Positive electrode active material and preparation method thereof, positive electrode plate, battery and electric equipment

Abstract

The invention provides a positive electrode active material and a preparation method thereof, a positive electrode plate, a battery and electric equipment, the 104 crystal face sub-grain size distribution of the positive electrode active material meets # imgabs 0 # imgabs 1 #, and delta Ln10, delta Ln50 and delta Ln90 are corresponding sub-grain size differences when the volume distribution cumulative percentages of Ln after 80 cycles and before the cycle of the positive electrode active material reach 10%, 50% and 90% respectively. Therefore, the structural stability of the positive electrode active material is improved, and the high-temperature performance of the battery is improved.

Description

Technical Field

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

[0002] Positive electrode active materials are sought after for their excellent electrochemical performance. During the charge and discharge process of positive electrode active materials, lithium ions are frequently inserted and extracted between the positive and negative electrodes, resulting in changes in the material structure. Especially at high or low temperatures, the change in the structure of the positive electrode active material will be aggravated, leading to the deterioration of electrical performance. Summary of the Invention

[0003] This application aims to solve at least one of the technical problems in the related art to some extent.

[0004] In a first aspect of this application, a positive electrode active material is provided, and the sub-grain size distribution of the 104 crystal plane of the positive electrode active material satisfies:

[0005] Wherein, ΔLn 10 , ΔLn 50 , ΔLn 90 are the differences in the sub-grain size corresponding to the cumulative percentage of the Ln volume distribution reaching 10%, 50%, and 90% respectively after 80 cycles of the positive electrode active material compared with before cycling.

[0006] For the positive electrode active material proposed in this application, by keeping ΔLn 10 , ΔLn 50 , ΔLn 90 within a suitable range, that is, the sub-grain size fluctuates within a small range, the structural stability of the material can be significantly improved, and the influence on lithium ion transport caused by structural changes can be reduced, thereby improving the high-temperature cycle performance of the battery.

[0007] According to some embodiments of this application, Thus, the lithium ion transport path is shortened, the structural stability of the positive electrode active material is improved, and the low-temperature and high-temperature performance of the battery is improved.

[0008] According to some embodiments of this application, the sub-grain size distribution satisfies: Kn' 90 =(Ln' 90 -Ln' 10 ) / Ln' 50 <1.8, optionally, 0.5<Kn' 90 <1.5, Kn 90 =(Ln 90 -Ln 10 ) / Ln 50 , Kn 90> Kn' 90 , where Ln 10 , Ln 50 , Ln 90 are the sub-grain sizes corresponding to when the cumulative percentage of the volume distribution of the sub-grains on the 104 crystal plane of the aforementioned positive electrode active material reaches 10%, 50%, and 90% respectively before 80 cycles, and Ln' 10 , Ln' 50 , Ln' 90 are the sub-grain sizes corresponding to when the cumulative percentage of the volume distribution of the sub-grains on the 104 crystal plane of the aforementioned positive electrode active material reaches 10%, 50%, and 90% respectively after 80 cycles. Thus, the sub-grain size distribution after cycling is narrower than that before cycling, indicating that the consistency of the sub-grain size does not deteriorate significantly after 80 cycles of charge and discharge, and further indicating that the material has good stability at the sub-grain level.

[0009] According to some embodiments of the present application, (Kn 90 - Kn' 90 ) / Kn 90 < 0.25, optionally, 0 < (Kn 90 - Kn' 90 ) / Kn 90 < 0.2. Thus, the volume change of the positive electrode active material is small and the structure is more stable.

[0010] According to some embodiments of the present application, in the X-ray diffraction pattern of the positive electrode active material, the lattice parameter c and the lattice parameter a satisfy: Δ(c / a) is less than 0.08% before and after 80 cycles; preferably less than 0.06%. Thus, the lattice change of the positive electrode active material is small before and after cycling, and the stability of the positive electrode active material is good.

[0011] According to some embodiments of the present application, the average particle size of the positive electrode active material particles is P 50 , and satisfies 1 μm ≤ P 50 ≤ 2.5 μm, optionally, 1.3 μm ≤ P 50 ≤ 2 μm. Thus, while improving the particle size uniformity of the positive electrode active material particles, the adhesion between particles is reduced.

[0012] According to some embodiments of the present application, the median particle size Dv 50 of the volume distribution of the positive electrode active material particles satisfies 2 μm ≤ Dv 50 ≤ 4.5 μm, optionally, 2.5 μm ≤ Dv 50 ≤ 4 μm. Thus, the transmission path of lithium ions is shortened and the kinetic performance of the positive electrode active material is improved.

[0013] According to some embodiments of the present application, 1 ≤ Dv50 / P 50 ≤2.5, optionally, 1.2 ≤ Dv 50 / P 50 ≤2.5. Thus, the agglomeration between the positive electrode active material particles is reduced.

[0014] According to some embodiments of the present application, it includes the compound shown in Formula Ι:

[0015] Li 1±a (Ni x Co y Mn z G b )M c O2 Formula I,

[0016] wherein, 0 ≤ a ≤ 0.1, 0 ≤ b ≤ 0.05, 0 ≤ c ≤ 0.05, 0.4 ≤ x < 1, 0 < y < 0.5, 0 ≤ z < 0.5, G includes at least one of Zr, Ti, Y, W, Al, Nb, and M includes at least one of La, Zr, B, Nb, Ti, W, Si, Mg, Al, Co.

[0017] According to some embodiments of the present application, 0 < b ≤ 0.05. Thus, the structural stability of the positive electrode active material is improved by doping elements, and the high-temperature performance of the battery is improved.

[0018] According to some embodiments of the present application, the positive electrode active material includes a matrix and a coating material located on at least part of the surface of the matrix, and the coating material includes the M element. Thus, the structural stability of the positive electrode active material is improved.

[0019] The second aspect of the present application provides a method for preparing the positive electrode active material provided in the first aspect of the present application, and the method includes:

[0020] Mix a nickel-cobalt-manganese precursor, a first lithium source, and an additive containing a doping element G to obtain a mixture;

[0021] Pre-sinter the mixture at a temperature of 400°C - 900°C to obtain a first intermediate product;

[0022] After mixing the first intermediate product with a second lithium source, heat it to a first constant temperature section and keep it warm. The temperature of the first constant temperature section is 500°C - 800°C. After the heat preservation ends, raise the temperature to conduct the first sintering on the mixture. The temperature of the first sintering is 800°C - 1000°C. After the first sintering ends, lower the temperature to a second constant temperature section. The temperature of the second constant temperature section is 300°C - 700°C and keep it warm to obtain a second intermediate product. The amount of substance of lithium element n (Li1) in the first lithium source(Li2) The ratio is greater than 1.43;

[0023] Perform a second sintering on the second intermediate product, where the temperature of the second sintering is less than or equal to the temperature of the first sintering, to obtain the positive electrode active material.

[0024] In the method for preparing the positive electrode active material proposed in this application, adding a lithium source for the first time and controlling the temperature of the pre-sintering can enable lithium to melt and penetrate into the interior of the precursor, react preferentially from the interior of the precursor, and the surface layer is in a lithium-deficient state. Adding a lithium source for the second time and performing a first constant temperature and a first sintering with the first intermediate product, and controlling the temperature of the first constant temperature section and the first sintering can enable the lithium source to melt on the surface of the particles with a lithium-deficient surface, and make the lithium on the particle surface react with the first intermediate product, achieving the purpose of uniform reaction inside and on the surface, thereby improving the structural stability of the positive electrode active material and the high-temperature performance of the battery. According to some embodiments of this application, the temperature of the second sintering is 300°C - 800°C.

[0025] According to some embodiments of this application, the method satisfies at least one of the following conditions:

[0026] The time of the pre-sintering is 3h - 12h;

[0027] The times of the first sintering and the second sintering are independently 6h - 12h respectively.

[0028] According to some embodiments of this application, the additive includes at least one of an oxide containing element G, a hydroxide containing element G, and a carbonate containing element G.

[0029] The third aspect of this application provides a positive electrode sheet, including the positive electrode active material provided in the first aspect of this application or the positive electrode active material prepared by the method provided in the second aspect of this application.

[0030] The fourth aspect of this application provides a battery, including the positive electrode sheet provided in the third aspect of this application.

[0031] The fifth aspect of this application provides an electrical device, including the battery provided in the fourth aspect of this application. Description of the Drawings

[0032] The above and / or additional aspects and advantages of this application will become apparent and be easily understood from the description of the embodiments in conjunction with the following drawings, where:

[0033] Figure 1 Shows a schematic flow chart of a method for preparing a positive electrode active material according to an embodiment of this application.

[0034] Figure 2Shows the SEM image of the positive electrode active material prepared in Example 1 of the present application.

[0035] Figure 3 Shows the SEM image of the positive electrode active material prepared in Comparative Example 2 of the present application.

[0036] Figure 4 Shows the schematic diagram of the change in the size distribution of the 104 crystal plane before and after cycling after the positive electrode active material prepared in Example 1 of the present application is assembled into a battery. Detailed Description of the Embodiments

[0037] The embodiments of the present application will be described in detail below. The following described embodiments are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those techniques or conditions not specified in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0038] The first aspect of the present application provides a positive electrode active material, and the size distribution of the 104 crystal plane sub-grains of the positive electrode active material satisfies: Wherein, ΔLn 10 , ΔLn 50 , ΔLn 90 are the differences in the sub-grain sizes corresponding to the cumulative percentage of the Ln volume distribution of the positive electrode active material reaching 10%, 50%, and 90% respectively after 80 cycles and before cycling. Specifically, ΔLn 10 = Ln' 10 - Ln 10 , ΔLn 50 = Ln' 50 - Ln 50 , ΔLn 90 = Ln' 90 - Ln 90 , Ln 10 , Ln 50 , Ln 90 are the sub-grain sizes corresponding to the cumulative percentage of the Ln volume distribution of the 104 crystal plane sub-grains of the positive electrode active material reaching 10%, 50%, and 90% respectively before 80 cycles, and Ln' 10 , Ln' 50 , Ln' 90 are the sub-grain sizes corresponding to the cumulative percentage of the Ln volume distribution of the 104 crystal plane sub-grains of the positive electrode active material reaching 10%, 50%, and 90% respectively after 80 cycles.

[0039] In this application, the positive electrode active material, conductive carbon black, and polyvinylidene fluoride (PVDF) are fully mixed in a mass ratio of 95:3:2 with an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry (with a solid content of 60% at 25°C). After coating this positive electrode slurry on aluminum foil and drying it at 120°C for 12 hours, it is stamped into shape under a pressure of 100 MPa to make a positive electrode plate with a diameter of 15.8 mm and a thickness of 3.2 mm, where the loading amount of the positive electrode active material is 15.5 mg / cm 2 . Inside a glove box filled with argon where both the water content and oxygen content are less than 5 ppm, the positive electrode plate, separator, negative electrode plate, and electrolyte are assembled into a CR2025 coin cell. The electrolyte uses an equal-volume mixture of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0040] The 80-cycle process includes the following steps:

[0041] Battery activation: Place the CR2025 coin cell in an incubator at 45°C and charge it at a constant current and constant voltage with a cut-off voltage of 3.0 - 4.4 V at a current of 0.2C until 4.4 V. After standing for 10 minutes, discharge it at a constant current of 0.2C until 3.0 V and leave it for 20 minutes;

[0042] High-temperature cycling: In an incubator at 45°C, charge the activated battery at a constant current and constant voltage at a current of 1C until 4.4 V, then stand for 10 minutes, discharge it at a constant current of 1C until 3.0 V, and leave it for 20 minutes, which is recorded as 1 cycle; Repeat the charge and discharge 80 times in the above manner to complete the high-temperature cycling process described in this scheme.

[0043] Record the discharge capacity of the first cycle as A1, the discharge capacity after 80 cycles as A2, and the high-temperature cycling capacity retention rate is recorded as A2 / A1 * 100%.

[0044] After 80 cycles, disassemble the battery cell to obtain the positive electrode plate, scrape off the powder on the positive electrode plate, and the sub-grain size Ln of the positive electrode active material is obtained by using the powder X-ray diffraction pattern measured by CuKα radiation and performing size statistics by the Fundamental Parameter fitting algorithm.

[0045] During the charge and discharge process of the ternary positive electrode active material, lithium ions in the positive electrode active material will continuously intercalate and deintercalate, resulting in changes in the lithium layer. Some transition metal ions will also change their valence states due to redox reactions and thus migrate between the layers. The changes in the lithium layer and transition metal layer of the positive electrode material provided in this application will bring about structural contraction or relaxation on the sub-grain level of the positive electrode active material. Within a suitable range, the sub-grain size ΔLn 10 、ΔLn50 , ΔLn 90 The appropriate change of can improve the stability of the material structure, and further optimize the stability of the material and the lithium-ion transport ability. The positive electrode active material proposed in this application, by making ΔLn 10 , ΔLn 50 , ΔLn 90 remain within a suitable range, that is, the sub-grain size fluctuates within a small range, can significantly improve the structural stability of the material, reduce the influence on lithium-ion transport caused by structural changes, and thus improve the high-temperature cycling performance of the battery.

[0046] As an example, ΔLn 10 can be etc., or can be a range composed of any of the above numerical values.

[0047] According to some specific embodiments of the present application,

[0048] As an example, ΔLn 50 can be etc., or can be a range composed of any of the above numerical values.

[0049] According to some specific embodiments of the present application,

[0050] As an example, ΔLn 90 can be etc., or can be a range composed of any of the above numerical values.

[0051] According to some specific embodiments of the present application,

[0052] According to some embodiments of the present application, the positive electrode active material includes a compound represented by Formula Ι:

[0053] Li 1±a (Ni x Co y Mn z G b )M c O2 Formula I,

[0054] wherein, 0 ≤ a ≤ 0.1, 0 ≤ b ≤ 0.05, 0 ≤ c ≤ 0.05, 0.4 ≤ x < 1, 0 < y < 0.5, 0 ≤ z < 0.5, G includes at least one of Zr, Ti, Y, W, Al, Nb, and M includes at least one of La, Zr, B, Nb, Ti, W, Si, Mg, Al, Co.

[0055] As an example, a can be 0, 0.03, 0.06, 0.08, 0.1, etc., or can be a range composed of any of the above numerical values.

[0056] As an example, b can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, etc., or can be a range composed of any of the above numerical values.

[0057] According to some specific embodiments of the present application, 0 < b ≤ 0.05. By doping the G element into the positive electrode active material, the structural stability of the positive electrode active material can be improved, and the high-temperature performance of the battery can be enhanced.

[0058] As an example, c can be 0.01, 0.02, 0.03, 0.04, 0.05, etc., or can be a range composed of any of the above numerical values.

[0059] As an example, x can be 0.4, 0.6, 0.8, 0.9, 0.95, etc., or can be a range composed of any of the above numerical values.

[0060] As an example, y can be 0.1, 0.2, 0.3, 0.4, 0.45, etc., or can be a range composed of any of the above numerical values.

[0061] As an example, z can be 0, 0.1, 0.2, 0.3, 0.4, 0.45, etc., or can be a range composed of any of the above numerical values.

[0062] According to some embodiments of the present application, the positive electrode active material includes a matrix and a coating material located on at least a part of the surface of the matrix, and the coating material includes the M element. Thereby, the structural stability of the positive electrode active material is improved.

[0063] According to some embodiments of the present application, Kn' 90 =(Ln' 90 -Ln' 10 ) / Ln' 50 <1.8. By making Kn' 90 <1.8, the uniformity of the sub-grain size and the homogeneity of the distribution of the material can be improved, which is beneficial to ensuring the stability of the material structure.

[0064] As an example, Kn' 90 can be 0.3, 0.6, 0.9, 1.2, 1.6, 1.7, etc., or can be a range composed of any of the above numerical values.

[0065] According to some specific embodiments of the present application, 0.5 < Kn' 90 <1.5, Kn 90 =(Ln 90 -Ln 10 ) / Ln50 , Kn 90 > Kn' 90 .

[0066] According to some embodiments of the present application, (Kn 90 - Kn' 90 ) / Kn 90 < 0.25.

[0067] During the charge and discharge process of the battery, the sub-grain volume of the crystal plane of the positive electrode active material 104 will change. Sub-grains of different sizes change to different degrees, which will cause changes in the sub-grain size distribution. By making (Kn 90 - Kn' 90 ) / Kn 90 within a suitable range, the volume change degree of the positive electrode active material before and after cycling can be reduced, and the structural stability of the positive electrode active material can be improved.

[0068] As an example, (Kn 90 - Kn' 90 ) / Kn 90 can be 0.1, 0.13, 0.16, 0.19, 0.22, 0.24, etc., or can be a range composed of any of the above values.

[0069] According to some specific embodiments of the present application, 0 < (Kn 90 - Kn' 90 ) / Kn 90 < 0.2.

[0070] According to some embodiments of the present application, in the X-ray diffraction pattern of the positive electrode active material, the lattice parameter c and the lattice parameter a satisfy: Δ(c / a) is less than 0.08% before and after 80 cycles. Specifically, the lattice parameters of the positive electrode active material before cycling are a and c, and the lattice parameters of the positive electrode active material after 80 cycles are c' and a', and Δ(c / a) = (c' / a' - c / a) / (c / a) × 100%.

[0071] The process of cycling the positive electrode material 80 times during the test of Δ(c / a) is the same as the cycling process during the test of the sub-grain size.

[0072] In this application, an X-ray diffraction pattern is obtained by an X-ray diffractometer (XRD). The c / a is the ratio of the dimensions of the unit cell along the c-axis and the a-axis obtained by refining the XRD pattern, which reflects the degree of anisotropy of the structure of the positive electrode active material. During the process of lithium ion insertion and extraction, the crystal will exhibit lateral or longitudinal contraction or expansion, resulting in a change in the c / a value. The change rate of c / a before and after cycling reflects the degree of change in the unit cell structure. The smaller the change rate, the less the material is affected by the outside at the crystal level, the positive electrode particles do not undergo significant lattice distortion, the interlayer stress is released sufficiently, and the lithium ion diffusion channel remains stable. Therefore, the structure of the material is stable.

[0073] In this application, the sub-grain size, lattice parameter a, and lattice parameter c of the 104 crystal plane of the positive electrode active material are all obtained by refining the XRD pattern. The sub-grain size is obtained by spherical fitting, which reflects the volume size of the sub-grains of the positive electrode active material at the microscopic level. Kn 90 and Kn' 90 The changes reflect the changes in their distribution uniformity at the sub-grain level; the change in the c / a value reflects the axial change at the unit cell level of the material, that is, the structural stability of the lithium layer and the metal layer. The stability of the material is reflected from two dimensions of sub-grains and unit cells.

[0074] When refining the XRD pattern in this application, the Rietveld analysis software used for refining includes but is not limited to TOPAS, Rietan, JANA, and JADE.

[0075] As an example, Δ(c / a) before and after 80 cycles can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, etc., or can be a range composed of any of the above values.

[0076] According to some specific embodiments of this application, Δ(c / a) is less than 0.06%.

[0077] According to some embodiments of this application, the average particle size of the positive electrode active material particles is P 50 , and satisfies 1 μm ≤ P 50 ≤ 2.5 μm. By making P 50 within the above range, on the one hand, the lithium ion transmission path can be shortened and the low-temperature performance of the battery can be improved; on the other hand, the adhesion between the positive electrode active material particles can be reduced, which is beneficial to the formation of single crystal particles. That is to say, by making ΔLn 10 , ΔLn 50 , ΔLn 90 remain within a suitable range and controlling the average particle size of the positive electrode active material particles, the structural stability and kinetic performance of the positive electrode active material can be improved, and further the high-temperature and low-temperature performance of the battery can be improved.

[0078] In this application, the average particle size P 50 is the diameter calculated by converting the projected area of 500 particles tested by a scanning electron microscope (SEM) into an equal-area standard circle and then calculating the average value, which is the average particle size of the positive electrode active material particles.

[0079] As an example, P 50 can be 1μm, 1.3μm, 1.7μm, 2μm, 2.3μm, 2.5μm, etc., or can be a range composed of any of the above values.

[0080] According to some specific embodiments of the present application, 1.3μm ≤ P 50 ≤ 2μm.

[0081] According to some embodiments of the present application, the median volume diameter Dv of the positive electrode active material particles 50 satisfies 2μm ≤ Dv 50 ≤ 4.5μm. Thereby, the transmission path of lithium ions is shortened and the low-temperature performance of the battery is improved.

[0082] In this application, Dv 50 can be obtained by testing with a laser particle size analyzer of the Mastersizer 3000 model of Marvern Company.

[0083] According to some specific embodiments of the present application, 2.5μm ≤ Dv 50 ≤ 4μm.

[0084] According to some embodiments of the present application, 1 ≤ Dv 50 / P 50 ≤ 2.5. By making the ratio of Dv 50 / P 50 within the above range, the agglomeration of the positive electrode active material is reduced, and during the battery cycling process, the risk of deterioration of the battery high-temperature cycle caused by the exposure of new interfaces due to the dispersion of the agglomerated particles is reduced.

[0085] According to some specific embodiments of the present application, 1.2 ≤ Dv 50 / P 50 ≤ 2.5.

[0086] The second aspect of the present application provides a method for preparing the positive electrode active material provided in the first aspect of the present application, and the method includes:

[0087] Mixing a nickel-cobalt-manganese precursor, a first lithium source, and an additive containing a doping element G to obtain a mixture;

[0088] Performing pre-sintering on the mixture, and the temperature of the pre-sintering is 400°C - 900°C to obtain a first intermediate product;

[0089] After mixing the first intermediate product with the second lithium source, heat it to the first constant temperature section and keep it warm. The temperature of the first constant temperature section is 500°C - 800°C. After the heat preservation ends, raise the temperature to conduct the first sintering on the mixture. The temperature of the first sintering is 800°C - 1000°C. After the first sintering ends, lower the temperature to the second constant temperature section. The temperature of the second constant temperature section is 300°C - 700°C and keep it warm to obtain the second intermediate product. The amount of substance n of lithium element in the first lithium source (Li1) and the amount of substance n of lithium element in the second lithium source (Li2) have a ratio greater than 1.43;

[0090] Conduct the second sintering on the second intermediate product. The temperature of the second sintering is less than or equal to the temperature of the first sintering to obtain the positive electrode active material.

[0091] In the method for preparing the positive electrode active material proposed in this application, adding the lithium source for the first time and controlling the temperature of the pre-sintering can enable lithium to melt and penetrate into the interior of the precursor, and react preferentially from the interior of the precursor. The surface layer is in a lithium-deficient state. Adding the lithium source for the second time to conduct the first constant temperature and the first sintering with the first intermediate product, and controlling the temperature of the first constant temperature and the first sintering can enable the lithium source to melt on the surface of the lithium-deficient particles, and make the lithium on the particle surface react with the first intermediate product, achieving the purpose of uniform internal and surface reactions, thereby improving the structural stability of the positive electrode active material and the high-temperature performance of the battery.

[0092] The method proposed in this application will be described in detail below. Refer to Figure 1 , the method includes:

[0093] S10: Mix the nickel cobalt manganese precursor, the first lithium source, and the additive containing the doping element G to obtain a mixture

[0094] In this step, mix the nickel cobalt manganese precursor and the first lithium source using a high-speed mixer to obtain a uniform mixture. The stirring speed of the high-speed mixer can be 300 rpm - 500 rpm, and the stirring time can be 20 min - 40 min.

[0095] According to some embodiments of the present application, the nickel cobalt manganese precursor, the first lithium source, and the additive containing element G can also be mixed using a high-speed mixer.

[0096] According to some embodiments of the present application, the additive includes at least one of an oxide containing element G, a hydroxide containing element G, and a carbonate containing element G.

[0097] During the sintering process, the nickel-cobalt-manganese precursor grows to form single crystals under the action of lithium salts. An additive containing element G is added, and element G can enter the material lattice to affect the orientation of the material. The sub-grain size of the additive in this application is similar to it, which can improve the structural stability of the cathode active material.

[0098] According to some embodiments of the present application, the nickel-cobalt-manganese precursor includes at least one of nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide.

[0099] S20: Pre-sinter the mixture at a temperature of 400°C - 900°C to obtain a first intermediate product

[0100] In this step, in an air or oxygen atmosphere, the mixture is placed in a kiln for pre-sintering.

[0101] As an example, the temperature of the pre-sintering can be 400°C, 500°C, 550°C, 600°C, 650°C, 700°C, 800°C, 900°C, etc., or can be a range composed of any of the above values.

[0102] As an example, the time of the pre-sintering can be 3h - 12h. For example, it can be 3h, 7h, 10h, 12h, etc., or can be a range composed of any of the above values.

[0103] By making the temperature and time of the pre-sintering within the above ranges, the lithium salt can be melted, enabling it to fully contact the precursor and form a lithiated precursor; if the temperature is too low, the lithium salt cannot fully contact the precursor or even does not melt; if the temperature is too high, the lithium salt may directly react on the local or surface layer of the precursor, resulting in lithium deficiency inside, affecting the transmission of lithium ions and the structural stability of the material.

[0104] S30: After mixing the first intermediate product with a second lithium source and heating it to a first constant temperature section for heat preservation, the temperature of the first constant temperature section is 500°C - 800°C. After the heat preservation ends, the temperature is raised to perform the first sintering on the mixture. The temperature of the first sintering is 800°C - 1000°C. After the first sintering ends, the temperature is lowered to a second constant temperature section, and the temperature of the second constant temperature section is 300°C - 700°C for heat preservation to obtain a second intermediate product. The amount of substance n of lithium element in the first lithium source (Li1) and the amount of substance n of lithium element in the second lithium source (Li2) The ratio of is greater than 1.43

[0105] In this step, in an air or oxygen atmosphere, the first intermediate product and the second lithium source are heated and raised in temperature in a kiln. There is a slightly positive pressure inside the kiln, with the pressure being 0 - 30 Pa. The temperature is raised at a rate of 1 °C / min - 4 °C / min to the first constant temperature stage. The temperature of the first constant temperature stage is 500 °C - 800 °C, and it is held for 2 h - 4 h. Then, it is raised in temperature at the same rate of temperature increase for the first sintering. The temperature of the first sintering is 800 °C - 1000 °C. After the first sintering is completed, the temperature is lowered to the second constant temperature stage. The temperature of the second constant temperature stage is 300 °C - 700 °C, and it is held for 2 h - 4 h. After the holding is completed, it is cooled to room temperature and crushed by a jet mill. The rotational speed of the classification wheel of the jet mill is 30 Hz - 50 Hz, and an intermediate product is obtained.

[0106] As an example, the amount of substance n of lithium element in the first lithium source (Li1) and the amount of substance n of lithium element in the second lithium source (Li2) The ratio can be 1.44, 1.6, 1.8, 2, 2.5, 3, 3.5, 4, etc., or can be a range composed of any of the above values.

[0107] As an example, the temperature of the first constant temperature stage can be 500 °C, 600 °C, 700 °C, 800 °C, etc., or can be a range composed of any of the above values.

[0108] As an example, the temperature of the first sintering can be 800 °C, 900 °C, 1000 °C, etc., or can be a range composed of any of the above values.

[0109] According to some specific embodiments of the present application, the temperature of the first sintering can be 850 °C - 980 °C.

[0110] According to some embodiments of the present application, the time of the first sintering can be 6 h - 12 h. For example, it can be 6 h, 8 h, 10 h, 12 h, etc., or can be a range composed of any of the above values.

[0111] By making the temperature and time of the first sintering within the above ranges, the average particle size and sub - grain size of the sintered cathode active material intermediate product can be within the ranges of this solution, and at the same time, good structural stability and electrical properties can be ensured. If the temperature is too high, over - sintering may occur, leading to an excessive average particle size or sub - grain size; if the temperature is too low, the average particle size may be too small, and even single - crystal materials may not be formed.

[0112] As an example, the temperature of the second constant temperature stage can be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, etc., or can be a range composed of any of the above values.

[0113] S40: Conduct a second sintering on the second intermediate product, where the temperature of the second sintering is less than or equal to the temperature of the first sintering, to obtain the positive electrode active material.

[0114] In this step, the second intermediate product is subjected to a second sintering in an air or oxygen atmosphere. The temperature of the second sintering is less than or equal to the temperature of the first sintering. The time of the second sintering can be 6h - 12h. After the second sintering is completed, it is sieved through a colloid mill or directly sieved to obtain a single-crystalline positive electrode active material.

[0115] According to some embodiments of the present application, the temperature of the second sintering can be 300°C - 800°C. For example, it can be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, etc., or it can be a range composed of any of the above values.

[0116] According to some embodiments of the present application, this step further includes: mixing the second intermediate product with a coating agent containing element M, and using a high-speed mixer for mixing. The stirring speed can be 300rpm - 600rpm, and the stirring time can be 20min - 40min.

[0117] In summary, the positive electrode active material and its preparation method proposed in the present application have the following advantages:

[0118] (1) For the positive electrode active material proposed in the present application, by reducing the change in sub-grain size before and after cycling, the structural stability of the positive electrode active material can be improved, and the cycling performance of the battery under high-temperature conditions can be enhanced.

[0119] (2) By controlling the volume change degree and unit cell change degree of the positive electrode active material, the structural stability of the positive electrode active material is further improved, and the cycling performance of the battery under high-temperature conditions is enhanced.

[0120] (3) By controlling Dv 50 and P 50 of the positive electrode active material, the agglomeration between the positive electrode active material particles can be reduced. During the battery cycling process, the risk of deterioration of the battery high-temperature cycle caused by the exposure of new interfaces due to the dispersion of the agglomerated particles can be reduced. At the same time, the transmission path of lithium ions can be shortened, the kinetic performance of the positive electrode active material can be improved, and the low-temperature performance of the battery can be enhanced.

[0121] (4) For the method of preparing the positive electrode active material proposed in the present application, by controlling the addition method of the lithium source, the sintering process, and the temperature, the structural stability of the positive electrode active material can be improved, the transmission distance of lithium ions can be reduced, and a positive electrode active material with excellent low-temperature and high-temperature performances can be obtained.

[0122] The third aspect of the present application provides a positive electrode plate, which includes the positive electrode active material provided by the first aspect of the present application or the positive electrode active material prepared by the method provided by the second aspect of the present application.

[0123] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material provided by the first aspect of the present application.

[0124] The fourth aspect of the present application provides a battery, which includes the positive electrode plate provided by the third aspect of the present application.

[0125] The shape of the battery can be a cylindrical battery, a square battery, or any other shape of battery, etc. Classified by the outer packaging, the battery can be a hard shell battery, a soft package battery, etc.

[0126] Generally, the battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. Among them, the positive electrode plate, the negative electrode plate, and the separator can be made into an electrode assembly through a winding or lamination process, and the electrode assembly and the electrolyte can be accommodated in the outer packaging. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0127] The positive electrode plate may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode current collector may include a metal foil. For example, the metal foil may be made of aluminum foil. The positive electrode active material may include the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the method described in the second aspect of the present application. The conductive agent may include acetylene black, single-walled carbon nanotubes, and conventional materials in the art. The binder may be polyvinylidene fluoride (PVDF) and conventional materials in the art.

[0128] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a thickener, a conductive agent, and a binder. Among them, the negative electrode current collector may be made of a metal foil. For example, the metal foil may be made of copper foil. The negative electrode active material may include artificial graphite, natural graphite, silicon-containing carbon-based composite materials, lithium-containing metal composite materials, lithium metal materials, and common negative electrode active materials in the art. The thickener may be sodium carboxymethyl cellulose (CMC-Na) and conventional materials in the art. The conductive agent may be acetylene black and conventional materials in the art. The binder may be styrene-butadiene rubber and conventional materials in the art.

[0129] In some embodiments, the separator may be a separator known in the art that can be used in lithium-ion batteries and is stable to the electrolytes used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0130] In the fourth aspect of the present application, an electrical device is proposed, including the lithium-ion battery described in the third aspect of the present application. This electrical device has all the features and advantages of the aforementioned lithium-ion battery, which will not be elaborated here one by one.

[0131] In the fifth aspect of the present application, an electrical equipment is provided, including the battery provided in the fourth aspect of the present application.

[0132] The electrical equipment may include 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, satellites, energy storage systems, etc., but not limited thereto.

[0133] The embodiments of the present application will be described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0134] Example 1

[0135] Preparation of cathode active material

[0136] Mix lithium carbonate as the first lithium source with nickel cobalt manganese hydroxide precursor (Ni 0.6 Co 0.1 Mn 0.3 )(OH)2 and additives ZrO2 (element G1 is Zr), additive Nb2O5 (element G2 is Nb) using a high-speed mixer, where n (Li) :[n (Ni) +n (Co) +n (Mn) :n (G1) :n (G2) =0.72:1:0.003:0.001, the rotation speed of the high-speed mixer is 400 rpm, and mix for 20 min;

[0137] Pre-sinter the mixture in an air atmosphere, heat it up to the sintering temperature of 800 °C at a rate of 2.7 °C / min, and the sintering time is 4 h. Mix the first sintered product with lithium carbonate as the second lithium source, the rotation speed of the high-speed mixer is 400 rpm, and mix for 20 min, where n (Li1) :n (Li2)= 0.72:0.32, and then heated at a rate of 2.7 °C / min to 700 °C in an atmosphere with an oxygen content of over 90% for the first constant temperature section, with a constant temperature time of 3 h. After the heat preservation ended, it was heated at a rate of 2.7 °C / min to 970 °C for the first sintering, and the first sintering constant temperature time was 8 h; then it was continuously cooled at a rate of 2.7 °C / min to 500 °C for the second constant temperature section, with a constant temperature time of 3 h. After that, the sintered material was crushed by a jet mill at a classification wheel speed of 40 Hz to obtain the product of the second process;

[0138] The product of the second process was mixed with coating agent Al2O3 (M1 element is Al), coating agent Co3O4 (M2 element is Co) in a ratio of [n (Ni) + n (Co) + n (Mn) :n (M1) :n (M2) = 1:0.001:0.02 using a high-speed mixer. The rotation speed of the high-speed mixer was 500 rpm, and the mixing time was 30 min; then the second sintering was carried out in an air atmosphere. The temperature of the second sintering was 700 °C, and the time was 9.5 h; after the sintered material was discharged, it was crushed by a colloid mill to obtain the positive electrode active material. The chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0139] Example 2

[0140] The preparation process of the positive electrode active material was the same as that of Example 1, except that the precursor composition was (Ni 0.8 Co 0.1 Mn 0.1 )(OH)2, the second lithium source was lithium hydroxide, n (Li1) :n (Li2) = 0.8:0.23, the first sintering temperature was 900 °C, the constant temperature time was 7 h, the second sintering temperature was 650 °C, and the time was 7 h. The chemical formula of the positive electrode active material is Li 1.03 (Ni 0.78049 Co 0.11707 Mn 0.09756 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0141] Example 3

[0142] The preparation process of the positive electrode active material is the same as that of Example 1, except that the pre-sintering temperature is 550 °C, the time is 5 h, the first sintering temperature is 940 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0143] Example 4

[0144] The preparation process of the positive electrode active material is the same as that of Example 1, except that the first lithium source is lithium hydroxide, the additive containing element G2 is Y2O3, the first sintering temperature is 940 °C, the second-stage constant temperature is 600 °C, the constant temperature time is 4 h, the airflow mill classification is 45 Hz, the coating agent containing element M1 is B2O3, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Y 0.00098 )B 0.00098 O2.

[0145] Example 5

[0146] The preparation process of the positive electrode active material is the same as that of Example 1, except that n (Li1) : n (Li2) = 0.64:0.42, the first sintering temperature is 990 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.000 98 )Al 0.00098 O2.

[0147] Example 6

[0148] The preparation process of the positive electrode active material is the same as that of Example 1, except that the second lithium source is lithium hydroxide, the first sintering temperature is 915 °C, the time is 10 h, the airflow mill classification is 45 Hz, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0149] Example 7

[0150] The preparation process of the positive electrode active material is the same as that in Example 1, except that the pre-sintering temperature is 900 °C, the first sintering temperature is 980 °C, the temperature of the second constant temperature section is 650 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0151] Example 8

[0152] The preparation process of the positive electrode active material is the same as that in Example 1, except that the pre-sintering temperature is 450 °C, n (Li1) : n (Li2) = 0.95:0.09, the temperature of the first constant temperature section is 600 °C, the temperature of the second constant temperature section is 350 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0153] Comparative Example 1

[0154] The preparation process of the positive electrode active material is the same as that in Example 1, except that the temperature of the first constant temperature section is 950 °C, the temperature of the second constant temperature section is 250 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.000 98 )Al 0.00098 O2.

[0155] Comparative Example 2

[0156] The preparation process of the positive electrode active material is the same as that in Example 1, except that the temperature of the first constant temperature section is 400 °C, the temperature of the second constant temperature section is 850 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.000 98 )Al 0.00098 O2.

[0157] Comparative Example 3

[0158] The preparation process of the positive electrode active material is the same as that of Example 1, except that the pre-sintering temperature is 960 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0159] Comparative Example 4

[0160] The preparation process of the positive electrode active material is the same as that of Example 1, except that the pre-sintering temperature is 300 °C, and the chemical formula of the positive electrode active material is Li 1.04 (Ni 0.58537 Co 0.11707 Mn 0.29268 Zr 0.00293 Nb 0.00098 )Al 0.00098 O2.

[0161] The detailed differences between Examples 1 - 8 and Comparative Examples 1 - 4 are shown in Table 1.

[0162]

[0163] Performance Test

[0164] 1. Median volume diameter Dv 50 : Obtained by testing with a laser particle size analyzer of Mastersizer 3000 model from Malvern Corporation.

[0165] 2. Average particle size P 50

[0166] Obtained by testing with a scanning electron microscope of S-4800 model from Hitachi, Japan. The projected area of each single crystal particle in the electron microscope is statistically analyzed, and then its particle size is calculated. The specific method is: the average diameter calculated by converting the projected areas of 500 randomly selected particles in the scanning electron microscope image into standard circles with equal areas, that is, the average particle size P of the single crystal nickel-cobalt-manganese ternary positive electrode active material particles. 50 .

[0167] 3. Ln 10 、Ln 50 、Ln 90 、Ln' 10 、Ln' 50 、Ln' 90, lattice parameter c, lattice parameter a: Tested by Rigaku rotating anode diffractometer Smartlab 9KW, in the range of 10 - 80°, voltage 40 kV, current 200 mA, step 0.02°, scanning time 2° / min. The test results were statistically calculated for the microcrystalline size using the WPPF grain size distribution function of SmartLab Studio II software according to the Fundamental Parameter method (FP method).

[0168] 4. Capacity Test

[0169] The electrochemical performance of CR2025 coin cells was tested using a Shenzhen Neware battery test system. The charge-discharge current density at 0.1C was 100 mA / g. The charge-discharge voltage range was controlled at 3.0V - 4.4V. At room temperature, the coin cells were charge-discharged at 0.1C to evaluate the charge-discharge specific capacity of the single-crystalline nickel cobalt manganese ternary cathode material.

[0170] 5. High-temperature cycle capacity retention rate

[0171] In both the examples and comparative examples, the charge-discharge voltage range was controlled at 3.0V - 4.4V. At a constant temperature of 60°C, the coin cells were charge-discharged at 0.1C for 2 cycles, and then charge-discharged at 1C for 80 cycles to evaluate the high-temperature cycle capacity retention rate of the single-crystalline nickel cobalt manganese ternary cathode material.

[0172] 6. Low-temperature performance test (the test voltage range for all lithium-ion batteries is 3.0 - 4.4V):

[0173] For the -10°C 10% SOC - DCR test, the coin cell was activated by charge-discharging at 1C at 25°C for 1 week, then charged to 10% SOC at 1C and transferred to a -10°C incubator and left to stand for 2 h, and then discharged at a current of 1C for 20 s. -10°C 10% SOC - DCR is (the voltage at the last second of the standing step - the voltage after discharging for 20 s) / discharge current.

[0174] For the -10°C 20% SOC - DCR test, the coin cell was activated by charge-discharging at 1C at 25°C for 1 week, then charged to 20% SOC at 1C and transferred to a -10°C incubator and left to stand for 2 h, and then discharged at a current of 1C for 20 s. -10°C 20% SOC - DCR is (the voltage at the last second of the standing step - the voltage after discharging for 20 s) / discharge current.

[0175] The test results of the positive active materials and batteries in Examples 1 - 8 and Comparative Examples 1 - 4 are shown in Tables 2 and 3.

[0176]

[0177]

[0178] The process of high-temperature cycling of the ternary cathode active material is also a process of continuous charging and discharging. During the charging and discharging process, lithium ions in the cathode active material will continuously intercalate and deintercalate. However, not all the deintercalated lithium can return to its original position, resulting in changes in the arrangement of the lithium layer. Some transition metal ions will also undergo redox reactions during high-temperature cycling, thus changing their valence states, and further leading to changes in the arrangement of the transition metal layer. The above changes in the lithium layer and the transition metal layer will cause changes in the structure of the cathode material, which are manifested as shrinkage or relaxation of the structure at the sub-grain level. Generally, as the number of cycles increases, the changes in the metal layer and the layer spacing will intensify, causing shrinkage of the sub-grain size. Therefore, Ln 50 usually becomes smaller. Ln 10 and Ln 90 will also tend to change towards the size of Ln 50 , that is, it is manifested as a contraction and narrowing of the sub-grain size distribution.

[0179] It can be seen from the comparison between Examples 1-8 and Comparative Examples 1-4 that the battery assembled with the cathode active material prepared in this application has excellent high-temperature performance. It shows that by making the sub-grain size fluctuate within a small range, the structural stability of the material can be significantly improved, the influence on lithium-ion transport caused by structural changes can be reduced, and thus the high-temperature cycling performance of the battery can be improved.

[0180] It can be seen from the comparison between Examples 1-4 and Examples 5 and 6 that by making the average particle size P 50 within the preferred range, the transport path of lithium ions can be shortened, and the kinetic performance of the cathode active material can be improved.

[0181] It can be seen from Examples 1-4 and Examples 5-8 that by controlling the change value of the sub-grain size within the preferred range of this application, and at the same time controlling P 50 and Dv 50 of the cathode active material, a battery with a higher capacity and excellent high-temperature and low-temperature performance can be obtained. It shows that by controlling the change value of the sub-grain size of the cathode active material and P 50 and Dv 50 , the structural stability and kinetic performance of the cathode active material can be improved simultaneously.

[0182] It can be seen from Comparative Example 1 and Comparative Example 2 that if the temperatures of the first constant-temperature section and the second constant-temperature section are not within the ranges defined in this application, the uniformity of the sub-grain size of the finally prepared cathode active material is poor, and the lithium-ion transport is easily blocked, resulting in a lower capacity and poorer high-temperature cycling performance of the battery.

[0183] It can be seen from Comparative Example 3 that if the sintering temperature is too high, the lithium salt directly binds on the surface of the precursor during the pre-sintering stage, advancing the reaction that originally occurred in the first sintering stage to the pre-sintering process. However, only partial lithium salt is added during pre-sintering, resulting in a lack of lithium in the reaction, extremely uneven sub-grain size distribution, and a broadening of the sub-grain size distribution. At the same time, the lithium salt reaction only remains on the surface and does not penetrate into the interior of the precursor. Even when a second lithium source is added subsequently for the first and second constant-temperature stages at appropriate temperatures, the uneven sub-grain size distribution is still not improved, thereby leading to hindered lithium-ion transport and poor electrochemical performance. Since the pre-sintering temperature is high, it is equivalent to extending the time of the first sintering, causing a sharp increase in the average particle size and obvious interface effects, and thus the capacity is also low.

[0184] It can be seen from Comparative Example 4 that due to the low pre-sintering temperature, the lithium salt is difficult to melt and penetrate into the interior of the precursor particles, failing to achieve the purpose of pre-sintering to enable full melting contact between the lithium salt and the precursor. The sub-grain size distribution is relatively wide and the electrical properties are poor. The change rate of c / a is close to the variation law of the sub-grain size. The larger the change value of the sub-grain size, the larger the change value of c / a.

[0185] From Figure 2 and Figure 3 comparison, it can be seen that the positive electrode active material prepared in Example 1 has round and regular particles and good independence. In Comparative Example 2, due to the too low temperature in the first constant-temperature stage and the too high temperature in the second constant-temperature stage, the purpose of enabling the lithium salt to react uniformly with the material is not achieved. It can be clearly seen in the SEM that some particles have become too large, but there are still single-crystal-like materials with incomplete reactions.

[0186] From the attached Figure 4 it can be seen that after the positive electrode active material prepared in Example 1 is assembled into a battery and cycled, the sub-grain size of the 104 crystal plane shifts to the left.

[0187] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode active material, characterized in that: The sub-grain size distribution of the 104 crystal plane of the positive electrode active material satisfies: Among them, ΔLn 10 , ΔLn 50 , ΔLn 90 It is the difference in subgrain size corresponding to the cumulative percentage of Ln volume distribution reaching 10%, 50% and 90% respectively after 80 cycles of the positive electrode active material and before the cycle.

2. The positive electrode active material according to claim 1, characterized in that 3. The positive electrode active material according to claim 1 or 2, characterized in that: Kn' 90 =(Ln' 90 -Ln' 10 ) / Ln' 50 <1.8, optionally, 0.5<Kn' 90 <1.5,Kn 90 =(Ln 90 -Ln 10 ) / Ln 50 , Kn 90 >Kn' 90 , where Ln 10 , Ln 50 , Ln 90 is the sub-grain size corresponding to the cumulative percentage of the volume distribution of the crystal sub-grain size Ln of the positive electrode active material 104 before 80 cycles reaching 10%, 50%, and 90%, respectively, Ln' 10 , Ln' 50 , Ln' 90 The sub-grain sizes correspond to the cumulative percentages of the volume distribution of the crystal plane sub-grain size Ln of the positive electrode active material 104 reaching 10%, 50%, and 90% respectively after 80 cycles.

4. The positive electrode active material according to claim 3, characterized in that (Kn 90 -Kn' 90 ) / Kn 90 <0.25, optionally, 0 < (Kn 90 -Kn' 90 ) / Kn 90 <0.

2.

5. The positive electrode active material according to claim 1 or 2, characterized in that: In the X-ray diffraction pattern of the positive electrode active material, the lattice parameter c and the lattice parameter a satisfy: Δ(c / a) before and after 80 cycles is less than 0.08%; preferably less than 0.06%.

6. The positive electrode active material according to claim 1 or 2, characterized in that: The average particle size of the positive electrode active material particles is P 50 , and satisfy 1μm≤P 50 ≤2.5μm, optionally, 1.3μm≤P 50 ≤2μm.

7. The positive electrode active material according to claim 6, characterized in that The volume distribution median particle size Dv of the positive electrode active material particles 50 Satisfy 2μm≤Dv 50 ≤4.5μm, optionally, 2.5μm≤Dv 50 ≤4μm.

8. The positive electrode active material according to claim 7, characterized in that 1≤Dv 50 / P 50 ≤2.5, optionally, 1.2≤Dv 50 / P 50 ≤2.

5.

9. The positive electrode active material according to claim 1 or 2, characterized in that: It includes the compound shown in Formula Ι: Li 1±a (Ni x Co y Mn z G b )M c O₂ of formula I, Wherein, 0≤a≤0.1, 0≤b≤0.05, 0≤c≤0.05, 0.4≤x<1, 0<y<0.5, 0≤z<0.5, G includes at least one of Zr, Ti, Y, W, Al, Nb, M includes at least one of La, Zr, B, Nb, Ti, W, Si, Mg, Al, Co.

10. The positive electrode active material according to claim 9, characterized in that 0＜b≤0.05。 11. The positive electrode active material according to claim 9, characterized in that The positive electrode active material includes a matrix and a coating material located on at least part of the surface of the matrix, and the coating material includes the M element.

12. A method for preparing the positive electrode active material according to any one of claims 1 to 11, characterized in that: It includes: Mixing a nickel-cobalt-manganese precursor, a first lithium source, and an additive containing a doping element G to obtain a mixture; Pre-sintering the mixture at a temperature of 400°C - 900°C to obtain a first intermediate product; The first process product and the second lithium source are mixed and heated to a first constant temperature section and kept warm, the temperature of the first constant temperature section is 500°C-800°C, after the insulation is completed, the temperature is increased to perform a first sintering of the mixture, the temperature of the first sintering is 800°C-1000°C, after the first sintering is completed, the temperature is lowered to a second constant temperature section, the temperature of the second constant temperature section is 300°C-700°C and kept warm, to obtain a second process product, the amount of lithium element in the first lithium source is n (Li1) The amount of lithium in the second lithium source n (Li2) The ratio is greater than 1.43; Performing a second sintering on the second intermediate product, and the temperature of the second sintering is less than or equal to the temperature of the first sintering to obtain the positive electrode active material.

13. The method according to claim 12, characterized in that When performing the second sintering, mixing the second intermediate product with a coating agent containing the M element.

14. The method according to claim 12, characterized in that The temperature of the second sintering is 300°C - 800°C.

15. The method according to claim 12, characterized in that Satisfying at least one of the following conditions: The pre-sintering time is 3h - 12h; The times of the first sintering and the second sintering are each independently 6h - 12h.

16. The method according to claim 12, characterized in that The additive includes at least one of an oxide containing the G element, a hydroxide containing the G element, and a carbonate containing the G element.

17. A positive electrode plate, characterized in that: It includes the positive electrode active material according to any one of claims 1 - 11 or the positive electrode active material prepared by the method according to any one of claims 12 - 16.

18. A battery, characterized in that: It includes the positive electrode sheet according to claim 17.

19. An electrical equipment, characterized in that: It includes the battery according to claim 18.

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