active layer. Optionally, the conductive agent accounts for 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any value within the range of any two of the above values.

[0103] In some embodiments, the negative electrode active layer may optionally include other additives, such as a thickener. The thickener may be sodium carboxymethyl cellulose (CMC-Na). Optionally, the thickener accounts for 0.8% to 2% of the mass of the negative electrode active layer. Optionally, the mass percentage of the thickener in the negative electrode active layer may be 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any value within the range of any two of the above values.

[0104] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0105] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent to form a negative electrode slurry. Optionally, a non-limiting example of a solvent is deionized water. The negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet is obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0106] In some embodiments, the lithium-ion secondary battery also includes an electrolyte. The electrolyte serves to conduct ions between the positive and negative electrode plates.

[0107] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0108] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0109] In some embodiments, the solvent may include one or more of the following: 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), butenyl carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0110] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0111] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC).

[0112] It is understood that lithium-ion secondary batteries also include a separator. The separator is located between the positive electrode and the negative electrode. This application does not impose any particular restriction on the type of separator; any well-known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0114] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0115] In some embodiments, the lithium-ion secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0116] In some embodiments, the outer packaging of the lithium-ion secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] This application does not impose any particular limitation on the shape of the lithium-ion secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured lithium-ion secondary battery 1.

[0118] In some implementations, refer to Figure 2 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The lithium-ion secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to actual needs.

[0119] In some implementations, the lithium-ion secondary battery can be a single battery cell, a battery module, or a battery pack.

[0120] The battery module includes at least one lithium-ion secondary battery. The battery module may contain one or more lithium-ion secondary batteries, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0121] In a battery module, multiple lithium-ion secondary batteries can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium-ion secondary batteries can be secured using fasteners.

[0122] Optionally, the battery module may also include a housing with a receiving space in which multiple lithium-ion secondary batteries are housed.

[0123] In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0124] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0125] In addition, this application also provides an electrical device, which includes the lithium-ion secondary battery provided in this application. The battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0126] As an electrical device, lithium-ion rechargeable batteries can be selected according to its usage requirements.

[0127] Figure 3 Here is an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device, a battery pack or battery module can be used.

[0128] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0129] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0130] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0131] Example 1

[0132] (1) Positive electrode plate

[0133] LiNi 0.8 Co0.1 Mn 0.1 O2, polyvinylidene fluoride (PVDF), and super P were mixed in a weight ratio of 95:1.5:3.5, and N-methylpyrrolidone (N-methylpyrrolidone) was added as solvent. The mixture was stirred to prepare a positive electrode slurry. This slurry was then coated onto a 13μm thick aluminum foil, dried, and subjected to 50T cold pressing, slitting, and cutting to form the positive electrode sheet. No breakage occurred in the aluminum foil during the cold pressing process. LiNi... 0.8 Co 0.1 Mn 0.1 The O2 particles consist of a first particle, a second particle, a third particle, a fourth particle, and a fifth particle. The first particle has an average particle size of 15.0 μm and accounts for 8% of the mass of the positive electrode active material. The second particle has an average particle size of 6.2 μm and accounts for 7% of the mass of the positive electrode active material. The third particle has an average particle size of 3.4 μm and accounts for 15% of the mass of the positive electrode active material. The fourth particle has an average particle size of 2.7 μm and accounts for 35% of the mass of the positive electrode active material. The fifth particle has an average particle size of 1.7 μm and accounts for 35% of the mass of the positive electrode active material. All particles—first, second, third, fourth, and fifth—are polycrystalline particles.

[0134] (2) Negative electrode plate

[0135] Graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed in a weight ratio of 97:0.8:0.9:1.3, and deionized water was added and stirred to prepare a negative electrode slurry. The negative electrode slurry was then coated onto a current collector copper foil, dried, and subjected to cold pressing, slitting, and cutting to form a negative electrode sheet.

[0136] (3) Separating membrane

[0137] Polyethylene film is used as the separation membrane.

[0138] (4) Electrolyte

[0139] In an argon-atmospheric glove box with a water content of <10 ppm, diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed at a volume ratio of 1:1 to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent at a concentration of 1.0 mol / L.

[0140] (5) Lithium-ion secondary battery

[0141] The positive electrode, separator, and negative electrode are prepared in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain a bare cell, and tabs are welded on. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion secondary battery is obtained.

[0142] Example 2

[0143] Compared with Example 1, Example 2 differs in that the first, second, and third particles are polycrystalline, while the fourth and fifth particles are monocrystalline.

[0144] Example 3

[0145] The difference between Example 3 and Example 1 is that LiNi is used. 0.8 Co 0.1 Mn 0.1 O2 replaced with LiNi 0.9 Co 0.09 Mn 0.01 O2.

[0146] Example 4

[0147] The difference between Example 4 and Example 1 is that LiNi is used. 0.8 Co 0.1 Mn 0.1 O2 was replaced with lithium iron phosphate.

[0148] Example 5

[0149] The difference between Example 1 and Example 5 is that the second particle is replaced with lithium iron phosphate.

[0150] Comparative Examples 1-2

[0151] Compared with Example 1, Comparative Examples 1 and 2 differ in that Dv10, Dv50, and Dv90 are different. See Table 1 for details.

[0152] Comparative Example 3

[0153] Compared with Example 4, Comparative Example 3 differs in that Dv10, Dv50, and Dv90 are different. See Table 1 for details.

[0154] Test case

[0155] The compaction density of the positive electrode sheets in the examples and comparative examples was tested, and the results are shown in Table 1.

[0156] Table 1

[0157]

[0158] In Table 1, the units for Dv10, Dv50, and Dv90 are μm. The unit for compacted density is g / cm³. 3 As can be seen from Table 1, when the main material of the positive electrode active material is the same, such as in Examples 1-3, 5 and Comparative Examples 1-2 where the main material of the positive electrode active material is a layered lithium-containing transition metal oxide, or in Examples 3 and Comparative Examples 3 where the main material of the positive electrode active material is lithium iron phosphate, and the positive electrode active material satisfies the following conditions: Dv10 is 1.8μm~3μm and Dv10 / Dv90 is 0.14~0.17, the positive electrode sheet has a high compaction density.

[0159] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A lithium-ion secondary battery, characterized in that, The device includes a positive electrode sheet, which comprises a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer has Dv10 and Dv90 satisfying the following conditions: Dv10 is 1.8μm~3μm, Dv90 is 14.8μm~18μm, and Dv10 / Dv90 is 0.14~0.

17. The positive electrode active material includes a first particle, a second particle, a third particle, a fourth particle, and a fifth particle. The average particle size ratio of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle is 1:(0.4~0.5):(0.2~0.3):(0.1~0.2):(0.1~0.15); the average particle size of the first particle is 10μm~20μm. The first particle comprises a layered lithium-containing transition metal oxide, the second particle comprises one or more of a layered lithium-containing transition metal oxide and a lithium-containing phosphate with an olivine structure, the third particle comprises a layered lithium-containing transition metal oxide, the fourth particle comprises a layered lithium-containing transition metal oxide, and the fifth particle comprises a layered lithium-containing transition metal oxide. The layered lithium-containing transition metal oxide accounts for 90% to 100% of the mass percentage of the positive electrode active material; The positive electrode active material satisfies one or more of the following characteristics: (1) The first particle accounts for 5% to 10% of the mass percentage of the positive electrode active material; (2) The second particle accounts for 5% to 10% of the mass of the positive electrode active material; (3) The third particle accounts for 15% to 20% of the mass of the positive electrode active material; (4) The fourth particle accounts for 30% to 35% of the mass of the positive electrode active material; (5) The fifth particle accounts for 30% to 35% of the mass of the positive electrode active material.

2. The lithium-ion secondary battery according to claim 1, characterized in that, The Dv50 of the positive electrode active material is 6μm~8μm.

3. The lithium-ion secondary battery according to any one of claims 1 to 2, characterized in that, The positive electrode active material includes single-crystal particles and polycrystalline particles.

4. The lithium-ion secondary battery according to claim 3, characterized in that, The mass ratio of the single crystal particles to the polycrystalline particles is 6:4 to 8:

2.

5. The lithium-ion secondary battery according to any one of claims 1 to 2 and 4, characterized in that, The chemical formula of the layered lithium-containing transition metal oxide is Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y Wherein, 0.2≤x≤1.2, 0.8≤a≤1, 0≤b≤1, 0≤c≤1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

6. The lithium-ion secondary battery according to any one of claims 1 to 2 and 4, characterized in that, The positive electrode active material includes lithium phosphate with an olivine structure.

7. The lithium-ion secondary battery according to claim 6, characterized in that, The positive electrode active material comprises a layered lithium-containing transition metal oxide and a lithium-containing phosphate with an olivine structure, wherein the lithium-containing phosphate with an olivine structure accounts for less than or equal to 10% of the mass percentage of the positive electrode active material.

8. The lithium-ion secondary battery according to any one of claims 1 to 2, 4, and 7, characterized in that, The mass ratio of the first particle, the second particle, the third particle, the fourth particle, and the fifth particle is 1:(0.8~1.2):(1.5~2.5):(6~10):(6~10).

9. The lithium-ion secondary battery according to any one of claims 1 to 2, 4, and 7, characterized in that, The positive electrode active material satisfies one or more of the following characteristics: (1) The average particle size of the second particle is 5 μm to 10 μm; (2) The average particle size of the third particle is 3μm~5μm; (3) The average particle size of the fourth particle is 2μm~3μm; (4) The average particle size of the fifth particle is 1 μm to 2 μm.

10. The lithium-ion secondary battery according to any one of claims 1 to 2, 4, and 7, characterized in that, The positive electrode active material satisfies one or more of the following characteristics: (1) The first particle comprises polycrystalline particles; (2) The second particle includes polycrystalline particles; (3) The third particle includes one or more of single-crystal particles and polycrystalline particles; (4) The fourth particle includes one or more of single-crystal particles and polycrystalline particles; (5) The fifth particle includes one or more of single crystal particles and polycrystalline particles.

11. The lithium-ion secondary battery according to claim 10, characterized in that, The layered lithium-containing transition metal oxide accounts for 90% to 100% of the mass of the positive electrode active material; the olivine-structured lithium phosphate accounts for less than or equal to 10% of the mass of the positive electrode active material.

12. The lithium-ion secondary battery according to any one of claims 1 to 2, 4, 7, and 11, characterized in that, The compaction density of the positive electrode sheet is 3.5 g / cm³. 3 ~4.0g / cm 3 .

13. An electrical appliance, characterized in that, The lithium-ion secondary battery includes any one of claims 1 to 12.

Images