Positive electrode active material, electrochemical device, and electronic device

Abstract

The present disclosure provides a positive electrode active material, an electrochemical device, and an electronic device. The present disclosure provides a positive electrode active material, comprising: secondary particles formed by primary particles; the secondary particles include an inner part and an outer part covering the inner part; wherein, the ratio of the average particle size of the primary particles in the outer part to the average particle size of the primary particles in the inner part is G, and 1.1 ≤ G ≤ 10, the outer part is the region from the secondary particle interface to the secondary particle surface, and the inner part is the region from the secondary particle interface to the secondary particle center. The positive electrode active material of the present disclosure improves the cycle performance while ensuring the rate performance.

Description

[0001] This application is a divisional application of the application with the application number 202010203415.4, the application date of March 20, 2020, and the invention title of "Positive Electrode Active Material, Electrochemical Device and Electronic Device". Technical Field

[0002] The present disclosure relates to the technical field of lithium batteries, and particularly to a positive electrode active material, an electrochemical device and an electronic device. Background Art

[0003] In recent years, lithium-ion batteries have been widely used in electronic devices such as mobile phones and laptop computers due to their advantages such as high specific energy, high working voltage, and low self-discharge efficiency. The rate performance and cycle performance are important performance indicators of lithium-ion batteries. Therefore, improving the rate performance and cycle performance is crucial for improving the performance of lithium ions. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present disclosure is to provide a positive electrode active material, an electrochemical device and an electronic device. The ratio of the average particle size of the primary particles in the outer part of the positive electrode active material of the present disclosure to the average particle size of the primary particles in the inner part is G, and 1.1 ≤ G ≤ 10, which improves the cycle performance while ensuring the rate performance.

[0005] The present disclosure provides a positive electrode active material, comprising:

[0006] secondary particles formed by primary particles;

[0007] The secondary particles include an inner part and an outer part covering the inner part;

[0008] wherein, the ratio of the average particle size of the primary particles in the outer part to the average particle size of the primary particles in the inner part is G, and 1.1 ≤ G ≤ 10; the outer part is the region from the secondary particle interface to the secondary particle surface, and the inner part is the region from the secondary particle interface to the secondary particle center.

[0009] In the above positive electrode active material, the content of element X in the inner part is greater than the content of element X in the outer part, and element X includes at least one of W, Nb, V or Mo.

[0010] In the above positive electrode active material, the secondary particles satisfy at least one of the conditions (a)-(c):

[0011] (a) The molar ratio of the element X contained in the outer part to the element X contained in the inner part is greater than or equal to 0 and less than or equal to 0.2;

[0012] (b) The molar percentage of the X element in the inner part to the total transition metals in the inner part is between 0.1% and 5%;

[0013] (c) The molar percentage of the X element in the outer part to the total transition metals in the outer part is between 0 and 0.5%.

[0014] In the above positive electrode active material, there is a Y element within a depth of 200 nm from the outer surface of the secondary particle, and the Y element includes at least one of Mg, Ti, or Zr.

[0015] In the above positive electrode active material, the average particle size of the primary particles in the inner part is between 100 nm and 2 μm; and / or the average particle size of the primary particles in the outer part is between 200 nm and 5 μm.

[0016] In the above positive electrode active material, the ratio of the average aspect ratio of the primary particles in the outer part to the average aspect ratio of the primary particles in the inner part is H, and 1 ≤ H ≤ 8.

[0017] In the above positive electrode active material, the average aspect ratio of the primary particles in the inner part is between 1 and 3; and / or the average aspect ratio of the primary particles in the outer part is between 1.5 and 8.

[0018] In the above positive electrode active material, the ratio of the porosity of the inner part to the porosity of the outer part is J, and 2 ≤ J ≤ 20.

[0019] In the above positive electrode active material, the porosity of the inner part is between 5% and 20%; and / or the porosity of the outer part is between 1% and 6%.

[0020] In the above positive electrode active material, the number of primary particles on any diameter of the secondary particle is greater than 5.

[0021] In the above positive electrode active material, the secondary particle includes a compound with the chemical formula Li c Ni 1-a-b-m-n Co a Me b X m Y n O 2-d Z d , where 0.90 ≤ c ≤ 1.10, 0.05 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.1, 0.001 ≤ m ≤ 0.05, 0.001 ≤ n ≤ 0.01, 0 ≤ d ≤ 0.05, and 0.70 < 1 - a - b - m - n < 0.99;

[0022] Among them, Me is at least one element of Mn and Al, X is at least one element of W, Nb, V, and Mo, Y is at least one element of Mg, Ti, and Zr, and Z is at least one element of S, P, and Cl.

[0023] The present disclosure also provides an electrochemical device, comprising:

[0024] a positive electrode;

[0025] a negative electrode;

[0026] a separator disposed between the positive electrode and the negative electrode;

[0027] wherein, the positive electrode comprises the positive electrode active material described in any one of the above.

[0028] The present disclosure also provides an electronic device, characterized in that it comprises the electrochemical device described above.

[0029] For the positive electrode active material provided by the embodiments of the present disclosure, the average particle size of the primary particles in the outer part is larger than the average particle size of the primary particles in the inner part, and the ratio between the two is G and 1.1 ≤ G ≤ 10. While ensuring the capacity and rate performance, the cycle stability of the lithium-ion battery is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Combined with the drawings and referring to the following specific embodiments, the above and other features, advantages and aspects of the embodiments of the present disclosure will become more obvious. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic and the elements and elements are not necessarily drawn to scale.

[0031] Figure 1 is a schematic diagram of a positive electrode active material according to an embodiment of the present disclosure.

[0032] Figure 2 is a flowchart of a preparation method of a positive electrode active material according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The embodiments of the present disclosure will be described in more detail below with reference to the drawings. Although some embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not used to limit the protection scope of the present disclosure.

[0034] The solutions provided by the embodiments of the present application will be described in detail below with reference to the drawings.

[0035] An embodiment of the present disclosure provides a positive electrode active material, comprising: secondary particles formed by primary particles; the secondary particles include an inner part and an outer part covering the inner part; wherein, the ratio of the average particle size of the primary particles in the outer part to the average particle size of the primary particles in the inner part is G, and 1.1 ≤ G ≤ 10; the outer part is the region from the secondary particle interface to the surface of the secondary particle, and the inner part is the region from the secondary particle interface to the center of the secondary particle;

[0036] In an embodiment of the present disclosure, the definition of the secondary particle interface is as follows:

[0037] Find the midpoint of the longest diameter of the secondary particle;

[0038] The line connecting the midpoint of the longest diameter to any point on the surface of the secondary particle is the radius of the secondary particle, and the plane passing through the midpoint of the radius is the interface of the secondary particle.

[0039] For an illustrative example, please refer to Figure 1 , where O is the midpoint of the longest diameter AA' of the shown secondary particle, and a, a', b, b', c, c', d, d', e, e', f, f' are the midpoints on the radii OA, OA', OB, OB', OC, OC', OD, OD', OE, OE', OF, OF' respectively. The plane passing through the midpoints of the above radii is the interface of the secondary particle.

[0040] Specifically, in this embodiment, the positive electrode active material can be the positive electrode material of a lithium-ion battery, for example, it can be a nickel-containing positive electrode material. The secondary particles can be spherical or nearly spherical. To better illustrate the positive electrode active material proposed in this embodiment, an attached Figure 1 is schematically provided in this embodiment. Please refer to Figure 1 , Figure 1 which schematically shows the morphology of a secondary particle. It should be noted that Figure 1 it is only for explanatory purposes and does not impose any limitation on the positive electrode active material in the present disclosure. Figure 1 In it, the secondary particles are formed by quasi-circular primary particles. For example, the secondary particles can be formed by the aggregation of multiple primary particles. Each primary particle has a particle size, and the particle size of the primary particle refers to the longest diameter of the primary particle, which can usually be obtained by statistical analysis using a scanning electron microscope. The average particle size of the primary particles is the average of the particle sizes of each primary particle. In this embodiment, the average particle size of the primary particles in the outer part is greater than the average particle size of the primary particles in the inner part, and the ratio of the two is G and 1.1 ≤ G ≤ 10. Figure 1The definition of the interface is schematically shown. The positive electrode active material proposed in the present disclosure can be used as the positive electrode active material of a lithium-ion battery. In a lithium-ion battery, the particle size of the positive electrode active material will affect the capacity, rate performance, and cycle performance of the lithium-ion battery. In the prior art, methods such as increasing the nickel content and reducing the particle size are often used to increase the capacity. However, when the nickel content is increased to a certain extent, the capacity will no longer increase, and too small a particle size will lead to deterioration of the cycle performance and storage performance.

[0041] For the positive electrode active material proposed in the embodiments of the present disclosure, the primary particle size of the inner part is smaller, and it has a higher specific surface area, which can effectively improve the capacity and rate performance of the lithium-ion battery. However, the smaller particle size is not conducive to the cycle performance of the lithium-ion battery. To improve the cycle performance, in the present disclosure, primary particles with a larger particle size are used in the outer part, thereby ensuring the cycle performance. It should be noted that it is not the case that as long as the average particle size of the outer part is larger than that of the inner part, the above effects can be achieved. When G is less than 1.1, since the average particle size of the outer part is only slightly larger than that of the inner part, the cycle performance cannot be improved. When the average particle size of the outer part is much larger than that of the inner part, that is, when G is greater than 10, due to the too large average particle size of the outer part, the internal resistance will increase, and the overall average particle size of the positive electrode active material will increase, resulting in a decrease in the overall capacity of the positive electrode active material and a decline in the rate performance. Therefore, in this embodiment, 1.1 ≤ G ≤ 10, thereby improving the cycle stability of the lithium-ion battery while ensuring the capacity and rate performance.

[0042] In some embodiments of the present disclosure, the content of element X in the inner part is greater than the content of element X in the outer part, and element X includes at least one of W, Nb, V, or Mo. In this embodiment, W, Nb, V, or Mo as element X can inhibit grain growth. Therefore, when the content of element X in the outer part is lower than that in the inner part, the average particle size of the inner part can be made smaller than that of the outer part. At the same time, by adding element X, the ion conduction rate of the inner part can be increased, thereby improving the capacity and rate performance. In addition, since element X is mainly distributed in the inner part, while improving the rate performance of the inner part, the structural stability of the outer part will not be damaged.

[0043] In some embodiments of the present disclosure, the secondary particles satisfy at least one of the conditions (a)-(c): (a) the molar ratio of the X element contained in the outer portion to the X element contained in the inner portion is greater than or equal to 0 and less than or equal to 0.2; (b) the molar percentage of the X element in the inner portion to the total transition metals in the inner portion is between 0.1% and 5%; (c) the molar percentage of the X element in the outer portion to the total transition metals in the outer portion is between 0 and 0.5%. Specifically, in this embodiment, when condition (a) is satisfied, it indicates that the X element in the outer portion is much less than the X element in the inner portion, and the outer portion may have no X element. The X element can inhibit grain growth. Therefore, when condition (a) is satisfied, it can be ensured that the average particle size of the outer portion is greater than that of the inner portion. When condition (b) or (c) is satisfied, it indicates that the content of the X element accounts for a relatively low proportion of the active transition metal elements, and the properties of the cathode active material itself will not change due to the incorporation of too much X element. For example, the cathode active material in the embodiments of the present disclosure may be a nickel-containing cathode material. By defining the molar percentage of the X element to the transition metal elements, the physical and chemical properties of the nickel-containing cathode material can be ensured to be stable. In the embodiments of the present disclosure, the elemental molar ratio of the cathode active material can be tested by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). For the elemental molar ratio of the inner portion or the outer portion, an EDS Mapping electron probe microanalyzer (EPMA) can be used, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) or X-ray photoelectron spectroscopy (XPS) can also be used for testing.

[0044] In some embodiments of the present disclosure, there is a Y element within a depth of 200 nm from the surface of the secondary particles, and the Y element includes at least one of Mg, Ti, or Zr. Specifically, in this embodiment, the Y element is distributed in the region from the outer surface of the secondary particles inward for 200 nm. Research shows that these Y elements such as Mg, Ti, and Zr can effectively improve the cycling performance of the cathode active material and resist the erosion of the electrolyte, but will have an adverse effect on the capacity of the material. Since the capacity of the cathode active material in this embodiment is mainly ensured by the primary particles in the inner portion, therefore, in this embodiment, the Y element is only added within the near-surface range of the secondary particles to resist the erosion of the electrolyte, so that the cycling performance can be ensured without deteriorating the capacity of the cathode active material.

[0045] In some alternative embodiments, the ratio of the average particle size of the primary particles in the outer portion adjacent to the interface to the average particle size of the primary particles in the inner portion adjacent to the interface is greater than 1.2.

[0046] In some embodiments of the present disclosure, the average particle size of the primary particles in the inner part is between 100 nm and 2 μm; and / or, the average particle size of the primary particles in the outer part is between 200 nm and 5 μm. Reducing the particle size can improve the capacity of the cathode active material. Therefore, by limiting the range of the average particle size of the primary particles in the inner part, the capacity of the cathode active material can be ensured. At the same time, if the average particle size of the particles in the outer part is too large, it will cause an increase in the overall particle size of the cathode active material, resulting in adverse effects such as a decrease in the overall capacity of the cathode active material and an increase in the internal resistance. Therefore, it is necessary to limit the range of the average particle size of the outer part.

[0047] In some embodiments of the present disclosure, the ratio of the average aspect ratio of the primary particles in the outer part to the average aspect ratio of the primary particles in the inner part is H, and 1 ≤ H ≤ 8. Specifically, in this embodiment, the aspect ratio is D1 / D2, where D1 is the longest diameter of the primary particle, and D2 is the longest diameter among all the diameters perpendicular to the longest diameter of the primary particle. The aspect ratio can be measured and statistically analyzed using a high-magnification SEM-CP image. The aspect ratio reflects the similarity of the primary particle to a sphere, and the aspect ratio of a sphere is 1. Therefore, the primary particles in the outer part differ more from a sphere compared to the primary particles in the inner part. The specific surface area of a sphere is the smallest. By making the outer part non-circular, the primary particles in the outer part can provide a larger reaction surface, thereby improving the rate performance of the outer part and compensating for the adverse effects of large particle size on the rate performance.

[0048] In some embodiments of the present disclosure, the average aspect ratio of the primary particles in the inner part is between 1 and 3; and / or, the average aspect ratio of the primary particles in the outer part is between 1.5 and 8. In this embodiment, by limiting the aspect ratio of the primary particles in the inner part, it is ensured that the primary particles in the inner part are approximately circular, reducing the contact area between the inner part and the electrolyte, and reducing the erosion of the electrolyte on the inner part, thereby preventing the cycling performance of the inner part from deteriorating. By limiting the aspect ratio of the outer part, the primary particles in the outer part can provide a larger reaction surface, improving the rate performance of the outer part.

[0049] In some embodiments of the present disclosure, the ratio of the porosity of the inner part to the porosity of the outer part is J, and 2 ≤ J ≤ 20. The porosity refers to the ratio of the pore area to the total area. It can be obtained by processing a high-magnification SEM image of the cathode active material using image processing software Photoshop (PS). The processing steps are as follows:

[0050] a) Load the SEM image into PS;

[0051] b) Select the magnetic lasso tool to select the part to be measured;

[0052] c) Select "Color Range" in "Select", select "Grayscale" for the selection preview and select "Shadows";

[0053] d) Select "Histogram" in "Window" and record the pixels of the pores in the expanded view;

[0054] c) Select the magnetic lasso again to select the part to be measured and record the pixels;

[0055] d) Divide to obtain the porosity.

[0056] In some embodiments of the present disclosure, the porosity of the inner part is significantly higher than that of the outer part, indicating that the inner part is in a porous state. This is because the primary particle growth of the inner part is incomplete, while the primary particles of the outer part are fully grown. Optionally, the porosity of the inner part is 5%-20%; and / or the porosity of the outer part is 1%-6%.

[0057] In some embodiments of the present disclosure, the number of primary particles on any diameter of the secondary particles is greater than 5. Optionally, the number of primary particles on any diameter of the secondary particles is 10 to 20.

[0058] In some embodiments of the present disclosure, the secondary particles include a compound of the chemical formula Li c Ni 1-a-b-m-n Co a Me b X m Y n O 2-d Z d , where 0.90 ≤ c ≤ 1.10, 0.05 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.1, 0.001 ≤ m ≤ 0.05, 0.001 ≤ n ≤ 0.02, 0 ≤ d ≤ 0.05, and 0.70 < 1 - a - b - m - n < 0.99; wherein, Me is at least one element of Mn and Al, X is at least one element of W, Nb, V, and Mo, Y is at least one element of Mg, Ti, and Zr, and Z is at least one element of S, P, and Cl. In some alternative embodiments, 2 ≤ m / n ≤ 50.

[0059] In some embodiments of the present disclosure, the difference between the average lithium layer spacing corresponding to the crystal plane of the primary particles (003) in the inner part and the average lithium layer spacing corresponding to the crystal plane of the primary particles (003) in the outer part is K, This is because the content of element X in the inner part is higher than that in the outer part, resulting in lattice expansion. The larger the average lithium layer corresponding to the (003) crystal plane, the better the rate performance. In some embodiments, the average lithium layer spacing corresponding to the (003) crystal plane of the primary particles in the inner part can be measured by a transmission electron microscope. In some embodiments, the average lithium layer spacing corresponding to the (003) crystal plane of the primary particles in the inner part is ; in some embodiments, the average lithium layer spacing corresponding to the crystal plane of the primary particles (003) in the outer part is between ; in some embodiments, the unit cell parameters of the positive electrode active material are

[0060] In some embodiments of the present disclosure, the average particle size of the primary particles in the inner part is relatively small, and the average particle size of the primary particles in the outer part is relatively large, which can be achieved by adding X elements such as W, Nb, and Mo to the inner part to inhibit grain growth. By controlling the particle sizes of the primary particles in the inner part and the outer part, the capacity and rate performance of the positive electrode active material can be improved. Making the primary particles in the inner part smaller can effectively improve the capacity and rate performance, while making the primary particles in the outer part larger can prevent the cycling performance from deteriorating. Since the X element mainly exists in the inner part, while improving the rate performance of the inner part, the structural stability of the outer surface of the positive electrode active material will not be damaged.

[0061] At the same time, in order to ensure the cycling performance, adding Y elements such as Mg, Ti, and Zr to the positive electrode active material can effectively improve the cycling performance of the positive electrode active material, but the Y element will deteriorate the capacity and rate to some extent. Therefore, in some embodiments, the Y element is added only near the surface of the secondary particles to resist the erosion of the electrolyte, and at the same time, the capacity and rate performance can be minimized.

[0062] To better illustrate the positive electrode active material proposed in the embodiments of the present disclosure, the following will be described in conjunction with Examples 1-26 and Comparative Examples 1-2. For the positive electrode active materials in Examples 1-26 and Comparative Examples 1-2, one or more of particle size testing, electrical property testing, and XRD testing will be performed. The testing methods for each test will be described first below.

[0063] (1) Particle size testing

[0064] The particle size of the samples in Examples 1-26 and Comparative Examples 1-2 refers to the Dv50 value measured by laser particle size. The particle size testing is to analyze the particle size of the samples using a Mastersizer 2000 laser particle size distribution tester. The injection system is Hydro2000SM wet dispersion, the range is 0.01um - 3500um, the light source is Red light: Helium neon laser / blue light: Solid state light source, and the detection angle is 0 - 144°. The sample testing time is 6s, the background testing time is 6s, the number of sample testing snaps is 6000 times, the test cycle is 3 times and the average value is taken, the stirring pump speed is 3000rpm, and the analysis mode is set to General purpose.

[0065] (2) Electrical performance test

[0066] The prepared lithium-ion battery was left standing for about 2 hours at a test temperature of about 25°C, then the lithium-ion battery was charged at a constant current of about 1.5C to about 4.25V, and then charged at a constant voltage of about 4.25V to about 0.02C, and left standing for about 15 minutes; then the lithium-ion battery was discharged at a constant current of 0.1C to about 2.8V and left standing for about 30 minutes. After repeating the above steps 3 times, the lithium-ion battery was charged at a constant current of 1.5C to about 4.25V, and then charged at a constant voltage of about 4.25V to about 0.02C, and left standing for about 15 minutes; then the lithium-ion battery was discharged at a constant current of 5C to about 2.8V and left standing for about 30 minutes; after completing the above charge and discharge process, the discharge capacity of the lithium-ion battery at different rates was measured.

[0067] The 0.1C discharge capacity in the following examples refers to the capacity of the first cycle discharged at 0.1C, and the 5C / 0.1C capacity retention rate = (5C first cycle discharge capacity / 0.1C first cycle discharge capacity) × 100%

[0068] The tested lithium-ion battery was left standing for about 2 hours at a test temperature of about 25°C, then the lithium-ion battery was charged at a constant current of about 1C to about 4.2V, and then charged at a constant voltage of about 4.2V to about 0.02C, and left standing for about 15 minutes; then the lithium-ion battery was discharged at a constant current of about 4C to about 2.8V and left standing for about 30 minutes, and the capacity at this time was recorded as the first cycle discharge capacity. The above process was repeated 500 times and the discharge capacity at this time was recorded as the 500th cycle discharge capacity. The capacity retention rate of the 500th cycle of the lithium-ion battery was calculated by the following formula:

[0069] Capacity retention rate of the 500th cycle = (500th cycle discharge capacity / first cycle discharge capacity) × 100%

[0070] (3) Unit cell parameter test

[0071] In the following examples, the unit cell parameters were obtained by X-ray diffraction analysis (XRD). An X-ray diffractometer of the X’Pert Pro type from Philips was used, with a Cu target Kα radiation source (λ = 0.15418 nm), a Ni filter, a scanning speed of 1° min-1, and a scanning range of 10 - 120°. The GSAS / EXPGUI software was used to calculate the unit cell parameters of the positive electrode active material.

[0072] The following describes Examples 1 - 8 and Comparative Examples 1 - 2.

[0073] Preparation of the positive electrode active material in Examples 1 - 8: First, NiSO 4·6H 2 O, CoSO 4 ·7H 2 O, WO 3 Prepare a suspension according to the molar ratio of Ni:Co:W = 0.90:0.097:0.003, prepare an alkali solution with NaOH, and prepare an ammonia solution with NH 3 ·H 2 O. Add the three solutions of salt, alkali, and ammonia into the reaction kettle simultaneously. Control the reaction stirring speed at 1300 rpm, and control the temperature at 52 ± 2 °C through the jacket oil bath. Adjust the pH to 11.2 by controlling the amount of ammonia water added. After the first reaction duration T1, add the mixed salt solution of NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, with a molar ratio of Ni:Co = 0.9:0.1. At this stage, control the stirring speed at 800 rpm, adjust the pH to 11.7, and after the second reaction duration T2, filter, wash, and dry the slurry to obtain the precursor of the cathode material. Mix the precursor with LiOH according to Li / (Ni+Co+W) = 1.05, and sinter at 780 °C for 18 h to obtain the first sintered product; then mix the first sintered product and ZrO 2 Mix according to Zr / (Ni+Co+W) = 0.002 and heat-treat at 650 °C for 12 h to obtain the cathode active material.

[0074] Among them, different T1 and T2 are adopted in Examples 1 - 8, as shown in Table 1 specifically.

[0075] Table 1

[0076]

[0077] Preparation of the cathode active material in Comparative Example 1: Prepare a suspension according to Ni:Co:Mn = 0.8:0.1:0.1 with NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 Prepare an alkali solution with NaOH, and prepare an ammonia solution with NH 3 ·H 2 O. Add the three solutions of salt, alkali, and ammonia into the reaction kettle simultaneously. Control the reaction stirring speed at 800 rpm, and control the temperature at 52 ± 2 °C through the jacket oil bath. Adjust the pH to 11.5 by controlling the amount of ammonia water added. After reacting for 24 h, filter, wash, and dry the slurry to obtain the precursor of the cathode material. Mix the precursor with LiOH, and sinter at 780 °C for 18 h to obtain the first sintered product; then mix the first sintered product and Al 2 O3 After mixing in a stoichiometric ratio, the positive electrode active material was obtained by heat treatment at 600 °C for 6 h.

[0078] Preparation of the positive electrode active material in Comparative Example 2: NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 were made into a suspension according to Ni:Co:Mn = 0.8:0.1:0.1, NaOH was made into an alkaline solution, and NH 3 ·H 2 O was made into an ammonia solution. The three solutions of salt, alkali, and ammonia were simultaneously added to the reaction kettle. The reaction stirring speed was controlled at 800 rpm, and the temperature was controlled online at 52 ± 2 °C through a jacket oil bath. The pH was adjusted to 11.5 by controlling the amount of ammonia water added. After reacting for 24 h, the slurry was filtered, washed, and dried to obtain the precursor of the positive electrode material. The precursor was mixed with LiOH and WO 3 , and then sintered at 780 °C for 18 h to obtain a first-fired product; then the first-fired product and Al 2 O 3 were mixed in a stoichiometric ratio and heat-treated at 600 °C for 6 h to obtain the positive electrode active material.

[0079] The test results of Examples 1-8 and Comparative Examples 1-2 are shown in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] As can be seen from Table 2, by adjusting the first duration T1 and the second duration T2, the average particle size and the ratio G of the primary particles of the inner part and the outer part are changed. As shown in Table 2, from the test results of Examples 1 and 3, it can be seen that when the second duration T2 is the same, the longer the first duration T1, the larger the average particle size of the primary particles in the inner part. From Examples 2-6, it can be seen that as the second duration T2 increases, the average particle size of the primary particles in the inner part increases slightly, while the average particle size of the primary particles in the outer part increases significantly. That is, the second duration will affect the average particle size of the primary particles in the inner part and the outer part, and the influence on the primary particles in the outer part is more obvious.

[0084] The capacity retention rate of Examples 1-8 after 500 cycles was significantly higher than that of Comparative Example 1 and Comparative Example 2. In Examples 1-8, G>1, while in Comparative Example 1 and Comparative Example 2, G<1. Thus, it can be seen that by making the average particle size of the primary particles in the outer part larger than that of the primary particles in the inner part, the cycle performance can be significantly improved.

[0085] When G>1 is satisfied, from the perspective of the 500-cycle capacity retention rate of Examples 1-8, the 500-cycle capacity retention rate of Examples 6-8 is significantly higher than that of Examples 1-5. This is because the average particle size of the primary particles in the outer part of Examples 6-8 is larger, and a larger average particle size of the primary particles is beneficial to improving the cycle performance. However, the 500-cycle capacity retention rate and the initial discharge capacity of Example 6 have significantly started to deteriorate, which is due to the influence of excessive G. Therefore, in the examples of the present disclosure, 1.1≤G≤10 is defined.

[0086] From the perspective of the initial discharge capacity of Examples 1-8 and the capacity retention rate of 5C / 0.2C at -10°C, both the initial discharge capacity of Example 8 and the capacity retention rate of 5C / 0.2C at -10°C are lower than those of Examples 1-7. This is because the average particle size of the primary particles in the inner part and the average particle size of the primary particles in the outer part of Example 8 are larger. Larger primary particles lead to capacity attenuation and also cause a decrease in rate performance. Therefore, in the examples of the present disclosure, it is preferably set that the average particle size of the primary particles in the inner part is between 100 nm and 2 μm, and the average particle size of the primary particles in the outer part is between 200 nm and 5 μm.

[0087] Examples 9-19 are described below.

[0088] Preparation of the positive electrode active material in Example 9: First, NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, and WO 3 were prepared into a suspension according to Ni:Co:W = 0.80:0.197:0.003. NaOH was prepared into an alkaline solution, and NH 3 ·H 2 O was prepared into an ammonia solution. The three solutions of salt, alkali, and ammonia were simultaneously added to the reaction kettle. The reaction stirring speed was controlled at 1300 rpm, and the temperature was controlled online at 52±2°C through a jacket oil bath. By controlling the amount of ammonia water added, the pH was adjusted to 11.2. After reacting for 10 min, NiSO 4 ·6H 2 O and CoSO 4 ·7H 2A mixed salt solution of O with a stoichiometric ratio of Ni:Co = 0.8:0.2. At this stage, the stirring speed is controlled at 800 rpm, the pH is adjusted to 11.7, and after reacting for 20 h, the slurry is filtered, washed, and dried to obtain the precursor of the cathode material. The precursor and LiOH are mixed at Li / (Ni + Co + W) = 1.05 and sintered at 780 °C for 18 h to obtain a first-fired product; then the first-fired product and ZrO 2 are mixed at Zr / (Ni + Co + W) = 0.002 and heat-treated at 650 °C for 12 h to obtain the cathode active material.

[0089] The difference between the preparation of the cathode active material in Example 10 and that in Example 9 is only that the raw material WO 3 is replaced with Nb 2 O 5 .

[0090] The difference between the preparation of the cathode active material in Example 11 and that in Example 9 is only that the raw material WO 3 is replaced with MoO 3 .

[0091] The difference between the preparation of the cathode active material in Example 12 and that in Example 9 is only that the raw material WO 3 is replaced with V 2 O 5 .

[0092] The difference between the preparation of the cathode active material in Example 13 and that in Example 9 is only that the raw material WO 3 is replaced with WO 3 and Nb 2 O 5 .

[0093] The difference between the preparation of the cathode active material in Example 14 and that in Example 9 is only that the raw material WO 3 is replaced with Nb 2 O 5 and MoO 3 .

[0094] The difference between the preparation of the cathode active material in Example 15 and that in Example 9 is only that the raw material WO 3 is replaced with WO 3 , MoO 3 and V 2 O 5 .

[0095] The difference between the preparation of the cathode active material in Example 16 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.199:0.001.

[0096] The difference between the preparation of the cathode active material in Example 17 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.195:0.005.

[0097] The difference between the preparation of the cathode active material in Example 18 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.192:0.008.

[0098] The difference between the preparation of the cathode active material in Example 196 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.19:0.01.

[0099] The difference between the preparation of the cathode active material in Example 20 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.18:0.02.

[0100] The difference between the preparation of the cathode active material in Example 21 and that in Example 9 is only that Ni:Co:W = 0.80:0.197:0.003 is replaced by Ni:Co:W = 0.80:0.15:0.05.

[0101] Different X elements or different amounts of X element are incorporated in Examples 9 - 21, and the test results of Examples 9 - 21 are shown in Table 3.

[0102] Table 3

[0103]

[0104] As shown in Table 3, it can be seen from the test results of Examples 9 - 15 that the lattice spacing of the inner part (003) depends on the type of X element. The atomic radii of W, Nb, Mo, and V are similar. Therefore, after the same amount of X element is incorporated into the inner part, the lattice spacing of the inner part (003) is similar. Thus, there is basically no difference in the lattice spacing of the inner part (003) in Examples 9 - 15. It can be seen from the test results of Examples 16 - 18 that as the content of W incorporated into the inner part increases, the lattice spacing of the inner part (003) gradually increases. This is because the incorporation of the W element causes lattice expansion, and the greater the incorporation amount, the greater the lattice expansion.

[0105] The electrochemical performance of Examples 9 - 21 is shown in Table 4. It can be seen that the initial discharge capacity and 5C / 0.2C rate performance of the material are significantly improved as the lattice spacing increases. However, with the increase of the X element, the primary particle size decreases to a certain extent, resulting in a slight decrease in the cycle retention rate. In addition, with the increase of the X element content, the primary particles tend to be refined, but when the X element content is greater than 0.5%, the change is not obvious. The discharge capacity and rate also increase to a certain extent with the refinement of the particles.

[0106] Table 4

[0107]

[0108] The following describes Examples 22 - 28.

[0109] Preparation of the cathode active material for Examples 20 - 26: NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, and WO 3 were made into a suspension according to Ni:Co:W = 0.90:0.097:0.003, NaOH was made into an alkaline solution, and NH 3 ·H 2 O was made into an ammonia solution. The three solutions of salt, alkali, and ammonia were simultaneously added to the reaction kettle. The reaction stirring speed was controlled at r1 rpm, and the temperature was controlled online at 52 ± 2°C through a jacket oil bath. The pH was adjusted to pH1 by controlling the amount of ammonia water added. After reacting for 10 min, NiSO 4 ·6H 2 O and CoSO 4 ·7H 2A mixed salt solution of O with a stoichiometric ratio of Ni:Co = 0.9:0.1. At this stage, the stirring speed is controlled at r2 rpm, the pH is adjusted to pH2, and after reacting for T2, the slurry is filtered, washed, and dried to obtain the precursor of the cathode material. After mixing the precursor with LiOH, it is sintered at 780 °C for 18 h to obtain the first sintered product; then the first sintered product and ZrO 2 After mixing according to Zr / (Ni + Co + W) = 0.002 and heat-treating at 650 °C for 12 h, the finished product is obtained.

[0110] The differences between Examples 22 - 28 lie in the use of different pH1, pH2, r1, r2, and T2. The pH1, pH2, r1, r2, and T2 of Examples 22 - 28 are shown in Table 5.

[0111] Table 5

[0112] Serial number pH1 r1 pH2 r2 T2 Example 22 11.0 1500 11.7 1000 22 Example 23 11.0 1500 11.9 800 22 Example 24 11.0 1500 12.3 800 22 Example 25 11.0 1500 12.5 800 22 Example 26 11.2 1200 11.5 900 27 Example 27 11.4 1200 11.5 900 27 Example 28 11.5 1200 11.5 900 27

[0113] The test results of Examples 22 - 28 are shown in Table 6.

[0114] Table 6

[0115]

[0116]

[0117] As shown in Table 5 and Table 6, it can be seen from Examples 22 - 25 that by increasing pH2, the aspect ratio of the primary particles in the outer part can be significantly increased, and the porosity of the outer part can be increased. It can be seen from Examples 26 - 28 that by increasing pH1, the aspect ratio of the primary particles in the inner part and the aspect ratio of the primary particles in the outer part can be increased, and at the same time, the porosity of the inner part can be increased.

[0118] Table 7 gives the electrical performance test results of Examples 22 - 28. It can be found from Examples 22 - 25 that with the increase of the external porosity and the aspect ratio of the primary particle size, the rate performance and discharge capacity of the particles have been significantly improved, while the cycle retention rate has decreased to a certain extent. This is because with the increase of the external pores, the lithium-ion transport channels increase, the rate and capacity increase, and on the other hand, the side reactions with the electrolyte also increase, resulting in a certain decrease in the cycle; it can be found from Examples 26 - 28 that with the increase of the internal porosity and the aspect ratio of the primary particle size, the initial discharge capacity and the 5C / 0.2C capacity retention rate also increase to a certain extent, but the cycle capacity retention rate basically does not deteriorate. This is because the electrolyte forms a SEI (solid electrolyte interface) film on the surface particles, delaying the erosion of the internal particles.

[0119] Table 7

[0120]

[0121] Examples 29 to 33 present the cases of different Y element doping.

[0122] Preparation of the positive electrode active material: First, NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, and WO 3 are prepared into a suspension according to the molar ratio of Ni:Co:W = 0.90:0.097:0.003. NaOH is prepared into an alkaline solution, and NH 3 ·H 2 O is prepared into an ammonia solution. The three solutions of salt, alkali, and ammonia are simultaneously added to the reaction kettle. The reaction stirring speed is controlled at 1300 rpm, and the temperature is controlled online at 52 ± 2 °C through a jacket oil bath. By controlling the amount of ammonia water added, the pH is adjusted to 11.2. After the first reaction duration T1, NiSO 4 ·6H 2 O and CoSO 4 ·7H 2 O mixed salt solution are added, and the molar stoichiometric ratio is Ni:Co = 0.90:0.1. At this stage, the stirring speed is controlled at 800 rpm, the pH is adjusted to 11.7, and after the second reaction duration T2, the slurry is filtered, washed, and dried to obtain the precursor of the positive electrode material. The precursor and LiOH are mixed according to Li / (Ni + Co + W) = 1.05 and sintered at 780 °C for 18 h to obtain a first-fired product; then, the first-fired product and the oxide of Y (the oxide of Zr is ZrO2, the oxide of Mg is MgO, and the oxide of Ti is ZrO2) are mixed according to the stoichiometric ratio Y / (Ni + Co + W) = n and heat-treated at 650 °C for 12 h to obtain the positive electrode active material.

[0123] Table 8 shows the types and contents of different Y elements and the corresponding electrochemical performances. It can be seen from Examples 29 to 32 that as the content of the Zr element increases, both the capacity and the rate decrease significantly, while the cycle performance improves significantly. Examples 33 to 35 are the cases of co-doping of several Y elements, and it is found that the performance is not much different from that of single Zr doping.

[0124] Table 8

[0125]

[0126] An electrochemical device is also proposed in the embodiments of the present disclosure, including: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; wherein, the positive electrode includes the positive electrode active material of any one proposed in the present disclosure.

[0127] A conductive agent or a binder may be added to the positive electrode or the negative electrode of the above-mentioned electrochemical device. The conductive agent may include one or a combination of several of conductive carbon black, flake graphite, graphene, and carbon nanotubes. The binder may include one or a combination of several of polyvinylidene fluoride, copolymer of vinylidene fluoride - hexafluoropropylene, styrene - acrylate copolymer, styrene - butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. In some embodiments, the separator includes one or a combination of several of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, and aramid. For example, polyethylene includes one or a combination of several selected from high - density polyethylene, low - density polyethylene, and ultra - high - molecular - weight polyethylene. In particular, polyethylene and polypropylene have a good effect on preventing short - circuit and can improve the stability of the battery through the shut - off effect.

[0128] In some embodiments, the surface of the separator may further include a porous layer. The porous layer is disposed on at least one surface of the separator. The porous layer includes inorganic particles and a binder. The inorganic particles are selected from aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), cerium dioxide (CeO 2 ), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, and one or a combination of several thereof. The binder is selected from one or a combination of several of polyvinylidene fluoride, copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The porous layer on the surface of the separator can improve the heat - resistance performance, antioxidant performance, and electrolyte infiltration performance of the separator, and enhance the adhesion between the separator and the electrode sheet.

[0129] In some embodiments, the electrochemical device further includes an electrolyte, which includes at least two of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP). In addition, the electrolyte may additionally include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and dinitrile compound as an electrolyte additive.

[0130] In some embodiments of the present disclosure, the positive electrode active material further includes a carbon material, which may be at least one of graphene, carbon nanotubes, carbon fibers, or carbon black. Among them, the aspect ratio of the carbon nanotubes may be 500 - 100000. The mass ratio of the carbon nanotubes to the mass of the positive electrode active material is 0.2% - 2%.

[0131] In some embodiments of the present disclosure, the graphitization degree of the negative electrode is between 94% and 96%, and the Id / Ig in the Raman test of the negative electrode should be between 0.02 and 0.6. In some embodiments of the present disclosure, the electrolyte has a fluorinated chain ester with a fluorine content between 40% and 80%, and the mass ratio of the fluorinated chain ester to the mass of the electrolyte is less than or equal to 30%

[0132] Embodiments of the present disclosure also propose an electronic device, including the electrochemical device proposed by the present disclosure. For example, the electronic device includes a mobile phone containing a lithium-ion battery.

[0133] Embodiments of the present disclosure also propose a preparation method of a positive electrode active material. Please refer to Figure 2 , and the preparation method includes:

[0134] S11: Configure a salt solution or suspension with an Ni source, a Co source, and an X source in a first ratio, add a precipitating agent and a buffering agent to the salt solution or suspension, and react for a first period of time;

[0135] Specifically, the precipitating agent may be an alkali solution, such as NaOH. Optionally, the molar ratio of the Ni source, the Co source, and the X source is: (0.7 - 0.99):(0.05 - 0.2):(0.01 - 0.05). Optionally, the first period of time is 10 min - 2 h.

[0136] S12: After reacting for the first period of time, add a solution containing Ni and Co and react for a second period of time to obtain a precipitate;

[0137] Optionally, the second period of time is 15 h - 30 h;

[0138] S13: Dry the precipitate to obtain a precursor, mix the precursor and a lithium source in a second ratio, and heat-treat at a first temperature for a third period of time to obtain a first fired product;

[0139] Optionally, the first temperature is 750°C - 850°C, and the third duration is 14h - 24h; optionally, the molar ratio of the lithium source to the precursor is the second ratio, and the second ratio is 1.01 - 1.15.

[0140] S14: Mix the first calcined product with the Y source in the third ratio, and heat-treat for the fourth duration at the second temperature to obtain the cathode active material.

[0141] Specifically, the molar ratio of the first calcined product to the Y source is the third ratio, and the third ratio is (1 - n):n, where 0.001 ≤ n ≤ 0.02. Optionally, the second temperature is 500°C - 650°C, and the fourth duration is 10h - 16h. In some embodiments, in order to add Y elements within the near-surface range of the cathode active material, the second temperature is lower than the crystallization temperature of the cathode active material.

[0142] In the above-described embodiments of the preparation method, the content of the X element and the first duration will both affect the size, aspect ratio, and porosity of the primary particles in the inner part. The higher the content of the X element and the shorter the first duration, the smaller the primary particles in the inner part, the smaller the aspect ratio, and the larger the porosity. And the lattice spacing corresponding to the (003) plane of the primary particles in the inner part is only affected by the content of the X element. The second duration mainly affects the size and aspect ratio of the primary particles in the outer part, and the longer the second duration, the larger the primary particles in the outer part and the larger the aspect ratio. In addition, in this solution, the pH value and the rotation speed also have a greater impact on the aspect ratio of the primary particles. The greater the pH value and the smaller the rotation speed, the larger the aspect ratio of the primary particles. Therefore, in some embodiments of the present disclosure, in order to control the aspect ratio of the primary particles, during the reaction for the first duration by adding a precipitant and a buffer to the salt solution or suspension, control the pH to 11.0 - 11.5 and stir at a rotation speed of 1200 rpm - 1500 rpm. In some embodiments, during the reaction for the second duration by adding a mixed salt solution containing Ni and Co, control the pH to 11.5 - 12.5 and stir at a rotation speed of 800 rpm - 1000 rpm.

[0143] In some embodiments of the present disclosure, the above preparation method further includes: coating the surface of the active material with an oxide of at least one component of Al, Zr, Mg, and B.

[0144] The above description is only for the preferred embodiments of the present disclosure and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosure concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present disclosure.

[0145] Moreover, although the operations are depicted in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in a sequential order. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the foregoing description, these should not be construed as limitations on the scope of the present disclosure. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments.

[0146] Although the subject matter has been described in language specific to structural features and / or methodological acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are merely example forms of implementing the claims.

Claims

1. A positive electrode active material, characterized in that, it comprises: secondary particles formed by primary particles; the secondary particles include an inner part and an outer part covering the inner part; wherein, the ratio of the average particle size of the primary particles in the outer part to the average particle size of the primary particles in the inner part is G, and 1.1 ≤ G ≤ 10; the outer part is the region from the secondary particle interface to the secondary particle surface, the inner part is the region from the secondary particle interface to the secondary particle center, the connection line from the midpoint of the longest diameter of the secondary particle to any point on the secondary particle surface is the radius of the secondary particle, and the plane passing through the radius midpoint is the interface of the secondary particle; the secondary particles include nickel-containing lithium cobalt oxide.

2. The positive electrode active material according to claim 1, characterized in that, the molar percentage content of element X in the inner part is greater than the molar percentage content of element X in the outer part, and the element X includes at least one of W, Nb, V or Mo.

3. The positive electrode active material according to claim 2, characterized in that, the secondary particles satisfy at least one of the conditions (a)-(c): (a) The molar ratio of the element X contained in the outer part to the element X contained in the inner part is greater than or equal to 0 and less than or equal to 0.2; (b) The molar percentage of element X in the inner part to the total transition metals in the inner part is between 0.1% - 5%; (c) The molar percentage of element X in the outer part to the total transition metals in the outer part is between 0 - 0.5%.

4. The positive electrode active material according to claim 1, characterized in that, element Y is present within a depth of 200 nm from the secondary particle surface, and the element Y includes at least one of Mg, Ti or Zr.

5. The positive electrode active material according to claim 1, characterized in that, the average particle size of the primary particles in the inner part is between 100 nm - 2 μm; and / or the average particle size of the primary particles in the outer part is between 200 nm - 5 μm.

6. The positive electrode active material according to claim 1, characterized in that, the ratio of the average aspect ratio of the primary particles in the outer part to the average aspect ratio of the primary particles in the inner part is H, and 1 ≤ H ≤ 8.

7. The positive electrode active material according to claim 1, characterized in that, the average aspect ratio of the primary particles in the inner part is between 1 - 3; and / or the average aspect ratio of the primary particles in the outer part is between 1.5 - 8.

8. The positive electrode active material according to claim 1, characterized in that, the ratio of the porosity of the inner part to the porosity of the outer part is J, 2 ≤ J ≤ 20.

9. The positive electrode active material according to claim 1, characterized in that, the porosity of the inner part is 5% - 20%; and / or the porosity of the outer part is 1% - 6%.

10. The positive electrode active material according to claim 1, characterized in that, the number of primary particles on any diameter of the secondary particles is greater than 5.

11. The positive electrode active material according to claim 1, wherein, The secondary particles include a compound with the chemical formula Li c Ni 1-a-b-m-n Co a Me b X m Y n O 2-d Z d , where 0.90 ≤ c ≤ 1.10, 0.05 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.1, 0.001 ≤ m ≤ 0.05, 0.001 ≤ n ≤ 0.02, 0 ≤ d ≤ 0.05, and 0.70 < 1 - a - b - m - n < 0.99; Me is at least one element of Mn and Al, X is at least one element of W, Nb, V, and Mo, Y is at least one element of Mg, Ti, and Zr, and Z is at least one element of S, P, and Cl.

12. An electrochemical device, characterized in that, comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; wherein, the positive electrode comprises the positive electrode active material according to any one of claims 1-11.

13. An electronic device, characterized in that, comprising the electrochemical device according to claim 12.

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