Lithium-ion secondary battery, positive electrode active material, method for producing same, and electric device

Abstract

The application provides a lithium ion secondary battery, a positive electrode active material, a preparation method and an electric device. The lithium ion secondary battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte. The positive electrode sheet comprises a positive electrode active material. The positive electrode active material comprises secondary particles. The secondary particles comprise first secondary particles, second secondary particles and third secondary particles. The volume particle size distribution of the first secondary particles is 3 mu m < d11 <= 7.5 mu m. The volume particle size distribution of the second secondary particles is 7.5 mu m < d12 <= 11 mu m. The volume particle size distribution of the third secondary particles is 11 mu m < d13 <= 15 mu m. Based on the total number of the secondary particles, the number ratio of the first secondary particles is 2% <= N1 < 10%, the number ratio of the second secondary particles is 70% <= N2 < 85%, and the number ratio of the third secondary particles is 5% <= N3 < 28%. By using the above-mentioned proportioning secondary particles, the compaction density of the positive electrode sheet is improved, and the volume energy density of the lithium ion secondary battery is improved.

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and particularly to lithium ion secondary batteries, positive active materials, preparation methods thereof, and electrical equipment. Background Art

[0002] In recent years, lithium ion batteries have achieved great development. Lithium ion batteries can be widely used in energy storage power systems such as hydraulic power plants, thermal power plants, wind power plants, and solar power plants, as well as in many fields such as electric vehicles, electric tools, military equipment, and aerospace. Among them, when lithium ion batteries are applied to electric vehicles such as electric bicycles, electric motorcycles, and electric cars, with the increasing market demand for the cruising range of 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 this application, and do not necessarily constitute prior art. Summary of the Invention

[0003] In view of this, this application provides a lithium ion secondary battery, a positive active material, a preparation method thereof, and electrical equipment to solve the technical problem of low volumetric energy density of the battery caused by the low tap density of the positive electrode plate in the lithium ion secondary battery.

[0004] In the first aspect of this application, a lithium ion secondary battery is provided. The lithium ion secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive active material. The positive active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85. The positive active material includes secondary particles. The secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm. The secondary particles include the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles. The volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm. Based on the total number of secondary particles, the number proportion of the first type of secondary particles is N1, 2% ≤ N1 < 10%. The volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm. Based on the total number of secondary particles, the number proportion of the second type of secondary particles is N2, 70% ≤ N2 < 85%. The volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm. Based on the total number of secondary particles, the number proportion of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

[0005] In this 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 for 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 a first type, a second type, and a third type, with the particle size and quantity distribution within the aforementioned range. This can increase the compaction density of the positive electrode sheet, and the particle size and quantity distribution of these secondary particles makes them less prone to breakage as the compaction density of the positive electrode sheet increases. This results in a higher volumetric energy density for the lithium-ion secondary battery, thereby improving its electrochemical performance.

[0006] In one embodiment, one, two, or three of the first type of secondary particle, the second type of secondary particle, and the third type of secondary particle are circular secondary particles. The circular secondary particle is defined as having a ratio of the longest diameter to the shortest diameter of the secondary particle of d1 / d2 in a scanning electron microscope image, where 1 ≤ d1 / d2 ≤ 1.2.

[0007] In this embodiment, one, two, or three of the first, second, and third types of secondary particles are spherical secondary particles with a ratio of their longest to shortest diameter within the aforementioned range. This results in a higher degree of internal ordering of the secondary particles, reduced friction between them, and a higher compaction density under the same pressure. During cyclic charging and discharging, the spherical secondary particles have a lower degree of stress accumulation, making it easier to release the generated stress and reducing the probability of secondary particle breakage. This enables the lithium-ion secondary battery to have a higher volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0008] In one embodiment, the ratio of the number of the second type of secondary particles to the number of the first type of secondary particles is 7 to 42.5.

[0009] In this embodiment, the ratio of the number of the second type of secondary particles to the number of the first type of secondary particles is within the above range, which can increase the compaction density of the positive electrode sheet. Furthermore, the distribution of the number of these secondary particles makes it less likely for the secondary particles to break as the compaction density of the positive electrode sheet increases, thereby enabling the lithium-ion secondary battery to have a higher volumetric energy density and improving the electrochemical performance of the lithium-ion secondary battery.

[0010] In one embodiment, the average particle size of the primary particles is 100 nm to 500 nm.

[0011] In this 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.

[0012] In one embodiment, the compaction density of the positive electrode active material under a pressure of 5T is 3.35 g / cm³. 3 ~3.6g / cm 3 .

[0013] In this 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.

[0014] In one embodiment, the specific surface area of ​​the positive electrode active material is 0.35 m². 2 / g~0.75m 2 / g.

[0015] In this embodiment, the specific surface area of ​​the positive electrode active material is within the above-mentioned range, which results in a better compaction density of the positive electrode active material and a better volumetric energy density of the lithium-ion secondary battery.

[0016] In one embodiment, the basis weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The compacted density of the positive electrode sheet at 0.7% elongation is 3.35 g / cm³. 3 ~3.7g / cm 3 .

[0017] In this embodiment, the compaction density of the positive electrode sheet is within the above-mentioned range, resulting in a high volumetric energy density for the lithium-ion secondary battery, thereby improving its electrochemical performance. Specifically, the basis weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The preferred compaction density of the positive electrode sheet at 0.7% elongation is 3.4 g / cm³. 3 ~3.65g / cm 3 .

[0018] In one embodiment, the positive electrode active material includes a structure with the formula Li a Ni b Co c Mn d M1 (1-b-c-d) O nThe material; 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 a combination of more than one of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, Ti.

[0019] In this embodiment, the positive electrode active material combines the advantages of three elements of nickel, cobalt and manganese. At the same time, the doping element M1 helps to improve the bulk phase stability and electrical stability of the positive electrode active material, reduce the cation mixing problem caused by high nickel, and is also beneficial to promoting the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0020] The second aspect of the present application further provides a method for preparing a lithium-ion secondary battery, including: providing a slurry containing a positive electrode active material, coating the slurry containing the positive electrode active material on a positive electrode current collector to form a positive electrode plate, the positive electrode active material including lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements being greater than or equal to 0.85; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle diameter of the primary particles is 50 nm to 2 μm; the secondary particles include the first type of secondary particles, the second type of secondary particles and the third type of secondary particles, the volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the number proportion of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the number proportion of the second type of secondary particles is N2, 70% ≤ N2 < 85%; the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the number proportion of the third type of secondary particles is N3, 5% ≤ N3 < 28%; arranging a separator between the positive electrode plate and the negative electrode plate to form a lithium-ion secondary battery.

[0021] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85% of all transition metal elements, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of all transition metal elements, thereby improving the electrochemical performance of the lithium-ion secondary battery. The secondary particles include primary particles with an average particle size of 50 nm to 2 μm. The cathode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, interconnected by grain boundaries. The cathode active material includes secondary particles, including a first type, a second type, and a third type, which are prepared in a single step. The lithium-ion secondary battery prepared using the above method has a high compaction density of the cathode sheet, and the secondary particles in the cathode sheet are less prone to breakage as the compaction density of the cathode sheet increases, resulting in a high volumetric energy density and improved electrochemical performance of the lithium-ion secondary battery.

[0022] In one embodiment, the method for preparing the positive electrode active material includes: providing a solution containing a nickel source, a cobalt source, and a manganese source, wherein the molar ratio of the nickel source, cobalt source, and manganese source is x:y:(1-xy), and x≥0.85; adding a complexing agent with a concentration of 0.2mol / L to 3.5mol / L and a precipitant with a concentration of 0.3mol / L to 0.5mol / L to the solution containing the nickel source, cobalt source, and manganese source; controlling the pH range to 12.1 to 13 under an inert atmosphere; and maintaining the temperature at 50°C to... At 70℃, the reaction is carried out for 4 to 7 hours to form a first intermediate product. The pH of the first intermediate product is adjusted to 10.5 to 11, and the reaction is carried out for 13 to 17 hours to obtain a second intermediate product. The pH of the second intermediate product is adjusted to 10 to 10.4, and the reaction is carried out for 55 to 80 hours to obtain nickel cobalt manganese hydroxide with a volume average particle size (DV50) of 8.5 μm to 12 μm. The nickel cobalt manganese hydroxide is mixed with lithium salt and sintered to obtain lithium nickel cobalt manganese oxide cathode material.

[0023] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85 of all transition metal elements, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of all transition metal elements, thereby resulting in better electrochemical performance of the lithium-ion secondary battery. Furthermore, during the preparation of the nickel-cobalt-manganese hydroxide precursor, the precipitant reacts with the nickel, cobalt, and manganese sources to form a precipitate, and the complexing agent effectively complexes metal ions such as Ni, Co, and Mn in the liquid, helping to control the composition of the cathode active material precursor. By controlling the concentrations of the mixed salt solution, the precipitant, the complexing agent, the pH, the temperature, and the time within the aforementioned ranges, the nickel-cobalt-manganese hydroxide precursor exhibits the secondary particle size distribution provided in the first aspect of this application. Specifically, in the first intermediate product formation stage, the pH is controlled within the range of 12.1–13. Maintaining a higher pH can inhibit the growth of seed crystals in the overall particles and maintain the uniformity of the secondary particle size. The number of seed crystals is adjusted by controlling the nucleation time to 4–7 hours. In the second intermediate product formation stage, the pH of the reaction is lowered to 10.5–11, allowing the reaction to transition from nucleation to growth. Short-term pH reduction can decrease the formation of new crystal nuclei and improve the particle size uniformity of the secondary particles. The nickel-cobalt-manganese hydroxide formation stage is the growth period. Maintaining a low pH in the range of 10–10.4 can inhibit nucleation and reduce the probability of small particles. Stable reaction conditions can improve the crystallinity of the overall secondary particles. Furthermore, the volume average particle size (DV50) of the nickel-cobalt-manganese hydroxide precursor can be controlled within the range of 8.5 μm–12 μm, which helps to further control the volume average particle size (DV50) of the lithium nickel-cobalt-manganese oxide cathode material.

[0024] In one embodiment, nickel cobalt manganese hydroxide is mixed with lithium salt and sintered to obtain lithium nickel cobalt manganese oxide cathode material, comprising: mixing nickel cobalt manganese hydroxide with lithium salt and sintering for a first time to obtain a first product; mixing the first product with a first coating source and sintering for a second time to obtain a second product, wherein the temperature of the second sintering is lower than the temperature of the first sintering.

[0025] In this embodiment, nickel-cobalt-manganese hydroxide is mixed with lithium salt and subjected to a first high-temperature sintering to obtain a first product. The first product is then mixed with a first coating source and subjected to a second sintering to obtain a second product, which is a lithium nickel-cobalt-manganese oxide cathode material with the first coating source coated on its surface. The two sintering processes result in a better crystallinity of the material, thereby improving the electrochemical performance of the lithium nickel-cobalt-manganese oxide cathode material. The coating layer formed by the first coating source also reduces the possibility of side reactions between the lithium nickel-cobalt-manganese oxide cathode material and the electrolyte, further improving the electrochemical performance of the lithium-ion secondary battery.

[0026] In one embodiment, the temperature of the first sintering is 725°C to 780°C, and the time of the first sintering is 7h to 14h; or / and, the temperature of the second sintering is 400°C to 615°C, and the time of the second sintering is 5h to 11h.

[0027] In this embodiment, the temperature and time of the first sintering and the temperature and time of the second sintering are controlled within the above range to give the material a better crystallization state, thereby improving the electrochemical performance of the lithium nickel cobalt manganese oxide cathode material.

[0028] In one embodiment, a first product is obtained by mixing nickel cobalt manganese hydroxide with a lithium salt and performing a first sintering, comprising: mixing nickel cobalt manganese hydroxide, a lithium salt, and a dopant source, and performing a first sintering to obtain the first product, wherein the dopant source includes one or more of Mg source, Na source, Zr source, Y source, Al source, Ca source, W source, Nb source, Ta source, Sr source, or Ti source.

[0029] In this embodiment, incorporating one or more of the following sources—Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, or Ti—into the positive electrode active material can improve the material's crystal structure, reduce distortion of the layered structure, and thereby enhance the structural stability and cycle life of the lithium nickel cobalt manganese oxide positive electrode material.

[0030] In one embodiment, the first coating source includes one or more of Co, Al, F, and Ti sources.

[0031] In this embodiment, the first coating source is beneficial to improving the structural stability of the positive electrode active material, thereby improving its electrochemical performance. The Co source coating is primarily used to reduce residual alkali on the surface of the positive electrode active material. Residual alkali generates a large amount of gas under high voltage and also exacerbates side reactions between the positive electrode active material and the electrolyte. Therefore, reducing residual alkali improves the stability of the lithium-ion secondary battery. The coating layer formed by the Al source can delay electrolyte erosion and reduce by-product generation. The main function of the F source is to form a quasi-artificial solid electrolyte interphase (CEI) film on the surface of the positive electrode active material. The quasi-artificial CEI film formed by AlF3 can effectively reduce electrolyte erosion and improve interface stability. The coating layer formed by the Ti source can enhance the strength of the positive electrode active material.

[0032] In one embodiment, after mixing the first product with the first coating source and sintering it a second time to obtain the second product, the process includes: mixing the second product with the second coating source and sintering it a third time to obtain the third product, wherein the third product is a lithium nickel cobalt manganese oxide cathode material.

[0033] In one embodiment, the temperature of the third sintering is 250°C to 348°C, and the time of the third sintering is 5 h to 12 h; the second coating source includes one or more of the first of the B source, the Al source, and the Y source.

[0034] In this embodiment, after mixing the first product with the first coating source and performing the second sintering to obtain a lithium nickel cobalt manganese oxide cathode material coated with the first coating source on the surface, the lithium nickel cobalt manganese oxide cathode material is mixed with the second coating source and subjected to the third sintering. The second coating source is coated outside the first coating source to obtain a double-coated lithium nickel cobalt manganese oxide cathode material. The second coating source is beneficial to improving the interface stability of the cathode active material and improving the ability of lithium ions to intercalate and deintercalate. Among them, the B source can refine the primary grains and improve the ability of lithium ions to deintercalate on the surface. The coating formed by the Y source is easy to form a protective layer on the surface, reduce the surface activity, and improve the interface stability; the AlF3 forms an artificial CEI film-like structure that can effectively help reduce the erosion of the electrolyte and improve the interface stability.

[0035] The third aspect of the present application further provides a cathode active material, including lithium nickel cobalt manganese oxide, wherein the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the cathode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; the secondary particles include: the first type of secondary particles, the volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the number ratio of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the second type of secondary particles, the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the number ratio of the first type of secondary particles is N2, 70% ≤ N2 < 85%; the third type of secondary particles, the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the number ratio of the third type of secondary particles is N3, 5% ≤ N3 < 28%. <000026​In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85 of all transition metal elements, ensuring that nickel in the lithium nickel-cobalt-manganese cathode active material accounts for at least 0.85 of all transition metal elements, thereby improving the electrochemical performance of the lithium-ion secondary battery. The secondary particles include primary particles with an average particle size of 50 nm to 2 μm. The cathode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, interconnected by grain boundaries. The cathode active material includes secondary particles, including a first type, a second type, and a third type, which are prepared in a single step. The lithium-ion secondary battery prepared using the above method has a high compaction density of the cathode sheet, and the secondary particles in the cathode sheet are less prone to breakage as the compaction density of the cathode sheet increases, resulting in a high volumetric energy density and improved electrochemical performance of the lithium-ion secondary battery.

[0037] In one embodiment, one, two, or three of the first type of secondary particle, the second type of secondary particle, and the third type of secondary particle are spherical secondary particles. The spherical secondary particle is defined as the ratio of the volumetric particle size distribution to the shortest diameter of the secondary particle in the scanning electron microscope image as d1 / d2, where 1≤d1 / d2≤1.2.

[0038] In this embodiment, one, two, or three of the first, second, and third types of secondary particles are spherical secondary particles with a ratio of their longest to shortest diameter within the aforementioned range. This results in a higher degree of internal ordering of the secondary particles, reduced friction between them, and a higher compaction density under the same pressure conditions. During cyclic charging and discharging, the spherical secondary particles have a lower degree of stress accumulation, making it easier to release the generated stress and reducing the probability of secondary particle breakage. This enables the lithium-ion secondary battery to have a high volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0039] In one embodiment, the positive electrode active material includes a structure with the 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.

[0040] In this 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 is also beneficial to promoting the growth of radial primary particles, thereby improving the electrochemical performance of the positive electrode active material.

[0041] The fourth aspect of the present application further provides a method for preparing a positive electrode active material, including: providing a solution containing a nickel source, a cobalt source, and a manganese source, wherein the molar ratio of the nickel source, the cobalt source, and the manganese source is x:y:(1 - x - y), x ≥ 0.85; adding a complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitating agent with a concentration of 0.3 mol / L to 0.5 mol / L into the solution containing the nickel source, the cobalt source, and the manganese source, under an inert atmosphere, controlling the pH range to be 12.1 to 13, and reacting at 50 to 70 °C for 4 h to 7 h to form a first intermediate product; adjusting the pH of the first intermediate product to 10.5 to 11 and reacting for 13 h to 17 h to obtain a second intermediate product; adjusting the pH of the second intermediate product to 10 to 10.4 and reacting for 55 h to 80 h to obtain nickel cobalt manganese hydroxide, and the volume average particle size DV50 of the nickel cobalt manganese hydroxide is 8.5 μm to 12 μm; mixing the nickel cobalt manganese hydroxide with a lithium salt and sintering to obtain a lithium nickel cobalt manganese oxide positive electrode material, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; the secondary particles include the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles, the volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the number proportion of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the number proportion of the second type of secondary particles is N2, 70% ≤ N2 < 85%; the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the number proportion of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

[0042] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85 of all transition metal elements, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of all transition metal elements, thereby resulting in better electrochemical performance of the lithium-ion secondary battery. Furthermore, during the preparation of the nickel-cobalt-manganese hydroxide precursor, the precipitant reacts with the nickel, cobalt, and manganese sources to form a precipitate, and the complexing agent effectively complexes metal ions such as Ni, Co, and Mn in the liquid, helping to control the composition of the cathode active material precursor. By controlling the concentrations of the mixed salt solution, the precipitant, the complexing agent, the pH, the temperature, and the time within the aforementioned ranges, the nickel-cobalt-manganese hydroxide precursor exhibits the secondary particle size distribution provided in the first aspect of this application. Specifically, in the first intermediate product formation stage, the pH range is controlled between 12.1 and 13. Maintaining a higher pH can inhibit the growth of seed crystals in the overall particles and maintain the uniformity of the secondary particle size. The number of seed crystals is adjusted by controlling the nucleation time to 4 to 7 hours. In the second intermediate product formation stage, the pH of the reaction is lowered to 10.5 to 11, so that the reaction transitions from nucleation to growth. Lowering the pH for a short time can reduce the formation of new crystal nuclei and improve the uniformity of the secondary particle size. The nickel-cobalt-manganese hydroxide formation stage is the growth period. Maintaining a low pH range of 10 to 10.4 can inhibit nucleation and reduce the probability of small particles. Stable reaction conditions can improve the crystallinity of the overall secondary particles.

[0043] In one embodiment, nickel cobalt manganese hydroxide is mixed with lithium salt and sintered to obtain a lithium nickel cobalt manganese oxide cathode material, comprising: mixing nickel cobalt manganese hydroxide with lithium salt and performing a first sintering to obtain a first product, wherein the first sintering temperature is 725°C to 780°C and the first sintering time is 7h to 14h; mixing the first product with a first coating source and performing a second sintering to obtain a second product, wherein the second sintering temperature is 400°C to 615°C and the second sintering time is 5h to 11h, wherein the first coating source includes one or more of Co source, Al source, F source, and Ti source; mixing the second product with a second coating source and performing a third sintering to obtain a third product, wherein the third product is a lithium nickel cobalt manganese oxide cathode material, wherein the third sintering temperature is 250°C to 348°C and the third sintering time is 5h to 12h; wherein the second coating source includes one or more of B source, Al source, and Y source.

[0044] In this embodiment, nickel-cobalt-manganese hydroxide is mixed with lithium salt and sintered at a high temperature for the first time to obtain a first product. The first product is then mixed with a first coating source and sintered a second time to obtain a second product, which is a lithium nickel-cobalt-manganese oxide cathode material coated with the first coating source. The two sintering processes result in a better crystallinity of the material, thereby improving the electrochemical performance of the lithium nickel-cobalt-manganese oxide cathode material. The coating layer formed by the first coating source also reduces the possibility of side reactions between the lithium nickel-cobalt-manganese oxide cathode material and the electrolyte, further improving the electrochemical performance of the lithium-ion secondary battery. By controlling the first sintering temperature and time, and the second sintering temperature and time within the aforementioned ranges, the material achieves a better crystallinity, thereby improving the electrochemical performance of the lithium nickel-cobalt-manganese oxide cathode material. The first product is mixed with the first coating source, and after a second sintering, a lithium nickel cobalt manganese oxide cathode material with the first coating source coated on its surface is obtained. Then, the lithium nickel cobalt manganese oxide cathode material is mixed with a second coating source, and after a third sintering, the second coating source coats the first coating source, resulting in a two-layer coated lithium nickel cobalt manganese oxide cathode material. The second coating source helps improve the interfacial stability of the cathode active material and enhances the lithium-ion insertion / extraction capability. The B source is converted into lithium boron oxide, which can act as a fast ion conductor, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0045] In one embodiment, nickel cobalt manganese hydroxide is mixed with lithium salt and sintered to obtain lithium nickel cobalt manganese oxide cathode material, comprising: mixing nickel cobalt manganese hydroxide, lithium salt and dopant source, and performing a first sintering to obtain a first product, wherein the dopant source includes one or more of Mg source, Na source, Zr source, Y source, Al source, Ca source, W source, Nb source, Ta source, Sr source or Ti source.

[0046] In this embodiment, incorporating one or more of the following sources—Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, or Ti—into the positive electrode active material can improve the material's crystal structure, reduce distortion of the layered structure, and thereby enhance the structural stability and cycle life of the lithium nickel cobalt manganese oxide positive electrode material.

[0047] The fifth aspect of this application provides an electrical device comprising a lithium-ion secondary battery according to any of the above-mentioned methods, and / or a lithium-ion secondary battery prepared by any of the above-mentioned methods, and / or a positive electrode active material according to any of the above-mentioned methods, and / or a positive electrode active material prepared by any of the above-mentioned methods. The electrical device according to the embodiments of this application possesses at least the same advantages as the lithium-ion secondary battery of the first aspect, and / or at least the same advantages as the lithium-ion secondary battery prepared by the method of the second aspect, and / or at least the same advantages as the positive electrode active material of the third aspect, and / or at least the same advantages as the positive electrode active material prepared by the method of the fourth aspect.

[0048] 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

[0049] Figure 1 This is a scanning electron microscope image of secondary particles according to an embodiment of this application;

[0050] Figure 2 This is a particle size distribution diagram of secondary particles according to an embodiment of this application;

[0051] Figure 3 This is a schematic flowchart of the preparation method of the positive electrode active material according to one embodiment of this application;

[0052] Figure 4 This is a schematic flowchart of a method for preparing a positive electrode active material according to another embodiment of this application;

[0053] Figure 5 This is a schematic diagram of a method for preparing a positive electrode active material according to another embodiment of this application;

[0054] Figure 6 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application.

[0055] Figure 7 This is an exploded structural diagram of a battery according to one embodiment of this application.

[0056] Figure 8a This is a partial structural schematic diagram of an electrical device according to one embodiment of this application.

[0057] Figure 8b This is a schematic diagram of an electrical device according to one embodiment of this application. Detailed Implementation

[0058] 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.

[0059] 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.

[0060] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0061] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0062] Unless otherwise specified, all steps of 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.

[0063] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application are open-ended and can also be closed-ended. For example, "comprising" and "including" can mean that other components not listed can also be included or comprised, or it can only include or comprise the listed components.

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

[0065] During the production process of the positive electrode sheet, in order to increase the compaction density of the positive electrode sheet, the compaction density can be increased by increasing the cold pressing pressure. However, as the cold pressing pressure increases, the secondary particles of the positive active material are prone to breakage, reducing the electrochemical performance of the lithium-ion secondary battery.

[0066] Based on this, in the first aspect of this application, a lithium-ion secondary battery is provided. The lithium-ion secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. The positive electrode sheet includes a positive active material. The positive active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the positive active material includes secondary particles. Refer to Figure 1 , the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; refer to Figure 2 , the secondary particles include the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles. The volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the proportion of the number of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the proportion of the number of the second type of secondary particles is N2, 70% ≤ N2 < 85%; the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the proportion of the number of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

[0067] In this 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 for 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 a first type, a second type, and a third type, with the particle size and quantity distribution within the aforementioned range. This can increase the compaction density of the positive electrode sheet, and the particle size and quantity distribution of these secondary particles makes them less prone to breakage as the compaction density of the positive electrode sheet increases. This results in a higher volumetric energy density for the lithium-ion secondary battery, thereby improving its electrochemical performance.

[0068] The average particle size of the primary particles can be 50nm, 85nm, 100nm, 180nm, 220nm, 300nm, 500nm, 1μm, 1.5μm, 1.7μm, 2μm, or any range of two of the above values, such as 50nm~1μm, 1μm~1.5μm, 1.5μm~2μm, 100nm~500nm, 300nm~1.7μm, etc.

[0069] The volumetric particle size distribution d11 of the first 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 any 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. Based on the total number of secondary particles, the percentage N1 of the first type of secondary particles can be 2%, 2.2%, 2.5%, 3.5%, 4%, 4.5%, 5%, 5.2%, 6.7%, 7%, 8%, 9.5%, 9.99%, or a range of any two of the above values, such as 2% to 5.2%, 5.2% to 9.99%, 4.5% to 7%, 3.5% to 9.5%, etc.

[0070] The volumetric particle size distribution d12 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. Based on the total number of secondary particles, the proportion N2 of the second type of secondary particles can be 70%, 72%, 75%, 78%, 80%, 81%, 82%, 83.5%, 84%, 84.9%, etc., or a range consisting of any two of the above values, such as 70%~78%, 78%~81%, 81%~84.9%, etc.

[0071] The volumetric particle size distribution d13 of the third type of secondary particles can be 11.1 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 14 μm, 14.5 μm, 15 μm, etc., or a range consisting of any two of the above values, such as 11.1 μm to 12.5 μm, 12.5 μm to 14 μm, 14 μm to 15 μm, etc. Based on the total number of secondary particles, the proportion N3 of the third type of secondary particles can be 5%, 8%, 8.5%, 10%, 15%, 17.5%, 20%, 23%, 25%, 27.9%, etc., or a range consisting of any two of the above values, such as 5% to 8.5%, 8.5% to 17.5%, 17.5% to 27.9%, etc.

[0072] 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.

[0073] Among them, volumetric particle size distribution is common knowledge in the field, has a common meaning in the field, and can be measured by methods and instruments in the field.

[0074] In one embodiment, one, two, or three of the first type of secondary particle, the second type of secondary particle, and the third type of secondary particle are circular secondary particles. The circular secondary particle is defined as having a ratio of the longest diameter to the shortest diameter of the secondary particle of d1 / d2 in a scanning electron microscope image, where 1 ≤ d1 / d2 ≤ 1.2.

[0075] In this embodiment, one, two, or three of the first, second, and third types of secondary particles are spherical secondary particles with a ratio of their longest to shortest diameter within the aforementioned range. This results in a higher degree of internal ordering of the secondary particles, reduced friction between them, and a higher compaction density under the same pressure conditions. During cyclic charging and discharging, the spherical secondary particles have a lower degree of stress accumulation, making it easier to release the generated stress and reducing the probability of secondary particle breakage. This enables the lithium-ion secondary battery to have a higher volumetric energy density and improves its electrochemical performance.

[0076] The ratio of the longest diameter to the shortest diameter of the secondary particle, d1 / d2, can be 1, 1.05, 1.1, 1.12, 1.15, 1.18, 1.2, or a range of any two of the above values, such as 1 to 1.1, 1.1 to 1.2, 1.12 to 1.18, etc.

[0077] In one embodiment, the ratio of the number of the second type of secondary particles to the number of the first type of secondary particles is 7 to 42.5.

[0078] In this embodiment, the ratio of the number of the second type of secondary particles to the number of the first type of secondary particles is within the above range, which can increase the compaction density of the positive electrode sheet. Furthermore, the distribution of the number of these secondary particles makes it less likely for the secondary particles to break as the compaction density of the positive electrode sheet increases, thereby enabling the lithium-ion secondary battery to have a higher volumetric energy density and improving the electrochemical performance of the lithium-ion secondary battery.

[0079] The ratio of the number of the second type of secondary particles to the number of the first type of secondary particles can be 7, 9, 10, 15, 18.5, 22, 26, 31, 35, 39, 42.5, or any range of any two of the above values, such as 7-15, 15-26, 26-35, 35-42.5, 10-31, 18.5-39, etc.

[0080] In one embodiment, the average particle size of the primary particles is 100 nm to 500 nm.

[0081] In this 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.

[0082] The average particle size of a primary particle can be 100nm, 155nm, 190nm, 220nm, 290nm, 350nm, 400nm, 420nm, 460nm, 485nm, 500nm, or any range of two of the above values, such as 100nm~290nm, 290nm~420nm, 420nm~500nm, 155nm~350nm, 190nm~400nm, 220nm~485nm, etc.

[0083] In one embodiment, the compaction density of the positive electrode active material under a pressure of 5T is 3.35 g / cm³. 3 ~3.6g / cm 3 .

[0084] 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.

[0085] In this 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.

[0086] The compaction density of the positive electrode active material can be 3.35 g / cm³. 3 3.38g / cm 3 3.40 g / cm 3 3.45g / cm 3 3.50g / cm 3 3.52g / cm 3 3.56g / cm 3 3.58g / cm 3 3.6g / cm 3 etc., or a range consisting of any two of the above values, such as 3.35 g / cm³. 3 ~3.45g / cm 3 3.45g / cm 3 ~3.52g / cm 3 3.52g / cm 3 ~3.6g / cm 3 3.40 g / cm 3 ~3.58g / cm 3 3.45g / cm 3 ~3.6g / cm 3 wait.

[0087] In one embodiment, the specific surface area of ​​the positive electrode active material is 0.35 m². 2 / g~0.75m 2 / g.

[0088] In this embodiment, the specific surface area of ​​the positive electrode active material is within the above-mentioned range, which results in a better compaction density of the positive electrode active material and a better volumetric energy density of the lithium-ion secondary battery.

[0089] Specific surface area 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.

[0090] The specific surface area of ​​the positive electrode active material can be 0.35 m². 2 / g, 0.38m 2 / g, 0.45m 2 / g, 0.52m 2 / g, 0.58m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.75m 2 / g, or a range consisting of any two of the above values, such as 0.35m. 2 / g~0.58m 2 / g, 0.58m 2 / g~0.65m 2 / g, 0.65m 2 / g~0.75m 2 / g, 0.52m 2 / g~0.7m 2 / g etc.

[0091] In one embodiment, the basis weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The compacted density of the positive electrode sheet at 0.7% elongation is 3.35 g / cm³. 3 ~3.7g / cm 3 .

[0092] In this embodiment, the compaction density of the positive electrode sheet is within the above-mentioned range, resulting in a high volumetric energy density for the lithium-ion secondary battery, thereby improving its electrochemical performance. Specifically, the basis weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The preferred compaction density of the positive electrode sheet at 0.7% elongation is 3.4 g / cm³. 3 ~3.65g / cm 3 .

[0093] The compaction density of the positive electrode sheet can be 3.35 g / cm³. 3 3.39 g / cm 3 3.4 g / cm³, 3.42 g / cm³ 3 3.46 g / cm 3 3.50g / cm 3 3.52g / cm 3 3.57g / cm 3 3.59g / cm 3 3.6g / cm 3 3.65 g / cm³, 3.66 g / cm³ 3 3.7g / cm 3 etc., or a range consisting of any two of the above values, such as 3.35 g / cm³. 3 ~3.46g / cm 3 3.46 g / cm 3 ~3.52g / cm 3 3.52g / cm 3 ~3.7g / cm 3 3.4g / cm 3 ~3.57g / cm 3 3.57g / cm 3 ~3.65g / cm 3 wait.

[0094] In one embodiment, the positive electrode active material includes a structure with the 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.

[0095] In this 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.

[0096] In the embodiments of the present 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.

[0097] In some embodiments, the positive electrode active material further includes a coating layer, and the coating layer includes elements such as Al, B, Co, Y, etc. The coating layer including Co element can reduce the residual alkali formed during the manufacturing process. The coating layer including B element can refine the grains, which is beneficial to the insertion and extraction of active particles. The coating layer including Al element or Y element can improve the interface stability of the positive electrode active material.

[0098] The second aspect of the present application also provides a preparation method of a lithium-ion secondary battery, including: providing a slurry containing a positive electrode active material, coating the slurry containing the positive electrode active material on a positive electrode current collector to form a positive electrode plate, where the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; the secondary particles include the first type of secondary particles, the second type of secondary particles, and the third type of secondary particles. The volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the number proportion of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the number proportion of the second type of secondary particles is N2, 70% ≤ N2 < 85%; the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the number proportion of the third type of secondary particles is N3, 5% ≤ N3 < 28%; arranging a separator between the positive electrode plate and the negative electrode plate to form a lithium-ion secondary battery.

[0099] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85% of all transition metal elements, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of all transition metal elements, thereby improving the electrochemical performance of the lithium-ion secondary battery. The secondary particles include primary particles with an average particle size of 50 nm to 2 μm. The cathode active material provided in this application is a polycrystalline material, composed of many grains with different orientations, i.e., primary particles, interconnected by grain boundaries. The cathode active material includes secondary particles, including a first type, a second type, and a third type, which are prepared in a single step. The lithium-ion secondary battery prepared using the above method has a high compaction density of the cathode sheet, and the secondary particles in the cathode sheet are less prone to breakage as the compaction density of the cathode sheet increases, resulting in a high volumetric energy density and improved electrochemical performance of the lithium-ion secondary battery.

[0100] In one embodiment, refer to Figure 3 The preparation methods of positive electrode active materials include:

[0101] S310: Provides a solution containing a nickel source, a cobalt source and a manganese source, wherein the molar ratio of the nickel source, the cobalt source and the manganese source is x:y:(1-xy), and x≥0.85.

[0102] In the embodiments of this application, the nickel source includes, but is not limited to, nickel carbonate, nickel hydroxide, nickel acetate, nickel sulfate, nickel chloride, nickel nitrate, and nickel oxalate. The cobalt source includes, but is not limited to, cobalt carbonate, cobalt hydroxide, cobalt acetate, cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt oxalate. The manganese source includes, but is not limited to, manganese dioxide, electrolytic manganese dioxide, and manganese tetroxide.

[0103] In the embodiments of this application, x can be 0.85, 0.88, 0.90, 0.92, 0.95, 0.96, 0.98, 0.99, 1, etc., or a range consisting of any two of the above values, such as 0.85~0.92, 0.92~0.96, 0.96~1, etc.

[0104] S320: A complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitant with a concentration of 0.3 mol / L to 0.5 mol / L are added to a solution containing nickel, cobalt, and manganese sources. Under an inert atmosphere, the pH is controlled within the range of 12.1 to 13, and the reaction is carried out at 50℃ to 70℃ for 4 to 7 hours to form the first intermediate product.

[0105] In this embodiment, the precipitant reacts with the nickel, cobalt, and manganese sources to form a precipitate. The complexing agent can effectively complex metal ions such as Ni, Co, and Mn in the liquid, which helps control the composition of the positive electrode active material precursor. The pH range is controlled between 12.1 and 13. Maintaining a higher pH can inhibit the growth of seed crystals in the overall particles and maintain the uniformity of the secondary particle size. The number of seed crystals can be adjusted by controlling the nucleation time to 4 to 7 hours. By controlling the concentration of the precipitant and complexing agent, as well as the pH range, reaction temperature, and reaction time, it is beneficial to control the reaction of the nickel, cobalt, and manganese sources to form nickel-cobalt-manganese hydroxide nuclei. The concentration of the complexing agent can be 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 1.8 mol / L, 2.1 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or any range of two of the above values, such as 0.2 mol / L to 1 mol / L, 1 mol / L to 2.1 mol / L, 2.1 mol / L to 3.5 mol / L, 0.8 mol / L to 2.5 mol / L, 0.3 mol / L to 3 mol / L, etc. The concentration of the precipitant can be 0.3 mol / L, 0.32 mol / L, 0.35 mol / L, 0.38 mol / L, 0.40 mol / L, 0.45 mol / L, 0.48 mol / L, 0.5 mol / L, or any range of two of the above values, such as 0.3 mol / L to 0.38 mol / L, 0.38 mol / L to 0.45 mol / L, 0.45 mol / L to 0.5 mol / L, etc. The pH can be 12.1, 12.2, 12.3, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, or any range of two of the above values, such as 12.1 to 12.5, 12.5 to 12.8, 12.8 to 13.0, etc. The reaction temperature can be 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, or any range of two of the above values, such as 50℃~58℃, 58℃~65℃, 65℃~70℃, etc. The reaction time can be 4h, 4.5h, 4.8h, 5h, 5.2h, 5.5h, 5.7h, 6.0h, 6.3h, 6.5h, 6.6h, 6.8h, 7h, or any range of two of the above values, such as 4h~5.2h, 5.2h~6.3h, 6.3h~7h, etc. In this embodiment, the inert atmosphere is nitrogen; in other embodiments, the inert atmosphere can also be argon, etc.

[0106] S330: Adjust the pH of the first intermediate to 10.5-11 and react for 13-17 hours to obtain the second intermediate.

[0107] In this embodiment, the pH of the reaction is lowered to 10.5–11, allowing the reaction to transition from nucleation to growth. Short-term pH reduction can decrease the formation of new crystal nuclei and improve the particle size uniformity of the nickel-cobalt-manganese hydroxide secondary particles. The pH can be 10.5, 10.6, 10.7, 10.8, 10.85, 10.9, 11.0, or any range of two of these values, such as 10.5–10.7, 10.7–10.85, or 10.85–11.0. The reaction time can be 13h, 13.5h, 13.8h, 14h, 14.5h, 15.0h, 15.6h, 16.2h, 16.5h, 16.8h, 17h, or any range of two of the above values, such as 13h~14.5h, 14.5h~16.2h, 16.2h~17h, etc.

[0108] S340: Adjust the pH of the second intermediate to 10-10.4 and react for 55-80 h to obtain nickel cobalt manganese hydroxide with a volume average particle size (DV50) of 8.5 μm-12 μm.

[0109] In this embodiment, the step of forming nickel-cobalt-manganese hydroxide is the growth period. Maintaining a low pH in the range of 10 to 10.4 can inhibit nucleation and prevent the formation of small particles. Stable reaction conditions can improve the overall crystallinity of secondary particles. The pH can be 10, 10.1, 10.2, 10.3, 10.4, or any range of two of the above values, such as 10–10.2 or 10.2–10.4. The reaction time can be 55 h, 58 h, 60 h, 65 h, 70 h, 73 h, 75 h, 76 h, 78 h, 80 h, or any range of two of the above values, such as 55 h–65 h, 65 h–76 h, or 76 h–80 h. The volume average particle size (DV50) of nickel cobalt manganese hydroxide can be 8.5 μm, 8.8 μm, 9.0 μm, 9.2 μm, 9.5 μm, 10 μm, 11 μm, 11.5 μm, 12 μm, or any range of two of the above values, such as 8.5 μm to 9.5 μm, 9.5 μm to 11 μm, 11 μm to 12 μm, etc.

[0110] S350: Nickel-cobalt-manganese hydroxide is mixed with lithium salt and sintered to obtain lithium nickel-cobalt-manganese oxide cathode material.

[0111] In this embodiment, a solid-state reaction is achieved by sintering nickel-cobalt-manganese hydroxide with a lithium salt to generate a lithium nickel-cobalt-manganese oxide cathode material. The lithium salt is one or a mixture of two or more of LiOH·H₂O, Li₂CO₃, Li₂SO₄, LiNO₃, LiC₂O₄, and CH₃COOLi. In this embodiment, the metal molar ratio Li / Me of the lithium salt to the ternary nickel-cobalt-manganese hydroxide precursor is 1.0–1.2, where Me is the total molar amount of Ni, Co, and Mn elements.

[0112] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor among all transition metal elements is controlled to be greater than or equal to 0.85, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of the total transition metal elements, thereby resulting in better electrochemical performance of the lithium-ion secondary battery. By controlling the concentration of the precipitant, the concentration of the complexing agent, the pH, the temperature, and the time, the nickel-cobalt-manganese hydroxide precursor also exhibits the particle size distribution of the secondary particles provided in the first aspect of this application. Controlling the volume average particle size (DV50) of the nickel-cobalt-manganese hydroxide precursor within the range of 8.5 μm to 12 μm helps to further control the volume average particle size (DV50) of the lithium nickel-cobalt-manganese oxide cathode material. The lithium nickel-cobalt-manganese oxide cathode material is obtained by sintering the nickel-cobalt-manganese hydroxide with a lithium salt.

[0113] In another embodiment, refer to Figure 4 The preparation methods of positive electrode active materials include:

[0114] S410: Provides a solution containing a nickel source, a cobalt source and a manganese source, wherein the molar ratio of the nickel source, the cobalt source and the manganese source is x:y:(1-xy), and x≥0.85.

[0115] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0116] S420: A complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitant with a concentration of 0.3 mol / L to 0.5 mol / L are added to a solution containing nickel, cobalt, and manganese sources. Under an inert atmosphere, the pH is controlled within the range of 12.1 to 13, and the reaction is carried out at 50℃ to 70℃ for 4 to 7 hours to form the first intermediate product.

[0117] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0118] S430: Adjust the pH of the first intermediate to 10.5-11 and react for 13-17 hours to obtain the second intermediate.

[0119] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0120] S440: Adjust the pH of the second intermediate to 10-10.4 and react for 55-80 h to obtain nickel cobalt manganese hydroxide with a volume average particle size (DV50) of 8.5 μm-12 μm.

[0121] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0122] S450: Nickel-cobalt-manganese hydroxide is mixed with lithium salt and sintered for the first time to obtain the first product.

[0123] In this embodiment, nickel cobalt manganese hydroxide is mixed with lithium salt and subjected to a first high-temperature sintering to obtain a first product; the first product is mixed with a first coating source and subjected to a second sintering to obtain a second product, wherein the second product is a lithium nickel cobalt manganese oxide cathode material with the first coating source coated on its surface.

[0124] In one embodiment of this application, the temperature of the first sintering is 725℃~780℃, and the time of the first sintering is 7h~14h. In this embodiment, the temperature and time of the first sintering and the temperature and time of the second sintering are controlled within the above ranges to give the material a better crystallization state, thereby improving the electrochemical performance of the lithium nickel cobalt manganese oxide cathode material. The temperature of the first sintering can be 725℃, 735℃, 746℃, 755℃, 770℃, 775℃, 780℃, etc., or any range of two of the above values, such as 720℃~735℃, 735℃~755℃, 755℃~780℃, 710℃~746℃, 720℃~770℃, 746℃~780℃, etc. The first sintering time can be 7h, 7.5h, 8.2h, 8.8h, 9.2h, 10h, 12h, 14h, or any range of two of the above values, such as 7h~9.2h, 9.2h~14h, 8.2h~12h, etc.

[0125] In another embodiment of this application, nickel-cobalt-manganese hydroxide, lithium salt, and a dopant source are mixed and subjected to a first sintering to obtain a first product. The dopant source includes one or more of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, or Ti sources. In this embodiment, incorporating one or more of Mg, Na, Zr, Y, Al, Ca, W, Nb, Ta, Sr, or Ti sources into the positive electrode active material can improve the crystal structure of the material, reduce distortion of the layered structure, and thereby improve the structural stability and cycle life of the lithium nickel-cobalt-manganese oxide positive electrode material.

[0126] S460: The first product is mixed with the first coating source and then sintered a second time to obtain the second product. The temperature of the second sintering is lower than that of the first sintering.

[0127] In this embodiment, the material undergoes secondary sintering to achieve a better crystallinity, thereby improving the electrochemical performance of the lithium nickel cobalt manganese oxide cathode material. The coating layer formed by the first coating source can also reduce the possibility of side reactions between the lithium nickel cobalt manganese oxide cathode material and the electrolyte, further improving the electrochemical performance of the lithium-ion secondary battery.

[0128] In this embodiment, the temperature of the second sintering is 400℃~615℃, and the time of the second sintering is 5h~11h. The temperature of the second sintering can be 400℃, 420℃, 480℃, 540℃, 580℃, 615℃, or any range of any two of the above values, such as 400℃~540℃, 540℃~650℃, 480℃~580℃, 420℃~615℃, etc. The time of the second sintering can be 5h, 6.5h, 8.2h, 8.7h, 9.2h, 11h, or any range of any two of the above values, such as 5h~8.7h, 8.7h~11h, 6.5h~9.2h, etc.

[0129] In this embodiment, a coating layer can be formed on the surface of lithium nickel cobalt manganese oxide through two sintering processes, which can improve the electrochemical performance of lithium-ion secondary batteries.

[0130] In another embodiment of this application, reference is made to Figure 5 The preparation methods of positive electrode active materials include:

[0131] S510: Provides a solution containing a nickel source, a cobalt source and a manganese source, wherein the molar ratio of the nickel source, the cobalt source and the manganese source is x:y:(1-xy), and x≥0.85.

[0132] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0133] S520: A complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitant with a concentration of 0.3 mol / L to 0.5 mol / L are added to a solution containing nickel, cobalt, and manganese sources. Under an inert atmosphere, the pH is controlled within the range of 12.1 to 13, and the reaction is carried out at 50℃ to 70℃ for 4 to 7 hours to form the first intermediate product.

[0134] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0135] S530: Adjust the pH of the first intermediate to 10.5-11 and react for 13-17 hours to obtain the second intermediate.

[0136] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0137] S540: Adjust the pH of the second intermediate to 10-10.4 and react for 55-80 h to obtain nickel cobalt manganese hydroxide with a volume average particle size (DV50) of 8.5 μm-12 μm.

[0138] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0139] S550: Nickel-cobalt-manganese hydroxide is mixed with lithium salt and sintered for the first time to obtain the first product.

[0140] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0141] S560: The first product is mixed with the first coating source and then sintered a second time to obtain the second product. The temperature of the second sintering is lower than that of the first sintering.

[0142] The steps are the same as those in the above embodiments, and will not be explained in detail here.

[0143] S570: The second product is mixed with the second coating source and sintered for a third time to obtain the third product, which is a lithium nickel cobalt manganese oxide cathode material.

[0144] In this embodiment, a third sintering process allows for the further formation of a coating on the surface of the lithium nickel cobalt manganese oxide. In this embodiment, the second coating source, including one or more of B, Al, and Y sources, is beneficial for improving the interfacial stability of the positive electrode active material and enhancing the lithium-ion insertion / extraction capability. Specifically, the B source refines the primary grains, improving the lithium-ion insertion / extraction capability on the surface, while the coating formed by the Y source easily forms a protective layer on the surface, reducing surface activity and improving interfacial stability.

[0145] In one embodiment, the temperature of the third sintering is 250℃ to 348℃, and the sintering time is 5h to 12h; the second coating source includes one or more of B source, Al source, and Y source. The temperature of the third sintering can be 250℃, 268℃, 275℃, 280℃, 300℃, 320℃, 335℃, 348℃, etc., or a range of any two of the above values, such as 250℃ to 280℃, 280℃ to 320℃, 320℃ to 348℃, etc. The sintering time can be 5h, 5.5h, 6.8h, 8.8h, 9.2h, 10h, 12h, etc., or a range of any two of the above values, such as 5h to 8.8h, 8.8h to 12h, 6.8h to 10h, etc.

[0146] In the embodiments of the present application, through three sintering processes and controlling the sintering temperature within the above range, a coating material formed by two coating sources can be obtained on the surface of lithium nickel cobalt manganese oxide, which can improve the electrochemical performance of the lithium ion secondary battery.

[0147] The third aspect of the present application further provides a positive electrode active material, including lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; the secondary particles include: the first kind of secondary particles, the volume particle size distribution of the first kind of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the proportion of the number of the first kind of secondary particles is N1, 2% ≤ N1 < 10%; the second kind of secondary particles, the volume particle size distribution of the second kind of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the proportion of the number of the first kind of secondary particles is N2, 70% ≤ N2 < 85%; the third kind of secondary particles, the volume particle size distribution of the third kind of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the proportion of the number of the third kind of secondary particles is N3, 5% ≤ N3 < 28%.

[0148] In this embodiment, the proportion of nickel element in the nickel cobalt manganese hydroxide precursor in all transition metal elements is controlled within the range of greater than or equal to 0.85, so that the nickel element in the lithium nickel cobalt manganese positive electrode active material accounts for at least 0.85 of all transition metal elements, thereby making the electrochemical performance of the lithium ion secondary battery better. 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 present application is a polycrystalline material, and the polycrystalline material is composed of many grains with different orientations, that is, primary particles, and the grains are interconnected through grain boundaries. The positive electrode active material includes secondary particles, and the secondary particles include the first kind of secondary particles, the second kind of secondary particles and the third kind of secondary particles, and these secondary particles are prepared at one time. The lithium ion secondary battery prepared by the above method has a higher tap density of the positive electrode sheet, and the secondary particles in the positive electrode sheet are not easily broken as the tap density of the positive electrode sheet increases, so that the lithium ion secondary battery has a high volumetric energy density, thereby improving the electrochemical performance of the lithium ion secondary battery.

[0149] In one embodiment, one or two or three of the first kind of secondary particles, the second kind of secondary particles, and the third kind of secondary particles are circular secondary particles, and for the circular secondary particles, in the scanning electron microscope image, the ratio of the volume particle size distribution of the secondary particles to the shortest diameter is d1 / d2, 1 ≤ d1 / d2 ≤ 1.2.

[0150] In this embodiment, one, two, or three of the first, second, and third types of secondary particles are spherical secondary particles with a ratio of their longest to shortest diameter within the aforementioned range. This results in a higher degree of internal ordering of the secondary particles, reduced friction between them, and a higher compaction density under the same pressure. During cyclic charging and discharging, the spherical secondary particles have a lower degree of stress accumulation, making it easier to release the generated stress and reducing the probability of particle breakage. This enables the lithium-ion secondary battery to have a high volumetric energy density, thereby improving the electrochemical performance of the lithium-ion secondary battery.

[0151] In one embodiment, the positive electrode active material includes a structure with the 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.

[0152] In this 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.

[0153] The fourth aspect of the present application further provides a method for preparing a positive electrode active material, including: providing a solution containing a nickel source, a cobalt source, and a manganese source, wherein the molar ratio of the nickel source, the cobalt source, and the manganese source is x:y:(1-x-y), and x≥0.85; adding a complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitating agent with a concentration of 0.3 mol / L to 0.5 mol / L into the solution containing the nickel source, the cobalt source, and the manganese source, under an inert atmosphere, controlling the pH range to be 12.1 to 13, reacting for 4 h to 7 h at 50 to 70 °C to form a first intermediate product; adjusting the pH of the first intermediate product to 10.5 to 11 and reacting for 13 h to 17 h to obtain a second intermediate product; adjusting the pH of the second intermediate product to 10 to 10.4 and reacting for 55 h to 80 h to obtain nickel cobalt manganese hydroxide, and the volume average particle size DV50 of the nickel cobalt manganese hydroxide is 8.5 μm to 12 μm; mixing the nickel cobalt manganese hydroxide with a lithium salt and sintering to obtain a lithium nickel cobalt manganese oxide positive electrode material, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.85; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; the secondary particles include a first type of secondary particles, a second type of secondary particles, and a third type of secondary particles, the volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the number proportion of the first type of secondary particles is N1, 2% ≤ N1 < 10%; the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the number proportion of the second type of secondary particles is N2, 70% ≤ N2 < 85%; the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the number proportion of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

[0154] In this embodiment, the proportion of nickel in the nickel-cobalt-manganese hydroxide precursor is controlled to be greater than or equal to 0.85 of all transition metal elements, ensuring that the nickel content in the subsequently prepared lithium nickel-cobalt-manganese cathode active material is at least 0.85% of all transition metal elements, thereby resulting in better electrochemical performance of the lithium-ion secondary battery. Furthermore, during the preparation of the nickel-cobalt-manganese hydroxide precursor, the precipitant reacts with the nickel, cobalt, and manganese sources to form a precipitate, and the complexing agent effectively complexes metal ions such as Ni, Co, and Mn in the liquid, helping to control the composition of the cathode active material precursor. By controlling the concentrations of the mixed salt solution, the precipitant, the complexing agent, the pH, the temperature, and the time within the aforementioned ranges, the nickel-cobalt-manganese hydroxide precursor exhibits the secondary particle size distribution provided in the first aspect of this application. Specifically, in the first intermediate product formation stage, the pH is controlled within the range of 12.1–13. Maintaining a higher pH can inhibit the growth of seed crystals in the overall particles and maintain the uniformity of the secondary particle size. The number of seed crystals is adjusted by controlling the nucleation time to 4–7 hours. In the second intermediate product formation stage, the pH of the reaction is lowered to 10.5–11, allowing the reaction to transition from nucleation to growth. Short-term pH reduction can decrease the formation of new crystal nuclei and improve the uniformity of the secondary particle size. The nickel-cobalt-manganese hydroxide formation stage is the growth period. Maintaining a low pH in the range of 10–10.4 can inhibit nucleation and avoid the formation of small particles. Stable reaction conditions can improve the crystallinity of the overall secondary particles. The preparation method of the positive electrode active material provided in the fourth aspect of this application is the same as the preparation method of the positive electrode active material in the lithium-ion secondary battery in the third aspect.

[0155] The fifth aspect of this application provides an electrical device comprising a lithium-ion secondary battery according to any of the above-mentioned methods, and / or a lithium-ion secondary battery prepared by any of the above-mentioned methods, and / or a positive electrode active material according to any of the above-mentioned methods, and / or a positive electrode active material prepared by any of the above-mentioned methods. The electrical device according to the embodiments of this application possesses at least the same advantages as the lithium-ion secondary battery of the first aspect, and / or at least the same advantages as the lithium-ion secondary battery prepared by the method of the second aspect, and / or at least the same advantages as the positive electrode active material of the third aspect, and / or at least the same advantages as the positive electrode active material prepared by the method of the fourth aspect.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.).

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.).

[0166] 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).

[0167] 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.

[0168] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0169] 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.

[0170] 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.

[0171] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into a battery cell assembly using a winding or stacking process.

[0178] In some implementations, such as Figure 6 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.

[0179] 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. For example, the insulating element may be made of plastic, rubber, etc.

[0180] 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.

[0181] 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.

[0182] Please refer to Figure 7The 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] As electrical equipment, individual battery cells and / or batteries can be selected according to their usage requirements.

[0188] Figure 8a and Figure 8b 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.

[0189] 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.

[0190] 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.

[0191] Example 1

[0192] 1) Preparation of positive electrode active material:

[0193] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0194] 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 (complexing agent) and 0.4 mol / L ammonia (precipitant) are added. Under a nitrogen atmosphere, the pH in the reactor is controlled at 13, and the temperature at 55°C to carry out a co-precipitation reaction. After 5 hours of reaction, the first intermediate product is formed.

[0195] 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.

[0196] Then, a complexing agent and ammonia were added to bring the pH of the reaction vessel to 10.2. The reaction was carried out for 60 hours to obtain nickel cobalt manganese hydroxide. The reaction caused the nickel cobalt manganese hydroxide particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel cobalt manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0197] 1.2) First sintering:

[0198] The aforementioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of SrO and ZrO2 to achieve a Li:Sr:Zr molar ratio of 1:0.0004:0.0006. The mixed powder was then added to a sintering furnace for a first sintering process at 725°C for 13 hours, followed by a cooling rate of 5°C / min to room temperature, yielding lithium transition metal oxide (Li(Ni)). 0.93 Co 0.06 Mn 0.01 ) 0.999 Sr 0.0004 Zr 0.0006 O2).

[0199] 1.3) Second sintering:

[0200] The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoOOH and Al2O3 to make the molar ratio of Li, Co and Al 1:0.011:0.005. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 615℃ for 7.5h. After that, the temperature was lowered to room temperature at a rate of 5℃ / min.

[0201] 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℃.

[0202] 1.5) Third sintering:

[0203] The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Y2O3 and H2BO3 to achieve a molar ratio of lithium, yttrium, and boron of 1:0.005:0.003. The mixed powder was then sintered for the third time at 348°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 ) 0.999 Sr 0.0004 Zr 0.0006 O2.

[0204] 2) Preparation of positive electrode sheet.

[0205] 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.

[0206] 3) Preparation of negative electrode materials.

[0207] 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.

[0208] 4) Preparation of electrolyte.

[0209] The electrolyte was a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC), wherein the volume ratio of EC, DEC, and DMC was 1:1:1. LiPF6 was then dissolved in the above organic solvent at a concentration of 1 mol / L.

[0210] 5) Separation membrane.

[0211] A 13μm thick polyethylene separator film was selected.

[0212] 6) Preparation of lithium-ion batteries.

[0213] 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.

[0214] Example 2

[0215] Similar to Example 1, the difference is:

[0216] 1) Preparation of positive electrode active material:

[0217] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0218] 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 (a complexing agent) and 0.5 mol / L ammonia (as a precipitant) are added. Under a nitrogen atmosphere, the pH in the reactor is controlled at 12.1, and the temperature at 70°C to carry out a co-precipitation reaction. After 4 hours of reaction, the first intermediate product is formed.

[0219] Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.8. React for 13 hours to obtain the second intermediate product.

[0220] 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 55 hours to obtain nickel cobalt manganese hydroxide. The reaction caused the nickel cobalt manganese hydroxide particles to grow to the target Dv50 of about 8.5 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel cobalt manganese strong oxide precursor (Ni). 0.85 Co 0.14 Mn 0.01 (OH)2).

[0221] 1.2) First sintering:

[0222] 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 SrO and ZrO2 to achieve a Li:Sr:Zr molar ratio of 1:0.0004:0.0006. The mixed powder was then added to a sintering furnace for a first sintering process at 725°C for 7 hours, followed by a cooling rate of 5°C / min to room temperature, yielding lithium transition metal oxide (Li(Ni)). 0.85 Co 0.14 Mn 0.01 ) 0.999 Sr 0.00004 Zr 0.0006 O2).

[0223] 1.3) Second sintering:

[0224] The lithium transition metal oxide obtained in step 1.12) was crushed and mixed with CoOOH and Al2O3 to make the molar ratio of Li, Co and Al 1:0.011:0.005. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 615℃ for 5 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0225] 1.4) Add 300g of the powder obtained in step 1.13) to 300mL of deionized water and stir for 5min. Then filter to obtain solid powder and dry at 60℃.

[0226] 1.5) Third sintering:

[0227] The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Y2O3 and H2BO3 to achieve a molar ratio of lithium, yttrium, and boron of 1:0.005:0.003. The mixed powder was then sintered for the third time at 250°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 ) 0.999 Sr 0.0004 Zr 0.0006 O2.

[0228] Example 3

[0229] Similar to Example 1, the difference is:

[0230] 1) Preparation of positive electrode active material:

[0231] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0232] 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. Next, 0.2 mol / L sodium carbonate and 0.4 mol / L ammonia were added. Under a nitrogen atmosphere, the pH in the reactor was controlled at 12.5, and the temperature at 58°C to carry out a co-precipitation reaction. After 7 hours of reaction, the first intermediate product was formed.

[0233] 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.

[0234] Subsequently, a complexing agent and ammonia were added to bring the pH of the reactor to 10.4, and the reaction was carried out for 80 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the nickel-cobalt-manganese hydroxide particles to grow to the target Dv50 of approximately 12 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.9 Co 0.09 Mn 0.01 (OH)2).

[0235] 1.2) First sintering:

[0236] The aforementioned nickel-cobalt-manganese strong oxide precursor was mixed with LiOH at a molar ratio of 1:1.05, followed by the addition of SrO and ZrO2 to achieve a Li:Sr:Zr molar ratio of 1:0.0004:0.0006. The mixed powder was then added to a sintering furnace for a first sintering process at 780°C for 14 hours, followed by a cooling rate of 5°C / min to room temperature, yielding lithium transition metal oxide (Li(Ni)). 0.9 Co 0.09 Mn 0.01 ) 0.999 Sr 0.0004 Zr 0.0006 O2).

[0237] 1.3) Second sintering:

[0238] After crushing the lithium transition metal oxide obtained in step 1.2), it was mixed with CoOOH and Al2O3 to make the molar ratio of Li, Co and Al 1:0.011:0.005. The mixed powder was then added to a sintering furnace for a second sintering at a temperature of 400℃ for 11 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0239] 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℃.

[0240] 1.5) Third sintering:

[0241] 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 1:0.005:0.003. The mixed powder was then sintered for the third time at 348°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 Li(Ni) of Example 3. 0.9 Co 0.09 Mn 0.01 ) 0.999 Sr 0.0004Zr 0.0006 O2.

[0242] Example 4

[0243] Same as Example 1, except that:

[0244] 1) Preparation of positive electrode active material:

[0245] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0246] 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. Following this, 3.5 mol / L sodium carbonate and 0.35 mol / L ammonia were added. Under a nitrogen atmosphere, the pH in the reactor was controlled at 13, and the temperature at 50°C to carry out a co-precipitation reaction. After 5 hours of reaction, the first intermediate product was formed.

[0247] Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.6. React for 15.5 hours to obtain the second intermediate product.

[0248] Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10, and the reaction was carried out for 60 hours to obtain nickel cobalt manganese hydroxide. The reaction caused the nickel cobalt manganese hydroxide particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel cobalt manganese strong oxide precursor (Ni). 0.95 Co 0.04 Mn 0.01 (OH)2).

[0249] Example 5

[0250] Same as Example 1, except that:

[0251] 1) Preparation of positive electrode active material:

[0252] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0253] 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. Next, 2.1 mol / L sodium carbonate and 0.4 mol / L ammonia were added. Under a nitrogen atmosphere, the pH in the reactor was controlled at 13, and the temperature at 55°C to carry out a co-precipitation reaction. After 5 hours of reaction, the first intermediate product was formed.

[0254] 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.

[0255] Then, a complexing agent and ammonia were added to bring the pH in the reactor to 10.3, and the reaction was carried out for 65 hours to obtain nickel cobalt manganese hydroxide. The reaction caused the nickel cobalt manganese hydroxide particles to grow to the target Dv50 of about 9.5 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel cobalt manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0256] Example 6

[0257] Same as Example 1, except that:

[0258] 1) Preparation of positive electrode active material:

[0259] 1.2) First sintering:

[0260] The aforementioned nickel-cobalt-manganese strong oxide precursor was mixed with Li₂O₃ at a molar ratio of 1:1.05, followed by the addition of Sb₂O₃ and ZrO₂ to achieve a Li:Sb:Zr molar ratio of 1:0.0008:0.0006. The mixed powder was then added to a sintering furnace for a first sintering process at 735°C for 12 hours, followed by a cooling rate of 5°C / min to room temperature, yielding lithium transition metal oxide (Li(Ni)O₂)O₃. 0.93 Co 0.06 Mn 0.01 ) 0.9986 Sb 0.0008 Zr 0.0006 O2).

[0261] Example 7

[0262] Same as Example 1, except that:

[0263] 1) Preparation of positive electrode active material:

[0264] 1.3) Second sintering:

[0265] The lithium transition metal oxide obtained in step 1.2) was crushed and mixed with CoOOH and Ti2O3 to make the molar ratio of Li, Co and Ti 1:0.011:0.005. The mixed powder was then added to a sintering furnace for a second sintering at 500℃ for 10 hours, and then cooled to room temperature at a rate of 5℃ / min.

[0266] Example 8

[0267] Same as Example 1, except that:

[0268] 1) Preparation of positive electrode active material:

[0269] 1.5) Third sintering:

[0270] The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with H2BO3 and Al2O3, so that the molar ratio of lithium, aluminum, and boron was 1:0.005:0.003. The mixed powder was then sintered for the third time at 300°C for 7 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 ) 0.999 Sr 0.0004 Zr 0.0006 O2.

[0271] Comparative Example 1

[0272] Same as Example 1, except that:

[0273] 1) Preparation of positive electrode active material:

[0274] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0275] 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. Next, 0.8 mol / L sodium carbonate and 0.25 mol / L ammonia were added. Under a nitrogen atmosphere, the pH in the reactor was controlled at 11.5, and the temperature at 64°C to carry out a co-precipitation reaction. After 6 hours of reaction, the first intermediate product was formed.

[0276] Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 10.2. React for 17 hours to obtain the second intermediate product.

[0277] Subsequently, a complexing agent and ammonia were added to bring the pH of the reactor to 9.6, and the reaction was carried out for 65 hours to obtain nickel-cobalt-manganese hydroxide. The reaction caused the nickel-cobalt-manganese hydroxide particles to grow to the target Dv50 of approximately 12 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel-cobalt-manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0278] 1.5) Third sintering:

[0279] The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Y2O3 and H2BO3 to achieve a molar ratio of lithium, yttrium, and boron of 1:0.005:0.003. 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 ) 0.999 Sr 0.0004 Zr 0.0006 O2.

[0280] Comparative Example 2

[0281] The same as the embodiment, except that:

[0282] 1) Preparation of positive electrode active material:

[0283] 1.1) Preparation of nickel-cobalt-manganese hydroxide precursor:

[0284] 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. Next, 0.8 mol / L sodium carbonate and 0.55 mol / L ammonia were added. Under a nitrogen atmosphere, the pH in the reactor was controlled at 14, and the temperature at 61°C to carry out a co-precipitation reaction. After 4 hours of reaction, the first intermediate product was formed.

[0285] Continue adding complexing agent and ammonia water, and gradually reduce the pH in the reactor to 11.5. React for 13 hours to obtain the second intermediate product.

[0286] Then, a complexing agent and ammonia were added to bring the pH of the reactor to 10.6, and the reaction was carried out for 58 hours to obtain nickel cobalt manganese hydroxide. The reaction caused the nickel cobalt manganese hydroxide particles to grow to the target Dv50 of about 10 μm. After the reaction was completed, the particles were washed and dried to obtain the nickel cobalt manganese strong oxide precursor (Ni). 0.93 Co 0.06 Mn 0.01 (OH)2).

[0287] 1.5) Third sintering:

[0288] The powder obtained in step 1.4) was added to a sintering furnace and thoroughly mixed with Y2O3 and H2BO3 to achieve a molar ratio of lithium, yttrium, and boron of 1:0.005:0.003. 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 ) 0.999 Sr 0.0004 Zr 0.0006 O2.

[0289] Furthermore, the percentage of the first type of secondary particles N1, the ratio of the longest diameter to the shortest diameter of the first type of secondary particles d1 / d2, the percentage of the second type of secondary particles N2, the ratio of the longest diameter to the shortest diameter of the second type of secondary particles d1 / d2, the percentage of the third type of secondary particles N3, the ratio of the longest diameter to the shortest diameter of the third type of secondary particles d1 / d2, the ratio of the number of the second type of secondary particles to the number of the first type of secondary particles N2 / N1, 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 Table 2.

[0290] The lithium-ion secondary batteries obtained in Examples 1-8 and Comparative Examples 1 and 2 were subjected to battery performance testing. Detailed process and performance parameters are shown in Table 1 and Table 2.

[0291] Test method:

[0292] 1. 0.1C specific capacity test

[0293] 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.

[0294] 2. Cyclic performance test at 25℃

[0295] 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. Capacity retention after 100 cycles = D100 / D1.

[0296] 3. Laser particle size testing

[0297] ① Prepare the sample powder, add surfactant and deionized water, and sonicate to ensure that the sample is completely dispersed in the dispersant;

[0298] ② Adjust the testing instrument and align it with the sample. Inject the sample into the laser particle size analyzer's test cell, ensuring stable suspension. Turn on the light source. Under the illumination of the laser beam, the particle size distribution characteristics can be determined by receiving and measuring the energy distribution of the scattered light. Instrument model: Master Size 3000Hydro EV / Hydro 2000MU.

[0299] 4. Powder compaction density test

[0300] 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.

[0301] 5. Specific surface area test

[0302] 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.

[0303] 6. Electrode compaction density test method

[0304] After the positive electrode active material is prepared into an electrode sheet, its length L0 is measured. The sheet is then placed on a roller press and rolled 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 P1 under the corresponding pressure is then: P1 = M1 / L2, and the elongation Q1 = (L1 - L0) / L0. Based on the measured compaction density under different elongation rates, the electrode compaction density corresponding to 0.7% elongation can be fitted.

[0305] 7. Average particle size of primary particles

[0306] 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.

[0307] 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 single measurement is calculated as the sum of the sizes of all measured particles divided by the sum of the number of particles measured in a single measurement.

[0308] 8. Volumetric energy density test

[0309] 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, left 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.

[0310]

[0311]

[0312] According to the test results in Tables 1 and 2, the secondary particles in the positive electrode active materials of Examples 1 to 8 include three different particle sizes. The compaction density of the positive electrode active material, the compaction density of the positive electrode sheet, the specific capacity, the cycle capacity retention rate, and the volumetric energy density are all stronger than those of Comparative Examples 1 and 2. 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 by utilizing the particle size and quantity distribution of the secondary particles provided in the examples of this application, the compaction density of the positive electrode active material, the compaction density of the positive electrode sheet, and the energy density can be improved. Furthermore, the particle size and quantity distribution of these secondary particles makes it less likely for the secondary particles to break as the compaction density of the positive electrode sheet increases, thereby enabling the lithium-ion secondary battery to have higher specific capacity, cycle capacity retention rate, and volumetric energy density, and improving the electrochemical performance of the lithium-ion secondary battery.

[0313] 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 plate, a negative electrode plate and an electrolyte. The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.

93. The positive electrode active material includes secondary particles, and the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm. The secondary particles include: The first kind of secondary particles, the volume particle size distribution of the first kind of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the quantity proportion of the first kind of secondary particles is N1, 2% ≤ N1 < 10%. The second kind of secondary particles, the volume particle size distribution of the second kind of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the quantity proportion of the second kind of secondary particles is N2, 70% ≤ N2 < 85%. The third kind of secondary particles, the volume particle size distribution of the third kind of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the quantity proportion of the third kind of secondary particles is N3, 5% ≤ N3 < 28%.

2. The lithium-ion secondary battery according to claim 1, characterized in that, One or two or three of the first kind of secondary particles, the second kind of secondary particles, and the third kind of secondary particles are circular secondary particles, and for the circular secondary particles, in the scanning electron microscope image, the ratio of the longest diameter to the shortest diameter of the secondary particles is d1 / d2, 1 ≤ d1 / d2 ≤ 1.

2.

3. The lithium-ion secondary battery according to claim 1, characterized in that, The ratio of the quantity of the second kind of secondary particles to the quantity of the first kind of secondary particles is 7 to 42.

5.

4. The lithium-ion secondary battery according to claim 1, characterized in that, The average particle size of the primary particles is 100 nm to 500 nm.

5. The lithium-ion secondary battery according to claim 1, characterized in that, The compaction density of the positive electrode active material under 5T pressure is 3.35 g / cm³. 3 ~3.6g / cm 3 .

6. The lithium-ion secondary battery according to claim 1, characterized in that, The specific surface area of the positive electrode active material is 0.35 m² / g to 0.75 m² / g.

7. The lithium-ion secondary battery according to claim 1, characterized in that, The weight is 1.4 × 10⁻⁶. -4 g / mm 2 ~2.3×10 -4 g / mm 2 The compacted density of the positive electrode sheet at 0.7% elongation is 3.35 g / cm³. 3 ~3.7g / cm 3 .

8. The lithium-ion secondary battery according to any one of claims 1-7, 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, 0.93≤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.

9. A method for preparing a lithium-ion secondary battery, characterized in that, It includes: Providing a slurry containing a positive electrode active material, coating the slurry containing the positive electrode active material on a positive electrode current collector to form a positive electrode plate. The positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.

93. The positive electrode active material includes secondary particles, and the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm. The secondary particles include the first kind of secondary particles, the second kind of secondary particles and the third kind of secondary particles. The volume particle size distribution of the first kind of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the quantity proportion of the first kind of secondary particles is N1, 2% ≤ N1 < 10%. The volume particle size distribution of the second kind of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the quantity proportion of the second kind of secondary particles is N2, 70% ≤ N2 < 85%. The volume particle size distribution of the third kind of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the quantity proportion of the third kind of secondary particles is N3, 5% ≤ N3 < 28%. A separator is placed between the positive and negative electrodes to form a lithium-ion secondary battery.

10. The method for preparing a lithium-ion secondary battery according to claim 9, characterized in that, The method for preparing the positive electrode active material includes: A solution containing a nickel source, a cobalt source, and a manganese source is provided, wherein the molar ratio of the nickel source, the cobalt source, and the manganese source is x:y:(1-xy), and x≥0.93; A complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitant with a concentration of 0.3 mol / L to 0.5 mol / L are added to the solution containing nickel, cobalt and manganese sources. Under an inert atmosphere, the pH is controlled within the range of 12.1 to 13, and the reaction is carried out at 50 to 70°C for 4 to 7 hours to form the first intermediate product. The pH of the first intermediate was adjusted to 10.5-11, and the reaction was carried out for 13-17 hours to obtain the second intermediate. The pH of the second intermediate product was adjusted to 10-10.4, and the reaction was carried out for 55-80 hours to obtain nickel cobalt manganese hydroxide, wherein the volume average particle size (DV50) of the nickel cobalt manganese hydroxide was 8.5 μm-12 μm. The nickel-cobalt-manganese hydroxide was mixed with lithium salt and sintered to obtain a lithium nickel-cobalt-manganese oxide cathode material.

11. The method for preparing a lithium-ion secondary battery according to claim 10, characterized in that, The process of mixing the nickel-cobalt-manganese hydroxide with a lithium salt and then sintering it yields a lithium nickel-cobalt-manganese oxide cathode material, comprising: The nickel-cobalt-manganese hydroxide is mixed with lithium salt and subjected to a first sintering process to obtain the first product; The first product is mixed with the first coating source and then sintered a second time to obtain the second product. The temperature of the second sintering is lower than that of the first sintering.

12. The method for preparing a lithium-ion secondary battery according to claim 11, characterized in that, The temperature of the first sintering is 725℃~780℃, and the sintering time is 7h~14h; or / and, The second sintering temperature is 400℃~615℃, and the second sintering time is 5h~11h.

13. The method for preparing a lithium-ion secondary battery according to claim 11 or 12, characterized in that, The process of mixing the nickel-cobalt-manganese hydroxide with a lithium salt and then performing a first sintering to obtain a first product includes: The nickel-cobalt-manganese hydroxide, lithium salt, and dopant source are mixed and subjected to a first sintering process to obtain a first product. The dopant source includes one or more of the following: Mg source, Na source, Zr source, Y source, Al source, Ca source, W source, Nb source, Ta source, Sr source, or Ti source.

14. The method for preparing a lithium-ion secondary battery according to claim 11, characterized in that, The first coating source includes one or more of Co, Al, F, and Ti sources.

15. The method for preparing a lithium-ion secondary battery according to claim 11, wherein after mixing the first product with the first coating source and performing a second sintering to obtain the second product, the method further comprises: The second product is mixed with the second coating source and then sintered for a third time to obtain the third product, which is a lithium nickel cobalt manganese oxide cathode material.

16. The method for preparing a lithium-ion secondary battery according to claim 15, wherein the temperature of the third sintering is 250℃~348℃, and the time of the third sintering is 5h~12h; the second coating source includes one or more of B source, Al source, and Y source.

17. A positive electrode active material, characterized in that, It includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.93; the positive electrode active material includes secondary particles, the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm; The secondary particles include: The first type of secondary particles, the volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm; based on the total number of secondary particles, the proportion of the number of the first type of secondary particles is N1, 2% ≤ N1 < 10%; The second type of secondary particles, the volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm; based on the total number of secondary particles, the proportion of the number of the first type of secondary particles is N2, 70% ≤ N2 < 85% The third type of secondary particles, the volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm; based on the total number of secondary particles, the proportion of the number of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

18. The positive electrode active material according to claim 17, characterized in that, 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 for the circular secondary particles, in the scanning electron microscope image, the ratio of the volume particle size distribution to the shortest diameter of the secondary particles is d1 / d2, 1 ≤ d1 / d2 ≤ 1.

2.

19. The positive electrode active material according to claim 17 or 18, 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, 0.93≤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.

20. A method for preparing a positive electrode active material, characterized in that, It includes: Providing a solution containing a nickel source, a cobalt source, and a manganese source, wherein the molar ratio of the nickel source, the cobalt source, and the manganese source is x:y:(1 - x - y), x ≥ 0.93; Adding a complexing agent with a concentration of 0.2 mol / L to 3.5 mol / L and a precipitating agent with a concentration of 0.3 mol / L to 0.5 mol / L into the solution containing the nickel source, the cobalt source, and the manganese source, under an inert atmosphere, controlling the pH range to be 12.1 to 13, and reacting for 4 h to 7 h at 50 to 70 °C to form a first intermediate product; Adjusting the pH of the first intermediate product to 10.5 to 11 and reacting for 13 h to 17 h to obtain a second intermediate product; Adjusting the pH of the second intermediate product to 10 to 10.4 and reacting for 55 h to 80 h to obtain nickel cobalt manganese hydroxide, and the volume average particle size DV50 of the nickel cobalt manganese hydroxide is 8.5 μm to 12 μm; Mix the nickel cobalt manganese hydroxide with a lithium salt and sinter to obtain a lithium nickel cobalt manganese oxide cathode material. The cathode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel element in all transition metal elements is greater than or equal to 0.

93. The cathode active material includes secondary particles, and the secondary particles include primary particles, and the average particle size of the primary particles is 50 nm to 2 μm. The secondary particles include the first type of secondary particles, the second type of secondary particles and the third type of secondary particles. The volume particle size distribution of the first type of secondary particles is d11, 3 μm < d11 ≤ 7.5 μm. Based on the total number of secondary particles, the proportion of the number of the first type of secondary particles is N1, 2% ≤ N1 < 10%. The volume particle size distribution of the second type of secondary particles is d12, 7.5 μm < d12 ≤ 11 μm. Based on the total number of secondary particles, the proportion of the number of the second type of secondary particles is N2, 70% ≤ N2 < 85%. The volume particle size distribution of the third type of secondary particles is d13, 11 μm < d13 ≤ 15 μm. Based on the total number of secondary particles, the proportion of the number of the third type of secondary particles is N3, 5% ≤ N3 < 28%.

21. The method for preparing the positive electrode active material according to claim 20, characterized in that, The process of mixing the nickel cobalt manganese hydroxide with a lithium salt and sintering to obtain a lithium nickel cobalt manganese oxide cathode material includes: Mix the nickel cobalt manganese hydroxide with a lithium salt and conduct the first sintering to obtain a first product. The temperature of the first sintering is 725 °C to 780 °C, and the time of the first sintering is 7 h to 14 h. Mix the first product with a first coating source and conduct the second sintering to obtain a second product. The temperature of the second sintering is 400 °C to 615 °C, and the time of the second sintering is 5 h to 11 h. The first coating source includes one or more of Co source, Al source, F source, Ti source. Mix the second product with a second coating source and conduct the third sintering to obtain a third product, and the third product is a lithium nickel cobalt manganese oxide cathode material. The temperature of the third sintering is 250 °C to 348 °C, and the time of the third sintering is 5 h to 12 h. The second coating source includes one or more of B source, Al source, Y source.

22. The method for preparing the positive electrode active material according to claim 20 or 21, characterized in that, The process of mixing the nickel cobalt manganese hydroxide with a lithium salt and sintering to obtain a lithium nickel cobalt manganese oxide cathode material includes: Mix the nickel cobalt manganese hydroxide, a lithium salt and a doping source and conduct the first sintering to obtain a first product. Among them, the doping source includes one or more of Mg source, Na source, Zr source, Y source, Al source, Ca source, W source, Nb source, Ta source, Sr source or Ti source.

23. An electrical appliance, characterized in that, Include the lithium ion secondary battery according to any one of claims 1-8, and / or, the lithium ion secondary battery prepared by the preparation method according to any one of claims 9-16, and / or the cathode active material according to any one of claims 17-19, and / or, the cathode active material prepared by the preparation method of the cathode active material according to any one of claims 20-22.

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