Positive electrode active material composition, positive electrode plate, battery and electric equipment

Abstract

The invention provides a lithium ion secondary battery, a positive electrode active material and electric equipment, the positive electrode active material of the lithium ion secondary battery comprises secondary particles, the secondary particles comprise a first type of secondary particles, a second type of secondary particles and a third type of secondary particles, the particle size of the first type of secondary particles is greater than 11 [mu] m and less than or equal to 15 [mu] m, and the particle size of the third type of secondary particles is greater than 11 [mu] m and less than or equal to 15 [mu] m. The particle size of the second type of secondary particles is greater than 7.5 mu m and less than or equal to 11 mu m, and the particle size of the third type of secondary particles is greater than 3 mu m and less than or equal to 7.5 mu m. Based on the total area of the secondary particles in a scanning electron microscope image with the magnification times of 2000, the total area ratio of the first type of secondary particles is greater than or equal to 5% and less than or equal to 26%; the total area ratio of the second type of secondary particles is greater than or equal to 64% and less than or equal to 80%; and the total area ratio of the third type of secondary particles is greater than or equal to 2% and less than or equal to 15%. By utilizing the secondary particles with the ratio, the compaction density of the positive pole piece is improved, and the volume energy density of the lithium ion secondary battery is improved.

Description

[0001] This application is a divisional application of the Chinese Patent Application No. 202411730338.2, titled "Cathode Active Material Composition, Cathode Electrode Sheet, Battery and Electric Equipment", filed on November 28, 2024. TECHNICAL FIELD

[0002] The present application relates to the technical field of lithium batteries, in particular to a cathode active material composition, a cathode electrode sheet, a battery and an electric equipment. BACKGROUND

[0003] In recent years, lithium ion batteries have made great progress. Lithium ion batteries can be widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric vehicles, electric tools, military equipment and aerospace. Among them, when lithium ion batteries are applied to the field of electric vehicles such as electric bicycles, electric motorcycles and electric vehicles, as the market requires higher endurance for electric vehicles, how to improve the volumetric energy density of the battery needs to be further solved. The above statements are only used to provide background technical information related to the present application, and do not necessarily constitute the prior art. SUMMARY

[0004] Therefore, the present application provides a cathode active material composition, a cathode electrode sheet, a battery and an electric equipment, which can improve the compaction density of the cathode active material composition and improve the volumetric energy density of the lithium ion secondary battery.

[0005] A first aspect of the present application provides a lithium ion secondary battery, comprising a cathode electrode sheet, an anode electrode sheet and an electrolyte, the cathode electrode sheet comprising a cathode active material, the cathode active material comprising lithium nickel cobalt manganese oxide, the molar content of nickel element in all transition metal elements being greater than or equal to 0.85; the cathode active material comprising secondary particles, the secondary particles comprising primary particles, the average particle size of the primary particles being 50 nm-2 μm; the secondary particles comprising first type secondary particles, second type secondary particles and third type secondary particles. The particle size of the first type secondary particles is greater than 11 μm and less than or equal to 15 μm; based on the total area of the secondary particles in a scanning electron microscope image with a magnification of 2000, the total area proportion of the first type secondary particles is greater than or equal to 5% and less than or equal to 26%; the particle size of the second type secondary particles is greater than 7.5 μm and less than or equal to 11 μm; based on the total area of the secondary particles in a scanning electron microscope image with a magnification of 2000, the total area proportion of the second type secondary particles is greater than or equal to 64% and less than or equal to 80%; the particle size of the third type secondary particles is greater than 3 μm and less than or equal to 7.5 μm, and based on the total area of the secondary particles in a scanning electron microscope image with a magnification of 2000, the total area proportion of the third type secondary particles is greater than or equal to 2% and less than or equal to 15%.

[0006] In the technical solution of the embodiment of the application, the molar content of nickel in all transition metal elements is greater than or equal to 0.85, and the specific capacity of the positive electrode active material is relatively high, so that the energy density of the lithium ion secondary battery is relatively high. The secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm. The positive electrode active material provided by the application is a polycrystalline material, which is composed of a plurality of crystal grains with different orientations, i.e., primary particles, and the crystal grains are connected to each other through grain boundaries. Further, the secondary particles include first-type secondary particles, second-type secondary particles and third-type secondary particles, and the particle size and quantity distribution and the total area ratio distribution of the secondary particles are within the above range, which can improve the compaction density of the positive electrode sheet, and the total area ratio distribution of the secondary particles makes the secondary particles not easy to be broken during the increase of the cold-pressing pressure in the manufacturing process of the positive electrode sheet, so that the lithium ion secondary battery has a relatively high volumetric energy density, thereby improving the electrochemical performance of the lithium ion secondary battery.

[0007] In some embodiments, based on the total area of the secondary particles in a scanning electron microscope image with a magnification of 2000, the total area ratio of the first-type secondary particles is greater than or equal to 17% and less than or equal to 26%, the total area ratio of the second-type secondary particles is greater than or equal to 68% and less than or equal to 80%, and the total area ratio of the third-type secondary particles is greater than or equal to 2% and less than or equal to 15%.

[0008] In the technical solution of the embodiment of the application, based on the total area of the secondary particles in a scanning electron microscope image with a magnification of 2000, the total area ratio of the first-type secondary particles, the total area ratio of the second-type secondary particles and the total area ratio of the third-type secondary particles are within the above range, which can improve the compaction density of the positive electrode sheet, and the area ratio distribution of the secondary particles makes the secondary particles not easy to be broken during the increase of the cold-pressing pressure in the manufacturing process of the positive electrode sheet, so that the lithium ion secondary battery has a relatively high volumetric energy density, thereby improving the electrochemical performance of the lithium ion secondary battery.

[0009] In some embodiments, one or two or three of the first-type secondary particles, the second-type secondary particles and the third-type secondary particles are circular secondary particles, and the circular secondary particles are secondary particles with a ratio of the longest diameter to the shortest diameter greater than or equal to 1 and less than or equal to 1.4 in a scanning electron microscope image.

[0010] In the technical scheme of the embodiment of the present application, one or two or three of the first type of secondary particles, the second type of secondary particles and the third type of secondary particles are circular secondary particles, and the ratio of the longest diameter to the shortest diameter is in the above range, so that the internal arrangement order of the secondary particles is higher, the friction between the secondary particles is reduced, and under the same pressure, the compaction density is larger; in the process of cyclic charging and discharging, the stress accumulation degree in the circular secondary particles is lower, and the generated stress is easier to release, which is beneficial to reducing the probability of secondary particle breakage, improving the compaction density of the positive electrode plate, and improving the volume energy density of the lithium ion secondary battery; improving the situation of reduced battery cycle performance caused by particle breakage, improving the cycle stability of the lithium ion secondary battery, and improving the electrochemical performance of the lithium ion secondary battery.

[0011] In some embodiments, in a scanning electron microscope image with a magnification of 2000, the ratio of the total area of the second type of secondary particles to the total area of the first type of secondary particles is 2.69-4.44.

[0012] In the technical scheme of the embodiment of the present application, the ratio of the total area of the second type of secondary particles to the total area of the first type of secondary particles is in the above range, which can improve the compaction density of the positive electrode plate, and the area ratio distribution of this type of secondary particles makes the secondary particles not easy to break during the increase of the cold-pressing pressure in the process of making the positive electrode plate, so that the lithium ion secondary battery has a higher volume energy density, thereby improving the electrochemical performance of the lithium ion secondary battery.

[0013] In some embodiments, the compaction density of the positive electrode active material under a pressure of 5T is 3.36 g / cm3-3.6 g / cm3.

[0014] In the technical scheme of the embodiment of the present application, the compaction density of the positive electrode active material is in the above range, and the lithium ion secondary battery has a high volume energy density, thereby improving the electrochemical performance of the lithium ion secondary battery.

[0015] In some embodiments, the specific surface area of the positive electrode active material is 0.35 m2 / g-0.7 m2 / g.

[0016] In the technical scheme of the embodiment of the present application, the specific surface area of the positive electrode active material is in the above range, so that the compaction density of the positive electrode active material is better, and the volume energy density of the lithium ion secondary battery is better.

[0017] In some embodiments, the compaction density of the positive electrode plate with a grammage of 1.4 x 10 -4 g / mm 2 -2.3 x 10 -4 g / mm 2 under 0.7% elongation is 3.35 g / cm3-3.7 g / cm3.

[0018] In the technical solution of this application embodiment, the compaction density of the positive electrode sheet is within the above range, and the lithium-ion secondary battery has a high volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0019] In some implementations, the average particle size of the primary particles is 100 nm to 500 nm.

[0020] In the technical solution of this application embodiment, the average particle size of the primary particles is within the above-mentioned range, which makes the primary particles have a shorter electron transport path, which helps to improve electron transport efficiency, thereby improving the charge and discharge performance of the battery and making the electrochemical performance of the lithium-ion secondary battery better.

[0021] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, wherein the molar content of nickel in all transition metal elements is greater than or equal to 0.9.

[0022] In the technical solution of this application embodiment, the molar content of nickel in all transition metal elements is greater than or equal to 0.9, the specific capacity of the positive electrode active material is high, and the volumetric energy density of the lithium-ion secondary battery is high.

[0023] In some embodiments, the positive electrode active material includes materials with the structural formula Li. a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

[0024] In the technical solution of this application embodiment, the positive electrode active material combines the advantages of nickel, cobalt and manganese. At the same time, the doping element M1 helps to improve the bulk stability and electrical stability of the positive electrode active material, reduce the cation mixing problem caused by high nickel, and promote the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0025] The second aspect of this application provides a positive electrode active material, comprising lithium nickel cobalt manganese oxide, wherein the molar content of nickel in all transition metal elements is greater than or equal to 0.85; the positive electrode active material comprises secondary particles, which include primary particles, the average particle size of which is 50 nm to 2 μm; the secondary particles include: a first type of secondary particles, the particle size of which is greater than 11 μm and less than or equal to 15 μm; based on the total area of ​​the secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​the first type of secondary particles accounts for greater than or equal to 5% and less than [a certain percentage]. Or equal to 26%; Secondary particles, the particle size of secondary particles is greater than 7.5 μm and less than or equal to 11 μm; Based on the total area of ​​secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​secondary particles of secondary particles accounts for greater than or equal to 64% and less than or equal to 80%; Third secondary particles, the particle size of secondary particles is greater than 3 μm and less than or equal to 7.5 μm; Based on the total area of ​​secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​secondary particles of secondary particles accounts for greater than or equal to 2% and less than or equal to 15%.

[0026] In the technical solution of this application embodiment, the molar content of nickel in all transition metal elements is greater than or equal to 0.85, resulting in a high specific capacity of the positive electrode active material and thus a high energy density of the lithium-ion secondary battery. The secondary particles include primary particles, with an average particle size of 50 nm to 2 μm. The positive electrode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, which are interconnected through grain boundaries. Further, the secondary particles include first-type, second-type, and third-type secondary particles. The particle size and quantity distribution, as well as the total area ratio of the secondary particles, fall within the aforementioned range, which can improve the compaction density of the positive electrode sheet. Furthermore, this distribution of the total area ratio of secondary particles makes them less prone to breakage due to increased cold pressing pressure during the positive electrode sheet manufacturing process, thereby enabling the lithium-ion secondary battery to possess a high volumetric energy density and thus improving its electrochemical performance.

[0027] In some embodiments, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are circular secondary particles. A circular secondary particle is defined as a secondary particle whose longest diameter to shortest diameter ratio is greater than or equal to 1 and less than or equal to 1.4 in a scanning electron microscope image.

[0028] In the technical solution of this application embodiment, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are spherical secondary particles. The ratio of their longest diameter to their shortest diameter is within the aforementioned range, resulting in a higher degree of internal ordering of the secondary particles, reduced friction between the secondary particles, and greater compaction density under the same pressure. During cyclic charging and discharging, the stress accumulation inside the spherical secondary particles is lower, and the generated stress is more easily released, which helps to reduce the probability of secondary particle breakage, increase the compaction density of the positive electrode sheet, increase the volumetric energy density of the lithium-ion secondary battery, and thus improve the electrochemical performance of the lithium-ion secondary battery.

[0029] In some embodiments, the positive electrode active material includes materials with the structural formula Li. a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

[0030] In the technical solution of this application embodiment, the positive electrode active material combines the advantages of nickel, cobalt and manganese. At the same time, the doping element M1 helps to improve the bulk stability and electrical stability of the positive electrode active material, reduce the cation mixing problem caused by high nickel, and promote the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0031] A third aspect of this application provides an electrical device comprising the lithium-ion secondary battery provided in the first aspect of this application and / or the positive electrode active material provided in the second aspect of this application. Since the electrical device of this application includes the lithium-ion secondary battery provided in the first aspect of this application, it has at least the same advantages as the lithium-ion secondary battery provided in the first aspect.

[0032] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of secondary particles according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application.

[0034] Figure 3 This is an exploded structural diagram of a battery according to one embodiment of this application.

[0035] Figure 4a This is a partial structural schematic diagram of an electrical device according to one embodiment of this application.

[0036] Figure 4b This is a schematic diagram of an electrical device according to one embodiment of this application. Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0038] The "range" disclosed in this application is defined by 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 and can be arbitrarily combined; 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 listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0042] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0043] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0044] As a positive electrode active material, lithium nickel cobalt manganese oxide has a low compaction density, resulting in a low volumetric energy density and consequently a low energy density in lithium-ion secondary batteries.

[0045] Based on this, the first aspect of this application provides a lithium-ion secondary battery, including a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, which includes lithium nickel cobalt manganese oxide, wherein the molar content of nickel in all transition metal elements is greater than or equal to 0.85. The positive active material includes secondary particles, as described above. Figure 1Secondary particles include primary particles, with an average particle size of 50 nm to 2 μm. Secondary particles are further categorized into three types: Type I, Type II, and Type III. Type I secondary particles have a particle size greater than 11 μm and less than or equal to 15 μm. Based on the total area of ​​secondary particles in a 2000x scanning electron microscope image, Type I secondary particles account for 5% to 26% of the total area. Type II secondary particles have a particle size greater than 7.5 μm and less than or equal to 11 μm. Based on the total area of ​​secondary particles in a 2000x scanning electron microscope image, Type II secondary particles account for 64% to 80% of the total area. Type III secondary particles have a particle size greater than 3 μm and less than or equal to 7.5 μm. Based on the total area of ​​secondary particles in a 2000x scanning electron microscope image, Type III secondary particles account for 2% to 15% of the total area.

[0046] In the technical solution of this application embodiment, the molar content of nickel in all transition metal elements is greater than or equal to 0.85, resulting in a high specific capacity of the positive electrode active material and thus a high energy density of the lithium-ion secondary battery. The secondary particles include primary particles, with an average particle size of 50 nm to 2 μm. The positive electrode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, which are interconnected through grain boundaries. Further, the secondary particles include first-type, second-type, and third-type secondary particles. The particle size and quantity distribution, as well as the total area ratio of the secondary particles, fall within the aforementioned range, which can improve the compaction density of the positive electrode sheet. Furthermore, this distribution of the total area ratio of secondary particles makes them less prone to breakage due to increased cold pressing pressure during the positive electrode sheet manufacturing process. This results in a higher volumetric energy density for the lithium-ion secondary battery, improving its energy density and electrochemical performance.

[0047] The average particle size of the primary particles can be 50nm, 85nm, 100nm, 180nm, 220nm, 300nm, 500nm, 1μm, 1.5μm, 1.7μm, 2μm, etc., or a range consisting of any two of the above values, such as 50nm~1μm, 1μm~1.5μm, 1.5μm~2μm, 100nm~500nm, 300nm~1.7μm, etc.

[0048] The particle size of the first type of secondary particles can be 11.1μm, 11.5μm, 12μm, 12.5μm, 13μm, 14μm, 14.5μm, 15μm, etc., or a range consisting of any two of the above values, such as 11.1μm~13μm, 13μm~15μm, 8.5μm~10μm, 7.85μm~9μm, 9μm~10.5μm, etc.

[0049] Based on the total area of ​​secondary particles in a scanning electron microscope image with a magnification of 2000, the percentage of the total area of ​​the first type of secondary particles can be 5%, 5.5%, 8%, 10%, 13%, 15%, 18%, 21%, 25%, 26%, etc., or a range consisting of any two of the above values, such as 5%~13%, 13%~26%, 5.5%~15%, 8%~21%, etc.

[0050] The particle size of the second type of secondary particles can be 7.55μm, 7.85μm, 8.5μm, 9μm, 9.8μm, 10μm, 10.5μm, 11μm, etc., or a range consisting of any two of the above values, such as 7.55μm~9.8μm, 9.8μm~11μm, 8.5μm~10μm, 7.85μm~9μm, 9μm~10.5μm, etc.

[0051] Based on the total area of ​​secondary particles in a scanning electron microscope image with a magnification of 2000, the percentage of the total area of ​​the second type of secondary particles can be 64%, 65%, 70%, 72%, 75%, 76%, 77%, 78%, 79%, 80%, etc., or a range consisting of any two of the above values, such as 64%~76%, 76%~80%, 65%~78%, 70%~79%, etc.

[0052] The particle size of the third type of secondary particles can be 3.1μm, 3.5μm, 3.7μm, 4μm, 4.5μm, 5.5μm, 6μm, 6.7μm, 7.5μm, or any range of two of the above values, such as 3.1μm~3.7μm, 3.7μm~7.5μm, 3.5μm~5.5μm, 4.5μm~6.7μm, 5.5μm~7.5μm, etc.

[0053] Based on the total area of ​​secondary particles in a scanning electron microscope image with a magnification of 2000, the percentage of the total area of ​​the third type of secondary particles can be 2%, 2.5%, 5%, 6%, 8%, 10%, 12%, 13%, 14%, 15%, etc., or a range consisting of any two of the above values, such as 2%~8%, 8%~15%, 6%~14%, 10%~13%, etc.

[0054] In this embodiment of the application, the sum of the total area ratio of the first type of secondary particles, the total area ratio of the second type of secondary particles, and the total area ratio of the third type of secondary particles is 1.

[0055] The average particle size of primary particles is common knowledge in the field and has a common meaning in the field. It can be measured by methods and instruments in the field.

[0056] In this embodiment, the secondary particles include first-type secondary particles, second-type secondary particles, and third-type secondary particles. The secondary particles of the positive electrode active material are prepared by the same preparation method, that is, the positive electrode active material prepared by the same preparation method under the same preparation conditions, which simultaneously includes first-type secondary particles, second-type secondary particles, and third-type secondary particles.

[0057] In some implementations, based on the total area of ​​secondary particles in a scanning electron microscope image with a magnification of 2000, the total area of ​​the first type of secondary particles accounts for more than or equal to 17% and less than or equal to 26%; the total area of ​​the second type of secondary particles accounts for more than or equal to 68% and less than or equal to 80%; and the total area of ​​the third type of secondary particles accounts for more than or equal to 2% and less than or equal to 15%.

[0058] In the technical solution of this application embodiment, based on the total area of ​​secondary particles in a scanning electron microscope image with a magnification of 2000, the proportion of the total area of ​​the first type of secondary particles, the proportion of the total area of ​​the second type of secondary particles, and the proportion of the total area of ​​the third type of secondary particles are within the above range, which can improve the compaction density of the positive electrode sheet. Furthermore, this distribution of the area proportion of secondary particles makes it less likely for the secondary particles to break as the cold pressing pressure increases during the manufacturing process of the positive electrode sheet, thereby enabling the lithium-ion secondary battery to have a higher volumetric energy density and thus improving the electrochemical performance of the lithium-ion secondary battery.

[0059] Based on the total area of ​​secondary particles in a scanning electron microscope image at 2000 magnification, the percentage of the total area of ​​the first type of secondary particles can be 17%, 18%, 19%, 20%, 21%, 22%, 23%, 25%, 26%, or any range of two of the above values, such as 17%~23%, 23%~26%, 19%~22%, 18%~25%, etc.; the percentage of the total area of ​​the second type of secondary particles can be 68%, 69%, 70%, 73%, 75%, 78%. The percentage of total area of ​​the third type of secondary particles can be 2%, 3.5%, 4%, 5.5%, 6.5%, 8%, 12%, 14.2%, 15%, etc., or any two of the above values, such as 68%~75%, 75%~80%, 68%~73%, 78%~69%, etc.;

[0060] In some embodiments, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are circular secondary particles. A circular secondary particle is defined as a secondary particle whose longest diameter to shortest diameter ratio is greater than or equal to 1 and less than or equal to 1.4 in a scanning electron microscope image.

[0061] In the technical solution of this application embodiment, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are spherical secondary particles, and the ratio of their longest diameter to their shortest diameter is within the above-mentioned range. This results in a higher degree of internal ordering of the secondary particles, reduced friction between the secondary particles, and a higher compaction density under the same pressure. During cyclic charging and discharging, the stress accumulation inside the spherical secondary particles is lower, and the generated stress is more easily released, which helps to reduce the probability of secondary particle breakage, increase the compaction density of the positive electrode sheet, and increase the volumetric energy density of the lithium-ion secondary battery. It also mitigates the reduction in battery cycle performance caused by particle breakage, improves the cycle stability of the lithium-ion secondary battery layer, and enhances the electrochemical performance of the lithium-ion secondary battery.

[0062] The ratio of the longest diameter to the shortest diameter of the secondary particle can be 1, 1.05, 1.1, 1.12, 1.15, 1.18, 1.2, 1.35, 1.4, or a range of any two of the above values, such as 1~1.1, 1.1~1.2, 1.12~1.18, 1.18~1.4, 1.05~1.2, etc.

[0063] In some implementations, in a scanning electron microscope image at a magnification of 2000, the ratio of the total area of ​​the second type of secondary particles to the total area of ​​the first type of secondary particles is 2.69 to 4.44.

[0064] In the technical solution of this application embodiment, the ratio of the total area of ​​the second type of secondary particles to the total area of ​​the first type of secondary particles is within the aforementioned range. This can improve the compaction density of the positive electrode sheet, and the area distribution of these secondary particles makes them less prone to breakage as the cold pressing pressure increases during the positive electrode sheet manufacturing process. This results in a higher volumetric energy density for the lithium-ion secondary battery, thereby improving its electrochemical performance. In a scanning electron microscope image with a magnification of 2000, the ratio of the total area of ​​the second type of secondary particles to the total area of ​​the first type of secondary particles can be 2.69, 2.87, 2.9, 3.0, 3.2, 3.5, 3.8, 3.9, 4.0, 4.2, 4.41, 4.44, etc., or a range consisting of any two of the aforementioned values, such as 2.69~3.2, 3.2~3.9, 3.9~4.44, 3.0~4.2, 3.5~4.0, etc.

[0065] In some embodiments, the compaction density of the positive electrode active material under 5T pressure is 3.36 g / cm³ to 3.6 g / cm³.

[0066] Among them, compaction density is common knowledge in the field, has a common meaning in the field, and can be measured by methods and instruments in the field.

[0067] In the technical solution of this application embodiment, the compaction density of the positive electrode active material is within the above-mentioned range, and the lithium-ion secondary battery has a high volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery. The compaction density of the positive electrode active material can be 3.36 g / cm³, 3.38 g / cm³, 3.40 g / cm³, 3.44 g / cm³, 3.48 g / cm³, 3.50 g / cm³, 3.51 g / cm³, 3.55 g / cm³, 3.57 g / cm³, 3.6 g / cm³, etc., or a range consisting of any two of the above values, such as 3.36 g / cm³~3.48 g / cm³, 3.48 g / cm³~3.51 g / cm³, 3.51 g / cm³~3.6 g / cm³, 3.48 g / cm³~3.55 g / cm³, 3.44 g / cm³~3.57 g / cm³, etc.

[0068] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.35 m² / g to 0.7 m² / g.

[0069] In the technical solution of this application embodiment, the specific surface area of ​​the positive electrode active material is within the above-mentioned range, resulting in better compaction density of the positive electrode active material and better volumetric energy density of the lithium-ion secondary battery. The specific surface area of ​​the positive electrode active material can be 0.35 m² / g, 0.42 m² / g, 0.45 m² / g, 0.51 m² / g, 0.55 m² / g, 0.61 m² / g, 0.63 m² / g, 0.65 m² / g, 0.68 m² / g, 0.7 m² / g, etc., or a range consisting of any two of the above values, such as 0.35 m² / g~0.51 m² / g, 0.51 m² / g~0.63 m² / g, 0.63 m² / g~0.7 m² / g, 0.42 m² / g~0.61 m² / g, 0.55 m² / g~0.68 m² / g, etc.

[0070] In some implementations, the basis weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The compaction density of the positive electrode sheet at 0.7% elongation is 3.35 g / cm³ to 3.7 g / cm³.

[0071] In the technical solution of this application embodiment, the compaction density of the positive electrode sheet is within the above range, and the lithium-ion secondary battery has a high volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery. The compaction density of the positive electrode sheet can be 3.35 g / cm³, 3.38 g / cm³, 3.39 g / cm³, 3.42 g / cm³, 3.47 g / cm³, 3.52 g / cm³, 3.53 g / cm³, 3.55 g / cm³, 3.57 g / cm³, 3.62 g / cm³, 3.7 g / cm³, etc., or a range consisting of any two of the above values, such as 3.35 g / cm³~3.47 g / cm³, 3.47 g / cm³~3.53 g / cm³, 3.53 g / cm³~3.62 g / cm³, 3.47 g / cm³~3.57 g / cm³, 3.52 g / cm³~3.57 g / cm³, etc.

[0072] In some implementations, the average particle size of the primary particles is 100 nm to 500 nm.

[0073] In the technical solution of this application embodiment, the average particle size of the primary particles is within the above-mentioned range, which makes the primary particles have a shorter electron transport path, which helps to improve electron transport efficiency, thereby improving the charge and discharge performance of the battery and making the electrochemical performance of the lithium-ion secondary battery better.

[0074] The average particle size of a single particle can be 100nm, 180nm, 230nm, 250nm, 285nm, 320nm, 375nm, 430nm, 486nm, 500nm, or any range of two of the above values, such as 100nm~285nm, 285nm~375nm, 375nm~500nm, 230nm~486nm, 320nm~430nm, etc.

[0075] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, wherein the molar content of nickel in all transition metal elements is greater than or equal to 0.9.

[0076] In the technical solution of this application embodiment, the molar content of nickel in all transition metal elements is greater than or equal to 0.9, the specific capacity of the positive electrode active material is high, and the volumetric energy density of the lithium-ion secondary battery is high.

[0077] In some embodiments, the positive electrode active material includes materials with the structural formula Li. a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

[0078] In the technical solution of this application embodiment, the positive electrode active material combines the advantages of nickel, cobalt and manganese. At the same time, the doping element M1 helps to improve the bulk stability and electrical stability of the positive electrode active material, reduce the cation mixing problem caused by high nickel, and promote the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0079] In the embodiments of this application, the substances providing the M1 source include, but are not limited to, sodium carbonate, sodium hydroxide, zirconium hydroxide, zirconium oxide, zirconium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, titanium oxide, titanium hydroxide, titanium carbonate, tungsten oxide, tungsten hydroxide, tungsten carbonate, niobium oxide, niobium hydroxide, niobium carbonate, tantalum hydroxide, tantalum carbonate, strontium hydroxide, strontium oxide, strontium carbonate, strontium phosphate, calcium hydroxide, calcium oxide, calcium carbonate, calcium phosphate, aluminum oxide, aluminum hydroxide, yttrium oxide, yttrium hydroxide, etc.

[0080] In some embodiments, the positive electrode active material further includes a coating layer comprising elements such as Al, B, and Co. The inclusion of Co in the coating layer can reduce residual alkali formed during the manufacturing process. The inclusion of B in the coating layer can refine the grain size, which is beneficial for the insertion and extraction of active particles. The inclusion of Al in the coating layer can improve the interfacial stability of the positive electrode active material.

[0081] The second aspect of this application provides a positive electrode active material, comprising lithium nickel cobalt manganese oxide, wherein the molar content of nickel in all transition metal elements is greater than or equal to 0.85; the positive electrode active material comprises secondary particles, which include primary particles, the average particle size of which is 50 nm to 2 μm; the secondary particles include: a first type of secondary particles, the particle size of which is greater than 11 μm and less than or equal to 15 μm; based on the total area of ​​the secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​the first type of secondary particles accounts for greater than or equal to 5% and less than [a certain percentage]. Or equal to 26%; Secondary particles, the particle size of secondary particles is greater than 7.5 μm and less than or equal to 11 μm; Based on the total area of ​​secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​secondary particles of secondary particles accounts for greater than or equal to 64% and less than or equal to 80%; Third secondary particles, the particle size of secondary particles is greater than 3 μm and less than or equal to 7.5 μm; Based on the total area of ​​secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​secondary particles of secondary particles accounts for greater than or equal to 2% and less than or equal to 15%.

[0082] In the technical solution of this application embodiment, the molar content of nickel in all transition metal elements is greater than or equal to 0.85, resulting in a high specific capacity of the positive electrode active material and thus a high energy density of the lithium-ion secondary battery. The secondary particles include primary particles, with an average particle size of 50 nm to 2 μm. The positive electrode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, which are interconnected through grain boundaries. Further, the secondary particles include first-type, second-type, and third-type secondary particles. The particle size and quantity distribution, as well as the total area ratio of the secondary particles, fall within the aforementioned range, which can improve the compaction density of the positive electrode sheet. Furthermore, this distribution of the total area ratio of secondary particles makes them less prone to breakage due to increased cold pressing pressure during the positive electrode sheet manufacturing process, thereby enabling the lithium-ion secondary battery to possess a high volumetric energy density and thus improving its electrochemical performance.

[0083] In some embodiments, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are circular secondary particles. A circular secondary particle is defined as a secondary particle whose longest diameter to shortest diameter ratio is greater than or equal to 1 and less than or equal to 1.4 in a scanning electron microscope image.

[0084] In the technical solution of this application embodiment, one, two, or three of the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles are spherical secondary particles. The ratio of their longest diameter to their shortest diameter is within the aforementioned range, resulting in a higher degree of internal ordering of the secondary particles, reduced friction between the secondary particles, and greater compaction density under the same pressure. During cyclic charging and discharging, the stress accumulation inside the spherical secondary particles is lower, and the generated stress is more easily released, which helps to reduce the probability of secondary particle breakage, increase the compaction density of the positive electrode sheet, increase the volumetric energy density of the lithium-ion secondary battery, and thus improve the electrochemical performance of the lithium-ion secondary battery.

[0085] In some embodiments, the positive electrode active material includes materials with the structural formula Li. a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

[0086] In the technical solution of this application embodiment, the positive electrode active material combines the advantages of nickel, cobalt and manganese. At the same time, the doping element M1 helps to improve the bulk stability and electrical stability of the positive electrode active material, reduce the cation mixing problem caused by high nickel, and promote the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0087] A third aspect of this application provides an electrical device comprising the lithium-ion secondary battery provided in the first aspect of this application and / or the positive electrode active material provided in the second aspect of this application. Since the electrical device of this application includes the lithium-ion secondary battery provided in the first aspect of this application, it has at least the same advantages as the lithium-ion secondary battery provided in the first aspect.

[0088] Electrical equipment can include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0089] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer includes the positive active material composition of the above embodiments of this application.

[0090] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0091] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0093] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0095] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes the negative electrode active material of the above embodiments.

[0096] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0097] 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 may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one 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).

[0099] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners like sodium carboxymethyl cellulose (CMC-Na).

[0101] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0102] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements.

[0103] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0104] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0105] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0106] 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.

[0107] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0108] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0109] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into a battery cell assembly using a winding or stacking process.

[0110] In some implementations, such as Figure 2 As shown, the battery cell 10 may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned cell assembly 11 and electrolyte. The outer packaging includes an end cap 12, a housing 13, and other functional components.

[0111] End cap 12 refers to a component that covers the opening of housing 13 to isolate the internal environment of battery cell 10 from the external environment. The shape of end cap 12 can be adapted to the shape of housing 13 to fit it. Optionally, end cap 12 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 12 is not easily deformed under pressure and impact, allowing battery cell 10 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 12a can be provided on end cap 12. Electrode terminals 12a can be used for electrical connection with cell assembly 11 to output or input electrical energy to battery cell 10. In some embodiments, end cap 12 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 10 reaches a threshold. The material of end cap 12 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this. In some embodiments, an insulating element (not shown) may be provided on the inner side of the end cap 12. The insulating element can be used to isolate the electrical connection components within the housing 13 from the end cap 12 to reduce the risk of short circuits. Exemplarily, the insulating element may be made of plastic, rubber, etc.

[0112] The housing 13 is a component used to cooperate with the end cap 12 to form the internal environment of the battery cell 10. This internal environment can accommodate the cell assembly 11, electrolyte, and other components. The housing 13 and the end cap 12 can be independent components. An opening can be provided on the housing 13, and the end cap 12 closes the opening to form the internal environment of the battery cell 10. Alternatively, the end cap 12 and the housing 13 can be integrated. Specifically, the end cap 12 and the housing 13 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 13, the end cap 12 closes the housing 13. The housing 13 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 13 can be determined according to the specific shape and size of the cell assembly 11. The material of the housing 13 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0113] The casing 13 may contain one or more battery cell assemblies 11. The portions of the positive and negative electrodes that do not contain active material each constitute tabs 11a. The positive and negative tabs may be located together at one end of the main body or at opposite ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 11a connect to the electrode terminals to form a current loop.

[0114] Please refer to Figure 3The battery 100 includes a housing 20 and a battery cell 10, with the battery cell 10 housed within the housing 20. The housing 20 provides a space for the battery cell 10 and can have various structures. In some embodiments, the housing 20 may include a first portion 21 and a second portion 22, which overlap each other, jointly defining a space for accommodating the battery cell 10. The second portion 22 may be a hollow structure with one open end, and the first portion 21 may be a plate-like structure, covering the open side of the second portion 22 so that the first portion 21 and the second portion 22 jointly define the space. Alternatively, both the first portion 21 and the second portion 22 may be hollow structures with one open side, with the open side of the first portion 21 covering the open side of the second portion 22. Of course, the housing 20 formed by the first portion 21 and the second portion 22 can have various shapes, such as a cylinder, a cuboid, etc.

[0115] In battery 100, there can be multiple battery cells 10, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 10 are connected in both series and parallel configurations. Multiple battery cells 10 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 10 is housed within the housing 20. Alternatively, battery 100 can also be composed of multiple battery cells 10 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the housing 20. Battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 10.

[0116] In this embodiment, the battery 100 includes a lithium-ion battery as the battery cell 10. In other embodiments, the battery 100 may further include any one or more of lithium-sulfur batteries, sodium-ion batteries, and magnesium-ion batteries, but is not limited thereto. The battery cell 10 may be cylindrical, flat, cuboid, or other shapes.

[0117] In some implementations, the batteries can be assembled into battery modules, and the number of batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0118] Electrical equipment includes at least one of the battery cells and / or batteries provided in this application. The battery cell or battery pack can be used as a power source for the electrical equipment or as an energy storage unit for the electrical equipment. Electrical equipment may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0119] As electrical equipment, individual battery cells and / or batteries can be selected according to their usage requirements.

[0120] Figure 4a and Figure 4b As shown, the electrical equipment is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A structural schematic diagram of the vehicle 1000 is provided. A battery 100 is installed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0121] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0122] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0123] Example 1 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction begins, water is added to the reactor, and the temperature is raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of Ni:Co:Mn of 0.93:0.06:0.01 is then added. Next, 0.4 mol / L sodium carbonate (as a complexing agent) and 0.4 mol / L ammonia (as a precipitant) are added. The pH in the reactor is controlled at 12, and the temperature at 71°C to carry out a co-precipitation reaction. After 8 hours of reaction, the first intermediate product is formed. Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.7. React for 18 hours to obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10.3, and the reaction was carried out for 65 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0124] 1.2) First sintering: The above-mentioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of WO3 and ZrO2 to achieve a Li:W:Zr molar ratio of 1:0.003:0.006. The mixed powder was then added to a sintering furnace for the first sintering, held at 720°C for 13 hours, and then cooled to room temperature at a rate of 5°C / min to obtain lithium transition metal oxide (Li(Ni)O2)). 0.93 Co 0.06 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2).

[0125] 1.3) Second sintering: The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoOOH to make the molar ratio of Li to Co 1:0.011 and then thoroughly mixed. The mixed powder was added to a sintering furnace for a second sintering at a temperature of 620℃ for 7.5h, and then cooled to room temperature at a rate of 5℃ / min.

[0126] 1.4) Add 300g of the powder obtained in step 1.3) to 300mL of deionized water and stir for 5min. Then filter to obtain solid powder and dry at 60℃.

[0127] 1.5) Third sintering: The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Al2O3 and H2BO3, so that the molar ratio of lithium, aluminum, and boron was 1:0.002:0.003. The mixed powder was then sintered for the third time at 350°C for 6 hours, and then cooled to room temperature at a rate of 1.5°C / min to obtain the positive electrode active material Li(Ni) of Example 1. 0.93 Co 0.06 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2.

[0128] 2) Preparation of the positive electrode sheet: The above-prepared positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were dissolved in solvent N-methylpyrrolidone (NMP) at a mass ratio of 98:0.5:1.5. After thorough stirring and mixing, a positive electrode slurry was obtained. The positive electrode slurry was then uniformly coated onto aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet.

[0129] 3) Preparation of negative electrode materials.

[0130] Artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are added to a deionized water solvent in a mass ratio of 90:5:2:2:1 and thoroughly mixed. The mixture is then coated onto both sides of a copper foil and subjected to drying, cold pressing, and other processes to obtain the negative electrode sheet.

[0131] 4) Preparation of electrolyte.

[0132] The electrolyte was a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC), with a volume ratio of EC, DEC, and DMC of 1:1:1. LiPF6 was then dissolved in the above organic solvent at a concentration of 1 mol / L.

[0133] 5) Separation membrane.

[0134] A 13μm thick polyethylene separator film was selected.

[0135] 6) Preparation of lithium-ion batteries.

[0136] The separator, negative electrode, and positive electrode are stacked in the order of "separator-negative electrode-separator-positive electrode", shaped, packaged in an aluminum-plastic bag, injected with electrolyte, sealed, and then formed to obtain a soft-pack battery.

[0137] Example 2 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction begins, water is added to the reactor, and the temperature is raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of Ni:Co:Mn of 0.85:0.14:0.01 is then added. Next, 0.4 mol / L sodium carbonate (as a complexing agent) and 0.3 mol / L ammonia (as a precipitant) are added. The pH in the reactor is controlled at 11.5, and the temperature at 75°C to carry out a co-precipitation reaction. After 4 hours of reaction, the first intermediate product is formed. Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.5. React for 17 hours to obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH in the reactor to 10.2, and the reaction was carried out for 80 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.85 Co 0.14 Mn 0.01 (OH)2).

[0138] 1.2) First sintering: The above-mentioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of WO3 and ZrO2 to achieve a Li:W:Zr molar ratio of 1:0.003:0.006. The mixed powder was then added to a sintering furnace for the first sintering, held at 700°C for 7 hours, and then cooled to room temperature at a rate of 5°C / min to obtain lithium transition metal oxide (Li(Ni)O2)). 0.85 Co 0.14 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2).

[0139] 1.3) Second sintering: The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoOOH to make the molar ratio of Li to Co 1:0.011. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 650℃ for 5 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0140] 1.4) Add 300g of the powder obtained in step 1.3) to 300mL of deionized water and stir for 5min. Then filter to obtain solid powder and dry at 60℃.

[0141] 1.5) Third sintering: The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Al2O3 and H2BO3, so that the molar ratio of lithium, aluminum, and boron was 1:0.002:0.003. The mixed powder was then sintered for the third time at 375°C for 5 hours, and then cooled to room temperature at a rate of 1.5°C / min to obtain the positive electrode active material Li(Ni) of Example 2. 0.85 Co 0.14 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2.

[0142] Example 3 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction began, water was added to the reactor, and the temperature was raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate, in a molar ratio of Ni:Co:Mn of 0.9:0.09:0.01, was then added. Subsequently, 0.4 mol / L sodium carbonate and 0.3 mol / L ammonia were added. The pH in the reactor was controlled at 12.2, and the temperature at 65°C to carry out a co-precipitation reaction. After 8 hours of reaction, the first intermediate product was formed. Continue adding complexing agent and ammonia water, control the pH in the reactor to gradually decrease, so that the pH in the reactor is 11, react for 17 hours, and obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10, and the reaction was carried out for 80 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 12 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.9 Co 0.09 Mn 0.01 (OH)2).

[0143] 1.2) First sintering: The above-mentioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of WO3 and ZrO2 to achieve a Li:W:Zr molar ratio of 1:0.003:0.006. The mixed powder was then added to a sintering furnace for the first sintering, held at 700℃ for 14 hours, and then cooled to room temperature at a rate of 5℃ / min to obtain lithium transition metal oxide (Li(Ni)O2)O2). 0.9 Co 0.09 Mn 0.01 )0.991 W 0.003 Zr 0.006 O2).

[0144] 1.3) Second sintering: The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoOOH to make the molar ratio of Li to Co 1:0.011. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 630℃ for 11 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0145] 1.4) Add 300g of the powder obtained in step 1.3) to 300mL of deionized water and stir for 5min. Then filter to obtain solid powder and dry at 60℃.

[0146] 1.5) Third sintering: The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Al2O3 and H2BO3, so that the molar ratio of lithium, aluminum and boron was 1:0.002:0.003. The mixed powder was sintered for the third time at 400°C for 12 hours and then cooled to room temperature at a rate of 1.5°C / min to obtain the positive electrode active material of Example 3.

[0147] Example 4 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction began, water was added to the reactor, and the temperature was raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate, in a molar ratio of Ni:Co:Mn of 0.95:0.04:0.01, was then added. Subsequently, 3.5 mol / L sodium carbonate and 0.3 mol / L ammonia were added. The pH in the reactor was controlled at 11.8, and the temperature at 71°C to carry out a co-precipitation reaction. After 8 hours of reaction, the first intermediate product was formed. Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.8. React for 16 hours to obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10.5, and the reaction was carried out for 65 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.95 Co 0.04 Mn 0.01 (OH)2).

[0148] 1.2) First sintering: The above-mentioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of WO3 and ZrO2 to achieve a Li:W:Zr molar ratio of 1:0.003:0.006. The mixed powder was then added to a sintering furnace for the first sintering, held at 715°C for 13 hours, and then cooled to room temperature at a rate of 5°C / min to obtain lithium transition metal oxide (Li(Ni)O2)). 0.95 Co 0.04 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2).

[0149] Example 5 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction began, water was added to the reactor, and the temperature was raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate, in a molar ratio of Ni:Co:Mn of 0.93:0.06:0.01, was then added. Subsequently, 1.6 mol / L sodium carbonate and 0.3 mol / L ammonia were added. The pH in the reactor was controlled at 11.8, and the temperature at 71°C to carry out a co-precipitation reaction. After 8 hours of reaction, the first intermediate product was formed. Continue adding complexing agent and ammonia water, control the pH in the reactor to gradually decrease, so that the pH in the reactor is 11, react for 18 hours, and obtain the second intermediate product; Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10.3, and the reaction was carried out for 70 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 9 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0150] Example 6 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.2) First sintering: The above-mentioned nickel-cobalt-manganese strong oxide precursor was mixed with Li₂CO₃ at a molar ratio of 1:1.05, followed by the addition of WO₃ and SrO to achieve a Li:W:Sr molar ratio of 1:0.003:0.006. The mixed powder was then added to a sintering furnace for the first sintering, held at 700°C for 11 hours, and then cooled to room temperature at a rate of 5°C / min to obtain lithium transition metal oxide (Li(Ni)O₂O₃)O₂O₃). 0.93 Co 0.06 Mn 0.01 ) 0.991 W 0.003 Sr 0.006 O2).

[0151] Example 7 Similar to Example 1, the difference is: 1.3) Second sintering: The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoSO4 to make the molar ratio of Li to Co 1:0.011. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 630℃ for 8 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0152] Example 8 Similar to Example 1, the difference is: 1.5) Third sintering: The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Y2O3 and H2BO3, so that the molar ratio of lithium, yttrium, and boron was 1:0.002:0.003. The mixed powder was then sintered for the third time at 320°C for 5 hours, and then cooled to room temperature at a rate of 1.5°C / min to obtain the positive electrode active material Li(Ni) of Example 8. 0.93 Co 0.06 Mn 0.01 ) 0.991 W 0.003 Zr 0.006 O2.

[0153] Comparative Example 1 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction begins, water is added to the reactor, and the temperature is raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of Ni:Co:Mn of 0.85:0.1:0.05 is then added. Next, 2 mol / L sodium carbonate and 0.25 mol / L ammonia are added. The pH in the reactor is controlled at 11, and the temperature at 62°C to carry out a co-precipitation reaction. After 10 hours of reaction, the first intermediate product is formed. Continue adding complexing agent and ammonia water, control the pH in the reactor to gradually decrease, so that the pH in the reactor is 10, react for 17 hours, and obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH of the reactor to 9.8, and the reaction was carried out for 85 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 12 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.85 Co 0.1 Mn 0.05 (OH)2).

[0154] Comparative Example 2 Similar to Example 1, the difference is: 1) Preparation of positive electrode active material: 1.1) Preparation of nickel-cobalt-manganese strong oxide precursors: Before the reaction began, water was added to the reactor, and the temperature was raised to 60°C. A mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of Ni:Co:Mn of 0.85:0.1:0.05 was then added. Next, 2 mol / L sodium carbonate and 0.6 mol / L ammonia were added. The pH in the reactor was controlled at 13.1, and the temperature at 68°C to carry out a co-precipitation reaction. After 7 hours of reaction, the first intermediate product was formed. Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 12. React for 19 hours to obtain the second intermediate product. Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10.8, and the reaction was carried out for 70 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the precursor particles to grow to the target Dv50 of about 7 μm. After the reaction was completed, the precursor was washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.85 Co 0.1 Mn 0.05 (OH)2).

[0155] Furthermore, the total area ratio of the first type of secondary particles, the ratio of the longest diameter to the shortest diameter of the first type of secondary particles, the total area ratio of the second type of secondary particles, the ratio of the longest diameter to the shortest diameter of the second type of secondary particles, the number ratio of the third type of secondary particles, the ratio of the longest diameter to the shortest diameter of the third type of secondary particles, the ratio of the total area of ​​the second type of secondary particles to the total area of ​​the first type of secondary particles, the average particle size of the primary particles, and the specific surface area of ​​the positive electrode active material in Examples 1-8 and Comparative Examples 1 and 2 are recorded in Tables 2.1 and 2.2.

[0156] The lithium-ion secondary batteries obtained in Examples 1-8 and Comparative Examples 1 and 2 were subjected to battery performance tests. The process and performance parameters of Examples 1-8 and Comparative Examples 1 and 2 are detailed in Tables 1.1, 1.2, 2.1 and 2.2.

[0157] Test method: 1. 0.1C specific capacity test Under constant temperature conditions of 25℃, the electrode was charged at 0.1C to 4.25V, then charged at 4.25V at a constant voltage until the current was ≤0.05mA. After standing for 5 minutes, it was discharged at 0.1C to 2.8V to obtain the capacity C1. The specific capacity is C1 / m, where m is the mass of the positive electrode active material.

[0158] 2. Cyclic performance test at 25℃ Under constant temperature conditions of 25℃, the battery was charged at 0.33C to 4.25V, then charged at 4.25V at a constant voltage until the current ≤0.05mA. After resting for 5 minutes, it was discharged at 0.33C to 2.8V, yielding the capacity D1. This process was repeated for 100 cycles, and the capacity D100 of the pouch battery was recorded. The capacity retention rate after 100 cycles = D100 / D1.

[0159] 3. Total area test of type I secondary particles, type II secondary particles, and type III secondary particles. Scanning electron microscopes were used to capture images at 2000x magnification. ImageJ software was used to calculate the area and corresponding particle size of the secondary particles. The sum of the areas of the first type of secondary particles was calculated, which is the total area of ​​the first type of secondary particles. The same method can be used to calculate the total area of ​​the second and third types of secondary particles.

[0160] 4. Powder compaction density test A certain amount of powder is placed in a compaction mold, which is then placed on a compaction density instrument. Different pressures are set, and the thickness of the powder (the thickness after depressurization) under different pressures can be read on the instrument. From this, the compaction density can be calculated. Instrument model: CARVER4350.

[0161] 5. Specific surface area test The sample to be tested is prepared into a uniform powder or granules, then placed in a vacuum at a specific processing temperature to remove adsorbed gases and moisture from the surface. The sample is placed in an adsorption instrument with liquid nitrogen at a temperature of 77.35 K. Adsorption isotherms are measured by gradually increasing the nitrogen pressure. Based on the adsorption isotherm data, the BET equation is used for fitting, yielding the slope and intercept of the adsorption isotherms. The specific surface area of ​​the sample is calculated using the parameters in the BET equation.

[0162] 6. Electrode compaction density test method After the positive electrode active material is prepared into an electrode sheet, the length L0 is measured, and the electrode sheet is placed on a roller press for rolling under different pressures. The length L1, coating thickness L2, and mass of coating material per unit area of ​​the electrode sheet M1 are measured after rolling. The compaction density under the corresponding pressure is P1=M1 / L2, and the elongation Q1=(L1-L0) / L0. Based on the test compaction density under different elongation rates, the electrode sheet compaction density corresponding to 0.7% elongation can be fitted.

[0163] 7. Average particle size test The positive electrode active material was tested using a ZEISS Sigma 300 scanning electron microscope, and then the morphology of the sample was observed in accordance with the standard JY / T010-1996.

[0164] Software Name: LIBMAS Lithium-ion Battery Material Microscopic Intelligent Analysis System. This system automatically identifies single-crystal particles from scanning electron microscope images of the cathode active material using AI. It can draw particle outlines, particle quantity, number, area, maximum caliper diameter, average value, and provides manual intervention options. The average particle size of a primary sample is calculated as the sum of the sizes of all measured particles divided by the sum of the number of primary samples.

[0165] 8. Volumetric energy density test Using the Blue Electric testing system, the battery cell was charged at 0.1C to 4.25V in a constant temperature environment of 25℃, then charged at a constant voltage of 4.25V until the current ≤0.05mA, allowed to stand for 5 minutes, and then discharged at 0.1C to 2.8V. The capacity of the battery cell was obtained as C1, and the corresponding voltage plateau was U1. The volume of the battery cell was measured as V1, and the volumetric energy density Vd was: Vd=(Cp×U1) / V1.

[0166] Table 1.1 Process parameters of lithium-ion secondary batteries in various embodiments and comparative examples

[0167] Table 1.2 Process parameters of lithium-ion secondary batteries in various embodiments and comparative examples

[0168] Table 2.1 Process and performance parameters of lithium-ion secondary batteries in various embodiments and comparative examples

[0169] Table 2.2 Process and performance parameters of lithium-ion secondary batteries in various embodiments and comparative examples

[0170] According to the test results in Tables 1.1, 1.2, 2.1, and 2.2, the secondary particles in the positive electrode active materials of Examples 1 to 8 include three different particle sizes. The compaction density, compaction density, specific capacity, cycle capacity retention rate, and volumetric energy density of the positive electrode active materials are all stronger than those of Comparative Examples 1 and 2. Therefore, the electrochemical performance of the lithium-ion secondary batteries of Examples 1 to 8 is stronger than that of Comparative Examples 1 and 2. This indicates that the particle size and quantity distribution and total area ratio distribution of the secondary particles provided by the embodiments of this application can improve the compaction density of the positive electrode. Furthermore, the particle size and quantity distribution and total area ratio distribution of these secondary particles make it less likely for the secondary particles to break as the cold pressing pressure increases during the manufacturing process of the positive electrode. This results in the lithium-ion secondary battery having a higher volumetric energy density and cycle performance, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0171] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-ion secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive active material, which includes lithium nickel cobalt manganese oxide. The positive active material includes secondary particles, which include primary particles. The secondary particles include circular secondary particles, wherein the ratio of the longest diameter to the shortest diameter of the circular secondary particles is greater than or equal to 1 and less than or equal to 1.

4.

2. The lithium-ion secondary battery according to claim 1, characterized in that, The secondary particles include a first type of secondary particles and a second type of secondary particles. The first type of secondary particles has a particle size greater than 11 μm and less than or equal to 15 μm. The second type of secondary particles has a particle size greater than 7.5 μm and less than or equal to 11 μm. In a scanning electron microscope image with a magnification of 2000, the ratio of the total area of ​​the second type of secondary particles to the total area of ​​the first type of secondary particles is 2.69 to 4.

44.

3. The lithium-ion secondary battery according to claim 2, characterized in that, The secondary particles also include a third type of secondary particles, the particle size of which is greater than 3 μm and less than or equal to 7.5 μm; based on the total area of ​​the secondary particles in a scanning electron microscope image at a magnification of 2000, the total area of ​​the third type of secondary particles accounts for more than or equal to 2% and less than or equal to 15%; Based on the total area of ​​the secondary particles in the scanning electron microscope image at a magnification of 2000, the total area of ​​the first type of secondary particles accounts for more than or equal to 5% and less than or equal to 26%. Based on the total area of ​​the secondary particles in the scanning electron microscope image at a magnification of 2000, the total area of ​​the second type of secondary particles accounts for more than or equal to 64% and less than or equal to 80%.

4. The lithium-ion secondary battery according to any one of claims 1 to 3, characterized in that, The molar content of nickel among all transition metals is greater than or equal to 0.

8.

5. The lithium-ion secondary battery according to claim 3, characterized in that, The total area of ​​the secondary particles is based on the scanning electron microscope image at 2000 magnification. The total area of ​​the first type of secondary particles accounts for more than or equal to 17% and less than or equal to 26%; The total area of ​​the second type of secondary particles is greater than or equal to 68% and less than or equal to 80%; The total area of ​​the third type of secondary particles is greater than or equal to 2% and less than or equal to 15%.

6. The lithium-ion secondary battery according to any one of claims 1 to 5, characterized in that, The compaction density of the positive electrode active material under 5T pressure is 3.36 g / cm³ to 3.6 g / cm³; and / or, The specific surface area of ​​the positive electrode active material is 0.35 m² / g to 0.7 m² / g; and / or, The weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The compaction density of the positive electrode sheet at 0.7% elongation is 3.35 g / cm³ to 3.7 g / cm³.

7. The lithium-ion secondary battery according to any one of claims 1 to 6, characterized in that, The average particle size of the primary particles is 50 nm to 2 μm.

8. The lithium-ion secondary battery according to any one of claims 1 to 7, characterized in that, The average particle size of the primary particles is 100nm~500nm.

9. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The positive electrode active material includes materials with the structural formula Li. a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

10. A positive electrode active material, characterized in that, The positive electrode active material includes lithium nickel cobalt manganese oxide; the positive electrode active material includes secondary particles, and the secondary particles include primary particles; The secondary particles include circular secondary particles, wherein the ratio of the longest diameter to the shortest diameter of the circular secondary particles is greater than or equal to 1 and less than or equal to 1.

4.

11. The positive electrode active material according to claim 10, characterized in that, Positive electrode active materials include those with the structural formula Li a Ni b Co c Mn d M1 (1-b-c-d) O n Materials; 0.5≤a≤1.2, 0.85≤b≤0.99, 0<c≤0.1, 0<d≤0.05, 1.9≤n≤2.2, M1 includes one or more combinations of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, and Ti.

12. An electrical appliance, characterized in that, Includes the lithium-ion secondary battery according to any one of claims 1 to 9 and / or the positive electrode active material according to claim 10 or 11.

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