A single-crystal low-cobalt ternary material, a preparation method thereof, a secondary battery, a battery pack, and an electric device

Abstract

The application relates to a low-cobalt ternary positive electrode material with a single crystal structure, which has a chemical formula of Li 1+x (Ni a Co b Mn c ) 1‑d M d O 2‑y A y , wherein the molar fraction of Co elements is low, 0.05<=b<=0.14; and in a single particle, the ratio between the average Co content per unit area of the outer layer and the average Co content per unit area of the core on the cross section passing through the geometric center of the particle is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1. The material has better structural stability and kinetic properties at low temperature and high voltage, and improves the cycle performance and power performance of a secondary battery at low temperature and high voltage. The application also provides a preparation method of the low-cobalt ternary positive electrode material, a secondary battery, a battery module, a battery pack and a power utilization device containing the material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and more particularly to a single-crystal low-cobalt ternary material. Furthermore, this application also relates to a secondary battery comprising the single-crystal low-cobalt ternary material, a battery pack comprising the secondary battery, a battery module, and an electrical device. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. As the application scope of lithium-ion batteries expands, their acceleration performance at low temperatures and driving range urgently need improvement to meet greater market demand.

[0003] Currently, using ternary materials such as lithium iron phosphate and lithium nickel cobalt manganese oxide as positive electrode active materials in lithium-ion batteries is a relatively effective approach. Compared to lithium iron phosphate, lithium nickel cobalt manganese oxide is the best choice; however, this material is more expensive due to its high cobalt content, and lithium-ion batteries experience reduced cycle performance, power output, and shortened lifespan under low-temperature, high-voltage conditions. Therefore, there is an urgent need for a positive electrode active material that can improve the electrochemical performance of lithium-ion batteries under low-temperature, high-voltage conditions while reducing manufacturing costs. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a low-cobalt ternary cathode active material that enables secondary batteries to have improved power and cycle performance at low temperature and high voltage, as well as lower cost.

[0005] To achieve the above objectives, this application provides a low-cobalt ternary cathode material with a single-crystal structure, characterized in that...

[0006] The chemical formula of the single-crystal low-cobalt ternary cathode material is Li. 1+x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is selected from one or more of Zr, Sr, B, Ti, Mg, Sn and Al, and A is selected from one or more of S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤d ≤ 0.1, 0 ≤ y<0.2; and

[0007] In the single-crystal low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core in a cross-section passing through the geometric center of the particle is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1. The outer layer is the region from the surface of the particle to a depth of 200 nm in the direction towards the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered at the geometric center of the particle. Further, the radius of the material particle is at least 300 nm, optionally from 400 to 4000 nm. Thus, by obtaining a single-crystal low-cobalt ternary material that satisfies the above relationship and has a higher Co content in the outer layer than in the core, this application effectively improves the structural stability and kinetic properties of the cathode material under low temperature and high voltage, thereby improving the cycle performance and power of the secondary battery under low temperature and high voltage.

[0008] In some embodiments, the low-cobalt ternary cathode material particles also have a coating layer, which is a Q-containing oxide, wherein Q is one or more selected from Zr, Sr, B, Ti, Mg, Sn, and Al. This helps to reduce side reactions between the cathode active material surface and the electrolyte, thereby improving the stability and safety performance of the battery.

[0009] In some embodiments, the chemical formula of the low-cobalt ternary cathode material contains 0.5 ≤ a ≤ 0.7. This is beneficial for the low-cobalt ternary cathode material to have a high specific capacity at high voltage and maintain good chemical stability.

[0010] In some embodiments, the median particle size Dv of the low-cobalt ternary cathode material 50 In 1.6 m-3.6 Within the range of m, optionally within 1.8 m-3.5 Within the m range. This can improve the lithium-ion insertion / extraction capability and enhance the electrochemical performance of the battery.

[0011] In some embodiments, the low-cobalt ternary cathode material is characterized in that the Q content is 500-5000 ppm, based on the Q element in the Q-containing oxide relative to the low-cobalt ternary cathode material with a coating layer. This is beneficial for improving the structural stability of the cathode active material and reducing gas generation and heat generation.

[0012] The second aspect of this application provides a method for preparing a low-cobalt ternary cathode material, characterized in that it includes:

[0013] Step S1: The positive electrode active material precursor, lithium salt, and M-containing compound are mixed and sintered, and then crushed to obtain active material particle precursor 1, wherein the chemical formula of the positive electrode active material precursor is (Ni a Co b Mn c (OH)2), where 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1; 0.5≤ a ≤ 0.7

[0014] Step S2: Mix the active material particle precursor 1 with a Co-containing compound and sinter to obtain an active material particle precursor 2 with a Co-rich surface; tempering treatment to obtain a low-cobalt ternary cathode material.

[0015] The low-cobalt ternary cathode material has a single-crystal structure and its chemical formula is Li. 1+x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al, A is one or more selected from S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤ d ≤ 0.1, 0 ≤ y<0.2; and

[0016] In a single particle of the single-crystal low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core, on a cross-section passing through the geometric center of the particle, is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1. The outer layer is the region from the surface of the particle to a depth of 200 nm in the direction towards the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the radius of the material particle is at least 300 nm, optionally from 400 to 4000 nm.

[0017] The method for preparing low-cobalt ternary cathode active materials of the present invention is simple, easy to implement, and low in cost, and can be applied on a large scale in industrial production.

[0018] In some embodiments of the secondary battery, the M-containing compound in step S1 is selected from one or more of magnesium oxide, strontium oxide, titanium oxide, tin oxide, zirconium oxide, aluminum oxide, and boron oxide, and may be zirconium oxide, strontium oxide, or magnesium oxide.

[0019] In step S1, the sintering temperature is in the range of 800℃ to 960℃, the sintering time is 5-15 h, and the sintering atmosphere is air or O2. This is beneficial for the fusion between particles and increases the particle size.

[0020] In some embodiments, step S2 further includes step S2a: coating the Co-rich active material particle precursor 2 with a Q-containing oxide. In some embodiments, the Q-containing oxide in step S2a is selected from one or more of aluminum oxide, tin oxide, zirconium oxide, boron oxide, and titanium oxide, and may be titanium oxide. This yields a monocrystalline low-cobalt cathode active material with a coating layer, which avoids contact with the electrolyte in the secondary battery and stabilizes the structure of the monocrystalline low-cobalt cathode active material.

[0021] In some embodiments, the Co-containing compound in step S2 is selected from one or more of cobalt hydroxide, cobalt hydroxyoxide, cobalt oxide, cobalt acetate, or cobalt oxalate. In some embodiments, the amount of the Co-containing compound added in step S2 is such that the molar amount of Co added is in a ratio of 0.005-0.05:1 to the total molar amount of the metal elements Ni, Co, and Mn in the positive electrode active material precursor obtained in step S1, optionally 0.01-0.03:1.

[0022] In some embodiments, in step S2, the sintering temperature is in the range of 650-750°C, optionally in the range of 700-720°C, the sintering time is 2-8 h, optionally 4-5 h, and the sintering atmosphere is air or O2. This yields a positive electrode active material with a non-uniformly distributed Co element.

[0023] A third aspect of this application provides a secondary battery, including the monocrystalline low-cobalt positive electrode active material of the first aspect of this application or the monocrystalline low-cobalt positive electrode active material prepared according to the method of the second aspect of this application.

[0024] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0025] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0026] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application.

[0027] Because the active cathode material provided by this invention has the characteristics of single-crystal morphology, overall low cobalt content, cobalt-rich outer layer, and small particle size, the secondary battery made using the single-crystal low-cobalt cathode active material of this invention has improved cycle performance and power performance under low temperature and high voltage, and a long driving range. Correspondingly, the battery pack, battery module, and power device provided by this application also have good cycle capability and long driving range under low temperature and high voltage. Attached Figure Description

[0028] Figure 1 The image shows a SEM image of the low-cobalt cathode active material of Example 1 of this application.

[0029] Figure 2 The following is a line scan of the Co element in the low-cobalt cathode active material of this application ( Figure 2 A), and the radial distribution of Co element content (mass fraction) Figure 2 B).

[0030] Figure 3 This diagram illustrates the volume average particle size distribution according to one embodiment of this application.

[0031] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0032] Figure 5 yes Figure 4 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0033] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application.

[0034] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0035] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0036] Figure 9 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the single-crystal low-cobalt ternary material, its preparation method, secondary battery, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0040] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-6. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0043] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0044] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0045] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] Currently, lithium nickel cobalt manganese oxide ternary materials with a secondary spherical structure exhibit better low-temperature performance due to their smaller primary particles; however, at high voltages (≥4.3V), these secondary spherical particles are prone to cracking, leading to a rapid decrease in capacity. In contrast, single-crystal lithium nickel cobalt manganese oxide ternary materials are less prone to cracking and are more suitable for high-voltage applications, but their larger primary particles often result in inferior low-temperature performance compared to ternary secondary spherical materials. Furthermore, commercially available lithium nickel cobalt manganese oxide ternary materials typically have a high cobalt content, which helps reduce the Li / Ni mixing ratio on the surface of the cathode active material, accelerating the lithium-ion insertion / extraction rate and further improving the kinetic performance of single-crystal low-cobalt ternary cathode materials. However, the high price of Co results in excessively high costs.

[0047] To address the aforementioned technical problems, the inventors modified the single-crystal lithium nickel cobalt manganese oxide ternary material to develop a low-cost single-crystal low-cobalt ternary cathode material that can improve the cycle performance and power of batteries under low temperature and high voltage conditions.

[0048] Low-cobalt ternary cathode materials

[0049] The first aspect of this application provides a low-cobalt ternary cathode material with a single-crystal structure, characterized in that...

[0050] The chemical formula of the low-cobalt ternary cathode material is Li. 1+x(Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is selected from one or more of Zr, Sr, B, Ti, Mg, Sn and Al, A is selected from one or more of S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤ d≤ 0.1, 0 ≤ y<0.2;

[0051] and

[0052] In a single particle of the single-crystal low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core, on a cross-section passing through the geometric center of the particle, is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1. The outer layer is the region from the surface of the particle to a depth of 200 nm in the direction towards the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the radius of the material particle is at least 300 nm, optionally from 400 to 4000 nm.

[0053] In this invention, the low-cobalt ternary cathode material has a single-crystal structure. In the field of lithium-ion batteries, single crystal refers to a particle morphology, which is usually a dispersion of single particles (micrometer-sized) with fewer grain boundaries; while secondary spherical particles are usually agglomerated from many particles (100~500 nanometers) to form a spherical shape, with a large number of grain boundaries. The single-crystal ternary cathode material is a powder mainly composed of monodisperse primary particles, which means that these primary particles are separated from each other and independent of each other. More importantly, this single-crystal ternary cathode material is suitable for high voltage (≥4.3V), has the advantages of high energy density and resistance to cracking, which are not possessed by polycrystalline secondary spherical ternary materials.

[0054] In this invention, "unit area" refers to an area of ​​the same size in the outer layer and the core, typically 1 square nanometer, but can be selected according to actual test conditions.

[0055] In this invention, the Co content refers to the percentage of the mass of Co element contained in a unit area of ​​a single particle of the single-crystal low-cobalt ternary material, on a cross-section passing through the geometric center of the single particle, relative to the total mass of the single-crystal low-cobalt ternary material.

[0056] In the chemical formula of the low-cobalt ternary cathode material, the molar fraction of Li to the total molar fraction of Ni, Co and Mn is in the range of (1.67-1):1, and optionally in the range of (1.10-1.01):1. This is because when the sintering temperature is high, it is necessary to increase the excess lithium to compensate; moreover, the molar ratio in this range is conducive to obtaining single crystal materials with higher specific energy.

[0057] The molar fraction of Co is 0.05 ≤ b ≤ 0.14, which is lower than the Co content (at least 0.15%) of commonly used commercially available ternary materials (e.g., NCM333 or NCM523). Therefore, the single-crystal low-cobalt ternary material of the present invention reduces the amount of cobalt used, thereby reducing product costs.

[0058] The mole fractions of Ni, Co, and Mn should satisfy the following relationships: 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 A value ≤0.21 is beneficial for obtaining low-cobalt ternary single-crystal materials with stable crystal structures.

[0059] Optionally, when element M is present in the single-crystal low-cobalt cathode material of the present invention, the molar fraction of element M is not greater than 0.1, and optionally in the range of 0.001 to 0.005. This is beneficial to more effectively stabilize the structure of the cathode active material, improve the transport performance of lithium ions in the cathode active material particles, and thus improve the cycle performance of the battery.

[0060] Optionally, when element A is present in the single-crystal low-cobalt cathode material of the present invention, the molar fraction of element A is not greater than 0.2. By adding element A, which has strong electronegativity, to the cathode active material, the structural stability of the cathode active material is further improved, which is beneficial to improving the cycle performance of the battery.

[0061] Surprisingly, the inventors have discovered that single-crystal low-cobalt ternary materials that satisfy the above-mentioned relationship, if the Co element is not uniformly distributed, especially if the ratio of Co content per unit area in the outer layer to the core is in the range of 1.2-5.0:1, or optionally in the range of 1.4-2.0:1, can obtain structurally stable low-cobalt ternary cathode materials under low temperature and high voltage, thereby improving the cycle performance and power of secondary batteries under low temperature and high voltage.

[0062] In some embodiments, the ratio of Co content per unit area in the outer layer to the core can be selected as 1.4, 1.5, 1.7, 1.9, or 2.0. In some embodiments, the ratio of Co content per unit area in the outer layer to the core is in the range of (1.9-2.0):1.

[0063] In some embodiments, the low-cobalt ternary cathode material particles also have a coating layer, which is a Q-containing oxide, wherein Q is one or more selected from Zr, Sr, B, Ti, Mg, Sn, and Al. Further, the thickness of the coating layer is 3-100 nm, optionally 10-180 nm.

[0064] The single-crystal low-cobalt ternary cathode active material of the present invention can be active material particles, or particles composed of the active material particles and a coating layer coated thereon, wherein the coating layer is a coating layer selected from Q element oxides.

[0065] By coating the surface of active material particles with a coating layer containing an oxide containing the element Q, it is beneficial to reduce the electrolyte oxidation activity on the surface of the positive electrode active material, reduce the side reactions of the electrolyte on the surface of the positive electrode active material, suppress gas generation, reduce heat generation, and thus improve the stability and safety performance of the battery.

[0066] In this invention, the surface refers to the interface between the body (e.g., the active material particles) and the external environment (e.g., air, water, or electrolyte).

[0067] In some embodiments, in the chemical formula of the low-cobalt ternary cathode material, 0.5 ≤ a ≤ 0.7.

[0068] This is beneficial for low-cobalt ternary cathode materials to have a higher specific capacity under high voltage and maintain good chemical stability.

[0069] In some embodiments, the low-cobalt ternary cathode material has a median particle size Dv. 50 Particles in the range of 1.6 μm to 3.6 μm, and optionally in the range of 1.8 μm to 3.5 μm. Further optionally, Dv... 10 Within the range of 0.9μm-1.1μm, for example, 1.0μm; Dv 30 Within the range of 1.4μm-1.6μm, for example, 1.5μm; Dv 60 Within the range of 2.4μm-2.6μm, for example, 2.5μm.

[0070] Therefore, it can improve the lithium-ion intercalation / deintercalation capability, accelerate the lithium-ion intercalation / deintercalation rate, and help improve the electrochemical performance of the battery at low temperatures.

[0071] In some embodiments, the Q content in the coating layer of the low-cobalt ternary cathode material is 500-5000 ppm, based on the Q element in the Q-containing oxide relative to the single-crystal low-cobalt ternary cathode material with the coating layer.

[0072] This not only helps improve the structural stability of the positive electrode active material and reduce gas and heat generation, but also helps the positive electrode active material to have higher rate performance, power performance and capacity performance.

[0073] A second aspect of this application provides a method for preparing a low-cobalt ternary cathode material, characterized in that it includes:

[0074] Step S1: The positive electrode active material precursor, lithium salt, and M-containing compound are mixed and sintered, and then crushed to obtain active material particle precursor 1, wherein the chemical formula of the positive electrode active material precursor is (Ni a Co b Mn c (OH)2), where 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0.5≤ a ≤0.7,

[0075] Step S2: Mix the active material particle precursor 1 with a Co-containing compound and sinter to obtain an active material particle precursor 2 with a Co-rich surface; tempering treatment to obtain a low-cobalt ternary cathode material.

[0076] Among them, the low-cobalt ternary cathode material has a single-crystal structure.

[0077] The chemical formula of the low-cobalt ternary cathode material is Li. 1+x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is selected from one or more of Zr, Sr, B, Ti, Mg, Sn and Al, A is selected from one or more of S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤ d≤ 0.1, 0 ≤ y<0.2; and

[0078] In a single particle of the single-crystal low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core, on a cross-section passing through the geometric center of the particle, is in the range of 1.2-5.0:1, optionally in the range of 1.4-2.0:1. The outer layer is the region from the surface of the particle to a depth of 200 nm in the direction towards the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle. Further, the radius of the material particle is at least 300 nm, optionally from 400 to 4000 nm.

[0079] The positive electrode active material provided in this invention has a simple and easy-to-implement preparation process and low cost, and can be applied on a large scale in industrial production.

[0080] Step S1

[0081] In step S1, the positive electrode active material precursor can be prepared by co-precipitation, gelation, or solid-state methods. As an example, the preparation method of the positive electrode active material precursor includes the following steps:

[0082] S110. Disperse the Ni source, Co source and Mn source in a solvent according to the stoichiometric ratio to obtain a mixed solution.

[0083] S120. Adjust the pH of the mixed solution and react under a preset temperature and stirring. An inert gas can be introduced for protection during the reaction. After the reaction is complete, the precursor of the positive electrode active material is obtained through separation, washing, and drying. Its chemical formula is [Ni a Co b Mn c ](OH)2.

[0084] In step S110, the Ni source is a soluble nickel salt. There are no particular restrictions on the specific type of nickel salt; it can be selected according to actual needs. As an example, the nickel salt is selected from nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, or nickel acetate, and any mixture thereof, optionally selected from nickel sulfate and / or nickel nitrate, and further optionally from nickel sulfate.

[0085] In step S110, the Co source is a soluble cobalt salt. There are no particular restrictions on the specific type of cobalt salt; it can be selected according to actual needs. As an example, the cobalt salt is selected from cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, or cobalt acetate, and any mixture thereof, optionally selected from cobalt sulfate and / or cobalt nitrate, and further optionally from cobalt sulfate.

[0086] In step S110, the Mn source is a soluble manganese salt. There are no particular restrictions on the specific type of manganese salt; it can be selected according to actual needs. As an example, the manganese salt is selected from manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, or manganese acetate, and any mixture thereof, optionally selected from manganese sulfate and / or manganese nitrate, and further optionally from manganese sulfate.

[0087] In step S110, the molar ratio of the added Ni source, Co source, and Mn source is 1:(0.04-0.4):(0.2-0.7), or optionally 1:(0.05-0.3):(0.25-0.65). There are no particular limitations on the solvent, as long as it can dissolve the Ni source, Co source, and Mn source. As an example, the solvent is selected from water, methanol, ethanol, acetone, isopropanol, or n-hexanol, and any mixture thereof. The water can be one or more of deionized water, distilled water, mineral water, and tap water, for example, deionized water.

[0088] In step S110, there is no particular limitation on the concentration of the mixed solution, which can be adjusted according to actual needs. The mixed solution is an aqueous solution containing nickel, cobalt, and manganese ions, generally an aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate. As an example, the concentration of the mixed solution is 1.5 mol / L to 3.5 mol / L, for example, 2.0 mol / L to 2.9 mol / L. The concentration of the Co source in the mixed solution is 0.05 to 1.0 mol / L, optionally 0.06 to 0.6 mol / L.

[0089] In step S120, a reaction system can be formed by adding a precipitant and a complexing agent to the mixed solution. The concentrations of the complexing agent and the precipitant in the reaction system are adjusted, and the pH of the reaction system is controlled to be 10-12 to carry out a co-precipitation reaction to obtain a positive electrode active material precursor, such as [Ni a Co b Mn c ](OH)2.

[0090] In step S120, the precipitant can be one or more of LiOH, NaOH, and KOH, for example, NaOH. Further, the precipitant is in solution form, wherein the solvent can be one or more of water, methanol, ethanol, acetone, isopropanol, and n-hexanol, and the aforementioned water can be one or more of deionized water, distilled water, mineral water, and tap water, for example, deionized water. There is no particular limitation on the concentration of the precipitant solution, which can be selected according to actual needs. Optionally, the concentration of NaOH is 0.5-5 mol / L, for example, 1 mol / L.

[0091] In step S120, the complexing agent can be one or more of ammonia, ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium citrate, and disodium ethylenediaminetetraacetate (EDTA). Further, the complexing agent is in solution form, wherein the solvent can be one or more of water, methanol, ethanol, acetone, isopropanol, and n-hexanol, and the aforementioned water can be one or more of deionized water, distilled water, mineral water, and tap water, for example, deionized water.

[0092] Optionally, the complexing agent is ammonia water. There is no particular limitation on the concentration of ammonia water, and it can be selected according to actual needs. Optionally, the concentration of ammonia water is 0.1 mol / L to 2 mol / L, more specifically 0.2 mol / L to 1.5 mol / L, and even more specifically 0.3 mol / L to 1 mol / L, for example 0.4 mol / L.

[0093] Furthermore, the reaction temperature is 40℃ ~ 70℃, then 45℃ ~ 65℃, and even further, 50℃ ~ 60℃.

[0094] In step S120, the reaction is carried out under an inert gas protective atmosphere and continuous stirring. The inert gas is selected from one or more of nitrogen, argon, and helium. There are no particular restrictions on the stirring method, as long as the reaction system is stirred evenly. For example, mechanical stirring can be selected. The stirring speed is, for example, 100 rpm to 800 rpm. The above "rpm" means revolutions per minute, which represents the number of times the stirring device rotates per minute.

[0095] There are no particular restrictions on the detergent used when washing the coprecipitation reaction products. The detergent can be selected according to actual needs, such as using deionized water. There is no particular limit to the number of washes, as long as the residual ions on the surface of the reaction products can be removed.

[0096] After washing the coprecipitation reaction product, there are no particular restrictions on the drying temperature and method; they can be selected according to actual needs. For example, the drying temperature can be 100℃ ~ 150℃.

[0097] In step S1, the lithium salt is selected from lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), lithium acetate (CH3COOLi), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), or lithium nitrate (LiNO3), and any mixture thereof. Optionally, the lithium salt is selected from lithium carbonate, lithium hydroxide, or lithium nitrate, and any mixture thereof. Further optionally, the lithium salt is lithium carbonate.

[0098] In step S1, the compound containing M can be selected from one or more of oxides containing the element M, nitrate compounds, carbonate compounds, hydroxides, and acetic acid compounds. For example, the compound containing M is an oxide containing the element M, selected from one or more of magnesium oxide, strontium oxide, titanium oxide, tin oxide, zirconium oxide, aluminum oxide, and boron oxide; optionally, selected from one or more of magnesium oxide, strontium oxide, titanium oxide, zirconium oxide, aluminum oxide, and boron oxide; further optionally, selected from one or more of strontium oxide, titanium oxide, zirconium oxide, aluminum oxide, and boron oxide; and even more optionally, selected from one or more of zirconium oxide, strontium oxide, and boron oxide.

[0099] Optionally, when preparing active material particles without or containing doped element M, the amount of positive electrode active material precursor and lithium salt added is such that the ratio of the total molar amount of metal elements (Ni, Co, Mn) in the positive electrode active material precursor to the molar amount of Li element in the lithium salt is Me:Li = 1:(0.99~1.2), optionally, Me:Li = 1:(1~1.2), and further optionally, Me:Li = 1:(1.02~1.10), where Me is the sum of the molar amounts of metal elements in the positive electrode active material precursor, i.e., Me = Ni+Co+Mn.

[0100] Optionally, when preparing active material particles containing doped element M, the amount of positive electrode active material precursor and M-containing compound added is such that the ratio of the total molar amount of metal elements (Ni, Co, Mn) in the positive electrode active material precursor to the molar amount of M element in the M-containing compound is Me:M = 1:(0.001-0.005), or alternatively, Me:M = 1:(0.0015-0.003), where Me is the sum of the molar amounts of metal elements in the positive electrode active material precursor, i.e., Me = Ni+Co+Mn.

[0101] In step S1, mixing the positive electrode active material precursor and lithium salt and sintering them yields active material particles free of dopant element M. Alternatively, mixing the positive electrode active material precursor and lithium salt with a compound containing M and sintering them yields active material particles modified with M at the transition metal sites. Alternatively, mixing the positive electrode active material precursor and lithium salt with a compound containing M and a compound containing A and sintering them yields active material particles modified with M at the transition metal sites and doped with A at the oxygen sites.

[0102] The compound containing A can be selected according to actual needs, for example, it can be selected from one or more of the following: ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium bromide, lithium bromide, hydrogen bromide, ammonium iodide, lithium iodide, hydrogen iodide, hydrogen sulfide, lithium sulfide and ammonium sulfide.

[0103] Furthermore, in step S1, sintering is carried out in oxygen or air; the sintering temperature is in the range of 800℃ to 960℃. There is no particular limitation on the sintering time, which can be adjusted according to the actual situation, for example, 5 h to 15 h. This relatively high sintering temperature is beneficial to the fusion between particles and increases the particle size.

[0104] In step S1, there are no particular restrictions on the crushing method; it can be selected according to actual needs, such as using an air jet mill or a mechanical mill. Optionally, an air jet mill, such as the Shenyang Aircraft Corporation's air jet mill (40m³), can be used. 3 The crushing air pressure is set to 0.2-0.35 MPa, the feeding speed is 280-320 Kg / h, and the feeding particle size is controlled within 2 mm. The crushing operation is conducive to further decomposing the particles, thereby controlling the particle size within the desired range.

[0105] The median particle size of the active material precursor 1 obtained through sintering and crushing in step S1 is 1.4 mm. m-3.4 m, optionally in 1.6 m -3.5 m.

[0106] Step S2

[0107] In some embodiments, step S2 further includes step S2a: coating the Co-rich active material particle precursor 2 with a Q-containing oxide.

[0108] The positive electrode active material obtained by the method including step S2a includes active material particles and a coating layer containing element M covering the surface of the active material particles. This coating layer prevents the active material particles from contacting the electrolyte in the secondary battery, thus ensuring the structural stability of the positive electrode active material.

[0109] In some embodiments, the oxide containing Q in step S2a is one or more selected from aluminum oxide, tin oxide, zirconium oxide, boron oxide and titanium oxide, and may be titanium oxide.

[0110] The coating process can be carried out using methods and equipment known in the art, such as dry coating, liquid phase coating, and vapor phase deposition coating.

[0111] This results in a monocrystalline low-cobalt cathode active material with a capping layer, which can avoid contact with the electrolyte in secondary batteries and stabilize the structure of the monocrystalline low-cobalt cathode active material.

[0112] In some embodiments, the Co-containing compound in step S2 is one or more selected from cobalt hydroxide, cobalt hydroxyoxide, cobalt oxide, cobalt acetate, or cobalt oxalate.

[0113] In some embodiments, in step S2, the amount of the Co-containing compound added is such that the ratio of the molar amount of Co added to the total molar amount of metal elements Ni, Co, and Mn in the positive electrode active material precursor obtained in step S1 is 0.005-0.05:1, optionally 0.01-0.03:1.

[0114] In some embodiments, in step S2, the sintering temperature is in the range of 650-750°C, optionally in the range of 700-720°C, the sintering time is 2-8 h, optionally 4-5 h, and the sintering atmosphere is air or O2.

[0115] This facilitates the diffusion of Co elements from the surface into the particles, thereby achieving a non-uniform distribution of Co elements in a single particle of the low-cobalt ternary cathode material, particularly with the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core in the range of 1.2-5.0:1, and optionally in the range of 1.4-2.0:1.

[0116] Further, in step S2, the tempering temperature is 400℃ ~ 700℃, optionally 450℃ ~ 600℃.

[0117] Secondary batteries

[0118] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0119] In one embodiment of this application, a secondary battery is provided, comprising a positive electrode sheet using the single-crystal low-cobalt positive electrode active material of this application.

[0120] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0121] [Positive electrode plate]

[0122] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0123] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0124] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0126] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0128] [Negative electrode plate]

[0129] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0130] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0131] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0133] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0134] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0136] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0137] [Electrolytes]

[0138] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0139] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0140] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0141] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0142] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0143] [Isolation membrane]

[0144] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0145] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0146] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0147] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0148] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0149] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured secondary battery 5.

[0150] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0151] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0152] Figure 6 This is battery module 4, used as an example. (See reference...) Figure 6 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0153] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0154] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0155] Figure 7 and Figure 8 This is battery pack 1 as an example. (See reference...) Figure 7 and Figure 8The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0156] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0157] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0158] Figure 9 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0159] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0160] Example

[0161] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0162] I. Preparation Examples

[0163] [Preparation of positive electrode active materials]

[0164] Example 1

[0165] 1) Preparation of precursors for positive electrode active materials

[0166] Nickel sulfate, manganese sulfate, and cobalt sulfate were added to deionized water to prepare a mixed solution, wherein the molar ratio of nickel, cobalt, and manganese was Ni:Co:Mn = 55.6:11:33.4. 0.4 mol / L ammonia and 1 mol / L sodium hydroxide aqueous solution were added to the mixed solution to adjust the pH of the reaction system to 11.3. The reaction was carried out at 40℃ and 600 rpm with stirring. Inert nitrogen gas was purged during the reaction for protection. After the reaction was complete, the solid product was washed with deionized water and then dried at 100℃ to obtain the positive electrode active material precursor Ni. 0.556 Co 0.11 Mn 0.334 (OH)2.

[0167] 2) Preparation of active substance particle precursor 1

[0168] Lithium carbonate (Li2CO3) and Ni, the precursor of the positive electrode active material, are used. 0.556 Co 0.11 Mn 0.334 (OH)₂ and zirconium oxide (ZrO₂) are mixed and then mechanically blended. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the cathode active material precursor, the amount of lithium carbonate added is such that the molar ratio of lithium to Me is Li:Me = 1.06:1; the amount of zirconium oxide added is such that the molar ratio of zirconium to Me is Zr:Me = 2.031 × 10⁻⁶. -3 :1.

[0169] The mixture was placed in a tube furnace and sintered for 13 hours at a programmed temperature increase of 5°C / min to 940°C under air atmosphere. Afterwards, it was cooled to room temperature with the furnace and then sintered in an air jet mill (Shenyang Aircraft Corporation (40m)). 3 The 2 mm particles were crushed at a crushing air pressure of 0.35 MPa and a feeding speed of 300 Kg / h to obtain active substance particle precursor 1.

[0170] 3) Preparation of active substance particle precursor 2

[0171] Cobalt hydroxide was added to precursor 1 of the above-obtained active material particles. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) of the positive electrode active material precursor, the amount of cobalt hydroxide added was such that the molar ratio of cobalt to Me was 1.14 × 10⁻⁶. -2 1. After thorough mixing, the mixture is sintered at 700°C for 5 hours in air at a programmed temperature of 5°C / min, and then cooled to room temperature in the furnace to obtain the active material particle precursor 2.

[0172] 4) Preparation of active substance particle precursors with coating layer

[0173] Titanium oxide (TiO2) was added to the precursor 2 of the active material particles. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the cathode active material precursor, the amount of titanium oxide added was such that the molar ratio of titanium to Me was 2.031 × 10⁻⁶. -3 :1. After thorough mixing, active material particle precursor 2 with titanium oxide coating is obtained.

[0174] 5) Preparation of low-cobalt cathode active materials

[0175] The obtained active material particle precursor with titanium oxide coating was tempered at 500℃ for 5 hours to obtain the positive electrode active material CA1, wherein the molecular formula of the active material particles is Li. 1.03 (Ni 0.55 Co 0.12 Mn 0.33 ) 0.996 Zr 0.002 Ti 0.002 O2.

[0176] Example 2

[0177] Similar to Example 1, except that step 4 is not included in this preparation process.

[0178] Example 3

[0179] Similar to Example 1, the difference is that in step 2), the mixture is placed in a tube furnace and sintered for 13 h at a programmed temperature increase of 5°C / min to 960°C under an air atmosphere.

[0180] Example 4

[0181] Similar to Example 1, except for the following preparation process:

[0182] 1) Preparation of precursors for positive electrode active materials

[0183] The molar ratio of nickel, cobalt, and manganese is Ni:Co:Mn = 60.7:9:30.4, and the precursor for the positive electrode active material is Ni. 0.607 Co 0.09 Mn 0.304 (OH)2;

[0184] 2) Preparation of active substance particle precursor 1

[0185] Lithium carbonate (Li2CO3) and Ni, the precursor of the positive electrode active material, are used. 0.607 Co0.09 Mn 0.304 (OH)₂ and strontium oxide (SrO) are mixed, followed by mechanical mixing. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the cathode active material precursor, the amount of strontium oxide added is such that the molar ratio of strontium to Me is Sr:Me = 1.011 × 10⁻⁶. -3 :1,; The sintering temperature was 930℃ and the time was 12 h;

[0186] 3) Preparation of active substance particle precursor 2

[0187] The above-obtained active material particle precursor 1 was mixed with cobalt hydroxide and sintered at 710°C for 5 hours.

[0188] The unmentioned reaction conditions and steps were the same as in Example 1, and the molecular formula of the active material particles obtained was Li. 1.03( Ni 0.6 Co 0.1 Mn 0.3 ) 0.997 Sr 0.001 Ti 0.002 O2.

[0189] Example 5

[0190] Similar to Example 1, except for the following preparation process:

[0191] 1) Preparation of precursors for positive electrode active materials

[0192] The molar ratio of nickel, cobalt, and manganese is Ni:Co:Mn = 67.6:8:25.6, and the precursor for the positive electrode active material is Ni. 0.676 Co 0.08 Mn 0.256 (OH)2; Adjust the pH of the reaction system to 11.7;

[0193] 2) Preparation of active substance particle precursor 1

[0194] Lithium carbonate (Li2CO3) and Ni, the precursor of the positive electrode active material, are used. 0.607 Co 0.09 Mn 0.304 (OH)₂ and magnesium oxide (MgO) are mixed, and then mechanically mixed. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the positive electrode active material precursor, the amount of magnesium oxide added is such that the molar ratio of magnesium to Me is Mg:Me = 2.06 × 10⁻⁶. -3:1,; The sintering temperature was 920℃ and the time was 12 h;

[0195] 3) Preparation of active substance particle precursor 2

[0196] Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the precursor of the positive electrode active material, the amount of cobalt hydroxide added is such that the molar ratio of cobalt to Me is 2.36 × 10⁻⁶. -2 Mix in an amount of 1, and sinter at 720℃ for 5 hours;

[0197] 4) Preparation of active substance particle precursors with coating layer

[0198] Titanium oxide (TiO2) coating was used. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the cathode active material precursor, the amount of titanium oxide added was such that the molar ratio of titanium to Me was 2.06 × 10⁻⁶. -3 :1;

[0199] The unmentioned reaction conditions and steps were the same as in Example 1, and the molecular formula of the active material particles obtained was Li. 1.03 (Ni 0.65 Co 0.1 Mn 0.25 ) 0.996 Mg 0.002 Ti 0.002 O2.

[0200] Example 6

[0201] Similar to Example 1, except for the following preparation process:

[0202] 1) Preparation of precursors for positive electrode active materials

[0203] The molar ratio of nickel, cobalt, and manganese is Ni:Co:Mn = 70.8:9:20.2, and the precursor for the positive electrode active material is Ni. 0.708 Co 0.09 Mn 0.202 (OH)2;

[0204] 2) Preparation of active substance particle precursor 1

[0205] Lithium carbonate (Li2CO3) and Ni, the precursor of the positive electrode active material, are used. 0.708 Co 0.09 Mn 0.202(OH)₂ and magnesium oxide (MgO) are mixed, and then mechanically mixed. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the positive electrode active material precursor, the amount of magnesium oxide added is such that the molar ratio of magnesium to Me is Mg:Me = 2.031 × 10⁻⁶. -3 :1; The sintering temperature was 920℃ and the time was 11 h;

[0206] The unmentioned reaction conditions and steps were the same as in Example 1, and the molecular formula of the active material particles obtained was Li. 1.03 (Ni 0.70 Co 0.10 Mn 0.2 ) 0.996 Mg 0.002 Ti 0.002 O2.

[0207] Example 7

[0208] Similar to Example 1, except for the following preparation process:

[0209] 1) Preparation of precursors for positive electrode active materials

[0210] The molar ratio of nickel, cobalt, and manganese is Ni:Co:Mn = 70.7:4:25.3. The precursor for the positive electrode active material is Ni. 0.707 Co 0.04 Mn 0.253 (OH)2; Adjust the pH of the reaction system to 11.8;

[0211] 2) Preparation of active substance particle precursor 1

[0212] The sintering temperature was 910℃ and the time was 14 h;

[0213] 3) Preparation of active substance particle precursor 2

[0214] The obtained active material particle precursor 1 was mixed with cobalt hydroxide. Based on the total molar amount of metal elements (nickel, cobalt, and manganese, i.e., Me = Ni + Co + Mn) in the positive electrode active material precursor, the amount of cobalt hydroxide added was such that the molar ratio of cobalt to Me was 1.05 × 10⁻⁶. -2 1. The sintering temperature is 700℃ and the time is 4 hours;

[0215] The unmentioned reaction conditions and steps were the same as in Example 1, and the molecular formula of the active material particles obtained was Li. 1.03 (Ni 0.7 Co 0.05 Mn0.25 ) 0.996 Zr 0.002 Ti 0.002 O2.

[0216] Comparative Example C1

[0217] Similar to Example 1, except that:

[0218] 1) Preparation of precursors for positive electrode active materials

[0219] The molar ratio of nickel, manganese, and cobalt is Ni:Co:Mn = 55:12:33, and the precursor for the positive electrode active material is Ni. 0.55 Co 0.12 Mn 0.33 (OH)2; wherein the pH of the reaction system is adjusted to 11.2;

[0220] 2) Preparation of active substance particle precursor 1

[0221] Lithium carbonate (Li2CO3) and Ni, a precursor for positive electrode active materials 0.55 Co 0.12 Mn 0.33 (OH)2 is mixed and then mechanically mixed; based on the total molar amount of metal elements (nickel, cobalt and manganese, i.e. Me = Ni + Co + Mn) of the positive electrode active material precursor, the amount of lithium carbonate added is such that the molar ratio of lithium to Me is Li:Me = 1.02:1.

[0222] The mixture was placed in a tube furnace and sintered at 960°C in air at a programmed temperature of 5°C / min for 13 h; then cooled to room temperature with the furnace and crushed.

[0223] Step 2) does not include a compound containing element M and does not include step 3.

[0224] The unmentioned reaction conditions and steps are the same as in Example 1, and the molecular formula of the active material particles obtained is Li(Ni) 0.55 Co 0.12 Mn 0.33 ) 0.998 Ti 0.002 O2.

[0225] Comparative Example C2

[0226] Similar to Example 1, the difference lies in the step...

[0227] 2) The sintering treatment in step 2) is performed at a temperature of 950℃ for 13 hours, excluding step 3).

[0228] The unmentioned reaction conditions and steps were the same as in Example 1, and the molecular formula of the active material particles obtained was Li. 1.03 (Ni 0.55 Co 0.10 Mn 0.33 ) 0.996 Zr 0.002 Ti 0.002 O2.

[0229] Comparative Example C3

[0230] Similar to Example 1, except that:

[0231] 1) Preparation of precursors for positive electrode active materials

[0232] The molar ratio of nickel, manganese, and cobalt is Ni:Co:Mn = 55:15:30, and the precursor for the positive electrode active material is Ni. 0.55 Co 0.15 Mn 0.30 (OH)2; wherein the pH of the reaction system is adjusted to 11.2;

[0233] 2) Preparation of active substance particle precursor 1

[0234] Lithium carbonate (Li2CO3) and Ni, a precursor for positive electrode active materials 0.55 Co 0.12 Mn 0.33 (OH)2 is mixed and then mechanically mixed; based on the total molar amount of metal elements (nickel, cobalt and manganese, i.e. Me = Ni + Co + Mn) of the positive electrode active material precursor, the amount of lithium carbonate added is such that the molar ratio of lithium to Me is Li:Me = 1.02:1.

[0235] The mixture was placed in a tube furnace and sintered at 960°C in air at a programmed temperature of 5°C / min for 13 h; then cooled to room temperature with the furnace and crushed.

[0236] Step 2) does not include a compound containing element M and does not include step 3.

[0237] The unmentioned reaction conditions and steps are the same as in Example 1, and the molecular formula of the active material particles obtained is Li(Ni) 0.55 Co 0.15 Mn 0.30 ) 0.998 Ti 0.002 O2.

[0238] The main preparation parameters of the positive electrode active materials of the above embodiments and comparative examples are shown in Table 1. The product parameters of the positive electrode active materials of the above embodiments and comparative examples are shown in Table 2.

[0239] II. Application Examples

[0240] [Preparation of Secondary Batteries]

[0241] 1. Preparation of positive electrode sheet: The positive active material, conductive carbon black SP and binder polyvinylidene fluoride (PVDF) prepared in each example and comparative example are dispersed in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 18:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0242] 2. Negative electrode sheet: a lithium metal sheet with a diameter of 18 mm and a thickness of 0.5 mm (Tianjin Zhongneng).

[0243] 3. Preparation of electrolyte: Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed evenly at a mass ratio of 30:30:40 to obtain an organic solvent. LiPF6 was dissolved in the above solvent and mixed evenly to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0244] 4. Preparation of button cell: The positive electrode, polypropylene / polyethylene / polypropylene (PP / PE / PP) composite separator and negative electrode are stacked in sequence, and the above electrolyte is added to complete the preparation of the button cell.

[0245] The performance of the secondary battery was tested, and the test results are summarized in Table 2.

[0246] III. Measurement Methods

[0247] [Testing of Low-Cobalt Cathode Active Materials]

[0248] 1. Scanning electron microscope images of low-cobalt cathode active materials

[0249] A field emission scanning electron microscope (Zeiss Sigma 300) was used, with the following settings: resolution of 20 nm, accelerating voltage of 0.1-30 kV, magnification of 30-50,000 times, and In-lens mode. Detailed testing procedures were performed according to reference standard JY / T010-1996.

[0250] Scanning electron microscopy (SEM) of the positive electrode active material in Example 1 is as follows: Figure 1 As shown.

[0251] 2. Determination of elemental content in low-cobalt cathode active materials

[0252] Determination of metal and sulfur content: Inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400) was used for determination. First, 0.4 g of low-cobalt positive electrode active material was weighed and 10 ml (50% concentration) of aqua regia was added. The mixture was then placed on a plate at 180℃ for 30 min. After digestion on the plate, the volume was adjusted to 100 mL. Quantification method: standard curve method, referring to EPA 6010D-2014.

[0253] Determination of the content of elements N, F, Cl, Br and I: Ion chromatography (IC) was used, with reference to EN 14582:2016.

[0254] The oxygen content is calculated by the difference between the total amount of low-cobalt cathode active material (i.e., 1) and the sum of the contents of the above-mentioned detectable elements.

[0255] 3. Determination of Co content in the core and outer layer of low-cobalt active materials

[0256] An argon ion cross-section polisher (model JEOL IB-19530CP) and a scanning electron microscope (model Zeiss Sigma 300) were used (equipped with an energy dispersive X-ray spectrometer (EDS, model Oxford OXFord X-Max-50mm). 2 The determination was carried out. A slurry was prepared by mixing low-cobalt active material with PVDF and NMP at a weight ratio of 5:2:23, and uniformly coated onto copper foil, then dried at 60°C. After ion polishing, a scanning electron microscope was used to perform a line scan of the Co element content on the cross-section of the single crystal particles. The curve reflected the change in Co element content, such as... Figure 2 As shown.

[0257] 4. Particle size distribution determination

[0258] Instrument used: Malvern, Master Size 3000. Measurement conditions: Particle refractive index: 1.69, particle absorptivity: 1, solvent refractive index: 1.330; Test cycles: 3 times, sample and background test time: 6 s, number of sample and background tests: 6,000, stirrer / pump speed: 3000 rpm, light blocking setting: 8~12%.

[0259] Sample preparation: Add an appropriate amount of low-cobalt cathode material to water, with a total volume of about 110 ml, and sonicate at 53 kHz and 120 W for 5 min.

[0260] The detailed testing process was conducted in accordance with the reference standard: GB / T19077-2016 / ISO13320:2009.

[0261] Particle size distribution diagrams were plotted based on the test data (see attached). Figure 3 This is a particle size distribution diagram of the low-cobalt material in Example 1. From this distribution diagram, we can see that 50% of the particles in the total volume have a diameter greater than a certain Dv50 value, and another 50% of the particles in the total volume have a diameter smaller than this Dv50 value. Therefore, this Dv50 value is the volume average particle size.

[0262] [Battery Performance Test]

[0263] 1. Determination of the capacity performance of positive electrode active materials

[0264] At 25°C, the coin cell is charged at a constant current rate of 0.1C to 4.35V, then charged at a constant voltage rate until the current is less than or equal to 0.05C. After resting for 5 minutes, it is discharged at a constant current rate of 0.1C to 2.8V. The discharge capacity at this point is the specific capacity at room temperature. The coin cell is then placed at a low temperature of -10°C, and the low-temperature specific capacity is obtained by performing the above test. The percentage of the low-temperature specific capacity to the room-temperature specific capacity is the capacity retention rate.

[0265] 2. Measurement of DC resistance (DCR) of secondary batteries

[0266] At a low temperature of -10℃, the coin cell battery is charged at a constant current rate of 0.1C to 4.35V, and then charged at a constant voltage rate until the current is less than or equal to 0.05C. After that, the coin cell battery is adjusted to 20% of its state of charge (SOC), and then discharged at 5C for 10s. The voltage drop before and after discharge is recorded. The ratio of the voltage drop before and after discharge to the discharge current is the DC resistance DCR of the battery.

[0267] Table 1: Process parameters for steps 2)-4) in the preparation of low-cobalt cathode active materials

[0268]

[0269] Table 2: Test Results of Examples and Comparative Examples

[0270]

[0271] Compared with Comparative Examples 1-3, Examples 1-7 of the present invention show that the single-crystal low-cobalt ternary material of the present invention has a smaller median particle size and a non-uniformly distributed Co element; thereby obtaining a secondary battery with lower current impedance and higher capacity retention at low temperature and high voltage. It is evident that the secondary battery including the single-crystal low-cobalt ternary material of the present invention has improved power and cycle performance at low temperature and high voltage.

[0272] The positive electrode active materials prepared in Comparative Examples 1-3 have a uniform distribution of Co. Even for materials with relatively high cobalt content, such as Comparative Example 3, the secondary batteries made from them have poor power and cycle performance at low temperature and high voltage.

[0273] In Examples 1-7 of this invention, the cobalt content in the positive electrode active material is relatively low, thereby reducing costs; simultaneously, the molar fractions of each element in the chemical formula satisfy a certain proportional relationship and are within a certain range, ensuring that the positive electrode active material also possesses high structural stability; the particle size of this positive electrode active material is 1.8 mm. m -3.5 Within the m range, the migration path of lithium ions in the positive electrode active material is shorter. Moreover, the Co content per unit area of ​​the outer layer of a single particle of this positive electrode active material is higher than that in the core, resulting in less Li / Ni mixing in the surface structure. This leads to a faster rate of lithium ion insertion / extraction and better kinetic performance at low temperatures.

[0274] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A low-cobalt ternary cathode material with a single-crystal structure, characterized in that, The chemical formula of the low-cobalt ternary cathode material is Li. 1+x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al, A is one or more selected from S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤ d ≤ 0.1, 0 ≤ y ≤ 0.2; and In a single particle of the low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core on a cross-section passing through the geometric center of the particle is in the range of 1.2-5.0:1, wherein the Co content is the Co mass content, the outer layer is the region from the surface of the particle to a depth of 200 nm in the direction toward the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle.

2. The low-cobalt ternary cathode material according to claim 1, characterized in that, In a single particle of the low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core in a cross-section passing through the geometric center of the particle is in the range of 1.4-2.0:

1.

3. The low-cobalt ternary cathode material according to claim 1, characterized in that, In the individual particles of the low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core in a cross-section passing through the geometric center of the particle is in the range of 1.9-2.0:

1.

4. The low-cobalt ternary cathode material according to claim 1, characterized in that, The low-cobalt ternary cathode material particles also have a coating layer.

5. The low-cobalt ternary cathode material according to claim 4, characterized in that, The coating layer is an oxide containing Q, wherein Q is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al.

6. The low-cobalt ternary cathode material according to claim 1 or 2, characterized in that, In the chemical formula, 0.5 ≤ a ≤ 0.

7.

7. The low-cobalt ternary cathode material according to claim 1, characterized in that, The low-cobalt ternary cathode material has a median particle size Dv. 50 Particles in the range of 1.6μm to 3.6μm.

8. The low-cobalt ternary cathode material according to claim 7, characterized in that, The low-cobalt ternary cathode material has a median particle size Dv. 50 Particles in the range of 1.8μm to 3.5μm.

9. The low-cobalt ternary cathode material according to claim 1, characterized in that, The low-cobalt ternary cathode material is Dv 60 Particles in the range of 2.4μm to 2.6μm.

10. The low-cobalt ternary cathode material according to claim 1, wherein the low-cobalt ternary cathode material is Dv 10 Particles in the range of 0.9μm-1.1μm.

11. The low-cobalt ternary cathode material according to claim 1, characterized in that, The low-cobalt ternary cathode material is Dv 30 Particles in the range of 1.4μm to 1.6μm.

12. The low-cobalt ternary cathode material according to claim 5, characterized in that, The Q content is 500-5000 ppm, based on the Q element in the Q-containing oxide relative to the low-cobalt ternary cathode material with a coating layer.

13. The low-cobalt ternary cathode material according to claim 1, characterized in that, The particle radius of the low-cobalt ternary cathode material is 400 to 4000 nm.

14. A method for preparing low-cobalt ternary cathode materials, characterized in that, include: Step S1: The positive electrode active material precursor, lithium salt, and M-containing compound are mixed and sintered, and then crushed to obtain active material particle precursor 1, wherein the chemical formula of the positive electrode active material precursor is (Ni a Co b Mn c (OH)2), where 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1; 0.5≤ a ≤ 0.7 Step S2: Mix the active material particle precursor 1 with a Co-containing compound and sinter to obtain an active material particle precursor 2 with a Co-rich surface; tempering treatment to obtain a low-cobalt ternary cathode material. The low-cobalt ternary cathode material has a single-crystal structure and its chemical formula is Li. 1+x (Ni a Co b Mn c ) 1-d M d O 2-y A y Where M is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al, A is one or more selected from S, N, F, Cl, Br and I, 0 ≤ x ≤ 0.5, 0.05 ≤ b ≤ 0.14, 3.5 ≤ a / b ≤ 15, 0.02 ≤ b×c / a 2 ≤ 0.21, a+b+c = 1, 0 ≤ d ≤ 0.1, 0 ≤ y ≤ 0.2; and In a single particle of the low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core on a cross-section passing through the geometric center of the particle is in the range of 1.2-5.0:1, wherein the Co content is the Co mass content, the outer layer is the region from the surface of the particle to a depth of 200 nm in the direction toward the geometric center of the particle, and the core is a spherical region with a diameter of 200 nm centered on the geometric center of the particle.

15. The method according to claim 14, characterized in that, In the individual particles of the low-cobalt ternary cathode material, the ratio between the average Co content per unit area of ​​the outer layer and the average Co content per unit area of ​​the core in a cross-section passing through the geometric center of the particle is in the range of 1.4-2.0:

1.

16. The method according to claim 14, characterized in that, The M-containing compound mentioned in step S1 is selected from one or more of magnesium oxide, strontium oxide, titanium oxide, tin oxide, zirconium oxide, aluminum oxide, and boron oxide.

17. The method according to claim 16, characterized in that, The M-containing compound mentioned in step S1 is one or more selected from zirconium oxide, strontium oxide, or magnesium oxide.

18. The method according to claim 14, characterized in that, In step S2, there is also step S2a: coating the active material particle precursor 2 with a surface rich in Co with an oxide containing Q, wherein Q is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al.

19. The method according to claim 18, characterized in that, In step S2a, the oxide containing Q is selected from one or more of aluminum oxide, tin oxide, zirconium oxide, boron oxide, and titanium oxide.

20. The method according to claim 19, characterized in that, The oxide containing Q in step S2a is titanium oxide.

21. The method according to claim 14, characterized in that, The Co-containing compound mentioned in step S2 is selected from one or more of cobalt hydroxide, cobalt hydroxyoxide, cobalt oxide, cobalt acetate, or cobalt oxalate.

22. The method according to claim 14, characterized in that, In step S2, the amount of the Co-containing compound added is such that the ratio of the molar amount of Co element added to the total molar amount of metal elements Ni, Co, and Mn in the positive electrode active material precursor obtained in step S1 is 0.005-0.05:

1.

23. The method according to claim 22, characterized in that, In step S2, the amount of the Co-containing compound added is such that the ratio of the molar amount of Co element added to the total molar amount of metal elements Ni, Co, and Mn in the positive electrode active material precursor obtained in step S1 is 0.01-0.03:

1.

24. The method according to claim 14, characterized in that, In step S2, the sintering temperature is in the range of 650-750℃, and the sintering time is 2-8 h.

25. The method according to claim 24, characterized in that, The sintering temperature in step S2 is in the range of 700-720℃.

26. The method according to claim 24, characterized in that, The sintering time is 4-5 hours.

27. A secondary battery, characterized in that, The low-cobalt ternary cathode material includes any one of claims 1 to 13 or any one of claims 14 to 26.

28. A battery module, characterized in that, Includes the secondary battery as described in claim 27.

29. A battery pack, characterized in that, Includes the battery module as described in claim 28.

30. An electrical device, characterized in that, It includes at least one selected from the secondary battery of claim 27, the battery module of claim 28, or the battery pack of claim 29.

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